As fiber reinforced plastic composites gain an increasingly larger share in aerospace structures, the problem of joining them with metal elements becomes significant. The current paper is the second part of the literature review, which gathers and evaluates knowledge about methods suitable for the mechanical joining of composite and metal elements. This paper reviews the joining methods other than bolted joining, which are discussed in the first part of the review, namely self-piercing riveting, friction riveting, clinching, non-adhesive form-locked joints, pin joints, and loop joints. Some of those methods are full-fledged and employed in commercial applications, whereas others are merely ideas tested at the level of specimens. The current review describes the ideas and the qualities of the joining methods as well as the experimental work carried out so far. The summary section of this paper contains a comparison of those methods with the reference to their qualities, which is important from the point of view of a composite structure designer: possibility of the joint disassembly, damages induced in composite, complication level, weight penalty, range of possible materials to be joined, and the joint strength. Fibre reinforced composite materials continue to gain progressively larger share in the structures of modern aircraft. The amounts of composite laminates used in the Boeing 787 Dreamliner and Airbus A350 exceed 50% of the vehicle weight ,2. SinceThe number, diversity, and complexity of mechanical methods of joining composite and metal materials makes the choice of the proper method tedious and difficult. Furthermore, the recent review work on joining FRP composites to metal is moderate. Amancio-Filho and dos Santos described trends in joining of polymers and polymer-metal hybrid structures including bolted joining, clinching, welding and friction riveting . Kah et Conventional riveting does not apply to composite materials because loads experienced during the riveting process destroy the composite matrix around the rivet , therefoThe process of self-piercing riveting consists in joining two stacked sheets of the same or dissimilar materials by a rivet which is forced into the stack by a punch. The rivet pierces the top material through and partially pierces into the bottom material. The die on the bottom side of the stacked sheets causes the rivet to flare under the force, creating a mechanical interlock ,15. BothThe process does not require pre-drilled holes, and thus it is carried out in one operation ,15,19, wNo surface pre-treatment is needed ,21.The process is operator-friendly, and it emits only low noise, no fumes , and is This process has gained wide diffusion in the automotive industry, due to the increasing use of materials alternative to steel that are difficult or impossible to join using traditional techniques ,18. ReceOne disadvantage of the process is the fact that both sides of the joint must be accessible , which lUeda et al. found, on the basis of the cross-sections of SPR joined composite materials, that dragging of composite plies due to the punching appears around the hole  21]. De. De21]. 6 cycles is higher by 22% for the domed headed rivets than for the countersunk rivets ,,54,46,54Galvanic corrosion may occur in this joining method if a substrate made of aluminium alloys or steel is used along with a CFRP composite ,23.However, it has also disadvantages:The punch diameter has a significant influence on the joint quality: the neck-thickness is decreased and the undercut is increased with the increase of the punch diameter.The neck formation is also severely influenced by the punch corner radius. Sharp punch corners induce the concentration of deformation at the neck of the upper sheet, which decreases the neck-thickness, so the punches with tight radii are suitable for punching materials which have sufficient ductility, such as SPRC440. Blunt punch corners are suitable for more fragile materials, such as Al6061, and reduce the damage at the neck, but on the other hand, expand the hole in the lower sheet.The die depth also influences the quality of the joints. When the die is too shallow the undercut creation process is disturbed. On the other hand, too deep a die may cause the fracture of the joint neck in the joining process.Lee et al. conducted single lap shear tests of AA6061 alloy and the CFRP sheets joined by clinching . The speThe best failure strength of single lap shear (SLS) specimens (2.69 kN) was achieved for hole clinching process of CFRP laminates and Al6061 with flat die and with sharp punch corner . The joiThe clinching process was performed without pre-cutting holes in the composite sheet. Single lap shear tests of the specimens were carried out. In the case of the grooved and split dies part of the composite was stuck in the grooves and the splits proving very difficult to be removed, which makes those dies unsuitable for the commercial manufacturing process . On the An investigation which analyses two-stepped clinching based on reshaping deformation that follows mechanical clinching, as a method to improve the mechanical behaviour of clinched connections performed on hybrid metal-composites joints was presented by Lambiase and Ko . The cliApart from the conventional clinching process in which the metal component is plasticized in order to create lock in the hole made in the composite component, there have been several attempts made in order to design different processes, which can be incorporated to the group of ‘mechanical clinching’ methods. In those processes the composite component is the one which is softened to create a lock in the hole of the metal component. Only thermoplastic matrix composites are suitable to be joined by those processes, because the thermoset matrix, once cured, cannot be plasticized again and would crack under high strains required in clinching. Gude et al. developed a method called thermoclinching in order to join steel sheets with glass fabric reinforced polypropylene . The comThe joints were tested in single lap shear experiments and failed by either pull out (3kN) or shear (2 kN) of the composite formed lock, depending on its geometrical features . Abibe eJoints of short glass fibre-reinforced polyamide 6,6 and aluminium alloy were produced using the injection clinching joining process ,57. The It was found that the vertical force on the tool, as well as the tool diameter, rotation, and feed rate, must be carefully selected in order to generate correct heat which does not melt the composite but, at the same time softens it enabling the backward extrusion . DVS-EFB 3420:2012-02DVS-EFB 3450-1:2007-05General characteristics of clinching are presented in When large elements are assembled often occurs a need for introducing a concentrated force into a composite structure. In such cases a single massive joint which could withstand the force has to be designed. The simplest example of such a joint is a bolted joint. However, phenomena such as delaminations, fibre pull-outs, and microbuckling , which oThe non-adhesive form-locked joint is manufactured along with the composite structure. The hole is cut in dry fabric which is then infused by resin or in uncured prepreg. Metal rings are then fitted to the hole so that the edge of the hole is curled up and locked between them. The structure is then cured in a vacuum bag or in an autoclave. After the curing a screw with a hole in it and a nut are fitted into the hole of the joint in order to clench it . A bolt An experimental investigation of the strength of the non-adhesive form-locked joint was carried out by Tomasiewicz and Czarnocki . The joiAfter the static tests, an inspection of the damage done to the laminate plates was carried out with the help of computed tomography (CT). Several failure modes were distinguished: fiber rupture, matrix cracking, matrix-cracking induced delaminations, and compressive shear .General characteristics of non-adhesive form-locked joining are presented in Another method of creating joints between the fibre-reinforced plastic composites and metal parts involves producing metal part with an array of pins protruding vertically from it. Once the array of pins has been prepared, it is necessary to integrate it with the composite material . During A number of techniques have been used to produce pins on the surface of metallic components for the purpose of hybrid joining . Those tThe process of manufacturing the pin arrays on the metal substrate is complicated and, therefore, cost and time consuming.Once the joint is manufactured, it is impossible to disassembly it without destroying it.Galvanic corrosion may occur in this joining method if a substrate made of aluminium alloys or steel are used along with CFRP composite ,23.The main advantage of the pin joints is that the joining process does not require manufacturing holes in cured laminate, so problems like delaminations and stress concentrations are mitigated. The metal pins cause very slight disruption of the reinforcing fibres, which may contribute to the good performance of the joint. On the other hand, the disadvantages of the pin joints are following:Although the pin joining technique does not cause such strong destruction of the composite fibres as, for instance, hole drilling, it causes certain local disruption of the composite structure such as localised fibre waviness, broken fibres and a resin-rich zones . Figure Composite–metal pin joints typically exhibit very low interface strength due to poor pin-composite bonding, which significantly affects joint performance . The misParks et al. investigated the strength of single lap shear pin joints of titanium alloys and CFRP composite. The adherends were joined by 6 × 6 array of cylindrical pins protruding from the metal adherent in the area of 25.4 × 25.4 mm overlap . The limIt was also discovered that the pins not only decrease the area damaged by the impact, but also prevent the loss of the residual strength and the propagation of the damaged area. The improvement in mechanical performance results from the load distribution across the joint. As long as the reinforcing pins bridge the two substrates, they are capable of transmitting load and, therefore, reduce the stress intensity at the crack front ,63. The Uscnik et al. conducted tests of pin joints made of stainless steel and carbon reinforced thermoplastic composite with two kinds of pins manufactured on the surface of the steel substrates: cylinder and ball-headed  64]..64].Double lap shear specimens were tested in tension. The specimens with cylinder and ball-headed pins exhibited different modes of failure. The cylindrical pins were pulled of the composite material, whereas the ball-headed pins were fractured as the bolt failed. It resulted in higher tensile strength of the joints with the ball-headed pins (150 N) than in the case of the cylindrical pin joints (110 N) . The perIn the same work multi-pinned double cantilever beam (DCB) specimens were tested . The cylThe cylindrical-pinned joints failed by the pulling out of the pins from the CFRP component . This reGeneral characteristics of pin joining are presented in Research group “Schwarz–Silber” funded by German Research Foundation proposed a set of novel ideas for joining carbon fibre reinforced composites with aluminium alloys: wire, foil and fibre concepts ,77,78 F. Since tThe transition elements insulating carbon fibres from aluminium alloy decrease or eliminate the possibility of galvanic corrosion ,77.The continuity of carbon fibres is not disrupted in any way .All the joining concepts are focused on separating carbon fibres from aluminium alloy in order to avoid galvanic corrosion, which appears inevitably when those two materials are in contact ,23 and mJoining the transition elements  to aluminium substrate is tedious, time consuming and the joint often constitutes the weakest point of the structure ,78,80,81Glass and boron fibres have often lower strength than carbon fibres. This means that the ultimate strength of carbon reinforced composite structure is reduced to the strength of those fibres if they are used as the insulating elements.The additional elements in the joints increase the mass of the joint.On the other hand, their disadvantages are following:Schumacher et al. investigated the joining of aluminium substrate and carbon fibres by titanium loops . The looCarbon fibres were threaded through the loops and the structure was impregnated with polymeric resin in order to create CFRP composite. Tensile tests of such specimens were performed. The fracture started with delaminations of the matrix at the interfacial zone to the aluminium structure. The complete failure of the specimens occurred by subsequent failure of the titanium wires close to the aluminium weld. Only in some cases, the fracture path was through the aluminium substrate . Taking Clausen et al. used glass fibre loops to join carbon fibres to an aluminium alloy substrate . In the In the scope of the work, however, no tensile tests were performed in order to measure the strength of the joint. An assumption that the glass fibre loop joint is by 50% lighter than a bolted joint in aluminium/carbon fibre reinforced structure was made , howeverThe first fibre failures were predominantly located in carbon fibres . This inWoizeschke and Schumacher investigated the joining of aluminium alloy and carbon fibres with the use of titanium foil concept . A laserThe manufactured specimens were subjected to tensile tests. Three different failure modes occurred . Three oGeneral characteristics of loop joining are presented in As mentioned in Additive manufacturing of both metallic and polymer composite is possible if short fibres are used to reinforce the polymer. Yuan-Hui Chueh et al. developed a method of integrated laser-based powder bed fusion and fused filament fabrication for three-dimensional printing of hybrid metal/polymer objects . Laser-bGeneral characteristics of interlock joining with the application of integrated laser-based powder bed fusion and fused filament fabrication are presented in Table 8An attempt to deposit melted metal (copper) at the top of polymer component was also presented in , but resGeneral characteristics of pin joining with application of fused filament fabrication and electroforming are presented in It seems reasonable to combine electroforming  with looCarbon nanotubes are known as extremely strong objects with strength as high as 200 GPa . TherefoComposite parts containing carbon nanotubes are currently much more useful in electronic applications  because The techniques of the mechanical joining of composite and metal structures, namely self-piercing riveting, friction riveting, mechanical clinching, non-adhesive form-locked joining, pin joining, and loop joining, have been reviewed in the present work. All those methods constitute alternatives to traditional bolted joining. The concepts of those methods are so different that it is hard to compare them directly. However, the key features of bolted joining and those techniques are presented in The first aspect of discussed joining methods is the possibility of disassembling and assembling of the joint without destroying it. Only bolted joining and non-adhesive form-locked joining methods have this advantage, however the only method which was designed purposefully to allow multiple assembly/disassembly of the joint is the form-locked joining. The bolted joints need additional protection  in ordeAnother category in which the joining methods can be evaluated are damages and flaws induced by the joining process. Significant mechanical and sometimes thermal damages are induced in bolted joining, self-piercing riveting, friction riveting and mechanical clinching, because the joining process requires cutting of the reinforcing fibres. However, in the case of the bolted joining there are some methods which can reduce the manufacturing damages . The othAnother criterion used for the assessment of the joining techniques was their usefulness for joining thermoset matrix composites as well as thermoplastics. Bolted joining, self-piercing riveting, and mechanical clinching have been used for joining both thermoset and thermoplastic matrix composites. However, due to high strains caused in the composite by self-piercing riveting and mechanical clinching, it is discussible if those methods should be used for joining thermoset matrix composites. It seems that those methods can induce even more process-induced damages in those composites than bolted joining, but a separate investigation should be conducted in order to prove it. Friction riveting is used for thermoplastic composites only, because this method requires melting of the matrix. Non-adhesive form-locked joining and loop-joining have been used for joining only the thermoset composite matrix. The use of those methods for thermoplastic matrix composites, if possible, would require some modifications of the joining process.The last but not least aspect of the discussed techniques is their level of development. The bolted joining is commonly used in all branches of composite industry. Self-piercing riveting and mechanical clinching are used in the automotive industry for creating composite-metal and metal-metal joints. Non-adhesive form-locked joints have been successfully used for creating fuselage-wing joints in gliders and motogliders. However, no proof of using friction riveting, pin, and loop joining in the industry has been found, though admittedly the friction riveting was considered as a method of creating joints in composite emergency bridges. Therefore, those methods require further and thorough investigation before employing them in commercial applications. The loop joining method in particular, in which the joining process of titanium loops to aluminium alloy structures seems faulty and unreliable, needs development and further tests if it is going to be used in industry.The most crucial feature of a joint is its strength. Therefore, the comparison of the strengths requires a separate discussion. As the single lap shear testing is the most common method of testing joints in both composite and metal joints and it has been used to test the strength of the joints in many works cited in the present work, the comparison of SLS strengths seems to be the best mean to compare the mechanical performance of the described joining methods. Not all the methods though were investigated by SLS tests. The SLS testing is not applicable to non-adhesive form-locked and loop joining, because the first method is used to create joints too large to be the part of a standard SLS specimen, while the nature of the second method prevents the lap joining at all. Therefore, only bolted joining, self-piercing riveting, friction riveting, mechanical clinching, and pin joining were taken into account in The maximum SLS strength results were selected for each method . HoweverIn the future, we can expect further development of 3D printing technologies assuming that current problems with strength of composites reinforced with carbon nanotubes are solved. Full utilization of mechanical properties of nanotubes would allow for the creation of a new generation of composite materials. They would be characterised by mechanical properties never seen before. At the same time, they would be well suitable for 3D printing which should allow for rapid prototyping and manufacturing of parts with very complicated geometries and magnificent mechanical characteristics. Ability to create strong parts with complicated geometries will certainly facilitate mechanical joining with metallic parts if necessary.In the meantime, pin joining and loop joining with application of 3D printing of continuous-fiber composites, electroforming, selective laser melting, and laser metal deposition could be investigated. Both these approaches seem to combine strength of composites reinforced by continuous fibers with rapid prototyping and/or manufacturing.The present article contains a description of the mechanical methods suitable for joining fiber reinforced composite materials with metal elements with the exception of bolted joining, which is described in the accompanying paper . A compa


In this study, a novel test system for estimating bending and torsion fatigue under selectable kinematic and dynamic loading modes was constructed. Using S355J2 steel specimens, a series of tests were conducted to determine material sensitivity to different load paths and loading modes. The experimental results were supplemented with the results of numerical analyses, on the basis of which the components of strain and stress tensors for subsequent analyses were determined in the entire working part of the specimen. An original method for determining specific strain energy components was used. The experimental results showed the grouping of data according to the mode of loading chosen. This could signify that the selected fatigue models are sensitive to certain loading scenarios. We performed in-depth data analysis and complex numerical simulations, formulating likely explanations for the observed effect. Non-monotonic alternation of stress states may lead to permanent changes in the structure of materials and is often the cause of the limited functionality of components. The vast majority of machines and engineering structures are subjected to complex and time-varying operational loads ,3,4,5,6.The fatigue properties of construction materials under uniaxial loads are best described in the literature ,8,9. HowMost experimental studies conducted under multiaxial fatigue load conditions were performed for independent tension: compression and torsion ,22. The The main objective of this study was to examine the fatigue properties of S355J2 steel using an energetic description. In this work, fatigue tests were conducted on specimens in kinematic and dynamic scenarios with four paths of loadings. The cyclic stress–strain response of the fatigue-tested specimens were analyzed using finite element method (FEM) analysis with the Chaboche model of cyclic plasticity. We determined the effectiveness of the most popular energy models for many variants of cyclic loads based on the original method of determining specific strain energy components to describe fatigue life. The fatigue lives of these specimens were compared between kinematic and dynamic loading test conditions.ϕ = 16 mm. The chemical composition of this material was previously published [Steel grade S355J2 was supplied for testing in the form of drawn bars with a diameter ublished , whereasThe custom-built test stand we used in our research is presented in A schematic diagram of the control and conditioning system used in the experiments is shown in A test specimen  was mounIn the conducted experiments, we assumed that the respective ratios of bending and torsion displacements or moments of force amounted to unity. All loading paths used in experiments were fully reversed, as shown in H were subjected to kinematic loading, whereas specimens marked as P were subjected to dynamic loading.For construction materials in an elastic state, stress can be easily calculated directly on the basis of strains . In this case, the generalized Hooke law can be used. However, this approach ceases to be adequate as soon as the first plastic strain appears. In this case, the relationship between the strain and stress is strictly dependent on the load trajectory. Then, a constitutive model of cyclic plasticity must be used. Constitutive models, despite their diversity in terms of scope of applications and phenomena they embrace, always consist of three basic components.The plasticity condition in which the von Mises equation is the most commonly usedH is the plasticity module.Associated flow rule, which allows the determination of the increase in plastic strain, which, according to Drucker’s postulate , is normThe hardening rule. In most cases, to calculate fatigue, the kinematic hardening rule is used, allowing the position of plasticity surface he model ,31, the i and Di  are the To determine the components of the strain and stress state in specimens prior to experiments, a finite element method simulation was conducted on a numerical model of the test stand, produced in ANSYS 2019 R1 software . This allowed the computation of the field of stress The numerical model of the fatigue machine consisted of two levers, a holder tool, and a test specimen . These vThe cyclic properties and other necessary material data required to introduce the Chaboche constitutive model were determined on the basis of the cyclic strain curves of the S355J2 steel specimens. The loading conditions of the specimen, implemented in experiments under kinematic or dynamic loading, ensured that only normal strains t values . Other sAs the chosen shape of the specimen  guided tSmith–Watson–Topper modelThe comparison between the fatigue life of specimens tested with two different load modes (kinematic and dynamic) required the selection of the correct fatigue parameter. Among many models found in the literature ,35,36,37The Smith–Watson–Topper (SWT) arameter  is basedChu modelChu  proposedLiu modelFor multi-axial loads, Liu  proposedVirtual work is calculated similarly Glinka modelGlinka et al.  proposedThe authors, aiming to include the impact of mean stresses in the parameter in Equation , proposeEllyin modelThe Ellyin model ,44 propoFor selected cases of proportional and non-proportional loads, the energy is calculated using the following formula:When applying the Ellyin model, which refers directly to the elasto-plastic strain energy density, it was necessary to calculate it properly using the strain and stress tensor time curves determined previously through numerical simulations.Previous studies ,45 preseThis method of identification and calculation of the total strain energy density components , as descW is the value of the strain energy or fatigue energy parameter, and A and B are parameters calculated for this regression model. lgNf=A+BlValues of All considered energy models achieved good correlation with experimental data regardless of loading path, but only within each loading mode used in the experiments (either kinematic or dynamic).All models described above use the work of stress on strains. However, only the Ellyin model considers the hysteresis loop directly in the calculation of strain energy. The SWT, Liu, Chu, and Glinka models propose the use of certain values describing the state of stress and strain that are relatively easy to calculate. However, according to Liu , their rEvaluating the results presented in Comparing the durability under different load methods (kinematic and dynamic), we found that the value of elastic–plastic strain energy or any energy parameter can be significantly different for the same achieved fatigue life.Searching for the underlying reasons for the difference in strain energy between kinematic and dynamic loading modes, we directly analyzed the time courses of the moment of force and displacements of bending and torsion levers. acements a did notA similar effect was observed for tests under dynamic loading. However, in this case, the observed effects were different. Among the considered energy fatigue parameters, none consider the temporal transiency of strain tensor and the corresponding stress tensor. As a consequence, the values of strain energy (stress work on strains) were calculated with these models for a given time instance. Thus, the results ignore the changes in the values of the strain and stress tensor components during the fatigue process, affecting the strain energy or any energy parameter calculations.The numerical constitutive cyclic-plasticity model (Chaboche) used in calculations does not consider an important transiency in material properties caused by damage accumulation or crack initiation, propagation, etc. As a result, the obtained strain and stress tensor values are likely impacted.A second limitation of the considered energy fatigue models is related to their spatial sensitivity . This is understood as the need to calculate strain energy only at the most stressed point in the smallest cross-section of the specimen. This, in addition to sampling at an arbitrarily determined time instance, cannot provide complete information on the distribution of strain energy in a representative volume of the specimen. This volume can be considered to be subjected to plastic strains.In comparison, The numerically obtained values of strain energy and energy parameters were expected to be correctly estimated by a single regression model, regardless of loading path and irrespective of loading mode (dynamic or kinematic). Only the former of these assumptions was fulfilled, suggesting that the evaluated common fatigue models might be not entirely applicable in every load case.We conducted experimental research of the bending and torsional properties of S355J2 steel under two different modes of load application, which showed the significant limitations of some popular energy parameters used to determine fatigue durability.Despite similarities observed in the fatigue life of specimens tested under kinematic and dynamic modes of load application, neither energy parameters nor strain energy calculations allowed for the common regression model to be implemented for all results. Kinematic and dynamic data required separate regression models.The energy parameters published in the literature were in good agreement with data obtained from different loading paths, but only within specific groups of results obtained from either the kinematic or dynamic mode of loading.Among the possible reasons for such behavior, we identified the three most likely causes:The constitutive model of cyclic plasticity (Chaboche) influences the numerically obtained values of strain and stress tensors. The used model assumes that these values are stable and do not change in time, in contrast to actual fatigue damage. This can significantly influence the energy parameter and strain energy values.The described popular fatigue models consider only a singular arbitrary chosen time instance in fatigue life to compute either the energy parameter or strain energy. This results omit the time dependency in strain energy.The spatial sensitivity  of fatigue parameters proposed by many authors is a limitation affect the accuracy of the results. This is because when calculating many energy parameters as a single parameter, only the most stressed location is considered. As a consequence, certain parts of plastic strain energy deposited in the specimen are omitted.The custom-designed and built fatigue test stand will enable further investigations into bending and torsion fatigue behavior of materials under many load paths, including random loads and both kinematic and dynamic load application mode.As energy models do not consider the change in energy over time associated with the initiation and development of fatigue damage, the variability of energy parameters must be considered during the fatigue test and an algorithm must be developed for estimating energy values over a specific section, area, or volume depending on the analyzed load variant. This will be our future research objective.Future work will consider the sensitivity of structural materials to non-proportional hardening under these two loading modes.


Schettler et al.) In this framework, tool use consists of the mutual modification of the body, device, and world  , as these factors cause different gradients of change in body representations.Regarding the role of the body in clinical practice and especially in neurorehabilitation, Matamala-Gomez et al.). The paper from Lancioni et al. presents an overview of recent technology-aided programs designed to help people with significant disabilities to engage in adaptive responses, functional activities, leisure, and communication and thus help them interact with their physical and social environment and improve their performance/achievement. Two contributions are innovative research approaches and neurorehabilitation techniques during childhood. These approaches involve the use of an augmented reality system for unveiling face topography in very young children  and the application of subthreshold vibrotactile noise stimulation to improve manual dexterity in a child with developmental coordination disorder . The only study approaching a psychiatric condition, applied the rubber hand illusion in individuals with obsessive-compulsive disorder (OCD). This study suggests heightened malleability of body image in OCD and paves the way for a tolerable technique for the treatment of OCD .Novel technologies are expected to open up new neurorehabilitation opportunities for the body. One of the reviews examined experimental and clinical studies that have explored the manipulation of an embodied virtual body in immersive virtual reality for experimental as well as clinical pain relief, suggesting the potential of using an embodied virtual body in immersive virtual reality . Spichala and colleagues explored self-paced embodiable neurofeedback for post-stroke motor rehabilitation . Pizzamiglio et al. showed that patients with apraxia have difficulties in selecting elements of object-directed actions pertaining to habitual as well as goal-directed factors. Additionally, a few studies have further examined the neural underpinning of the action observation network  and transcranial magnetic stimulation .However, among the original research articles, a large group of contributions focused on promising interventions for more conventional rehabilitation following motor impairment after brain lesions . Surprisingly, this study revealed that the majority of the respondents did not evaluate the use of assistive technology. This result emphasizes the need for more thorough knowledge and use of outcome scales for improvement in the quality of assistive device evaluation . This study examined how passive learning of a home-used, neural-connected, and sensory-enabled prosthetic hand influenced the perception of artificial sensory feedback in the user. Participant interviews indicated that the naturalness of the experience and engagement with the prosthesis progressively increased, suggesting that artificial somatosensation may decrease prosthesis abandonment. From a clinical perspective, these results support the use of new rehabilitation perspectives that are necessary for successful integration of rapidly evolving technology into more effective rehabilitation practices aimed at restoring a sense of integrity in a damaged body.Patients with brain lesions were not the only clinical population considered in this Research Topic. One of the contributions focused on the use of outcome measures to assess various areas of interest pertaining to lesions of the spinal cord . This novel framework consists of a linear EEG mixing model and an emotion timing model. Building the linear EEG mixing model and decomposing the EEG source signals from the collected EEG signals improves the temporal classification of the EEG feature sequences, elected as the emotion classifier. Endo et al. used an adapted intentional binding effect paradigm to investigate whether the sense of agency can be used to measure the quality and experience of physical human-machine interaction schemes that allow the human operator and the collaborative machine to act as a “single entity.” One of the studies used functional near-infrared spectroscopy to measure the effects of moderate-intensity and high-intensity short-term aerobic exercise on prefrontal activity related to food images and recorded the subjective feelings of appetite in methamphetamine-dependent users .The final theme that we identified in the contribution centers around innovative methodology, pioneering paradigms, and novel techniques. Using a multi-channel electroencephalogram (EEG) for automatic emotion recognition can help brain-inspired robots in reading people's interactive intentions and states (In conclusion, this Research Topic collects an impressive body of literature on “Embodying Tool Use.” Overall, the contributions extend and enrich the previous multidisciplinary approach and translational applications. However, despite the significant progress made in our understanding and the real-world relevance, there are boundless directions, endless possibilities, and exciting challenges yet to be explored in future research.MP planned the topic. MP and GG edited the most of papers included in the topic. YC and JB edited some papers included in the topic. GG drafted the editorial which all authors reviewed and approved. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Forecasting data center cooling demand remains a primary thermal management challenge in an increasingly larger global energy-consuming industry. This paper proposes a dynamic modeling approach to evaluate two different strategies for delivering cold air into a data center room. The common cooling method provides air through perforated floor tiles by means of a centralized distribution system, hindering flow management at the aisle level. We propose an idealized system such that five overhead heat exchangers are located above the aisle and handle the entire server cooling demand. In one case, the overhead heat exchangers force the airflow downwards into the aisle (Overhead Downward Flow (ODF)); in the other case, the flow is forced to move upwards (Overhead Upward Flow (OUF)). A complete fluid dynamic, heat transfer, and thermodynamic analysis is proposed to model the system’s thermal performance under both steady state and transient conditions. Inside the servers and heat exchangers, the flow and heat transfer processes are modeled using a set of differential equations solved in MATLAB™ 2017a. This solution is coupled with ANSYS-Fluent™ 18, which computes the three-dimensional velocity, temperature, and turbulence on the Airside. The two approaches proposed (ODF and OUF) are evaluated and compared by estimating their cooling effectiveness and the local Entropy Generation. The latter allows identifying the zones within the room responsible for increasing the inefficiencies (irreversibilities) of the system. Both approaches demonstrated similar performance, with a small advantage shown by OUF. The results of this investigation demonstrated a promising approach of data center on-demand cooling scenarios. Data center thermal management is generally accomplished by providing cold air from a raised floor into the server aisle. In some designs, the cooling is aided by the strategic placing of heat exchanger arrangements: overhead, in-row, rear-door. Limited academic work exists on each system, where most of the available information is provided by the equipment suppliers in catalogs and manuals.The majority of the authors center their efforts on cases where centralized CRAH units provide the cold air. The air is then ducted and distributed to the data center room aisles ,2,3,4. THong-Koo et al.  used theA scarce number of publications have used overhead cooling as a distributed cooling system. Some authors used the overhead modules as a secondary cooling source to prevent hot spots. Heydari and Sabounchi  and HeydWu  used CFDThis work focuses on the modeling and comparison of two different overhead cooling configurations: Overhead Downward Flow (ODF) and Overhead Upward Flow (OUF). In both cases, the overhead systems are used as the sole source of cooling for the data center room. Energy efficiency is examined using the Entropy Generation Rate to locate and quantify the inefficiencies in the cooling system. Shah et. al  was the Kock and Herwig ,11 develThe application of overhead systems in data centers raises interesting questions that, to the best of our knowledge, remain unaddressed in the literature. One example is the lack of conclusiveness as to what is the more energy-efficient strategy to deploy overhead cooling, either injecting downward cold air into the aisle or removing hot airflow upwardly from the aisle. Distributed cooling such as overhead heat exchangers can advantageously operate when combined with dynamic on-demand cooling applications, in such a way that cooling can be delivered to the right location and at the right moment.In this work, we focus on quantifying the energy efficiency of downward and upward overhead airflow, as well as the transient behavior of such systems. Our analysis incorporates the simultaneous unsteady response in the heat exchangers, servers, and the cooling flow. We will demonstrate the importance of each component in the cooling dynamics and how relevant it is to contain the aisle.This paper showcases the early efforts of an ambitious project that intends to advance the research on the thermal energy efficiency of dynamically-operated data center HVAC systems. At this first stage, we aim to develop transient numerical models of the contributing components inside the server room. With this in mind, we created an idealized data center geometry to apply first and second law thermodynamic principles, so that we can systematically examine the system’s thermal efficiency.The room transfers no heat to the outside ,Fully-contained aisle, in other words, air only flows through servers and heat exchangers,Heat conduction allowed through the aisle containment walls,Fluid flow in the turbulent regime,Constant server heat dissipation of 1 kW, for a total of 100 kW of required overhead cooling.The data center room is comprised of 10 racks with 10 servers (4U) each and five overhead heat exchangers placed at the aisle ceiling. k-The Airside is comprised of the room and hot/cold aisle sections  and it i follows :Continuity:Momentum:Energy:Turbulent kinetic energy:S is the rate-of-strain tensor.Rate of viscous dissipation:We approximate the transient response in the servers via the lumped approach introduced by Erden et al.  and DemeK, is determined as a function of the server effectiveness, The heat transfer in the server is modeled by approximating its behavior to that of a heat exchanger, where an average temperature Experimental data presented in  were useThe overhead system has five air-to-liquid cross-flow heat exchangers. The dynamic behavior is dependent on the thermal inertia of metals and fluids, as well as the geometric arrangement. The unsteady response of cross-flow heat exchangers has been extensively investigated starting in the 1950s. Because this is a multi-dimensional and unsteady physical situation, no analytical and compact solution exits.Del Valle and Ortega  investigThe air stream, water stream, and wall were modeled via individual energy balances, forming a system of three unsteady non-linear differential equations. The model was subject to the following assumptions: (i) negligible heat losses, (ii) no thermal energy sources or sinks, (iii) single-phase flow, (iv) uniform heat transfer coefficients, and (v) uniformly-distributed wall thermal resistance in the entire heat exchanger with negligible axial heat conduction .The non-dimensionalized set of equations yields : (11)∂Twa and w correspond to air and water, respectively. The complete mathematical formulation may be found in [The subindices found in .Servers: heat transfer between the electronics and the cooling air; pressure drop as the air flows through the server, undergoing significant impedanceOverhead heat exchangers: heat transfer between the chilled water and the airflowAirside: the temperature difference between the room and the aisle induces heat transfer through the containment walls; turbulent viscous dissipation of momentum becomes non-negligibleOne consequence of the second law of thermodynamics is the concept of Entropy Generation, which quantifies loses (irreversibilities) that take place in a process, in this case being data center cooling . The proThe transient entropy balance in the servers and overhead system yields: The turbulent fluid flow and temperature distribution in the Airside require expressing the Entropy Generation at the infinitesimal level. A procedure first introduced by Kock and Herwig  was succThe four terms in  are indiThe total Entropy Generation rate in the Airside is obtained by integrating Equation :(20)S˙gek-TM. The velocity and pressure fields were coupled using the SIMPLE algorithm, and the nodes were interpolated via a second order upwind scheme.A complete three-dimensional simulation of the fluid dynamics and heat transfer process that takes place within the Airside (aisle + room) was conducted using a transient turbulent model  viaAfter one time step computed in Fluent, MATLAB uses the obtained results as inputs to solve the already mentioned equations and to update the boundary conditions in Fluent—depicted in l domain . The samSince the servers and overhead heat exchangers are modeled outside Fluent, the Airside numerical domain considers those zones as void volumes.Fluent computes the Airside turbulent flow and moves the solution forward by one time stepThe airflow data are used as inputs to the servers and heat exchangersMATLAB solves the servers and heat exchangersMATLAB output data become inlet boundary conditions for Fluent, and the fluid flow is updatedGo back to Step 1 under these new conditionsThe solution of the complex system of algebraic and differential equations was carried out algorithmically as follows:To enhance the early numerical convergence .We now compare all the sources of thermal irreversibility inside the room, for which the thermodynamic cycle of The first two terms on the right-hand side of Equation  considerWe reiterate that the scope of this work ignores potential contributors to the Entropy Generation such as pumps, chillers, and cooling towers. Our claims are limited to phenomena occurring inside the room.Equation  can be rn Number . Figure If the containing walls are perfectly insulated and considering the steady state condition  in transient scenarios. Dynamic modeling becomes crucial in the ultimate goal of achieving accurate on-demand cooling of data centers.The server temperature distributed uniformly throughout the racks. The positioning of the overhead heat exchangers allowed for the cooling airflow to undergo less resistance than the common perforated tile flow. This led to a uniform distribution of cold fluid entering the servers.Aisle containment reduced the Entropy Generation in the Airside to negligible levels when compared to previous results from a legacy data center.Using a second law analysis, we determined the room cooling efficacy, which quantified the deviation of server thermal management from optimum operation.In terms of cooling performance, the OUF and the ODF approaches showed nearly identical results ; selecting the correct scheme might potentially depend on other aspects, e.g., geometrical, mechanical, economical.The unsteady first and second law metrics presented in this numerical study show promise towards the grand goal of providing instantaneous thermal management as the data center demands it.In this study, we introduced a numerical model that simultaneously simulates the dynamics of servers, overhead heat exchangers, and the turbulent airflow in an idealized data center room. Based on the discussed results, we conclude the following:


In this case, we will describe a 68-year-old man with combined femoral and tibial bone deformities who underwent robotic arm-assisted total knee arthroplasty (RATKA) to treat his severe osteoarthritis in the setting of extra-articular deformities that altered the native anatomical axis and the kinematics of the deformed extra-articular bony structures which chronically generated a neomechanical axis. The combination of severe osteoarthritis with extra-articular deformities made the RATKA method the best surgical treatment option taking into account altered kinematics of the native joint which conventional jig-based total knee arthroplasty would not have prioritized during bony cuts and implant positioning. The patient underwent successful knee arthroplasty with robotic arm-assisted technology with restoration of the mechanical axis. Robotic arm-assisted total knee arthroplasty (RATKA) uses preoperative 3-D helical computed tomography images of the patient's anatomical bony structure to virtually plan femoral and tibial replacement components, implant positioning, and intra-articular balancing. RATKA's virtual planning may aid in greater component precision, implant accuracy, soft tissue protection, increased patient satisfaction, fewer instrumentation trays required intraoperatively, and overall improved safety of total knee arthroplasty . There hTotal knee arthroplasty (TKA) has been a longstanding treatment for severe osteoarthritis that may debilitate and/or compromise a patient's functional status. Traditional arthroplasty replacements involved the use of standardized predesigned jigs intraoperatively to position the implant component, and the positioning of the implant was primarily based on the anatomical axis of the joint. Severe osteoarthritis can lead to abnormalities in the anatomical axis due to the development of osteophytes and sclerotic bony surfaces, and these alterations change the kinematics of the native joint. In order to ensure a balanced joint during an arthroplasty procedure, the kinematics of the joint must be taken into account with an understanding of the current mechanical axis. Robotic arm-assisted TKA allows the surgeon to restore normal kinematics to the knee by reproducing alignment, balancing surrounding soft tissue, and decreasing the variability by increasing surgical precision which in turn all together leads to the restoration of the joint line . Also, tWorldwide use of robotics in orthopaedic arthroplasty procedures has been utilized since the 1980s, and then, the discussion of robots in the future potentially reducing human error by obtaining surgical accuracy, quality control reproducibility, and eliminating excessive outcome variations were the aim for the future as technology continued to improve . To dateA 68-year-old man with a history of a distal right femoral diaphyseal fracture that resulted in malunion and right varus knee deformity previously treated with a high tibial osteotomy (HTO) presented with severe osteoarthritic pain of the right knee. The patient had a distal femur fracture at the age of 18 years and was treated conservatively which resulted in malunion and shortening of the leg. At the age of 44 years, he was diagnosed with osteoarthritis and underwent a high tibial osteotomy. However, knee pain continued to get progressively worse especially for the last few years. The patient's social history included using an assisted walking device, being an active cigarette smoker, and combating chronic hypertension. Clinical evaluation and radiographic imaging confirmed the diagnosis of severe bone-on-bone tricompartmental osteoarthritis . The patThe surgical planning included obtaining a MAKO protocol CT scan. The robotic software converts CT images to a virtual model where a surgeon can plan on implant size, positioning, and joint alignment. As demonstrated from images, this patient had a distal femur fracture, which had resulted in malunion. Because of malalignment, the patient had recurvatum deformity. The use of the anatomical axis and jig-based technique would have resulted in the positioning of the knee implant into hyperextension. Also, it would have been difficult to use the jig-based technique in the setting of severe deformity of the distal femur. Also, deformity in the proximal tibia due to a previous high tibial osteotomy would have resulted in difficulties in establishing the mechanical axis. Because of robotic software, we were able to plan the implant position in a way that it would restore the mechanical axis.After exposure, femoral and tibial trackers were applied. The hip center of rotation was registered followed by medial and lateral malleolus registration. Bony landmark registration was done. Now, we proceeded with removing all the visible osteophytes and remaining ACL. Often times, it is difficult to remove the PCL completely without making the tibial cut in tight knees with longstanding deformities.We next proceeded with identifying the existing deformity without any correction and with corrective maneuver and checking the balances on the medial and lateral side . With thNext, appropriate tibial cut was made. The previous existing hardware was removed. With the help of the lamina spreader, the balance of the ligament was checked again in extension and flexion. We were able to open up the flexion gap more. Moving the planned femur implant anteriorly and thereby planning to remove more bone posteriorly, we were able to get the numbers closer to the extension gap as evidenced by Now, as evidenced by this figure, on the right bottom corner, the extension gap is 19 and 18 mm and the flexion gap is 19 mm laterally and 22 mm medially. At this point of time, the femoral implant is in 1° external rotation. So now, we needed to close down the medial gap in flexion. We were able to do this by pinning the femoral implant laterally and internally rotating the femoral component. By this maneuver, we were able to predict almost equal gaps in both flexion and extension. We proceeded with the femoral cuts. Trial implants were positioned.The patient remained in the hospital for 2 days to ensure that adequate pain management was obtained prior to being discharged home. He returned for a follow-up visit in 3 weeks postoperatively . During At his six-month follow-up appointment, the patient reported no pain with RATKA replacement. Postop X-rays demonstrate excellent alignment of the mechanical axis . The finRobotics involved in various surgical procedures over the years has proven that it promotes a positive impact on patient care by enhancing inpatient recovery and expediting the time to discharge . InvolviConventional JTKA techniques use a blueprint for the implant positioning that prioritizes the patient's anatomical axis. Patients with longstanding osteoarthritis inclusive of osteology changes may have some extensive osteophyte formation with or without angular deformities that can lead to distortion of the kinematics within the native joint, thus altering the anatomical axis. The use of the robotic arm-assisted device to position the implant during arthroplasty takes into account both the anatomical and mechanical axes, and this technology gives the user an advantage when treating altered native joints. However, the conventional JTKA method may not yield the best estimate of implant positioning or bone resurfacing when such anatomical axis alterations have occurred. Sodhi et al. concluded that utilizing preoperative CT images to develop a plan for the RATKA allows appropriate assessment of the deformity preoperatively and execution of a plan for balanced and aligned total knee arthroplasty . The abiExtra-articular deformities can be very challenging to correct and most often occur after a malunited fracture, and femoral malunion deformities can result in distal femoral recurvatum with varus deformity leading to severe osteoarthritis . Prior cWith further supporting data of RATKA's superior treatment when compared to the conventional JTKA in patients with bone deformities seeking surgical treatment by way of TKA, the discussion of RATKA replacements being superior to conventional JTKA replacements in the treatment of complex extra-articular deformities that alter the kinematics of the native joint and generate a mechanical axis may be warranted.


The currently available manipulation technologies offer high positioning accuracy, yet these devices significantly grow in complexity in achieving compliance. We explore soft and compliant actuator material with a mechanical response similar to gel-like samples for perspective miniaturized manipulators. First, we demonstrate three techniques for rendering the bulk sheet-like electroactive material, the ionic and capacitive laminate (ICL), into a practical manipulator. We then show that these manipulators are also highly compatible with electron optics. Finally, we explore the performance of an ICL manipulator in handling a single large cell. Intrinsic compliance, miniature size, simple current-driven actuation, and negligible interference with the imaging technologies suggest a considerable perspective for the ICL in spatially dense arrays of compliant manipulators for microscopy.Non-destructive handling of soft biological samples at the cellular level is becoming increasingly relevant in life sciences. In particular, spatially dense arrangements of soft manipulators with the capability of  Precise biomedical applications often involve manipulation of soft and fragile objects: gel-like substances or delicate samples of biological origin. Biological systems on any scale (from viruses and cells to organs) create mechanical cues in response to mechanical forces being applied to them  hard robots made of rigid materials  can be engineered to be compliant toward softer biological subjects (such as humans) mainly thanks to their highly sensitive sensors and high-precision control algorithms. However, in case of grave malfunction, these systems could cause serious damage, creating the need for intrinsically soft devices  samples are often widely distributed cellular structures with their characteristic dimensions and mechanical properties varying widely between specimens and in time. Consequently, scalable and compliant manipulators are favored for biomaterial manipulation, whereas the absolute positional accuracy can be of secondary importance. Moreover, if a large number of semi-independent actuators are involved, then the feedback-loop-based systems (as in AFM instruments) start to increase in complexity exponentially. Furthermore, in some cases, larger biological systems (above 100 μm) than just a single cell need to be characterized . In such cases, much larger probes than the standard AFM probe are needed for accurate characterization  samples commonly exhibit viscoelastic properties . ICLs have an exclusive set of desirable properties for this purpose. Their soft and compliant nature has made ICL materials appealing to various biomimetic soft robotics applications  or glass fiber fabric ] was fastened and tautened onto a frame. Then the membrane solution was applied to the fabric using a brush. After the evaporation of solvents, an open-pore ion-conductive polymeric gel membrane was formed. Then, electrodes were sprayed on both sides of the membrane using an airbrush (Iwata). Finally, gold leaf (Giusto Manetti Battiloro 24K transfer leaves) current collectors were glued on the laminate using a rolling method similar to what has been previously described elsewhere  pieces of ICL (in red) were cut and clamped face-to-face between three gold contacts (in orange), as shown in The gripper used in this study was fabricated as described in section Fabrication of ICL Actuators  with the following modifications. Two 5.0 × 1.2 × 0.15 mmThe next case study considers an ICL actuator with a flexible and conductive probe integrated into the material already during fabrication. For example, various probes and tubes can be integrated into the material in the final step during the current collector attachment. We designed an ICL with an integral wire probe that bends along with the actuator. This can be considered a two-in-one manipulator configuration, where the free end of the cantilevered probe can manipulate a sample mechanically to measure its mechanical properties, and simultaneously, various integrated sensors could be used to evaluate the electrical, electrochemical, and chemical properties of the same sample. The main challenge with this approach is to select and attach such a probe that a sufficient deflection magnitude is still maintained in the ICL actuator after the integration. The probe's mechanical properties should not interfere with the actuation, whereas it should still be functional as a probe . We chose to integrate a very fine gold-coated tungsten wire (diameter: 30 μm), as illustrated in d = 3 cm) using tape, and the first current collector was attached to one side of the laminate as usual. Then, the actuator was removed from the rod and turned over. About 6 cm long gold-coated tungsten wires (diameter: 30 μm) were cut and tightly fastened over the composite on the rod using tape  already in the early stages of the composite preparation. For example, we integrated inert, flexible non-conductive PTFE, PET, or polyimide tubes into the membrane of the actuator. Inspired by the proboscis of a mosquito, the ICL-tube assembly can behave as an active pipette tip for depositing or extracting liquids to/from desired areas, as schematically shown in The fabrication of an active capillary manipulator started with the integration of a capillary tube into the supporting fabric structure to achieve the centermost position for the tube. One fiber bundle was first removed from the glass fabric and then replaced with a tube  . The fabHitachi TM3000 scanning electron microscope was used at 15 keV acceleration voltage to visualize the probing of soft samples in vacuum. The actuator was fastened between gold clamps commutated to a DC power supply.The cross-sections of actuators were visualized with the same Hitachi TM3000 scanning electron microscope. Samples for SEM micrographs were first cryofractured using liquid nitrogen to obtain clearer cross-sections and then taped on a metal sample holder with their cross-sections facing up. The samples, together with the sample holder, were sputtered with 5 nm of gold using a Leica EM ACE600 sputter coater to obtain more detailed SEM micrographs.5x and 10x objectives were used for optical microscopy.The actuation of active tweezers was characterized by post-processing the recorded videos with video recognition implemented in the Vision Development module in LabView, National Instruments. Digital templates were created of visually distinctive areas  and tracked frame-by-frame using the grayscale value pyramid pattern-matching algorithm.The influence of various integrated probes was comparatively studied on samples from the same batch with different integrated probes . The disElectrical driving signals were generated, and impedances registered using IVIUM CompactStat and Princeton Applied Research Parstat 2273 electrochemical workstations. All electrical measurements were done using electrochemically inactive gold contacts.The measurement setup for the comparative performance study  has beenThe mechanical characterization of non-homogeneous multilayer composite materials with integrated probes is not straightforward. For example, tensile testing in the same direction as the reinforcement fibers is expected to be dominated mostly by the mechanical properties of the fibers  and not by the bulk active material itself . Since bending performance is the most important characteristic of this type of actuators, it is most reasonable to use bending stiffness (the actuator's resistance to bending deformation) to characterize and compare different manipulator configurations. Bending stiffness is a function of Young's modulus and the area moment of inertia of the sample.The bending stiffness of the bare ICL material and the ICL-probe assemblies was characterized using the end-loaded cantilever beam configuration. The actuators were fastened between clamps, and different weights were attached on the tip of the cantilever. The resulting deflection was measured from the video. See BS) of different manipulator assemblies was calculated using the following formula for end-loaded cantilever beams:The bending stiffness , l is the free length of the cantilever beam (18 mm), and h is the measured deflection in the cantilever beam due to the added load.where Capelin eggs for manipulation experiments were purchased from the local supermarket. In the conductive probing experiment, a drop of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]) ionic liquid was used.The considered manipulator concepts suggest pathways to transfer the ICL actuators from simple configurations suitable for material characterization toward practical arrangements as microscope accessories. Modifications in various stages of the ICL fabrication enable us to manufacture considerably different functional manipulators. Both electronically conductive , and non-conductive and inert  tools can be integrated into the ICL electrode or membrane during the ICL manufacturing.In the presented active manipulator concepts, the ICL was used to bend a supplementary component; thus, matching the ICL actuator bending stiffness to its supplement is essential for effective operation. In general, the supplementary components increase the bending stiffness of the manipulator, effectively creating a load for the actuator. In general, the position of the textile base material determines the location of the ICL's neutral layer, which is the layer with zero strain on bending. However, ICL manipulators were manufactured with tools placed in two locations: in the membrane layer in the center of the laminate, and close to one side of the laminate. In the former case, the tool location coincides with the textile reinforcement; thus, the bending stiffnesses of the tool and the ICL are expected to be additive. Indeed, The placement of the tool on the surface of the laminate potentially affects the bending performance due to a shift in the location of the neutral layer toward the electrode carrying the tool. Therefore, for more predictable actuation behavior in both directions, it is advisable to attach probes already in the neutral layer . However, from the manufacturing point of view, the ease of attaching probes only in the final manufacturing stage might be a more significant advantage in some cases.The ICL actuator is a capacitive device very similar to electrical double-layer capacitors (EDLC). The defining difference is that the swelling and contraction of electrodes upon the application of an electric signal that drives the bending motion in ICLs is seen as a disadvantage in EDLC-s. The actuation in the ICL is proportional to the charge stored in it . −1 by applying a 10-μA input current; the ICL terminal voltage spanned by 0.21 V only. The superimposed drift of the tweezer gap in −1) was much smaller than that imposed by the current actuation signal. Consequently, the ICL manipulator matches well with the typical in situ microscopy methods, offering actuation control at fast as well as at slow rates.Precision control of the ICL using current signals is demonstrated using the tweezer configuration. The ICL tweezer gap, as shown in The excellent stability of ICL tweezers is further demonstrated in ESR, and the voltage drop at the electric double-layer at the electrodes denoted as UEDL. In the particular current density value, UESR was larger than UEDL. Moreover, the ESR value decreased noticeably (5.5%) during cycling, possibly due to water absorption by the ionic liquid electrolyte and by Joule heating. However, using current as the feedback parameter ensured a uniform triangular actuation pattern throughout the lifetime experiment, deterring possible dependence on the ESR variations and the current density level.Further advantages of using current to control the speed of the manipulator are highlighted in The viscoelastic properties of the ICL material imply that the actuator's shape at zero position, i.e., the position with zero charge injected, is tunable and that it also adjusts further according to the applied load. The intrinsically soft ICL manipulator is particularly well-suited for probing soft samples, offering the necessary safety margin and conforming to samples of non-uniform geometries. The electroactive tweezer arms were used to manipulate a delicate capelin egg as follows. First, the sample was attached to the grips at zero charge; the gripped load adjusted itself in time so that the contact pressure approached zero. Then, a differential load was applied by injecting charge to the ICL to clamp the capelin egg with the tweezers. The ICL includes a liquid electrolyte essential to its working principle. This raises the question—are the ICL manipulators stable in the vacuum chamber of conventional SEM instruments? A simple biological sample (a human hair) was manipulated in the SEM vacuum chamber to prove that the ICL material can also be used to probe samples in the vacuum environment. The integration of conductive probes or sensors into the ICL opens up the possibility to characterize the mechanical and electrical properties of a sample (even simultaneously). As the current and voltage levels to drive an ICL are small, the interference from the actuation signal to the conductivity measurements is considered to be negligible. The possibility to measure the electrical properties of various samples was evaluated with the wire-carrying manipulator by probing a conductive sample—a drop of ionic liquid . Figure Moreover, the electrical properties of the assembly were tested using a simple continuity test. The actuation of the ICL manipulator (measured using a laser distance meter at 5 mm from the manipulator's base) reversibly created contact between the integrated probe and the liquid sample, as schematically shown in The ICLs have previously been demonstrated primarily for their actuation capability. We have explored how small changes in the manufacturing process can render these materials useful for prospective technologies of miniaturized manipulators. We have shown that ionic-liquid-based ICLs can be operated in air or in a vacuum, enabling probing of biological or other samples under an optical as well as a scanning electron microscope. The latter is enabled by the non-evaporative nature of ionic liquids and by the negligible interference from actuators to the electron optics.The application-based design of ICL manipulators is an essential step ahead—instead of just characterizing the actuating material, we modified the ICL assembly procedure to construct practically relevant devices, i.e., a manipulator for interacting with soft  samples. We explored four different manipulator configurations and demonstrated the integration of various tools—a simple cantilever probe, a needle probe, a capillary tube, and tweezer arms that are then steered by the ICL actuator.The capillary tube integrated into the ICL's textile base demonstrates new application possibilities that take advantage of the uniform and widely distributed nature of textiles that have a well-defined structure in the mm-scale, but span in meters in two dimensions. The integration of fluidics in a self-morphing flexible textile platform is an essential step toward new health and care applications.However, the biocompatibility of the actuators is of crucial importance when probing living tissues, cells, or other biological samples. ICL does offer actuation at relatively low potentials, thus providing a high safety margin in terms of electrical control. However, the choice of ICL constituent materials has, to date, been driven primarily by their impact on the composite actuation performance, consequently reaching to harmful substances , and little research has so far been focused on the safety and biocompatibility of ICL materials. There have been attempts to encapsulate ICL materials with biocompatible passive layers. However, every passive addition to the active material reduces its maximum achievable deflection. Therefore, further development is suggested in the field of efficient encapsulation methods to enable safe probing of various samples in liquid, vacuum, or air without compromising the actuation performance to a large degree.All datasets generated for this study are included in the article/IM designed and analyzed the active tweezer, performed data analysis, participated in writing, and revising of the manuscript. PR did the comparative characterization of manipulator concepts, designed and analyzed the probe manipulator, performed data analysis, participated in writing, and revising of the manuscript. FKr designed, prepared, and analyzed the active pipette tip. FKa performed the vacuum manipulation study. UJ took part in the discussions and revised the manuscript. AA took part in the discussions.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Abnormal endometrial receptivity is one of the major causes of embryo implantation failure and infertility. The plasma membrane transformation (PMT) describes the collective morphological and molecular alterations occurring to the endometrial luminal epithelium across the mid-secretory phase of the menstrual cycle to facilitate implantation. Dysregulation of this process directly affects endometrial receptivity and implantation. Multiple parallels between these alterations to confer endometrial receptivity in women have been drawn to those seen during the epithelial-mesenchymal transition (EMT) in tumorigenesis. Understanding these similarities and differences will improve our knowledge of implantation biology, and may provide novel therapeutic targets to manage implantation failure.A systematic review was performed using the Medline (Ovid), Embase, and Web of Science databases without additional limits. The search terms used were “(plasma membrane* or cell membrane*) and transformation*” and “endometrium or endometrial.” Research studies on the PMT or its regulation in women, discussing either the endometrial epithelium, decidualized stroma, or both, were eligible for inclusion.A total of 198 articles were identified. Data were extracted from 15 studies that matched the inclusion criteria. Collectively, these included studies confirmed the alterations occurring to the endometrial luminal epithelium during the PMT are similar to those seen during the EMT. Such similarities included alterations to the actin cytoskeleton remodeling of adherens junctions, integrin expression and epithelial-stromal communication. These were also some differences between these processes, such as the regulation of tight junctions and mucins, which need to be further researched.This review raised the prospect of shared and distinct mechanisms existing in PMT and EMT. Further investigation into similarities between the PMT in the endometrium and the EMT in tumorigenesis may provide new mechanistic insights into PMT and new targets for the management of implantation failure and infertility. There is a recent focus on examining changes in the endometrium that are required for successful implantation. The endometrium undergoes substantial remodeling throughout the menstrual cycle for the purpose of becoming adequately prepared or receptive to an implanting blastocyst. The most luminal portion of the endometrium, namely the functionalis, undergoes ovarian-steroid-hormone-mediated alterations across the average 28-day menstrual cycle to become receptive. The functionalis is comprised of the glandular epithelium (GE), luminal epithelium (LE) and stroma, and progesterone-mediated structural and functional alterations must occur to become optimally receptive during the “window of implantation” (WOI), which spans day 20–24 of the menstrual cycle. Such alterations include the increased secretory capacity and tortuosity of the GE, the acquisition of adhesive and loss of inhibitory cellular components within the LE, and stromal cell decidualization. Sequential exposure of estrogen and progesterone to the human endometrium is required for attainment of receptivity  is a similar process to PMT and describes the loss of apical-basolateral polarity in epithelial cells and the acquisition of a mesenchymal phenotype, typically associated with tumorigenesis. Specifically, EMT involves the disruption of cell-cell junctions, an acquisition of front-rear polarity, cytoskeletal and morphological alterations, enhanced motility, the down-regulation of epithelial and up-regulation of mesenchymal gene expression, and enhanced extracellular matrix degradation . These cTo the best of our knowledge, there have been no systematic reviews to date summarizing the events of the PMT in the human endometrium. Therefore, the aim of the present review was to evaluate the events of the PMT in women and compare these results with the key events described in the EMT.th of May 2020. The search terms used were “(plasma membrane* or cell membrane*) and transformation*” and “endometrium or endometrial.” No additional limits were used.The Medline (Ovid), Embase, and Web of Science databases were searched for articles published on or before the 27via direct or indirect effects and the function of decidualized stroma on PMT is just beginning to be realized. Inclusion criteria included: 1) articles discussing the PMT in the context of the endometrial epithelium, decidualized stroma, or both; 2) experimental designs; 3) studies including women as subjects. Exclusion criteria included: 1) an animal other than human without “human” in the title; 2) articles discussing gynecological cancer, alterations to the trophoblast, or early pregnancy changes without discussing the PMT; 3) conference abstracts, reviews or lack of available full text; 4) use of exclusively animal subjects. Sample size is indicated in Human studies assessing the PMT or its regulation in women, discussing either the endometrial epithelium, decidualized stroma, or both, were eligible for inclusion. Decidualized stroma was included as it can act on the LE Data were then extracted from the identified articles. Quality assessment was performed independently by two reviewers (SW and WZ). If there was disagreement, a third reviewer (ED) was consulted. The analysis followed the PRISMA statement for systematic reviews.A total of 198 articles were identified  2/3 complex  and a senior research fellowship (#550905) from the National Health and Medical Research Council (NHMRC) of Australia to ED.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The COVID-19 pandemic is leading to mental health problems due to disease experience, physical distancing, stigma and discrimination, and job losses in many of the settings hardest hit by the pandemic. Health care workers, patients with COVID-19 and other illnesses, children, women, youth, and the elderly are experiencing post-traumatic stress disorders, anxiety, depression, and insomnia. Virtual mental health services have been established in many settings and social media is being used to impart mental health education and communication resources. This rapid review highlights mental health services across countries hardest hit by the COVID-19 pandemic. More needs to be done to take these services to scale and ensure equity and efficiency. The impact of COVID-19 on mental health in sub-Saharan Africa could be immense, given the weak health care systems. Similar to the Ebola epidemic of 2014–2016, COVID-19 is expected to cause anxiety, depression and post-traumatic stress disorders. Uptake of mental health care services is generally low, and communities rely on social resources. Hence, efforts to control the disease transmission should be contextualized. Low digital literacy, low smartphone penetration and limited internet connection make online mental health services a limited option for service delivery. Safeguarding social and cultural resilience factors and coping mechanisms is critical in the sub-Saharan African context. Mass media is a feasible way of providing social resources. Community health workers can be trained quickly to provide mental health education, screening and counselling services. Toll-free mental health helplines can be used to provide services to health care workers and those needing customized care. Mental health and psychosocial support services need to be integrated into the pandemic response and coordinated nationally. It is critical for these services to continue during and after the epidemic. The COVID-19 (Coronavirus Disease of 2019) pandemic has impacted the lives of millions of people around the world and is likely to result in mental health problems among those with no previous mental illness as well as exacerbate the condition of those with pre-existing mental health problems/disorders. Mental health problems are likely to begin early and continue after the pandemic is over. Experience of the disease, breakdown of social support and stigma are possible causes of short-term mental health problems while factors such as economic losses can potentially cause long-term mental health issues.This paper summarizes the impact of COVID-19 on mental health in countries impacted by the pandemic and conceptualizes the implications for sub-Saharan Africa, with the aim of supporting time sensitive decisions that are required to impact policy and practice.®. A total of 21 scientific articles, 2 preprint articles and 6 country/continent specific reports and posts were included. For the second section which conceptualizes the implications for sub-Saharan Africa, the search words, Ebola AND mental health were used to explore all relevant journals in the Medline database. In total, 62 articles were screened, 3 manuscripts describing primary research and reviews from sub Saharan Africa were included. The rapid reviews were conducted by the two authors.A rapid review of scientific articles and reports published in English before or on May 17, 2020 was conducted. For the first section of the manuscript, search words included COVID-19, AND mental health, SARS- COV-2 AND mental health, 2019-nCOV AND mental health. All scientific articles were obtained from the Medline database, while country and continent specific reports and preprint articles were abstracted using googleSeveral recently published articles have documented the mental health impact of the COVID-19 pandemic on different target populations along with available and acceptable modalities for preventing and treating these problems/disorders.In the US 45% of adults have reported that they are experiencing anxiety and stress, these numbers are likely to increase as people continue to physically distance themselves as well as worry about getting sick from COVID-19.3Settings in China, the US and elsewhere have reported that Health Care Workers (HCW), first responders and other frontline workers, experience significant clinical depression, anxiety, post-traumatic stress and suicidal ideation.11A recent study conducted in China revealed 96.2% of COVID-19 inpatients experienced posttraumatic stress symptoms. These symptoms are likely to linger on for at least two years (as noted in studies conducted during the SARS outbreak) leading to reduced quality of life.13The impact of the current COVID-19 pandemic on the mental health of children has been noted in Spain, where strict lockdown measures led to heightened levels of stress and anxiety among young children.16Older adults are generally prone to mental health problems. In China approximately 23% of the older population (>55 years) have preexisting depression. Factors such as physical distancing and fear of death from COVID-19 are likely to result in stress and worsening of the mental health of seniors.18The disruption in the health care system from COVID-19 is impacting the care of other patients with chronic illnesses who need to visit health care facilities for chronic care. It is believed, the high levels of stress due to the inability to access timely care can cause mental illness.21In a nationwide survey of psychological disorders among Chinese people during the COVID-19 pandemic, it was noted that women were affected more than men while the youth age 18–30) had the highest COVID-19 peritraumatic distress index (CPDI).0 had the23Similar to China, high levels of stress were noted among adolescents and youth in the US, Canada, and Belgium.16Additionally, in China, stress levels were elevated among people with higher education levels due to increased self-awareness of their health, and migrant workers due to the uncertainty of income and exposure levels.1Among the workforce returning to work in China, it was noted that prevention measures such as handwashing, face masks and measures at the workplace that improved workplace hygiene resulted in fewer mental health problems/disorders (post-traumatic stress disorders (PTSD), anxiety, depression, stress and insomnia) among the workforce.26To combat COVID-19 mental health problems, several settings have employed digital treatment and prevention solutions to achieve the desired scale. In particular virtual mental health services have worked well in addressing scale and limiting the exposure of patients to COVID-19 at health facilities.5In China, several concerns regarding the current state of mental health services have been documented. While several services have been initiated to combat and address mental health issues, efficiency and equity in service provision may be lacking due to insufficient national coordination. Additionally, the efficacy of these services is not being evaluated, leaving behind the opportunity for continuous quality improvement. Online mental health services are helpful for those who have the resources and literacy to access them but the lack of alternative services is leaving behind a population that does not have access to the technology or literacy required to receive these services.28Another challenge that has been noted with regard to services in some settings is the lack of collaboration between health care facilities providing mental health services and community centers. Continuity of care for patients becomes a challenge once they are discharged from health care facilities. Inadequate numbers of mental health professionals such as psychologists and psychiatrists have led to front line health workers taking on the provision of mental health services. In China, the lack of policy and standardized training in mental health for non-mental health professionals may affect the quality of service provision.19In the US, existing mental health services are not sufficient to deal with the demand for services. Some of the challenges include a restriction on licensing and reimbursement of therapists who are trying to set up virtual services and the closure of community behavioral centers that are struggling to remain solvent.5Lessons learned from some of the countries with established services include the following: the strengthening of mental health services during the COVID-19 pandemic requires identifying high-risk groups early on and providing them with targeted interventions. An important feature of this is to conduct routine screening of mental health problems. Due to limited mental health care staff in many settings, this can be conducted by other front-line health workers. Additionally, the mental health of front-line health workers can be preserved by ensuring shorter workdays, provision of protective gear and adequate training in infection control. Stigma and discrimination of COVID-19 patients and front-line health workers need to be addressed by national authorities and influential leaders who should also take on the responsibility of ensuring the public receive accurate messaging during the course of the pandemic.9To date, very little has been documented about the impact of COVID-19 on mental health in sub-Saharan Africa. A global analysis of the literature on COVID-19 highlights the need for research from Africa which remains under researched.29In recent news the WHO warned that in the first year of the pandemic, Africa could see as many as 44 million people infected with COVID-19 and estimates up to 190 000 deaths among Africans from COVID-19 depending on the intervention measures taken to stop the spread.To better understand the impact of COVID-19 on mental health, we examined the literature on the recent Ebola epidemic in sub-Saharan Africa. The 2014–2016 West Africa Ebola virus outbreak triggered serious psychosocial consequences at both individual and community levels. Stress, grief, anxiety, depression and symptoms of PTSD were reported at the individual level while stigma, discrimination and interruption of social networks were observed at the community level.31In addition to some of the well-documented predictors of mental health problems, the inability of families to care for sick relatives coupled with the inability of family members to perform traditional and religious burial rituals for loved ones caused psychological distress.33The mental health consequences of the Ebola outbreak persisted after the end of the epidemic. In a survey carried out in Sierra Leone among a nationally representative sample of the population, 48% of participants reported at least one symptom of anxiety or depression and 76% reported PTSD symptoms a year into the epidemic.31Although Ebola is deadlier and less contagious than COVID-19, we think the mental health consequences arising from the COVID-19 pandemic in sub-Saharan Africa will have some similarity to the West Africa Ebola outbreak.Since March 2020, countries in Africa have implemented physical distancing measures, to reduce transmission of COVID-19, mainly closing educational institutions and banning mass gatherings. Twenty-two countries have also implemented a lockdown; 12 of which applied a national lockdown while the rest applied lockdown measures in affected areas.35The direct impact of the disease, particularly near-death experience during illness, isolation from loved ones during hospitalization which is a grim experience both for the family and the patients in most African communities, stress from news about high death rates among the very ill and the highly exposed , loss of loved ones or parents/guardians and stigma and discrimination among survivors and affected families. In particular, mental health problems will disproportionately affect frontline health care workers, COVID-19 survivors, families and children who have lost loved ones to the disease and those with pre-existing mental disordersEfforts to contain the spread of COVID-19 through restricting and limiting physical interactions may lead to limited access to social support structures, inadequate supply of food and medication, limited access to treatment for those with existing mental health problems as well as other chronic conditions, restricted access to faith-based institutions and leaders due to the ban on social gatherings, lack of access and support for those suffering from intimate partner violence or other forms of abuse. Most Sub-Saharan African communities are structured traditionally with a strong community and neighborhood focus and the main source of support and care for older people is family. Hence, in most communities, older people are protected from the calamities observed in care homes in high-income countries. However, the physical distancing directives might lead to loneliness in some settings.Uncertainty and stress resulting from loss of jobs and livelihoods.Three major factors are impacting the population and may lead to mental health problems:The stress of losing jobs and livelihoods can be overwhelming for many but this is worse for people of low socioeconomic status including those working in the informal sector. Although several countries have put some measures in place to mitigate the economic difficulties, the financial packages have been minimal, while those working in informal businesses have not been eligible for any of the government schemes.36The lockdown and the physical distancing measures are being debated and questioned by many about their impact on the informal economy which provides a livelihood for 60% of men, and nearly 75% of women and the majority of city dwellers who rely on this economy for their day to day needs.39Mental health services will need to be prioritized during the COVID-19 pandemic in sub-Saharan Africa. However, improving access and utilization of these needs to be thought through given some of the contextual factors. The utilization of mental health services does not happen frequently because many people in sub-Saharan Africa only engage with the health care system for services when all other social resources and self-help methods fail or if symptoms get very severe.Online and digital platforms used in high income settings are a limited option for mental health education and counselling services in sub-Saharan Africa mostly due to low smartphone penetration and internet access. The internet usage gap varies among countries (6.3% Chad-87% in Kenya).In most African countries, ministries of health and other responsible government institutions conduct regular press releases on COVID-19 and disseminate key information to the public, working in partnership with local radio and television stations. To make the services and social resources that are lacking during the lockdown accessible, we recommend employing mass media for communication of self-help measures that are likely to reduce stress. Mass media can also be used to communicate survivor experiences. Although there are few examples of people discussing their recovery experience, (eg Oluwaseun Osowobi on BBC and testimonies of patients in Burkina Faso) a lot more can be done to prepare and help others cope better as well as provide education on stigma and discrimination.We foresee greater challenges in the provision of mental health services compared to those documented in other settings. Lack of national coordination, shortage of mental health care staff etc., are issues that need to be addressed. Guidelines available for emergency situationsMany sub-Saharan African countries rely heavily on community health workers (CHW)/village health workers to deliver services.To augment this, toll-free mental health helplines available in some countries in Sub-Saharan Africa can be scaled up inexpensively to provide more in-depth and anonymous counselling for select segments of the population such as health care workers and people experiencing suicidal ideation. Several tiers of helplines can be established depending on the complexity of cases and the need for services.In conclusion, addressing the mental health impact of COVID-19 in sub-Saharan Africa needs to be prioritized. National coordination in service provision is key. Both mental health and psychosocial support need to be integrated into the pandemic response. Treatment efforts should be coupled with a response to support the psychosocial needs of patients and their families. Training of facility and community-based health workers needs to be coordinated while guidelines for mental health support during outbreaks need to be made available and disseminated to all providing services. Lockdown and physical distancing measures should be contextualized while cultural attributes and resources that provide social support and resilience should be tapped. There is a critical need for strong communication and community engagement to combat misinformation and fear-related behaviors. Psychosocial support including other interventions must continue during and after the pandemic targeting high-risk groups like survivors, bereaved family members, children who lost their parents, health care workers, burial workers and other first-line responders.