The filament extruded from the composite material was very elastic but had good features to be used for 3D printing applications. It was technically demonstrated that the 3D thermal deposition of composite filament with 35% BaTiO3 was a convenient process for achieving tailored architectures to be used as devices with functionality as piezoelectric sensors. Finally, the functionality of such 3D printable flexible piezoelectric devices with energy harvesting features was demonstrated, which can be used in various biomedical devices (as wearable electronics or intelligent prosthesis), generating enough energy to make such devices completely autonomous only by exploiting body movements at variable low frequencies.The purpose of this work was to obtain an elastic composite material from polymer powders (polyurethane and polypropylene) with the addition of BaTiO The application segments for piezoelectric energy harvesters based on ferroelectrics have dramatically expanded during the past 5 years. For several applications, ferroelectric micro- and nano-crystals with a defined one- (1D), two- (2D), and three-dimensional (3D) shape are of great scientific and technological interest because of their spontaneous polarization as well as their shape- and size-dependent properties. The subject of moldable piezoelectric sensors with energy harvesting features is very actual; research in this area extensively reports mainly thermo-rigid devices based on epoxy, PVDF, or other composite structures, mainly with PZT powders, such as [The past 10 years have witnessed enormous interest in the efficient capture of environmental energy through the development of energy-harvesting devices that transform mechanical energy into electricity and greatly reduce our dependence on fossil fuels and COensional D shape a such as ,12,13.Regarding the analysis of costs vs. benefits of adapted technology and the life cycle of such devices, we note that the basic literature largely supports piezoelectric energy as being applicable in special-purpose niches with high market impact, such as wireless sensor networks (IoT). The harvesting of piezoelectric energy must be interpreted through direct indicators: the power required for the real purpose and the surplus power, which is unused and stored over time. A decision model for analyzing costs vs. benefits would include aspects such as power consumption (both active and stored), physical size/energy density requirements, storage battery technology, and working circuit technology. For example, the CC2630 Zigbee TI controller uses 1.0 µA in passive mode, whereas the CC2538 uses between 1.3 and 600 µA. In “sleep mode”, consumption is 0.1 vs. 0.4 µA.The overall cost is also given by the relevant and precise characterization of the physical conditions that contribute to energy harvesting: the occurrence of dynamic force, vibration frequency, temperature range over time, etc. Depending on the complexity of the equipment, evaluations are made of potential improvements in energy efficiency, price, normalized price, and lifetime. As for the lifetime, the energy harvesting technologies are guaranteed for a minimum of 10 years, being made on the basis of robust materials, a sufficient element to make them very competitive on the renewable energy market, and for the technological design according to the forecasts of microelectronic applications.From the point of view of technological feasibility, the advantages of piezoelectric generators are mentioned as being simple structures, easy to manufacture on a large scale (mass production), on the one hand, and easy to implement in electronic systems of the ‘energy harvesting’ type.The new trend is defined by flexible energy-harvesting devices, which are yet more difficult to manufacture. Some achievements are presented as ,26,27,283, along with some optical and structural properties.The 3D architectural design of printable piezoelectric components involved a good knowledge of the adsorption of thermoplastic polymers on the surface of ceramic nanoparticles. In the stages prior to the realization of the 3D printable flexible piezoelectric composites with energy harvesting features, the following results were reported by the authors ,33,34 asOur study presents an example of good practice under the circumstances that it is obvious that by an extruding process pellets from thermoplastic composites may be manufactured, even if the inorganic powder content goes towards 80–90%, but it is also well known that the manufacture of rigorous filament in terms of diameter tolerance and reasonable length from thermoplastic composites with more than 10–15% inorganic powders is extremely difficult, mainly due to the fragility of the filament, which in many cases breaks itself under the reeling operation. That is why a tailored compounding of thermoplastic olefin with thermoplastic polyurethane was used. On the other hand, at higher powder contents, the filament homogeneity can suffer important changes under cooling operations due to dilatation, exfoliation, or delamination processes. Another major difficulty noticed by many practitioners refers to the thermal printer adaptation for such composites with a high content of inorganic powders, which makes the actual commercial printers useless for such applications, mainly when higher printing precision  is compulsory.The innovation presented by the present study includes a clear demonstration of the conditions imposed on such composites to become 3D printable, i.e., starting from the compounding and filamentation stage, through the 3D thermal deposition of composite filament with no clogging of the nozzle, no problems with multilayer deposition, and no 3D printing defects, to generating structures of rectangular network type with micro-meter precision, along with innovative tests to demonstrate their use as piezoelectric sensors within a dedicated signal processing circuit and the use of virtual instruments to assess their energy harvesting features.3 powder of a maximum 2 micron dimension from Sigma Aldrich . The present study completes and particularizes the previous research presented in [3 powder content up to 35% in order to emphasize their piezoelectric features.In order to obtain the composite structures, the following raw materials were used: a thermoplastic olefin TPO , a thermoplastic polyurethane TPU , and BaTiOented in  and refe3 powder were homogenized by mixing for one hour in a cylindrical mixer with a 1.3 L capacity TURBULA T2F type with a rubber ring holding device, and the rotation speed was 40 rpm. In this way, we sought to obtain a uniform distribution of the components of the mixtures throughout the structure without using specific additives or adhesives for compatibility. Processing conditions involved a rotation speed (in counter-rotation) of the extruder of 95 rpm and a feed speed from the feed hopper of 450 rpm.The polymers as powders (TPU and TPO—herein polypropylene) and the BaTiO3, a maximum material pressure of 2200 bar, and a real injection capacity minimum of 500 mm. The interface of the injection machine for obtaining the composite materials and the temperature regime on the areas of the cylinders of the injection machine are briefly presented in The injection of composite was performed on a Dr. Boy 35A injection machine  with the following characteristics: a screw diameter of 28 mm, an L/D ratio of 18.6 mm, a calculated injection capacity of 58.5 cm-The photoluminescence (PL) spectra of composites were recorded with a Fluorolog-3 spectrophotometer, FL3-2.2.1 model, from Horiba Jobin Yvon , with some expertise related in .-SEM optical scanning microscopy was performed with a field emission and focused ion beam scanning electron microscope (SEM) model Tescan Lyra III XMU .-The AFM analysis was performed with a WIKO NT 1100 type interferometric microscope in accordance with ISO 10109-7:2001 .-Dielectric features were determined by using the Broadband Dielectric Spectrometer (Novocontrol GMBH), which encompasses an Alpha frequency response analyzer and Quattro temperature controller with tailored measurement cells. The manufactured samples were sandwiched between two copper electrodes of 20 mm diameter and placed inside the temperature-controlled cell .-The piezoelectric features were measured using an Aixact TF Analyzer 2000-Electric Hysteresis Curve Lift System (static and dynamic hysteresis); the voltage that can be applied to the sample is +/− 100 V to +/− 10 kV). The device measures bulk samples (maximum diameter of 20 mm and a maximum thickness of 1.8 mm). The hysteresis curves were raised starting with a frequency of 0.1 Hz at an electric voltage 20% lower than the breakdown voltage of the samples. Simultaneously, the displacement of the sample can be measured with a laser interferometry system.-−2 mbar.TG/DSC thermal analysis, performed on a STA 449 F3 Jupiter TG-DSC simultaneous thermal analyzer, Netzsch , working in the temperature range up to 1550 °C, in an inert, oxidizing, reducing, static, or dynamic working atmosphere. The device is provided with a vacuum system with a maximum of 10The characterization of the composite materials was carried out with the use of the following equipment:vH corresponds to the photoluminescence intensity when the polarizer is positioned vertically for excitation and horizontally for emission in the spectrophotometer; G = IHV/IHH, where IHV corresponds to the light intensity measured when the polarizer is positioned horizontally for excitation and the polarizer is positioned vertically for emission.The photoluminescence spectrum of thermoplastic composites exhibits a maximum at 462 nm when the excitation wavelength used to record the photoluminescence spectrum is 350 nm. Anisotropy (r) and bond angle (ϕ) of macromolecular compounds, adsorbed on the surface of inorganic particles, can be calculated using anisotropic photoluminescence with the following formulas:3 nanoparticles having concentrations of 12 wt.%, 25 wt.%, and 35 wt.%, respectively, are presented in 3 as quenching agent of polymeric matrix’s PL. This result is in agreement with our previous paper [VV, IVH, IHV, and IVV values experimentally obtained, which are presented in 3 are equal to 0.0862 and 46.30; (iii) TPU:TPO 2:1 + 25% BaTiO3 equal to 0.078 and 47.10; and (iv) TPU:TPO 2:1 + 35% BaTiO3 equal to 0.029 and 51.80, respectively. In regard to the anisotropy, the composite with 12% BaTiO3 presents the maximum value and is explained by a more homogenous dispersion of particles with different spatial orientations, which is a phenomenon expected for homogenous dispersions with low quantities of particles. In regard to the bond angle, the maximum value is reached by the composite with 35% BaTiO3, which is explained by the composite architecture and will be further analyzed by SEM optical scanning microscopy. The value of r is less than 0.4, a fact that indicates that the excitation and emission transition dipoles are not aligned, which explains the complex dielectric polarization presented further in the paper. This aspect originates in the exchange reaction of the repeating units of the TPU-type polymer with BaTiO3 [The photoluminescence spectra in polarized light of composites with BaTiOus paper . Consideh BaTiO3  because 3 particles was about 1 μm, SEM structural analyses were performed to highlight the degree of homogeneity of the obtained materials. These analyses were performed on the field emission source and focused ion beam scanning electron microscope. The average dimension of BaTiO3 powder at a higher powder content.It can be generally seen that the filler is well homogenized within the polymer structure with a uniform dispersion, 3, which is considered more relevant due to the higher content of powder, and the resulted roughness was below 100 nm. The roughness of such composites may be relevant in the case of producing filaments for 3D printing purposes, and the obtained value is in line with the requirements for such applications.Basically, the experimental models made of polymer composite materials are very difficult to withstand atomic force microscopy tests because, for the AFM microscopy tests, a surface with nanometric roughness (preferably approx. 50 nm) is required. The roughness was determined as the average value between three measurements performed on the same sample in its central area at a focal distance of 90 μm. Roughness was obtained in the range of 75–450 nm, which gives some minor errors under the circumstances presented as above. In 3), the effect appears more blurred, but there is also a subjective cause given by the optical contract of such powders. These preliminary conclusions from the AFM analysis can be clearly correlated with those from the SEM analysis.A quasi-uniform distribution of the particles on the surface of the composite material can be observed as a whole, eventually depending on the size of the particle and its concentration. In the case of inorganic powders  independently measures the heat flow rates between a sample and a reference subjected to the same temperature program . The difference in heat flow between the sample and the reference, which are heated (or cooled) over a certain temperature range, is then determined, and this difference is plotted as a function of temperature. The direction of the thermal flow towards the DSC sensor is well defined and reproducible . The resFor such composite material, in addition to glass transition processes and chemical oxidation processes, there is also a first-order phase transformation process (melting) due to the TPO (PP) melting process. The maximum melting temperature is around 170 °C.The development of flexible and elastic piezoelectric energy capture devices based on customized composite elastomers and 3D printing technology involved modeling by fused deposition of composite materials in the form of filaments. The preliminary tests for making specific filaments for 3D printing with a diameter of 1.75 mm were carried out on a small laboratory extruder  from ext3 resulting from the extrusion operation was elastic, mainly due to the innovative addition of TPO, even close to the elasticity of rubber, but it provided good features to be used for 3D printing applications as well and presented a reasonable variation in a maximum diameter of 10%. The optimal temperatures were around 190 °C with a pulling speed of 15 cm/min. The filament was homogenous, with a smooth surface and no mechanical defects, and had reasonable winding features  with two windings was used , supplied with a constant voltage of 24 V dc from the direct voltage source (5) and also with alternating voltage from the autotransformer (6). The vibration force is proportional to the currents absorbed by the two windings, according to Equation (1):din. When the position of the cursor of the autotransformer is changed, the increase in the alternating voltage applied to the device (2) is achieved, and the mobile part (on which the sensor (1) is placed) will start to vibrate, and thus a signal will be generated at the two terminals of the self-adhesive copper strips of the sensor. Further, this signal is used to charge a capacitor with the role of an energy harvester, and if a resistor R is connected to the output of the sensor, the effective value U of the voltage of the oscillations generated by the sensor can be measured, with the power value to be determined with Equation (2):The vibration frequency was up to 50 Hz, and their amplitude was proportional to FIn our case, a very common electronic processing module, as presented in The output from the sensor is applied to a rectifier bridge made with 4 Shottky diodes of type 1N5818 in order to achieve a continuous charge process only and avoid the reverse bias effect.u(t) on the capacitor is given by Equation (3), where U is the voltage applied to the capacitor resulting from the rectification and R is the equivalent load resistance of the capacitor.The time variation of the voltage E accumulated in the capacitor to which the voltage U is applied is given by Equation (4).The maximum energy The analog signals when increasing the voltage of the vibration device, i.e., the vibration amplitude level increases, are presented in That is why intelligent signal processing was embedded by using a virtual instrument (VI) developed under the LabVIEW graphical programming environment , brieflyY-axis vs. the X-axis, which will show the effective time.Block 3 is the actual signal acquisition block and has been configured for the acquisition of analog signals. Because we are acquiring signals on several channels, “Multiple Channels” will be selected. Block (4) is a timer used to synchronize the acquisition with the display. After acquiring the signals, these vectors in which the values are stored are displayed value by value on display 5, after which these values are interpolated. These values will be presented on the SubVI (6) is used to close the “task” and is opened by block (2). Blocks (2) and (6) will always be used together. The SubVI (7) will clear all values stored in the 1D-type variables to prepare the VI for the next acquisition. The SubVI (8) will display an error message if errors occur. A sample count of 100 has been set, so we will store the values in a 1D vector variable.The front panel of the signal acquisition instrument was designed to simulate different functional regimes of the energy harvester, i.e., the resistor value, the time, the range (limits) of the input voltage, and the number of signal samples to be processed vs. time.Two signals are acquired, one directly from the sensor on channel A1 (the waveform is red) and the signal from the capacitors on channel A0 (the waveform is white), the latter being displayed separately for an analysis vs. charging time and charging regime.The first experiments are performed with the sensor without a preliminary activation with an electric field.The signals from the sensor output and the charging voltage of the capacitor are shown in In As seen in The following experiments are made with the sensor after the activation by the electric field. The sensor was activated by applying to its surfaces a continuous voltage of 31.6 V for 72 h to ensure saturation of the hysteresis effect.Here also, the charging of the capacitor starts after the vibrations reach a minimum level, but much earlier compared to a non-activated sensor, i.e., after a voltage of min. 85 V is applied . In thisAt this point in the studies, the feature of ‘energy harvesting’ mode was demonstrated. By preliminary activating the sensor in the electric field, the value of the electric signal generated by the sensor increases, the efficiency of the sensor is higher, and the charging of the capacitor is faster.An interesting aspect occurs when comparing the non-activated and activated sensors when the vibrations decrease.In the case of a non-activated sensor, when the applied voltage goes below 140 V, the sensor becomes passive, and the capacitor is not charged any more. However, in the case of an activated sensor, the charging of the capacitor continues even if the voltage is decreased to 70 V, until saturation  when th, where tThe overall picture based on the actual literature shows that many researchers are carrying out research with the aim of testing piezoelectricity as the main source for energy harvesting, and the applications are very innovative, especially in the case of flexible piezoelectric systems.3 until 35% were manufactured and interdisciplinary tested, and it was proved that the filler is well homogenized within the polymer structure with a uniform dispersion. For such composite material, in addition to glass transition processes and chemical oxidation processes, there is also a first-order phase transformation process—melting, due to the TPO (PP) melting process.Composite materials from polymer powders (TPU and TPO—herein polypropylene) with the addition of BaTiO3 dramatically increases the relative dielectric permittivity, from about 3 for pure polymers to about 10 for an addition of 12% BaTiO3, and finally to about 30 for an addition of 35% BaTiO3. In regard to the dielectric loss, at lower frequencies the effect of interfacial polarization is detrimental, with a very significant increase for an addition of 35% BaTiO3. The piezoelectric characteristics of the composite with 35% BaTiO3, without preliminary activation under a tailored electric field, are remarkable, especially at lower frequencies.The addition of BaTiO3 was very elastic, close to the elasticity of rubber, but it provided good features to be used for 3D printing applications and presented a variation in a maximum diameter of 10%.The filament extruded from the composite material with 35% BaTiOThe importance and degree of novelty of our study consist in the demonstration of the operation in energy harvesting mode of the new concept of sensors made by 3D printing technology, made in the form of thermoplastic composites deposited in various forms; here, the testing was performed on a structure of rectangular network type, acting as a piezoelectric sensor in a dedicated signal processing circuit.3 was a convenient process with no clogging of the nozzle, no problems with multilayer deposition, and no 3D printing defects.It was technically demonstrated that the 3D thermal deposition of composite filament with 35% BaTiO-3 has an immediate and proportional response to periodic mechanical excitation.The electrically activated device has superior performance in terms of the generated electrical signal; the device with 35% BaTiO-3 and a quasi-4D effect with frequency, responds better at lower frequencies to the variation of mechanical oscillations and achieves a quasi-uniform charging of the capacitor of the energy harvesting circuit, even if the mechanical oscillations become reduced in intensity.The device, with a higher concentration of BaTiO-3, the lower the minimum response threshold at low levels of mechanical oscillations, with an induced mechanical hysteresis effect when the mechanical oscillations decrease.The higher the concentration of BaTiOFor the development and integration of the signal processing circuits and the demonstration of the functionality of the energy harvesting features of 3D printed devices, an innovative test stand was developed and is assisted by a virtual instrument to produce and analyze the tailored vibrations to activate devices with functionality as piezoelectric sensors. As brief conclusions upon the electronic tests performed with non-activated and electrically activated devices:Such flexible piezoelectric systems can be used in various biomedical devices (as wearable electronics or intelligent prosthesis), generating enough energy to make such devices completely autonomous only by exploiting body movements at variable low frequencies.


Numerical simulations demonstrate that the initial penetration holes on the steel targets are enlarged under the detonation-like effects of PTFE/Al reactive materials, and the simulated perforation sizes are in good agreement with the experimental results.To study the penetration and cratering effect of reactive material composite jets, a series of experiments are carried out for the shaped charge (SC) with different composite liners damaging steel targets. The inner layer of composite liners is metal and the outer one is a polytetrafluoroethylene/aluminum (PTFE/Al) reactive material. Copper (Cu), titanium (Ti) and Al inner liners are used in this paper. The reactive material liner is composed of 73.5 wt.% PTFE and 26.5 wt.% Al powder through mass-matched ratios. Reactive material composite liners are prepared through machining, cold pressing and a sintering process. The SC mainly consists of a case, a composite liner, high-energy explosive and an initiator. The steel target is steel 45#, with a thickness of 66 mm. A standoff of 1.0 CD (charge diameter) is selected to conduct the penetration experiments. The experimental results show that when the inner layer of the composite liner is composed of Ti and Al, the hole diameters on the steel target formed by the reactive material composite jet are significantly larger than that of the inner Cu liner. By introducing the initiation delay time ( Reactive materials have been one of the research hotspots in the field of new material and engineering applications in recent years. Commonly used reactive materials mainly include the mixture of a polymer powder matrix (such as PTFE) and certain amounts of energetic metal powders . Thus far, the formulation system of reactive materials mainly includes PTFE/Al, PTFE/Al/W (tungsten), PTFE/Ti/W, etc. ,2,3. TheGenerally, reactive liners prepared using a class of reactive materials can be applied to the SC (shaped charge). Under the action of the SC, the high-velocity reactive jet formed by the reactive liner can not only penetrate the target with its kinetic energy, but also enlarge the initial perforation or enhance the after-effect through the release of chemical energy. Due to their excellent performance, shaped charges with reactive liners have been studied extensively. Early in 2001, Baker  verifiedTo improve the penetration depth of the SC with the class of reactive materials, more attention has been paid to the composite liner formed due to the reactive material liner and the metal liner. Lee  fabricatIn this paper, the penetration and cratering effects of the SC with reactive material composite liners against steel targets are investigated through static experiments and numerical simulations. Firstly, samples of reactive material–Cu liners, reactive material–Ti liners and reactive material–Al liners are fabricated. On this basis, penetration experiments of the SC with reactive material composite liners against steel targets are carried out. Then, the formation characteristics of the reactive material composite jets before impacting the target are investigated, including the formation morphology and performance parameters of the composite jets and the pressure and temperature distribution of the reactive materials. Finally, the combined cratering effects of the kinetic energy penetration and detonation-like reaction of the reactive material composite jets against steel targets are simulated and compared with the experimental results.(1)The first step is processing the metal liner. The metal bar is processed using mechanical equipment and the shape of the metal liner is processed according to the drawing.(2)The second step is preparing the PTFE/Al reactive materials. According to the formula design of the reactive materials, the PTFE powder and Al powder are crushed separately, and then mixed evenly with a special mixer. Generally, evenly mixed PTFE/Al compounds can be obtained through mixing for 30 min.(3)The third step is cold pressing the composite liner. First, a certain amount of uniformly mixed PTFE/Al compounds is weighed out, poured into a special mold and the formed into the liner shape at a pressure of 10 MPa. Then, the metal liner is placed inside the prepressed PTFE/Al liner. At this time, a pressure of 300 MPa is used to press for 10 min. Before the sintering process, the cold-pressed composite liner is placed in a room temperature environment for several hours to remove residual stress in the liner.(4)The fourth step is sintering the cold-pressed composite liner. The cold-pressed composite liner can be placed into a sintering furnace filled with nitrogen for high-temperature sintering. The maximum sintering temperature is 380 °C, and the temperature is kept for 4 h. Then, the temperature is reduced to 315 °C at 0.5 °C/min and maintained for 4 h. The sintered composite liner sample can then be cooled to room temperature while still in the furnace.Composite liners consist of an inner layer metal liner and an outer layer PTFE/Al reactive material liner. The typical preparatory process of composite liners is shown in 3. To study the effect of the inner metal liner material on the crater-expanding behavior of the steel target under the effect of the SC with the composite liner, three composite liners, reactive material–Cu liner, reactive material–Ti liner and reactive material–Al liner, were selected to carry out the penetration experiments. The wall thickness of the three types of composite liners was consistent to ensure the same mass of the main charge. The wall thickness of the metal liner t1 was 1 mm, and the PTFE/Al liner thickness t2 was 5 mm. The caliber diameter D and cone angle α of the composite liners were 66 mm and 60°, respectively.The schematic structure and samples of the reactive material composite liners are shown in H = 66 mm). The standoff refers to the distance from the bottom of the SC to the surface of the target. A hollow Al cylinder with an outer diameter of 76 mm and an inner diameter of 64 mm was selected for the standoff. The steel target was steel 45# with a diameter of 120 mm and a height of 66 mm.The schematic structure of the SC with the reactive material composite liners is shown in The typical damage effects of the three kinds of SCs with the reactive material composite liners against the steel targets are shown in D0 and De are the diameters of the petal bulge at the front and the back of the target, respectively. Dm refers to the minimum diameter of the penetration channel, which is an important index parameter of jet perforation capabilities [Dm were 0.32 CD and 0.41 CD, which was approximately 30.4% and 10.9% lower than that of the reactive material–Al jet, respectively.According to experimental results, the through-hole shape and representative crater parameters of the typical penetrated steel targets are shown in bilities . The craτ) was introduced by some domestic and foreign scholars [t < τ. The shock equation of state (EOS) and Johnson–Cook constitutive model were used to describe the formation and penetration behavior of the reactive material jets. Meanwhile, the corresponding parameters of the PTFE/Al reactive materials were obtained based on the separated Hopkinson shock and quasistatic compression experiments; the main material parameters are listed in ρ is the density of the material, a, b, n, C, m and S are the material constants, Tm and Troom are the melting temperature and room temperature, respectively, Γ is the Gruneisen coefficient and c0 is the acoustic sound speed of the material.Reactive material liners can form a high-velocity jet under the detonation of the SC, and its penetration and deflagration coupling effect on the target is very complex. At present, there is no material model mature enough for the numerical simulation of the whole process of the jet forming, penetration and deflagration coupling of the SC with reactive material liners. For this reason, the reaction delay time of reactive materials , the jet velocity values of vj,5-Ti and vj,5-Al increased by 18.2% and 25.1%, respectively. In addition, by comparing the velocity of the reactive material–Ti jet with that of the reactive material–Al jet, vj,1-Al was approximately 7.2% higher than vj,1-Ti, while vj,5-Al was only approximately 5.8% higher than vj,5-Ti. This phenomenon showed that the tip velocity of the reactive material–Al jet was greatly affected by the standoff. Specifically, when the standoff was 1.0 CD, the vj,5-Al decreased by approximately 5.7% compared with vj,1-Al.According to the simulation results, the performance parameters of the three kinds of reactive material composite jets are listed in dm,j-Cu) was the smallest, and the diameter of the reactive material–Al jet  was the largest. The value of dm,j-Al was 10 mm, which was approximately 85.2% and 25% larger than dm,j-Cu and dm,j-Ti, respectively. In terms of the length of the composite jet, the total length of the three composite jets was almost the same. However, the length of the metal jet would drop off gradually with the decrease in the material density of the inner liner. That is, the value of Lj,m-Al was the smallest, which was approximately 9.9% and 5.8% smaller than Lj,m-Cu and Lj,m-Ti, respectively.As to the diameter of the composite jet before impacting the target, the diameter of the reactive material–Cu jet (t = 14 µs), a high-pressure zone was produced at the interface between the metal jet and the slug. As the jet head continued to go forward, the high-pressure zone gradually moved to the interface between the two materials. The pressure–time curves of the gauges in the reactive material liner are shown in t = 7µs, the pressure reached a peak at gauge #9, followed by gauge points 11, 13, 15 and 17. As the material of the metal liner changed from Cu to Ti and Al, the instantaneous peak pressure at the gauge points decreased from 75.3 GPa to 65.9 GPa and 56.3 GPa. At t = 13µs, the second pressure peak appeared at gauges #9 and #11. However, compared with the first pressure peak, the second peak was significantly lower. Combining Under the effect of the high-pressure detonation wave, the reactive material liner was be crushed and gradually formed the main part of the slug. The detonation wave propagation and the plastic deformation of the reactive material liner would cause the temperature rise effect . When th2F4 could the Al particles experience a violent detonation-like reaction with the released oxidant [Meanwhile,  oxidant ,31. As st < τ. The time interval between the initiation of the SC and the violent detonation-like reaction is generally called the reaction delay time, and the chemical reaction behavior can be ignored in the time range [τ was not only affected by the particle size and preparation process of the PTFE/Al liner, but also related to the impact pressure and explosive type [τ could be obtained through relevant experiments. In this paper, the corresponding parameters of the PTFE/Al liner were consistent with that of the reference [τ was approximately 166.5 μs.These phenomena further verified that the chemical reaction of the PTFE/Al liner material was negligible when time me range . In addiive type . The timeference , and thet ≤ τ, the penetration processes of the three kinds of composite jets due to their kinetic energy are shown in For time τ, most of reactive materials were blocked outside the entrance of the penetration hole. This was mainly due to the smaller diameter and lower velocity of the reactive material–Cu jet head  formed on the steel targets and the errors between the numerical and experimental results are listed in Under the three conditions, the penetration results of the steel targets through the only kinetic energy of the reactive material composite jets are shown in t ≥ τ, and the behavior can be described through the EOS of the JWL. The corresponding parameters of the reactive material detonation-like effects are listed in According to the references ,37, it iτ, as shown in Based on the discussion above, the penetration process of the reactive material composite liner shaped charge against the steel target was divided into two stages. The first stage was the process of the composite jet forming and penetrating the steel target. The second stage was the violent detonation-like reaction of the PTFE/Al reactive materials. At the second stage, it was necessary to save the effective mesh data of the composite jets and steel targets in a two-dimensional Euler–Lagrange domain at time D0,d, Dm,d and De,d) and the errors between the numerical and experimental results are listed in 3, AlF2 and AlF [The combined perforation effects of the reactive material composite jets against the steel targets after the detonation-like reaction of the reactive materials are shown in  and AlF ,14,17, w(a)The experimental results showed that when the thickness of the steel target was 1.0 CD, the penetration hole diameters of the reactive material–Al jet and reactive material–Ti jet were significantly larger than that of the reactive material–Cu jet. In particular, the entrance hole and minimum diameters formed due to the reactive material -Cu jet were approximately 26.8% and 30.4% smaller than that of the reactive material–Al jet.(b)For the structure of the composite liner shaped charges, the inner metal liner material had a little influence on the jet morphology. However, it significantly affected the tip velocity and head diameter of the reactive material composite jet. As the material of the metal liner changed from Cu to Ti and Al, the jet tip velocity and diameter increased gradually, which was an important reason for the larger hole diameter formed by the reactive material–Al jet.(c)The hole diameters of the three kinds of reactive material composite jets obtained through numerical simulations were in good agreement with the corresponding experimental results. This proved that the simulation method combining the inert assumption during the jet formation and penetration and the JWL equation describing the detonation-like reaction behavior of the PTFE/Al reactive materials was reliable.In this paper, reactive material composite liners were fabricated with machining, cold pressing and sintering processes. On this basis, the perforation behavior of reactive material composite liners shaped charges against steel targets were investigated using numerical simulations and static experiments. Several conclusions were presented as follows:


Silicon-on-insulator (SOI) wafers are crucial raw materials in the manufacturing process of microelectromechanical systems (MEMS). Residual stresses generated inside the wafers during the fabrication process can seriously affect the performance, reliability, and yield of MEMS devices. In this paper, a low-cost method based on mechanical modeling is proposed to characterize the residual stresses in SOI wafers in order to calculate the residual stress values based on the deformation of the beams. Based on this method, the residual strain of the MEMS beam, and thus the residual stress in the SOI wafer, were experimentally determined. The results were also compared with the residual stress results calculated from the deflection of the rotating beam to demonstrate the validity of the results obtained by this method. This method provides valuable theoretical reference and data support for the design and optimization of devices based on SOI-MEMS technology. It provides a lower-cost solution for the residual stress measurement technique, making it available for a wide range of applications. The residual stress in silicon-on-insulator (SOI) wafers has been a significant concern impacting the reliability of microsystem devices and the performance of MEMS devices, potentially leading to device failure . TherefoResidual stress testing methods can be broadly categorized as either destructive or non-destructive. Destructive methods release stress by mechanically separating or splitting the components on the surface. Recently, optical techniques ,11,12,13Non-destructive measurement methods for residual stress have made significant progress in recent years. These include radiation methods ,19, nanoTo overcome these challenges, this study introduces a non-contact method to characterize the residual stress in SOI-MEMS devices. The residual strain measurement method calculates the residual stress value by measuring the residual strain and applying theoretical calculations based on mechanical equations. As a non-destructive measurement method, it has received much attention in recent years due to its scalability. The proposed method in this paper utilizes theoretical calculations and bending moment measurements to accurately assess the residual stress. By examining the underlying mechanisms of residual stress generation in SOI wafers, mechanical deflection models for MEMS cantilever beams and fixed beams are developed. Experimental testing is conducted to validate the effectiveness and feasibility of this method for characterizing residual stress in SOI wafers.Silicon direct bonding (SDB) technology is widely used in the preparation of SOI wafers. The process involved in creating bonded SOI wafers is illustrated in The SDB technology offers several advantages in the preparation of SOI wafers. It allows for the creation of a thin and defect-free buried oxide layer, which is crucial for the performance of SOI devices. The bonding process enables the integration of different materials and the formation of high-quality interfaces. Additionally, the ability to control the thickness of the device layer through polishing allows for customization according to specific device requirements.2 layer on the surface of a polished silicon wafer, induces the generation of residual stresses within the layer. These residual stresses can be categorized into thermal stress and intrinsic stress [The process of thermal oxidation, which involves growing a SiOc stress ,23. Therc stress , as depic stress . The lat2 layer on the polished silicon wafer surface, a significant amount of oxygen atoms is introduced into the silicon surface, leading to volume expansion. However, since the grown SiO2 layer is bonded to the substrate, its perimeter cannot freely expand. Considering that the thickness of the substrate is much larger than that of the SiO2 layer, it can be assumed that the radial expansion of the SiO2 layer is nearly zero. As a result, the SiO2 layer can only expand in the direction perpendicular to the substrate surface, resulting in the presence of intrinsic compressive stress distributed in a gradient along the thickness direction of the SiO2 layer.During the thermal growth of the SiO2 layer experiences a uniformly distributed thermal mismatch stress. This is because the thermal expansion coefficient of SiO2 is lower than that of silicon. After the growth of the SiO2 layer, the residual stress within the layer is a combination of the thermal mismatch stress and the intrinsic stress. At this point, the SiO2 layer and the silicon substrate reach equilibrium, and tensile stress is present in the substrate. The distribution of residual stress in the layer and substrate is illustrated in During the subsequent cooling process, the SiO2 layer experiences compressive stress from the underlying silicon and the device layer, while the underlying silicon and the device layer undergo tensile stress from the SiO2 layer. The residual stress in the SiO2 layer and the device layer exhibits a gradient along the thickness direction. On the other hand, since the thickness of the underlying silicon is considerably larger than the thickness of the other two layers, the residual stress in the underlying silicon can be approximated as uniformly distributed.In the prepared SOI wafer, the distribution of residual stress within the wafer is depicted in 2 layers disrupts the original stress balance mechanism within the SOI structure, leading to the development of residual stress. This residual stress induces bending deformation in the MEMS devices, subsequently impacting their performance and reliability. When processing a cantilever beam using the SOI wafer, initially, before the release of the substrate layer and the SiO2 layer in the three-layer SOI structure, the cantilever beam is in an ideal state of stress balance due to the mutual constraint exerted by the layers of the SOI wafer, as depicted in 0 and σ1, as illustrated in In the processing of MEMS devices using the SOI wafer structure, the gradual release of the underlying silicon and SiOF1 exists within the SiO2 layer to counterbalance the residual stress of the substrate, as depicted in F1 is an eccentric force, it generates a stress gradient within the SiO2 layer while laterally restraining the layer from stretching. Consequently, after the substrate is released, the influence of the shear force F1 on the SiO2 layer is also eliminated, and the lateral constraint on the cantilever beam at the lower end of the SiO2 layer disappears. This results in lateral elongation 2 layer and, concurrently, because of the stress gradient, a moment is generated, leading to deformation y1 as illustrated in Prior to the release of the substrate, a shear stress 2 layer, the cantilever beam experiences a shear force F0 to counterbalance the stress caused by the SiO2 layer, as depicted in F0 is an eccentric force, it induces a stress gradient within the cantilever beam, restraining the beam’s lateral contraction. Consequently, when the SiO2 layer is released, the influence of the shear force F0 on the cantilever beam is also eliminated, removing the lateral deformation constraint within the beam. As a result, the beam undergoes lateral deformation with shortening ΔSil, while the stress gradient generates a moment, leading to longitudinal bending deformation 2y, as illustrated in In the case of a cantilever beam with a SiO2 layer in the SOI wafer needs to be shared by the substrate layer and the device layer. That is to say, the value of the residual stress in the SiO2 layer has a residual stress value that is the sum of the substrate layer and the device layer, so the amount of deformation that occurs when removing the SiO2 layer will be greater than the amount of deformation that occurs when removing the substrate layer. Therefore, in the actual process of the MEMS beam, due to the residual stress existing in the SOI wafer, after releasing the substrate and the SiO2 layer, the cantilever beam not only shortens laterally but also deflects downward. By establishing the mechanical relationship between residual stress and residual strain of MEMS beams, residual stress in SOI wafers can be better mapped. The schematic diagram of SOI cantilever beam deformation after two different processes is shown in According to the above analysis, considering the compressive stress provided by the SiOF0 on the SiO2 layer of the cantilever beam, a SiO2 sacrificial layer is incorporated into the downward curved cantilever beam. This addition serves two purposes: it not only induces lateral elongation ΔSil but also generates deflection deformation in the cantilever beam, as illustrated in 2 layer can be regarded as applying a bending moment M0 to the cantilever beam, thereby altering the deflection of the beam from downward to upward. Consequently, the resulting deflection is manifested as y1 and y2.First, to examine the impact of shear force M0 and the shear force F0 can be expressed ash represents the thickness of the cantilever beam. The deflection y and angle θ of the cantilever beam caused by the bending moment M0 are, respectively, expressed asl represents the length and I denote the moment of inertia of the cantilever beam. E corresponds to the elastic modulus of the material used for the cantilever beam. When subjected to the shear force F0, the cantilever beam experiences a stretching effect, resulting in an elongation ΔSil in its length.A represents the cross-sectional area of the cantilever beam.The relationship between equivalent moment F1 from the substrate on the cantilever beam with a SiO2 layer can be analyzed. When subjected to shear force F1, the cantilever beam with a SiO2 layer experiences two distinct responses. First, it undergoes lateral shrinkage denoted as M1 to the beam structure. As a result, the beam’s deflection changes from an upward direction to a horizontal state, resulting in a deflection of −y1.The effect of shear force M1 and the shear force F1 can be expressed ash′ represents the thickness of the silicon dioxide layer. The deflection y1 and angle θ1 of the beam structure caused by the bending moment M1 are, respectively, expressed asF1 isE′ represents the elastic modulus of silicon dioxide and A′ represents the cross-sectional area of silicon dioxide layer.The relationship between the equivalent moment M2 to the cantilever beam, and the resulting deflection is y2, as shown in Clearly, under the constraint of the substrate and silicon dioxide layer, the cantilever beam top silicon layer can be reverted to a horizontal state from downward deflection, which is equivalent to applying a bending moment y2 and angle θ2 of the cantilever beam caused by the bending moment M2 are, respectively, expressed asThe deflection Sil and the deflection y2 of the beam structure can be represented as The deformation of the cantilever beam, characterized by downward deflection and lateral shortening, is illustrated in The bending deformation exhibited by the cantilever beam is attributed to its internal residual stresses. As a result, it is assumed that no deformation occurs at the free end of the cantilever beam. Instead, the resulting deformation is compensated by the application of a reverse axial force l2 caused by axial force BF, and the deflection f2 caused by bending moment BM are, respectively, expressed asIn the equivalent system of statically indeterminate beams, the axial tensile length Δl and the deflection f of the cantilever beam areThe axial tensile length ΔThe total length of the beam does not change and the deflection and deflection angle at the right end of the beam structure is zero. Therefore, the corresponding deformation coordination conditions areBF and BM can be obtained asBy substituting from Equations (15) and (16) into Equation (17), BF and bending moment BM, the residual stress σ can be derived asy represents the distance from any point to the neutral axis.From the axial force The approach allows for the conversion of the residual stress induced by deformation at the free end of the cantilever beam into an expression that relates to the axial force and bending moment at the right end of the beam. This establishes a mechanical theoretical model for the residual stress in SOI wafers, which is mapped by the residual strain of MEMS beams. By measuring the bending moment of the MEMS beams at various points during the machining process, the beam’s deformation deflection and deflection angle can be determined at each moment. The residual stress value within the cantilever beam is then linked to the equivalent values of axial restraint and bending moment. Through the measurement of axial restraint and bending moment, it becomes possible to obtain the residual stress present within the SOI chip.2 layer, and a 380 μm silicon substrate. The Young’s modulus of the SiO2 layer as a thin-film material decreases with increasing thickness, and its corresponding Young’s modulus is 88 GPa, 81 GPa, and 77 GPa for SiO2 layer thicknesses of 0.5 μm, 1 μm, and 2 μm, respectively [2 layer is 1 μm and Young’s modulus is defined as 81 GPa.In the experiment, two SOI wafers with both wafer orientations <100> are utilized to fabricate cantilever beam samples. Each SOI wafer consists of a 6 μm top silicon device layer, a 1 μm SiOectively . In this2 layer of the cantilever beam are removed. This results in a cantilever beam structure with only the top silicon device layer remaining. For SOI wafer 2, the substrate is removed while the SiO2 layer is retained. The cantilever beam structure of this wafer consists of the top silicon device layer and the SiO2 layer, with the substrate removed.The preparation process for the cantilever beam samples is outlined in Z-axis resolution of 0.01 μm. 2 layer and the other without such removal. Both types of cantilever beams exhibit significant residual deformation at the tail end. This residual deformation is characterized by out-of-plane deflection, which leads to blurriness or incompleteness when observed under an optical microscope. To address this, the residual stress of the wafer is characterized and analyzed based on the strain measured from the cantilever beam. The specific process for characterization is outlined in In the experiment, a confocal laser scanning microscope (CLSM), as depicted in 2 layer and has a length of 2000 μm and a width of 18 μm. The second type, denoted as CNT-2, has the SiO2 layer intact and has a length of 2000 μm and a width of 18 μm. In the second group, there are also two types of cantilever beams. The first type, labeled as CNT-3, does not have the SiO2 layer and has a length of 2000 μm and a width of 14 μm. The second type, designated as CNT4, has the SiO2 layer and has a length of 2000 μm and a width of 14 μm. However, it is worth noting that CNT-4 has experienced fracture at the midpoint, resulting in a remaining beam length of approximately 1000 μm. The structural morphology of the first group of cantilever beams (CNT-1 and CNT-2) has been obtained through CLSM, as depicted in In the experiment, two sets of cantilever beams with the same position coordinates are tested on two SOI wafers. In the first group, there are two types of cantilever beams. The first type, referred to as CNT-1, does not have the SiOThe residual strain data of the cantilever beams were obtained through experimental measurements, and curve fitting was performed using MATLAB. The deformation curves for the first and second groups of cantilever beams are depicted in 2 layers are removed, the cantilever beam exhibits a downward deflection deformation. This deflection direction aligns with the predictions of the mechanical theoretical model discussed earlier, with a deflection magnitude of 28.8 μm. The roughness present in the curve mainly stems from the surface roughness of the beam after the SiO2 layer removal. 2 layer intact, undergoes an upward deflection deformation. This deflection direction also aligns with the predictions of the mechanical theoretical model, resulting in a deflection of 307.7 μm.Considering that the length of the cantilever beam is 2000 μm, any data beyond this range are considered invalid in 2 layer intact, undergoes an upward deflection deformation with a deflection of 80.8 μm.In For the first group of cantilever beams, CNT-1 and CNT-2, the residual stress of the cantilever beam is calculated by combining the experimentally measured residual strain data with the mechanical theoretical model. The relevant mechanical results are summarized in Based on the calculation results mentioned above, the residual stress in the SOI wafer, determined by mapping the residual strain of the two sets of MEMS beams, is found to be 33.03 MPa and 31.45 MPa, respectively. Sasaki et al.  establisThe agreement between the calculated residual stress and the measured residual strain of the cantilever beam in this paper further validates the accuracy and feasibility of the proposed residual stress characterization method for SOI wafers.The method proposed in this paper for measuring SOI residual stress primarily relies on stable and effective mechanical theoretical models and formulas. Moreover, since the method only requires measuring the residual strain of the cantilever beam, the testing process is simplified, resulting in higher efficiency, lower cost, and easier operation.In industrial production, the characterization of residual stress in SOI wafers is often challenging. However, the theory proposed in this paper provides a more precise range for determining the value of residual stress, thus offering valuable insights for industrial manufacturing.Due to the inconsistent material properties of silicon and silicon dioxide, thermal mismatch stress and intrinsic stress occur when a thin layer of silicon dioxide grows on the silicon surface. The presence of residual stress affects the performance of MEMS devices fabricated using SOI silicon wafers. In this paper, we propose a high-precision, easy-to-implement, and cost-effective characterization method for measuring residual stress in SOI wafers. We analyze the generation mechanism of residual stress in SOI wafers and develop a mechanical theoretical model for MEMS beams. The feasibility of our method is verified through experimental testing and characterization using laser scanning confocal microscopy. This research provides theoretical references and experimental support for the design and optimization of devices based on SOI-MEMS technology.


Previously, the authors showed that the application of the aminodihydrophthalazinedione sodium (ADPS) immunomodulator transdermal therapeutic system (TTS) to laboratory animals provides bioavailability analogous to the intramuscular administration of this drug at the same dose. At the same time, its maximum blood concentration is significantly reduced, and the retention time of the drug in the body is increased more than 10-fold, which can contribute to prolonging the drug effect. The aim of the work was to identify a possible positive effect of the transdermal administration of the ADPS immunomodulator on reparative liver regeneration on an experimental model of extensive liver resection (ELR). It has been shown that at a period of 48 h after ELR, the percutaneous administration of the immunomodulator has a pronounced stimulating effect on the mitotic activity of rat liver cells; by 72 h after ELR, an accelerated rate of recovery of hepatic homeostasis in the body was observed in laboratory animals in groups with the application of the ADPS TTS versus the control group. Over the past decades, there has been a surge in scientific research in the development and implementation of highly active and competitive dosage forms in medical practice. Increasing attention is being paid to new drug delivery systems with improved biopharmaceutical characteristics that boost the therapeutic efficacy, tolerability, and safety of drug therapy. One such direction is the creation of transdermal therapeutic systems (TTS)—controlled release dosage forms designed for the continuous supply of drugs through intact skin into systemic circulation for a long time, limited only by medical indications. The use of a transdermal therapeutic system not only allows for increasing the drugs’ bioavailability but also eliminates the disadvantages of other methods of their administration ,2,3. In One of the prospective Russian-made drugs with an immunomodulatory property as well as an expressed anti-inflammatory property is a synthetic low-molecular-weight medicinal substance, aminodihydrophthalasindione sodium (ADPS), a derivative of phthalhydroside. The mechanism of action, in this case, is associated with its ability to reversibly (for 6–8 h) inhibit the excessive synthesis of tumor necrosis factor-α, interleukin-1, interleukin-6, and other proinflammatory cytokines by hyperactivated macrophages. In addition, ADPS stimulates the production of macrophages of key growth factors regulating regenerative processes, angiogenesis, and collagen production in the focus of inflammation .The authors have developed a transdermal therapeutic system containing the ADPS synthetic immunomodulator . Such a It was shown in vivo that the bioavailability of the transdermal administration of an immunomodulator is equal to the bioavailability of the intramuscular administration of this medicinal substance at the same dose. At the same time, the maximum blood concentration of ADPS is significantly reduced, but the retention time of this immunomodulator in the body is increased by more than 10-fold, which may contribute to the prolongation of the medicinal effect . HoweverThere are data on the positive effect of various immunomodulators by injectable administration on the process of liver tissue repair in experiments ,11.To confirm the specific activity of the ADPS immunomodulator transdermal administration, the authors used a model of extensive liver resection (ELR) in rats.Most knowledge about liver regeneration is obtained from rodent models where a two-thirds partial hepatectomy was performed . This tyLiver regeneration after partial hepatectomy is carried out with the participation of all mature types of liver cells. The liver manages to restore any lost mass and adjust its size to the size of the body while at the same time providing full support for the body’s homeostasis throughout the regeneration process ,15. At tIn clinical practice, the problem of accelerated liver recovery after extensive resection in cancer patients, as well as in donors with related transplantation of the right lobe of the liver, is of the greatest interest .It is worth noting that an important role in the regulation of regenerative processes in the body belongs to the immune system, all elements of which are actively involved in restoring the structure and function of cells of the damaged tissue. In this regard, the question arises about the expediency of using immunological drugs to impact the reparative processes in the affected organs and tissues ,18. The It is known that the mitotic activity of hepatocytes is reduced on the first day after surgery, but already on the second day its increase is noted . The maxADPS immunomodulator on reparative liver regeneration in an experimental model of extensive liver resection.The aim of the work was to identify a possible positive effect of the transdermal administration of the ® UV, Millipore, NJ, USA), 0.9% sodium chloride solution , sodium dodecyl sulfate , apricot kernel oil , 0.5–4% stearic acid (C17H35COOH), 55 to 70% oleic acid (C18H34O2), and 22 to 35% linoleic acid (C18H32O2), max 1% linolenic acid (C18H32O2) , α-tocopherol acetate , sodium docusate , Decaglyn PR-20 emulsifier ((C3H5O2)n(C18H32O2)m, Nikko Chemicals Co., Ltd., Tokyo, Japan) were used in the manufacturing of matrix-type laboratory samples of the aminodihydrophthalasindione sodium transdermal therapeutic system  with an emulsion delivery system ..24].It is known that the degree and timing of liver regeneration vary depending on circadian rhythms . The opeAll the animals were divided into seven groups: six groups of rats (n = 42) were used to create the model of ELR, and a group of intact rats (n = 5). Animal observations were carried out during the periods of 24, 48, and 72 h after ELR. The periods of 48 and 72 h were selected because the maximum mitotic and functional activity of hepatocytes is observed between the second and fifth days after ELR ,23. A peAnimals were treated with the ADPS TTS on the dorsal skin area with previously removed hair immediately after liver resection in groups 24/1, 48/1, and 72/1 .The duration of application was 24 h in groups 24/1 and 24/2; in groups 48/1 and 48/2—48 h with a single replacement of TTS after 24 h; in groups 72/1 and 72/2—72 h with a double replacement of TTS every 24 h.The following biochemical parameters were determined on the Reflotron™ analyzer : alanine aminotransferase (ALT), aspartic aminotransferase (AST), gammaglutamintranspeptidase (GGT), alkaline phosphatase (ALP), total protein, albumin, total bilirubin, creatinine, and urea.To accomplish this, the tip of a rat’s tail was dissected under anesthesia , and blood (32 mL) was taken with a pipette and applied to Reflotron™ test strips, which were immediately placed in a biochemical analyzer.To assess liver mass recovery dynamics in each operated animal, the removed part of the liver was weighed on an electronic scale  immediately after ELR. This removed part of the liver was taken as 70% of the total liver mass. Then, based on these data, the initial mass of the liver remainder for each animal was calculated. Then, after 24, 48, or 72 h of TTS application (in accordance with the labeling of the group), the remaining part of the liver was excised, its mass was measured, and the values obtained were compared with the calculated initial mass of the liver remainder for this laboratory animal.The effectiveness of the stimulating effect of the percutaneous administration of an immunomodulator on the processes of liver regeneration after ELR was evaluated by the mitotic (proliferative) activity of hepatocytes in the remainder of the resected liver. To do this, the extracted fragment of the middle lobe of the liver was cut into 3 × 4 × 5 mm pieces and placed in Buena solution for fixation. After 24 h, the Buena solution was replaced with 70% ethyl alcohol. When the fixation was completed, the pieces were washed in running water for 2–3 h, dehydrated in alcohols of ascending concentration, and poured into paraffin. Paraffin sections with a thickness of 4–5 µk were wet-glued onto glasses with a poly-L-lysine coating . Then the preparations were dried for 48 h in a thermostat at 37 °C, dewaxed, rehydrated, and stained with hematoxylin and eosin.MI, ‰):M—the number of dividing cells,N—the total number of analyzed cells.The mitotic activity of hepatocytes was studied after staining histological preparations of the excised liver. For each sample, the number of mitosis figures and the total number of cells were determined on a histological section of liver tissue stained with hematoxylin and eosin with an ×200 microscope magnification . This formula was used for the mitotic index calculation (t-test (standard software package Microsoft Excel 2007). The differences were considered statistically significant if p < 0.05.Using the Shapiro-Wilkes test on a small number of samples (n ≥ 5), a regular distribution of experimental data was proved. The validity of differences was determined using Student’s It is known that after extensive liver resection, the organ is restored to its original mass due to the proliferation and polyploidization of hepatocytes. It was noted that the distinct signs of increased proliferative activity of liver cells after extensive resection appears only after 48 h . Howeverp ≤ 0.05). At 72 h after ELR, the mitotic activity of hepatocytes decreased fourfold, while its values did not differ in both groups (p > 0.05).The mitotic activity of hepatocytes at 24 h after ELR in both groups did not differ from the initial value immediately after resection, equaling 0.14 ± 0.07‰. At 48 h after ELR, a significant increase was established, and in the group with TTS application, the mitotic index was significantly higher than in that without it  than similar indicators in the group without TTS application (ALT 142.0 ± 26.8 U/I and AST 273.1 ± 119.4 U/I).As can be seen from p < 0.05) than this indicator in the control group of animals.In the group of laboratory animals with the application of ADPS TTS, there was an increase in the level of urea and alkaline phosphatase from 24 to 48 h of the experiment. However, by 72 h of observation, there is a sharp decrease in the urea index to 6.8 ± 0.8 mmol/L, which corresponds to normal values (in the intact group—7.5 ± 0.4 mmol/L). In the period from 48 to 72 h of observation, the alkaline phosphatase index remained at the same level (⁓560 mmol/L), which is significantly lower (p < 0.05) than in the control group , and did not significantly differ (p > 0.05) from the values of the corresponding biochemical parameters of the intact group .Indicators of bilirubin and creatinine in the blood  in the gIn the study of total protein and albumin in the blood of laboratory animals, it was found that a day after ELR, a gradual increase in these indicators was observed in both groups . At the Evaluating the results of the effect of a percutaneous administration of an immunomodulator on hepatic homeostasis restoration, it can be concluded that a faster normalization of the majority of biochemical blood parameters is observed in the group of laboratory animals with the application of the ADPS TTS.In recent years, the range of medicinal substances used in the form of transdermal therapeutic systems has been significantly expanding. This is due not only to a number of advantages of the percutaneous administration of medicinal substances in comparison with traditional methods but also to the improvement of methods of influencing the percutaneous transport of medicinal molecules ,33. CurrThe relevance of studies related to the search for stimulators of liver regeneration is due to the need to increase the effectiveness of rehabilitation therapy to prevent the development of liver failure in patients after extensive liver resection and donors with related transplants .It is known that during the surgical intervention in the hepatic parenchyma, along with the death of liver cells, their regeneration processes occur simultaneously, and under physiological conditions, the regeneration of hepatocytes proceeds much faster than their death. However, despite the fact that no organ can compare with the liver in terms of the intensity of this process, its physiological regeneration is still very slow . Our stuThere are works on the use of various ways to stimulate liver regenerative processes: the introduction of various pharmaceutical and biological agents or products of cellular technologies.A number of works are devoted to the study of the effect of nicotinamide on liver regeneration and the restoration of its function. For example, in tests conducted on a liver resection model in C57BL/6 mice using immunohistochemical analysis , it was shown that the addition of exogenous nicotinamide (Nam) promotes the proliferation of hepatocytes and accelerates the recovery of liver tissue. The addition of Nam protected liver function after resection, which is confirmed by the data from studying the morphology of liver tissue and changes in serum markers of its damage . It was Changes in the same parameters showing the deterioration of liver cells after resection was observed by O. Parlak et al. when evaluating the L-carnitine effect on liver regeneration in an experiment . On a liC. Mangieri et al. carried out the assessment of the ongoing liver regeneration in rats with an intraoperative infusion of hepatocyte growth factor (HGF). It was found that this type of HGF infusion significantly increases liver regeneration after portal branch ligation in rodents .Experimental studies on mice were also described, where the role of bile salts in liver regeneration after its resection was shown. Under the influence of these salts, after hepatectomy, bile salt receptors are activated in non-parenchymatous (plasma membrane receptor TGR5) and parenchymal (intracellular receptor Fxr) liver cells, thereby providing signals for regenerative processes .Work is also underway to study MicroRNAs (miRNAs) as stimulators of liver regeneration ,39. For It should be noted that all these works are still at the stage of fundamental research and require a further detailed study for clinical practice applications. The above methods of stimulating liver reparative processes using cellular technologies are more complex, time-consuming, and expensive compared to the ADPS TTS developed by the authors. The ADPS TTS developed by us is a three-layer patch. The first layer is a backing film used as the outermost layer of a transdermal system to protect the product during wear, the second line is a nonwoven material containing an emulsion composition with an immunomodulator and percutaneous carriers, and the third layer is an anti-adhesive film that is removed before use. The composition of the emulsion was published earlier .The studies presented in this article are aimed at proving the possibility of using a prolonged form of an immunomodulator as a maintenance therapy to stimulate the regeneration of a damaged liver.At the first stage, a new dosage form of the immunomodulator was developed—the ADPS TTS, with the presence of percutaneous transfer of the drug substance proved in vitro . In the The results of studying the mitotic activity of hepatocytes in the early stages following extensive liver resection in the studied groups of animals showed that ELR induces the proliferative activity of hepatocytes, while percutaneous administration of the ADPS immunomodulator after ELR has a positive effect on the proliferation of hepatocytes in the remainder of the resected liver. It should be noted that on the third day after ELR, with the percutaneous administration of ADPS, there was a tendency to a faster normalization of the blood biochemical parameters of experimental animals versus the control group of operated animals (without the application of TTS). It should be emphasized that the stimulating effect of the ADPS immunomodulator on the regeneration of the damaged liver was established for rats with a high level of internal reparative liver regeneration.The revealed inhibitory effect of the percutaneous administration of ADPS on the normalization of the level of total protein and albumin in blood after ELR requires additional studies.Note that in the future, we aim to compare the effectiveness of oral, injectable, and transdermal methods of administration. These studies are planned in the ADPS TTS Preclinical Research Program.


Ultra-high-performance concrete (UHPC) has greater mechanical and durability performance than normal concrete (NC). Using a limited dosage of UHPC on the external surface of NC to form a gradient structure could significantly improve the strength and corrosion resistance of the concrete structure and avoid the problems caused by bulk UHPC. In this work, white ultra-high-performance concrete (WUHPC) was selected as an external protection layer for normal concrete to construct the gradient structure. WUHPC of different strengths were prepared, and 27 gradient WUHPC-NC specimens with different WUHPC strengths and interval times of 0, 10, and 20 h were tested using splitting tensile strength to reveal the bonding properties. Fifteen prism gradient specimens with the size of 100 × 100 × 400 mm and a WUHPC ratio of 1:1, 1:3, and 1:4 were tested using the four-pointed bending method to study the bending performance of the gradient concrete with different WUHPC thicknesses. Finite element models with different WUHPC thicknesses were also built to simulate the cracking behaviors. The results showed that the bonding properties of WUHPC-NC were stronger with less interval time and reached the maximum of 1.5 MPa when the interval was 0 h. Moreover, the bond strength first increased and then decreased with the decline in the strength gap between WUHPC and NC. When the thickness ratios of WUHPC to NC were 1:4, 1:3, and 1:1, the flexural strength of the gradient concrete improved by 89.82%, 78.80%, and 83.31%, respectively. The major cracks rapidly propagated from the 2 cm position to the bottom of the mid-span, and the thickness of 1:4 was the most efficient design. The results simulated by finite element analysis also proved that the elastic strain at the crack propagating point was the minimum and was easier to crack. The simulated results were in good accordance with the experimental phenomenon. Howeve solved ,4. Concre solved ,6,7. Ulte solved ,10,11,12e solved ,14, and e solved ,16. Howee solved ,18. Meane solved ,20,21,22The functional gradient approach is a common method used to design materials with the desired performance and is often used in nanomaterial synthesis ,25,26,27The bonding property is one of the key points for the gradient concrete, which is affected by many factors, such as stiffness, roughness, moisture, and shrinkage . Since tIn this work, a white UHPC (WUHPC)-NC gradient concrete was constructed to significantly improve the mechanical strength, corrosion resistance, and aesthetic appearance with a small dosage of WUHPC so that this gradient concrete could be widely used in urban buildings, city overpass bridges, and landscape architectures. WUHPC was designed as a thin overlayer to control the dosage and protect the inner NC from an exposed environment. The interval time of two concretes, and the strength degree of WUHPC were varied to study the bonding performance of the gradient concrete to determine the optimal mixed ratio and formation technology. The bending properties of the WUHPC-NC gradient concrete were also evaluated by flexural strength and four-pointed bending. Finite element analysis was used to reveal the strain distribution in the concrete and to predict the crack position. The research steps are illustrated in P·W 52.5 White Portland Cement (WPC), P·O 42.5 Portland Cement (PC), white silica fume (WSF), metakaolin (MK), limestone powder (LP), and Fly ash (FA) were selected as binder materials. The physical properties and the chemical compositions of the binders are shown in To reveal the effect of the strength gap on the bonding performance of the gradient WUHPC-NC, the WUHPC with different strengths was prepared in this experiment. The WUHPC was prepared by WPC, LP, WSF, MK, and sand without coarse aggregate. The strength of WUHPC was adjusted by W/B ratio, mineral admixture substituted ratio, and fiber content, while the hybrid fiber ratio was kept with SSF:HSF = 2:1. The detail of mix proportions and the designed strength of WUHPC and NC are listed in For WUHPC preparation, powder materials, including WPC, WSF, MK, LP, and sand, were first dry mixed in a container, then water and WR were added with continuous stirring until the uniform matrix was formed. Last, steel fibers were slowly added in 2–3 min. The preparation method of NC was traditional; the powders and stones were mixed with water in a blender.To form the gradient concrete, the prepared WUHPC and NC were cast successively into the mold of 100 × 100 × 100 mm for the splitting tensile strength test and 100 × 100 × 400 mm for the bending strength test. Twenty-seven samples were used in the splitting tensile strength test, and 15 samples were used in the bending test in total. Three different interval times between WUHPC and NC casting were chosen, which were 0 h, 10 h, and 20 h as a comparison. Additionally, the thickness ratios of WUHPC to NC of 1:1, 1:3, and 1:4 were prepared to reveal the optimal dosage of WUHPC, which is shown in The bonding property between WUHPC and NC in the gradient concrete was characterized by the splitting tensile strength. During the test, the specimen was pleased in the mold, with the interface verticalness. Two steel sticks were put at the junction of two materials; then, a vertical load was applied to the steel sticks at the rate of 0.05 MPa/s. The experimental setup is shown in According to standard ASTM C1069 , a univeThe specimens of NC and WUHPC with the size of 100 × 100 × 100 mm and 40 × 40 × 160 mm were used for compressive strength testing, and the load rates applied for two concretes were 0.5 MPa/s and 2.5 MPa/s, respectively. For each group, three specimens were tested, and the average results were calculated as the compressive strength. The morphology and the element distribution of the gradient concrete at the joint region were analyzed by scanning electron microscopy (SEM). The specimens around the joint area were cut into slices with a thickness of 5 mm by a high-speed precision cutting machine. Then, the test slices were immersed in anhydrous ethanol to stop hydration.The cementitious materials in concrete reacted to harden with time; it was easily understood that shorter interval time resulted in a longer reaction time of two concretes and led to stronger bonding strength. Once WUHPC and NC were cast together with an interval time of 0 h, the contact region was fresh and blended to react continuously and form a complete block. When the interval time increased, the activity of cementitious materials declined, and the surface began to lose plastic characteristics after the initial setting time so that an obvious boundary was generated at the interface between two concretes, which would weaken the bonding property. Additionally, with the strength increased, the matrix of WUHPC became denser, and the fresh NC was hard to mix at the interfacial position, resulting in a lower splitting tensile strength. Furthermore, compared with U2 and U3, more steel fiber was used in U2, the bonding property of the interface was better than in U3, and the splitting tensile strength was also increased.The morphologies of the split surface of the gradient concrete samples after the test are shown in In The flexural strength of U2, NC, and the gradient concretes with different WUHPC thicknesses are summarized in The flexural strength was mostly determined by the ultimate load capacity under four-point bending. The results showed that when the thickness of WUHPC: NC = 1:3, the gradient concrete could bear the highest bending load. This proved that even with a small dosage of WUHPC, the gradient structure also performed an equivalent mechanical behavior to WUHPC under bending conditions.Due to the high strength and the reinforcement of fiber, the deformation of WUHPC was much better than NC, and it did not rupture after the ultimate load. With the WUHPC dosage of 1/3, the gradient concrete showed similar deformation properties with pure WUHPC.The photos of cracks in the gradient concrete after four-point bending tests are present in In sum, the mechanical strength of the gradient concrete composited with a small dosage of WUHPC was more closed to that of the pure WUHPC and was much better than NC. When the gradient concrete with a thickness ratio of 1:4 between WUHPC and NC was used in the construction, the mechanical strength was significantly improved with limited materials cost increase, and this might be accepted in field applications.The morphology of the gradient concrete around the contacted area is shown in To analyze the difference between the two concretes, the element mapping crossing the boundary was tested and shown in The morphology and the linear element mapping of the matrix proved that there was indeed a transition zone in the gradient concrete, but the width of this zone was decreased with the increase of interval time. With the interval time of 0 h, two pieces of concrete were fresh and well-flowed. When they come into contact together, the matrix at the interface may blend into the other part due to gravity. That is why the elements Si and Ca vibrate at distances 120–160 μm in The size of the finite element modeling was 100 × 100 × 400 mm, which was composed of different thicknesses of WUHPC. The thickness ratios of WUHPC and NC were 1:4, 1:3, and 1:1, respectively. The contact mode between WUHPC and NC was binding, which was perfect bonding. The support sticks were rigid without displacement change. The mesh size was set to 20 mm, shown in The total deformation refers to the amount of displacement generated when a structure is subjected to load, which reflects the stiffness of the structure. The equivalent plastic strain was used to determine the position of the yield surface once the material was strengthened. The total deformations and equivalent elastic strains of the gradient concrete were simulated and analyzed by finite element analysis. It was found that when the gradient concrete was subjected to four-point bending, the displacement and the strain at the center part were the largest, so the cracks usually started from the bottom of the middle part. When the pressure was constant, the total deformation of the gradient concrete decreased with the increase of WUHPC thickness, but the total deformation reduction rate also decreased. By comparing the equivalent strain contours of the gradient concrete, it could be found that there was a region on the upper side of the split point of the gradient concrete where the strain was the minimum, which was why the split occurred.(1)The splitting tensile strength of the gradient concrete increased with the shorter interval time and reached the maximum once the strength gap between WUHPC and NC was moderate. With the increase of interval time, the boundary of the gradient concrete at the joint surface became more and more clear, which was not conducive to the bonding surface.(2)WUHPC could effectively improve the flexural performance of the gradient concrete, but this effect was not linearly increased with the thickness of WUHPC. When the thickness ratios of WUHPC to NC were 1:4, 1:3, and 1:1, compared with NC, the flexural strength of the gradient concrete increased by 89.82%, 78.80%, and 83.31%, respectively. From the results, the small dosage of WUHPC could significantly improve the bending properties of NC.(3)In the bending process, WUHPC was stressed first, and the cracks developed upward from the middle bottom of WUHPC, but the total development was relatively slow. Therefore, the deformation of the gradient concrete increased in the early stage, but when NC was stressed, the crack development speed increased. Moreover, there was a crack-splitting point that was independent of the thickness of WUHPC. In the experiment, the optimum thickness ratio (WUHPC:NC) of the gradient concrete was 1:4.(4)The total deformation and equivalent elastic strain of WUHPC with different thicknesses under the same pressure were simulated by finite element analysis. The results showed that the damaged area of the gradient concrete was easy to occur in the middle position, which was consistent with the cracking position of the gradient concrete. The equivalent elastic strain at the crack splitting point was smaller than that around it, which resulted in easy cracking, and the simulated results were close to the experiment.(5)By comparing the deformations of the middle bottom, the joint surface, and the center position, the displacement difference between the bottom and the middle section gradually decreased with the increase of WUHPC thickness. Therefore, the thickness of WUHPC was not suggested to be too large.(6)The steam curing method was adopted for the gradient concrete in this study. Although the curing time was greatly shortened, the steam curing condition could not make the gradient concrete be formed on a large scale, which was not conducive to its application in practical engineering. At the same time, due to the difference between WUHPC and NC, steam curing would promote hydration, leading to a large shrinkage stress, which might not be conducive to the bond performance of the gradient concrete.The combination of WUHPC and NC in the gradient concrete possessed better bending strength than plant NC. By studying the influence of pouring technology on the bonding property of the gradient concrete and the influence of WUHPC thickness on the flexural property of gradient concrete, the following conclusions are drawn through the numerical simulations by finite element analysis.