TG) polymers needed to produce hard films to be used as coatings will not produce coherent films at low temperature. This issue has been dealt by the use of temporary plasticizers added with the objective to reduce the TG of the polymers during film formation, while being released to the atmosphere afterwards. The main problem of these temporary plasticizers is their volatile organic nature, which is not recommended for the environment. Therefore, different strategies have been proposed to overcome their massive use. One of them is the use of hydroplasticization, as water, abundant in latexes, can effectively act as plasticizer for certain types of polymers. In this work, the effect of three different grafted hydroplasticizers has been checked in a (meth)acrylate copolymer, concluding that itaconic acid showed the best performance as seen by its low minimum film-formation temperature, just slightly modified water resistance and better mechanical properties of the films containing itaconic acid. Furthermore, film formation monitoring has been carried out by Differential Scanning Calorimety (DSC), showing that itaconic acid is able to retain more strongly the water molecules during the water losing process, improving its hydroplasticization capacity.The film formation step of latexes constitutes one of the challenges of these environmentally friendly waterborne polymers, as the high glass transition ( TG) of the binder polymer. On the one hand, for coating applications, the formation of a hard and scratch-resistant coherent film is essential, which needs a polymer with a high TG. On the other hand, it must be possible to obtain a film at ambient temperature, which requires a low MFFT. However, the TG and the MFFT are directly related to each other. This is known as the “film-formation dilemma” and constitutes one of the greatest challenges in the future development of waterborne latex particles for coating applications . The difference between the dry and the wet TG shows the extent of plasticization promoted by water. It is important to point out what is meant by the fraction of water in this equation. As presented by Hodge et al.  is the scanning rate, A [s−1·m−3] is the pre-exponential factor in the expression of the nucleation rate, k [Nm·K−1] is the Boltzman’s constant, γ [Nm−1] is the interfacial tension between the undercooled water and the ice germ, Vs  is the molar melting heat and Tm [K] is the melting temperature. The parameters γ, Vs, Lm and Tm are specific for water, allowing us to assume that this relation can also be used for any water/organic emulsion, as far as the crystallization mechanism is not changed significantly by the organic phase [R* and the freezing temperature T:To use the DSC for the determination of the water domains/droplets size Clausse et al. ,25 definic phase ,25. ThisT, at constant Tm, the smaller the radius of the germ, which has influence on the nucleation rate, resulting in a smaller water domain. For a DSC latex sample at the same drying stage and with the same amount of water, a lower domain size results in an increased number of droplets and thus in a better water distribution and plasticization effect. However, this equation cannot be used as such, because it is not possible to determine directly the interfacial tension γ between the undercooled water and the ice germ. For this, normally the relation between the water droplet size and the temperature is estimated by optical methods like cryogenic electron microscopy. In the case of the latexes investigated during this project, this is not possible because the freezing bound water is inside the latex particle. However, taking into account the latex particle size of ~120 nm for the emulsions used, the water droplet diameter DZ of ~ 1 nm for the bound freezing water seems to be a reasonable assumption. Due to this, it was decided to use the relation between DSC temperature shift and droplet size obtained from a W/O emulsion analyzed elsewhere, with water droplet diameters in this range. Díaz Ponce et al. [Equation (2) shows clearly that the lower the freezing temperature e et al.  analyzedco-butyl acrylate (60/40%) that was not able to form films at room temperature. Initially the macroscopic effect of the incorporation of three grafted THPs on the MFFT, TG, mechanical properties and water absorption of the final films was analyzed in order to find the one providing the best film-formation abilities, together with the less detrimental effect on the final films. Then, the hydroplasticization process was analyzed by DSC. The effect that the different grafted THPs had was analyzed by carrying out film-formation monitoring DSC at different drying stages. By the quantification of the water domain sizes for latexes with different THPs, a better understanding of the hydroplasticization effect was sought. To the best of our knowledge, this is the first time that such correlation between water domain size and hydroplasticization effect is quantified. Furthermore, the water absorption process of dried films containing THPs was also analyzed by DSC. The water distribution in both processes (film formation process) and water absorption of dry polymer films was found to be different by wet DSC, which stands as a powerful tool to monitor hydroplasticization.In this work, initially three functional monomers able to produce hydroplasticization were chosen: methacrylic acid, itaconic acid and polyethyleneglycol methacrylate. They were individually incorporated to a polymethyl methacrylate-Technical grade monomers methyl methacrylate , butyl acrylate , methacrylic acid  and itaconic acid  were used to synthesize the latexes. Polyethyleneglycol methacrylate  was used as macromonomer. Sodium dodecyl sulphate  was used as surfactant to stabilize the droplets and ammonium persulphate  to initiate the polymerization. All the chemicals were used as received. Deionized MilliQ water was used as polymerization media.Seeded semibatch emulsion polymerization was used for the synthesis of the latexes. The seed was prepared with BA/MMA (40/60 ratio) at 10% solids content with SDS as surfactant (0.5 wt % based on monomers) and APS as initiator (0.06 wt % based on monomers). Three different monomers were chosen to be used as grafted THPs: methacrylic acid (MAA), Polyethyleneglycol methacrylate (PEGMA) and itaconic acid (ITA) . MAA posThese functional monomers were fed together with BA/MMA at 40/60 weight ratio to the seed to produce the final latexes named with the name of the functional monomer  . A referMFFT was measured by a MFFT bar of our own construction. The steel bar was heated on the one side to 40 °C and cooled to 0 °C on the opposite side to produce a temperature gradient. The temperature along the bar was measured with PT-100 sensors. For the measurement, a polymer film with a thickness of 30 µm was applied on the bar. The temperature at which a coherent transparent film was obtained is the MFFT.−1.The mechanical properties of films dried at different temperatures were measured by tensile testing using a Stable Micro Systems Ltd.  with a constant velocity of 5 mm/s, corresponding to an initial strain rate of ca. 0.33 sThe water absorption of the films was measured by immersing the films dried at 60 °C in water for 11 days. During this time, the samples were weighed every 24 h.−1 , then heating to 100 °C , second cooling to −20 °C  at 10 °C·min−1 and then heating to 100 °C at 10 °C·min−1 and cooling again to 25 °C. The second heating cycle was used for the determination of the TG.DSC measurements of the latex films dried at 60 °C for 24 h were measured on Q1000, TA Instruments . The scanning cycles consisted of first cooling to −20 °C at 10 °C minApart from these DSC measurements of dried films, in this study DSC measurements of wet samples were also carried out. For the monitoring of the drying process, 5 mg of latex was weighed into the pan and we waited until a sufficient amount of water evaporated to obtain the desired water content. For these wet DSCs, the temperature range used was −60 to 60 °C and the heating rate 5 °C/min.TG, chemical resistance and mechanical properties can be tuned [TG = 30 °C. Apart from the REF latex, three latexes in which MAA, ITA and PEGMA functional monomers had been added were also synthesized. The functional monomers were chosen based on the ability to be incorporated into the polymer chain and to bind water. The main goal was to identify a compound that is able to bind enough water to obtain a good plasticization effect without having a negative impact on the latex viscosity and on the film properties. Therefore, beside TG and MFFT, the mechanical properties and the water absorption were investigated and compared.Due to their flexibility, acrylic latexes are broadly used in the coating industry . For allbe tuned ,29. The All the reactions were carried out as seeded radical emulsion polymerization in a semi-continuous manner, in order to obtain 50 wt % solids content latexes. Final conversions higher than 99.5% were obtained. It has to be pointed out that the latex synthesized with ITA presented some challenges. ITA is a carboxylated water-soluble monomer used occasionally as co-monomer in the latex production by emulsion polymerization to improve colloidal and mechanical properties . HoweverTG for the synthesized latexes. As reference, REF latex  was used with a TG of 30 °C and a MFFT of 25 ± 1 °C. The wt. % of the THPs used is based on the polymer content in each latex. Methacrylic acid (MAA) was the first grafted THP investigated because it has the potential to bind water and is known to readily incorporate into BA-MMA polymer chains [TG was only slightly influenced and the MFFT range was decreased by 9 °C to 16 ± 1 °C.r chains . HoweverTG. The wet TG is calculated based on the water percentage being able to absorb each copolymer (based on Barrie’s method) and, with the aid of the modified Flory–Fox equation proposed by Tsavalas and Sundberg [TGs were lower when a THP was introduced in the copolymer. However, the decreases observed in the wet TGs were not completely correlated to the decreases in the MFFT values, as ITA latex showed a higher MFFT decrease compared to the slight wet TG decrease. Therefore, it can be concluded that water absorption capacity obtained from Barrie’s method cannot be taken as the only indicator to evaluate the extent of the hydroplasticization effect.The latex containing ITA showed a huge decrease of the MFFT down to 14 ± 2 °C, what is 16 °C lower than its Sundberg , the valTG of 30 °C).The influence of the used THPs on the mechanical properties and the water uptake of the final dried films were also investigated. The films used for these studies were initially dried at 20 °C and relative humidity (RH) = 55% for 48 h. As can be seen in The mechanical properties of the ITA film annealed at 20 °C could therefore be measured. As it can be seen in As expected, the mechanical performance increased with increasing the annealing temperature, at 60 °C reaching similar mechanic properties compared to REF latex annealed at 60 °C. If all the latexes with grafted hydroplasticizers were annealed at 60 °C, the mechanical properties shown in Finally, the water absorption of the films with the grafted THPs was analyzed, for the films dried at 60 °C . PEGMA aAs explained in the introduction, in order to obtain a deeper knowledge of the hydroplasticization process, DSC measurements of THP latexes in the presence of water were carried out based on the work of Klots et al. . There, H obtained at −19.4 °C, the amount of nonbound freezing water can be calculated, and given the total amount of water added to the system, the amount of bound water can be inferred [HDSC = 57 J/g sample and knowing that the endotherm value for free water crystallization is ∆Hwater = 334 J/g, taking into account that 1.5 mg of polymer and 1 mg of water were initially added to the sample, it can be concluded that 43% of the water initially present in the pan was not bound to the polymer (and it froze at −19.4 °C), and the rest (57%) was bound to the polymer. As a result, each polymer gram was able to bind 0.38 g of water, i.e., 27.5% of water in the water swollen polymer. Similar DSC experiments  were carried out for all the films produced with grafted THPs, in order to determine the amount of bound water . The bound water crystallizing at lower temperatures probably is linked to the more hydrophilic ITA moieties, while the bound water crystallizing at higher temperature is linked to the acrylic polymer without ITA. The same splitting, even if less expressed, can be observed for the PEGMA film, showing domains more and less hydrophilic.These DSC measurements down to −60 °C after immersion of the films in water for one week allowed the calculation of the amount of freezing bound water, and by subtraction, the amount of nonfreezing water . The calculated amounts are shown in The quantification of the bound water for the samples immersed in water for one week provides insight to the water distributed in the final dried polymer film. This measurements could be of interest when studying the water uptake by latex containing different surface functionalities  or when As mentioned in the previous section, DSC measurements were also carried out with latexes at different drying stages, taking the measurement down to −60 °C. Wet latexes were placed in the aluminum pans used for the DSC measurements, and their weight was monitored along time, in order to stop the drying step at different water contents, from the initial 50% water content (50% solids content) to the final 0% of water. The discussion of the obtained results will be focused on the freezing bound water peaks.2O molecules, which need to overcome a specific energy barrier is needed. In the case of water, this can happen through sufficient cooling until an ice nucleus is formed. Normally, water freezes around 0 °C. The nucleation is a stochastic process. The more water molecules are present, the higher the probability of nucleation and crystallization. In a small water domain, the probabilities are lower, and therefore a lower temperature is necessary. This phenomenon is known as supercooling. With progressive drying of a latex, the water domains become smaller, resulting in the observed crystallization temperature shift for different drying stages. It is also possible that the thermogram shows one curve with multiple crystallization peaks, in a process known as fractionated crystallization [To understand the obtained thermogram, the crystallization process of water, especially of small water domains, has to be taken into account. To form a crystal structure, a certain amount of Hlization ,35.As for the REF latex, a peak shift down to lower transition temperatures and an increase of the peak area with decreasing water content can be observed. The biggest shift occurs for the sample with 10% water content. The water is distributed well throughout the polymer matrix in such small domains so that −50 °C is necessary to freeze it. This is the biggest shift of all analyzed samples.The bound water peaks corresponding to the drying of latex containing PEGMA are shown in The ITA latex and PEGMA latex both contain a THP, the hydrophilic functional monomer. This functional monomer disturbs the statistical distribution of freezing bound water observed for the REF latex by creating areas of higher and lower hydrophilicity. The results show that ITA allows strong binding of water into the polymer matrix until the last stage of the drying process, the stage where the chain interdiffusion occurs. This explains the strong decrease of the MFFT, down to 14 ± 2 °C.To confirm the robustness of the new implemented procedure for monitoring the film drying by DSC, the measurements for the drying latexes were repeated for ITA, PEGMA and REF latexes, and it was found that the results are reproducible.As it has been observed, the freezing bound water crystallization peaks found during the drying step of the latex are very different to the ones observed in the films immersed in water for one week. In fact, the process of water entering the dried film (important for water resistance) is different from the process of water leaving the latex during the film formation (important for the hydroplasticizing effect), what is essential for the plasticization effect. Therefore, the following of the drying process by DSC can be a useful tool to study the hydroplasticization effect. The determination of the water domain size has been proposed in this work as a mean to quantify the hydroplasticization process.TFreeze  is caused by the presence of compounds dissolved in the water phase .Therefore, the distribution of water domains in a drying latex will determine the water domain sizes, which, as seen before, will determine the crystallization temperature. To draw conclusions, the freezing temperatures for the different drying stages were collected for repeated DSC measurements during the drying of the different latexes and were plotted in Using the freezing temperatures and the assumptions presented in the Introduction, the size of the bound water droplets was estimated and plotted versus the drying stage .The calculated droplet size range from 0.17 to 0.64 nm seems small taking into account the size of water at around 0.27 nm [In summary, it can be considered that monitoring the drying process of latexes can give an extensive set of information about the hydroplasticization process during the latex film formation process. It is not possible to obtain exact absolute numbers of water domain sizes, but accurate trends allow an accurate comparison between latexes and the influence of the functional groups introduced into the latex as THPs.TG, and with just slight impacts on the chemical resistance and improving the mechanical properties at low drying temperatures. Regarding the film properties, some shortcomings have to be considered. The biggest drawback is the dependency on the drying conditions, as these still have a great influence on the final latex film properties. However, with the right functional compound and the right drying conditions, excellent films could be made without the use of any VOC.The effect of different compounds able to bind water to the polymer matrix and favor its hydroplasticization during the film formation process was analyzed in this work. Specifically, the goal of the temporary hydroplasticizers (THP) was to decrease the MFFT, without affecting the rest of the film properties. A BA/MMA (40/60) latex was chosen as reference latex, to which different grafted THPs were included. The results obtained from this investigation showed that the basic concept of temporary hydroplasticization works and can be tuned by incorporating the right functional compound. From the chosen grafted THPs , it was shown that with the addition of itaconic acid it was possible to decrease the MFFT down to 14 ± 2 °C without changing the The compound responsible for the plasticization effect is water. The used functional compound, the THP, acts as a door or storage to hold the right amount of water and distribute it in the polymer matrix to promote the film formation. For this, it is crucial to understand the water distribution and movement during the film formation. To enable this, during this project a method was developed to monitor the water redistribution during film formation by DSC. The monitoring of the crystallization of bound and unbound water during the latex drying process by DSC helped to understand the redistribution of water domains during the drying process. Two basic mechanisms were recognized. The first one is a steady movement of the water along the polymer matrix and water domain shrinking during the drying. This was the case for the PEGMA and REF latexes. The second occurred for the ITA latex. Here the water domains were set by the ITA, strongly limiting the movement and leading to a splitting of the fixed water domains during the drying process. This second mechanism shows a better water domain distribution, resulting in a stronger MFFT decrease.1H NMR relaxometry [The THP concept constitutes a very promising approach, for eliminating VOC from latex paints. However, this concept still needs extended investigations. Important in doing so is the focus on the mechanisms involved in the interaction between water and the polymer matrix, aside from the common film property testing. The latex film formation monitoring by DSC (FFM-DSC) is a powerful tool in carrying out investigations in this direction, and it can complement the information given by other techniques already used in the study of film formation such as small-angle neutron scattering  or 1H NMaxometry .


Combined sewer overflow structures (CSO) play an important role in sewer networks. When the local capacity of a sewer system is exceeded during intense rainfall events, they act as a “safety valve” and discharge excess rainfall run-off and wastewater directly to a natural receiving water body, thus preventing widespread urban flooding. There is a regulatory requirement that solids in CSO spills must be small and their amount strictly controlled. Therefore, a vast majority of CSOs in the UK contain screens. This paper presents the results of a feasibility study of using low-cost, low-energy acoustic sensors to remotely assess the condition of CSO screens to move to cost-effective reactive maintenance visits. In situ trials were carried out in several CSOs to evaluate the performance of the acoustic sensor under realistic screen and flow conditions. The results demonstrate that the system is robust within ±2.5% to work successfully in a live CSO environment. The observed changes in the screen condition resulted in 8–39% changes in the values of the coefficient in the proposed acoustic model. These changes are detectable and consistent with observed screen and hydraulic data. This study suggested that acoustic-based sensing can effectively monitor the CSO screen blockage conditions and hence reduce the risk of non-compliant CSO spills. In the UK, there is over 600,000 km of sewer pipes and over 70% of these are combined, in that they carry both wastewater and rainfall run-off from urban surfaces . Due to Water companies are regulated by the Office of Water Services (OFWAT), which is a non-ministerial government department that is responsible for ensuring that water companies offer adequate service to the customers at a fair price . With thThere are approximately around 31,000 combined sewer overflows (CSOs) in the UK . CSOs plThe key physical assets that constitute a CSO are the inlet and outlet pipes, which convey wastewater downstream. The diameter of these pipes, their slope and wastewater discharge determine the water level in the CSO chamber. If the wastewater level exceeds a certain threshold, e.g., in the case of a heavy rainstorm event or downstream blockage, then wastewater water spills through the CSO screen into the outlet pipe, into a receiving watercourse, e.g., local river or natural stream. The screen is installed so that spill flow can be screened for large solids. If the screen gets blocked, then an emergency overflow can bypass the screen  ,19:(1)Ljputed as ,19:(2)L¯Cair = (331.3 + 0.606 θ) m/s is the sound speed in air and θ is the temperature in degrees Celsius (°C) [d < 15 m , the recorded signal was dominated by the sound which was coming directly from the speaker. This sound was yet to be reflected by the screen multiple times to form a fully diffused sound field to carry useful information on the screen condition. For d > 100 m (0.29 s at θ = 20 °C), the acoustic signal was attenuated well below the background noise floor so that it could not be used in the analysis. It was found that a change in the air temperature had little or no effect on the measured sound pressure level time history ius (°C) . The choIn order to simplify the process of analysing the meaning of this graph, a least mean squares curve fitting method  was adopnt, nd is the distance, n is the integer in the time step, a0 is the SPL level at the intercept point when nd = 0 and b0 is the gradient of the curve. This method enabled us to identify the optimal values for the a0 and b0 coefficients for the best fit of a set of data. Here a0 and b0 have a clear physical meaning. The slope of the curve (b0) gives good indication of the conditions of the screen. A smaller absolute value of b0 indicates a smaller acoustic absorption of the screen, which results in a longer reverberation time in the CSO chamber. This means that the CSO screen condition is cleaner. On the contrary, a larger absolute value of b0 suggests that the CSO screen becomes contaminated with organic wastewater porous debris which absorbs sound better. This is an indicator that the screen is getting blinded. In this case, the acoustic attenuation in the chamber increases and so does the reverberation time. The coefficient a0 corresponds to the intercept point of the SPL curve when d is zero. This coefficient changes consistently with a change in b0 and it is an estimate of the maximum sound pressure level in the CSO. It is controlled by the power of the sound radiated by the speaker, the absorption area of the screen and walls in the CSO chamber and its volume. The coefficients 2 and 2300 × 4125 mm2. The findings obtained from these tests were used to inform the second phase tests. Phase 2 was to investigate the feasibility of in situ implementation of the proposed sensor within the CSO chamber with a screen size of 505 × 1480 mm2 over a period of six months. It should be noted that a typical CSO screen is a simple porous structure which is basically a stainless steel mesh. It consists of a 6 × 6 mm profile wedge wire to provide a larger surface area to enable a spill of a sufficient flow of wastewater filtering out any larger debris.There were two phases of field trial for the proposed acoustic instrument. Phase 1 involved two one-day experiments in two real CSO chambers with two static screens with dimensions 820 × 3380 mmFor phase 1 tests, an intrinsically safe version of the existing laboratory acoustic instrument was developed. This system consisted of four microphone arrays and a speaker, which were fastened on a wood panel, an IBM Lenovo Thinkpad tablet, a PCMCIA sound card (model: Digigram VXPocket 440) and a box of batteries with an amplifier circuit. This system and the method for its installation in phase 1 are shown in 2 screen. As can be seen from The first field trial site was located under a public highway located in West Yorkshire, as shown in 2, which was twice the size of the previous screen. The second field trial site was performed in a private highway. The section of land where the CSO was situated is privately owned and forms the main entrance to a garage and other businesses, as shown in b0 and a0 were estimated and plotted for the four CSO screen conditions, as shown in 0b gradually increased from −6.5 for blinded condition to −6.0 for fully cleaned condition in the first field trial. This corresponds to an 8% increase in the value of b0 from the case of the chamber with a fully blinded screen to that with a fully clean screen. For site 2 with a larger screen size, the values of b0 are higher compared to those measured on site 1 with the smaller screen size. For site 2 experiments, the value of b0 increases from −3.9 for the case with a fully blinded screen to −2.8 for cases with a fully cleaned screen, which constituted a 39% change. The results from the two sites confirm that the smaller absolute value of the coefficient b0 corresponds to a cleaner CSO screen condition, whereas a larger absolute value indicates the CSO screen is likely to be blocked by debris, which absorbs more sound, resulting in less acoustic reflections. These results also confirm that a change in the screen condition is clearly detectable acoustically. The proposed acoustic method seems more sensitive in the case of a CSO screen, which is larger in size. This makes physical sense because the larger the screen area, the larger the potential change in the acoustic absorption in the chamber which a screen with deposits is likely to provide. This is reflected in a larger change in the reverberation time and absolute value of the coefficient b0.In both field trials, each of the test conditions was recorded five times for validation purposes. The average of the sound pressure level data was calculated and curved, fitted using the LMS method (Equations (3)–(5)). The coefficients a0 and b0 on the flow conditions in the CSO chamber. Photographs of the screen condition studied in phase 2 experiments were obtained from regular manual inspection, which was carried out every two weeks. For the phase 2 field trial, a durable, intrinsically safe prototype of the acoustic instrument was developed to be left in the harsh conditions of the CSO chamber over a period of six months. This low-cost instrument was used to determine the dependence of the acoustic signature on a range of flow and screen conditions. This instrument can be linked to the existing telemetry, i.e., Hawkeye  technoloThe system used in phase 2 experiments consisted of an explosion-proof enclosure, which contained a control unit, power supply, microphone array and a speaker, as shown in The power supply lines were regulated electronically to 3.3 V for the control unit and microphone array and to 12 V for the power amplifier. These units were implemented on the same circuit board. In order to reduce the risk of a surge in the current in the external cable due to a malfunction in the electronics module, Zener barriers were placed on the control unit’s board, limiting the voltage going to the speaker to 12 volts  and the voltage going to the microphone array to 5.6 volts . The maximum current drawn on the speaker was limited to 250 mA. In addition, both voltage regulators had short circuit protection to prevent excessive currents from reaching the microphone array and the speaker in case of malfunction of the system. If a short circuit occurred, then the circuit would be instantaneously disconnected from the power supply.The speaker was hermetically sealed in an airtight plastic cylinder as shown in 2 and a Hawkeye telemetry system [y system ,30 to mea0 and b0, except the times when the water level in the chamber changed considerably, affecting the screen condition. Some interesting observations from the change in the values of the coefficients a0 and b0 can be made. This change is illustrated in a0 and b0 measured over the six-month period. This figure also presents the water depth data, which were recorded at 15-min intervals with the Hawkeye telemetry system. The water level data are helpful to interpret the observed behaviour of the coefficients a0 and b0. During a 14-day measurement period which started on the 18th of January, there was not much rain around the instrumented site. Therefore, the ambient (dry weather flow) water level varied little between 70 mm and 100 mm . In the case of the larger screen, the corresponding increase in the absolute value of this coefficient was 39%. These changes are clearly detectable with the proposed acoustic method. This acoustic instrument, installed to monitor a plurality of types of CSO, will require initial calibration—a straightforward process which can be automated and completed remotely.In this paper, the feasibility of novel acoustic instrumentation to detect changes in the combined sewer overflow (CSO) screen condition was studied. The results obtained from two field trials (phases 1 and 2) deployed in urban residential areas provide an informed decision when the screen needs to be cleaned. The controlled field experiments in phase 1 suggest that the change between the clean and fully blinded CSO screen conditions is detectable with the proposed acoustic method. In the case of the smaller screen (site 1), this change was reflected in the 8% increase in the absolute value of the coefficient b0 in Equation (3) and a 5 dB reduction in coefficient a0. These coefficients have recovered to their ambient values after the screen returned naturally to its original condition. In phase 2, the data from the acoustic experiment in the field were compared against the Hawkeye water level data obtained in the same CSO chamber simultaneously, albeit at a different sampling interval. The acoustic sensor head worked properly over a period of six months. The reproducibility of the acoustic sensor data during the dry weather flow period was found within ±2.5%. This level of repeatability, together with obtained experimental evidence, suggest that the system can reliably detect changes in the conditions in the CSO screen which were caused by a rapid change in the water level. A deposition of debris on the CSO screen by a short-term storm event caused a 30% increase in the absolute value of coefficient The results also show that the sensor can detect water level changes which occur over a period of time, which is longer than the sensor sampling interval. A significant increase in the water level causes a measurable drop in the sound pressure level in the chamber and reduction in the acoustic attenuation. These results make physical sense. It was found that the acoustic sensor performance returns to normal after the level of water drops to its ambient dry weather conditions. The speed of the acoustic measurements (a few seconds) and sensor’s ability to quantify the screen condition remotely have the potential to be at least two orders of magnitude less costly than traditional site visit and visual inspection methods. The results from phase 2 experiments show that the screen condition can naturally recover after a short-term storm event, which usually causes some debris deposition. This information is novel as it has not been observed before. This implies that the deployment of such sensors can help to reduce unnecessary site inspection visits, resulting in a reduction of operational costs and associated environmental impact. The proposed instrument can be improved further by pairing it with an energy harvesting system  and integrating it with the wireless network, e.g., the Hawkeye system.


Background and aim: Assessment of dentofacial asymmetries and other discrepancies that can affect the horizontal reference lines should be considered initially as a part of the esthetic diagnosis. Some variations of facial asymmetry are not considered an esthetic liability. So the aim of the present study is to determine a layperson’s preference regarding transverse occlusal plane (TOP) orientation in fabrication of a complete denture.Materials and methods: A total of 100 subjects who are edentulous and have enrolled for complete denture fabrication were selected. Photograph of the patient’s face was obtained from the frontal perspective on the day of try-in. The image obtained was edited to orient the occlusal plane in three different cants, zero degree, two degrees, and four degrees to the inter-pupillary line (IL) and presented to the patient. The obtained results were statistically analyzed.Results: The observed data was analyzed using Friedman’s test and Wilcoxon test was used for comparing ordinal data between groups. There was a statistically significant difference in acceptance depending on angulation, χ2(2) = 183.2, p = 0.0001.Conclusion: A cant of two degrees is not perceived by the subject but some subjects’ preference of occlusal plane may be altered according to the commissural canting which cannot be incorporated in complete denture fabrication. The transverse occlusal plane (TOP) when viewed from a frontal perspective should be parallel to the facial horizontal reference lines such as the inter-pupillary line (IL) and the commissure line (CL) to maintain facial harmony. Lack of parallelism among the TOP, CL, and IL can be attributed to different causes. The presence of an elevated labial commissure at rest or alar base on one side is often an indication of vertical skeletal asymmetry. Conditions for each patient should be individually diagnosed. Restorative treatment alone can also be a solution depending on a particular situation and the patient’s individual needs. Assessment of dentofacial asymmetries and other discrepancies that can affect the horizontal reference lines should be considered initially as a part of esthetic diagnosis.Laypeople prefer some degree of TOP inclination in patients who present a lip CL cant. The acceptable degree of canting should be assessed on an individual patient basis. Therefore, the purpose of the study is to determine a layperson’s preference regarding TOP orientation in fabrication of a complete denture.The study design was a double-blinded observational trial. The study plan was approved by the institutional ethical committee. Participants were explained about the nature of the study and written informed consent was obtained. A total of 100 subjects who are edentulous and have enrolled for complete denture fabrication were selected from the outpatients in the Department of Prosthodontics and Crown & Bridge, JSS Dental College and Hospital, Mysuru. Conventional complete denture fabrication procedures were followed to fabricate upper and lower complete denture and on the day of try-in of the complete denture, photograph of the patient’s face was obtained from the frontal perspective. The image obtained was edited to orient the occlusal plane in three different cants, zero degrees Figure , and fouThe data were analyzed using the statistical package for social sciences (SPSS) for Windows 26.0 . The descriptive data show mean, standard deviation (SD) and were used for comparison between the groups. The observed data were analyzed using Friedman’s test and Wilcoxon test was used for comparing ordinal data between groups. Confidence intervals were set at 95% and values of p < 0.05 were interpreted as statistically significant. There was a statistically significant difference in acceptance depending on angulation, χ2(2) = 183,2, p = 0.0001 (Table According to Glossary of Prosthodontic Terms 9 (GPT 9), an occlusal plane is defined as the average plane established by the incisal and occlusal surfaces of the teeth; it is not a plane but represents the planar mean of the curvature of the surfaces . The posThe faulty orientation of the occlusal plane will jeopardize interaction between tongue and buccinator muscles. Where the occlusal plane is too high, the tongue cannot rest on the lingual cusps of the lower denture and thus prevents its displacement. It also forces the tongue into a new position that is higher than its normal position causing the floor of the mouth to raise and create undue pressure on the border of the lingual flange, resulting in partial loss of border seal. There is also a tendency for the accumulation of food in the buccal and lingual sulci. An occlusal plane that is too low could lead to tongue and cheek biting .In the anterior region, the vertical height of the occlusal plane is governed by esthetic requirements and less frequently by functional demands . The antIn the present study frontal photograph of the subject was obtained during try-in and was edited using Adobe Photoshop. Three images of the subject with a modified occlusal plane were presented to the subject. Subject perception of the occlusal plane and his/her preference of cant were recorded.The image manipulated to create a two-degree occlusal cant was esthetically acceptable for 87 subjects. These results coincide with other research that has observed that occlusal canting is not perceived by laypersons unless it exceeds two or three degrees. Kokich et al.  found thPadwa and Kaiser  have shoOlivares et al.  suggesteSilva et al.  found thRehabilitation of completely edentulous individual is a challenging job for a restorative dentist when the esthetic anticipation of the patient is high. A cant of two degrees is not perceived by the subject but some subject’s preference of occlusal plane may be altered according to the commissural canting which cannot be incorporated in complete denture fabrication. So it is the responsibility of the restorative dentist to educate the patient regarding the same in cases of extreme canting to fabricate a denture which has a balance between esthetics and function.


In a high-speed single-molecule experiment with a force probe, a protein is tethered between two substrates that are manipulated to exert force on the system. To avoid nonspecific interactions between the protein and nearby substrates, the protein is usually attached to the substrates through long, flexible linkers. This approach precludes measurements of mechanical properties with high spatial and temporal resolution, for rapidly exerted forces are dissipated into the linkers. Because mammalian hearing operates at frequencies reaching tens to hundreds of kilohertz, the mechanical processes that occur during transduction are of very short duration. Single-molecule experiments on the relevant proteins therefore cannot involve long tethers. We previously characterized the mechanical properties of protocadherin 15 (PCDH15), a protein essential for human hearing, by tethering an individual monomer through very short linkers between a probe bead held in an optical trap and a pedestal bead immobilized on a glass coverslip. Because the two confining surfaces were separated by only the length of the tethered protein, hydrodynamic coupling between those surfaces complicated the interpretation of the data. To facilitate our experiments, we characterize here the anisotropic and position-dependent diffusion coefficient of a probe in the presence of an effectively infinite wall, the coverslip, and of the immobile pedestal. As a consequence, the fluctuations in the protein’s instantaneous position are filtered with a time constant of 3. Rigid spacers couple the motion of the protein’s ends tightly to the position of the bead, thereby increasing the bandwidth and precision of the experiment.A protein under tension exhibits both entropic and enthalpic elasticity, a behavior that can be measured by observing the elongation of a single molecule while applying mechanical force. In such an experiment, the molecule is placed between two substrates, at least one of which is part of an elastic transducer through which forces can be delivered, for example an optically trapped, micrometer-sized bead. To avoid non-specific interactions between the protein and the substrates to which it is attached, the protein is usually secured through long, flexible DNA or PEG spacers4. The protein was instead stretched directly between a diffusing probe—a 1 μm-diameter plastic bead to which force could be applied by optical tweezers—and an immobile glass pedestal—a 2 μm-diameter bead fixed to the coverslip. The protein’s ends were attached to the two beads through distinct, short, and relatively inelastic linkers. A similar approach was taken in previous work that studied the force-extension of whole titin molecules and of the molecular motor kinesin with optical tweezers6. Force-extension studies with atomic-force microscopes also sometimes avoid flexible spacers, albeit usually at the expense of non-specific anchoring of the target protein to at least one of the confining surfaces7.We developed a novel single-molecule assay that did not require long, flexible spacers4. Determining the entropic and enthalpic stiffness of the protein is crucial for our understanding of the molecular basis of mechanotransduction by the inner ear. Human ears can detect sounds at frequencies up to 20 kHz, and some bats and dolphins have a hearing range exceeding 200 kHz. The protein machinery that underlies hearing must therefore be capable of responding to very fast stimuli that likely produce mechanical responses far from thermal equilibrium. For two reasons, this high-frequency behavior has not been explored through single-molecule experiments. First, in the presence of flexible linker molecules, high-frequency force stimuli are largely filtered before they can elongate a protein of interest. Second, even in the absence of flexible linkers, the mechanical response of a protein is filtered owing to the drag on the bead and the stiffness of the optical potential that confines it. If these filtering effects are not too large compared to the time constant of the protein’s response, and if the diffusion coefficients at critical locations in the experimental volume are known, it is nevertheless possible to compensate for the filtering. In this study we characterize the anisotropic and position-dependent diffusion coefficient of a bead in our single-molecule assay in the presence of an effectively infinite wall, the coverslip, and of an immobile spherical obstacle, the pedestal. The results should facilitate analysis of high-speed studies of single-molecule forces relevant to auditory transduction.Our method allowed us to characterize the equilibrium mechanics of protocadherin 15 (PCDH15), a protein whose properties implicate it as part of a molecular spring important for hearing8 . We recorded the photodiode's total signal and recovered the position of the probe by subtracting the offset caused by the pedestal. The position signal after compensation was nearly zero  voxel within this volume. Such high spatial resolution is crucial for the constrained geometries in our single-molecule experiments: our data clearly demonstrated that in close proximity to the coverslip and pedestal, the diffusion constant dramatically changed over the dimensions of the trapping volume. The spatial resolution of our technique was limited by the precision with which we could determine the probe bead’s position, slightly below 1 nm along each axis, and by the duration of the diffusion measurement, for each voxel had to be visited sufficiently often to provide statistical significance. Although the resulting three-dimensional spatial map of diffusion constants was limited in spatial extent by the width of the trapping volume, larger volumes could be explored by displacing the optical trap in steps smaller than the width of the trapping volume and recording partially overlapping diffusion maps that were subsequently fused.Our method constitutes a significant improvement in spatial resolution over previous approaches. Although those methods average over the entire trapping volume accessible to the bead’s diffusion, typically on the order of 10 nm wide and 100 nm deep, we measured the diffusion constant in each 125 nmx-axis. Because we were therefore mainly interested in how the associated diffusion constant Dx changed with extension from the pedestal, we moved the optical trap along that axis in 100 nm steps and determined the diffusion constant at each position . This value plateaus beyond a characteristic autocorrelation time Voxel size contributed to the resolution of our measurements, for smaller voxels permitted a more granular mapping of the local diffusion constants. However, this benefit had to be balanced with the need to obtain sufficient data points from each voxel, the probability of which decreases as voxel size declines17κ is the spring constant of the optical trap along the relevant axis, a the displacement from the trap's center, t the time lag, γ the viscous drag coefficient of the probe given by Stokes' law, and D the local diffusion constant. kB and T are respectively the Boltzmann constant and thermodynamic temperature. For the ratio to remain small such that essentially free diffusion occurs, the time lag had to be much smaller than the characteristic drift time τ and τD determines the timescale at which the probe’s motion deviated from free diffusion. If τ < τD, as was the case in our system for excursions of less than 150 nm from the trap's center along any axis, then the influence of the gradient force on the mean squared displacement was negligible. If instead τ > τD, then the measured value would have exceeded that of a freely diffusing particle for intermediate time lags.A small time lag was also critical for another reason: the gradient force owing to the optical trap could result in drift. For a starting position far from the center of the trap, the gradient force causes the mean squared displacement to grow faster than free diffusion and therefore complicates measurements. The influences of the gradient force and of free diffusion can be compared by the relative mean-squared-displacement contribution5 s−1. A weak optical trap was formed within the sample chamber by focusing a 1064 nm laser beam with a high-numerical-aperture water-immersion objective lens.The Supplementary Information for this article includes detailed descriptions of the experimental apparatus and optical system. In brief, the photonic-force microscope was capable of measuring the position of a micrometer-sized probe bead with sub-nanometer precision for an integration time of 1 μs and sampling at 10The three-dimensional position of the probe confined within the weak optical trap was obtained from the interference on a quadrant photodiode of light scattered forward from the probe with unscattered light. To hold the probe at a constant displacement from the center of weak optical trap, as was required for the correction owing to the pedestal, an optical trap was formed by an 852 nm laser. The position of this relatively strong optical trap with respect to the weak trap was adjusted by means of a beam-steering lens in the beam path of the strong laser.Supplementary Information.


The need to cope with life concerns may drive an individual to resort to high‐risk behaviours. This study aimed to determine the relationship between health concerns and high‐risk behaviours.A cross‐sectional study.We sampled 926 Medical Sciences' students from the North of Iran from September–December 2017 using the stratified sampling method.The most and less common high‐risk behaviour was physical inactivity (97.5%) and high‐risk sexual behaviour (15.7%), respectively. In multivariate logistic regression analysis, participants' concerns about human sexuality , injury prevention and control , nutrition  and emotional health  increased the odds of risky behaviours. Among Medical Sciences' students, health concerns are linked with risky behaviours. The result of this study can be used to develop relevant interventions targeting mental health to reduce risky behaviour among youth. The frequency of alcohol and illicit drug use in the same group during the lifetime was found to be 11.9% and 8.8%, respectively , who are represented widely by university students, are believed to have higher tendency to adopt unhealthy behaviours than the other age groups , 90% power (β = 0.01) and 0.13 correlation coefficient between mental health and high‐risk sexual behaviour of a former study , as main strata, was obtained by dividing the total number of the students in that school by the total number of students in the university. Then, the number of samples allocated to each school was categorized based on the number of the male and female students in each school, alongside with their respective academic year. In turn, some classrooms in each school were selected randomly with the assistance of the random number table. Finally, in each classroom, all of the volunteer students who were present on the day of the research team's visit were invited to complete the self‐administered instruments. The survey was conducted by a trained reproductive health researcher. The sample size was determined to be 970 subjects with a 95% confidence level  for subscales of intentional and unintentional injuries, tobacco use, alcohol and other drug use, high‐risk sexual behaviours, body weight and dietary behaviours and physical activity were 0.83, 0.73, 0.71, 0.64, 0.85 and 0.82, respectively, p < .001, with an interval of 2 weeks  if her/his response was positive to at least one question in each domain indicating risky behaviour according to the criteria established by the Centers for Disease Control and Prevention Kann, . For exaα, ranged between 0.68–0.89 for 12 subscales and 0.96 for the total inventory. The Kappa coefficients of all items were between 0.40–0.75 or above 0.75 which indicated good to excellent agreementions of the inventory , were established for the Youth Risk Behavior Surveillance System questionnaire and Cronbach's α 0.94 ICC 0.74, (p < .001), for the Adolescent Health Concerns Inventory as well.The reliability and the consistency of these instruments in the present project were assessed with participation of 20 university students. In this way, Cronbach's 2.3t test. Then, a multivariate logistic regression model was administrated with the variables that were related to the high‐risk behaviours. Statistical significance was based on a p < .05. Analyses were performed using Statistical Package for Social Sciences for Windows version 16.0 (SPSS Inc.).Descriptive findings were reported using proportions and means with standard deviations. To identify whether high‐risk behaviours (as dependent variables) are more frequent in Medical Sciences' students who experienced health concerns, we first conducted the bivariate analysis using the chi‐square test and independent 3Of the 970 completed questionnaires, 44 were eliminated due to incomplete and inadequate replies to the questions (response rate = 95%). Among the respondents, 56.2% were female, and the mean age of the participants was 19.19 ± 1.97 years. Most of the participants (52.1%) were studying for Bachelor's degree in Science. Most of them were single (92.1%), and 45.9% lived in dormitories. The socio‐demographic characteristics of the participants are shown in Table p < .05), whereas physical inactivity was reported more among females , followed by unintentional injuries  and intentional injuries . Intentional and unintentional injuries, smoking and tobacco use, alcohol and drug use and high‐risk sexual behaviours more frequently occurred among males . As the goal in any data analysis is to extract from raw information the accurate estimation .In bivariate analysis as showed in Table 4University students are important targets for the promotion of healthy behaviours of the adult population. In this study, high‐risk behaviours such as intentional and unintentional injuries, alcohol use and high‐risk sexual behaviours were higher in male students. Many studies in line with our study showed that high‐risk behaviours are gender‐related and multiple risk‐taking behaviours more common in men  and high‐risk sexual behaviours is in line with the other studies  so the participants of the present study in MAZUMS were students from all over the country and from different ethnic groups. This could increase the generalizability of the findings as the results would be more acceptable and representative if the samples are taken from diverse localities with students of diverse backgrounds, although the results may not be generalized to non‐medical sciences' students. Comparing the gender composition of the students in the present study  with the national statistics  were not investigated. Moreover, the results of this research are only generalizable to Medical Science students. Fourth, there is a possibility of interview bias even though the interviewer attempted to read from the questionnaire when asking the question and avoid facial expressions of change voice and notations during the interview. Confounding bias was controlled by using the regression analysis. Final limitation of this study refers to the sampling method. In the final step of sampling, all of the volunteer students who were present on the day of the research team's visit were invited to complete the self‐administered instruments. This not‐randomly participation of the students may have increased the likelihood of selection bias, but this was inevitable as if we asked students to answer these culturally sensitive questionnaires according to the randomized selection in each class, it might increase the information bias, because they might be wondering why I was chosen to answer? However, based on the randomly selection of the classrooms in each strata, the students have an equal chance of being included and the selection bias can be limited.6Medical Sciences' students serve as role models for the other students and the transition from being a university student to being a good healthcare practitioner  requires committed role models. So, the findings of this project by investigating the university students' concerns in predisposing them to risky behaviours have some implication in practice and policy. This study has shown various prevalence rates of risky behaviours and health concerns among Medical Sciences' students at MAZUMS; hence, university‐based health education and promotion programs are required. Also, these findings illustrate the need to consider health concerns as predisposing variables when investigating the high‐risk behaviours of young people. Our study points to the necessity for screening, prevention and interventional programs targeting mental health in university students Further studies are recommended to reach an in‐depth understanding of how Iranian university students feel towards life in general, how often they feel concerned and how intense their concerns are. It is demonstrated that there is a large discrepancy in the literature about the prevalence and related factors of some high‐risk behaviours such as dietary behaviours and physical activity. This issue may be resulted from that there is not an acceptable national standards to facilitate comparison between countrywide studies. Also, it is not entirely clear to what extent high‐risk behaviours and health concerns can seriously endanger the health of young people? So, it is important to develop the culture‐based instruments for measuring high‐risk behaviours and health concerns with a qualitative approach and through in‐depth interviews with university students in the future. In this way, the roles of new emerging social determinants of health such as social media are recommended to be in the spotlight.The authors declare that they have no conflict of interest.All authors made a substantial contribution to writing of the paper draft and met the four criteria for authorship recommended by the International Committee of Medical Journal Editors.All procedures performed in the studies involving human participants were in accordance with the ethical standards of the institutional and/or National Research Committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The Ethics Committee of MAZUMS approved the study , and the students were informed about the topic, purpose and procedure of the study. All volunteer students were provided informed written consent before participation and were assured of the confidentiality of the data. In this way, a covered box was designed to collect anonymous questionnaires and reassure students that the information was confidential.


This is as a result of some unique features it has, such as very low power requirements as well as possibility of being used as passive and even active sensors. In recent years, RFID has found increased use on the human body , in healFactors such are comfort and conformity are essential for body mounted tags, which, fortunately, are provided by inkjet‐printed tags on tattoo transfer paper , due to Considering the above, it is, therefore, necessary to assess the limits of body‐mounted tags to understand the limits of use. The tag robustness was tested based on performance during normal daily activities, after gym activities, after showering and the effects of sweat. Part of this work has been presented in .2oC.The RFID tag was simulated on skin using Computer Simulation Technology™ Microwave studio. This software enables the designer to model and simulate the RFID over a frequency range and assess the quality of the impedance match to the application‐specific integrated circuit (ASIC) (or RFID transponder) used. The tag was modelled on a four‐layer phantom Figure The tag design, shown in Figure The fabrication was done with conductive silver nano‐particles ink , 13 inkj3The tag was then tested under various conditions such as normal 8‐h working day as well as during exercise activities in a gym. For the full work day tests, the measurements were recorded every 30 min for the 8 h. Due to the temporary nature of this tag, a minimum of 8‐h functionality under non‐stressful conditions was chosen as a benchmark to determine satisfactory performance. The measurements for the robustness test for the exercise activities were taken after 20 min of various gym activities. The tag was placed on the torso of the volunteer in order to guarantee sufficient contact with sweat and also maximize the effect of body motion on the tag during the exercises. The performance of the tag when worn to sleep for 6 h was also assessed. All measurements were taken using Voyantic Tagformance kit . This isIt was also sought to determine if there is a specific effect of sweat on the deterioration of the tag or if the observed deterioration was simply due to wear and tear. Consequently, a more regulated experiment was set up in order to remove the effect of movements and, consequently, friction on the tag. This experiment would also help to establish if sweat had any effect on tag durability as against ordinary water (moisture). In order to achieve this, a saline solution was made to have a close similarity to sweat. The salt concentration in this solution was obtained from . Of the 4Figure The first measured read range of the tag was 0.6 m. While there was no decrease in the measured read range during the first 180 min, subsequently, there are observed drops in the read range obtained from the tag. These drops in the read range could be attributed to wear and tear on the tag due to body movements by the user. This could lead to the weakening of the attachment of the chip to the tag as well as introduction of creases, which could lead to an increase in tag impedance. The effect of this is increased mismatch between the antenna and the chip leading to a decrease in the read range. It is necessary to note that the apparent increase in the read range noticed in the early stages of the measurement could be attributed to variations in the placement of the tag during the measurement as slight changes in the separation between the tag and the reader antenna would result to an apparent increase in the read range. The Voyantic Tagformance kit operates by measuring the backscattered power from the tag under test, while the transmitted power from the kit is used to set the threshold power of the chip in relation to frequency. With these values, the read range can then be deduced by the equipment utilising Friis equation because the associated losses from the cable and other sources have been removed prior to calculations during calibration. Tests indicate that a 1‐cm change in tag location after calibration would lead to about 20‐cm variation in the read range measured. Consequently, care was taken to avoid movements during the measurements. The tag was worn on the forearm to sleep but had suffered severe abrasion leading to the cutting of the feedline of the tag [see Figure The extended duration (8 h) of the tag's functionality is not indicative of an absolute test of robustness when considering its requirement for use in harsh environments such as during gym exercises. Consequently, a performance test was carried out during gym activities, which lasted for 20 min, which included 10 min on the treadmill and 10 min using the elliptical trainer. The before and after pictures of this experiment are shown in Figure Read range measurements afterwards showed a decrease in the read range when compared to the earlier measurements. Observation after the gym exercises shows the appearance of creases across the tag. However, because of the rigorous nature of the exercise and the associated movement of the torso, the creases were more pronounced than what was noticed in the earlier 8‐h test and also appeared in shorter time. As noted earlier, these creases have the effect of weakening the adhesion between the antenna and the chip as well as causing an increase in tag impedance. Even though the initial read range was measured to be about 70 cm, the measurement after exercising at the gym showed a reduction by about 13 cm, as seen in Figure Prior to assessing the effects of sweat, measuring points were defined on the tags according to Figure Point‐to‐point resistance measurements were carried out at these points before the start of the experiment and then at 5‐min intervals for 30 min using the order: 1–2, 1–3, 2–4, 3–9, 4–10, 3–10, 4–9, 5–6, 6–7 and 7–8. The averages of the resistances were taken for every measurement, and the results are plotted in Figure The results of the point‐to‐point resistance measurements indicate that no notable dissimilarity can be observed between the two tags. This observation would lead to the conclusion that the degradation of the tag during the gym activities had more to do with motion and friction than the effect of subjection to sweat. The first 15 min of the measurement where both tags were intact gave the most confidence in the results. This is because after this point, cracks were observed on both tags, which resulted to increase in resistance values. In addition, there was also folding of the paper underneath the polymer layer, where the conductive ink was deposited due to exposure to both liquids.In order to assess further the effect of exposure to liquid on the tag, it was worn during a shower for 10 min. This had the effect of exposing the transfer tattoo tag to water as well as bathing soap. Caution was taken to avoid exposing the tag to vigorous rubbing. Figure Figure 5In this work, the robustness tests were conducted to assess the durability of an inkjet‐printed epidermal RFID tag. These tests carried out over an 8‐h period. Read range measurements showed a non‐uniform step decrease in the tag read range, but tag operation was continuous throughout the duration of the test. However, the tag was badly damaged when worn overnight due to a cut on the feedline. The tag still functioned after gym exercise, though it showed signs of physical degradation. Further tests showed that the decrease in the tag read range was more as a result of wear and tear due to mechanical friction than being subjected to sweat, as DC resistance measurements showed no notable variation between exposing the tag to sweat  and to water for a period of 30 min. Finally, exposing the tag to water and bathing soap during showering resulted in no decrease in the tag read range. These results have gone on to show that tags such as the one presented here have shown some promise for use on the human body. However, future body‐mounted inkjet‐printed tags would require more robustness in the conducting pattern while striving to maintain skin comfort.


Ormia ochracea fly, which detects sound wavelengths much larger than its hearing organ. A typical ormia-based MEMS directional sound sensor possesses two coupled wings that vibrate in response to sound according to a superposition of its two main resonant modes, rocking and bending. Vibrations are transduced into electronic signals by interdigitated comb finger capacitors at each wing’s end along with a capacitance measuring circuitry. A sensor designed to exhibit resonant modes closely placed in frequency, enhancing their coupling, was operated with a closed cavity behind the wings. Simultaneous and independent measurements of electronic signals generated at each of the single sensor wings were used to determine incident sound direction of arrival (DOA). DOA was found proportional to the phase shift between them and to the difference over the sum of their amplitudes as well. Single sensor phase shift DOA measurement presented a resolution better than 3° for sound pressure levels of 25 mPa or greater. These results indicate that a single sensor operating in closed-cavity configuration can provide hemispherical unambiguous direction of arrival of sound waves which wavelength is much larger than the sensor size.MEMS acoustic sensors have been developed to mimic the highly-accurate sound-locating system of the  There are many insects that rely on phonotaxis in order to complete their reproductive cycles5. Usually the process involves parasitism of different species’ male hosts by the larvae deposited on or near them. Males give off their location by emitting mating calls, directed to the female individuals of their own species, but those are also heard by female individuals of the parasitic species. This happens in low light conditions, in order to avoid visually based predators, therefore, directional sound sensory capabilities are required for both species7.For many animal species, perceiving the direction under which a sensorial stimulus occurs is key for survival and reproduction. Considering auditory stimuli, cues used for these tasks rely on small differences in the pressure disturbances detected by physically separated sensory organs, either in amplitude, time of arrival or both. When the animal size is comparable to the sound wavelength in air, the required physical separation capable of making the differences perceivable by the nervous cells, processing or transmitting the detected stimulus, is naturally assured. For species of much smaller dimensions, the physical impediments of having sufficiently separated sound sensors pushed evolution towards using different mechanisms of detecting and processing the sound waves much needed for their basic survival tasksOrmia ochracea, which show the ability of finding the chirping host for their larvae with high accuracy, despite its sensory organ being much smaller than the wavelength8. Miles et al.10 found that the mechanical coupling between two tympana mediated by a semi-rigid cuticle was responsible for bringing those stimuli amplitude and time differences to within reasonable working ranges for the neuronal cells involved, enabling the parasitic fly to acoustically locate the host for its larvae. As a consequence of these findings, research and development of acoustic sensors based on micro-electro-mechanical systems (MEMS) mimicking the directional sound sensory capability of the fly’s hearing organ in a small form factor have been explored23.There are a number of studies concerned with one species of fly, 9. On the female fly hearing organ, each of the tympanal membranes present exclusive bilaterally-symmetric mechanoreceptive structures, the auditory apodeme and the bulba acustica8. Those are responsible for the transduction of each tympanal membranes mechanical vibrations into neuronal electrical pulses. This way, mechanical displacements of each tympanal membrane resulting from acoustic coupling are simultaneously and independently encoded. Likewise, on the MEMS directional acoustic sensors a transduction mechanism must be employed to convert each of the wings’ vibrations into electronic signals.A typical Ormia-based MEMS directional sound sensor consists of two wings, connected by a bridge in the middle and the entire structure is connected to a substrate using two torsional legs. The structure exhibits two vibration modes: rocking, in which wings oscillate out of phase and bending, presenting in phase oscillations. When an acoustic pressure wave is incident on the sensor, the response of the mechanical structure is a linear combination of its vibration modes17, as well as the one based on fiber-optic low-coherence light interferometry19 both take advantage of the high-sensitivity, high-resolution provided by photonic techniques, however at the cost of a higher complexity optical mounting or signal processing. An alternative technique was explored using an integrated PZT film deposited on the sensor die20. This was found to be less sensitive than other techniques at the expense of increased complexity on the microfabrication process by adding the piezoelectric film deposition, polling, patterning and etching. In order to simplify the fabrication process our group opted to employ interdigitated comb finger capacitors integrated at the edges of the wings15. These are patterned and etched during the same processes of patterning and releasing the wings. A capacitance measuring circuit completes the full transduction from mechanical displacement to electronically measurable signal. The combs were designed using a fishbone architecture to increase structural rigidity while attaining appreciable capacitance change22. Similar transduction mechanism was also employed by other research groups21 in their devices.Several transduction mechanisms were envisioned. The optoelectronic mechanism, based on the angular position of a monochromatic light beam diffracted off a grating 21 or by using two MEMS directional sound sensors22. The latter was operated at the bending mode under sound interaction on both sides of the wings, similar to that of a pressure gradient microphone, giving a cosine directivity pattern. In order to extract the acoustic wave direction of arrival, such arrangements were needed to eliminate the unknown sound pressure, in the first one, or the angular ambiguity, as in the second. In this paper, in close similarity to the fly’s hearing organ, the use of a single MEMS sensor for accurately determining the direction of sound is demonstrated.Aiming at finding the direction of arrival of acoustic stimuli, previous research works employed either a MEMS directional sound sensor along with a calibrated microphone2 wings, coupled by a 2.7 mm long bridge. Two legs, perpendicular to the bridge, connect the entire mechanical structure to the substrate and also act as torsional springs. A micrograph of the device surface is shown in Fig. The MEMS sensor employed in this paper consists of two 1.2 × 1.5 mm23. SEM images detailing the fingers are provided in the Supplementary Fig. The fabrication used a 400 μm-thick silicon-on-insulator (SOI) wafer, in which a 25 μm-thick device layer sits on top of a 1 μm-thick oxide layer. The comb finger capacitors were fabricated at the edges of the wings and details of the comb structure can be found in Downey. for the fly’s hearing organ using a lumped parameter coupled system9. The motion of each wing under steady-state harmonic excitation can be treated as a linear combination of two natural modes of vibrations, the rocking mode and the bending mode. The rocking mode motion results from pressure differences on the two wing’s surfaces due to the oblique incidence of the sound waves. The two wings will suffer displacements in opposite directions twisting the two legs, ensuing a phase shift of π radians between them. Therefore, this mode behaves as if the bridge were rigid. The bending mode is excited by the pressure of the incident sound with wings moving in phase by bending the bridge connecting them. The actual motion of the wings resulting from acoustic excitation at a given angular frequency ω will be a linear combination of these two natural modes. The degree of coupling between the two modes depends on their proximity in frequency as well as their bandwidths. The resulting displacement for each of the two wings can be expressed as9The mechanical response of the MEMS sensor to incident sound may be modeled similarly to the approach developed by Miles et al.5, taking into account the sound wavelength is much longer than wings’ separation, the amplitudes and phases of normal modes can be approximated asBy solving coupled differential equations of motion as detailed in Miles et alIt can be seen in Eq.  that botentclass1pt{minimaEven though the modal amplitudes mentclass2pt{minimmentclass2pt{minimThe auxiliary signal amplitudes are multiples of mentclass2pt{minimEquations  and 7)  7) show 22.The sensor die was glued on a 2.5 mm thick circuit board over a milled-through hole as schematically shown in Fig. Figure Thus, the rocking mode keeps the air volume in the cavity to be nearly the same while the bending mode compresses it. The increased spectral bandwidth observed on the bending mode response is associated with the losses induced by the viscous squeezed film damping as the two wings press the air volume in the cavity and force it through the gaps on the die trenches and between the two PCB boards. The relative proximity of bending and rocking mode response frequencies observed in Fig. 14. In order to minimize the sound coupling from backside of the wings, a back plate was used. Closing the back of the sensor, increases the bending mode damping coefficient Observing Fig. entclass1pt{minima24 was employed. This IC is capable of simultaneously measuring either 6 single-ended or 3 differential capacitances generating a 32-bit digital output associated with each reading. The capacitance readings in the registers may be dynamically updated at up to a 50 kHz sample rate. The PCap04 was able to provide, with negligible crosstalk, the simultaneous readings of the capacitance values associated with each wing. Additional circuitry was needed to convert the two 32-bit digital words associated with each wing displacement to analog signals through a digital-to-analog conversion. This operation would have to be done fast enough to avoid loss of information or aliasing resulting from sampling the capacitance signal at a frequency smaller than the Nyquist lower limit. Since the frequencies of the sensor rocking and bending resonances were designed to be below 2000 Hz, the sampling rate of the IC is found to be adequate for reproducing the signal, producing roughly about 30 samples per period. The complete capacitance readout circuit assembled consisting of a 32-bit ARM Cortex SAM3X8E microcontroller (Arduino Due) integrated with PCAP04 is schematically shown in Fig. Pursuing the direction of arrival determination from an acoustic stimulus employing a single MEMS sensor requires the ability of simultaneously and independently detecting mechanical displacements associated with each of the wings. In order to do that, an integrated circuit, PCap04, from ACAM Messelektronik, now ams AGThe microcontroller has two, on chip, 12-bit digital-to-analog converters (DAC) used to output as voltage signals the 32-bit capacitance readings performed by the PCAP04 integrated circuit. Communication between the microcontroller and the capacitance-to-digital integrated circuit was established through SPI connections available at both ends. The microcontroller on-chip DAC did not present high current fan out capacity and the addition of a buffering stage was needed. Moreover, the signal was still noticeably jigged (stepwise continuous) as a consequence of the DAC process and sampling frequency.Therefore, an active DC block high-pass filter and an active 2nd order Butterworth low-pass filter as shown in Fig. The sensor with the closed back along with the circuit board were mounted to a post and connected to a turntable inside an anechoic chamber, as schematically shown in Fig. A fixed loudspeaker facing the turntable was used as the sound source which was excited using a function generator via an audio amplifier. The frequency response of the sensor was measured at two fixed angle positions (± 45°), by sweeping the frequency from 500 Hz up to 2000 Hz as shown in Fig. In accordance to what was expected, the bending mode sensitivity is not affected by the angular sense (positive or negative) of incident sound wave while the response at the rocking mode is strongly affected by which side the sound is incident upon. Also worth noting is the close resemblance of the spectral responses originated on the signal processing circuit Fig.  with thaFigure Figure g to Eq. , is rela–2 was observed for the ratio of difference over sum. These results show that either technique can be used in determining the DOA of an acoustic wave using a single MEMS sensor and with full angular range between − 90° to + 90°. Subsequently, lock-in amplifiers, one for each channel, were used to synchronously detect the phase of each wings’ displacement signal relative to the reference signal. The excitation harmonic signal employed for generating sound was used as the reference for both lock-in amplifiers.A linear fit with slope of 1.21 was obtained for the phase shift versus incident angle and the intercept occurred at − 3.45°, which may be attributed to a systematic deviation from the normal incidence in the initial alignment of the sensor assembly. A similar linear behavior with slope of 1.4 × 102 = 0.99) is obtained, with a slope of 1.24 and shows that synchronous demodulation can be a good option for the sensor readout.A computer connected to the amplifiers, read the individual phases and calculated their difference. The time constants of the lock-in amplifiers were set to 100 ms and the turntable was rotated from − 90° to + 90° in 2° angular steps. Figure The measurements presented in Figs. Figure A log–log plot of the equivalent angle error as a function of the incident wave SPL was obtained from these values. The SPL for which the signal to noise ratio would be unitary for a given angular resolution can be determined from it. The minimum detectable angle variation or resolution, obtainable with this detection system for each given value of SPL, can also be determined. Figure As the SPL decreases the angular resolution becomes poorer due to the increase in the phase shift uncertainty. An angular resolution of better than 3° was obtained for SPL greater than 25 mPa (42 dB rel 20 μPa).In this work, a single biomimetic MEMS directional sensor was used to determine the DOA of an incident sound wave; in contrast to previous works, in which a second measurement by another similar sensor or a calibrated microphone becomes necessary in order to eliminate the sound pressure level (SPL) as one of the problem’s variables. Instead of using two sensors, utilizing the two resonant modes’ responses of the single sensor also eliminates the need for SPL determination, as it was demonstrated theoretically and empirically. Some of the sensor’s geometric parameters had to be conveniently adjusted in order to bring both modal frequency responses closer and enhance their coupling effects, known to be the reason for the directional sensitivity. The rocking mode resonant frequency was measured 1082 Hz and the bending mode, 1510 Hz. Also vital to the single sensor functioning was the reduction of the acoustic pressure communication with the back of the sensor and the cosine dependence of the directivity pattern associated with it. This was accomplished by closing the back of the sensor. The more responsive bending mode was dampened taking advantage of squeezed film effects by putting the sensor on top of a partially closed air cavity. As a result, the bending mode response is spectrally broadened due to a reduction in its Q factor and slightly downshifted, moving closer to the rocking mode response, also favoring their coupling. Laser vibrometry measurements and finite-element method modeling agreed on these trends for a partially closed back cavity and showed a bending mode oscillation sensitivity one order of magnitude less responsive than on the open back case. On the finite-element modeling simulations, the appropriate back air cavity stiffness and damping ratio were adjusted by changing the backplate slit surface area, responsible for the air and acoustic pressure interaction of the cavity with the exterior medium. Mechanical displacements of the wings were transduced to voltage by way of interdigitated air-gap comb finger capacitors placed at the edge of sensor moving wings, a commercially available capacitance-to-digital integrated circuit (PCap04) and an open-source microcontroller unit (Arduino Due) with dedicated embedded software. Simultaneous and independent measurement of the signals associated with each of the wings displacements enabled the experiments validating the use of a single sensor. Spectral response measurements using the electronic signals were found in good agreement with the previously measured and simulated mechanical spectral responses. The obtained overall sensitivity was on the order of 1 V/Pa. Simple signal processing was utilized to determine the DOA from the amplitudes and phases measured simultaneously from both wings, providing two ways of accomplishing it. The phase shift due to a single tone acoustic signal at 1150 Hz presented a linear characteristic with a slope of 1.24 degree/degree [phase shift/angle of incidence]. Further measurements demonstrated that this approach is capable of delivering an angular resolution in the DOA better than 3° for sound pressure levels greater than 25 mPa. It was clear from the results that the distinct character of individual mode interaction with the partially closed back air cavity was crucial for the DOA determination. The mechanical coupling and the pressure difference characteristics due the partially closed back cavity in the biomimetic sensor revealed both to be important. Although not studied in this work, this points in the direction that it should also be the case for the role of the prosternal chamber, the spiracular and tracheal system in the ormia fly hearing organ.The mechanical spectral responses of the sensor wing displacements with open and closed back configurations were performed using a Polytec OFV-5000 laser vibrometer. The laser head of the OFV 534 unit was installed on an optical breadboard inside the anechoic chamber, while the controller and processing equipment were kept outside, in the chamber’s control room. The sensor holder was also placed on the breadboard right in front of the optical head on a 5-axis motion stage allowing adjustments of the laser beam position on three linear translation directions along with azimuth and elevation angles as well. The position of the beam was visualized with the help of a camera pertaining to the optical head, by means of a splitter collinear with the laser beam. The image was displayed on the control unit screen. The setup also possessed a calibrated omnidirectional microphone model 378A21 from PCB Piezotronics, positioned on the optical breadboard on one side of the device under test, with their longitudinal axes aligned. The signal from the microphone was amplified by a Model 482C sensor signal conditioner, also from PCB Piezotronics. The output of the amplifier was connected to the reference input on the vibrometer junction box and was used by the software to ascertain the sound pressure level impinging on the device under test. The Polytec control software output a sinusoidal signal, frequency swept from 500 Hz up to 2 kHz and amplified by a Techron Power amplifier model 5507 before being connected to a JBL loudspeaker Model No 2450H, 8 ohms impedance, from JBL Incorporated, Northridge, CA, USA, positioned inside the anechoic chamber, making the sound angle of incidence on the sensor close to 45°. Physical impediments in the experiment setup did not allow it to be exactly equal to the desired value. The laser beam was initially positioned at the end of one wing and a measurement obtained by averaging ten frequency swept scans. While keeping all the other positioning and adjustments, the laser beam was positioned at the end of the other wing with the associated ten-average scan measurement obtained.The closed back sensor was mounted with the circuit board on a post, with the device vertical axis parallel to the post axis, and attached to the mandrel of a Brüel and Kjær controllable turntable type 5960, inside de anechoic chamber while its angular position was remotely adjusted in the control room by a type 5997 turntable controller (Brüel and Kjær). The electronic circuits were powered using a dual output DC power supply model E3620A from Agilent, placed in the control room and connected to the circuit board by coaxial cables threaded through wall feedthrough ducts between both rooms. The excitation swept signal was generated by one of the auxiliary signal outputs of a MLFI Lock-in amplifier, 500 kHz/5 MHz, 60 MSa/s from Zurich Instruments, amplified by a Techron Power amplifier model 5507 before being connected to a fixed JBL loudspeaker Model No 2450H, 8 ohms impedance, from JBL Incorporated, Northridge, CA, USA, positioned inside the anechoic chamber facing the turntable, constituting the sound source for the experiment. The electronic signal coming from one of the sensor channels  was connected to the input of this lock-in amplifier, also by threaded cable through the duct, and was synchronously demodulated. Another identical MLFI lock-in amplifier had the signal coming from the other wing connected to its input and demodulating it synchronously and simultaneously with the previous lock-in amplifier demodulation. Both lock-in amplifiers were properly synchronized by connecting their Clock and Trigger inputs/outputs and selecting the one generating the sweep as the master, while the other is configured as a slave. Both instruments were connected to a PC by way of the USB port. The Zurich instruments LabOne software, running on the PC, controls the amplifier parameters and records the data measured. A previous experiment used a calibrated omnidirectional microphone model 378A21 from PCB Piezotronics in place of the directional sensor as a way of relating the SPL incident on it to the lock-in amplifier auxiliary output voltage amplitude. The calibration factor (Pa/V) was utilized to determine the actual SPL once a voltage amplitude was set on for the subsequent measurements. The sensor was positioned at two angular positions with respect to the loudspeaker (± 45°) and for each position at a time the sinusoidal swept signal from 500 Hz to 2 kHz was applied. The calibrated SPL applied was 500 mPa. The magnitude of the signals demodulated by the lock-in amplifiers for the left and right wings were individually recorded and stored in the PC to be plotted later.Two experiments of this kind were performed. The experimental setup inside of the anechoic chamber was exactly the same as the one described for the electric spectral response above for both. The difference lied on where the signals from the wings (right and left) were connected in the control room. On the first experiment each of the signals were connected to a channel of a DSO7054B InfiniiVision digital storage oscilloscope from Agilent Technologies. A single tone acoustic signal with frequency equal to 1150 Hz was applied to the loudspeaker with amplitude such that it was produced an SPL of 500 mPa, according to the previously performed calibration. The sensor angular position was adjusted by the turntable to cover the interval  angles of incidence in 10° steps. Waveforms were saved to a flash drive connected to the oscilloscope USB port to be post processed. The phase shift between the signals was determined at the zero-crossing for each of the signals. On the second experiment, the signals were each connected back to the same lock-in amplifiers they were before. The experiment was then repeated but now with the angular steps reduced to 2° over the same interval. The lock-in amplifiers detected the individual phase of each signal (left or right wing) with respect to the single tone excitation used as a common synchronized reference signal that was generated internally in the master lock-in amplifier. Individual phases were subtracted in the instrument controlling PC with the LabOne software to produce the phase shift between the two demodulated signals.In order to determine the detection limits of the phase shift approach, the same setup for the second experiment of directional characteristic was utilized. Instead of keeping the incident sound pressure level constant, it was electronically and sequentially adjusted to 500, 250, 100, 50, 25, 10 and 5 mPa. At each SPL value, the turntable was rotated in a stepwise manner at five rotation positions placed symmetrically on and around the normal incidence position (0°), being held at each angular position for about 20 s. The initial angular step was set to 2°. The phase shifts were determined by the same method described before and the time series for the values was stored in the computer. For each step, the average value of phase shift (μ) and its standard deviation (σ) were calculated. Assuming that the minimum angular step on the turntable that would allow the electronic system to discriminate the two signal levels is equal to one standard deviation on the detected signal, or a unitary signal to noise ratio (SNR), each SPL will have an associated minimum detectable signal, being that which the signal standard deviation equal to the difference between averages of two adjacent angular steps. If the minimum detectable signal was reached for a given SPL, meaning that it was not possible to discriminate the angular step in the detected signal time series after the turntable had been rotated by one current angular step, then the angular step was increased and kept for the subsequent (lower) SPL, until it would not be possible to discriminate from the noise and the process repeated. The angular step had to be increased to 5° for the 25 mPa SPL and to 10° for the 5 mPa SPL. This way, the phase shift uncertainty related to an SPL is determined. But the uncertainty sought is the one in the angle of arrival, which is related to the phase shift uncertainty through the line slope determined in the second directional characteristic experiment (1.237). Dividing the phase uncertainty by the line slope results the angle of arrival uncertainty related to each SPL.Supplementary Figures