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Polyimide hybrid nanocomposites with the polyimide confined at molecular length scales exhibit enhanced fracture resistance with excellent thermal-oxidative stability at low density. Previously, polyimide nanocomposites were fabricated by infiltration of a polyimide precursor into a nanoporous matrix followed by sequential thermally induced imidization and cross-linking of the polyimide under nanometer-scale confinement. However, byproducts formed during imidization became volatile at the cross-linking temperature, limiting the polymer fill level and degrading the nanocomposite fracture resistance. This is solved in the present work with an easier approach where the nanoporous matrix is filled with shorter preimidized polyimide chains that are cross-linked while in the pores to eliminate the need for confined imidization reactions, which produces better results compared to the previous study. In addition, we selected a preimidized polyimide that has a higher chain mobility and a stronger interaction with the matrix pore surface. Consequently, the toughness achieved with un-cross-linked preimidized polyimide chains in this work is equivalent to that achieved with the cross-linking of the previously used polyimide chains and is doubled when preimidized polyimide chains are cross-linked. The increased chain mobility enables more efficient polymer filling and higher polymer fill levels. The higher polymer-pore surface interaction increases the energy dissipation during polyimide molecular bridging, increasing the nanocomposite fracture resistance. The combination of the higher polymer fill and the stronger polymer-surface interaction is shown to provide significant improvements to the nanocomposite fracture resistance and is validated with a molecular bridging model.

Intrinsically stretchable bioelectronic devices based on soft and conducting organic materials have been regarded as the ideal interface for seamless and biocompatible integration with the human body. A remaining challenge is to combine high mechanical robustness with good electrical conduction, especially when patterned at small feature sizes. We develop a molecular engineering strategy based on a topological supramolecular network, which allows for the decoupling of competing effects from multiple molecular building blocks to meet complex requirements. We obtained simultaneously high conductivity and crack-onset strain in a physiological environment, with direct photopatternability down to the cellular scale. We further collected stable electromyography signals on soft and malleable octopus and performed localized neuromodulation down to single-nucleus precision for controlling organ-specific activities through the delicate brainstem.

Background Neo-aortic pulmonary autografts often experience root dilation and valve regurgitation over time. This study seeks to understand the biomechanical differences between aortic and neo-aortic pulmonary roots using a heart simulator. Methods Porcine aortic, neo-aortic pulmonary, and pulmonary roots (n = 6) were mounted in a heart simulator (parameters: 100 mm Hg, 37 °C, 70 cycles per minute, 5.0 L/min cardiac output). Echocardiography was used to study root distensibility (percentage change in luminal diameter between systole and diastole) and valve function. Leaflet motion was tracked with high-speed videography. After 30 min in the simulator, leaflet thickness (via cryosectioning), and multiaxial modulus (via lenticular hydrostatic deformation testing) were obtained. Results There were no significant differences between aortic and neo-aortic pulmonary leaflet motion, including mean opening velocity (218 vs 248 mm/s, P = .27) or mean closing velocity (116 vs 157 mm/s, P = .12). Distensibility was similar between aortic (8.5%, 1.56 mm) and neo-aortic pulmonary (7.8%, 1.12 mm) roots ( P = .59). Compared to virgin controls, native pulmonic roots exposed to systemic pressure for 30 min had reduced leaflet thickness (630 vs 385 µm, P = .049) and a reduced Young's modulus (3,125 vs 1,089 kPa, P = .077). In contrast, the aortic roots exposed to pressure displayed no significant difference in aortic leaflet thickness (1,317 vs 1,256 µm, P = .27) or modulus (5,931 vs 3,631 kPa, P = .56). Conclusions Neo-aortic pulmonary roots demonstrated equivalence in valve function and distensibility but did experience changes in biomechanical properties and morphology. These changes may contribute to long-term complications associated with the Ross procedure.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Submitted/Accepted version Y.L., Z.L., M.Z., and X.C. acknowledge the National Research Foundation, Singapore (NRF) under NRF’s Medium Sized Centre: Singapore Hybrid-Integrated Next-Generation μElectronics (SHINE) Centre funding programme, and AME programming funding scheme of Cyber Physiochemical Interface (CPI) project (no. A18A1b0045). Y.L. acknowledges National Natural Science Foundation of China (62201243). C.J. acknowledges funding support from the National Key R&D Program of China (no. 2019YFA0706100), the National Natural Science Foundation of China (82151305), Lingang Laboratory (LG-QS-202202-09). T.Q.T. and N.E.L. acknowledge support by the Basic Science Research Program (no. 2020R1A2C3013480) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT. A.F. acknowledges the AFOSR (grant FA9550-22-1-0423). Y.L. and Y.Z. would like to acknowledge the NSF (award no. 2134664) and NIH (award no. R01HD108473) for financial support. X.F. acknowledges the support from the National Natural Science Foundation of China (grant no. U20A6001). L.Y. would like to thank the A*STAR Central Research Fund (CRF) and the AME Programmatic A18A1b0045 (Cyber Physiochemical Interfaces) for funding support. C.F.G. acknowledges the National Natural Science Foundation of China (no. T2225017). T.Q.T. acknowledges the Brain Pool Program (No. 2020H1D3A2A02111068) through the National Research Foundation (NRF) funded by the Ministry of Science. Z.L. acknowledges the support from RIE2020 AME Programmatic Grant funded by A*STAR-SERC, Singapore (Grant No. A18A1b0045). X.G. acknowledges funding support through the Shanghai Science and Technology Commission (grant no. 19JC1412400), the National Science Fund for Excellent Young Scholars (grant no. 61922057). C.D. acknowledges National Science Foundation CAREER: Conformable Piezoelectrics for Soft Tissue Imaging (grant no. 2044688) and MIT Media Lab Consortium funding. D.K. and O.G.S. acknowledge Leibniz Association and the German Research Foundation DFG (Gottfried Wilhelm Leibniz Program SCHM 1298/22-1, KA5051/1-1 and KA 5051/3-1), as well as the Leibniz association (Leibniz Transfer Program T62/2019). C.W. acknowledges the National Key Research and Development Program of China (grant no. 2021YFA1202600), National Natural Science Foundation of China (grant no. 62174082). A.V.-Y.T., E.Z., Y.Z., X.Z., and J.P. acknowledge the National Research Foundation, Singapore (NRF) under NRF’s Medium Sized Centre: Singapore Hybrid-Integrated Next-Generation μElectronics (SHINE) Centre funding programme, and AME programming funding scheme of Cyber Physiochemical Interface (CPI) project (no. A18A1b0045). R.Z. acknowledges National Natural Science Foundation of China (grant no. 51735007) and Beijing Natural Science Foundation (grant no. 3191001). N.M. acknowledges the support by JST PRESTO Grant Number JPMJPR20B7 and JST Adaptable and Seamless Technology transfer Program through Target-driven R&D (ASTEP) grant number JPMJTM22BK. C.P. acknowledges the Korean government (Ministry of Science and ICT, MSIT) (2022R1A4A3032923). M.W. acknowledges the National Key R&D Program of China under Grant (2021YFB3601200). X.Z. acknowledges National Natural Science Foundation of China (no. 62074029). S.X. acknowledges the 3M nontenured faculty award. T.-W.L. and D.-G.S. acknowledge the Pioneer Research Center Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (grant no. NRF-2022M3C1A3081211). C.T.L. would like to acknowledge support from the Institute for Health Innovation and Technology (iHealthtech), the MechanoBioEngineering Laboratory at the Department of Biomedical Engineering and the Institute for Functional Intelligent Materials (I-FIM) at the National University of Singapore (NUS). C.T.L. also acknowledges support from the National Research Foundation and A*STAR, under its RIE2020 Industry Alignment Fund − Industry Collaboration Projects (IAF-ICP) (grant no. I2001E0059) − SIA-NUS Digital Aviation Corp Lab and the NUS ARTIC Research (grant no. HFM-RP1). X.Y. acknowledges funding support by City University of Hong Kong (grant no. 9667221). T.X. and X.Z. acknowledge National Natural Science Foundation of China (22234006). B.C.K.T. acknowledges Cyber-Physiochemical Interfaces CPI, A*STAR A18A1b0045. H.G. acknowledges a research start-up grant (002479-00001) from Nanyang Technological University and the Agency for Science, Technology and Research (A*STAR) in Singapore. W.G. acknowledges National Science Foundation grant 2145802. D.J.L. acknowledges support from the US National Science Foundation grant number CBET-2223566. G.Y. acknowledges support from The Welch Foundation award F-1861, and Camille Dreyfus Teacher-Scholar Award. M.D.D. acknowledges funding support from NSF (grant no. EEC1160483). J.-H.A acknowledges the National Research Foundation of Korea (NRF-2015R1A3A2066337). J.C. acknowledges the Henry Samueli School of Engineering & Applied Science and the Department of Bioengineering at the University of California, Los Angeles for startup support and a Brain & Behavior Research Foundation Young Investigator Grant. K.T. acknowledges JST AIP Accelerated Program (no. JPMJCR21U1) and JSPS KAKENHI (grant no. JP22H00594). P.S.W. acknowledges the National Science Foundation (CMMI1636136) for support. A.M.A., M.C.H., and P.S.W. thank the National Institute on Drug Abuse (DA045550) for support. S.M. and X.C. appreciated the support from the Smart Grippers for Soft Robotics (SGSR) Programme under the National Research Foundation, Prime Minister’s Office, Singapore under its Campus of Research Excellence and Technological Enterprise (CREATE) programme.

Partial-thickness cutaneous injuries distributed over exposed body locations, such as the face and extremities, pose a significant risk of infection, function loss, and extensive scarring. These injuries commonly result from impact of kinetic debris from industrial accidents or blast weaponry such as improvised explosive devices. However, the quantitative connections between partial-thickness injuries and debris attributes (kinetic energy, shape, orientation, etc.) remain unknown, with little means to predict damage processes or design protection. Here we quantitatively characterize damage in near-live human skin after impact by debris-simulating kinetic projectiles at differing impact angles and energies. Impact events are monitored using high-speed and quantitative imaging to visualize skin injuries. These findings are utilized to develop a highly predictive, dynamic computational skin-injury model. Results provide quantitative insights revealing how the dermal-epidermal junction controls more severe wound processes. Findings can illuminate expected wound severity and morbidity risks to inform clinical treatment, and assess effectiveness of emerging personal protective equipment.

This study is motivated by the desire to disseminate a low-cost, high-precision, high-throughput environmental chamber to test materials and devices under elevated humidity, temperature, and light. This paper documents the creation of an open-source tool with a bill of materials as low as US$2,000, and the subsequent evolution of three second-generation tools installed at three different universities spanning thin films, bulk crystals, and thin-film solar-cell devices. We introduce an optical proxy measurement to detect real-time phase changes in materials. We present correlations between this optical proxy and standard X-ray diffraction measurements, describe some edge cases where the proxy measurement fails, and report key learnings from the technology-translation process. By sharing lessons learned, we hope that future open-hardware development and translation efforts can proceed with reduced friction. Throughout the paper, we provide examples of scientific impact, wherein participating laboratories used their environmental chambers to study and improve the stabilities of halide-perovskite materials. All generations of hardware bills of materials, assembly instructions, and operating codes are available in open-source repositories.

Scalable fabrication of charge transport layers with high uniformity and compactness is essential for the commercialization of perovskite solar cells (PSCs). Cost-effective deposition of high-quality electron transport layers (ETLs) is a particularly important step to achieve low-cost, efficient and large-area PSCs. Here, an open-air (relative humidity of 40–50%) and low-temperature (≤100 °C) ultrasonic spray coating of tin oxide (SnO2) nanocomposite films incorporating nanocrystalline SnO2 nanoparticles in an amorphous SnOx matrix is demonstrated to fabricate large-area ETLs for planar PSCs. The optimized SnO2/SnOx nanocomposite exhibits significantly enhanced hole-blocking and high-power conversion efficiencies of 18% and 16% for planar PSCs with an active area of 0.2 cm2 and 1 cm2, respectively. More importantly, the devices show little current–voltage hysteresis as well as good shelf-life stability by maintaining ∼90% of the initial performance without encapsulation after 2500 hours storage under inert conditions. Furthermore, high voltages of >6.0 V have been obtained for solar modules of 2.1 cm2 aperture area comprising six sub-cells in series, suggesting that the low-temperature, open-air and fast spray coating is suitable and transferable to deposit large-area charge transport layers for scalable PSCs or other optoelectronic devices.

Summary We report on the open-air fabrication of perovskite solar modules with key advances, including scalable large-area spray deposition, new monolithic integration scribing techniques, advanced photoluminescence characterization, and reproducible high-throughput manufacturability. Perovskite deposition with linear speeds of 12 m/min without post-annealing is demonstrated, with improved device performance, luminescent yield, and >10× carrier lifetimes. Manufacturability using monolithic integration of series-connected modules is accomplished with a new indirect fiber laser ablation scribing method. A stable cell and module power output of 18.0% and 15.5%, respectively, was achieved with a subcell Voc > 1.06 V. A comprehensive supporting technoeconomic analysis details the entire in-line manufacturing process from the glass substrate to the junction box of the encapsulated module. The module manufacturing cost, balance of system costs, and levelized cost of energy for a range of module efficiencies and lifetimes provide insights for the necessary tool speeds, efficiencies, and lifetimes for utility-scale energy generation.

Ultrathin perfluoropolyether-silane (PFPE-silane) films offer excellent functionality as antifingerprint coatings for display touchscreens due to their oleophobic, hydrophobic, and good adhesion properties. During smartphone use, PFPE-silane coatings undergo many abrasion cycles which limit the coating lifetime, so a better understanding of how to optimize the film structure for improved mechanical durability is desired. However, the hydrophobic and ultrathin (1-10 nm) nature of PFPE-silane films renders them very difficult to experimentally characterize. In this study, the cohesive fracture energy and elastic modulus, which are directly correlated with hardness and better wear resistance of 3.5 nm-thick PFPE-silane films were, respectively, measured by double cantilever beam testing and atomic force microscopy indentation. Both the cohesive fracture energy and modulus are shown to be highly dependent on the underlying film structure. Both values increase with optimal substrate conditions and a higher number of silane groups in the PFPE-silane precursor. The higher cohesive fracture energy and modulus values are suggested to be the result of the changes in the film chemistry and structure, leading to higher cross-linking density. Therefore, future work on optimizing PFPE-silane film wear resistance should focus on pathways to improve the cross-linking density. Subcritical fracture testing in humid environments reveals that humidity negatively affects the fracture properties of PFPE-silane films.

To decode the feeling of skin tightness after application of a cosmetic product and how to soothe this discomfort. To pursue this aim, we considered the ingredient's effect on stratum corneum (SC) biomechanics to differentiate between consumers prone to tightness from those that are not and correlate these effects with mechanoreceptor activation.In vivo clinical trials were used to assess the tightness perception dichotomy between groups of Caucasian women; in vitro experiments were used to measure the mechanical stresses induced in the SC after cleanser and moisturizer application; and in silico simulations were used to illustrate how the measured mechanical stresses in the SC result in the development of strains at the depth of cutaneous mechanoreceptors, triggering tightness perceptual responses.Before any cream application, women prone to tightness tend to have a more rigid SC than their less sensitive counterparts, however cleanser application increases SC stiffness in all women. Surprisingly, no correlation was found between tightness perception and hydration measurements by the Corneometer or barrier function, as evaluated by transepidermal water loss. Self-declared tightness and dryness scores were strongly associated with a self-described sensitive skin. After application of the optimized moisturizing formula, Osmoskin® containing natural waxes with good filming properties, consumers report a strong decrease in tightness and dryness perception. These results match with laboratory experiments where the cleanser was shown to increase SC drying stresses by 34%, while subsequent application of Osmoskin® decreased stresses by 48%. Finite element modelling, using experimental results as input, elucidates the differences in perception between the two groups of women. It makes clear that Osmoskin® changes the mechanical status of the SC, producing strains in underlying epidermis that activates multiple cutaneous mechano-receptors at a level correlated with the self-perceived comfort.Integration of the in vivo, in vitro and in silico approaches provides a novel framework for fully understanding how skin tightness sensations form and propagate, and how these sensations can be alleviated through the design of an optimized moisturizer.Décoder l'impression de tiraillement de la peau après l'application d'un produit cosmétique et la manière d'apaiser cette sensation désagréable. Pour poursuivre cet objectif, nous avons pris en compte l'effet de l'ingrédient sur la biomécanique de la couche cornée afin de différencier les consommatrices sujettes à un tiraillement de celles qui ne le sont pas et de corréler ces effets avec l'activation des mécanorécepteurs. MÉTHODES: Des essais cliniques in vivo ont été utilisés pour évaluer la dichotomie de perception de tiraillement entre des groupes de femmes de race caucasienne; des expériences in vitro ont été utilisées pour mesurer les contraintes mécaniques induites dans la couche cornée après application d'un produit nettoyant et d'un produit hydratant; et des simulations in silico ont servi à illustrer comment les contraintes mécaniques mesurées dans la couche cornée entraînent le développement de souches à la profondeur des mécanorécepteurs cutanés, qui déclenchent les réponses perceptives de tiraillement. RÉSULTATS: Avant toute application de crème, les femmes sujettes au tiraillement tendent à avoir une couche cornée plus rigide que leurs homologues moins sensibles, mais l'application d'un produit nettoyant augmente la raideur de la couche cornée chez toutes les femmes. Étonnamment, aucune corrélation n'a été observée entre la perception de tiraillement et les mesures d'hydratation réalisées par le cornéomètre ou la fonction barrière, évaluée par la perte d'eau transépidermique. Les scores de tiraillement et de sécheresse auto-déclarés étaient fortement corrélés à une peau décrite par les sujets elles-mêmes comme sensible. Après application de la formule hydratante optimisée, Osmoskin®, qui contient des cires naturelles ayant de bonnes propriétés de dépôt de film, les consommateurs rapportent une forte diminution de la sensation de tiraillement et de sécheresse. Ces résultats concordent avec les expériences en laboratoire où le produit nettoyant s'est avéré augmenter les contraintes de séchage de la couche cornée de 34 %, tandis que l'application ultérieure d'Osmoskin® a réduit les contraintes de 48 %. La modélisation à éléments finis, en utilisant les résultats expérimentaux comme données, élucide les différences de perception entre les deux groupes de femmes. Il est clair qu'Osmoskin® modifie l'état mécanique de la couche cornée, et produit des souches dans l'épiderme sous-jacent qui activent plusieurs mécano-récepteurs cutanés à un niveau corrélé au confort perçu par la patiente.La combinaison des approches in vivo, in vitro et in silico fournit un nouveau cadre pour comprendre pleinement comment les sensations de tiraillement de la peau se forment et se propagent, et comment elles peuvent être soulagées en mettant au point une crème hydratante optimisée.

Cosmetic emollients are widely used in skincare formulations due to their ability to 'soften' the skin and modulate formulation spreadability. Though emollients are commonly used, little is known about their effects on the biomechanical barrier properties of human stratum corneum (SC), which play a critical role in consumer perception of formulation efficacy. Accordingly, our objective was to provide new insights with a study involving fourteen cosmetic emollient molecules with widely varying structures, molecular weights, SC diffusivities, topological polar surface areas (TPSAs), viscosities and chemical functionalities.Mechanical stress in the SC was measured in vitro using a substrate curvature measurement technique. Stress development due to SC drying was measured before and after topical treatment with cosmetic emollients. Emollient diffusivity and alterations to lipid content in SC after treatment were measured via ATR-FTIR spectroscopy. The maximum penetration volume of emollient in SC was characterized to elucidate mechanisms underlying emollient effects on stress.The application of all cosmetic emollients caused a reduction in SC mechanical stress under dehydrating conditions, and a linear correlation was discovered between emollient penetration volume and the degree of stress reduction. These molecules also induced increases in stress equilibration rate, signalling changes to SC transport kinetics. Stress equilibration rate increases linearly correlated with decreasing intensity of the νCH2 band, indicating a previously unknown interaction between cosmetic emollients and SC lipids. Stress and penetration volume results were rationalized in terms of a multi-parameter model including emollient molecular weight, diffusivity, TPSA and viscosity.We provide a new rational basis for understanding the effects of cosmetic emollient choice on biomechanical properties affecting SC barrier function and consumer perception. We demonstrate for the first time that emollients very likely reduce SC mechanical stress through their ability to take up volume when penetrating the SC, and how molecular weight, SC diffusivity, TPSA and viscosity are predictive of this ability. As cosmetic formulations continue to evolve to meet the needs of customers, emollient molecules can be selected that not only contribute to formulation texture and/or spreadability but that also leverage this novel connection between emollient penetration and SC biomechanics.Les émollients cosmétiques sont largement utilisés dans les formulations de soins de la peau en raison de leur capacité à «adoucir» la peau et à moduler la capacité d'étalement de la formulation. Bien que les émollients soient couramment utilisés, on en sait peu sur leurs effets sur les propriétés de barrière biomécanique de la couche cornée humaine (SC), qui jouent un rôle essentiel dans la perception par les consommateurs de l'efficacité de la formulation. En conséquence, notre objectif était de fournir de nouvelles perspectives avec une étude impliquant quatorze molécules émollientes cosmétiques avec des structures, des poids moléculaires, des diffusivités SC, des surfaces polaires topologiques (TPSA), des viscosités et des fonctionnalités chimiques très variables. MÉTHODES: La contrainte mécanique dans le SC a été mesurée in vitro en utilisant une technique de mesure de la courbure du substrat. Le développement du stress dû au séchage SC a été mesuré avant et après un traitement topique avec des émollients cosmétiques. La diffusivité émolliente et les altérations de la teneur en lipides dans la SC après le traitement ont été mesurées par spectroscopie ATR-FTIR. Le volume de pénétration maximal de l'émollient dans SC a été caractérisé pour élucider les mécanismes sous-jacents aux effets émollients sur le stress. RÉSULTATS: L'application de tous les émollients cosmétiques a entraîné une réduction de la contrainte mécanique SC dans des conditions de déshydratation, et une corrélation linéaire a été découverte entre le volume de pénétration de l'émollient et le degré de réduction de la contrainte. Ces molécules ont également induit des augmentations du taux d'équilibrage des contraintes, signalant des changements dans la cinétique de transport SC. Le taux d'équilibrage des contraintes augmente linéairement en corrélation avec la diminution de l'intensité de la bande νCHNous fournissons une nouvelle base rationnelle pour comprendre les effets du choix des émollients cosmétiques sur les propriétés biomécaniques affectant la fonction de barrière SC et la perception du consommateur. Nous démontrons pour la première fois que les émollients réduisent très probablement la contrainte mécanique SC grâce à leur capacité à prendre du volume lors de la pénétration du SC, et comment le poids moléculaire, la diffusivité SC, le TPSA et la viscosité sont prédictifs de cette capacité. Alors que les formulations cosmétiques continuent d'évoluer pour répondre aux besoins des clients, des molécules émollientes peuvent être sélectionnées qui contribuent non seulement à la texture et / ou à l'étalement de la formulation, mais qui exploitent également cette nouvelle connexion entre la pénétration des émollients et la biomécanique SC.

Emulsifier molecules, with their amphiphilic character, are ubiquitous in moisturizing creams and primarily serve to disperse the water-insoluble molecules such as emollients, oils, lipids and fats in water. The objective of this study was to investigate the effect of emulsifier molecules on the barrier and biomechanical properties of human stratum corneum (SC) and to compare the efficacy of emulsifier molecules when used in a fully formulated moisturizing cream.We employed methods based on thin-film mechanics to measure the drying stress and intercellular cohesion in the SC. The emulsifier molecules or moisturizing creams formulated with them were applied to a fully hydrated SC adhered to a glass substrate. In-plane stress developed in the SC during drying was then measured by tracking changes in the curvature of the glass substrate. The intercellular cohesion within the SC was measured by means of a double cantilever beam (DCB) set-up, where the treated or untreated SC was sandwiched between two substrates, and the delamination energy calculated by measuring the force required to drive a crack through the SC. Moisturizing cream diffusivity through the stratum corneum was measured by spectroscopic technique and related to internal SC stress and fracture energy.We observe significant differences in the biomechanical behaviour of SC when moisturizing creams with different emulsifier molecules are applied on isolated stratum corneum ex vivo. The reduction in maximum stress varied between 12% and 26% depending on the emulsifier molecules used in the formulation. The intercellular cohesion and the diffusion of molecules in the formulated moisturizing creams through the SC were also found to be strongly dependent on the type of emulsifier molecule used in the formulation.The biomechanical and barrier properties of the human stratum corneum show strong dependence on the emulsifier molecule used in the moisturizing creams, even when the creams included only ~3 weight% emulsifier molecules. Moreover, we found that the reduction in SC peak stress was strongly correlated with the formulation diffusivity into the SC. The moisturizing creams diffusing fastest into the SC had the largest reduction in peak stress and vice versa.Les molécules d’émulsifiant, avec leur caractère amphiphile, sont omniprésents dans les crèmes hydratantes et servent principalement à disperser dans l’eau les molécules hydro insolubles telles que les émollients, les huiles, les lipides et les graisses. L’objectif de cette étude était d’étudier l’effet des molécules d’émulsifiant sur les propriétés barrières et biomécaniques de la couche cornée humaine (stratum corneum, SC), et de comparer l’efficacité des molécules d’émulsifiant lorsqu’elles sont utilisées dans une crème hydratante intégralement formulée. MÉTHODES: Nous avons employé des méthodes basées sur des propriétés mécaniques de couches minces pour mesurer le stress de dessèchement et la cohésion intercellulaire dans le SC. Les molécules d’émulsifiant ou les crèmes hydratantes formulées avec ces molécules ont été appliquées sur un SC entièrement hydraté collé à un substrat de verre. Le stress dans le plan développé dans le SC pendant le dessèchement a été mesuré en suivant les changements de courbure du substrat de verre. La cohésion intercellulaire au sein du SC a été mesurée au moyen d’une configuration de faisceau à double cantilever (DCB), où le SC traité ou non traité a été placé entre deux substrats, et l’énergie de délamination calculée en mesurant la force nécessaire pour entrainer une fissure dans la couche cornée. La diffusivité de la crème hydratante dans la couche cornée a été mesurée par la technique spectroscopique, et était liée à l’énergie interne du stress et de la fracture SC. RÉSULTATS: Nous observons des différences significatives dans le comportement biomécanique du SC lorsque des crèmes hydratantes avec différentes molécules d’émulsifiant sont appliquées sur une couche cornée isolée ex vivo. La réduction du stress maximal variait entre 12 % et 26 % en fonction des molécules d’émulsifiant utilisées dans la formulation. La cohésion intercellulaire ainsi que la diffusion des molécules dans les crèmes hydratantes formulées par le biais du SC se sont également révélées fortement dépendantes du type de molécule d’émulsifiant utilisée dans la formulation.Les propriétés biomécaniques et barrières de la couche cornée humaine montrent une forte dépendance à la molécule d’émulsifiant utilisée dans les crèmes hydratantes, même lorsque ces crèmes contenaient uniquement plus ou moins 3% de molécules d’émulsifiant. De plus, nous avons constaté que la réduction du stress maximal était fortement corrélée à la diffusivité de la formulation dans le SC. Les crèmes hydratantes qui se diffusent le plus rapidement dans le SC avaient la plus grande réduction du stress maximal et vice versa.

Background Thermal Spring Water (TSW) has been recognized to have beneficial effects on skin; however, the mechanisms underlying these are not completely elucidated. Aims We compared the effects of Avene TSW with mineral-rich (MR) TSW on the biomechanical properties of the skin using mechanistic ex vivo assays and clinical studies. Methods Ex vivo studies included the effect of both TSWs on the structure of the surface of human skin explants using scanning electron microscopy (SEM); mineral elemental content on the skin surface using SEM coupled to energy dispersing X-ray spectroscopy; and the stress properties of the stratum corneum (SC) when exposed to dehydration. Human clinical studies were conducted to compare the soothing effect of TSWs after a dermatological chemical peeling of face skin and to evaluate the overall sensitive scale of consumers using Avene TSW for 7 days. Results Both TSWs preserved surface skin ultrastructure; however, crystals formed from MR-TSW were needle-like and formed small grains, present in clusters heterogeneously spread over the surface. Needle crystals were mainly composed of calcium, while small clusters were mainly composed of sulphur. By contrast, Avene TSW-formed crystals composed of sodium and chlorine only were regular in shape and homogeneously distributed across the skin surface. Peak stress of SC layers was increased by MR-TSW, whereas Avene TSW showed a comparatively reduced effect on dehydration and stress. The difference in the two TSW types was reflected in clinical findings comparing postpeeling redness after TSW application. Avene TSW significantly decreased postpeeling redness, while MR-TSW increased it. The overall sensitive scale of consumers was decreased by 47% using Avene TSW for 7 days. Conclusions Avene TSW decreases postpeeling redness and soothes sensitive skin in human volunteers. Mechanistic studies suggested that differences in biomechanical effects could be linked to differences in calcium content of the TSW.

We report a scalable, low-temperature TiOx electron transport layer (ETL) produced directly on top of perovskite in an inverted architecture device by an open-air chemical vapor deposition (OA-CVD) process. The OA-CVD pyrolysis of a titanium ethoxide precursor forms a fully inorganic, conformal, and compact TiOx film. The resultant film is mechanically robust and exhibits a fracture toughness 30-fold higher than commonly used fullerene-based ETL films. The TiOx is an effective barrier layer against environmental degradation—unencapsulated devices with the TiOx ETL retain 60% of their initial efficiency after 1000 hours in ambient aging conditions—compared to devices with a fullerene ETL which were inoperable after 144 hours. Inverted architecture devices with an optimized TiOx ETL thickness of 70 nm exhibited high open-circuit voltages of 1.08 V. We comment on the photocatalytic properties of TiOx and the influence of an amorphous film on maximum power point stability.

Rapid Spray Plasma Processing (RSPP) is a high throughput, scalable, and open-air route toward manufacturing perovskite solar modules. The plasma exposure is dosed such that the perovskite precursor solution is cured in milliseconds using a combination of rapid heating, reactive species, and UV photons. We implemented in situ wide angle X-ray scattering (WAXS) to characterize the crystal growth in multiple cation, mixed halide perovskite thin films—Csx(MAzFA1−z)1−xPb(Br0.17I0.83)3 for 0.05 ≤ x ≤ 0.25—fabricated in open air. The use of synchrotron radiation and high detector speeds resolved the formation and dissolution of a transient intermediate crystalline phase during the tens of milliseconds when the perovskite crystallized. Increasing the mole fraction of cesium and methylammonium resulted in a decrease in the intermediate phase and an increase in the average grain diameter. Increasing the cesium fraction suppressed phase segregation, as observed in photoluminescence. Calculations showed the refractive index decreased and the extinction coefficient increased with cesium fraction. Based on the rapid crystallization kinetics, RSPP perovskite films exhibit residual stress values >5× lower than spin coated films. Understanding the kinetics of perovskite formation enables the design of perovskite films with improved thermomechanical and operational stability.

Background: The lipid components and natural moisturizing factors (NMFs) of the stratum corneum (SC) are integral pieces of the self-regulating barrier strategy which comprises one of the most important functions of human skin and seems to be related to biomechanical responses of the SC. Objectives: This work presents the contributions of the lipid bilayers and NMFs to the barrier properties and mechanical responses of human SC. Methods: We performed 2 biomechanical experiments, substrate curvature testing and double cantilever beam cohesion measurements, on isolated human SC exposed to either water, a 1:1 mixture of acetone/ether, or a 1:1 mixture of chloroform/methanol for various durations. Results: We show that treating ex vivo SC with organic solvents results in lipid extraction which increases with duration of exposure. This extraction is tied to a remarkably linear increase in the levels and rates of biaxial stress development during drying/hydration cycles. This effect appears to be tied to the total amounts of lipids extracted. Furthermore, striking changes are seen in the intercellular cohesion properties of the tissue after solvent exposure. Interestingly, changes in drying stress profiles are not observed after treatment with water, which has been previously shown to remove NMFs from the tissue, and which therefore might be expected to induce changes in the drying behavior of the skin. However, changes in intercellular cohesion and the SC cohesion gradient are seen, suggesting impacts on the corneodesmosome protein binding junctions within the tissue. Conclusions: These results suggest that lipid loss causes marked increases in SC drying stresses, which may in turn contribute to changes in skin perception. NMF extraction may be important in vivo, but has remarkably little impact in isolated SC.

Intrinsically stretchable bioelectronic devices based on soft and conducting organic materials have been regarded as the ideal interface for seamless and biocompatible integration with the human body. However, the grand challenge remains for the conducting polymer to possess both high mechanical ductility and good electrical conduction at cellular level feature sizes. This longstanding material limitation in organic bioelectronics has impeded the full exploitation of its unique benefits. Here, we introduce a new molecular engineering strategy based on rationally designed topological supramolecular networks, which allows effective decoupling of competing effects from multiple molecular building blocks to meet complex requirements. We achieve two orders of magnitude improvement in the conductivity under 100% strain in physiological environment, along with the capability for direct photopatterning down to 2 μm. These unprecedented capabilities allow us to realize previously inaccessible bioelectronic applications including high-resolution monitoring of ‘soft and malleable’ creatures, e.g., octopus, and localized neuromodulation down to single nucleus precision for controlling organ-specific activities through delicate tissues, e.g., brainstem.

Moisturizing compounds are commonly applied topically to human stratum corneum (SC). Many types of molecular species are employed, most commonly including humectants and occlusives. We find new evidence of keratin dispersion caused by the moisturizing compound ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid), and provide the first characterization of its impacts on the hydration kinetics and biomechanics of SC. A second compound, 2-(2-hydroxyethoxy)ethylguanidine succinate (HEG) was investigated for comparison. A suite of biomechanical and biochemical assays including FTIR, drying stress, and cellular cohesion were used. Studies were conducted on normal, lipid-extracted, and lipid plus natural moisturizing factor extracted SC. Ectoine was found to improve the dispersity and hydration of keratin bundles in corneocytes. It also decreased rates of stress development in lipid extracted SC when exposed to a dry environment by ∼30% while improving stress reduction during rehydration by ∼20%. Peak stresses were increased in harsh drying environments of, Highlights • First study demonstrating the biomechanical impact of keratin dispersion on human skin • Ectoine disperses keratin bundles in human stratum corneum • Rates of drying stress development are reduced in keratin-dispersed skin • Rehydration rates are increased in keratin-dispersed skin • Keratin dispersion alters corneocyte cohesion profiles

Low and Ultra-k dielectric organosilicate glasses (OSG) are widely used in device interconnect applications such as shallow trench isolation as insulating units. However, the process of gap filling between conducting units has been challenging. One of the challenges is related to the undesired formation of nanovoids in the low-k dielectric material confined inside the trench geometry. Importantly, the effects of such nanoscale device constraints on the structure and mechanical reliability of low-k dielectric hybrid materials are not very well understood. To close this lack of understanding and guide the related experimental efforts we performed molecular dynamics simulations where we explore the role of the molecular structure and connectivity of different low-k dielectric OSG precursors under nanoscale confinement, and predict the resulting elastic and fracture properties. We demonstrated that hyperconnected OSG precursors with aromatic rings, such as the 1,3,5-benzene molecule, pack more homogenously under confinement leading to smaller nanovoids and better mechanical reliability compared to conventionally bridged OSG precursors, such as the ethylene bridged Et-OCS molecule.

We report an industrially relevant approach to both scalable and fast open-air perovskite photovoltaic (PV) module production. This work resolves some of the most formidable barriers to module-level scaling that the perovskite community has been facing. Key advances include scalable large-area spray deposition, new monolithic integration scribing techniques, advanced photoluminescence characterization, and reproducible high-throughput manufacturability. Our rapid spray processing techniques enabled the highest perovskite PV efficiency produced in open-air. Innovations in scribing techniques enabled the first single-source laser process to achieve perovskite module monolithic integration and technoeconomic analysis led to a comprehensive cost model for perovskite module manufacturing. We report significant progress in reducing perovskite manufacturing costs necessary to potentially compete with incumbent Si-based PV for utility-scale power generation.

Polyolefin elastomer (POE) encapsulants are becoming increasingly competitive options to replace ethylene vinyl acetate (EVA); however, there remains little published work quantifying their adhesion. Here we characterize the critical adhesion energy of POE-encapsulated, bifacial mini-modules using single cantilever beam tests. Two types of structures are explored – a standard construction and one utilizing SmartWire Connection Technology (SWCT). Measurements are obtained for the encapsulant adhesion on both the front and rear sides of the mini-modules. Results indicate that POE encapsulants provide initial adhesion better than EVA; however, adhesion in SmartWire mini-modules is reduced due to weaker bonding with the SmartWire foil. These results provide a crucial baseline for understanding how delamination will affect POE-encapsulated modules. Additionally, they provide the first reported effects of modules utilizing SWCT on resulting adhesive strength.

This study begins to investigate the role of environmental factors, such as temperature and humidity, on the delamination kinetics of the ethylene vinyl acetate (EVA)/silicon–photovoltaic (Si–PV) cell interface. A fracture mechanics approach based on a single cantilever beam technique is employed to measure the delamination rate as a function of applied driving force. To glean insight into the mechanisms of bonding and degradation at this interface, and the effect of manufacturing variability and quality, we consider a high-quality pristine EVA and two EVAs formulated with reduced amounts of its adhesion promoter, silane. Results indicate that a bulk change in the viscoelastic properties of the EVA dominates the delamination kinetics at high driving forces and low humidity and the effect of a chemical reaction only becomes apparent at higher humidity and lower driving forces. These findings suggest that only interfacial phenomenon of susceptible, degraded material may have to be considered to adequately model PV module delamination failure.

We developed a framework to predict and model the photodegradation of adhesion and cohesion of a silicone encapsulant for concentrator photovoltaic applications. Silicone encapsulant specimens were artificially weathered under narrow band UV filters to determine the effects of individual wavelengths within the UV spectrum on the photodegradation of the cohesion of encapsulant material and its adhesion with adjacent interfaces. The threshold wavelength, signifying the upper bound of the damaging action spectrum for the silicone, was identified from the results. In addition, specimens were artificially weathered with different relative humidities to understand the effects of moisture on the rate of photodegradation. The adhesion energy was measured using a fracture mechanics approach. The complementary delaminated surfaces were characterized to determine the failure pathway and chemistry changes resulting from photodegradation. A previously developed model was modified to account for the effects of damaging wavelengths in the terrestrial solar spectrum and reciprocity law failure due to varying UV intensity during weathering. With these modifications, the model showed good agreement with the behavior of the silicone encapsulant exposed in an outdoor solar concentrator simulating concentrator photovoltaics operating conditions. Similar studies can be adopted to develop models that can have high predictive accuracies based on accelerated aging studies.

The stratum corneum (SC) is key in the maintenance of the biomechanical barrier and hydration of skin. Our previous investigations showed beneficial effects of a combination of emollients on water capture and retention and protein and lipid organization, all of which are linked to dryness and dry skin damage. Here, we show how a formulation containing an emollient combination ("Trio") and its basal formulation (placebo) impacted the descriptors of SC hydration in SC layers. Only the Trio formulation-not its placebo formulation-modified SC biomechanical drying stress behaviour and imparted a high capacity to protect it from dehydration. This was in accordance with findings at the molecular level using Raman analyses and at the structural level using cryo-scanning electron microscopy (SEM). After topical application, only the Trio formulation profoundly increased lateral packing of lipids and their compactness. Cryo-SEM showed that, unlike the placebo formulation, the Trio formulation prevented the water loss when applied before the dehydration process. In conclusion, these studies demonstrate that stresses in the SC due to dehydration can be alleviated using a formulation containing emollients that interact with the SC lipid components.

Perovskite photovoltaics (PV) have achieved rapid development in the past decade in terms of power conversion efficiency of small-area lab-scale devices; however, successful commercialization still requires further development of low-cost, scalable, and high-throughput manufacturing techniques. One of the key challenges to the development of a new fabrication technique is the high-dimensional parameter space, and machine learning (ML) can be used to accelerate perovskite PV scaling. Here, we present an ML-guided framework of sequential learning for manufacturing process optimization. We apply our methodology to the Rapid Spray Plasma Processing (RSPP) technique for perovskite thin films in ambient conditions. With a limited experimental budget of screening 100 conditions process conditions, we demonstrated an efficiency improvement to 18.5% for the best device, and we also experimentally found 10 unique conditions to produce the top-performing devices of more than 17% efficiency, which is 5 times higher rate of success than pseudo-random Latin hypercube sampling. Our model is enabled by three innovations: (a) flexible knowledge transfer between experimental processes by incorporating data from prior experimental data as a soft constraint; (b) incorporation of both subjective human observations and ML insights when selecting next experiments; (c) adaptive strategy of locating the region of interest using Bayesian optimization first, and then conducting local exploration for high-efficiency devices. Furthermore, in virtual benchmarking, our framework achieves faster improvements with limited experimental budgets than traditional design-of-experiments methods ( e.g ., one-variable-at-a-time sampling). This framework is shown to enable researchers’ domain knowledge in the ML-guided optimization loop; therefore, it has the potential to facilitate the wider adoption of ML in scaling to perovskite PV manufacturing.

Supplemental Digital Content is available in the text., Background: The purpose of this study was to determine the feasibility of using mouse models for translational study of flexor tendon repair and reconstruction. Methods: Quantitative data detailing the gross anatomy, biomechanical characteristics, and microscopic structure of the deep digit flexor tendon (DDF) of the mouse hindpaw were obtained. Histological characterization of the DDF and the anatomy of the digit in the mouse hindpaw are detailed. Biomechanical testing determined the load-to-failure, stress, elastic modulus, and the site of tendon failure. Results: In gross anatomy, the origins and insertions of the mouse deep digit flexor tendon are similar to those of the human digit, surrounded by a synovial sheath that is only 1- to 2-cells thick. A neurovascular network runs on each side of the digit outside the synovial sheath, but does not clearly penetrate it. The thickness of the DDF is 0.14 ± 0.03 mm and the width is 0.3 ± 0.03 mm. The thickness of the DDF is less than that of 9-0 nylon needle. The mean failure force of the deep flexor tendon was 2.79 ± 0.53N. Conclusions: The gross anatomy of the mouse hindpaw digit is similar to that of the human digit except for key differences seen in the synovial sheath and vascular supply. The dimensions of the mouse DDF make it challenging to create a clinically translatable repair model using currently available surgical techniques. Despite the similarities between the human and mouse anatomy, and the powerful basic science tools available in murine models, mice are an unreliable model for assessing flexor tendon injury and repair.

A computational platform describing the spatial and temporal interactions of monomers during the formation of network polymers provides structure-property relationships that are used to synthesize 3D network polymers with tailored functionalities. The three-dimensional arrangement of natural and synthetic network materials determines their application range. Control over the real-time incorporation of each building block and functional group is desired to regulate the macroscopic properties of the material from the molecular level onwards. Here we report an approach combining kinetic Monte Carlo and molecular dynamics simulations that chemically and physically predicts the interactions between building blocks in time and in space for the entire formation process of three-dimensional networks. This framework takes into account variations in inter- and intramolecular chemical reactivity, diffusivity, segmental compositions, branch/network point locations and defects. From the kinetic and three-dimensional structural information gathered, we construct structure-property relationships based on molecular descriptors such as pore size or dangling chain distribution and differentiate ideal from non-ideal structural elements. We validate such relationships by synthesizing organosilica, epoxy-amine and Diels-Alder networks with tailored properties and functions, further demonstrating the broad applicability of the platform.

We show that hyperconnected ULK dielectric glasses incorporating optimal precursor geometries lead to exceptional mechanical stiffness, as well as increasing fracture bond density. Using molecular dynamics and a novel graph theory approach, we predict that hyperconnected precursors with cyclic planar geometries significantly improve the mechanical reliability of these otherwise fragile materials, by not only increasing the network stiffness but also contributing to the fracture energy. Ultimately, we conclude that characterizing the implications of structural elements, such as precursor geometry and network connectivity, on the mechanical and fracture properties is essential for mechanically much more reliable design and integration of ULK dielectric materials.

Intrinsically and fully stretchable active-matrix-driven displays are an important element to skin electronics that can be applied to many emerging fields, such as wearable electronics, consumer electronics and biomedical devices. Here, we show for the first time a fully stretchable active-matrix-driven organic light-emitting electrochemical cell array. Briefly, it is comprised of a stretchable light-emitting electrochemical cell array driven by a solution-processed, vertically integrated stretchable organic thin-film transistor active-matrix, which is enabled by the development of chemically-orthogonal and intrinsically stretchable dielectric materials. Our resulting active-matrix-driven organic light-emitting electrochemical cell array can be readily bent, twisted and stretched without affecting its device performance. When mounted on skin, the array can tolerate to repeated cycles at 30% strain. This work demonstrates the feasibility of skin-applicable displays and lays the foundation for further materials development., To realize a skin-like display for human-electronics interfaces, intrinsically stretchable light-emitting, transistor and device interconnect components are needed. Here, the authors report a fully stretchable transistor driven active-matrix organic light-emitting electrochemical cell array.

The three-dimensional arrangement of natural and synthetic network materials determines their application range. Control over the real-time incorporation of each building block and functional group is desired to regulate the macroscopic properties of the material from the molecular level onwards. Here we report an approach combining kinetic Monte Carlo and molecular dynamics simulations that chemically and physically predicts the interactions between building blocks in time and in space for the entire formation process of three-dimensional networks. This framework takes into account variations in inter- and intramolecular chemical reactivity, diffusivity, segmental compositions, branch/network point locations and defects. From the kinetic and three-dimensional structural information gathered, we construct structure-property relationships based on molecular descriptors such as pore size or dangling chain distribution and differentiate ideal from non-ideal structural elements. We validate such relationships by synthesizing organosilica, epoxy-amine and Diels-Alder networks with tailored properties and functions, further demonstrating the broad applicability of the platform.

A scalable, open-air plasma process has been developed to deposit alternating layers of conformal organosilicate and dense SiO 2 thin film barriers to prevent moisture ingress. The in-situ low temperature process is suitable for direct deposition on thermally sensitive perovskite devices and is compatible with flexible polymeric substrates. When deposited directly on perovskite solar cells, they retain over 80% of their initial performance for over 660 hours in a 50°C 50%RH accelerated aging environment. Using optical calcium testing, low water vapor transmission rates (WVTR) on the order of 10−3 g/m2/day at an accelerated aging condition of 38°C and 90% relative humidity (RH) are achieved. The ability of the multilayer barrier to enable device resistance to humid environments is crucial towards realizing longer operating lifetimes.

Emerging moisture sensitive devices require robust encapsulation strategies to inhibit water ingress and prevent premature failure. A scalable, open-air plasma process has been developed to deposit alternating layers of conformal organosilicate and dense SiO2 thin-film barriers to prevent moisture ingress. The in situ low-temperature process is suitable for direct deposition on thermally sensitive devices and is compatible with flexible polymeric substrates. Using optical calcium testing, low water vapor transmission rates on the order of 10-3 g/m2/day at an accelerated aging condition of 38 °C and 90% relative humidity (RH) are achieved. Using moisture-sensitive perovskite devices as a representative moisture-susceptible device, devices retain over 80% of their initial performance for over 660 h in a 50 °C 50% RH accelerated aging environment. The ability of the multilayer barrier to enable device resistance to humid environments is crucial toward realizing longer operating lifetimes.