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Herein, a soft and flexible polymer composite sensor with a surface structure is manufactured that is sensitive to a wide range of mechanical stimuli, including small actions and large motions. A polymer sensor performing with a piezoresistive mechanism is proposed by synthesizing a new conductive polymer composite to fabricate a microline structure by itself, named Ag-reduced poly(ethylene glycol) diacrylate (PEGDA) composite directional bending sensor (ACBS). A simple but effective process of forming nanoparticles (NPs) and surface structures is a notable characteristic. High sensitivity to a small stimulus was achieved by forming Ag NPs within PEGDA, particularly concentrating on the surface and applying the microline structure. With the structural characteristics of a line structure, the ACBS achieved anisotropic sensitivity to bulk motion along the arranged line direction. The excellent sensitivity of this polymer sensor was experimentally demonstrated via water droplets, blowing, and breathing. Combining the advantages of a simple synthetic and simple fabrication process along with the fabrication ability of the microsurface structure with the material itself and the conductive Ag/PEGDA integrated layer, this ACBS is outstanding as a soft and flexible polymer composite sensor and has potential application in physical devices such as wearable devices and biosensors.

Directional droplet-sliding control without wetting the surface is immensely required in advanced surface engineering, including biological and chemical analyses or green technology. However, the development of robust and transparent thin sticker-type directional omniphobic films for portable usage in smart microfluidic platforms is rare. In this study, we report a novel perfluoropolyether (PFPE) directional omniphobic film (PDOF). The PDOF is a robust and transparent ultra-thin sticker-type film that can control the anisotropic sliding of various liquid droplets on the surface. The PFPE is a chemically stable and turgid material compared to polydimethylsiloxane (PDMS), which is often used to fabricate liquid-repellent thin films. A well-designed fabrication criterion through adhesion engineering in the soft-molding process was developed using the PFPE to obtain a PDOF with a thickness of 56 μm, with re-entrant micro-stripe structures on the surface. The fabricated PDOF showed intriguing liquid sliding properties based on the direction and spacing of the microstructures. This aspect is defined as an anisotropic factor.

Recent extensive research on flexible electronics has led to the development of various flexible sensors. In particular, sensors inspired by the slit organs of a spider, which utilize cracks in a metal film to measure strain, have garnered considerable interest. This method exhibited significantly high sensitivity, repeatability, and durability in measuring strain. In this study, a thin-film crack sensor was developed using a microstructure. The results exhibited its ability to simultaneously measure the tensile force and pressure in a thin film, further expanding its applications. Furthermore, the strain and pressure characteristics of the sensor were measured and analyzed using an FEM simulation. The proposed method is expected to contribute to the future development of wearable sensors and artificial electronic skin research.

Sheath blight (ShB) significantly threatens rice yield production. However, the underlying mechanism of ShB defence in rice remains largely unknown. Here, we identified a highly ShB-susceptible mutant Ds-m which contained a mutation at the ammonium transporter 1;1 (AMT1;1) D

In this study, we exploited the properties of nature-inspired hierarchical structures to propose surfaces capable of on-demand directional droplet manipulation. A microline polydimethylsiloxane structure that simulated a bamboo leaf was fabricated, and silica particles were embedded onto its surface to create hierarchical structures. The as-fabricated multiscale line structures exhibited anisotropic wetting properties along the advancing direction. As the embedded particle size increased, the perpendicular roll-off angle (ROA) decreased and the anisotropic roll-off characteristic disappeared, adopting lotus-leaf characteristics. Consequently, the fabricated surface exhibited characteristics of both bamboo and lotus leaves. The roll off could be controlled through different ROAs by changing the particles size of silica on the same surface.

In this study, moth-eye-inspired structures (MISs), which improve optical performance of surfaces, were developed to enhance light efficiency in various optical fields. As the polymer-based soft lithography process can easily optimize MIS materials and nanostructures, 12 MIS/inverse MIS (IMIS) surfaces of 300, 500, and 1000 nm composed of polyurethaneacrylate (PUA) and polydimethylsiloxane (PDMS) polymers were fabricated, and a thin octafluorocyclobutane (C4F8) layer was deposited on the surfaces to reduce their surface energies. The results showed that the 300-nm PDMS-MIS showed excellent optical properties with 94.44 % transmittance and 3.28 % reflectance. Additionally, two theoretical phenomena, the diffraction effect and double-slit diffraction, were experimentally demonstrated using three single-wavelength lasers. Subsequently, contact-angle measurements demonstrated all MIS/IMIS surfaces to possess hydrophobic and superhydrophobic properties, which can protect devices from outdoor liquids. Finally, we confirmed the applicability of MIS by attaching it to a cell phone display and an ITO glass, which is used as a substrate in various optical instruments.

Sufficient physical activity (PA) is highly recommended to improve the prognosis after stroke. However, there have been only a few studies evaluating the changes in PA level after stroke.We aimed to identify the changes in PA level between before and after stroke, and to determine the association between PA and adverse outcomes.This observational, retrospective cohort study was performed using the Nationwide Health Insurance Service (NHIS) database in South Korea. Subjects between the ages of 20 to 80 years, who had a first-ever ischemic stroke from 2010 to 2013, were included. Subjects were divided into either the "sufficient" or "insufficient" subgroups, depending on the result of the self-reported PA questionnaire. Adverse outcomes, including all-cause mortality, stroke recurrence, and myocardial infarction (MI), were collected from a post-stroke health checkup to 2017.Of the 34,243 subjects with ischemic stroke, only 21.24% had sufficient PA level after stroke. Among those with insufficient PA level, only 17.34% improved their PA level after stroke. Subjects with sufficient PA level after stroke, regardless of their PA level prior to stroke, showed a lower risk of composite adverse outcomes (adjusted Hazard Ratio [HR], 95% CI: 0.85, 0.80-0.90). Subjects who went from insufficient to sufficient PA level (HR 0.87, 95% CI: 0.81-0.93) showed a significantly lower risk of composite adverse outcomes.Achieving a sufficient PA level after ischemic stroke appears to significantly reduce major adverse events. Further effort is needed to promote the PA level after ischemic stroke.

We report a reliable and robust method for the fabrication of bioinspired superomniphobic surfaces with precise concave-cap-shaped micropillar arrays. This method includes silicon-based conventional microelectromechanical systems (MEMS) and polymer replication processes. We have elucidated two critical cases of fabrication rules for precise micromachining of a negative-shaped bioinspired silicon master. The fabricated polymeric structure replicated from the semipermanent silicon master based on the design rules exhibited high structural fidelity and robustness. Finally, we validated the superomniphobic properties, structural durability, and long-term stability of the fabricated bioinspired surfaces.

In this study, we demonstrate the controllable clustering of thermoresponsive high-aspect-ratio hydrogel pillars by modulating the elastic modulus of the materials. Generally, high-aspect-ratio polymeric pillars readily cluster owing to the effect of capillary force and adhesion. However, this unstable behavior hinders the implementation of various functionalities such as wetting, adhesion, and energy harvesting on surfaces with such pillars. Conversely, clustering behavior may be required in the case of digital microfluidic platforms that grip tiny particles or perform biological and chemical analyses. Therefore, it is necessary to develop a reliable method for controlling the clustering behavior. To this end, we fabricate high-aspect-ratio pillars that exhibit capillary-induced clustering behavior based on the cross-linker density of the thermoresponsive hydrogel and the temperature of the surrounding environment. Through experimental and theoretical analyses, a criterion for controlling the clustering and recovery behavior of the fabricated pillars is determined. The established criterion is employed to fabricate a smart mobile camera lens cover that can produce blurred and deblurred images based on optical variations resulting from the clustering and recovery of the pillars. The results of this study can be used to fabricate high-aspect-ratio polymeric pillars for use in diverse applications.

In this paper, we fabricate and evaluate superhydrophobic surfaces with mushroom-shaped microstructures. Using a silicon master and polymer microstructure patterning, polydimethylsiloxane (PDMS) surfaces bearing mushroom-shaped structures with five different spacing ratios are prepared and tested with water droplets of different temperatures. The fabricated PDMS surfaces demonstrate superhydrophobicity even to high-temperature water droplets with decreased surface tension. We compare the experimental data with the theoretical results calculated based on the Cassie state and Eötvös rule. Our work suggests potential applications to control wettability with liquids of various temperatures.

This study applied a counterpulsation (CP) control method based on a phase-locked loop (PLL) algorithm to synchronise a pneumatic pulsatile ventricular assist device (VAD) with the hearts of patients with arrhythmias. Electrocardiogram data obtained from 40 patients with arrhythmias were used as the input signal for the pulsatile VAD, and the effects of the arrhythmia and the CP control of the VAD on the patients’ haemodynamic states were evaluated. The CP failure rate increased when tachycardia occurred; however, 85 % of the VAD pulses did not occur during heart contraction within 0.1 seconds of the QRS wave. When co-pulsation between the VAD and heart occurred, the aortic pressure did not exceed 140 mmHg and the load on the ventricles remained constant. The PLL CP control algorithm used in this study was able to maintain the CP continuously without increasing the heart load, even when arrhythmias occurred.

Highlights Moth-eye structured polydimethylsiloxane (PDMS) films with different sizes were fabricated to improve the efficiency of perovskite solar cells.The PDMS with 300-nm moth-eye films significantly reduced light reflection at the front of the glass and therefore enhanced the solar cell efficiency of ~ 21%.The PDMS with 1000-nm moth-eye films exhibited beautiful coloration. Electronic supplementary material The online version of this article (10.1007/s40820-019-0284-y) contains supplementary material, which is available to authorized users., Large-area polydimethylsiloxane (PDMS) films with variably sized moth-eye structures were fabricated to improve the efficiency of perovskite solar cells. An approach that incorporated photolithography, bilayer PDMS deposition and replication was used in the fabrication process. By simply attaching the moth-eye PDMS films to the transparent substrates of perovskite solar cells, the optical properties of the devices could be tuned by changing the size of the moth-eye structures. The device with 300-nm moth-eye PDMS films greatly enhanced power conversion efficiency of ~ 21% due to the antireflective effect of the moth-eye structure. Furthermore, beautiful coloration was observed on the 1000-nm moth-eye PDMS films through optical interference caused by the diffraction grating effect. Our results imply that moth-eye PDMS films can greatly enhance the efficiency of perovskite solar cells and building-integrated photovoltaics. Electronic supplementary material The online version of this article (10.1007/s40820-019-0284-y) contains supplementary material, which is available to authorized users.

We report directional switchable adhesion behavior inspired by the locomotion mechanism of gecko lizard. The robust mushroom-like polydimethylsiloxane microline arrays are fabricated by using silicon based over-etching process and replica molding. The line gecko patterns attached to the glass substrate exhibit strong shear adhesion forces in parallel and perpendicular directions with respect to the line direction and high adhesion hysteresis property only in the parallel direction. We have explained the directional adhesion behavior of the line gecko pattern by comparing peeling propagation and normal adhesion phenomenon. Then, we have successfully demonstrated silicon wafer transportation with the line gecko pattern by using directional adhesion behavior of the pattern, which is high shear adhesion force and low peeling force in the parallel direction with respect to the line direction.

To reduce the complications of cardiopulmonary resuscitation (CPR) and increase its effectiveness, the quality of CPR must be measured and feedback provided to the CPR practitioner. Although CPR ancillary devices that attach sensors to measure the compression frequency and depth have been used, these devices did not previously capture the parameters necessary to determine whether the compression position was appropriate, or whether the thorax was deformed by fracture or other causes. In this study, we proposed a system for measuring the mechanical impedance of a patient’s thorax using a load cell and an accelerometer, incorporated into a CPR ancillary device; the mechanical impedance measurements enabled monitoring of the characteristics and deformations of the thorax during in vitro experiments using dummies, and in an animal experiment using two pigs. When CPR was performed, sensors attached to the CPR assist device measured the compression force and movement, and then the single frequency elements of force and velocity at chest compression frequency were calculated. The mechanical impedance can be determined by calculating the ratio of the obtained force to the velocity. Dummies with different elastic moduli show differences in mechanical impedance. In the animal experiment using pigs, the mechanical impedance of the pig’s thorax steadily decreased in response to successive chest compressions. The mechanical impedance system proposed in this study may be useful in the development of new methods to rapidly measure the mechanical properties of the human body or other complex structures.

Animals such as the armadillo and pangolin have natural armor as a mechanical form of protection from predators. Among the several types of armor that exist in nature, structures composed of thin elastomeric substrates with overlapping hard scales can shield underlying soft tissues from physical impacts and localized stresses while maintaining a level of mechanical compliance necessary for natural motions. Here, we design and fabricate a class of artificial armor that derives inspiration from these natural systems. The optimization process involves systematic tests of several design candidates to assess their mechanical stability against different types of mechanical stresses. The resulting platforms provide highly effective protection layers for wearable electronic devices and soft robotic systems with little constraint on their functionality, as demonstrated with representative devices.

Objective: To investigate the feasibility of using the attenuation-based automatic tube potential selection (ATPS) algorithm for cerebral computed tomography angiography (CTA) and to assess radiation dose, vascular attenuation, and image quality compared to a conventional fixed 120-kVp protocol. Materials and Methods: Among 36 volunteers for cerebral CTA, a total of 18 were scanned with fixed 120 kVp and 140 effective mAs using automatic tube current modulation. The other 18 were scanned with an ATPS algorithm. Radiation doses, attenuation, contrast-to-noise ratio (CNR) of the cerebral arteries, subjective scores for arterial attenuation, edge sharpness of the artery, visibility of small arteries, venous contamination, image noise, and overall image quality were compared between the groups. Results: The volume CT dose index and effective dose of the ATPS group were lower than those of the fixed 120-kVp group. The ATPS group had significantly higher arterial attenuation and no significant difference in CNR, compared with the fixed 120- kVp. The ATPS group had higher subjective scores for arterial attenuation, edge sharpness of the artery, visibility of small arteries, and overall image quality. Conclusion: The ATPS algorithm for the cerebral CTA reduced radiation dose by 43% while maintaining image quality and improved the attenuation of cerebral arteries by selecting lower tube potential.

This work reports a facile fabrication method for constructing multifunctional moth-eye TiO2/polydimethylsiloxane (PDMS) pads using soft nano-imprinting lithography and a gas-phase-deposited thin sacrificial layer. Mesoporous TiO2 nanoparticles act as an effective UV filter, completely blocking high-energy UVB light and partially blocking UVA light and forming a robust TiO2/PDMS composite pad by allowing the PDMS solution to easily fill the porous TiO2 network. The paraboloid-shaped moth-eye nanostructures provided high transparency in the visible spectrum and also have self-cleaning effects because of nanoroughness on the surface. Furthermore, we successfully achieved a desired multiscale-patterned surface by partially curing select regions using TiO2/PDMS pads with partial UVA ray blockers. The ability to fabricate multifunctional polymeric pads is advantageous for satisfying increasing demands for flexible and wearable electronics, displays, and solar cells.

In this communication, we present a simple and robust switchable dry adhesion system by using PDMS wrinkled-gecko surface. The PDMS substrate with gecko-inspired wide-tip arrays is a wrinkled area generated by UVO exposure using a shadow mask. The fabricated PDMS wrinkled-gecko device shows high dry adhesion hysteresis on a targeted surface. In the experiments, the difference of adhesion force of wrinkled PDMS surface between adhesion on and off modes increases with longer UVO treatment time. Also, it has durability with mechanical robustness without any defect or decrease in adhesion force even after 100 repeating cycles of the adhesion test. These remarkable properties can be used for precise, green-environmental transporting system with various applications in commercial and research areas.

Large-area polydimethylsiloxane (PDMS) films with variably sized moth-eye structures were fabricated to improve the efficiency of perovskite solar cells. An approach that incorporated photolithography, bilayer PDMS deposition and replication was used in the fabrication process. By simply attaching the moth-eye PDMS films to the transparent substrates of perovskite solar cells, the optical properties of the devices could be tuned by changing the size of the moth-eye structures. The device with 300-nm moth-eye PDMS films greatly enhanced power conversion efficiency of ~ 21% due to the antireflective effect of the moth-eye structure. Furthermore, beautiful coloration was observed on the 1000-nm moth-eye PDMS films through optical interference caused by the diffraction grating effect. Our results imply that moth-eye PDMS films can greatly enhance the efficiency of perovskite solar cells and building-integrated photovoltaics. Highlights: 1 Moth-eye structured polydimethylsiloxane (PDMS) films with different sizes were fabricated to improve the efficiency of perovskite solar cells.2 The PDMS with 300-nm moth-eye films significantly reduced light reflection at the front of the glass and therefore enhanced the solar cell efficiency of ~ 21%.3 The PDMS with 1000-nm moth-eye films exhibited beautiful coloration.