Patterning of Metal Halide Perovskite Thin Films and Functional Layers for Optoelectronic Applications.

In recent years, metal halide perovskites have received significant attention as materials for next-generation optoelectronic devices owing to their excellent optoelectronic properties. The unprecedented rapid evolution in the device performance has been achieved by gaining an advanced understanding of the composition, crystal growth, and defect engineering of perovskites. As device performances approach their theoretical limits, effective optical management becomes essential for achieving higher efficiency. In this review, we discuss the status and perspectives of nano to micron-scale patterning methods for the optical management of perovskite optoelectronic devices. We initially discuss the importance of effective light harvesting and light outcoupling via optical management. Subsequently, the recent progress in various patterning/texturing techniques applied to perovskite optoelectronic devices is summarized by categorizing them into top-down and bottom-up methods. Finally, we discuss the perspectives of advanced patterning/texturing technologies for the development and commercialization of perovskite optoelectronic devices.

Crack-Based Sensor with Microstructures for Strain and Pressure Sensing.

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.

Ultrasensitive and Highly Stretchable Multiple-Crosslinked Ionic Hydrogel Sensors with Long-Term Stability.

Flexible hydrogels are receiving significant attention for their application in wearable sensors. However, most hydrogel materials exhibit weak and one-time adhesion, low sensitivity, ice crystallization, water evaporation, and poor self-recovery, thereby limiting their application as sensors. These issues are only partly addressed in previous studies. Herein, a multiple-crosslinked poly(2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide-co-acrylamide) (P(SBMA-co-AAm)) multifunctional hydrogel is prepared via a one-pot synthesis method to overcome the aforementioned limitations. Specifically, ions, glycerol, and 2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide are incorporated to reduce the freezing point and improve the moisture retention ability. The proposed hydrogel is superior to existing hydrogels because it exhibits good stretchability (a strain of 2900%), self-healing properties, and transparency through effective energy dissipation in its dynamic crosslinked network. Further, 2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide as a zwitterion monomer results in an excellent gauge factor of 43.4 at strains of 1300-1600% by improving the ion transportability and achieving a strong adhesion of 20.9 kPa owing to the dipole-dipole moment. The proposed hydrogel is promising for next-generation biomedical applications, such as soft robots, and health monitoring.

Bioinspired On-Demand Directional Droplet Manipulation Surfaces.

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.

Silver-Reduced Poly(Ethylene Glycol) Diacrylate Composites with Microline Arrays for Directional Bending Sensors.

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.

Efficacy and Safety of Botulinum Toxin Type A (NABOTA) for Post-stroke Upper Extremity Spasticity: A Multicenter Phase IV Trial.

OBJECTIVE: To evaluate the efficacy and safety of Daewoong botulinum toxin type A (NABOTA) after its launch in South Korea. METHODS: This prospective, multicenter, open-label phase IV clinical trial included 222 patients with stroke. All patients visited the clinic at baseline and at weeks 4, 8, and 12 after injection of upto 360 units of NABOTA into the wrist, elbow, and finger flexor muscles at the first visit. The primary outcome was the change in Modified Ashworth Scale (MAS) score for the wrist flexor muscles between baseline and week 4. The secondary outcomes were the changes in MAS, Disability Assessment Scale (DAS), and Caregiver Burden Scale (CBS) scores between baseline and each visit, and the Global Assessment Scale (GAS) score at week 12. RESULTS: There was a statistically significant decrease in the MAS score for the wrist flexors between baseline and week 4 (-0.97±0.66, p<0.001). Compared with baseline, the MAS, DAS and CBS scores improved significantly during the study period. The GAS was rated as very good or good by 86.8% of physicians and by 60.0% of patients (or caregivers). The incidence of adverse events was 14.4%, which is smaller than that in a previous trial. CONCLUSION: NABOTA showed considerable efficacy and safety in the management of upper limb spasticity in stroke patients.

Robust and Transparent Lossless Directional Omniphobic Ultra-Thin Sticker-Type Film with Re-entrant Micro-Stripe Arrays.

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.

Self-Assembled Artificial Nanocilia Actuators.

Self-assembly of nanoparticles (NPs) is a powerful route to constructing higher-order structures. However, the programmed self-assembly of NPs into non-close-packed, 3D, shape-morphing nanocilia arrays remains elusive, whereas dynamically actuated nanometer cilia are universal in living systems. Here, a programmable self-assembly strategy is presented that can direct magnetic NPs into a highly ordered responsive artificial nanocilia actuator with exquisite nanometer 3D structural arrangements. The self-assembled artificial NP cilia can maintain their structural integrity through the interplay of interparticle interactions. Interestingly, the nanocilia can exhibit a field-responsive actuation motion through "rolling and sliding" between assembled NPs rather than bending the entire ciliary beam. It is demonstrated that oleic acid coated over the NPs acts as a lubricating bearing and enables the rolling/sliding-based actuation of the cilia.

Ammonium transporter 1 increases rice resistance to sheath blight by promoting nitrogen assimilation and ethylene signalling.

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) D358 N. AMT1;1 D358 N interacts with AMT1;1, AMT1;2 and AMT1;3 to inhibit the ammonium transport activity. The AMT1 RNAi was more susceptible and similar to the AMT1;1 D358 N mutant; however, plants with higher NH4+ uptake activity were less susceptible to ShB. Glutamine synthetase 1;1 (GS1;1) mutant gs1;1 and overexpressors (GS1;1 OXs) were more and less susceptible to ShB respectively. Furthermore, AMT1;1 overexpressor (AMT1;1 OX)/gs1;1 and gs1;1 exhibited a similar response to ShB, suggesting that ammonium assimilation rather than accumulation controls the ShB defence. Genetic and physiological assays further demonstrated that plants with higher amino acid or chlorophyll content promoted rice resistance to ShB. Interestingly, the expression of ethylene-related genes was higher in AMT1;1 OX and lower in RNAi mutants than in wild-type. Also, ethylene signalling positively regulated rice resistance to ShB and NH4+ uptake, suggesting that ethylene signalling acts downstream of AMT and also NH4+ uptake is under feedback control. Taken together, our data demonstrated that the AMT1 promotes rice resistance to ShB via the regulation of diverse metabolic and signalling pathways.

Capillary-Induced Clustering of Thermoresponsive Micropillars.

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.

Physical activity after ischemic stroke and its association with adverse outcomes: A nationwide population-based cohort study.

BACKGROUND: 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. AIMS: We aimed to identify the changes in PA level between before and after stroke, and to determine the association between PA and adverse outcomes. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Reliable and Robust Fabrication Rules for Springtail-Inspired Superomniphobic Surfaces.

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.

Optimization of Shapes and Sizes of Moth-Eye-Inspired Structures for the Enhancement of Their Antireflective Properties.

Novel antireflective (AR) structures have attracted tremendous attention and been used in various applications such as solar cells, displays, wearable devices, and others. They have also stimulated the development of several other methods, including moth-eye-inspired technologies. However, the analyses of the shapes and sizes of nanostructures remain a critical issue and need to be considered in the design of effective AR surfaces. Herein, moth-eye and inverse-moth-eye patterned polyurethane-acrylate (PUA) structures (MPS and IMPS) with three different sizes are analyzed and compared to optimize the designed nanostructures to achieve the best optical properties pertaining to maximum transmittance and minimum reflectance. We fabricated moth-eye-inspired conical structures with three different sizes using a simple and robust fabrication method. Furthermore, the fabricated surfaces of the MPS and IMPS structures were analyzed based on the experimental and theoretical variation influences of their optical properties according to their sizes and shapes. As a result of these analyses, we herein propose a standard methodology based on the optimal structure of IMPS structure with a 300 nm diameter.

Selective Liquid Sliding Surfaces with Springtail-Inspired Concave Mushroom-Like Micropillar Arrays.

Herein, a mushroom-like reentrant structure is proposed, inspired by springtails, to create a selective liquid sliding surface by implementing a simple yet sturdy silicon fabrication and lithography method. The fabricated arrays display high structural fidelity, presenting a novel geometry of a concave tip. The mushroom-like head shape of these structures is found to have superomniphobicity, which is independent of a variation of temperatures for even low surface tension liquids such as mineral oil. A design rule for the novel cap of the proposed structures, which results in a selective liquid sliding property with deionized (DI) water and mineral oil, is also investigated. It is demonstrated that oil starts to slide at a roll-off angle (ROA) 10° and then DI water rolls off at ROA 15° on the same fabricated transparent and flexible surface with repeatable durability.

Utility of CPR Machine Power and Change in Right Atrial Pressure for Estimating CPR Quality.

When a cardiac arrest occurs, it is necessary to perform cardiopulmonary resuscitation (CPR) as soon as possible. This requires maintaining the pressure depth at 5 cm at a rate of 100 cpm. For CPR machines, which are frequently used in ambulances, the return of spontaneous circulation (ROSC) is not superior to that of manual CPR, although CPR machines can maintain the compression rate and reciprocal distance of the compression plate more accurately. When the thoracic cavity is deformed due to repeated chest compressions, CPR machines must be adjusted. It is necessary to develop a method for measuring whether adequate CPR is achieved using CPR machines. CPR was performed on two pigs with a CPR machine, commencing 1 minute after the heart was stopped. Four CPR modes were used, with compression rates of 60 or 100 cpm and compression depths of 3 or 5 cm. The CPR machine was equipped with a load cell for measuring compression force, and a potentiometer for measuring compression depth. The measurement results obtained from the sensor were used to calculate the frequency components. The compression force and depth data were used to calculate the mechanical power of the CPR machine and mechanical impedance of the thoracic cavity. Changes in end-tidal carbon dioxide (ETCO2), coronary perfusion pressure (CPP), carotid blood flow (CBF), and right atrial pressure (RAP) were measured during performance of CPR; change in RAP refers to variation therein with chest compressions. Continuous CPR in both animals resulted in deformation of the chest cavity and a steady decline in impedance. The correlation between CPR power and change in RAP was 0.78, and that between compression force and CBF was 0.64. Impedance was not correlated with blood pressure or CBF. When the condition of the animal deteriorated due to cardiac arrest, the CPP decreased and ETCO2 increased. The CPR power and RAP varied according to the CPR mode rather than the condition of the animal. Measuring the CPR machine power does not require a separate procedure, such as catheter intubation, so should be suitable as an index of the quality of CPR in emergency situations.

Moth-eye Structured Polydimethylsiloxane Films for High-Efficiency Perovskite Solar Cells.

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.

Tunable Multimodal Drop Bouncing Dynamics and Anti-Icing Performance of a Magnetically Responsive Hair Array.

Anti-icing materials that can efficiently limit ice formation have a strong potential to replace existing anti-icing techniques, such as Joule heating, chemical release, or mechanical removal, which are usually inefficient, expensive, and environmentally harmful. In this study, an anti-icing material based on a magnetically responsive hierarchical hair array that can actively modulate drop bouncing dynamics is presented. The magnetically responsive hair array exhibits an immediate and reversible structural bending motion in response to an external magnetic field. The array also exhibits superhydrophobicity, regardless of its tilt angle, due to the tapered geometry of the hairs and the multiscale surface roughness of the array. Due to its dynamic structure and water-repellent characteristics, the array can induce distinct multiple modes of drop bouncing behavior by adjusting its structural bending state in a reversible fashion. Three different types of bouncing behavior, namely, quasi-pancake bouncing, directional bouncing, and macrotexture-induced droplet fragmentation, can be obtained with the vertical, tilted, and fully bent hair arrays, respectively. We demonstrate that the dynamically controllable drop bouncing behavior of the magnetically responsive hierarchical array enables the efficient and robust prevention of ice formation and accumulation.

Multifunctional Moth-Eye TiO2/PDMS Pads with High Transmittance and UV Filtering.

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.

3D tissue formation by stacking detachable cell sheets formed on nanofiber mesh.

We present a novel approach for assembling 3D tissue by layer-by-layer stacking of cell sheets formed on aligned nanofiber mesh. A rigid frame was used to repeatedly collect aligned electrospun PCL (polycaprolactone) nanofiber to form a mesh structure with average distance between fibers 6.4 µm. When human umbilical vein endothelial cells (HUVECs), human foreskin dermal fibroblasts, and skeletal muscle cells (C2C12) were cultured on the nanofiber mesh, they formed confluent monolayers and could be handled as continuous cell sheets with areas 3 × 3 cm2 or larger. Thicker 3D tissues have been formed by stacking multiple cell sheets collected on frames that can be nested (i.e. Matryoshka dolls) without any special tools. When cultured on the nanofiber mesh, skeletal muscle, C2C12 cells oriented along the direction of the nanofibers and differentiated into uniaxially aligned multinucleated myotube. Myotube cell sheets were stacked (upto 3 layers) in alternating or aligned directions to form thicker tissue with ∼50 µm thickness. Sandwiching HUVEC cell sheets with two dermal fibroblast cell sheets resulted in vascularized 3D tissue. HUVECs formed extensive networks and expressed CD31, a marker of endothelial cells. Cell sheets formed on nanofiber mesh have a number of advantages, including manipulation and stacking of multiple cell sheets for constructing 3D tissue and may find applications in a variety of tissue engineering applications.