Search

Stretchable devices, garnering increasing attention as next-generation form factors, have a crucial problem in that vertical contraction occurs during stretching, causing image distortion of stretchable displays and discomfort in skin-attached devices. Previous structural strategies to mitigate vertical contraction, such as auxetic reentrants and wrinkles, suffer from the drawback that their structure becomes visible during stretching. In this study, this issue is addressed by unidirectionally aligning nanoscopic cylinders within block copolymer elastomer films. Employing a shear-rolling process at high temperatures on thick films of polystyrene-block-polyisobutylene-block-polystyrene thermoplastic elastomers, macroscopic mechanical anisotropy is achieved, resulting in completely transparent and monotonically stretchable substrates devoid of vertical or depth distortion during deformation. Significantly, the unidirectional orientation of high-modulus cylindrical nanostructures induces macroscopic mechanical anisotropy with a modulus ratio exceeding five times. While the Poisson's ratio of conventional elastic materials hovers around ≈0.5, this mechanical anisotropy minimizes vertical contraction, yielding a Poisson's ratio below 0.07. Moreover, owing to the negligible size of the nanocylinders compared to visible-light wavelengths, the substrate can be monotonically uniaxially stretched while maintaining high transmittance without introducing distortions, surface undulations, or haziness, resulting in distortion-free stretchable substrates., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

The photovoltaic performance of inverted perovskite solar cells (PSCs) relies on effectively managing the interface between the hole extraction layer and the light-absorbing perovskite layer. In this study, we have synthesised (4-(3,6-bis(methylthio)-9H-carbazol-9-yl)butyl)phosphonic acid (MeS-4PACz), which forms a self-assembled monolayer on the fluorine-doped tin oxide (FTO) electrode. The molecule's methylthio substituents generate a favourable interfacial dipole moment and interact with the perovskite layer. This interaction results in well-aligned energy levels among the FTO/SAM/perovskite layers, promoting efficient hole extraction and significantly reducing carrier recombination losses. Additionally, the methylthio groups passivate iodide vacancies and interact with Pb2+ ions of the perovskite, reducing defect-induced trap states and enhancing the crystalline growth of the perovskite layer. Consequently, inverted PSCs incorporating MeS-4PACz achieve a remarkable power conversion efficiency of 25.13%, along with outstanding photostability., (© 2024 Wiley‐VCH GmbH.)

The gyroid structure from self-assembly is highly attractive for optical applications such as photonic crystals and metamaterials. However, due to the direction-dependent nature of these applications, achieving a monograin-level structure over a large area has remained challenging. In this study, the fabrication of unidirectionally oriented anisotropic nanocylinders of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) is reported block copolymer thin films up to a 4-inch scale via a shear-rolling process, followed by solvent annealing to induce phase transition to nearly monograin gyroid structures. Grazing-incidence small-angle X-ray scattering (GISAXS) analysis and cross-sectional scanning electron microscope (SEM) images in the direction parallel to the shear-rolling direction reveal the preferential orientation with the (111) plane onto the YZ axis of the film, while only the (110) plane on the YZ axis of the film is observed in the perpendicular direction, with grain sizes approaching single-grain levels. For metamaterial applications, the PDMS domain is selectively removed, and gold is electroplated to produce monograin gold gyroid films., (© 2024 Wiley‐VCH GmbH.)

Human pluripotent stem cells (hPSCs), encompassing human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), hold immense potential in regenerative medicine, offering new opportunities for personalized cell therapies. However, their clinical translation is hindered by the inevitable reliance on xenogeneic components in culture environments. This study addresses this challenge by engineering a fully synthetic, xeno-free culture substrate, whose surface composition is tailored systematically for xeno-free culture of hPSCs. A functional polymer surface, pGC2 (poly(glycidyl methacrylate-grafting-guanidine-co-carboxylic acrylate)), offers excellent cell-adhesive properties as well as non-cytotoxicity, enabling robust hESCs and hiPSCs growth while presenting cost-competitiveness and scalability over Matrigel. This investigation includes comprehensive evaluations of pGC2 across diverse experimental conditions, demonstrating its wide adaptability with various pluripotent stem cell lines, culture media, and substrates. Crucially, pGC2 supports long-term hESCs and hiPSCs expansion, up to ten passages without compromising their stemness and pluripotency. Notably, this study is the first to confirm an identical proteomic profile after ten passages of xeno-free cultivation of hiPSCs on a polymeric substrate compared to Matrigel. The innovative substrate bridges the gap between laboratory research and clinical translation, offering a new promising avenue for advancing stem cell-based therapies., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

With the rapid development of human-friendly wearable devices, energy storage components are required to have skin-like stretchability or free-form to fit closer and more comfortably to the human body. This study introduces a hierarchically interpenetrated reentrant microcellular structure combined with 2D cellular graphene/MXene/carbon nanotubes (CNTs) and 3D cellular melamine foam. This composite structure works as a stretchable framework of lithium metal composite electrodes to provide stretchability for lithium metal electrodes, which are promising as next-generation energy storage systems. The interpenetrated but independent cellular structures successfully obtain stable structural deformability from the nonconductive and deformable melamine foam, while at the same time, high electrical conductivity, lithiophilicity, and mechanical stability of the graphene/CNT/MXene network serve as a lithium deposition support during the electrodeposition of lithium. The reentrant structure is fabricated by radial compressing the hierarchical cellular structures to take advantage of the structural stretchability of the accordion-like reentrant frameworks. The lithium-deposited composite electrodes exhibit much lower overpotential during Li stripping and plating than lithium metal foil anodes and show stable electrochemical performances under 30% of mechanical strain. The reentrant microcellular electrodes offer great potential for advanced designs of lithium metal electrodes for stretchable batteries with high energy density., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)

The growth of lithium (Li) dendrites reduces the lifespan of Li-metal batteries and causes safety issues. Herein, hierarchically porous aramid nanofiber separators capable of effectively suppressing the Li dendrite growth while maintaining highly stable cycle performances at high charge/discharge rates are reported. A two-step solvent exchange process combined with reprotonation-mediated self-assembly is utilized to control the bimodal porous structure of the separators. In particular, when ethanol and water are used sequentially, aramid nanofibers form hierarchical porous structures containing nanopores in macroporous polymer frameworks to yield a mechanically robust membrane with high porosity of 97% or more. The optimized samples exhibit high ionic conductivities of 1.87-4.04 mS cm -1 and high Li-ion transference numbers of 0.77-0.84 because of the ultrahigh porosity and selective affinity to anions. Li-metal symmetric cells do not show any noticeable presence of dendrites after 100 cycles, and they operate stably for more than 1500 cycles even under extreme conditions with a high current density of >20 mA cm -2 . In addition, the LiFePO 4 /Li full cell retains 86.3% of its capacity after 1000 cycles at a charge rate of 30 C., (© 2022 Wiley-VCH GmbH.)

Interest in resistive random access memory (RRAM) has grown rapidly in recent years for realizing ultrahigh density data storage devices. However, sneak currents in these devices can result in misreading of the data, thus limiting the applicability of RRAM. Complementary resistive switching (CRS) memory consisting of two antiserial RRAMs can considerably reduce sneak currents; however, complicated device architectures and manufacturing processes still remain as challenges. Herein, an effective and simple approach for fabricating CRS memory devices using self-assembled block copolymer micelles is reported. Cu ions are selectively placed in the core of polystyrene-block-poly(2-vinylpyridine) spherical micelles, and a hexagonally packed micelle monolayer is prepared through spin-coating. The micelle monolayer can be a symmetrical resistive switching layer, because the micelles and Cu act as dielectric and active metals in memory devices, respectively. The locally enhanced electric field and Joule heating achieved by the structured Cu atoms inside the micelles promote metal ionization and ion migration in a controlled manner, thus allowing for position selectivity during resistive switching. The micelle-based memory device exhibits stable and reliable CRS behavior, with a nonoverlapping and narrow distribution of threshold voltages. Therefore, this approach is promising for fabricating CRS memory devices for high-performance and ultrahigh-density RRAM applications., (© 2022 Wiley-VCH GmbH.)

With the miniaturization of personal wearable electronics, considerable effort has been expended to develop high-performance flexible/stretchable energy storage devices for powering integrated active devices. Supercapacitors can fulfill this role owing to their simple structures, high power density, and cyclic stability. Moreover, a high electrochemical performance can be achieved with flexible/stretchable supercapacitors, whose applications can be expanded through the introduction of additional novel functionalities. Here, recent advances in and future prospects for flexible/stretchable supercapacitors with innate functionalities are covered, including biodegradability, self-healing, shape memory, energy harvesting, and electrochromic and temperature tolerance, which can contribute to reducing e-waste, ensuring device integrity and performance, enabling device self-charging following exposure to surrounding stimuli, displaying the charge status, and maintaining the performance under a wide range of temperatures. Finally, the challenges and perspectives of high-performance all-in-one wearable systems with integrated functional supercapacitors for future practical application are discussed., (© 2020 Wiley-VCH GmbH.)

From graphene oxide wrapped iron oxide particles with etching/reduction process, high-performance anode and cathode materials of lithium-ion hybrid supercapacitors are obtained in the same process with different etching conditions, which consist of partially etched crumpled graphene (CG) wrapped spiky iron oxide particles (CG@SF) for a battery-type anode, and fully etched CG for a capacitive-type cathode. The CG is formed along the shape of spikily etched particles, resulting in high specific surface area and electrical conductivity, thus the CG-based cathode exhibits remarkable capacitive performance of 210 F g -1 and excellent rate capabilities. The CG@SF can also be ideal anode materials owing to spiky and porous morphology of the particles and tightly attached crumpled graphene onto the spiky particles, which provides structural stability and low contact resistance during repetitive lithiation/delithiation processes. The CG@SF anode shows a particularly high capacitive performance of 1420 mAh g -1 after 270 cycles, continuously increases capacity beyond the 270th cycle, and also maintains a high capacity of 170 mAh g -1 at extremely high speeds of 100 C. The full-cell exhibits a higher energy density up to 121 Wh kg -1 and maintains high energy density of 60.1 Wh kg -1 at 18.0 kW kg -1 . This system could thus be a practical energy storage system to fill the gap between batteries and supercapacitors., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Highly ordered perpendicular orientation and straightly parallel orientation coexisting polystyrene-block-polydimethylsiloxane (PS-b-PDMS) cylindrical microdomains with 10 nm width can be realized by using polyvinyl acetate as a partially dewetted topcoat and solvent annealing with acetone vapor. During solvent annealing, the swelled topcoat begins to dewet and the dewetting rim sweeps the surface of the block copolymer films to align the cylindrical microdomains with the direction of dewetting propagation. However, the wetted region of the topcoat/PS-b-PDMS film forms with a perpendicular orientation due to reduced surface tension and sufficient concentration gradient in the solvent evaporation step. The orientational changes (perpendicular/straightly parallel orientation) in the dewetted/wetted area are also investigated according to the vapor pressure of solvent annealing. The degree of directionality of the swept PS-b-PDMS films according to the distance from the dewetting front, which is equivalent with time after sweeping, is examined. To control the direction of dewetting and complex structures within a specific area, an imprinting process is introduced to form topographical line-space patterns in the topcoat and perpendicular/parallel orientation of BCP patterns in the line-space patterns, respectively., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Sub-10 nm Graphene Nanoribbon Arrays are fabricated over large areas by etching CVD-grown graphene. A mask is used made by the directed self-assembly of a cylindrical PS-b-PDMS block copolymer under solvent annealing guided by a removable template. The optimized solvent annealing process, surface-modified removable polymeric templates, and high Flory-Huggins interaction parameters of the block copolymer enable a highly aligned array of nanoribbons with low line edge roughness to be formed. This leads to a higher on/off ratio and stronger temperature dependence of the current for nanoribbon FETs, and a photocurrent which is 30 times larger compared to unpatterned graphene., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) block copolymers with a period as low as 13 nm have been self-assembled on a template formed from PS-b-PDMS of a 34–40 nm period, which is itself templated by micron-scale substrate features prepared using conventional lithography. This hierarchical process provides a simple method for directing the self-assembly of sub-10 nm features and registering them on the substrate.