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The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area. Multiplex lithography is a technique that can be used to fabricate complex soft materials. Here, the authors develop a method to prepare multilevel multiscale structures and demonstrate its application on polymer electrolyte membrane fuel cells which display decreased membrane resistance and increased electrochemical active surface area.

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. 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.

Guided cracks were successfully generated in an electrode using the concentrated surface stress of a prism-patterned Nafion membrane. An electrode with guided cracks was formed by stretching the catalyst-coated Nafion membrane. The morphological features of the stretched membrane electrode assembly (MEA) were investigated with respect to variation in the prism pattern dimension (prism pitches of 20 μm and 50 μm) and applied strain ( S  ≈ 0.5 and 1.0). The behaviour of water on the surface of the cracked electrode was examined using environmental scanning electron microscopy. Guided cracks in the electrode layer were shown to be efficient water reservoirs and liquid water passages. The MEAs with and without guided cracks were incorporated into fuel cells, and electrochemical measurements were conducted. As expected, all MEAs with guided cracks exhibited better performance than conventional MEAs, mainly because of the improved water transport.

Air pollution by particulate matter (PM) in the air including PM1.0, PM2.5, and PM10, which are categorized by particle size, is a critical global environmental issue, harming the climate, ecosystems, and human health. Especially, ultrafine dust including PM1.0 and PM2.5 poses significant human health risks. Commercial fabric‐based filters effectively trap PMs but cause high‐pressure drop and limited filter capacity and reusability. Electrospun nanofiber filters address some issues but have low mechanical strength, toxic exposure risks, long fabrication times, and restrained reusability. Herein, a reusable and transparent impaction‐based PM filter using a UV‐curable polymeric stencil with micro apertures is proposed. The polymeric stencil filters achieve high filter efficiency (68–94%), superior filter capacity, and low‐pressure drop (<64 Pa). The polymeric stencil filters can be easily cleaned with water or ethanol and remain stable under extreme temperatures (−196 to 450 °C) with slight shrinkage (0–7%). The polymeric stencil filters can be broadly utilized for not only industrial, indoor, and vehicle filters but also transparent and flexible facial health masks. A reusable impaction‐based filter using micro‐apertured polymeric stencils for capturing particulate matter is developed. The stencil filter exhibits low‐pressure drop, and high filter capacity and efficiency. And, the flexible and transparent filters can be used for human health masks, which are stable even under extreme temperature conditions.

Despite rapid advancements in anion exchange membrane water electrolysis (AEMWE) technology, achieving pure water‐fed AEMWE remains critical for system simplification and cost reduction. Under pure water‐fed conditions, electrochemical reactions occur solely at active sites connected to ionic networks. This study introduces an eco‐friendly patterning technique leveraging membrane swelling properties by applying mechanical stress during dehydration under fixed constraints. The method increases active sites by creating additional hydroxide ion pathways at the membrane‐electrode interface, eliminating the need for additional ionomers in the electrode. This innovation facilitates ion conduction via locally shortened pathways. Membrane electrode assemblies (MEAs) with patterned commercial membranes demonstrated significantly improved performance and durability compared to MEAs with conventional catalyst‐coated substrates and flat membranes under pure water‐fed conditions. The universal applicability of this technique was confirmed using in‐house fabricated anion exchange membranes, achieving exceptional current densities of 13.7 A cm−2 at 2.0 V in 1.0 M potassium hydroxide (KOH) and 2.8 A cm−2 at 2.0 V in pure water at 60 °C. Furthermore, the scalability of the technique was demonstrated through successful fabrication and operation of large‐area cells. These findings highlight the potential of this patterning method to advance AEMWE technology, enabling practical applications under pure water‐fed conditions. An eco‐friendly large‐area patterning technique is developed that employs membrane swelling properties. With the advantages of facilitated ion conduction and secured more active sites, excellent performance of AEMWE with 13.7 A cm−2 (1 M KOH) and 2.8 A cm−2 (pure water) at 2.0 V is achieved. The practical applicability of the method is validated with a large‐area single‐cell (68.75 cm2)

For further commercializing proton-exchange membrane fuel cells, it is crucial to attain long-term durability while achieving high performance. In this study, a strategy for modifying commercial Nafion membranes by introducing ultrathin multiwalled carbon nanotubes (MWCNTs)/CeO2 layers on both sides of the membrane was developed to construct a mechanically and chemically reinforced membrane electrode assembly. The dispersion properties of the MWCNTs were greatly improved through chemical modification with acid treatment, and the mixed solution of MWCNTs/CeO2 was uniformly prepared through a high-energy ball-milling process. By employing a spray-coating technique, the ultrathin MWCNTs/CeO2 layers were introduced onto the membrane surfaces without any agglomeration problem because the solvent rapidly evaporated during the layer-by-layer stacking process. These ultrathin and highly dispersed MWCNTs/CeO2 layers effectively reinforced the mechanical properties and chemical durability of the membrane while minimizing the performance drop despite their non-ion-conducting properties. The characteristics of the MWCNTs/CeO2 layers and the reinforced Nafion membrane were investigated using various in situ and ex situ measurement techniques; in addition, electrochemical measurements for fuel cells were conducted.

Polymer electrolyte membrane fuel cells (PEMFCs) suffer from severe performance degradation when operating under harsh conditions such as fuel starvation, shut‐down/start‐up, and open circuit voltage. A fundamental solution to these technical issues requires an integrated approach rather than condition‐specific solutions. In this study, an anode catalyst based on Pt nanoparticles encapsulated in a multifunctional carbon layer (MCL), acting as a molecular sieve layer and protective layer is designed. The MCL enabled selective hydrogen oxidation reaction on the surface of the Pt nanoparticles while preventing their dissolution and agglomeration. Thus, the structural deterioration of a membrane electrode assembly can be effectively suppressed under various harsh operating conditions. The results demonstrated that redesigning the anode catalyst structure can serve as a promising strategy to maximize the service life of the current PEMFC system. In this study, an anode catalyst based on Pt nanoparticles encapsulated in a multifunctional carbon layer (MCL) is redesigned, acting as a molecular sieve layer and protective layer. Electrochemical studies have shown that MCL helped suppress the structural deterioration of a membrane electrode assembly and maximize the service life of the PEMFC system.

This article reports on a flexible polymer electrolyte membrane fuel cell (PEMFC) with a pre-bent flow field. The performances in the flat and bent positions were lower and higher, respectively than that of the traditional flexible fuel cells. The low performance in the flat position was attributed to the void space induced incomplete contact at the interface of the membrane electrode assembly (MEA) and flow-field plates, which resulted in poor performance due to the high ohmic resistance (5.85 Ω cm 2 ) and faradaic resistance (4.17 Ω cm 2 ). However, when bending stress was applied to the MEA, a decreased ohmic resistance (0.954 Ω cm 2 ), faradaic resistance (0.737 Ω cm 2 ), and an enhanced power density (88.7 mW/cm 2 ) were observed because of the improved interfacial contact property between the MEA and the flow-field plates from the increased compressive stress. These experimental results were further analyzed and visualized with aid of the finite element analysis. Despite the relatively low performance in the flat shape, the proposed pre-bent design of the flexible PEMFC possesses promising applicability especially in flexible electronics where the curved shapes are highly required.

In the original publication, the equal contribution information was not available in first page of the article.

The instability of polymeric membranes with nano- and micro-sized apertures has been regarded as one of the main reasons behind realizing ultra-thin membranes with apertures. As is well known, when the thickness of the membrane gets thinner or the aperture size gets smaller, the possibility of geometrical deformation or structural damage by collapse or fracture increases. Herein, we suggest the design rules for the stability of polymeric membranes possessing 1D nano-line patterns monolithically constructed on micro-aperture supporting layers. The proposed theoretical model, which has been thoroughly demonstrated and analyzed based on both theoretical and experimental approaches, provides stability criteria for lateral collapse and vertical fracture of ultra-thin membranes with apertures.