The Mechanical Aspects of Formation and Application of PDMS Bilayers Rolled into a Cylindrical Structure

A polydimethylsiloxane (PDMS) film with its surface being oxidized by a plasma treatment or a UV-ozone (UVO) treatment, that is, a bilayer made of PDMS and its oxidized surface layer, is known to roll into a cylindrical structure upon exposure to the chloroform vapor due to the mismatch in the swelling ratio between PDMS and the oxidized layer by the chloroform vapor. Here we analyzed the formation of the rolled bilayer with the mechanical aspects: how the mismatch in the swelling ratio of the bilayer induces rolling of the bilayer, why any form of trigger that breaks the symmetry in the in-plane stress level is needed to roll the bilayer uniaxially, why the rolled bilayer does not unroll in the dry state when there is no more mismatch in the swelling ratio, and how the measured curvature of rolled bilayer matches well with the prediction by the theory. Moreover, for the use of the rolled bilayer as the channel of the microfluidic device, we examined whether the rolled bilayer deforms or unrolls by the flow of the aqueous solution that exerts the circumferential stress on the rolled bilayer

Hierarchical Optimization of High-Performance Biomimetic and Bioinspired Membranes

Biomimetic and bioinspired membranes have emerged as an innovative platform for water purification and aqueous separations. They are inspired by the exceptional water permeability (∼10 9 water molecules per second per channel) and perfect selectivity of biological water channels, aquaporins. However, only few successes have been reported for channel-based membrane fabrication due to inherent challenges of realizing coherence between channel design at the angstrom level and development of scalable membranes that maintain these molecular properties at practice-relevant scales. In this article, we feature recent progress toward practical biomimetic membranes, with the review organized along a hierarchical structural perspective that biomimetic membranes commonly share. These structures range from unitary pore shapes and tubular hydrophobic channel geometries to self-assembled bilayer structures and finally to macroscale membranes covering a size range from the angstrom, to the micrometer scale, and finally to the centimeter and larger scales. To maximize the advantage of water channel implementation into membranes, each feature needs to be optimized in an appropriate manner that provides a path to successful scale-up to achieve high performance in practical biomimetic and bioinspired membranes. © 2018 American Chemical Society.11Nsciescopu

Metal-Free Synthesis of Indolopyrans and 2,3-Dihydrofurans Based on Tandem Oxidative Cycloaddition

The synthesis of versatile scaffold indolopyrans based on C-C radical-radical cross-coupling under metal-free conditions is described. The reaction involving single electron transfer between coupling partners followed by cage collapse allows highly selective cross-coupling while employing only equimolar amounts of coupling partners. Moreover, the mechanistic manifold was expanded for the functionalization of enamines to give the stereoselective synthesis of 2,3-dihydrofurans. This iodine-mediated oxidative coupling features mild conditions and fast reaction kinetics

Hierarchical Optimization of High-Performance Biomimetic and Bioinspired Membranes

Biomimetic and bioinspired membranes have emerged as an innovative platform for water purification and aqueous separations. They are inspired by the exceptional water permeability (∼10 9 water molecules per second per channel) and perfect selectivity of biological water channels, aquaporins. However, only few successes have been reported for channel-based membrane fabrication due to inherent challenges of realizing coherence between channel design at the angstrom level and development of scalable membranes that maintain these molecular properties at practice-relevant scales. In this article, we feature recent progress toward practical biomimetic membranes, with the review organized along a hierarchical structural perspective that biomimetic membranes commonly share. These structures range from unitary pore shapes and tubular hydrophobic channel geometries to self-assembled bilayer structures and finally to macroscale membranes covering a size range from the angstrom, to the micrometer scale, and finally to the centimeter and larger scales. To maximize the advantage of water channel implementation into membranes, each feature needs to be optimized in an appropriate manner that provides a path to successful scale-up to achieve high performance in practical biomimetic and bioinspired membranes. © 2018 American Chemical Society.11Nsciescopu

3D Cell Printing of Islet-laden Pancreatic Tissue-derived Extracellular Matrix Bioink Constructs for Enhancing Pancreatic Functions

Type 1 diabetes mellitus (T1DM) is a form of diabetes that inhibits or halts insulin production in the pancreas. Although various therapeutic options are applied in clinical settings, not all patients are treatable with such methods due to the instability of the T1DM or the unawareness of hypoglycemia. Islet transplantation using a tissue engineering-based approach may mark a clinical significance, but finding ways to increase the function of islets in 3D constructs is a major challenge. In this study, we suggest pancreatic tissue-derived extracellular matrix as a potential candidate to recapitulate the native microenvironment in transplantable 3D pancreatic tissues. Notably, insulin secretion and the maturation of insulin-producing cells derived from human pluripotent stem cells were highly up-regulated when cultured in pdECM bioink. In addition, co-culture with human umbilical vein-derived endothelial cells decreased the central necrosis of islets under 3D culture conditions. Through the convergence of 3D cell printing technology, we validated the possibility of fabricating 3D constructs of a therapeutically applicable transplant size that can potentially be an allogeneic source of islets, such as patient-induced pluripotent stem cell-derived insulin-producing cells.11Nsciescopu

Deformable Joule Heating Electrode Based on Hybrid Layers of Silver Nanowires and Carbon Nanotubes and its Application in a Refreshable Multi‐Cell Braille Display

Joule heating electrodes (JHEs) are required for thermal actuation systems. A highly stretchable, patternable, and low-voltage operating JHE based on hybrid layers of silver nanowires and carbon nanotubes are reported. The conductive layers are applied on a locally pre-strained bistable electroactive polymer (BSEP) membrane to form a wrinkled conductive surface with a low resistance of 300 Ω/sq, and subsequently patterned to a serpentine trace by laser engraving. The resistance of the resulting JHE electrode remains nearly unchanged up to 80−90% area strain. By applying a voltage of 7 − 9 V to the electrode, the temperature of the BSEP membrane increased to ~60 °C, well above the polymer's phase transition temperature of 46 °C, thereby lowering its modulus by a factor of 103. An electronic Braille device based on the JHEs on a BSEP membrane is assembled with a diaphragm chamber. The electrode is patterned into 3 × 2 individually addressable pixels. Through Joule heating of the pixels and local expansion of the BSEP membrane using a pneumatic pressure, the pixels deformed out of the plane by over 0.5 mm to display Braille letters. The Braille content can be refreshed for 20 000 cycles at the same operating voltage

Longitudinal immune kinetics of COVID-19 booster versus primary series vaccination: Insight into the annual vaccination strategy

Background: Data on the durability of booster dose immunity of COVID-19 vaccines are relatively limited. Methods: Immunogenicity was evaluated for up to 9–12 months after the third dose of vaccination in 94 healthy adults. Results: Following the third dose, the anti-spike immunoglobulin G (IgG) antibody response against the wild-type was boosted markedly, which decreased gradually over time. However, even 9–12 months after the booster dose, both the median and geometric mean of anti-spike IgG antibody levels were higher than those measured 4 weeks after the second dose. Breakthrough infection during the Omicron-dominant period boosted neutralizing antibody titers against Omicron sublineages (BA.1 and BA.5) and the ancestral strain. T-cell immune response was efficiently induced and maintained during the study period. Conclusions: mRNA vaccine booster dose elicited durable humoral immunity for up to 1 year after the third dose and T-cell immunity was sustained during the study period, supporting an annual COVID-19 vaccination strategy

Organic Solvent Dispersible MXene Integrated Colloidal Quantum Dot Photovoltaics

Despite recent advances in colloidal quantum dot (CQD) photovoltaics, several challenges persist and hinder further improvements. In particular, the Fermi level mismatch between the iodide-treated photoactive and thiol-treated hole-transporting CQD layers creates an unfavorable energy band for hole collection. Furthermore, the numerous surface cracks in the thiol-treated CQD layer facilitate direct contact between the photoactive CQD layer and the metal electrode, consequently leading to reduced device performance. To address these issues, a polycatechol functionalized MXene (PCA-MXene) that can serve both as a dopant and an interlayer for CQD photovoltaics is developed. By achieving a uniformly dispersed mixture in a butylamine solvent, PCA-MXene enables the effective combination of MXene and CQDs. This results in the modification of the work function of CQDs and the modulation of the energy band alignment, ultimately promoting enhanced hole extraction. Moreover, the PCA-MXene employed as an interlayer effectively covers the surface cracks present in the thiol-treated CQD layer. This coverage inhibits both metal electrode penetration and moisture intrusion into the device. Owing to these advantages, the CQD photovoltaics incorporating PCA-MXene achieve a power conversion efficiency (PCE) of 13.6%, accompanied by enhanced thermal stability, in comparison to the reference device with a PCE of 12.8%. © 2023 Wiley-VCH GmbH.FALS

Dehydrated Biomimetic Membranes with Skinlike Structure and Function

Novel vapor-permeable materials are sought after for applications in protective wear, energy generation, and water treatment. Current impermeable protective materials effectively block harmful agents but trap heat due to poor water vapor transfer. Here we present a new class of materials, vapor permeable dehydrated nanoporous biomimetic membranes (DBMs), based on channel proteins. This application for biomimetic membranes is unexpected as channel proteins and biomimetic membranes were assumed to be unstable under dry conditions. DBMs mimic human skin’s structure to offer both high vapor transport and small molecule exclusion under dry conditions. DBMs feature highly organized pores resembling sweat pores in human skin, but at super high densities (>1012 pores/cm2). These DBMs achieved exceptional water vapor transport rates, surpassing commercial breathable fabrics by up to 6.2 times, despite containing >2 orders of magnitude smaller pores (1 nm vs >700 nm). These DBMs effectively excluded model biological agents and harmful chemicals both in liquid and vapor phases, again in contrast with the commercial breathable fabrics. Remarkably, while hydrated biomimetic membranes were highly permeable to liquid water, they exhibited higher water resistances after dehydration at values >38 times that of commercial breathable fabrics. Molecular dynamics simulations support our hypothesis that dehydration induced protein hydrophobicity increases which enhanced DBM performance. DBMs hold promise for various applications, including membrane distillation, dehumidification, and protective barriers for atmospheric water harvesting materials