PDMS thin-film composite membrane fabricated by ultraviolet crosslinking acryloyloxy-terminated monomers

Design Rules for Capillary Force-Induced Clustering and Recovery of Monolithic Microbridges on Microapertured Polymer Membrane

Microbridge structures have been widely used in microelectromechanical systems. When the devices with microbridges operate in diverse environments, including wet conditions, structural failures such as crumples, clustering, and collapse of micro/nanostructures occur due to the capillary force of liquid in this environment. It is necessary to establish comprehensive design criteria to address this. Herein, we investigate the structural stability of microbridges on microsized apertures in wet conditions. The multiscale structure is fabricated with microbridge width, spacing of 10 μm, and height of 6 μm while varying the supporting micro aperture size. The behavior of the microbridges is observed through an optical microscope during water dispensing on the bridges and evaporation. It is found that the microbridges remain stable on apertures of 100 μm in diameter, while clustering occurs on larger-sized apertures (300, 500 μm). Interestingly, in contrast to the 500 μm-sized aperture, the clustered microbridges on the 300 μm-sized aperture gradually recover to their original configuration after completely evaporating water. A simple theoretical model for capillary force-induced clustering and recovery is proposed to elucidate this phenomenon, which agrees with the experimental results. The microbridges constructed following the design rule can ensure robust and stable operation even in wet conditions. These findings contribute to advancing micro/nanoscale engineering and offer insights for developing innovative microdevices.

Carbon Capture Membranes Based on Amorphous Polyether Nanofilms Enabled by Thickness Confinement and Interfacial Engineering

Thin-film composite membranes are a leading technology for post-combustion carbon capture, and the key challenge is to fabricate defect-free selective nanofilms as thin as possible (100 nm or below) with superior CO₂/N₂ separation performance. Herein, we developed high-performance membranes based on an unusual choice of semi-crystalline blends of amorphous poly(ethylene oxide) (aPEO) and 18-crown-6 (C6) using two nanoengineering strategies. First, the crystallinity of the nanofilms decreases with decreasing thickness and completely disappears at 500 nm or below because of the thickness confinement. Second, polydimethylsiloxane is chosen as the gutter layer between the porous support and selective layer, and its surface is modified with bio-adhesive polydopamine (<10 nm) with an affinity toward aPEO, enabling the formation of the thin, defect-free, amorphous aPEO/C6 layer. For example, a 110 nm film containing 40 mass % C6 in aPEO exhibits CO₂ permeability of 900 Barrer (much higher than a thick film with 420 Barrer), rendering a membrane with a CO₂ permeance of 2200 GPU and CO₂/N₂ selectivity of 27 at 35 °C, surpassing Robeson's upper bound. This work shows that engineering at the nanoscale plays an important role in designing high-performance membranes for practical separations.

Porous Structural Microfluidic Device for Biomedical Diagnosis: A Review

Microfluidics has recently received more and more attention in applications such as biomedical, chemical and medicine. With the development of microelectronics technology as well as material science in recent years, microfluidic devices have made great progress. Porous structures as a discontinuous medium in which the special flow phenomena of fluids lead to their potential and special applications in microfluidics offer a unique way to develop completely new microfluidic chips. In this article, we firstly introduce the fabrication methods for porous structures of different materials. Then, the physical effects of microfluid flow in porous media and their related physical models are discussed. Finally, the state-of-the-art porous microfluidic chips and their applications in biomedicine are summarized, and we present the current problems and future directions in this field.