Durability and Recoverability of Soft Lithographically Patterned Hydrogel Molds for the Formation of Phase Separation Membranes

Abstract

Hydrogel-facilitated phase separation (HFPS) has recently been applied to make microstructured porous membranes by modified phase separation processes. In HFPS, a soft lithographically patterned hydrogel mold is used as a water content source that initiates the phase separation process in membrane fabrication. However, after each membrane casting, the hydrogel content changes due to the diffusion of organic solvent into the hydrogel from the original membrane solution. The absorption of solvent into the hydrogel mold limits the continuous use of the mold in repeated membrane casts. In this study, we investigated a simple treatment process for hydrogel mold recovery, consisting of warm and cold treatment steps to provide solvent extraction without changing the hydrogel mold integrity. The best recovery result was 96%, which was obtained by placing the hydrogel in a warm water bath (50 °C) for 10 min followed by immersing in a cold bath (23 °C) for 4 min and finally 4 min drying in air. This recovery was attributed to nearly complete solvent extraction without any deformation of the hydrogel structure. The reusability of hydrogel can assist in the development of a continuous membrane fabrication process using HFPS.

Micropatterned Thin-Film Composite Poly(piperazine-amide) Nanofiltration Membranes for Wastewater Treatment

“…The most common method to synthesize this dense layer, typically made of polyamide, is an interfacial polymerization (IP) reaction in which two highly reactive monomers, such as amine and acid chloride, react at the interface of two immiscible solutions. , The IP reaction occurs at the top surface of a porous membrane to fabricate the TFC membrane. Since the invention of TFC membranes, one of the hoped for goals of researchers has always been enhancing both permeation flux (how fast water transports through a membrane) and rejection (the ability of a membrane to separate solutes) using cost-efficient and scalable methods. , Significant efforts have been made to enhance the TFC membrane performance, including optimizing the parameters of the IP reaction, coating the membrane surface with hydrophilic layers, − applying post-treatment steps using organic solvents, , and incorporating nanoparticles within the polyamide layer. − Most of the proposed methods either added extra complexity steps that reduced the affordability and scalability of such membranes or lowered the permeation flux, making them less applicable for industrial applications. , In addition, some of these modification methods used expensive nanoparticles or environmentally unfriendly chemicals …”