A hybrid of microreplication and mask-less photolithography for creating dual porosity and textured surface membranes

Microporous membranes have a number of applications in microfluidic devices including biotechnology and displays (Hagedon et al 2012 Nature Commun. 3 1173, De Jong et al 2006 Lab Chip 6 1125–39). Though commercially available micro-porous membranes are widely available using the ion track-etch method, there are few economical techniques to make mechanically robust membranes with dual pore sizes and/or surface texture. We demonstrate fabrication of high strength polyamide (poly(p-phenylene-2,6-benzobisoxazole)) membranes using a hybrid microreplication and mask-less photolithographic method. The fabricated films are only ∼6–10 µm thick, yet adequately strong to be released and handled with diagonals of at least several inches. The films contain dual pore sizes (32 µm, 6 µm) with the smaller pores achieving 1:1 aspect ratio, and the films include a highly-engineered surface texture. These films are demonstrated in application for electronic-paper displays, and exhibit robust optical switching and diffuse (paper-like) reflectance. (technical note)