Nanoporous membrane fabrication by nanoimprint lithography for nanoparticle sieving.

An isoporous membrane with strictly controlled pore size, shape and distribution could provide an efficient, precise and mild sieving of particles in nanotechnology and biomedical applications. However there is a lack of highly porous polymeric membranes combining isoporosity and high permeance in the range below 500 nm. Track-etched membranes are practically the only commercial option. Membranes prepared by phase inversion typically have a broad pore size distribution. Most nanofabrication methods have limited the preparation of membranes with pores in the micrometer range. In this work, we present a nanotechnology-based fabrication methodology to manufacture a stable and flexible nanoporous polymeric membrane with 300 nm isopores using UV nanoimprint lithography. The highly porous membrane has a pore density of 4 × 109 pores per cm2 and stable permeance of 108 000 L m-2 h-1 bar-1. Uniform ZIF-8 nanoparticles were synthesized and the isoporous membrane successfully demonstrated as high as 100% rejection and size-based sieving performance of nanoparticles.

Nanofabrication of Isoporous Membranes for Cell Fractionation.

Cell fractionations and other biological separations frequently require several steps. They could be much more effectively done by filtration, if isoporous membranes would be available with high pore density, and sharp pore size distribution in the micro- and nanoscale. We propose a combination of two scalable methods, photolithography and dry reactive ion etching, to fabricate a series of polyester membranes with isopores of size 0.7 to 50 µm and high pore density with a demonstrated total area of 38.5 cm2. The membranes have pore sizes in the micro- and submicro-range, and pore density 10-fold higher than track-etched analogues, which are the only commercially available isoporous polymeric films. Permeances of 220,000 L m-2 h-1bar-1 were measured with pore size 787 nm. The method does not require organic solvents and can be applied to many homopolymeric materials. The pore reduction from 2 to 0.7 µm was obtained by adding a step of chemical vapor deposition. The isoporous system was successfully demonstrated for the organelle fractionation of Arabidopsis homogenates and could be potentially extended to other biological fractionations.