Shape-selective filtration of nanomaterials and proteins using lamellar block copolymer-based slit membranes

The growing need for highly efficient water purification and bioseparations necessitates innovations in block copolymer (BCP) based ultra-filtration membranes. Most of the work in BCP membranes has focused on using cylindrical pores. However, biological ultrafiltration membranes can have complex architectures which can perform complex separations. In this work, we demonstrate novel slit-based membranes using lamellar block copolymers by taking insights from biological membranes. The vertically oriented BCPs are converted to slit membranes using a wet etching process. These slit-shaped membranes demonstrate sharp cut-offs for solute filtration. Furthermore, we demonstrate the first example of enhanced separation of 1-D nanomaterials (nanorods) as compared to the 0-D nanomaterials (nanoparticles) using these slit-based membranes, which is facilitated by the shape similarity of 1-D nanomaterials with the nano-slits. Additionally, we show that these slit-shaped membranes show 100 % permeability of similar-sized Lysozyme and Bovine Serum Albumin (BSA) proteins while retaining the Immunoglobulin G (IgG) antibodies up to 70 %, thus making them highly useful for bioseparations. The enhanced permeation of the BSA and Lysozyme is governed by their relative one-dimensional shapes as opposed to the Y-like shape of the IgG proteins. We believe that these slit-shaped membranes will be useful for shape-selective filtrations across a spectrum of applications.