Vapor-based synthesis of ultrathin hydrogel coatings for thermo-responsive nanovalves

Abstract

We report vapor-based, single-step synthesis of hydrogel coatings and the fabrication of thermo-responsive nanovalves with fine flow regulation. The hydrogel films exhibited swelling ratios as high as 15.4 at room temperature. The swelling ratio dramatically decreased with the increase of the temperature. The increase of the crosslinking degree in the hydrogel reduced the swelling ratio of the coatings and broadened the transition temperature region. Thermo-responsive nanovalves were fabricated by depositing ultrathin hydrogel coatings inside nanoporous track-etched polycarbonate membranes. Electron microscopy observations revealed hydrogel coatings along the sidewalls of the nanopores with controllable thicknesses in the sub-50 nm range. The “closed” and “open” states of the nanopores for the flow of bovine serum albumin were achieved by varying the temperature. Fine regulation of the protein flow was also demonstrated in nanopores with different hydrogel coating thicknesses. The hydrogel coatings were estimated to have smaller temperature-induced swelling change in the nanopores compared with the same coatings on planar surfaces.