Abstract

Controlled Loading and Release of on-chip Stored Liquid Agents Through Surface Modified Metal Membrane

Tao Zhang, Scientist, Singapore Institute Of Manufacturing Technology

Liquid sample loading and releasing is one bottleneck problem in microfluidic device fabrication and applications since current methods such as blisters are suffering from large liquid volume, sample residue contamination, manually release, and so on. In this research, UV controlled releasing of liquid was demonstrated for the first time on nickel membrane modified with silica/polymer hybrid layer. The penetration of water droplet through membrane was controlled by the wettability change of grafted UV responsive molecules on the nanoporous silica/polymer layer. The method involved layer-by-layer coating of 15 nm silica nanoparticles and positively charged PAH polymers on oxygen plasma pretreated nickel membrane with 2 um pore size. After formation of nanoporous silica/PAH layer on nickel membrane, azobenzene based UV responsive molecules were chemically grafted on the top layer of silica, which can switch between hydrophobic and hydrophilic by molecular conformation transformation. The membrane surface can switch reversibly between hydrophobic state, the water contact angle is 170 degrees, and superhydrophilic state after 365 nm UV and 404 nm visible light illumination. At hydrophilic state, water droplet can flow through the nickel membrane due to capillary effect. The UV responsive nickel membrane provides a cost-effective and fast approach for on-chip liquid reagent controlled loading and release in microfluidic devices.