A Passive Microfluidic Valve using Superhydrophobic/Hydrophilic Nanostructures for Lab-on-A-Chip (LOC) Systems

This paper describes a passive microfluidic valve, which has an integrated superhydrophobic surface in one of the channels to selectively inhibit the flow of water based reagents and pass aqueous solutions containing surfactants. The microchannels were fabricated by standard photolithography and wet etching techniques. The superhydrophobic polymer patch was fabricated using the layer-by-layer (LBL) deposition technique, in which multiple layers of polyelectrolytes were coated on a channel wall followed by silica nanoparticle treatment. The channels were sealed with a polydimethylsiloxane (PDMS) slab by treating under oxygen plasma. The fabricated microfluidic valve was tested with liquids flowing in the microchannels under capillary action. It is shown that the valve selectively regulates the flow of test samples. The water sample stops at the front of superhydrophobic patch and the 2-isopropanol flows through the channels without any resistance.