Micro valves using nanoparticle-based giant electrorheological fluid

The paper presents novel micro valves, using giant electrorheological (GER) fluid, for micro flow control. This GER fluid, consisting of urea-coated 20 nm-diameter nanoparticles (barium titanyl oxalate) suspended in silicone oil, can reach a yield stress of 130 kPa, breaking the theoretical upper bound of conventional ER fluids. A PDMS-based chip was used to assure good bonding and zero dead volume of the valve in controlling the other flows. The differential pressure along the 2-way GER valve (GER channel) was systematically measured by adjusting different parameters; it is much higher than that of the present ER valves. These valves can be integrated with other microfluidic components for different applications, such as micromixing, micro-pumping and so on.