Electrorheological-fluid-based microvalves

Abstract

We present the successful design and fabrication of push-and-pull microvalves that use a giant electrorheological (GER) fluid. Our multilayer microvalves, including the GER fluid control channel, the electrode, the flow channel, and the flexible membrane, are fabricated with polydimethylsioxane-based materials by soft lithography techniques. The GER effect is able to provide high-pressure changes in GER control channel so as to fully close and open an associated flow channel. The fast response time of the GER fluid and the push-and-pull valve design adopted assure fast switching time of the valve less than 10ms and sound reliability. This GER-fluid-based microvalve has other advantages of easy fabrication and biocompatibility and is suitable for most microfluidic applications.

Structure evolution in electrorheological fluids flowing through microchannels

“…These unique features make ER fluids an ideal class of materials for use in a variety of hydraulic components, including valves 2,3 , clutches 4 and shock absorbers 5 . Recently, custom-formulated ER fluids have been employed in a number of microscale applications [6][7][8] and in various microfluidic devices [9][10][11][12] . With the recent discovery of nanoparticle-based ER fluids 13 , the expansion of applications to even smaller scale devices can also be envisioned.…”

Stimulus-active polymer actuators for next-generation microfluidic devices

“…However, for microvalve application the switching time is a crucial parameter, and here phasechange actuators and polymer hydrogels have-featuring values from a few seconds to a few minutes-a clear handicap. The smallest switching times in the millisecond range were achieved with a bistable membrane configuration (thermopneumatically actuated), a PDMS membrane [215] with carbon nanotube electrodes and electrostatic actuation, and with push-and-pull valves based on electrorheological fluids (cf. Table 1).…”

“…This transformation from liquid like to solid like is reversible and relatively fast, with response times in the order of 10 ms. In [215], the authors used an ERF (consisting of urea-coated barium titanyl oxalate nanoparticles in silicone oil) with giant electrorheological properties (yield stress of 200 kPa at an electric field of 5 kV/mm) to realize microfluidic push-andpull valves in multilayer PDMS structures by sandwiching a PDMS membrane between an ERF channel and a microfluidic channel. The same research group realized an ERF-driven cross-stream-active micromixer in a PDMSbased device [216,217], where the flow in the main channel is perturbed by the liquid flow in the orthogonal side channels.…”

Polydimethylsiloxane-based conducting composites and their applications in microfluidic chip fabrication

“…The microvalve was opened or closed by applying negative pressure ͑ϳ30 kPa͒ or positive pressure ͑ϳ10 kPa͒, respectively, to its pneumatic channels. Niu et al 37 introduced an electrodynamic and digitally addressable microvalve for millisecond-fast response time to control other fluid flows. The valve is actuated by smart giant electrorheological ͑GER͒ fluid, 38 which is a type of colloidal suspension exhibiting solidlike behaviors, such as the transmission of shear stress under an applied field of 1-2 kV/mm.…”