Experimental results from six prototype devices demonstrate that pressure changes induced in a liquid bridge via electrowetting can generate large deflections (20–75 µm) of an elastomeric membrane similar to those used in lab-on-a-chip microfluidic devices. In all cases deflections are obtained with a low voltage (20 V) and very small power consumption (<1 µW). The effects of variations in the bridge size and membrane dimensions on measured displacements are examined. Theoretical predictions are in good agreement with the measured displacements in those cases where the liquid contact angles could be measured within the devices during electrowetting. Contact angle hysteresis and charge injection into the dielectric layers limited the repeatability of deflection behavior during repeated cycling. Approaches for achieving greater deflections and improved repeatability are discussed.
Elastomeric materials offer many benefits to MEMS (Micro Electro Mechanical Systems).These benefits include smaller device footprints, greater range of motion, and lower required actuation forces. However, a complementary actuation technology is needed, to implement the capabilities of elastomeric components. Capillary forces are a novel and promising mechanism to produce motion in the flexible components of micro devices -such as elastomeric
Conventional approaches to microscale actuation, such as electrostatic, have difficulty in achieving large motion at moderate voltages. Recently, actuators relying on the active control of capillary pressure have been demonstrated, with the pressure change caused by electrowetting on a pair of opposing surfaces. In this work, experimental results are presented from five prototype devices in which only a single active surface is used. The results demonstrate that pressure changes induced in a liquid bridge in this manner can produce large deflections (15 μm) of a flexible membrane. Voltages employed in the tests were moderate (≤25 V). The influence of several design variables, such as membrane diameter and thickness, on the membrane deflection are examined. Theoretical predictions are also presented and generally follow the experimental values. Potential sources for the discrepancies between theory and experimental results are discussed. While deflections obtained using a single active surface are not as large as those obtained with two active surfaces, single-active-surface configurations offer a simple route to achieving adequate deflections for lab-on-a-chip microsystems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.