Osmotically Actuated Micropumps and Control Valves for Point-of-Care Applications

We present novel micropumps and valves actuated by osmotic flow for point-of-care (POC) applications. Although there has been significant progress in the development of microfluidic flowcontrol components, such as fluidic switches, diodes, and resonators, the flow needs to be ultimately supplied by bulky off-chip active components. These off-chip components cannot be easily miniaturized integrated micropumps that utilize electrostatic, piezoelectric, or electroosmotic actuation require high operational voltages, limiting their applications. Other novel approaches, such as magnetic actuation and liquid metal pumping, are also limited by their nonstandard processes and biocompatibility. In this paper, we report two active components, control valves and fluid pumps, actuated by osmotic mechanism, allowing completely stand-alone integrated microfluidic systems. To the best of our knowledge, this is the first attempt to realize control valves by osmosis. The valve can maintain robust sealing up to 125 kPa of back pressure. The fabricated osmotic pump is capable of pumping at >30 \mu L/min, which is higher than that of previous works by an order of magnitude. To demonstrate the feasibility of manipulating biofluids, white blood cells suspended in serum were driven and filtered by osmotic actuation. The experimental results verified the potential use of osmotic actuation for POC disposable microfluidics.