Water-powered, osmotic microactuator

Abstract

This paper presents a microactuator that draws power directly from water and produces mechanical actuation without any electrical energy consumption. The microactuator is made of cellulose acetate with cylindrical cavity of 0.5 to 1.5 mm in diameter and 0.4 to 1 mm in depth. These cavities are filled with sodium chloride and a polyvinylidene chloride copolymer diaphragm is spun on as the cover. Using osmosis for the first time on the microscale, this water-powered, osmotic actuator can provide both high pressure (up to 35.6 MPa) and large actuating displacement (up to 0.8 mm as measured with an actuator of 0.8 mm in diameter). Incompressible water flow controlled by membrane characteristics and chemical potential enables the direct energy conversion to provide mechanical actuation. Measurement results show that constant volume change of 4/spl sim/15 nl/hr can be achieved depending on the design. When integrated with other microfluidic devices, this osmotic microactuator can serve as a clean, compact and inexpensive fluid power source.