An Electrohydrodynamic Injection Pump - A Novel Actuator for Microsystem Technology

A silicon micromachined electrohydrodynamic (EHD) injection pump for microsystem technology is presented. The pump consists of two opposed grids, which are micromachined from single crystal silicon and bonded together anodically. Pumping and static pressure generation was achieved with different polar fluids such as ethanole, propanole or acetone but most organic solvents can be pumped. With ethanole a maximum static pressure of 2.5 kPa (32 cm pumping head) and a pumping rate of 14 ml/min at a pressure of 420 Pa were achieved. For the realized pump tne grid area measures 3 mm × 3 mm and the grid distance 350 μm. Pumping started at d.c. voltages as low as 40 V, wheras 700 V were needed for maximum throughput. Pumping was also observed with a.c. driving voltage. To increase pressure several of the devices can be stacked. This opens up new applications like micromachined cooling systems or microhydraulic actuators. The maximum flow rate and pressure head can be varied in a wide range by adjusting the dimensions of the pump. By further reducing the grid distance driving voltages below 100 V are expected.