Development of Robust Self-assembled Microvalves for Robust Hydraulic Actuators

摘要

Compact robust hydraulic actuators are very important for space related applications because of their capability of producing much larger forces per unite volume/mass than existing technologies. The major components of these actuators are PZT stacks (pusher) and microvalves. The PZT pusher works at high frequencies to produce large flow rates (proportional to displacement traveled) and high pressures. As a component of the hydraulic actuator, the microvalves are challenged in matching the requirements of the PZT in terms of high operational frequencies, large flow rates and high-pressure support capabilities. In order to fulfill these requirements, the authors have developed robust self-assembled solid nickel micro valve arrays consisting of 80 single micro check valves, to achieve the required flow rate ( > 10 cc/second). A single micro check valve consists of an inlet channel (200 μm in diameter), a specially designed valve flap held by four identical micro beams, and outlet channels. All these structures are made from electroformed nickel and are self-assembled during a novel in situ UV-LIGA fabrication process. Finite element simulation results show that the micro check valve has a 1st resonant frequency of 16 kHz and is able to support pressures greater than 10 MPa. Test results show the flow rate is 19 cc/s at a pressure difference of 100 psi, and is roughly proportional to the pressure applied. Based on Poiseuille's law, it is reasonable to predict larger flow rates if higher-pressure differences are applied.