Design and fabrication of in situ UV-LIGA assembled robust nickel micro check valves for compact hydraulic actuators

Abstract

Compact robust hydraulic actuators (pumps) are very important for space-related applications because of their capabilities in producing much larger forces per unit volume/mass than existing technologies. PZT stacks (pusher) have been widely identified for developing compact actuators (pump), but valves to match the inherent properties of PZT, in terms of high frequency (up to 100 kHz), load support (up to 100 MPa) and desired flow rate, are missing. The authors have developed novel robust solid nickel microvalve arrays using an in situ UV-LIGA assembling process. A high frequency and large pressure support capability has been realized analytically by elaborating the scaling law, in combination with a stiff material such as nickel. Large flow rate was realized by utilizing a microvalve array, instead of using a single valve. By doing this, all major requirements, in terms of frequency match, load support, as well as small amount of valve mass (payload), have been met. The reliability of the valve is assured by using a curved valve flap so that low stress can be maintained, in combination with a mechanical robust nickel valve stopper.