A latchable high-pressure thermohydraulic valve actuator

This work presents a latchable thermohydraulic microactuator for use in high-pressure valves, e.g. for oceanic sampling in missions of long duration. Mounted on a miniature submersible, it can be used in confined spaces to explore previously unreachable environments. However, the device can be used in any high-pressure application where long duration open and/or closed valve states are required, and power consumption is an issue. The actuator is fabricated using standard batch-processes as photochemical machining, wet etching and photolithography. The actuation and latching mechanisms are both thermohydraulic, using solid-to-liquid phase transition of paraffin for actuation and of a low melting point alloy for latching. Focus of this work is on the endurance of the actuator to facilitate a bistable valve. The actuator managed to keep a deflected position for almost 50 h at the load equivalent to 1.8 MPa applied pressure, after which the experiment was aborted. No pressure dependence was discovered in the latching losses, i.e. the difference in deflection before and after the actuator is powered off. Furthermore, the effect of intermixing of paraffin and the low melting point alloy was evaluated.