Electrowetting Ionic Liquid Flow Controller

Abstract

Ionic liquids are used in a variety of chemical, microfluidic, aerospace, and other diverse applications. Microfluidic applications often require a small footprint and manage small volumes of fluid in their channels on the order of microliters or less. Many microfluidic devices utilize external pressure systems or mechanical pumping mechanisms to control the flow of fluids through the device, inherently limiting the footprint of the device. Open microchannel microfluidics have at least one fluid boundary open to the environment instead of a channel wall surface confining liquid completely. A promising micro-scale fluid system for spacecraft propulsion applications is the electrospray thruster. Electrospray thrusters utilizes ionic liquids for propellant whereby ions are accelerated via electric field for thrust. These propulsion systems currently have few suitably sized active propellant management options, leaving the overall system less robust than desired. For use as a micro-scale ionic liquid propellant management device in these small electrospray spacecraft propulsion systems, a solid-state flow controller is proposed. By including an electrowetting region within an open microchannel fluid path, a change in liquid pressure can be achieved via electrowetting effect so long as contact angle is free to change within the electrowetting channel region. Various open microchannels are fabricated in silicon and tested, showing that rounding of the open microchannel ledges prevents liquid pinning along the channel, allowing for contact angle changes via electrowetting to manifest a change in pressure within the liquid in the channel, demonstrating a solid-state ionic liquid flow controller for use in electrospray propulsion systems. [2023-0191]