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University of Hawaii

Electrical Engineering

Electrokinetic Actuation of Liquid Metal for Reconfigurable Radio Frequency Devices

Date: 2016-03-03           Add to Google Calendar
Time: 11am – 1pm
Location: Holmes Hall 389
Speaker: Ryan Gough, candidate for PhD, advisor: Dr. Wayne Shiroma

Liquid metals are an attractive material choice for designers wishing to combine the advantages of metals, such as high electrical conductivity, thermal conductivity, and reflectivity, with the inherently dynamic nature of fluids. Liquid metals have drawn special interest from microwave and radio frequency (RF) design engineers seeking to create tunable devices with linear, high-quality-factor responses. This interest has only increased with the recent introduction of non-toxic, gallium-based alternatives to mercury on the commercial market. Early experiments with liquid metal as an RF tuning element have yielded promising results, but have largely depended on externally applied pressure for actuation, necessitating the use of clunky and inefficient micro-pumps. This research demonstrates that by leveraging the naturally high surface tension of liquid metals, as well as the unique electrochemistry of gallium-based alloys, a tremendous amount of control can be exerted over both the metal’s shape and position via low-voltage, low-power electrical signals. The actuation techniques developed as part of this research are immediately reversible, repeatable, and do not require the constant application of actuation signals in order to maintain an actuated state. Furthermore, the power and voltage requirements for these techniques are better than an order of magnitude below those needed for conventional micro-pumps. The 'self-actuation' of gallium alloys will also be demonstrated, in which the liquid metal is capable of supplying its own kinetic energy via the direct transfer of stored electrochemical energy within its native oxide layer, resulting in dramatic, controlled changes to its shape and position with no external power supply required. Each of these techniques will be discussed and demonstrated in turn, along with several examples of how they can be used to leverage the unique properties of liquid metal towards the creation of reconfigurable RF devices.