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DEPARTMENT OF ELECTRICAL ENGINEERING
PHD DISSERTATION DEFENSE
Electrokinetic Actuation of Liquid Metal for
Reconfigurable Radio Frequency Devices
Speaker:
Date:
Time:
Location:
Ryan Gough
Thursday, March 3, 2016
11am – 1pm
Holmes Hall 389
Abstract
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.