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University of Hawaii

Electrical Engineering

Reconfigurable and Flexible Liquid-Metal Devices and Circuits

Date: 2020-03-03           Add to Google Calendar
Time: 3:00pm - 6:00pm
Location: Holmes Hall 389
Speaker: Kareem Elassy, PhD Candidate in EE, Advisor Dr Ohta

Abstract

Liquid-metal reconfigurable and flexible electronics attempt to address design constraints on materials, space, cost, and power. The work presented in this dissertation is divided into two parts to utilize the unique properties of gallium-based liquid metal towards reconfigurable electronics and flexible electronics. The first part of this work discusses a novel approach to achieve fully versatile reconfigurable electronics using liquid-metal elements. Typically, reconfigurable electronics are realized using various kinds of switching elements as MEMS, PIN diodes, varactors, and filter banks; which have limited versatility and scalability. These limitations are addressed through continuously shaping liquid metal in microfluidic circuits to shape the devices structures, plus altering the interconnects between the devices. Different modes of reconfigurable 1D, 2D, and 3D arrays of electrically conductive elements were implemented to demonstrate reconfigurable dipole and patch antennas that change radiation pattern, polarization, and gain. Such antennas exhibited a significant improvement to mitigate the channel interference in a communication system with multiple transmitters and receivers. The second part of this dissertation discusses liquid-metal patterning using all-low-cost high-resolution techniques for flexible electronics. Usually flexible electronics are fabricated using nanoparticle or polymeric conductive inks. Conductive nano inks suffer from cracks after cyclic deformation, while polymeric inks have low conductivity. Gallium-based liquid-metal alloy is a promising alternative that addresses these issues. Liquid metal spontaneously forms self-passivated oxide film when exposed to ambient atmosphere. This film performs as a mechanical support for the underlying continuous conductive core enriching liquid metal with self-healing properties throughout dynamic deformations. All-low-cost fabrication techniques were developed to pattern liquid-metal high-resolution features by printing and spraying on polymeric substrates. The usefulness of these fabricating methods was demonstrated by realizing graphene transistors, RFID, patch antennas, and transmission lines. Many more possibilities for liquid-metal applications are still unrealized.



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