Reconfigurable and Flexible Liquid-Metal Devices and Circuits

Abstract

Liquid-metal reconfigurable and flexible electronics attempt to address design constraints on materials, space, cost, and power. The work presented in this dissertation utilizes the unique properties of gallium-based liquid metals towards reconfigurable electronics and flexible electronics. The first part of this work discusses a novel approach to achieve versatile reconfigurable electronics using liquid-metal elements. Typically, reconfigurable electronics are realized using various kinds of switching elements such as MEMS switches, PIN diodes, varactors, and filter banks; these have limited versatility and scalability. These limitations are addressed by using LM in microfluidic channels to shape the structures of RF devices, such as antennas and transmission lines. Reconfigurable 1D, 2D, and 3D arrays of electrically conductive elements were implemented to demonstrate reconfigurable dipole and patch antennas that can change: radiation patterns, creating 87 patterns by altering the shape of a single antenna; polarization angle by exchanging the radiating edge and half-wavelength edge in a patch antenna; and maximum gain from 0 to 2 dBi at different angles of a dipole-antenna radiation pattern. Such antennas are useful in mitigating channel interference in a communication system with multiple transmitters and receivers. The second part of this dissertation discusses liquid-metal patterning using 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. Low-cost fabrication techniques were developed to pattern printed and sprayed LM on polymeric substrates obtaining high-resolution 35-µm features with 25-µm spacing. 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.