Liquid Metal Based Test Structures and Reconfigurable Microfluidic Microwave Devices and Antennas

Abstract

Electrically reconfiguring communicational devices suffer from a number of drawbacks: incorporating electrical elements such as varactors in unit cell level to manipulate the inductance/capacitance of the circuits and maintaining RF/DC interference isolation in power supply is very challenging. In this thesis, a mechanical tuning approach for communicational devices is proposed with stretching or curving these devices. Devices are fabricated based on the gecko-fluidic reversible bonding technique with EGaIn liquid metal (LM) as their conductor and a new thermoplastic substrate (SEBS) with a versatile and cost effective manufacturing method. Selective filling of complex micro-fluidic features is realized with the use of hydrophobic valves which are optimized based on the measured critical pressure of oxidized EGaIn for filling SEBS channels. Laplace barriers are used to achieve “auto-filling” of extremely low aspect ratio channels of LM in SEBS substrate. Furthermore, a technique for making multiple discrete units of LM features from a monolithic injected LM pattern. As a proof of concept, mechanically reconfigurable antennas such as a half-wavelength folded dipole, a multilayer dipole with a soft via, and a micro-strip patch are fabricated and measured for tuning in their center frequency. A super stretchable beam reconfigurable FSS is also manufactured which shifts its beam direction by stretching or curving.