Observation of Liquid Metal Actuation in Microfluidic Channels and Implementation to Tunable RF Inductors

The overreaching goal of this thesis research is to analyze liquid metal plug actuation in microfluidic channels and to exemplify this actuation in a tunable inductor design using liquid metal as a switching material, and to demonstrate the feasibility of liquid metal in other devices.

A gallium and indium based alloy, EGaIn, which is liquid at room temperature is the liquid metal type chosen for this research. Although it owns some advantages such as high vapor pressure, non-toxicity and good conductivity, there are some crucial factors that we should pay attention to move the liquid metal in microchannels as a result of oxidation with contact to air and stickiness of oxidized skin to any surface. One of them is to determine the right coating material for coating the channel and the best surfactant to carry the liquid metal plug without leaving residues with sufficient amount of pressure.

So far, liquid metals have been used in some RF applications, but EGaIn could not be implemented properly in a microfluidic channel as a separate liquid metal plug because of the oxidation issue. Our aim is here to verify that there are ways to handle the actuation of based liquid metals in microchannels. In this thesis, we have used EGaIn in the experiments conducted, but the acquired results are also applicable to galinstan, which is another gallium based alloy.

Right after the liquid metal actuation is exhibited in microfluidic channels, this actuation is exemplified in tunable loop and spiral inductors on both PCB and glass slides using lithography technique. A closed loop channel with peristaltic pumping valves has been designed with the help of LabVIEWTM and proper channel designing technique. Therefore, moving the liquid metal in a desired way with an expected speed is achieved.

At the end of the study, tunability in an RF inductor using liquid metal as a switching part is provided, once a solution to the nagging oxidation problem of liquid metals is offered, and thus the feasibility of liquid metals to the electrical device applications is demonstrated.