There is tremendous interest in leveraging the unique properties of gallium liquid metal alloys (GaLMAs) to develop flexible, stretchable, conformal and reconfigurable RF electronic devices.  These properties are difficult or impossible to achieve using traditional dynamic tuning platforms such as microelectromechanical switching (MEMS) or electronic switching (solid state components).   Use of tunable antennae and/or structurally integrated stretchable electronic components to support or replace traditional electronic materials offers critical advantages including: ultra-broadband response, dynamically tuned RF functional window, multi-level switching, directional steerability, and on-demand reconfiguration.                 The work presented here details efforts to manipulate the surface chemistry of gallium liquid metal alloys (GaLMAs) with the purpose of controlling flow to alter the electrical and electromagnetic response of various RF microfluidic electronic devices.  Under ambient conditions, the surface of a GaLMA spontaneously develops a thin layer of Ga2O3 that imparts structural stability to deposited metal droplets and increases the stickiness of the alloy to surfaces.  This property is potentially useful for self-healing applications where passivating surface oxidation of the alloy can prevent significant material leakage from a damaged circuit and enable quick reconnection; however, challenges arise for reconfigurable electronics applications where metal oxide residue can interfere with actuation between multiple circuit elements.  Previous work by Dickey and coworkers (North Carolina State University) demonstrates that surface oxides of liquid metals are reduced in the presence of HCl, either in vapor form or after diffusion through a PDMS membrane.  Reduction of the oxide layer results in alloy dewetting and a fully liquid droplet forming.  This work demonstrates the exquisite control obtained by using proton exchange membranes as the interfacing layer with the GaLMA materials that greatly reduce the need for the direct presence of caustic (HCl) materials.  We show how various film treatments influence the wettability of deposited GaLMA, with potential implications for channel filling/evacuation within proposed RF electronic devices.

Flexible, stretchable, and reconfigurable RF electronic devices enabled by control of gallium liquid metal alloy surface chemistry

248th National Meeting (2014)

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