Graphene Coated Liquid Metal Droplet-Enabled Dual-Axis Integrated Accelerometer

This paper presents the design, optimization, fabrication, and characterization of a novel accelerometer consisting of a graphene-coated liquid metal proof mass integrated with laser-induced graphene (LIG) resistive sensing elements. The sensor utilizes the unique electromechanical properties of eutectic gallium-indium (EGaIn) liquid metal by confining an EGaIn droplet within a graphene-patterned 3D pyramid cavity. The pyramid base structure imposes a restoring force on the droplet enabling continuous and simultaneous sensing in two directions using a single proof mass. Coating EGaIn droplet with graphene forms an interpenetrated protective shell around the droplet, enhancing its mobility and mechanical robustness. Design optimization of the sensing microelectrodes is performed to improve the sensor performance. The accelerometer performance is evaluated and characterized, demonstrating a sensitivity of ≈9.5 kΩ g−1 (978 Ω m−1 s2) and a cross-axis sensitivity of ≈3 % with excellent repeatability (over 120 000 cycles). The sensor is fabricated using a scalable laser writing technique and integrated with a programmable system on a chip (PSoC) to function as a stand-alone system for real-time wireless motion monitoring and virtual game control. The developed Graphene/Liquid metal droplet-based sensor is promising for applications of inertial sensors, inertial switches, and soft liquid metal robots with attractive electromechanical properties.