Multilayer Carbon Nanotube/Gold Nanoparticle Composites on Gallium-Based Liquid Metals for Electrochemical Biosensing

Gallium-based liquid metals have emerged as an important class of materials for bioelectronic and biosensor devices due to their low mechanical properties and fluidic behavior. However, liquid metals are susceptible to oxidation and corrosion, causing instability and limited electrochemical properties under physiological environments. The limited biostability and electrochemical properties hinder the use of liquid metals for potential biosensing applications. Here we developed a nanomaterial electrochemical deposition method to prevent the oxidation process, improve the biostability, and enhance the electrochemical properties of liquid metals in the physiological buffer. A carbon nanotube composite was designed to be deposited by a cathodic reaction on a gallium surface to prevent oxidation during the deposition. Then gold nanoparticles were functionalized onto the carbon nanocomposite to enhance the electrochemical properties further. The nanocomposite multilayer on the liquid metals provided excellent biostability and substrate adhesion confirmed by a long-term aging test in physiological buffer and repeated bending. We conducted dopamine sensing to confirm the enhanced electrochemical performance of the nanocomposite multilayer on the liquid metal. The liquid metal-based biosensor demonstrated a sensitivity of 0.236 ± 0.013 μA/μM and LOD of 23.2 nM that are competitive with current electrochemical tools used for in vivo dopamine sensing. Also, the nanocomposite structure displayed good dopamine detection selectivity under a plethora of metabolic byproducts. Lastly, a fast-scan cyclic voltammetry (FSCV) test was performed to demonstrate the fast responsiveness and high sensitivity of this liquid metal biosensing platform. Overall, this study systematically evaluated the electrochemical deposition conditions of nanomaterials on gallium alloys. This study also developed a method to enable a biostable and high-performance electrochemical sensing capability of liquid metals and opens up opportunities for potential biosensing applications of liquid metal devices in the future.