A Liquid Metal Balloon for the Exfoliation of an Ultrathin and Uniform Gallium Oxide Layer.

We report the exfoliation of ultrathin gallium oxide (GaO) films from liquid metal balloons, formed by injecting air into droplets of eutectic gallium-indium alloy (eGaIn). These GaO films enable the selective adsorption of carbon nanotubes (CNTs) dispersed in water, resulting in the formation of a dense, percolating CNT network on their surface. The self-assembled CNT network on GaO provides a versatile platform for device fabrication. As an example application, we fabricated a chemiresistive gas sensor for detecting simulants of chemical warfare agents (CWAs), including diisopropyl methylphosphonate (DIMP), dimethyl methylphosphonate (DMMP), and triethyl phosphate (TEP). The sensor exhibited reversible responses, high sensitivity, and low limits of detection (13 ppb for DIMP, 28 ppb for DMMP, and 53 ppb for TEP). These findings highlight the potential of GaO films derived from liquid metal balloons for integrating CNTs into functional electronic devices.