Virginia Tech demonstrates 3D-printed liquid metal (gallium-indium) composites that boost thermal conductivity 40x, enabling advanced heat dissipation in compute systems.
Virginia Tech graduate student Hugh Grennan has demonstrated a novel 3D-printed composite that combines liquid metal with silicone for enhanced thermal conductivity. In a presentation on the 3D Printing Nerd YouTube channel, Grennan showed the material conducting electricity, remaining functional even after being cut, and then successfully printing it as a heat-spreader — achieving thermal conductivity 40 times that of the base silicone.
The composite consists of eutectic gallium-indium (EGaIn), a metal alloy of approximately three parts gallium to one part indium that remains liquid at room temperature, suspended in uncured polydimethylsiloxane (PDMS) silicone. When mixed, the liquid metal breaks into separate droplets, each surrounded by a thin gallium oxide skin. After about an hour in an oven, the silicone cures to a solid while the metal droplets remain liquid inside, ranging from 10 to 100 microns in diameter. This structure provides the composite with soft elasticity, extreme toughness, and the capacity for autonomously self-healing electrical circuits.
The research comes from the Soft Materials and Structures Lab at VT MADE, Virginia Tech's New Center for Advanced Manufacturing. Grennan uses a syringe-fed 3D printer loaded with the composite. The printer's settings control the ratio between nozzle extrusion speed and print-bed movement, which stretches the droplets from round shapes into long, thin ones. This elongation is critical: it directs heat flow along the droplets' long axis, from a heat source to a heat sink.
A 2025 paper in Advanced Functional Materials, co-authored by associate professor Michael Bartlett who directs the lab, measured the printed composite's thermal conductivity along the droplet direction at 9.9 W/mK — approximately 40 times that of unfilled silicone. A separate 2024 paper in Additive Manufacturing highlighted the oxide skin's critical role in maintaining droplet shape and reconfiguration.
Grennan demonstrated the material's electrical properties by pressing a line into a cast slab with an indenter. The pressure forced droplets to merge into a conductive track that lit an LED. He then cut across the track with a razor blade and pressed again nearby; the LED relit faintly. The droplets begin insulated from one another by both the silicone matrix and their individual oxide skins. When conductive paths form through merged metal, a cut doesn't permanently break the path — the liquid metal flows around the damage.
Potential applications include custom heat sinks and stretchable wearable devices. Liquid metal is already used in some high-end hardware: Nvidia's GeForce RTX 5090 Founders Edition employs a gallium alloy in place of traditional thermal paste. The wearables market continues to expand, with IDC reporting 145.7 million unit shipments worldwide in the first quarter of 2026, up 4.3% year-over-year. The lab's recent research addresses stretchable liquid metal and polymer feedstocks for 3D-printed conductive parts, suggesting near-term applications in directed cooling for electric vehicles, robotics, and electronics, along with refined solutions for flexible wearable devices.