A Virginia Tech lab has demonstrated a 3D-printed composite that uses liquid metal droplets to steer heat through soft silicone. Graduate student Hugh Grennan mixed eutectic gallium-indium into uncured PDMS, then printed the material from a syringe-fed printer. The droplets, roughly 10 to 100 microns across, keep their liquid state after the silicone is cured in an oven. According to a 2025 paper in Advanced Functional Materials, the printed composite reaches a thermal conductivity of 9.9 W/mK along the droplet direction, about 40 times that of unfilled silicone.
The key is stretching the droplets during printing. By controlling the ratio of extrusion speed to bed movement, the lab turns round droplets into long, thin ones, allowing heat to travel along their length from a heat source to a heat sink. The same material can also carry electricity: pressing a line into a cast slab forces droplets to merge into a conductive track, and cutting that track does not permanently break it, since the liquid metal can flow and reform pathways. A 2024 paper in Additive Manufacturing credits the gallium oxide skin around each droplet for this reconfiguration behavior.
The lab points to custom heat sinks, stretchable wearables, and directed cooling for electric vehicles, robots, and electronics as likely uses. The Tom's Hardware report notes that liquid metal is already used in some PC hardware, such as Nvidia's RTX 5090 Founders Edition, but the Virginia Tech work extends the idea to printed, flexible structures. Since only one source was used, there are no conflicting accounts to compare.