GaInSn

GaInSn, commonly referred to as Galinstan, is a eutectic alloy of gallium, indium, and tin. It is liquid at room temperature, with a melting point around −19 °C, which makes it a convenient mercury substitute in various applications. The alloy is valued for its low melting point, non-toxicity relative to mercury, and good thermal and electrical properties.

The typical composition is about 68.5% gallium, 21.5% indium, and 10% tin by weight, though variations exist for specific uses. At room temperature the material is a dense, silver‑gray liquid metal. It has a higher density than water (approximately 6.4 g/cm³) and notable thermal conductivity, which makes it useful for heat transfer and cooling tasks. The alloy is not volatile and possesses a very high boiling point, remaining liquid under ordinary operating conditions. A key characteristic is the spontaneous formation of a thin oxide layer on its surface (primarily gallium oxide), which can alter wetting behavior and protect the bulk metal from rapid oxidation.

Oxide formation also means GaInSn droplets can be partly non-wetting on certain surfaces, and wetting can be enhanced or inhibited by surface treatment or heating. This oxide skin is a factor in handling and in microfluidic or electronic applications where precise fluid control is required.

Applications span thermal management, liquid-metal circuits, flexible electronics, microfluidics, and soft robotics. It is used in thermal interface materials and reconfigurable antennas due to its conductivity and liquid form. Safety considerations emphasize that while Galinstan is less toxic than mercury, it contains heavy metals; ingestion should be avoided, and standard handling and disposal practices apply.