A group of scientists made a working liquid metal robot

From NewScientist:

A miniature, shape-shifting robot can liquefy itself and reform, allowing it to complete tasks in hard-to-access places and even escape cages. It could eventually be used as a hands-free soldering machine or a tool for extracting swallowed toxic items.

Robots that are soft and malleable enough to work in narrow, delicate spaces like those in the human body already exist, but they can't make themselves sturdier and stronger when under pressure or when they must carry something heavier than themselves. Carmel Majidi at Carnegie Mellon University in Pennsylvania and his colleagues created a robot that can not only shape-shift but also become stronger or weaker by alternating between being a liquid and a solid.

The robot itself is made from a mixture of magnetic materials including neodymium, iron, and boron, and the liquid metal gallium. It "melts" when placed near a magnet, though I'm not entirely sure how it re-forms itself after that. So it's not quite a T-1000 yet. But it's getting there.

Here's a little more from the source paper, "Magnetoactive liquid-solid phase transitional matter," published in the journal Matter:

Magnetically actuated miniature machines can perform multimodal locomotion and programmable deformations. However, they are either solid magnetic elastomers with limited morphological adaptability or liquid material systems with low mechanical strength. Here, we report magnetoactive phase transitional matter (MPTM) composed of magnetic neodymium-iron-boron microparticles embedded in liquid metal. MPTMs can reversibly switch between solid and liquid phase by heating with alternating magnetic field or through ambient cooling. In this way, they uniquely combine high mechanical strength (strength, 21.2 MPa; stiffness, 1.98 GPa), high load capacity (able to bear 30 kg), and fast locomotion speed (>1.5 m/s) in the solid phase with excellent morphological adaptability (elongation, splitting, and merging) in the liquid phase. We demonstrate the unique capabilities of MPTMs by showing their dynamic shape reconfigurability by realizing smart soldering machines and universal screws for smart assembly and machines for foreign body removal and drug delivery in a model stomach.

Metal robot can melt its way out of tight spaces to escape [Karmela Padavic-Callaghan / NewScientist]

Magnetoactive liquid-solid phase transitional matter [Qingyuan Wang, Chengfeng Pan, Yuanxi Zhang, Lelun Peng, Zhipeng Chen, Carmel Majidi, and Lelun Jiang / Matter]