Robots come in all shapes and sizes, but they all have one thing in common — they’re solid. It might seem that there is no other way for a robot to be, but a little film called Terminator 2 suggests otherwise? The liquid metal T-1000 is science fiction, but so-called soft robots might not be impossible. Researchers Lei Sheng, Jie Zhang, and Jing Liu at Tsinghua University in Beijing have developed a way to manipulate liquid metal to make it change shape on command.

When you think of liquid metal, pure elemental mercury probably comes to mind. Of course, mercury is toxic, so building a shape-shifting robot out of it would be a terrible idea (unless the intention is to destroy all humans). The researchers in this case are using a gallium-indium-selenium alloy, which is also liquid at room temperature. With a melting point of just 50 degrees Fahrenheit (10 degrees Celsius), the team was able to move the alloy around in its liquid form by placing it in water and applying voltage.

The researchers were able to produce tiny liquid metal spheres on the surface of a water droplet by carefully controlling the direction and intensity of current. The metal droplet can be moved around and merged with other droplets by shifting the voltage source to different locations as well. It is hoped that further experimentation will reveal what conditions and voltages produce different shapes and movements, which could be used to create simple machines. The gallium-indium-selenium alloy is also bioneutral, so a machine based on carefully controlled liquid metal could even have medical applications.

Simple shapes are a long way from the T-1000, but every robot apocalypse has to start somewhere.