Robots now rewrite their stiffness to swim, bend, and adapt

Mechanical engineers at Duke University have created programmable solid building blocks whose mechanical properties—such as stiffness, damping, and movement—can be dynamically altered without changing their overall shape. These Lego-like cubes contain 27 internal cells filled with a gallium-iron composite that can switch between solid and liquid states at room temperature when heated via electrical current. By selectively liquefying specific cells, the researchers can encode different mechanical behaviors into the blocks. Demonstrations showed that beams and columns made from these cubes could vary from soft rubber-like to stiff plastic-like responses, and a robotic fish equipped with a column of these cubes altered its swimming paths solely through internal reconfiguration. This technology represents a shift from traditional shape-shifting materials by enabling real-time changes in mechanical response while maintaining geometry. The modular cubes can be assembled or detached like Lego bricks, allowing for customizable 3D structures with tunable mechanical properties. Additionally, freezing the blocks at zero degrees Celsius resets all cells to solid, enabling repeated reprogramming cycles