Duke mechanical engineers have built programmable building blocks that assemble a little like Lego, but can rewrite their own mechanical properties on command. Reported in Science Advances by Yun Bai, a doctoral student in Xiaoyue Ni's laboratory, the blocks emulate one of living tissue's defining talents: the ability to change stiffness and shape in real time to suit whatever the moment demands of the body.
Each block is a soft polymer cube around 10.5 millimetres across, containing a three by three by three grid of internal cells filled with a gallium and iron mixture that can exist as solid or liquid at room temperature. Passing an electrical current through chosen cells heats and liquefies them, while cooling sets them solid again, so the same assembled structure can be reprogrammed into different mechanical behaviours again and again.
To prove the point, the team built a robotic fish with a reconfigurable tail that swam along different paths while driven by the same motor. The researchers suggest miniaturised versions could one day navigate blood vessels or form adaptive stents, though such applications remain speculative; for now, the work shows how far programmable matter has moved beyond fixed, single-purpose engineering.