Microscopic droplets can now swim indefinitely through a liquid using nothing but chemical reactions and protein separation.
Biological movement usually requires complex molecular motors like the spinning tails found on bacteria. These artificial structures achieve the same result by using active phase separation to create their own propulsion. A simple enzymatic reaction allows the colloid to push itself forward in a perfectly uniform environment without any external power source. This discovery bridges the gap between dead matter and the lifelike movement seen in single-celled organisms. It opens the door for building tiny, self-propelled robots that can navigate the human body using only the chemicals already present in the blood.
Propelling catalytic structures using active phase separation
arXiv · 2604.27965
Living systems routinely consume energy to achieve motility, often using intricate biomolecular machinery. In this work, we show that active droplets can sustain indefinite self-propulsion of a spherical colloid in an otherwise homogeneous, isotropic, and autonomous environment. Our proposed minimal mechanism consists of phase-separating proteins, enzymes passivating them, and complementary enzymes anchored to the colloid surface that reactivate the proteins. This passivation-activation cycle gi