Non-reciprocal chemotactic movement in enzyme cascade under flow-free conditions

Chemotactic guiding by chemical gradients is important because of possible applications in targeted delivery. In addition, the experimental demonstration of microscale non-reciprocal interactions in active systems is fundamentally important. We developed a microchannel architecture that allows reactive particles to be exposed to imposed chemical gradients for a long time under flow-free conditions. Using this setup, we show that particles functionalized with different enzymes show positive chemotactic mobility in response to their respective substrate gradients. Most significantly, when combined, both acid phosphatase- and glucose oxidase-functionalized particles exhibit chemotaxis in response to a gradient of glucose-6-phosphate, which acid phosphatase converts to glucose, the substrate for glucose oxidase. These findings underscore the significance of chemical gradients in directing particle movement, offering insights crucial for understanding swarming and signaling in living systems. The work also constitutes the first step in designing populations of particles with distinct functions that coordinate their behavior.