Ultrasensitive chemotaxis of urease-powered micromotors with reversible regulation by micromolar chemical modulators

Inspired by the chemotactic navigation of biological cells and microorganisms, enzyme-powered micromotors have emerged as promising autonomous systems that convert chemical energy into directional motion. However, the ultrasensitive regulation of their chemotactic responses by low-concentration chemical modulators remains largely unexplored. Herein, we report urease-functionalized micromotors capable of chemotaxis in a three-inlet microfluidic device that generates well-defined lateral urea gradients. The micromotors exhibited self-propulsion driven by urease-catalyzed urea decomposition, and their motility was reversibly modulated by Ag + /DTT-mediated chemical regulation at micromolar levels. Under lateral urea gradients, the micromotors exhibited positive chemotaxis and migrated preferentially toward the substrate-rich stream. Notably, this chemotactic response was suppressed by 1 μM Ag + and restored by 16 μM DTT. The Janus micromotors showed a stronger chemotactic response than their non-Janus counterparts, with transverse displacements of 13.92 ± 0.85 and 10.16 ± 1.92 μm, respectively, highlighting the role of structural asymmetry in converting substrate gradients into directional migration. Furthermore, increasing flow velocity weakened chemotactic migration by restricting the gradient development and shortening the residence time. These results provide a controlled microfluidic platform for evaluating enzyme-powered chemotaxis and provide quantitative insights into how chemical modulators, particle architecture, and flow dynamics jointly govern the ultrasensitive navigation of micromotors in chemically heterogeneous environments.