Autonomous oscillatory movement of sensory protocells in stratified chemical media
Patrick Peschke, B. V. V. S. Pavan Kumar, Tobias Walther, Avinash J. Patil, Stephen Mann
Abstract
The taxis of microscale objects in response to environmental chemical gradients represents a fundamental step toward the construction and programming of motile cytomimetic agents. Here, we demonstrate that various modes of autonomous oscillatory movement can be implemented across stratified chemical media by sensory-mediated actuation of protocell buoyancy. We use enzyme-powered peptide/polynucleotide protocells as microscale agents that sense and move in response to stationary or diffusive chemical fronts present in their local environment. By using stratified sucrose density gradients of antagonistic enzyme substrates, sustainable non-harmonic oscillatory movements, short-lived quasi-harmonic trajectories, damped harmonic behaviors, and states of protocell levitation are implemented under non-equilibrium conditions. Furthermore, transitions from harmonic to damped oscillatory trajectories provide a spatiotemporal mechanism for transient protocell-mediated reactivity and execute protocell logistics using an oscillatory cell-like transporter capable of repeated pick-up and delivery of molecular cargo. Our work provides opportunities for the development of soft microrobotics and sensing/delivery microscale agents.