(171z) A Microrobotic Design for the Spontaneous Tracing of Isochemical Contours in the Environment

Microrobotic platforms hold significant potential to advance a variety of fields, from medicine to environmental sensing because of their ability to bring electronics to otherwise inaccessible locations. However, given their small volume, the unfavorable scaling of energy and computation constrains options for their control to relatively simple mechanisms. The prospect of algorithmic design built into their construction is a compelling solution to such constraints, enabling emergent, collective functions. However, this motivates the study of how simple device operations can give rise to such functions. In this work, we computationally simulate minimally functional robotic entities modeled on readily achievable state-of-the-art features in a modern lab or cleanroom. Inspired by Dou and Bishop (Phys Rev Res. 2019;1(3):1-5), we show that the simple combination of unidirectional steering connected to a single environmental (chemical) sensor along with constant propulsion gives rise to highly complex functions of significant utility. Such systems can trace the contours orthogonal to arbitrary chemical gradients in the environment. Also, pairs of such robots that are additionally capable of emitting the same chemical signal are shown to exhibit coupled relative motion. When the pair has uni-directional steering in opposite directions within the 2D plane (i.e. counter-rotating) they move in parallel trajectories to each other. Alternatively, when steering is in the same direction (co-rotation), the two move in the same epicyclical trajectory. In this way, the chirality of the uni-directional steering produces two distinct emergent phenomena. The behavior in all cases is understood as a ratchet mechanism that exploits the differential in the radii of curvature corresponding to different spatial locations. Applications to environmental detection, remediation and monitoring are discussed. This work provides a template for how simple, easily fabricated micro-robotic platforms, can achieve highly complex behavior such as circumnavigation, control of relative positioning and directionality of and within a micro-robotic swarm.