Designing Time-varying Fields to Encode the Autonomous Navigation of Micro-robots

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Mobile robots use sensory information about their environment to direct their actions autonomously toward specific goals such as cargo delivery, waste removal or materials repair. Achieving similar goals in microscopic environments, such as inside the human vascular system, requires robots with dimensions that are comparable to those of living cells. However, so-called “micro-robots” are not autonomous. Instead, they require on external sensor and controllers to direct their motion and other actions. The goal of this project is to create autonomous micro-robots that can navigate local variations in their environment with external supervision. The micro-robots are based on small particles that can be energized by placing them in time-varying magnetic fields. Once the dynamics of the particles in the magnetic field are understood, the project will design fields that direct particle motion along gradients in surface topography (topotaxis) and fluid velocity (rheotaxis). In addition to providing research training for graduate and undergraduate students, the project will include educational outreach to young women in high school interested in pursuing STEM fields. In partnership with the 'Girls in STEM' summer program at the Courant Institute, summer research projects on micro-robotics will train students on the integration of data, models, and design to advance engineering goals.Existing micro-robots based on field-driven particles rely on knowledge of the current position and the target destination to control particle motion through fluid environments. These external control strategies often are challenged by limited information (i.e., particle positions are unknown) and global actuation (i.e., particles move in a common field). This project will use time-varying magnetic fields in three-dimensions to encode the autonomous navigation of multiple particles in response to gradients in the particle environment—particularly, those in topography (topotaxis) and velocity (rheotaxis). Importantly, the field does not instruct particles on where to move but rather on how to respond to local variations in the environment. As a result, the same field can drive multiple particles to move simultaneously in different directions. Building on model predictions, the project aims (1) to demonstrate experimentally the autonomous navigation of magnetic micro-particles across complex topographic landscapes, (2) to design improved driving protocols informed by automated experiments and dynamical models, and (3) to develop rheotactic particles capable of navigating velocity gradients within microfluidic channels. These aims will be achieved through a combination of experiments on magnetic micro-spheres and ellipsoids driven by time-periodic fields and dynamical models based on low Reynolds number hydrodynamics informed and augmented by particle tracking data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.