Microscopic Robots That Sense, Think, Act, and Compute

While miniaturization has been a goal in robotics for nearly 40 years, roboticists have struggled to access sub-millimeter dimensions without making sacrifices to on-board information processing due to the unique physics of the microscale. Consequently, microrobots often lack the key features that distinguish their macroscopic cousins from other machines, namely on-robot systems for decision making, sensing, feedback, and programmable computation. Here, we take up the challenge of building a microrobot comparable in size to a single-celled paramecium that can sense, think, and act using onboard systems for computation, sensing, memory, locomotion, and communication. Built massively in parallel with fully lithographic processing, these microrobots can execute digitally defined algorithms and autonomously change behavior in response to their surroundings. Combined, these results pave the way for general purpose microrobots that can be programmed many times in a simple setup, cost under $0.01 per machine, and work together to carry out tasks without supervision in uncertain environments.

Artificial Spacetimes for Reactive Control of Resource-Limited Robots

Field-based reactive control provides a minimalist, decentralized route to guiding robots that lack onboard computation. Such schemes are well suited to resource-limited machines like microrobots, yet implementation artifacts, limited behaviors, and the frequent lack of formal guarantees blunt adoption. Here, we address these challenges with a new geometric approach called artificial spacetimes. We show that reactive robots navigating control fields obey the same dynamics as light rays in general relativity. This surprising connection allows us to adopt techniques from relativity and optics for constructing and analyzing control fields. When implemented, artificial spacetimes guide robots around structured environments, simultaneously avoiding boundaries and executing tasks like rallying or sorting, even when the field itself is static. We augment these capabilities with formal tools for analyzing what robots will do and provide experimental validation with silicon-based microrobots. Combined, this work provides a new framework for generating composed robot behaviors with minimal overhead.

Electrokinetic Propulsion for Electronically Integrated Microscopic Robots

Robots too small to see by eye have rapidly evolved in recent years thanks to the incorporation of on-board microelectronics. Semiconductor circuits have been used in microrobots capable of executing controlled wireless steering, prescribed legged gait patterns, and user-triggered transitions between digital states. Yet these promising new capabilities have come at the steep price of complicated fabrication. Even though circuit components can be reliably built by semiconductor foundries, currently available actuators for electronically integrated microrobots are built with intricate multi-step cleanroom protocols and use mechanisms like articulated legs or bubble generators that are hard to design and control. Here, we present a propulsion system for electronically integrated microrobots that can be built with a single step of lithographic processing, readily integrates with microelectronics thanks to low current/low voltage operation (1V, 10nA), and yields robots that swim at speeds over one body length per second. Inspired by work on micromotors, these robots generate electric fields in a surrounding fluid, and by extension propulsive electrokinetic flows. The underlying physics is captured by a model in which robot speed is proportional to applied current, making design and control straightforward. As proof, we build basic robots that use on-board circuits and a closed-loop optical control scheme to navigate waypoints and move in coordinated swarms. Broadly, solid-state propulsion clears the way for robust, easy to manufacture, electronically controlled microrobots that operate reliably over months to years.