Distributed Control of Microscopic Robots in Biomedical Applications

TL;DR

This paper reviews the potential and control strategies for microscopic robots in biomedical applications, highlighting their capabilities, physical constraints, and ability to perform high-resolution sensing in vivo.

Contribution

It introduces simple distributed control methods for microscopic robots, demonstrating their effectiveness in biomedical tasks like chemical source detection within flowing fluids.

Findings

Microscopic robots can discriminate single-cell chemical sources from background.

Distributed control enables real-time decision-making in fluid environments.

High-resolution sensing is achievable with large numbers of microscopic devices.

Abstract

Current developments in molecular electronics, motors and chemical sensors could enable constructing large numbers of devices able to sense, compute and act in micron-scale environments. Such microscopic machines, of sizes comparable to bacteria, could simultaneously monitor entire populations of cells individually in vivo. This paper reviews plausible capabilities for microscopic robots and the physical constraints due to operation in fluids at low Reynolds number, diffusion-limited sensing and thermal noise from Brownian motion. Simple distributed controls are then presented in the context of prototypical biomedical tasks, which require control decisions on millisecond time scales. The resulting behaviors illustrate trade-offs among speed, accuracy and resource use. A specific example is monitoring for patterns of chemicals in a flowing fluid released at chemically distinctive sites. Information collected from a large number of such devices allows estimating properties of cell-sized chemical sources in a macroscopic volume. The microscopic devices moving with the fluid flow in small blood vessels can detect chemicals released by tissues in response to localized injury or infection. We find the devices can readily discriminate a single cell-sized chemical source from the background chemical concentration, providing high-resolution sensing in both time and space. By contrast, such a source would be difficult to distinguish from background when diluted throughout the blood volume as obtained with a blood sample.