Tad Hogg
Abstract
Multiagent control provides strategies for aggregating microscopic robots (“nanorobots”) in fluid environments
relevant for medical applications. Unlike larger robots, viscous forces and Brownian motion
dominate the behavior. Examples range from modified microorganisms (programmable bacteria) to future
robots using ongoing developments in molecular computation, sensors and motors. We evaluate controls
for locating a cell-sized area emitting a chemical into a moving fluid with parameters corresponding to
chemicals released in response to injury or infection in small blood vessels. These control methods are passive
Brownian motion, following the chemical concentration gradient, and cooperative behaviors in which
some robots use acoustic signals to guide others to the chemical source. Control performance is evaluated
using diffusion equations to describe the robot motions and control state transitions. The quantitative results
show these control techniques are feasible approaches to the task with trade-offs among fabrication
difficulty, response speed, false positive detection rate and energy use. Controlled aggregation at chemically
distinctive locations could be useful for sensitive diagnosis, selective changes to biological tissues and
forming structures using previous proposals for multiagent control of modular robots.
Preprint in pdf format (published in Autonomous Agents and Multi-Agent Systems, 14:271-305 (2007))
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