Turning-rate Selective Control : A New Method for Independent Control of Stress-engineered MEMS Microrobots,
by I. Paprotny, C. Levey, and B. R. Donald.

Summary of paper: We present a novel method for independently controlling multiple stress-engineered MEMS microrobots (called "MicroStressBots") through a single, global, control signal. As can be seen in the optical microscope image (left), the microrobots are about 200 microns long. We named our technique Turning-rate Selective Control (TSC).

To implement TSC, we designed the microrobots to have different turning rates. TSC specifically exploits the differences in turning rates between individual microrobots to differentiate their motion, and thereby obtain individual control.

Thus, even though all robots move simultaneously, and are identical except for their turning rates, TSC can individually and independently position the robots' centers of rotation within a planar configuration space. This allows the individual robots to be independently maneuverable to within a distance r from an arbitrary desired goal point in the plane. The distance r is the turning radius (approximately half of a microrobot width).

We describe the theory behind TSC and, by using fabricated microrobots, show experimental results that confirm the feasibility of TSC for controlling multiple MicroStressBots through a single, global, control signal. Our paper further validates the microrobot control paradigm called Global Control, Selective Response that we first introduced in 2007 at the Inaugural Lecture of the Nanotechnology Public Lecture Series at MIT. We conclude by discussing how TSC can significantly extend the maximum number of independently controllable MicroStressBots.