  Microscopic robots could perform tasks with high spatial precision, such as
acting on precisely-targeted cells in biological tissues. Some tasks may
benefit from robots that change shape, such as elongating to improve chemical
gradient sensing or contracting to squeeze through narrow channels. This paper
evaluates the energy dissipation for shape-changing (i.e., metamorphic) robots
whose size is comparable to bacteria. Unlike larger robots, surface forces
dominate the dissipation. Theoretical estimates indicate that the power likely
to be available to the robots, as determined by previous studies, is sufficient
to change shape fairly rapidly even in highly-viscous biological fluids.
Achieving this performance will require significant improvements in
manufacturing and material properties compared to current micromachines.
Furthermore, optimally varying the speed of shape change only slightly reduces
energy use compared to uniform speed, thereby simplifying robot controllers.

Robotics;Biological Physics