Figure 5.

Actuation and steering demonstrations of the microrollers and microscrews using a rotating magnetic field, and demonstration of their spatial adaptability by their temperature-dependent size control. (a) Schematic illustration of magnetic actuation and steering of the microrollers. (b) Controlled surface rolling trajectory snapshots (blue lines) of a microroller at a 10 mT rotating magnetic field at 0.8 and 1.5 Hz on a smooth glass substrate inside deionized water. (c) Mean motion speed of the microrollers as a function of magnetic rotation frequency. (d) Magnetic steering control snapshots of the double-helical microscrews at 10 mT rotating magnetic field at 0.8 Hz. (e) Mean speed of microscrews with different rotation frequencies. (f) Schematic diagram and optical images of the microroller showing the spatial adaptability (shrinkage) by temperature control to pass through a channel smaller than its initial diameter.