LS13437 - Catalytic micromotors are extremely small moving particles, about the
size of bacterial organisms, that convert chemical energy through a
catalytic reaction involving bubble generation, to propel the particle
through the fluid. Until now direct observation of the bubble
propulsion for spherical micromotors has eluded researchers since bubble
formation is very difficult on convex surfaces. By using larger
micromotors with a reduced surface curvature and an ultra-fast camera,
the bubble growth and burst processes that drive spherical micromotors
have been resolved. Interestingly, it was found that bubble growth
tends to propel the micromotor in one direction, while the bursting of
the bubble that leaves a zone of depression pulls the micromotor back.
The competition between the two processes creates an almost back and
forth motion of the micromotor. However, the growth process induces a
greater displacement than that in the burst process, giving the
micromotor a net displacement in one direction. A theory is developed
that quantitatively describes this behavior. These results provide
further insight into the behavior of micromotors, which are expected to
have various biomedical applications in the future, such as advanced
drug delivery.
