Physicists have long struggled to understand the quirky material vanadium dioxide (VO2). At temperatures >67 °C this metal oxide acts as a conductor. Cool it to a moderate temperature, however, and VO2 quickly rearranges its interior structure to become an insulator. And we are talking quick: Some have estimated the transition to happen in a trillionth of a second in a controlled environment. As researchers have increased their understanding of this inorganic compound, which changes so abruptly with respect to both its structure and its conductivity, some have looked for ways—from electronics to optics—to take advantage of the uniqueness of VO2. We review a new application of VO2 and its potential clinical impact: as a microactuator. Scientists are no strangers to actuators. Piezoelectrics, differential thermal expansion, and shape-memory alloys—all are used to explore ways to transduce an external stimulus into mechanical action. The investigators in a new proof-of-concept study have proposed that VO2 be the next actuator possibility on everyone's list. While studying the compound's dual-phase transition, a team of researchers led by Junqiao Wu at the University of California, Berkeley, came to realize that the structure moves quite dramatically during its phase transition: a 100-μm VO2 wire consistently shrank by about 1 μm in length. According to the researchers, this 1% change in length is much greater than the approximately 0.005% observed with regular thermal-expansion materials. Given the extent of the shrinkage, the speed of the transition, and the energy produced in the metal–insulation phase transition, the researchers calculated that a work density of 7 J/cm …