Vapor Bubbles in Microchannels

Vapor and gas bubbles are used to pump liquid in microchannels when conventional pumps cannot be efficient, e.g. in micro-actuators. They also push individual droplets of liquid ink out of a channel in bubble-jet printers. Recently, scientists proposed using bubble surfaces as micro-mirrors for reflecting optical signals in a switching device for optical communications networks. This design may lead to a dramatic increase in the speed of the Internet. Numerous applications of bubbles rely on the fact that they can be created by localized heating very quickly and then disappear when the heating is off. Professor Ajaev has developed mathematical models that predict the shape of a vapor bubble in a rectangular microchannel heated from below, shown in the figure, and estimate how quickly the bubble changes its shape when the heating conditions are changed. Recently, he and his collaborators at the University of California started working on applying the same ideas to heat pipes, which are small devices used to prevent over-heating of laptop computers and mobile phones.