Building robots out of bubbles is an intriguing idea in its own right, but propelling them with lasers is just plain crazy. The bubble microrobots, devised by the researchers from the University of Hawaii at Manoa, have no mechanical parts whatsoever, but can nevertheless be manipulated with very high precision. Combined into complex robotic systems, they could potentially be used to assemble larger objects, such as biological cells.
To make a bubble micro robot, shine a 400 mW 980 nanometer laser beam into the globule of a regular bubble resting on a heat-absorbing surface, surrounded with a saline solution. As the surrounding fluid moves away from the spot heated up by the laser, the bubble is propelled towards that spot. The location of the bubble changes along with the target location of the laser beam, and the stronger the light, the faster the bubble moves (the top speed is around 4 mm/s or 0.15 ips). The level of precision is finely illustrated by the picture below, which shows 100-µm-diameter glass beads arranged by a microrobot (visible in the top center of the image) to form the acronym for the University of Hawaii (UH).
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This unconventional approach means that a virtually unlimited number of tiny robots can be brought in and out of existence instantly, as the need arises and at almost no cost. No assembly is necessary – all you need to create a robot is a syringe full of air. Another major advantage over alternative, less “ephemeral” microrobotic systems is the fact that each bubblebot can be steered independently by separate lasers (this is not necessarily the case with magnetically controlled microrobots).
On the other hand, the obvious limitation of the system is that it operates in a liquid environment (this is not to say it is necessarily a disadvantage). Next steps include using arrays of lasers to get whole teams of robotic bubbles to assemble tiny beads into more and more complex shapes. The goal is to create a system capable of assembling microstructures as complex as cells, possibly autonomously.
One of the microrobots can be seen in action in the video below.