Bubble-powered drug-delivery microbots are steered by ultrasound
Although many scientists have been working on microscopic "robots" that could deliver drugs to specific locations within the body, one challenge remains – powering the things without the use of bulky onboard batteries. A new approach utilizes ultrasound waves that act on tiny bubbles.
Led by Prof. Mingming Wu, scientists at Cornell University started by utilizing a laser lithography system to 3D print animal-cell-sized triangular "micro-robotic swimmers." Each one is made of a hydrophobic (water-repelling) resin, and has two cavities etched into its back – the openings of those two cavities are of different diameters. Because the resin is hydrophobic, an air bubble forms in each cavity when one of the swimmers is placed in a liquid environment.
When an external ultrasound transducer is subsequently aimed at the swimmer, the sound waves cause the bubbles to oscillate, generating vortices that propel the robot forward. However, by varying the resonance frequency of the waves, it's possible to selectively excite either of the bubbles individually, or both of them at the same time.
In this way, the swimmer can be steered by remote control. While previous studies have produced microbots that were propelled by a single bubble, they had to be steered using two ultrasound transducers. By contrast, the Cornell swimmers are reportedly the first that only require one transducer, thanks to their dual-bubble design.
The scientists are now working on making the robots out of biocompatible and biodegradable materials, so they will harmlessly dissolve within the body once their job is done.
A paper on the research was recently published in the journal Lab on a Chip.
Source: Cornell University