‘Microbubbles’ are here to help power tiny medical robots

23 Nov 2016

Image: Astrid Gast/Shutterstock

Researchers in Germany think they’ve found a way to harness magnetic fields to greater effect in tiny robots, using microbubbles to power devices.

In recent years, a growing field of medical research and engineering has focused on microrobots, designed to deliver treatments or diagnose illnesses within the human body.

Last August, for example, nanoengineers at the University of California utilised innovative 3D-printing technology to manufacture fish-shaped microrobots ­– dubbed microfish – that may one day be used in detoxification, targeted drug delivery or even surgery.

A related piece of research this summer showed how robots that look and move like bacterium could achieve something similar.


However, achieving anything like suitable treatment through these devices requires immense control of power and movement – something lacking when relying on magnetic fields.

Small-scale motors are needed in bots, with magnetic fields the power mode of choice at the moment.

However, according to Tian Qiu, a researcher at the Max Planck Institute for Intelligent Systems in Germany, magnetic fields do not provide selectivity since all actuators (the components controlling motion) under the same magnetic field just follow the same motion.

So Qiu and a team of researchers thought of a new way, ultimately developing a process whereby microbubbles provide the specificity needed to power microrobots for biomedical applications. The paper is available here.

This process, according to the team, provides numerous advantages in terms of powering microrobots.

“First, by applying ultrasound at different frequencies, multiple actuators can be individually addressed; second, the actuators require no on-board electronics which make them smaller, lighter and safer; and third, the approach is scalable to the sub-millimetre size,” according to Qiu.

To create the actuator, the team used a standard commercial polymer that simply traps air bubbles, and then used the liquid air.

“We found that a thin surface (30-120 micrometers effective thickness) with appropriate topological patterning can provide propulsion force using ultrasound, and thousands of these bubbles together can push a device at millimetre scale,” Qiu said.

“The simplicity of the structure and material to accomplish this task was a pleasant surprise,” added Qiu, noting that the next stage was upping the “propulsive force” and ultimately, testing it in a real biological experiment.

Gordon Hunt was a journalist with Silicon Republic