Bubble-Powered Robots Can Replace Needle Injections

A joint US-Chinese research team just recently developed a new technique that uses bubble-popping as a potential propulsion system for microbots. This important discovery is expected to replace needle-based drug delivery and other interesting applications.

At the core of the new technique is cavitation, or the sudden collapse of bubbles in liquid. Using the energy released from this, the team found that they could make tiny robots (called "jumpers") move incredible distances relative to their size.

Inspired by the way ferns disperse their spores and Archerfish shoot liquid jets, they found that they could generate their own bubbles by heating light-absorbing material with a laser.

These bubbles expand until they can’t hold any more energy, then collapse violently. The collapse releases a shockwave of mechanical energy. That energy is powerful enough, they found, to propel millimetre-sized devices up to 4.92 feet (1.5 metres) into the air.

The robots can also "swim" at a speed of around 26.84 mph (12 meters per second). "The swimming motion is highly controllable, enabling navigation through complex, confined environments such as mazes and microfluidic channels," the researchers explained.

This is very interesting as cavitation is normally thought of as destructive (e.g., it damages ship propellers and pumps). To this end, by carefully controlling the laser heating (intensity, angle, and timing), the researchers can determine the direction of launch, height, and force of the jump, as well as control whether the device should jump, slide, or “swim” in water.

The new technique is not just interesting in and of itself; it could revolutionize some fields, like medicine. For example, it could be used for novel new medical injections and drug delivery methods.

Here, tiny cavitation-propelled devices could be launched into or through the skin, potentially replacing hypodermic needles. They could also deliver drugs precisely inside the body (e.g., directly to a tumour site).

Because the system uses light-triggered heating, it could be tuned for minimally invasive procedures. This is important as traditional microrobots often rely on magnetic fields or chemical fuels for propulsion, which can be hard to control inside the body.

Cavitation, on the other hand, provides a high-energy, controllable launch system that doesn’t require onboard power or moving parts. The technique could also have other applications in the exploration of things in confined or harsh environments.

For example, these "jumpers" can travel across wet or uneven surfaces, suggesting uses in micro-robotics. They could, therefore, explore tight or inaccessible spaces (inside pipes, machinery, or even biological systems).

There could also be interesting applications in biomedical research. The tiny robots could, for example, act as micro-swimmers inside liquid environments like blood or intercellular fluid.