Microbots swarm and shape-shift

Scientists have demonstrated that microrobots of a single “species” can shape-shift as a collective into various formations and organise themselves to carry out diverse tasks in variable environments.

Unlike living species with a known ability to work together, such as ants and fish, the bots don’t have smarts to rely on sensory function and communication. The researchers had to use external magnetic or electric fields to control them.

But even so, they exhibited enough versatility and multitasking capability to suggest they could one day be used for inner-body diagnostics or biomedical treatment at the cellular or molecular level.

The research was led by Hue Xie from the State Key Laboratory of Robotics and Systems at China’s Harbin Institute of Technology, and reported in the journal Science Robotics.{%recommended 7456%}

Big advances with small robots are coming thick and fast. Earlier this month, for example, US researchers described how they created a million of them in just a few weeks using nanofabrication techniques borrowed from the semiconductor industry.

However, as Xie and colleagues note in their paper, “integrating drive and sensing functions into micro- and nanoscale robots remains a challenge” and you need to have an awful lot of them working together to actually be of use, say, inside a human body.

In their recent work they were able to program switchable transformation behaviour in a robotic swarm by regulating the movement of each individual microrobot. By tuning the frequency and direction of a rotating magnetic field, each individual microrobot – a peanut-shaped hematite particle – exhibited oscillating, rolling, tumbling and spinning movements. 

Depending on the type of individual movement, the robots as a group self-organised into different formations of liquid (an evenly distributed pattern of robots), chains (robots connected in long and parallel rows travelling by the short end), ribbon (rows of robots travelling by the long end) and vortex (circular crowds of robots), respectively. 

The researchers could also change the swarm’s speed and direction, by tweaking the applied magnetic field. 

The microrobot collective accomplished a variety of tasks by switching between conformations; for example, using the “chain” formation to cross narrow channels, then the “vortex” to lift heavy loads.

Xie and colleagues say their findings support and demonstrate the idea of achieving the control of a variety of synthetic and living active matter via a programmed external stimulus, “thus increasing the possibilities of emulating living systems by active matter”. 

“Moreover, the physical mechanisms that govern the dynamics of out-of-equilibrium colloidal systems were carefully investigated, which is helpful for achieving a better understanding of the cooperative mechanisms and self-organisation phenomena that occur in active systems,” they write.

“This provides potential solutions for biomedical applications, such as imaging and targeted drug delivery.”