24 May 2022

Highly manoeuvrable miniature robots controlled by magnetic fields

Scientists at Nanyang Technological University have developed millimetre-sized robots that can be controlled using magnetic fields to perform highly manoeuvrable and dexterous manipulations. This could pave the way to possible future applications in biomedicine and manufacturing

The miniature robots are created by embedding magnetic microparticles into biocompatible polymers — harmless non-toxic materials. The robots are ‘programmed’ to execute their desired functionalities when magnetic fields are applied.

These robots improve on many existing small-scale robots by optimizing their ability to move in six degrees-of-freedom – that is, translational movement along the three spatial axes, and rotational movement about those three axes, commonly known as roll, pitch and yaw.

The new miniature robots can rotate 43 times faster than previous designs in the critical sixth DoF when their orientation is precisely controlled. They can also be made with ‘soft’ materials and thus can replicate important mechanical qualities — one type can ‘swim’ like a jellyfish, and another has a gripping ability that can precisely pick and place miniature objects.

According to Assistant Professor Lum Guo Zhan from the School of Mechanical and Aerospace Engineering, the crucial factor is the discovery of the ‘elusive’ third and final principal vector of these magnetic fields, which is critical for controlling such machines. In contrast, previous versions had only defined the applied magnetic fields in terms of two principal vectors.

“By fully understanding the physics of these miniature robots, we are now able to accurately control their motions, he said. “Furthermore, our proposed fabrication method can magnetise these robots to produce 51 to 297 folds larger six-DoF torques than other existing devices. Our findings are therefore pivotal, and they represent a significant advancement for small-scale robotic technologies.”

Remote-controlled miniature robots suitable for surgical, manufacturing use

Measuring about the size of a grain of rice, the miniature robots may be used to reach confined and enclosed spaces currently inaccessible to existing robots, say the NTU team, making them particularly useful in the field of medicine.

Movement can be controlled remotely by an operator, using a programme running on a control computer that precisely varies the strength and direction of magnetic fields generated by an electromagnetic coil system.

In future, the miniature robots may also inspire novel surgical procedures for ‘difficult-to-reach’ vital organs, such as the brain, though much more work and testing is needed before the miniature robots can eventually be deployed for medical applications.

Besides surgery, the robots may also be of value in biomedical applications such as assembling lab-on-chip devices; these are used for clinical diagnostics by integrating several laboratory processes on a single chip.

With their gripper robot, the scientists were able to assemble a 3D structure consisting of a bar sitting atop two Y-shaped stilts in less than five minutes, about 20 times faster than existing miniature robots have been able to. This proof-of-concept demonstration, say the researchers, suggests that one day they may be used in ‘micro factories’ that build microscale devices.

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