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Millimeter-Sized Robots Controlled With Magnetic Fields

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Scientists at Nanyang Technological University, Singapore (NTU Singapore) have developed millimeter-sized robots that are controlled with magnetic fields. These robots are capable of executing highly maneuverable and dexterous manipulation, and they could have a big impact in fields like biomedicine and manufacturing. 

The research was published in the scientific journal Advanced Materials in May. 

Building Upon Existing Small-Scale Robots

The miniature robots were created by embedding magnetic microparticles into biocompatible polymers, which are non-toxic materials to humans. The robots are programmed so that when magnetic fields are applied, they carry out their desired functionalities. 

The new technology built upon previous small-scale robots, and the new additions include an optimized ability to move in six degrees-of-freedom (DoF), which is translational movement along the three spatial axes and rotational movement about those axes, or roll, pitch, and yaw angles. 

The researchers have already previously developed six DoF miniature robots, but the new versions can rotate 43 times faster in the critical sixth DoF, as long as their orientation is precisely controlled.

Grain-sized robots made by NTU Singapore scientists

Because of the use of ‘soft’ materials in their construction, the robots can replicate mechanical qualities. For example, one can swim while another can grip, pick up, and place miniature objects precisely. 

Assistant Professor Lum Guo Zhan from the School of Medicine and Aerospace Engineering is the lead author of the study.

According to Professor Lum, the major advancement heavily depends on the discovery of the ‘elusive’ third and final principal vector of the magnetic fields. Prior to this discovery, the applied magnetic fields were only defined in terms of two principal vectors. 

“My team sought to uncover the fundamental working principles of miniature robots that have six-DoF motions through this work. By fully understanding the physics of these miniature robots, we are now able to accurately control their motions. 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,” said Asst. Prof Lum.

The miniature robots measure out to about the size of a grain of rice, so they are useful when trying to get to confined and enclosed spaces that limit large robots. This means the new development is especially useful in medicine.

The robots can be controlled remotely by an operator and a program running on a control computer. The program alters the strength and direction of magnetic fields generated by an electromagnetic coil system. 

In medicine, the miniature robots could reach certain vital organs like the brain, but there will need to be a lot more testing and tweaking before they can be applied in this way.

The co-authors of the research include PhD students Xu Changyu and Yang Zilin from the School of Mechanical and Aerospace Engineering. 

“Besides surgery, our robots may also be of value in biomedical applications such as assembling lab-on-chip devices that can be used for clinical diagnostics by integrating several laboratory processes on a single chip,” they said. 

Testing the Robots

The research team tested the robots in lab experiments and demonstrated their dexterity and speed. 

With a jellyfish-inspired bot, the team controlled it to swim through a tight opening barrier when suspended in water. This experiment demonstrated how the robots can negotiate barriers in dynamic and uncertain environments, meaning in the future, they could be used for targeted biomedical applications like surgical procedures. 

The miniature robot also exceeded the fastest rotation of any existing miniature robots. 

The research team will now look to make the robots even smaller, bringing them down to a few hundred micrometers. They also want them to eventually be fully autonomous.