In the case of exploration and biomedical applications, millirobots with the ability to adapt to unstructured surroundings, work in limited spaces, and interact with a wide range of objects would be highly preferable.
However, designing millirobots has been very difficult as they involve complex fabrication methods.
Scientists from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences collaborated with the City University of Hong Kong (CityU) to design a reprogrammable, agglutinate, biocompatible, and disintegrable magnetic spray (M-spray) that can easily convert inanimate objects into millirobots.
The study results have been reported in an article titled “An agglutinate magnetic spray transforms inanimate objects into millirobots for biomedical applications,” published in the Science Robotics journal.
The magnetic spray (M-spray) is primarily composited from gluten, polyvinyl alcohol (PVA), and magnetic particles. The M-skin developed by using the M-spray is reprogrammable by tweaking the easy magnetization direction without altering the main structure.
Thorough wetting of the covered spray leads to an increase in the spacing between magnetic particles as a result of PVA swelling, and the constraints on magnetic particles from the gluten and PVA get decreased considerably.
Consequently, the magnetic particles present within the spray can be rearranged along the direction of magnetic flux and can subdue the constraints when a strong magnetic field is applied.
The on-demand reprogramming ability endows millirobots with high adaptivity to achieve diverse locomotion. The team demonstrated the reprogramming of a three-section reptile millirobot that could move with 3D caterpillar motion before reprogramming and 2D concertina after reprogramming.
Dr SHANG Wanfeng, Study Co-First Author and Associate Professor, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences
Furthermore, the M-spray can be detached by increasing the magnetic particles’ kinetic energy to overcome the inner constraints. This is achieved by employing an oscillating magnetic field in an aqueous surrounding. This magnetically induced disintegration guarantees that the developed millirobot can disintegrate as expected.
Moreover, the study evidenced possible applications in the biomedical area, such as the navigation potential of an M-spray-covered catheter in the narrow vascular model, the reprogramming of multipoint sampling cotton thread for several sets of steering, and a magnetic spray-covered capsule for active delivery.
A rabbit stomach experiment illustrated that a developed capsule millirobot can effectively improve the retention and the concentration of a drug in particular lesions.
This research offers a general on-demand robot construction method by leveraging the structure and morphology of the targeted objects themselves. With biocompatible components, the side effects from its disintegration are negligible, making it a good candidate for biomedical applications.
Dr WU, Shenzhen Institutes of Advanced Technology
Yang, X., et al. (2020) An agglutinate magnetic spray transforms inanimate objects into millirobots for biomedical applications. Science Robotics. doi.org/10.1126/scirobotics.abc8191.