New Magnetic Spray Transforms Objects Into Insect-Scale Robots for Biomedical Applications

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Different Millirobots

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The reptile millirobot modifications from caterpillar movement to concertina movement after reprogramming. Credit: City University of Hong Kong

An simple method to make millirobots by finishing things with a glue-like magnetic spray was established in a joint research study led by a researcher from City University of Hong Kong (CityU). Driven by the electromagnetic field, the layered things can crawl, stroll, or roll on various surface areas. As the magnetic finishing is biocompatible and can be broken down into powders when required, this innovation shows the capacity for biomedical applications, consisting of catheter navigation and drug shipment.

The research study group is led by Dr. Shen Yajing, Associate Professor of the Department of Biomedical Engineering (BME) at CityU in partnership with the Shenzhen Institutes of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS). The research study findings have actually been released in the clinical journal Science Robotics, entitled “An agglutinate magnetic spray transforms inanimate objects into millirobots for biomedical applications.”


An simple method to make millirobots by finishing things with a magnetic spray was established in a joint research study led by a researcher from CityU. As the magnetic finishing is biocompatible and can be broken down into powders when required, this innovation shows the capacity for biomedical applications. Credit: City University of Hong Kong

Transforming things into millirobots with a “magnetic coat”

Scientists have actually been establishing millirobots or insect-scale robotics that can adjust to various environments for expedition and biomedical applications.

Dr. Shen’s research study group created a basic method to build millirobots by finishing things with a composited glue-like magnetic spray, called M-spray. “Our idea is that by putting on this ‘magnetic coat’, we can turn any objects into a robot and control their locomotion. The M-spray we developed can stick on the targeted object and ‘activate’ the object when driven by a magnetic field,” discussed Dr. Shen.

Dr Shen and Team at CityU

Dr. Shen (middle) & the group at CityU. Credit: City University of Hong Kong

Composed of polyvinyl alcohol (PVA), gluten, and iron particles, M-spray can abide by the rough and smooth surface areas of one (1D), 2 (2D) or three-dimensional (3D) things quickly, stably, and strongly. The movie it formed on the surface area is almost 0.1 to 0.25mm thick, which is thin enough to protect the initial size, type, and structure of the things.

After finishing the item with M-spray, the scientists allured it with single or several magnetization instructions, which might manage how the item moved by an electromagnetic field. Then they used heat on the item till the finishing was strengthened.

In in this manner, when driven by an electromagnetic field, the things can be changed into millirobots with various mobility modes, such as crawling, turning, strolling, and rolling, on numerous surface areas from glass, skin, wood to sand. The group showed this function by transforming cotton thread (1D), origami (2D flat aircraft), polydimethylsiloxane (PDMS) movie (2D curved/soft surface area) and plastic pipeline (3D round item) into soft reptile robotic, multi-foot robotic, strolling robotic and rolling robotic respectively.

On-need reprogramming to alter mobility mode

What makes this method unique is that the group can reprogram the millirobot’s mobility mode as needed.

Mr. Yang Xiong, the co-first author of this paper, discussed that traditionally, the robotic’s preliminary structure is typically repaired once it is built, for this reason constraining its flexibility in movement. However, by moistening the strengthened M-spray finishing totally to make it adhesive like glue and after that by using a strong electromagnetic field, the circulation and positioning instructions of the magnetic particles (simple magnetization axis) of the M-spray finishing can be altered.

On-Demand Millirobot Reprogramming

The reptile millirobot modifications from caterpillar movement to concertina movement after reprogramming. Credit: City University of Hong Kong

Their experiments revealed that the exact same millirobot might change in between various mobility modes, such as from a quicker 3D caterpillar motion in a roomy environment to a slower 2D concertina motion for going through a narrow space.

Navigating capability and disintegrable home

This reprogrammable actuation function is likewise practical for navigation towards targets. To check out the capacity in biomedical applications, the group performed try outs a catheter, which is commonly utilized for placing into the body to deal with illness or carry out surgeries. They showed that the M-spray layered catheter might carry out sharp or smooth turns. And the effect of blood/liquid circulation on the movement capability and stability on the M-spray layered catheter was restricted.

By reprograming the M-spray finishing of various areas of a cotton thread based upon the shipment job and environment, they even more revealed that it might attain a fast-steering and efficiently travel through an irregular, narrow structure. Dr. Shen mentioned that from the view of medical application, this can avoid the unanticipated plunging in the throat wall throughout insertion. “Task-based reprogramming offers promising potential for catheter manipulation in the complex esophagus, vessel, and urethra where navigation is always required,” he stated.

Another crucial function of this innovation is that the M-spray finishing can be broken down into powders as needed with the control of an electromagnetic field. “All the raw materials of M-spray, namely PVA, gluten, and iron particles, are biocompatible. The disintegrated coating could be absorbed or excreted by the human body,” stated Dr. Shen, worrying the adverse effects of the disintegration of M-spray is minimal.

Successful drug shipment in bunny stomach

To more validate the expediency and efficiency of the M-spray allowed millirobot for drug shipment, the group carried out in vivo test with bunnies and pill covered with M-spray. During the shipment procedure, the bunnies were anesthetized, and the position of the pill in the stomach was tracked by radiology imaging. When the pill reached the targeted area, the scientists broke down the finishing by using an oscillating electromagnetic field. “The controllable disintegration property of M-spray enables the drug to be released in a targeted location rather than scattering in the organ,” Dr Shen included.

Though the M-spray finishing will begin to break down in about 8 minutes under highly acidic environment (pH level 1), the group revealed that an extra PVA layer on the surface area of the M-spray finishing might lengthen it to about 15 minutes. And if changing the iron particles with nickel particles, the finishing might keep steady in a highly acidic environment even after 30 minutes.

“Our experiment results indicated that different millirobots could be constructed with the M-spray adapting to various environment, surface conditions, and obstacles. We hope this construction strategy can contribute to the development and application of millirobots in different fields, such as active transportation, moveable sensor and devices, particularly for the tasks in limited space,” stated Dr. Shen.

Reference: 18 November 2020, Science Robotics.
DOI: 10.1126/scirobotics.abc8191

Dr. Shen from CityU and Dr. Wu Xinyu from SIAT of CAS are the matching authors of the paper. The very first authors are Mr. Yang Xiong, a PhD trainee from BME at CityU and Dr. Shang Wanfeng from SIAT CAS. Other co-authors are Dr. Lu Haojian, Dr. Liu Yanting, Mr. Yang Liu, and Miss Tan Rong, brand-new graduates and PhD trainees from Dr. Shen’s group.

The research study was supported by the National Science Foundation of China and the Research Grants Council of Hong Kong.