Untethered small-scaled magnetic robots have great potential in biomedical applications under magnetic guidance.  

However, the property and locomotion of the tiny robots still remain challenges to fulfill the purpose of minimally invasive medicines in biological region. Especially, due to the materials and functional integrations, the transition of the structure of robot from hard to soft is able to enhance capability of the robots (e.g. soft interface, no harm interaction).  

Researchers from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences utilized magnetic elastomer to fabricate a swimming soft film robot.  

The study named "Magnetic soft robot with the triangular head-tail morphology inspired by lateral undulation", was published in  ASME/ IEEE transactions on Mechatronics and recommended by the Journal technical editor.

Firstly, the magnetic soft robot with the triangular head-tail morphology and sine-based magnetization utilized a high degree of freedom provided by magnetic compliance for mobility in a form of lateral undulation.  

This locomotion system was a reliable and potential movement especially in fluid because the undulating robot generated the pressure gradient on its surface which could enhance the swimming performance.  

That is, a low-pressure region was produced around its body surface, but the high-pressure region was around the head. Due to the distinguish pressure, the racing fluid from the high to low region pulled the robot through, corresponding to a sequence of its body-wave propagation.  

As appeared in the simulation results, the robot generated the travelling wave with the velocity gradient around its surface that was down along the head to the tail. (Video 1)

With this novel design, the fabricated robot could achieve the self-propulsion by the body-wave propagation under the driving of oscillating magnetic field, similar to eel’s slithering. (Video 2)

Next, due to the property of non-uniform magnetic strength, the deformation degree and magnetic response of the robot was tunable. Thus, varying the magnitude of the actuating magnetic field and frequency could empower and adjusted the robot’s performance significantly. The feasibility of the robots was validated and confirmed experimentally in the diverse environmental conditions that mimic biological regions which are extremely complex and unstructured (e.g. in vessel where blood flow is violent, in cerebral fluid where flow rate is slower). (Video 3)

More notably, regarding this locomotion system, the robot could exert the force rate to push out surrounding fabrics which were heavier than itself, for the self-built path in the granular-like media. (Video 4)

Besides, the robot could swim against the flow of fluid by gaining the frequency of the body-wave undulation for the faster swimming speed (Video 5). 

Researchers believed that this contribution leads to the promising application in diverse applications of biomedicines (e.g. fatty or unwanted biological objects removal in vessel).

Figure. (a) Specifications of the robot; (b) Free undulation of the robot in viscous fluid (10mm².s^-1); (c) Force transfer of the undulating robot to the fabric media; (d) Adjustable amplitude of the undulating robot in tubes; (e) and(f) Undulation of the robot in the flow. (Image by SIAT)

Video 1. Numerical simulation of the lateral undulation.  (Video by SIAT)

Video 2. Force-free undulation in large boundary without any obstacle.  (Video by SIAT)

Video 3. Adjustable amplitude to swim within different diameters of tube as confined spaces.  (Video by SIAT)

Video 4. Exerting the force rate to push out surrounding fabrics for the self-built path. (Video by SIAT)

Video 5. Undulation in the flow of viscous fluid. (Video by SIAT)

Media Contact: 
ZHANG Xiaomin 
Email: xm.zhang@siat.ac.cn