Scientists are making progress in the field of microrobots

Recently, the research group of Shang Wanfeng, Intelligent Bionic Center, Shenzhen Institute of Advanced Integrated Technology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, has cooperated with the Intelligent Manufacturing Center of the Hong Kong University of Science and Technology to make new progress in the field of microrobots. Faced with the challenges of difficult counter-current swimming and insufficient control of micro-medical robots in fluid environments such as blood vessels, the team proposed a unique soft film capsule structure of untethered micro-robots and a control strategy for their wall-mounted precession, which provided new research ideas and solutions for the application of micro-magnetic robots in actual blood vessels. The research results were published in IEEE Transactions on Robotics under the title An On-Wall-Rotating Strategy for Effective Upstream Motion of Untethered Millirobot: Principle, Design, and Demonstration.

In recent years, in order to achieve the goal of minimally invasive treatment of cardiovascular diseases (CVD), scientists have proposed more magnetic untethered robots for blood vessels. However, due to the fluidity of blood, the untethered and untethered microrobots in the blood vessels bear great resistance, which makes it difficult to remain stationary in the free state and more difficult to achieve fixed-point drug administration control against the current. In order to reduce the fluid resistance of the wireless robot in blood vessels, the team proposed a streamlined structure design and an adherent motion strategy that is easier to apply in clinical practice. As shown in Figure 1, the study combined an elliptical arc and a parabolic design to reduce the fluid resistance of the robot by about 58.5% compared to the traditional structure. The adherent motion mode allows the robot to advance at the tube wall with low fluid resistance, which is further reduced by about 30.7% compared to the classic method of advancing in the center of the tube.

Figure 1. Design and optimization of self-vector streamlined capsule robot 

The rotation uniform magnetic field drive mode is limited by the cut-off frequency, which cannot provide sufficient power to realize the high-speed countercurrent motion of the robot, thus limiting the further application of this kind of magnetic drive robot in clinical practice. The adherent rotating magnetic drive strategy was established, and the fluid resistance was overcome by the high-efficiency magnetic rotation “dragging” force generated by the rotating gradient magnetic field at a uniform rotational velocity on the surface of the streamlined robot, so that the robot was subjected to uniform dynamic friction during the movement, so that the wireless robot could be controlled to move forward at a uniform speed in the tube, which solved the problems of the robot motion jamming and instability due to the constant change of static friction when the traditional gradient magnetic field drove the robot, and reached a relative countercurrent velocity of about 143mm/s. To explore the clinical potential of the new approach, the researchers tested the robot’s locomotor ability in pig blood vessels. In this study, a 130 mm section of porcine abdominal aorta was connected to a peristaltic pump to simulate a 2700 mm3/s blood flow environment (Figure 2). The robot successfully passed through the above blood vessels within 26s, which verified the robot’s countercurrent movement ability in real blood vessels, and made the clinical application of intravascular wireless robots possible.

Figure 2. Robot counterflow control system and its in vitro experimental verification. (a) Counterflow control system of the capsule robot;(b) Comparison of control strategies: insufficient gradient force, unstable movement of stuttering, continuous movement at uniform speed;(c) Counterflow of the robot through the abdominal aorta of pigs at a uniform speed. 

The team has made a series of achievements in the fields of micromanipulation and microrobotics, and proposed a paradigm for rapid preparation of robots at the general microscale-the theory of magnetic spray microskeleton empowerment.

The research work was supported by the National Natural Science Foundation of China and the Research Grants Council of Hong Kong, and the Shenzhen Basic Research Special Project. (Source: Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences)

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