Design and testing of a novel gastrointestinal microrobot

In order to improve the reliability, safety and whole digestive applicability of the gastrointestinal microrobot (GMR), a novel inchworm-like GMR is proposed in this paper. The expanding mechanism of the robot adopts an overlapping expanding arm structure. This structure increases the variable diameter ratio (ratio of fully expanded diameter to fully folded diameter) of the robot to 3.3, making the robot more applicable to the intestines in various parts of the human body. The mechanical model of the expanding arm is established, and the expanding force at different expanding radii is obtained. And then the expanding force is tested by a force test platform. The force test results: the maximum expanding force is 6.5 N, and the minimum expanding force is 1.3 N. The trend of the experimental and theoretical values is the same, and the experimental value is less than the theoretical value. A position limiting device based on Hall sensor is designed, which detects whether the mechanism reaches the limit position by non-contact method. This device alleviates the problem of sharp voltage drop caused by motor stall and improves the stability of the control circuit. The results of the Hall-type position limiting device (HPLD) testing show that the working currents of the expanding mechanism and the telescoping mechanism with HPLD are respectively 0.066A and 0.110A, and the robot control circuit works stably. Finally, the robot is tested in the intestine of the living pig, and the safety and reliability of the robot are verified. However, due to the decrease of the efficiency of wireless power transmission in vivo experiments and the change of the position of the receiving coil relative to the transmitting coil, sometimes the power supply is insufficient.