Design of Magnetic Actuated Capsule Robot for Liquid Sampling

Objective: This study aims to introduce a biopsy capsule robot based on the negative pressure suction principle to achieve liquid sampling in the digestive tract. Methods: The proposed capsule robot is designed with a magnetic spring configuration. By controlling the direction of an external magnetic field, the suction port can be aligned with the target sampling area. The sampling operation can then be achieved by increasing the external field to start the magnetic spring and a negative pressure can be generated to achieve the liquid sampling. Moreover, a locking mechanism is designed to prevent the magnetic spring from retracting, ensuring that the collected liquid is not squeezed out. Results: The capsule robot prototype has dimensions of $\phi$ 16.3 mm × 24.4 mm. Both phantom and in-vitro experiments have been carried out. Results showed that it can sample liquids with viscosities ranging from 0.7 mPa$\cdot$s to 200 mPa$\cdot$s and absorb up to 0.24 ml liquid. Additionally, the sealing of the capsule also meets clinical requirements. Conclusion: The experimental results indicate that the designed capsule robot can satisfy the clinical requirements for liquid sampling within the digestive tract. Significance: This study has designed and developed a micro capsule robot in the digestive tract, which can achieve safe and efficient liquid sampling operations. The proposed robot can benefit the clinical diagnosis of digestive diseases, especially in the small intestine.