Biomechanics of a Vibro-Impact Capsule Robot Self-Propelling in the Lower Gastrointestinal Tract

Abstract

Gastrointestinal (GI) diseases cause enormous human suffering and economic burden every year. In particular, bowel cancer has become the second leading cause of cancer-related deaths worldwide. Before capsule endoscopy was introduced, traditional endoscopic diagnostic techniques, including upper and lower GI endoscopies, had been the cornerstone of diagnosing GI diseases. However, the small intestine, within the lower GI tract, is an anatomical site previously considered inaccessible to clinicians. Since its introduction into clinical practice two decades ago, capsule endoscopy has been aimed at becoming the primary modality for examining the surface lining of the lower GI tract due to its painless, wireless, sedative-free, safe, and rapid procedure. Further, the research and development of the self-propelled capsule robot enable the movement of the capsule to be precisely controlled, rather than passively relying on natural GI peristalsis. This greatly improves the accuracy of diagnosis and can further develop its functionality, such as biopsy, drug delivery, cancer detection, minimally invasive surgery and targeted therapy. The vibro-impact capsule robot is controlled by driving internal magnets with an external alternating electromagnetic field to generate vibration and impact on the capsule body, and is feasible clinically due to its smooth surface (without external auxiliary accessories). In practice, the biomechanical study of movement of the vibro-impact capsule robot in the GI tract is a prerequisite, as the capsule movement needs to overcome resistance while avoiding secondary damage to the intestine caused by excessive driving force. This thesis aims to study the interaction between the vibro-impact capsule robot and the intestine, including the contact pressure, friction force and dynamic behaviour of the capsule, by means of mathematical modelling, finite element (FE) simulation and experimental investigation. Considering intestinal complex anatomy and mobility, capsule-intestine contact was performed under different contact conditions. As computer technology has become more powerful, modelling tools based on the FE method have been used to analyse the dynamics of capsule endoscopes in complex intestinal environments, which is difficult to do with ordinary mathematical equations. In addition, the study of the capsule-tumour contact relationship provides the potential for the capsule robot to diagnose early cancer through sensing rather than vision. Results of this thesis will be useful for prototype and control system design of the next generation capsule robot.