Magnetically actuated soft capsule endoscopes

Current medical technologies are developing toward minimally invasive diagnosis and therapy. Wireless capsule endoscopy (WCE) to reduce pain, discomfort and side effects of patients is one of the state-of-the-art medical technologies to represent this trend. However, due to the lack of mobility, currently, the clinical application of WCE is limited to passive monitoring of the gastrointestinal tract. In this motivation, various kinds of capsule robots for next generation of capsule endoscopy are under development now.;In this thesis, an untethered soft capsule robot, called Magnetically Actuated Soft Capsule Endoscope (MASCE), for minimally invasive medical operations inside the stomach is proposed. MASCE is inspired by two emerging robotics concepts: magnetic micro-robotics and soft robotics. MASCE is manipulated by the magnetic interaction between its internal magnets and an external permanent magnet. Because MASCE's body is made of a soft elastomer, the underactuated MASCE is deformed and recovered to minimize the tissue stress during magnetic manipulation. The important point is magnetically controlled shape deformation and recovery. MASCE is designed to be axially contracted and relaxed by the external magnetic field and this axial compression can be used for one extra degree of freedom motion for medical procedures.;The first half part of this thesis introduces three major topics of magnetic micro-robotics: magnetic manipulation, localization and mapping of the workspace. First, MASCE moves on the bottom surface of a water-filled stomach using rolling motion. This rolling-based surface locomotion is induced by rotating motion of the external permanent magnet. Because this manipulation strategy is based on the symmetrical orientation and locomotion between the external magnet and MASCE, the tracking error between them can be minimized. Second, MASCE is localized in a 3-D space using its axial compression and relaxation. The developed localization method uses an internal hall-effect sensor. Based on the measured magnetic field, the direction of MASCE from EPM is estimated in the coaxial alignment stage. The distance between them is estimated in the shape deformation and the shape recovery stages. The developed 3-D localization method employs the state of the soft capsule robot, which is new in magnetic micro-robotics. Finally, using the localized positions of MASCE, the rough geometry of the local tissue surface is reconstructed where MASCE is manipulated. The position difference of MASCE between the shape deformation stage and the shape recovery stage gives a rough estimate of the tissue compliance. Based on the estimated tissue compliance, the deformation of the tissue surface is compensated. Finally, the deformation-compensated 3-D map is reconstructed for path planning of MASCE.;The latter part of this thesis focuses on clinical applications of the magnetically controlled axial deformation of MASCE. The first is localized drug delivery. MASCE has an elastomer-bodied drug chamber between two internal magnets. The polymeric drug is locally released around diseased tissues by the squeezing force of two internal magnets. The released drug is made of a cytoprotective agent to protect a gastric ulcer from a gastric acid. Such polymeric coating could guide a self-healing process of the gastric tissue until the balance between the gastric acid secretion and the mucous layer's tissue protection function is recovered. The second application is a biopsy strategy using thermally self-assembled micro-grippers. MASCE distributes a number of micro-grippers around a target position using the strengthened magnetic field. The distributed micro-grippers self-assemble to a closed arrangement at body temperature and grab multiple tissue samples of the target. The closed micro-grippers are collected by a wet adhesive patch, which consists of silicone oil-coated micro-post arrays, at the end of MASCE, thus, gathering the tissue samples. Finally, the collected tissue samples would be analyzed in micro-scopic images. The last application is a semi-implantable medical device. The design of MASCE is modified to have bistability, so that its shape can be reconfigured by the external magnetic field. This magnetically actuated soft capsule implant (MASCI) can perform persistent health monitoring and therapy while staying in the stomach and recover its original shape to be discharged from the stomach after finishing the given tasks.;Various soft capsule robot prototypes are shown to enable the above functions in a synthetic stomach model experiments and in-vitro experiments using fresh porcine stomachs. Such miniature mobile robotic capsule technology would improve patient healthcare by making endoscopy less invasive with new therapeutic and diagnostic functions.