A new endoscopic microcapsule robot using beetle inspired microfibrillar adhesives

Abstract

The diagnosis of gastrointestinal diseases within the small intestine has been greatly advanced with the introduction of the endoscopic microcapsule in recent years. In an effort to increase its reliability and expand its functionality, a mechanism for stopping and locomoting the capsule within the digestive tract is proposed in this paper. This mechanism, actuated by shape memory alloy wires, utilizes a synthetic microfibrillar adhesive similar to the attachment mechanisms employed by beetles. This fibrillar attachment mechanism is a combination of molecular adhesion caused by van der Waals forces and liquid adhesion caused by capillary forces. The molecular adhesion is enhanced by the presence of microfibers, and the liquid adhesion arises from a secretion from the beetle's footpad. A synthetic version of the beetle's footpad was fabricated from PDMS using a silicon mold. Another version was created from SU-8 using photolithography. Testing revealed decent adhesion with glass and prepared pig intestine in vitro both with a silicone oil to simulate the secretion and without it. A prototype robot with simple polymer adhesive pads for stopping successfully attached and detached inside a flexible vinyl tube. An inch worm locomotion mechanism is proposed and is in the preliminary stages of fabrication and testing