A Biologically Inspired Soft-Bodied Bellows-Driven Stomach Robot: Concept, Design and Validation

Abstract

A human stomach is an organ in the digestive system that breaks down foods by physiological digestion, divided into mechanical and chemical digestion. The mechanical digestion is controlled by peristaltic waves generated over the stomach body. The physiological digestion of a stomach is essential to sustain nutrition and health in humans. Replicating the digestion process in a robot has been essential to provide a test environment as an alternative solution to in-vivo testing, which is difficult in practice. Currently, stomach robots are made of rigid rods and metal cylinders, unrealistic replicas of the human stomach that cannot contract and expand like biological examples. Therefore, a soft-bodied stomach robot can simulate peristaltic waves realistically and perform in-vitro simulations and experiments. Soft robotics is an emerging field that introduces promising engineering methods that replicate biological behaviours. Soft robotics aims to obtain a delicate interaction with their environment and be adaptable in different situations. The invention of this field provides new ideas that differ from the classic engineering strategies. With soft robotics technology, it is possible to translate biological behaviour into an engineering context. Soft robotics introduces potential methods to replicate peristaltic waves and achieve a soft-bodied stomach simulator. This work presents the concept, design, and experimental validation of a stomach robot, modelled from abstracted medical images and constructed from soft materials. An actuation concept is introduced to provide contractions in the robot. The analysis of conventional actuation methods in soft robotics is examined and evaluated with finite element analysis (FEA) software and initial experiments on prototypes. The results lead to novel bellows-driven soft pneumatic actuators (SPA) that provide high linear displacement. This actuator is developed, modelled, and validated to be a suitable actuator for the soft robotic stomach simulator (SoRSS) application. A ring-shaped actuator constructed from multi-SPAs is introduced to convert the linear displacement of SPAs to a contraction profile compared with a stomach segment. From that, multi-rings actuators are formed in a stomach shape to provide a peristaltic wave. SoRSS provides peristaltic waves and antral contractions that are in excellent agreement with the biological stomach. The robot undergoes experimental validation with the aid of videofluoroscopy, a medical device that is usually used for recording esophagus and stomach physiology. The outcomes present the internal contraction, peristaltic waves, and the digestion phases during actuation. Those are compared with other medical studies to prove the workability of SoRSS. This robot satisfies the specification of human stomach geometry and motility.