Development of multi-capsule endoscopy locomotion via spring-assisted distance management

Abstract

Gastrointestinal (GI) tract analysis has been revolutionized since the emergence of wireless capsule endoscopy (WCE) in 2000 and has been widely accepted due to its minimally invasive procedures. While conventional gastrointestinal examinations, such as colonoscopy and endoscopy, involve sedation and multiple insertions, capsule endoscopy offers a more compliant alternative for analyzing the GI tract for patients. Traditional wireless capsule endoscopy systems were mainly focused on imaging, which limited their usability in advanced medical procedures like biopsy, drug delivery, and real-time diagnostics. To overcome such drawbacks, the concept of a multi-WCE train was introduced, where instead of one, multiple capsules synchronously operate to enhance diagnostic and therapeutic capabilities. Ensuring the stable connection of the multi-capsule endoscopy was a primary challenge in WCE train procedures, particularly in sharp turns of the intestinal paths. Previous studies have worked on coil-based inductive power systems and magnetic-based remote actuation to support the intercapsule connection. However, these methods have faced drawbacks during complex GI tract paths. This study aims to overcome these challenges by introducing a new capsule configuration with flexible spiral springs and embedded spherical magnets. This system supports a stable connection between capsules during sharp radius of curvatures (ROCs) of the intestinal path. We proposed a system that consists of multiple capsules, each designed with a special spiral spring equipped with a permanent magnet. These springs allow the capsule train to connect firmly during the entire examination, especially in sharp turns of the bowel paths. This approach provides a physical yet adaptable connection mechanism that does not rely on external power sources. The spring's flexible characteristics adapt to the changes in the inter-capsule distance during movement, ensuring the train remains intact during harsh paths. The evaluation of the effectiveness of this approach was conducted by using finite element analysis, beside physical experiments. The COMSOL multiphysics simulations were focused on assessing the mechanical properties of the model, including K-value evaluations of the springs, yield point, stress distribution under the known forces, and displacement of the spiral springs. Three different intestinal models were used to conduct physical experiments to test various capsule-spring configurations: a basic polylactic acid (PLA) phantom, a silicone-coated bowel model with villus-like shape, and a bovine bowel-covered intestinal model for mimicking the realistic scenarios.