Development of an Untethered Inflatable Capsule Robot for Stricture Dilation - a Preliminary Study

Abstract

Capsule robots have the potential to provide untethered access to the gastrointestinal tract and perform simple tasks that could reduce invasiveness and provide a better alternative method of access than an endoscopy or colonoscopy. Current state-of-the-art for capsule robots already fulfil the need for inspection, but there is a gap that exists between the capabilities of current capsule robots when compared with those of endoscopic surgical robots [1]. For example, strictures occurring throughout the gastrointestinal tract due to inflammation or Crohn’s disease needs a source of pressure to break the strained organ and unblock the stenosis. Additionally, access to the distal parts of the small intestine remains difficult even for Endoscopic Balloon Dilation (EBD). A capsule robot with an actuator that can provide volumetric expansion could fulfil both of these needs, i.e., opening the lumen at a stricture site, anchoring for surgical procedures in difficult-to-access GI areas. This paper presents a capsule robot prototype, of 14 mm diameter and 28 mm length, with a soft internal actuator capable of providing wireless volumetric expansion as seen in Fig. 1. The inflation of the capsule is based on the chemical reaction between NaHCO3 and C6 H8 O7 , which releases carbon dioxide (CO2 ) gas. The inflation of the internal actuator is wirelessly controlled through magnetic induction which generates thermal energy. The capsule also deflates over time due to the CO2 being slowly reabsorbed into water as carbonic acid (H2 CO3 ). Mechanisms that can provide wireless expansion, such as using a wireless electronic module with a pump to inflate and deflate a balloon, using liquid-to-gas transition of chemicals as the source of expansion, or using chemical reactions that release gas as a source of pressure have been previously presented [2]–[4]. However, the method of actuation should not require operating at temperatures that can cause permanent tissue damage [5]. In the current work the generated thermal energy is below limits of hyperthermia [5].The chemicals and the dissolution medium used are all safe for ingestion, making them suitable for gastroin- testinal applications, and the capsule design provides a novel and promising alternative for ballooning operations without using electronics or a battery.