ORCA: Origami Capsule Endoscopy System

What it does

ORCA is a controllable capsule endoscope that can be passively propelled anterograde or retrograde through intestinal peristalsis. This solves the problem that current capsule endoscopes are uncontrollable due to size constraints and limited electrical power.

Your inspiration

If there was some mechanism by which peristalsis could passively push the capsule both antegrade and retrograde, then we could control the capsule with very little energy. How can the capsule be pushed back by intestinal peristalsis? I accidentally grabbed a bald cypress leaf and held it in my hand. When the hand is opened, it moves a bit on the palm. The leaf shape of the bald cypress is pinnately compound, with all the upper compound leaves facing in one direction. Due to the triangular arrangement of the compound leaves, when the leaf is squeezed, the entire leaf will deform forward, making the leaf move.

How it works

ORCA is a capsule endoscope with a special origami structure. When the origami structure is folded, the capsule endoscope is propelled forward by intestinal peristalsis. When the origami structure is unfolded, the intestinal peristalsis squeezes the origami structure to drive the capsule endoscope to move in the opposite direction. So it consumes no electricity while moving. Only when the direction of movement needs to be changed, a micro-motor is needed to compress or stretch the origami structure, which consumes very little energy. The patient can swallow ORCA if the entire digestive tract needs to be examined. If only the colon needs to be examined, it can be pushed into the anus with a special syringe to enter the colon. ORCA is linked with external devices via Bluetooth. Doctors can control ORCA, view records and generate diagnostic reports through the app. After the test is complete, ORCA will be expelled from the anus.

Design process

Initially, I wanted to charge the capsule endoscope with the propeller through the peristalsis of the intestines. In this way, the problem of insufficient power of the capsule can be solved. But the capsule requires an additional power-harvesting device, which makes it unwieldy and impractical. One day I stumbled across bald cypress leaves that can move in one direction when squeezed. This made me realize that it is also possible to make the peristaltic push the capsule passively retrograde so that no electricity is required. So I designed a series of different origami structures (3D printed from TPU material with a hardness of 95A) imitating the shape of bald cypress leaves to test their retrograde state under peristalsis. I found that a structure made of a series of triangles connected in series could be pushed back the furthest distance by peristalsis. Performing a finite element analysis of the structure's motion in the peristaltic intestine, I found that the greater the indentation of the peristalsis, the longer the structure retrogradely travelled. The experimental results also verified the conclusion of the simulation. And, when the origami structure is folded up by a fishing line running through it, it is pushed in the other direction by the peristalsis.

How it is different

Currently, the market's digestive tract examination equipment mainly includes a gastroscope, colonoscopy, capsule endoscope, and magnetic control capsule endoscopy system (MCE). Because the small intestine is too long, the total length is about 6 meters, and it is meandering, which makes it difficult for the traditional endoscope to enter. Capsule endoscopy is currently the main method of small intestine examination, but it is too small (About 3 cm long), the battery capacity is limited, there is no propulsion system and cannot be controlled. (Current wireless charging technology makes it difficult to charge the capsule.) This results in a high rate of missed lesions (20%). Nor can do a biopsy, drug delivery and other tasks. MCE can only examine the stomach. ORCA is a controllable capsule endoscope that can examine the small and large intestines, ensuring no missed diagnosis, and providing the possibility for biopsy and drug delivery.

Future plans

1. Design a biopsy device to be mounted on ORCA. 2. Investigate how to make origami structures from degradable materials. It will automatically dissolve within tens of hours after the detection is completed to avoid blocking. 3. Investigating how to charge ORCA through intestinal peristalsis, so that ORCA can work longer and perform more tasks.

Awards

This research was written in an academic paper "Origami Inspired Design for Capsule Endoscope to Retrograde Using Intestinal Peristalsis" which was published in IEEE Robotics and Automation Letters (Volume 7, Issue 2) and at IEEE International Conference On Soft Robotics ( April 4-8, 2022, Edinburgh).