Edible Origami for Intestinal-Retentive Medical Devices

 Medical devices that operate within the gastrointestinal tract (GIT) are exciting new platforms that could support new concepts for therapeutics and diagnostics. Orally ingested “pill-shaped” devices transit the GIT within 12-24 hours while intestinal-retentive devices (IRDs) could offer sustained residence to enable longitudinal monitoring, extend drug delivery timelines, or support new concepts such as internal wound-healing. 

In this work, we take inspiration from the ancient art of origami and the world of self-expanding cardiovascular stents to create a self-deployable IRD composed of edible, auxetic origami. Autonomous actuation of this pill-sized, tubular structure is achieved through the development of a unique gelatin-based bioplastic tuned to fold without fracture and unfold at elevated humidities. The relaxation and deployment characteristics of individual origami folds were studied using an environmental chamber in combination with mechanical testing and time-lapse photography. A series of precise molds were fabricated using SLA printing and CO2 laser processing to transform sheets of the bioplastic material into cm -scale origami arrays containing 100+ folds. Folded tubes of varying cell densities were characterized in-situ via normal force measurements to understand the prospective anchoring force of respective designs. The effective Poisson’s ratio of the pill-sized origami structures were measured to identify trends in volumetric packing efficiency and validate the tube’s ability to anchor in both the small bowel (2.5 cm) and colon (4 cm). Ex-vivo friction testing in porcine intestine explants validated origami deployment in a realistic tissue environment and illustrated the contribution of active deployment towards IRD anchoring. 

In parallel, pilot experiments were conducted on an electrode pill capsule designed for stimulation of the gastrointestinal nervous system. Non-invasive neuromodulation via the gut-brain axis is an appropriate application of the deployable auxetic origami substrate given the substantial benefit of increased surface area on nerve recruitment capabilities. The future fusion of these two technologies may offer innovative therapeutic interventions in the treatment of depression, weight loss, IBS, and more.