Untethered shape-changing devices in the gastrointestinal tract

IntroductionAdvances in microfabrication, automation, and computer engineering seek to revolutionize small-scale devices and machines. Emerging trends in medicine point to smart devices that emulate the motility, biosensing abilities, and intelligence of cells and pathogens that inhabit the human body. Two important characteristics of smart medical devices are the capability to be deployed in small conduits, which necessitates being untethered, and the capacity to perform mechanized functions, which requires autonomous shape-changing.Areas coveredWe motivate the need for untethered shape-changing devices in the gastrointestinal tract for drug delivery, diagnosis, and targeted treatment. We survey existing structures and devices designed and utilized across length scales from the macro to the sub-millimeter. These devices range from triggerable pre-stressed thin film microgrippers and spring-loaded devices to shape-memory and differentially swelling structures.Expert opinionRecent studies demonstrate that when fully enabled, tether-free and shape-changing devices, especially at sub-mm scales, could significantly advance the diagnosis and treatment of GI diseases ranging from cancer and inflammatory bowel disease (IBD) to irritable bowel syndrome (IBS) by improving treatment efficacy, reducing costs, and increasing medication compliance. We discuss the challenges and possibilities associated with ensuring safe, reliable, and autonomous operation of these smart devices.