Ingestible sensing capsules are fast emerging as a critical technology that has the ability to greatly impact health, nutrition, and clinical areas. These ingestible devices are noninvasive and hence are very attractive for customers. With widespread access to smart phones connected to the Internet, the data produced by this technology can be readily seen and reviewed online, and accessed by both users and physicians. The outputs provide invaluable information to reveal the state of gut health and disorders as well as the impact of food, medical supplements, and environmental changes on the gastrointestinal tract. One unique feature of such ingestible sensors is that their passage through the gut lumen gives them access to each individual organ of the gastrointestinal tract. Therefore, ingestible sensors offer the ability to gather images and monitor luminal fluid and the contents of each gut segment including electrolytes, enzymes, metabolites, hormones, and the microbial communities. As such, an incredible wealth of knowledge regarding the functionality and state of health of individuals through key gut biomarkers can be obtained. This Review presents an overview of the gut structure and discusses current and emerging digestible technologies. The text is an effort to provide a comprehensive overview of ingestible sensing capsules, from both a body physiology point of view as well as a technological view, and to detail the potential information that they can generate.

Recent advancements and major breakthroughs in machine learning (ML) technologies in the past decade have made it possible to collect, analyze, and interpret an unprecedented amount of sensory information. A new era for “smart” sensor systems is emerging that changes the way that conventional sensor systems are used to understand the world. Smart sensor systems have taken advantage of classic and emerging ML algorithms and modern computer hardware to create sophisticated “smart” models that are tailored specifically for sensing applications and fusing diverse sensing modalities to gain a more holistic appreciation of the system being monitored. Herein, a review of the recent sensing applications, which harness ML enabled smart sensor systems, is presented. First well‐known ML algorithms implemented in smart sensor systems for practical sensing applications are discussed. Subsequent sections summarize the practical sensing applications under two major categories: physical and chemical sensing and visual imaging sensing describing how the sensor technologies are coupled with ML “smart” models and how these systems achieve practical benefits. Finally, an outlook on the current trajectory and challenges that will be faced by future smart sensing systems and the opportunities that may be unlocked is provided.

Summary: Background: Intestinal gases are currently used for the diagnosis of disorders including small intestinal bacterial overgrowth and carbohydrate malabsorption.Aim: To compare the performance of measuring hydrogen production within the gut directly with the telemetric gas‐sensing capsule with that of indirect measurement through breath testing.Methods: Using standard breath testing protocols, the capsules and breath tests were simultaneously evaluated in a single‐blinded trial in 12 healthy subjects. Eight received a single dose of 1.25‐40 g inulin and four 20 or 40 g glucose. Safety and reliability of the capsules were also assessed.Results: There were no reported adverse events. All capsules were retrieved and operated without failure. Capsule measurements were in agreement with breath test measurements in magnitude but not in timing; minimal hydrogen production was observed after glucose ingestion and capsule measurements correlated with breath hydrogen after ingestion of 40 g inulin. A dose‐dependent increase in concentration of hydrogen was observed from the capsule following ingestion of inulin as low as 1.25 g compared with >10 g for breath measurements. Specifically, the capsule measured >3000 times higher concentrations of hydrogen compared to breath tests, resulting in a signal‐to‐noise ratio of 23.4 for the capsule compared to 4.2 for the breath test.Conclusions: The capsule showed high sensitivity and signal‐to‐noise ratio in measuring luminal hydrogen concentrations, provided information on the site of intestinal gas production, and demonstrated safety and reliability. The capsule has potential for improving diagnostic precision for disorders such as small intestinal bacterial overgrowth.

Gastroenterologists are still unable to differentiate between some of the most ordinary disorders of the gut and consequently patients are misdiagnosed. We have developed a swallowable gas sensor capsule for addressing this. The gases of the gut are the by-product of the fermentation processes during digestion, affected by the gut state and can consequently provide the needed information regarding the health of the gut. Here we present the first study on gas sensor capsules for revealing the effect of a medical supplement in an animal (pig) model. We characterise the real-time alterations of gastric-gas in response to environmental heat-stress and dietary cinnamon and use the gas profiles for understanding the bio-physiological changes. Under no heat-stress, feeding increases gastric CO₂ concentration, while dietary cinnamon reduces it due to decrease in gastric acid and pepsin secretion. Alternatively, heat-stress leads to hyperventilation in pigs, which reduces CO₂ concentration and with the cinnamon treatment, CO₂ diminishes even more, resulting in health improvement outcomes. Overall, a good repeatability in gas profiles is also observed. The model demonstrates the strong potential of real-time gas profiler in providing new physiological information that will impact understanding of therapeutics, presenting a highly reliable device for monitoring/diagnostics of gastrointestinal disorders.