Capsule robot for gut microbiota sampling using shape memory alloy spring

Abstract

Background: Human gut microbiota can provide lifelong health information and even influence mood and behaviour. We currently lack the tools to obtain a microbial sample, directly from the small intestine, without contamination. Methods: Shape memory alloy springs are used in concentric configuration to develop an axial actuator. A novel design of sampling mechanism is fabricated for collecting the sample from the gut. Storage chamber (500 µl) is used to protect the sample from downstream contamination. Results: The developed actuator occupies a small space (5 � Ø5.75 mm) and produces sufficient output force (1.75 N) to operate the sampling mechanism. A noninvasive capsule robot was tested ex vivo on the animal intestine, and it captured an average of 134 µl content which was sufficient for microbiome assessment. Conclusions: Laboratory testing revealed that the collected sample had an amino acid signature indicative of microbiota, mucus and digesta, which provided a proof of concept for the proposed design. K E Y W O R D S capsule robot, GI tract, gut microbiota, intestine, micro robot 1 | INTRODUCTION A significant population of microorganisms (bacteria, archaea and fungi) live inside the gastrointestinal (GI) tract, play a major role in fibre fermentation and the synthesis of short-chain fatty acids, and some nutrients (e.g., vitamins), and are collectively known as microbiota. 1 Human intestinal microbiota consist of 10 13-10 14 microorganisms which can act as biomarkers. 2 The microbiota, present in the GI tract, contain lifelong information on the health of an individual and can assist in early diagnosis of diseases such as cancer, diabetes and obesity. 3-5 Several researchers believe that analysis of microbiota could be helpful in predicting obesity, diabetes and inflammatory bowel disease. 3-6 Microbiota can also help to study the relationship or interaction between nutrition and human health. 3 Given the significance of gut microbiota, it is critical to explore its ecology. Microbiota colonise the mucous layer which covers the columnar epithelium of the GI tract and the digesta within the intestinal lumen. 7 The population of microorganisms (microbiota) inside the intestine has been studied using various methods. The most common samples used as a proxy for intestinal microbiota are fecal samples; however, they do not categorise spatial inhabitants, and it is not possible to localise them. Similarly, they lack temporal information and cannot reciprocate real-time gut environment as they are examined after travelling through the entire GI tract, which exposes the sample to contamination. 8 Some efforts have been made in obtaining samples from the human gut with biopsy; however, it is a tethered method which largely restricts its use to the large intestine. 9,10 Furthermore, tethered methods involve a high risk of gut perforation, bleeding and require sedation, and the procedure is also invasive and unpleasant for a patient in terms of comfort. 10 Most importantly, the sample obtained by biopsy is a tissue s...

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“…The frictional forces are further elaborated in (2), where µ is the coefficient of friction, F s is the normal force on the sampler, F s is the force due to the deformation of the intestine, δ is the coefficient of viscosity, N v is the radial stress on the sampler and v is the velocity of sampler. These forces are elaborated in our previous work, and overall frictional forces can be considered as 200mN [35].…”

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