To achieve long-term attachment of capsule endoscopes (CEs) and miniature biosensors in the human gastrointestinal (GI) tract, a tissue attachment mechanism (TAM) was designed, optimized and tested for safety and adhesive capabilities on excised tissue in vitro and in vivo on a live pig model. Six TAMs were tested for their attachment strength in an in vitro attachment tensile experiment in which each TAM was tested on three different proximal intestine tissue samples. The maximum strength and average value are 8.09 N and 4.54 N respectively. The initial attachment damage was tested for 10 min using a sine wave pull force on the TAM with a 0.4 N peak value and 6 s period, which represents typical human intestinal traction force from peristalsis. The in vitro attachment tensile test verified that the tissue was not visually damaged nor perforated by the attachment process. In the in vivo experiment, four TAMs were placed in the intestine of a pig through individual longitudinal enterotomies. X-ray images were taken each hour after the surgery and showed zero migration of the TAMs after 24 h of adhesion. X-ray images taken each day indicated the attachment duration of this mechanism lasted up to 6 days. Post experiment inspection confirmed the attachment did not cause visible damage to tissue. These results confirmed the reliability of the TAM in vivo and demonstrated preliminary feasibility of long-term sensor adhesion to the GI tract.
A wireless medical capsule for measuring the contact pressure between a mobile capsule and the small intestine lumen was developed. Two pressure sensors were used to measure and differentiate the contact pressure and the small intestine intraluminal pressure. After in vitro tests of the capsule, it was surgically placed and tested in the proximal small intestine of a pig model. The capsule successfully gathered and transmitted the pressure data to a receiver outside the body. The measured pressure signals in the animal test were analyzed in the time and frequency domains, and a mathematic model was presented to describe the different factors influencing the contact pressure. A novel signal processing method was applied to isolate the contraction information from the contact pressure. The result shows that the measured contact pressure was 1.08 ± 0.08 kPa, and the small intestine contraction pressure's amplitude and rate were 0.29 ± 0.046 kPa and 12 min-1. Moreover, the amplitudes and rates of pressure from respiration and heartbeat were also estimated. The successful preliminary evaluation of this capsule implies that it could be used in further systematic investigation of small intestine contact pressure on a mobile capsule-shaped bolus.
We have proposed a long-term, noninvasive, nonrestrictive method of delivering and implanting a biosensor within the body via a swallowable implantation capsule robot (ICR). The design and preliminary validation of the ICR's primary subsystem-the sensor deployment system-is discussed and evidence is provided for major design choices. The purpose of the sensor deployment system is to adhere a small biosensor to the mucosa of the intestine long-term, and the modality was inspired by tapeworms and other organisms that employ a strategy of mechanical adhesion to soft tissue via the combined use of hooks or needles and suckers. Testing was performed to refine the design of the suction and needle attachment as well as the sensor ejection features of the ICR. An experiment was conducted in which needle sharpness, needle length, and vacuum volume were varied, and no statistically significant difference was observed. Finally, preliminary testing, coupled with prior work within a live porcine model, provided evidence that this is a promising approach for implanting a biosensor within the small intestine.
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