University of Minnesota M.S.E.E. thesis. August 2016. Major: Electrical Engineering. Advisors: Jing Bai, Debao Zhou. 1 computer file (PDF); viii, 68 pages.Highly flexible skin-like sensors, such as electrical skin (e-skin) sensor for pressure measurement, have the potential to provide quantitative physical contact assessments, when equipped on household and medical devices to benefit human society. One of the promising applications is to monitor the contact pressure of a colonoscope to the colonic wall during a colonoscopy to reduce the possibility of perforation and hemorrhaging.Colon, as the largest intestine, is a long winding tube at end of human's digestive tract. Many disorders affect the colon's ability to work properly, thus the American Cancer Society suggests that citizens over 50 years old should be subject to a colon screen test. However, risks do exist during colonoscopy. A rate of 0.19% perforation occurs in the diagnostic colonoscopy. Many attempts have been made to fabricate highly stretchable electronic devices, but no effort has been made to design or investigate the mechanical behaviors of a tubular-shaped e-skin that meet the need for controlling the risks during colonoscopy. In this project, a high performance three-layer tactile sensor array was designed and fabricated, and a pressure detection system was set up as well. The operating mode was thoroughly investigated and the pressure detection on curved surface, such as a tube was realized. A detailed study about false positive error was performed to improve the sensor’s reliability and accuracy. Based on a tubular-shaped, highly flexible skin-like sensor array we developed, we conducted both modeling and experimental studies on the change of the maximum pressure distribution of a tubular e-skin sensor under various bending conditions with and without external compressive forces. These studies revealed the value of the maximum stress on a tubular shaped e-skin sensor array when bent. The measuring errors due to bending in pressure detection during colonoscopy can be quantified for compensation. Thus, high accuracy diagnose can be achieved. Based on all these work, the pressure detection in the colon-simulator was successfully realized. The results could also be used to address strategies on optimizing the design of tactile sensors for other medical application
