UBC Theses and Dissertations

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UBC Theses and Dissertations

Shear capable soft sensor technology for the application of pressure ulcer detection in diabetics Velez Lopez, Andres


Diabetic pressure ulcers (DFU) are one of the most common complications related to diabetes, a disease that has become a global epidemic affecting many countries, especially modern and rich ones. The financial cost of treating DFUs this disease is monumental, costing $550 million yearly in Canada alone to treat. the DFUs being one of the costliest outcomes of diabetes, can lead to a sedimentary lifestyle for individuals that could benefit from physical activity to combat their diabetes. There is a need to develop technology that can sense and monitor the condition of feet at this crucial crossroad. This thesis builds on a capacitive sensor developed in our lab that can measure normal and shear stress simultaneously, made from soft, comfortable, and affordable materials which could be implemented into an insole or modified shoe device. The sensor was characterized using modified protocols of existing methodology to establish sensitivity, repeatability, and proper calibration. Overall, the sensor can measure stresses in the prescribed ranges for normal (0-1000 kPa) and shear (0-200 kPa) and is responsive, in the lab as well as real-life testing, to the different time regimes it is being designed for (standing and walking). We show that the sensor is suited well for measuring displacement change in the foot to capture anatomy change in the foot and swelling. While the force characterization has been described, there is still a good amount of work to establish this sensing parameter to coupe with hysteresis and creep (in the worst case 24% of the full scale) present in the deformation of the materials being used. There is a tradeoff to contend with that combines the comfort and softness of the sensor to its ability to withstand high forces and how the modeling of these deformations is accurate and relevant to our clinical considerations. This technology could be a game-changer for the common diabetic and here we lay out the framework to make soft normal and shear stress in-shoe sensors a reality.

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