UBC Theses and Dissertations

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UBC Theses and Dissertations

A soft flexible and stretchable pressure sensor array designed to warn of pressure ulcer formation Wyss, Justin Kian Ming


A pressure ulcer, also commonly referred to as a pressure injury or bedsore, is a localized injury or damage to the skin and/or underlying soft tissue, usually over bony prominences, due to prolonged pressure that is sufficient enough to impair blood supply. It is a wound that can disrupt an individual’s life abruptly, affecting not only the person’s physical and mental wellbeing, but also impacting the healthcare system significantly. Most susceptible to the development of a pressure ulcer are individuals confined to beds and/or wheelchairs. In the spinal cord injury (SCI) community, pressure ulcers remain one of the most prevalent and costly preventable secondary complications. There is a need for methods and/or devices that can reduce the incidences or even prevent the formation of such wounds, especially in bedridden patients and wheelchair users. We propose a soft, flexible, and stretchable capacitive pressure sensor array, made out of low-cost materials. It is scalable in size, robust and capable of measuring pressure in the desired range (0 – 200 mmHg) over extended periods of time (>12h) with low repeatability error (0.5%), hysteresis (0.57%), and non-linearity error (0.52%), while fully conforming around various contours (e.g. wheelchair cushions). The pressure readings are displayed on a generated pressure heatmap with the data being wirelessly transmitted to mobile devices (e.g. laptop, smartphone, tablet). A first iteration alert system design enables the sensor to be implemented for potential pressure ulcer prevention, warning the users and healthcare professionals prior to a formation. The working principle of the sensor is based on the well-established capacitance sensing technology, where the relative position of two electrodes is changed by applied force. The sensor array is made of soft, rubbery material and the dielectric contains air to enable relatively large deformations. Further work is required to improve the life-span of the sensor before it is ready to be tested with patients.

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