Over the past decade, there has been rapidly growing interest in wearable and implantable devices for a wide range of biomedical applications. For many applications involving prolonged contact with the body, devices that are compliant and can comfortably conform to and move with the patient are highly preferred. These flexible substrates (i.e. clothing, bandages, meshes, catheters, etc) can be instrumented to measure various physiological markers, such as temperature, pH, and oxygenation levels, to better inform clinical care. In this dissertation, I will discuss two examples of sensors designed to interact with flexible substrates for clinical monitoring and diagnosis applications.
I will first present the development of an electronic bandage to objectively monitor the progression of wound healing in pressure ulcers and other chronic wounds. Chronic skin wounds affect millions of people each year and take billions of dollars to treat. Pressure ulcers are a type of chronic skin wound that can be especially painful for patients and are tricky to treat because current monitoring solutions are subjective. We have developed an impedance sensing tool to objectively monitor tissue health in wounds. An electrode array is printed onto a flexible, polymeric substrate to form a “smart” bandage. With this sensor array, we can measure impedance of the underlying tissue and extract information on tissue health (i.e. size of wounds and tissue types) to inform the clinical course of treatment.
In the second half of the dissertation, I will discuss methods for instrumenting hernia mesh prosthetics to provide quantitative guidance to surgeons during hernia repair surgeries. Abdominal wall hernias are typically treated by suturing in a surgical mesh to cover and overlap the hernia defect. However, in 10-20% of patients, the hernia repair fails, resulting in recurrence of the hernia. 18% of these recurrences are attributed to mechanical failure of the mesh, often due to unequal stress distribution across the mesh surface resulting in high stress concentrations at the tissue-mesh interface. Strain across the mesh can be used as an indicator for how evenly stress is distributed across the surface of the mesh. I will discuss two methods, based on optical approach and magnetoelastic approaches, for instrumenting the hernia mesh prosthetic to measure the stress distribution during the surgical repair process and the postoperative healing period.