Multifunctional Flexible Piezoelectrics for Wearable Medical Devices.

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The global market for medical wearable devices will reach $12.1 billion by 2021. In healthcare technologies, intelligent wearable devices provide an added value to diagnosis, treatment, patient monitoring and prevention. Diabetes is one of the most common chronic endocrine conditions that can develop at any stage of life and its incidence is increasing rapidly. According to the International Diabetes Federation, there are currently 415 million people worldwide with diabetes and this number is expected to grow up to 642 million in 2040, with an estimated 55% increase in 25 years.Diabetic peripheral neuropathy is a common complication for people with diabetes, where the loss of sensation caused by nerve damage can make it difficult for people to feel when their foot is at risk of skin breakdown, which can result in foot ulcers forming. These ulcers can fail to heal and become infected over time; around 30% of patients with a diabetic foot ulcer may be at risk of lower limb amputation. Current best practice recommends patients perform daily monitoring of their feet supported by regular physical examination by trained specialists, which is time-consuming.Here we propose the development of a novel self-powered wearable multifunctional sensing device that monitors the patient's posture. Whenever the pressure sensing inserts detect clinically dangerous foot pressure, a light signal and an audio alert are transmitted prompting the device user to offload the pressure from a particular region of their foot.The multifunctional device will be composed of several layers of screen-printed functional ceramic inks on a flexible polymer substrate. A phosphor layer generates electroluminescent (EL) light and a piezoelectric layer generates sound and additionally harvests mechanical energy and convert it into EL light for feedback. A pyroelectric layer harvests thermal energy and converts that to electrical energy. Lead-free ferroelectric materials, such as barium titanate (BT) and potassium sodium niobate (KNN) based ceramics, will be printed and the dielectric, piezo and ferroelectric properties will be characterised. Different phosphors such as ZnS and ZnS:Cu will be fabricated to achieve optimum and uniform light emission. Coupling of the phosphor, piezoelectric and pyroelectric materials will result in a piezo-pyro-electro-luminescence device with simultaneous sound and light emission powered by energy harvesting of the external mechanical and thermal energy.The project is in collaboration with DST Innovations, an expert company in printed electronics for flexible materials. The focus of DST is developing energy-efficient and environmentally safe technologies that can replace those used in today's electronic products. The company has expertise in developing lightweight, low powered and flexible lighting solution for large area lightings and will support the project by offering technical knowledge.The main goals of this PhD project are the following:Formulate and test the printability and performance of lead-free piezoelectric inks (BT-based, KNN) and phosphor inks (ZnS)Formulate and test the conductive inks for optimum electrode structureFabricate multilayer devices using screen printing. Piezoelectric and phosphor layers will be printed individually and in combination, with and without electrodes.Characterise the physical and electromechanical properties using impedance spectroscopy, piezoelectric, pyroelectric, ferroelectric, electroluminescence and surface roughness analysisDevelop and test the self-powered multifunctional wearable piezoelectric device