Ionic polymer-metal composite (IPMC) sensors

Ionic polymer-metal composites (IPMCs) which are fabricated from an ionomeric membrane, infused with mobile counterions and sandwiched between two thin noble metal electrodes, offer an outstanding capability to transform electrical energy into mechanical energy and vice versa which makes them an appropriate candidate for actuators and sensors. The purpose of this dissertation is to characterize and model IPMCs in sensory mode, develop a new fabrication procedure to improve their flexibility and humidity dependence and take advantage of IPMCs’ exceptional properties in the fabrication of several biomedical instruments to measure some physiological signals such as plantar pressure distribution, blood pulse and tactile forces. For this aim, some IPMC dynamic pressure sensors in bending, compression and shear modes of deformation are designed based on streaming potential hypothesis, fabricated utilizing direct assembly process (DAP) and calibrated in a standard shock pressure tube which provides a broad evaluation of the linearity, sensitivity and reliability of IPMC sensors. Also, to develop a reliable model of applicable sensors that could be used for real-time purposes, three explicit, dynamic, physics-based, rational transfer functions are derived by solving IPMC governing partial differential equation (PDE) in Laplace domain for compression, shear and bending modes. Derived models not only have terms of fundamental material parameters and sensor dimensions but also offer simplicity. Next, to resolve the fragility of electrodes and strong humidity dependence, IPMCs with highly flexible electrodes using sputtered gold thin film and coated with a waterproof acrylic material are fabricated. Conducting some experiments over a period of time shows the improved reliability evidently. In order to develop a self-powered flexible insole, eight circular IPMC pressure sensors are fabricated and fixed on the measuring insole at some specific anatomic areas. The fabricated smart insole is utilized for the real-time plantar pressure distribution analysis of a subject during static stance and gait cycle during walking and running. Produced colormaps based on measured signals are realistic and show a good agreement with those from commercial smart insoles. Finally, IPMCs are developed for monitoring blood pulse wave and as a flexible touch sensor and recorded signals are discussed