Wearable and flexible pedobarographic insole for continuous pressure monitoring

The feedback of the foot plantar pressure is important in gait and posture application for diagnosing lower limb problems, injury prevention and motor relearning therapy as well as for footwear design and sport biomechanics. Tracking the pressure that acts between the foot and the support surface during everyday locomotor activities is clinically imperative to evaluate the foot function and in particular to assist patients with musculoskeletal and neurological diseases in the development of normal gait functionality. Here a flexible piezoresistive insole with dedicated electronics was developed to measure both the pressure distribution under 64 nodes arranged in the main plantar regions and the mean plantar pressure during walking activity with a sampling frequency of 20 Hz. This study reports on the easy and cost effective approach used to fabricate the conformable insole based on a piezoresistive material composed by copper spiky microparticles dispersed into silicon rubber. The entire insole was prepared in a single step by casting technique, and then completed with a patterned metalized polyimide films as bottom and top electrodes. The insole was then connected to a dedicated electronics to register the dynamic resistance variation under the plantar pressure. A connected personal computer was used for data analysis and visualization through a developed pressure imaging 3D software. The confidence on the obtained data allows the use of such piezoresisitve insole as a therapeutic or rehabilitative tool.