Skin is the first point of contact of the human body with the outer environment, and influences the biomechanics of different organ systems in normal and diseased states. Wearable electronics such as fitness tracking equipment, motion sensing devices, and advanced wearables in prosthetics and orthotics are often used to quantify the interaction of the body with the environment during different physical activities, and improve health. These wearable equipment can be bulky and a source of discomfort to the human skin with prolonged wear. To date, very few flexible polymers have been developed which can conduct electricity and be used in wearable devices. In the current work, a novel conductive synthetic skin composite system was developed, which would be indispensable for integration into wearable technologies, and also allow the biomechanical testing of the human skin for different engineering and medical applications. The mechanical behavior of this polymer can be tuned to mimic the human skin from different locations of the body with varying stiffnesses, with a phenomenal degree of accuracy. The composite system is composed of short carbon fibers dispersed in a multi part silicone based matrix material. The volume fraction of the fibers were varied to control the mechanical and electrical properties of the composite. Uniaxial tensile tests were conducted to generate stress versus strain responses of the synthetic skin composites at different fiber volume fractions, and electrical measurements were recorded at different strains. Microscopy was used to understand composite fiber orientations in unstretched and stretched states, and its effects on the electrical conductivity of the material. Additionally, non-linear material characterization models were developed to characterize the composite variants. To the best of our knowledge, such an accurate synthetic skin composite system with tailorable electrical properties has not been developed; making this state of the art in bio mimicking and functionalization of the human skin.
Rectifying memristor bridge circuit realized with human skin
