Strain induced graphite/PDMS sensors for biomedical applications

This paper presents the design, fabrication and implementation of novel graphite/PDMS sensors for biomedical applications. The fabrication involves 3-D printed molds which were developed using acrylonitrile thermoplastic polymer as the filament. Graphite and PDMS were used to develop the electrodes and substrate of the sensor patches respectively. The electrodes were patterned in an interdigitated manner with the casting of graphite powder on the 3-D printed molds. The operating principle of the sensor patches is described along with the COMSOL simulation result which depicts the electric field density distribution between the two groups of electrode fingers of opposite polarity under an applied stress. The characterization and experimentation of sensor patches were done by analyzing the changes in their complex conductivities at different operating conditions. The highest bending radius of curvature achieved by the developed sensor patches is 6 mm. The sensor patches were then employed for strain-sensing purposes by attaching them on different parts of the body like finger, elbow, neck and knee. Strain sensing was successfully done based on the bending of the different joints on which the sensor patches were attached. The promising results shown by the sensor patches increase the chances of utilizing them in future in the biomedical world.