Submillimeter-Scaled PEDOT:PSS/PPy Piezoresistive Pressure Sensor Array and Its Applications in Biomedicine

Developing a small, smart, and sensitive pressure sensor array is necessary for establishing a comfortable and safe environment in daily life. Herein, the miniaturization effects of $1\times 1$ poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) piezoresistive pressure sensors with a cross-point electrode (CPE) structure have been investigated and found to suffer from response delays owing to the serious current crowding effect. To eliminate the adverse effects caused by the device scaling, polypyrrole (PPy) was blended into PEDOT:PSS to obtain a high piezoresistive sensitivity of 0.58 kPa ⁻¹ and a fast relaxation time of 0.74 s for the miniaturized PEDOT:PSS/PPy piezoresistive pressure sensors with a PPy concentration of 60 ppm. Subsequently, the optimized PEDOT:PSS/PPy composites were implemented to fabricate $3\times 3$ CPE piezoresistive sensor arrays with an electrode size of 0.2 mm, and a readout circuit was designed to instantaneously measure the resistance of each pixel of the sensor arrays under the application of pressure. Using the $3\times 3$ PEDOT:PSS/PPy piezoresistive sensor arrays with a readout circuit, the pressure distribution of the finger pressing and an occlusal pressure monitoring of a molar before and after the dental filling process were successfully demonstrated, suitable for prospective applications in biomedicine.