Polyurethane Foam Embedded Pressure Sensor Array With 3-D Printed Structure and Thin MEMS Strain Gauge for Car Seat

We have developed a car seat with a pressure sensor array embedded under polyurethane (PU) foam to monitor the posture and driving behavior of the drivers. Each pressure sensor consists of a 5-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m-thick piezoresistive micro-electromechanical systems (MEMSs) strain gauge wired on a 3-D printed parallel-plate cantilever. A cover is attached on top of the cantilever pressure sensor to concentrate the pressure applied through the PU foam, and it is surrounded by a plastic frame of the same height to prevent geometric nonlinear pressure sensor characteristics. To monitor drivers, the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> pressure sensor array is embedded under the PU foam of a car seat. The pressure sensor has a sensitivity range of 0–20 kPa and a determination coefficient of the sensor’s regression line of 0.99, which exhibits high linearity. Our evaluation using the prototype sensor array and a driving simulator demonstrated that driver posture changes and braking behavior could be detected. The sensor array is expected to be applied to smart car seats for automated vehicles in the future.