Pen-shaped pressure sensor for endoscopic palpation

This paper demonstrates a ballpoint pen like pressure sensor for endoscopic palpation, which can conduct continuous pressure measurement at different locations while a metal ball on the tip rotates. This device is a capacitive-typed pressure sensor which obtains applying force or pressure data from capacitance changes. PDMS polymer is used for the sensor base and liquid metal is used for electrodes to form them on the cylindrical sides. This device has double cylinder and 4 arranged electrodes on its sides for 4 capacitors, surrounding the ball, which can detect the sizes and directions of the applying force vertically to the axis of the ballpoint pen. The device was tested, and verified to be able to detect the pressure and its direction. The experiment was conducted on the fabricated device, in which loads were applied from three different directions while the capacitance of the equipped capacitors were measured. As a result, it was observed that the only capacitance ratios of capacitor which was applied force increased and this device was verified to be able to detect the sizes and directions of applied force in all directions.