Pressure level sensor using a conductive diaphragm and microswitch arrays

• We proposed a contact-type pressure level sensor using ITO resistor with diaphragm.
• The change of pressure level can be detected from the ITO's change in resistance.
• A high sensitivity of 1.68 V/V MPa was achieved by the contact-type pressure sensor.
• Extra signal amplification or temperature compensation circuits are not required.

This paper describes a contact-type pressure level sensor, using an indium-tin-oxide (ITO) resistor integrated with an array of Au electrodes. The pressure level sensor consists of a silicon diaphragm with a conducting layer and Pyrex glass with the ITO resistor. The Au electrode arrays with different pitch distance were formed on the ITO resistor by a lift-off process. The conducting diaphragm was deformed with the increase of applied pressure, and the electrode located at the middle of the ITO resistor made contact with the diaphragm at a certain level of pressure. The number of Au electrodes in contact with the diaphragm increased with the additional increase of pressure. This caused a decrease of ITO resistance, which was proportional to the total numbers of electrodes contacted to the conducting diaphragm. The pitch distance between the Au electrodes was optimized by a FEM simulation, which made the sensor output value linear. The fabricated pressure level sensor was successfully evaluated with a simple electrical circuit, and showed a high sensitivity of 1.68 V/V MPa in the dynamic range of 0.5–5 bar.