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Miniature humidity micro-sensor based on organic conductive polymer – poly(3,4-ethylenedioxythiophene)

Miniature humidity micro-sensor based on organic conductive polymer – poly(3,4-ethylenedioxythiophene)

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A resistive micro-sensor for humidity sensing based on a conductive polymer material that is deposited electrochemically is presented. The resistor is formed by filling a narrow air gap (12 µm) between two conductor pads with conductive poly(3,4-ethylenedioxythiophene) (PEDOT) polymer, and the resistance of the polymer micro-resistor thus formed is measured to be 41 Ω at a temperature of 20°C. The conductor pads are prepared with a thick layer (20 µm) of nickel using a multi-user microelectromechanical systems (MEMS) process. The area of the entire sensor is around 100×200 µm, making it very compact. The humidity sensor has been characterised within a sealed chamber where the relative humidity is controlled by different saturated salt solutions at a constant temperature of 20°C. The resistance of the sensor varies from 37 to 62 Ω from 22 to 99.9% of relative humidity at room temperature.


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