title: A microfabricated amperometric moisture sensor.
abstract: We describe a microfabricated moisture sensor with interdigitated Au or Pt electrodes on a silicon substrate. The sensor active area is covered with a spin-coated, baked-on layer of Nafion(R) perfluorosulfonate ionomer of submicron thickness. The sensor responds to moisture with a 10-90% rise time of 50-100 ms and a 90-10% fall time of 20-30 ms, faster than any other presently available sensor. The logarithm of the sensor current is related to the cube root of the moisture level at a given temperature. At 23 degrees C, the sensor easily measures relative humidities as low as 10%. The sensor response at a given absolute humidity level decreases exponentially with increasing temperature. The film is stable up to a temperature of 150 degrees C, permitting elevated temperature moisture measurement. Since sorbed water is actively decomposed electrolytically, the sensors exhibit negligible hysteresis. Response reproducibility of an individual sensor is <1%, that between identically made sensors is <5%, suggesting mass production techniques without individual calibration will be acceptable for all but the most demanding situation.
authors.affiliation: Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA.
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Su
authors.forename: Xiong
authors.initials: X
authors.lastname: Xingguo
authors.forename: Tim
authors.initials: T
authors.lastname: Dallas
authors.forename: Shubhra
authors.initials: S
authors.lastname: Gangopadhyay
authors.forename: Henryk
authors.initials: H
authors.lastname: Temkin
authors.forename: Xuejun
authors.initials: X
authors.lastname: Wang
authors.forename: Richard
authors.initials: R
authors.lastname: Walulu
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Li
authors.forename: Purnendu K
authors.initials: PK
authors.lastname: Dasgupta