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Laboratoire ML -UniversitC Bordeaux I -351 cows de la LibCration -33405 Talence Cedex, France -Tel+33 (0)5 56 84 65 40, Fax +33 (0)5 56 37 15 45, Absrrucr -Here are presented and compared two capacitive humidity sensors with interdigitated electrodes for a portable clinical application. The first structures are covered by a polyimide sensitive layer and the optimised ones include a BCB sensitive layer and a heating resistor. Humidity measurements results are presented, in particular sensors response time in absorption which are very small (inferior to 500 ms). Then, mechanisms of absorption and adsorption in a polymer layer are described and the two structures are compared. Suitability of optimised sensors for our application is discussed : new structures permit to increase sensitivity and decrease response time. When the structure is maintained at 4OoC by its heater, the response time is 200 ms and the total desorption time is 11 s.

This paper presents and compares two capacitive humidity sensors with interdigitated electrodes for a portable clinical application. A polyimide-sensitive layer covers the first structures and the optimized ones include a benzocyclobutene-sensitive layer and a heating resistor. Humidity measurements results are presented, in particular sensors response time in absorption, which are very small (inferior to 500 ms). Next, mechanisms of absorption and adsorption in a polymer layer are described and the two structures are compared. Suitability of optimized sensors for our application is discussed: new structures allow us to increase sensitivity and decrease response time. When the structure is maintained at 40 degrees C by its heater, the response time is 200 ms and the total desorption time is 11 s.