Abstract
The development of humidity sensors with simple transduction principles attracts considerable interest by both scientific researchers and industrial companies. Capacitive humidity sensors, based on polyimide sensing material with different thickness and surface morphologies, are prepared. The surface morphology of the sensing layer is varied from flat to rough and then to nanostructure called nanograss by using an oxygen plasma etch process. The relative humidity (RH) sensor selectively responds to the presence of water vapor by a capacitance change. The interaction between polyimide and water molecules is studied by FTIR spectroscopy. The complete characterization of the prepared capacitive humidity sensor performance is realized using a gas mixing setup and an evaluation kit. A linear correlation is found between the measured capacitance and the RH level in the range of 5 to 85%. The morphology of the humidity sensing layer is revealed as an important parameter influencing the sensor performance. It is proved that a nanograss-like structure is the most effective for detecting RH, due to its rapid response and recovery times, which are comparable to or even better than the ones of commercial polymer-based sensors. This work demonstrates the readiness of the developed RH sensor technology for industrialization.
Highlights
Humidity is defined as the water vapor amount in air
We report detailed insights into the performance of a planar interdigitated about the properties of polyimide based capacitive for use as the sensing layer for relative humidity (RH) are still missing
We have successfully demonstrated that the nanostructure of polyimide to obtain nanograss can be well controlled by adjustment of a series of O2 plasma etch parameters
Summary
Humidity is defined as the water vapor amount in air. It is the most abundant greenhouse gas and an important abiotic factor influencing the human life. Polymeric layersthe asavailability a sensitive of several low-cost relative humidity sensors on theare market, new small and medium layer in combination with interdigitated electrodes intensively studied [7]. Of several relative humidity sensors on the market, small andofmedium size companies polyimide films have been used as sensing layers for humidity sensors [18,20,21,22,23,24,25,26,27], complete reports are looking for mature technology for realizing RH sensors for a wide range of applications. Report detailed the different performance of a and planar interdigitated is worth mentioning that planar IDTs takematerial advantage onlydifferent of the electric field lines penetrating It the transducer coated with polyimide sensing having thickness and morphologies. Worth mentioning that planar IDTs take advantage only of the electric field lines penetrating the polymeric layer (in general the upper half of the transducer)
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