Zero Hysteresis, High Sensitivity and Fast Response of Two RH Sensors based on CNO: Polymer Nanocomposites

This paper presents fabrication and characterization of two types of Relative Humidity (RH) sensors. Sensing materials, containing Carbon Nano Onion CNO (as conductive filler), mixed with PolyVinyl Pyrrolidone (PVP) or PolyVinyl Alcohol (PVA) (as polymeric matrix) are deposited by drop casting on an Inter Digital Transducer (IDT/1mil or IDT/2mil). This test vehicle using a metallic configurated IDT on Polyimide (PI) substrate, has the finger/space dimension equal to 25 μm /50 μm and a sensitive area of 4mm x 4mm. IDT/1mil & IDT/2mil were photolithographically configurated on Cr/Au metalized in vacuum on PI substrate. Optimisation of sensitive nanomaterial preparation and dispersibility enhancing by using IPA have been done. Sonication in two steps: first (for dissolving and mixing the polymer) and second (for breaking the CNOs aggregates) was applied. The result of doubled sonication time was notable, leading to zero hysteresis of RH sensors characteristic. The enhanced electrical characteristics of the two types of RH sensors were analysed and discussed in detail.