Abstract
A moisture sensor has been reported that detects invisibly small water droplets and distinguishes their particle size with high accuracy and high speed. This sensor uses narrow lines of dissimilar metals as electrodes, arranged with gaps of 0.5 to 10 μm. The working principle for this sensor is that it measures the galvanic current generated when a water droplet forms a bridge-like structure between the electrodes. In addition, the surface of the sensor was controlled by using hydrophilic polymer, GL, and hydrophobic polymer, PMMA. The study of the relationship between the contact angle, projected area of water droplets and current response from the sensor with a modified surface showed that in the case of GL, the contact angle was small (wettability increased) and the average value and distribution of the projected water droplet area and the sensor’s response increased. This enhanced the sensor’s sensitivity. On the other hand, in the case of PMMA, the contact angle was large (wettability decreased), the area of the water droplet and its distribution became small and the accuracy of discriminating the water droplet’s diameter by the sensor enhanced. Therefore, by rendering sensor’s surface hydrophilic and hydrophobic, the sensitivity and accuracy of the sensor could be enhanced.
Highlights
Small water droplets lead to various phenomenon like metal corrosion, glass fogging, molding, etc.Inevitable corrosion causes nuisance and economical losses of several orders in our daily life, such as in pipes used in transportation of underground water, gas and various products, electrical appliances, etc
The current response of the sensor quickly rose at 5 s when water droplets started to appear the sensor surface
In the case of hydrophilic GL, bigger water droplets were observed after the spray and current enhancement was observed due to a larger increase in the number of contacts between the water droplets and the electrodes than for the other two. These results show that by controlling the nature of the sensor surface, we can successfully improve the detection sensitivity and accuracy of the sensor
Summary
Small water droplets lead to various phenomenon like metal corrosion, glass fogging, molding, etc.Inevitable corrosion causes nuisance and economical losses of several orders in our daily life, such as in pipes used in transportation of underground water, gas and various products, electrical appliances, etc. It is very important to detect the number and size of water droplets on the target in order to increase life time and functional evaluation of various products, for economical and safety concerns [1,2,3,4]. The data was collected as time-current measurement device explained in the former section was placed in a chamber. The chamber was data using the software on the PC The output of this device was calibrated by using a semiconductor connected by a hose to a sprayer such as a nebulizer (OMRON/NE-U17, which sprays water droplets evaluation instrument (Agilent Technologies B1500A, Agilent Technologies, Tokyo, Japan). Connected by a on hosethe to asensor sprayer such aswas a nebulizer which air sprays droplets condensation surface induced(OMRON/NE-U17, by introducing humid intowater the chamber. Connected by a on hosethe to asensor sprayer such aswas a nebulizer which air sprays droplets condensation surface induced(OMRON/NE-U17, by introducing humid intowater the chamber. of particle size ~1–8 μm).
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