Droplets evaporation is a common phenomenon. It's necessary to keep studying on the evaporation mechanism of multi component droplets

which can promote the development of related industry and technologies

such as pesticide powder spraying

inkjet printing

industrial coating and rapid cooling technology. Based on silicon and PTFE films

the evaporation of water-ethanol mixed liquid drops are studied by using 10%

20% and 30% concentrations of ethanol and pure water. The CCD camera is used to record the change of the appearance of sessile droplets. Then evaporation characteristics of mixed droplets are obtained by analyzing the contact angle and contact radius. It can be seen from the experiment that the evaporation time shortens obviously after adding ethanol. The evaporation of mixed droplets on silicon wafers consists of three evaporation stages as similar as pure water. But the evaporation time of the both first and second stages reduced. And there is a sudden increase in angle at second stage in the experiment of 10% and 20%. On the PTFE film

the pure water droplet has only constant contact radius and mix evaporation stage. When the ethanol content increased to 20%

the first stage turns to be the constant contact angle evaporation mode. As the concentration of ethanol increases

the rate of mix stage is mainly raised. Besides

from the angle of rate and capacity of evaporation

it was found that two liquids may evaporate at the same time. But when the concentration of ethanol is high

the ethanol evaporates faster than pure water. For droplets on the silicon

pure ethanol evaporates in the first stage when the concentration reaches 30%. On the surface of PTFE

the concentration threshold of the ethanol is 20%. Therefore

the concentration of ethanol which can change the order of evaporation varies with the kind of surface. In summary

the addition of ethanol will affect the droplet evaporation mode and the total duration.