Evaporation kinetics of laser modulated pendant nanocolloidal droplet

Abstract

While a body of literature is there on the sessile evaporation of droplets, literatures dealing with the evaporation characteristics of the complex nanocolloidal systems are scarce. While a few literatures deals with the evaporation kinetics of such colloids the effect of the external optical irradiation in modulating the evaporation kinetics are not talked in literature. The present study analyses the effect of laser as an external optical source in modulating the evaporation characteristics of the hanging nanocolloidal droplets which are free from surface effects so as to capture the physics behind the interfacial mass transport. The current study analyses the effect of the power of laser, nature and concentration of the particle on evaporation rate of such complex colloidal systems. Evidence of internal circulation was observed with PIV technique in colloidal systems together with volumetric heat generation which can be attributed to be the causes behind the enhanced evaporation rate. Theoretical analysis of the evaporation rate with the classical mass transfer model for droplets falls short in predicting the evaporation rate in colloidal systems. Marangoni and Rayleigh numbers are calculated from the theoretical examination and are found to induce the circulation in such systems.