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ABSTRACT
Thermocapillary flow inside a sessile droplet is considered in relation to microsized particles, resembling the environmental dust particles’ removal from the hydrophobic surface. Polycarbonate surface is textured through solution-induced crystallization to generate surfaces with hydrophobic characteristics. The dusts are collected from the local environment and characterized using the analytical tools. Internal fluidity of the droplet is simulated numerically in line with the experimental conditions. An experiment is carried out to measure the velocity of the dust particles using the optical microscopic system. It is found that thermocapillary-induced forces generate counter-rotating cells in the droplet, which depends on the droplet contact angle. The percentage of dust particles removed from the hydrophobic surface into the droplet, due to droplet internal fluidity, increases with the size of the dust particles and it remains almost constant with progressing time. The dust particles follow the streamlines in the circulation cells inside the droplet.
Nomenclature
| Bo | = | Bond number |
| Cp | = | specific heat capacity |
| g | = | gravity |
| Gr | = | Grasshoff number |
| k | = | thermal conductivity |
| Ma | = | Marangoni number |
| Nu | = | Nusselt number |
| p | = | pressure |
| R | = | the wetting radius |
| T | = | temperature |
| t | = | time |
| V | = | velocity |
| ∀ | = | volume of the droplet |
| β | = | thermal expansion coefficient |
| = | temperature derivative of the surface tension | |
| μ | = | dynamic viscosity |
| ν | = | kinematic viscosity |
| ρ | = | density |
| σ | = | surface tension |
| θ | = | contact angle |
| Subscripts | = | |
| D | = | drag |
| eff | = | effective |
| ext | = | external |
| g | = | gravity |
| P | = | particle |
| W | = | water |
| o | = | refer to ambient |
Nomenclature
| Bo | = | Bond number |
| Cp | = | specific heat capacity |
| g | = | gravity |
| Gr | = | Grasshoff number |
| k | = | thermal conductivity |
| Ma | = | Marangoni number |
| Nu | = | Nusselt number |
| p | = | pressure |
| R | = | the wetting radius |
| T | = | temperature |
| t | = | time |
| V | = | velocity |
| ∀ | = | volume of the droplet |
| β | = | thermal expansion coefficient |
| = | temperature derivative of the surface tension | |
| μ | = | dynamic viscosity |
| ν | = | kinematic viscosity |
| ρ | = | density |
| σ | = | surface tension |
| θ | = | contact angle |
| Subscripts | = | |
| D | = | drag |
| eff | = | effective |
| ext | = | external |
| g | = | gravity |
| P | = | particle |
| W | = | water |
| o | = | refer to ambient |