116 / 2021-04-07 15:43:47

Effect of substrate elasticity on evaporation kinetics and evaporative deposition of aqueous polystyrene nanoparticles droplets

droplet,evaporation,nanoparticle,crack,constant contact radius mode

Evaporation of aqueous polystyrene (PS) nanoparticles droplets on silicon and polydimethylsiloxane (PDMS) surfaces was studied. Experimental results showed that softer PDMS surfaces yielded a longer constant contact radius (CCR) stage, which could be ascribed to surface deformation of PDMS induced by the vertical component of liquid-vapor interfacial tension. Ring­like depositions of nanoparticles with different crack patterns were found on both silicon and PDMS surfaces. In-situ observation of crack formation showed that nanoparticle movement on the silicon surface was impeded, resulting in radial cracks with periodic distribution. In contrast, nanoparticles were shown to move easily on the PDMS surface. This observation indicated the difference in crack patterns on surfaces could be attributed to the friction force between nanoparticles and the substrate. A large friction force between nanoparticles and the substrate prevented cracks from moving, resulting in a radial crack pattern with periodic distribution, while a small friction force produced multiple large cracks.