Experimental investigation of interfacial heat and mass transfer in droplets loaded with carbon nanotubes and polystyrene particles on heated substrate

• Evaporation dynamics of CNT/PS nanoparticle-laden droplets were investigated. • Three evaporation modes were identified and linked to temperature and nanoparticle composition. • CNTs enhanced droplet interfacial heat transfer and reduced evaporative cooling effect. • PS particles promoted the multi-ring coffee-ring sedimentation pattern via the stick–slip phenomenon. • Results guide spray cooling design for high-performance electronic devices. This study investigates the evaporation dynamics, wetting behaviour, interfacial heat transfer, and particle deposition patterns of droplets containing carbon nanotube (CNT) and polystyrene (PS) nanoparticles on substrates at various temperatures. The influence of particle composition and substrate conditions on droplet behaviour and final deposit morphology was systematically examined. Droplet wetting analysis revealed that contact angle fluctuations intensify during the final evaporation stage with increasing substrate temperature and PS content, indicating a reduction of interfacial energy barriers. In contrast, higher CNT loading accelerated evaporation owing to its superior thermal conductivity. The evaporation process transitioned through constant contact radius (CCR), mixed, and mixed stick–slip (MSS) modes, with the transitions governed by both particle composition and substrate temperature. Interfacial heat transfer analysis indicated that increased CNT content reduces temperature gradients, promotes uniform interfacial temperature distribution, and mitigates evaporative cooling effects. Particle deposition patterns were strongly dependent on composition and temperature. PS-rich droplets formed multi-ring coffee-stain structures, while CNT-rich droplets exhibited single-ring sedimentary patterns more easily. These findings elucidate the interplay between particle composition and substrate conditions, offering valuable insights for the effective thermal management of high-performance electronics and sensors via spray cooling.