Droplet evaporation on flexible substrates using a lattice Boltzmann, material point, and immersed boundary method coupled model

Efficient thermal management is critical for the reliability of flexible electronic devices, where droplet evaporation on heated surfaces provides a promising cooling strategy. However, when the substrate is flexible, droplet spreading and evaporation are strongly affected by coupled fluid–structure–thermal interactions arising from substrate deformation, making the underlying mechanisms difficult to resolve. To investigate droplet impact on superheated flexible substrates, a lattice Boltzmann, material point, and immersed boundary method coupled model is developed. Lattice Boltzmann method resolves fluid dynamics involving multiple phases and phase transitions, while material point method captures the deformation and thermal response of the flexible substrate. Immersed boundary method enables momentum and heat coupling between the fluid and solid domains. Furthermore, the diffuse interface immersed boundary wetting scheme is innovatively incorporated to capture droplet wetting dynamics on deformable substrates. Using this coupled algorithm, the influences of substrate elasticity, wettability, and superheating temperature are examined. The results show that softer substrates generate stronger wetting ridge deformation and interfacial oscillations, which suppress internal heat transfer and prolong droplet evaporation. Increasing substrate wettability enhances droplet spreading, while higher superheating temperature intensifies vapor generation. Quantitatively, increasing the elastic modulus from 1.288 to 128.8 MPa reduces the droplet lifetime by 27.1%, whereas decreasing the equilibrium contact angle from 90° to 30° shortens the lifetime by 23.67%. These findings provide new insights into droplet evaporation on deformable substrates and offer guidance on thermal regulation strategies for flexible electronics.