GOALI: Controlled Coating via Charged Droplet Impact and Deposition on Dielectric and Conducting Surfaces

Many products used by consumers and industry are coated with layers of materials to prevent corrosion or to provide specialized surface properties. A common way to apply a coating is to spray a liquid onto the surface. The effectiveness and resilience of the coating often depends on intricate details of how the liquid drops that impact the surface bounce, splash, and spread over the surface to form the coating. Despite decades of research and practice, the fundamentals of coating processes, especially on products and machines with complex shapes, are not fully understood. This GOALI project is a joint effort between the University of Illinois - Chicago (UIC) and the Spraying Systems Company to conduct experiments and develop numerical simulations that will determine whether coating processes can be improved by applying an electric field to control details of drop dynamics as the drops impact the surface. The results of fundamental studies conducted at UIC will be used to develop spraying protocols that will be tested at Spraying Systems under industrially relevant conditions. The research team at UIC and representatives from Spraying Systems will also conduct a series of outreach activities to engage students at all academic levels, especially those from underrepresented groups, in the research and related demonstrations. The goal of this GOALI project is to investigate drop dynamics in the presence of an electric field to manipulate spray coating processes. The project will focus on droplet impact, deposition, and spreading on substrates attached to electrodes that generate an electric field. Experiments will be conducted to analyze droplet impact and spreading on dielectric and conducting surfaces to evaluate the droplet's shape and spreading difference. The influence of the morphology of the surface on droplet processes will be evaluated. Phase-field modeling of droplet impact onto dielectric and conducting surfaces will be carried out, using ab initio density function theory calculations to obtain surface binding energies. The results will be used to develops spraying protocols that will be tested in practice at Spraying Systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.