The effect of van der Waals interaction on the microstructure of EPD deposits: A simulation study

Electrophoretic deposition is a method of choice for generating coatings thanks to its ease of implementation and its ability to produce coatings of relatively large thicknesses in a single-step process. While this process also benefits from a large number of tunable parameters to adapt the coating to each application (such as applied electric field, particle concentration, and viscosity of the suspension), such freedom can make selecting parameters an overwhelming task. A better fundamental understanding of the microscopic phenomena and mechanisms at play during deposition can provide clues for a more efficient design of optimized coatings. Particle-based models, which allow for the systematic simulation of deposit microstructures across various process parameters, are particularly interesting for gaining insights into such systems. Nevertheless, such studies are rare and usually do not include the possibility of self-cohesion between particles, which is crucial for the final structure of the deposit. Here, we use particle-based simulations to study how barrier-limited aggregation influences the deposits formed under different applied electric fields. We show that self-cohesion indeed leads to different microstructures, both in the close vicinity of the substrate and in the bulk of the deposit, and we relate this to the mechanical signature of the deposits. Our results reveal that at high electric fields, the influence of self-cohesion on the resulting microstructures essentially vanishes beyond a critical field strength. This marks the transition from a deposition regime affected by aggregation to a regime largely dominated by volume-exclusion effects.