Periodic Line-Patterned Particle-Polymer Composite Surface Structures Fabricated by Acoustic Assembly Photopolymerization (AAP)
Authors: Chen Yinong , Pan Yayue 
Published: August 2024

Abstract
There is an increasing demand in various industrial and scientific fields for engineered surfaces with autonomous functionality. These advanced surfaces, designed with specific topographical features, offer superior performance and a broader range of functions compared to surfaces with random roughness. In particular, there is a growing interest in surfaces characterized by periodic patterns. Periodic patterning not only simplifies the design process but also enhances controllability of structural features. For instance, anisotropic periodic patterns such as line arrangements enable directional influence over structural and performance characteristics. Furthermore, periodic patterns enhance the scalability of manufacturing processes. Upon refined fabrication strategy for a single period, it can be efficiently scaled up, resulting in economic benefits and consistency in surface quality. The incorporation of different materials in surface fabrication is another strategy to achieve advanced functionalities. By embedding function-specific materials, objects gain improved mechanical properties, like tensile strength, impact resistance, and physical attributes such as hydrophobicity, electrical insulation, and magnetic responsiveness. Our study utilizes Acoustic Assembly Photopolymerization (AAP), a simple, sustainable, and fast technique that can fabricate structured films with periodic patterns. AAP distinguishes itself with its environmentally friendly characteristics and rapid manufacturing speed for fabricating complex particle-polymer composite films. The AAP-fabricated films are characterized with spatially varying particle-polymer composition along with periodic surface structure. Specifically, this study focuses on the periodic line-patterned particle-polymer composite surface structures fabricated via AAP. As one of the basic particle patterns created by acoustic patterning, the periodic line pattern not only provides directional structure and properties for the fabricated surfaces but also establishes a platform for exploring more complex surface structure designs. The AAP process employs an external acoustic field to position particles into distinct microscale patterns. Upon photopolymerization, films with the periodic line-patterned particle-polymer composite surface structures could be fabricated. Grounded in acoustic assembly physics and curing dynamics, physics-based models were developed in this paper to explore the relationship between AAP process parameters and the periodic line-patterned composite surface architectures fabricated by AAP. By analyzing the acoustic radiation forces and Stokes drag forces acting on particles within an acoustic field, the particle distribution in the particle-polymer suspension is modeled. Subsequently, a curing model that considers particle distribution and exposure time has been established. The models enable the prediction of architecture variables, including the dimensions of ridges and grooves, and the outer contour of the ridge regions. Experimental results have validated the effectiveness of the AAP process and the accuracy of the proposed models for predicting the AAP-fabricated periodic line-patterned surface structures.