Acoustic-Assisted Photopolymerization: Revolutionizing Fabrication of Multimaterial Hierarchical Surfaces


Multimaterial hierarchical surfaces refer to complex surfaces composed of multiple materials arranged in a hierarchical manner, incorporating macro, micro, and nanoscale features. These surfaces are designed with precise control over material composition, structure, and surface properties to achieve specifically preprogrammed or dynamically programmable functionalities. Multimaterial hierarchical surfaces are used in surface engineering, tissue engineering and can also be used for drug delivery systems, enabling controlled release of therapeutic agents. Moreover, multimaterial hierarchical surfaces play a crucial role in the development of microfluidic systems used for chemical and biological analysis in the form of lab-on-a-chip Devices.   Furthermore, multimaterial hierarchical surfaces offer advantages in sensor technologies by enabling precise control of surface properties as well as in micro- and nano-manufacturing processes, where precise control over surface features is crucial.

In the realm of biomedicine, drug delivery, lab-on-a-chip devices, water-harvesting, and tissue engineering, the demand for simple, rapid, and cost-effective fabrication methods for complex multimaterial hierarchical surfaces has escalated. Traditional techniques like CNC machining and lithography have limitations, leading researchers to explore alternative methods. Professor Yayue Pan and PhD candidate Ketki Lichade in Pan group from the University of Illinois at Chicago have recently developed a groundbreaking technique called acoustic assembly photopolymerization, which utilizes sound waves to assemble and pattern different materials into intricate structures.

The researchers’ study, published in the peer-reviewed Journal of Advanced Materials Interfaces, introduces acoustic assembly photopolymerization as a revolutionary method for creating multimaterial hierarchical surfaces. This technique involves a setup consisting of a projector, resin vat, piezoelectric plates, a high-speed camera, and a flexible clear window. By activating the piezoelectric plates and projecting digital masks onto the clear window, micro/nano-particles can be moved and assembled, and the particle-polymer suspension can be selectively cured with locally controlled curing depth, resulting in complex surface formations adorned with micro-cones, micro-/nano-pores,  and nano-wrinkles. The photopolymerization process integrated with acoustic assembly is not only simple, rapid, and cost-effective but also environmentally friendly.

The authors delved into the relationship between material properties, process parameters, and particle patterning. They discovered that the breadth of patterns was influenced by particle concentration and acoustic field, while the actuation frequency affected the pattern spacing. Interestingly, a single pattern could have varying particle densities due to a gradient acoustic force. Mechanical tests showed that the patterned surfaces exhibited higher Young’s modulus compared to homogeneous composite surfaces. However, the interaction between particles and the polymer remained an obstacle.

The research team examined the effectiveness of acoustic-assisted photopolymerization in engineering surfaces for hydrodynamic applications. By analyzing the wettability of the manufactured surfaces, they assessed the technique’s efficacy. Contact angle measurements using deionized water and diiodomethane revealed the ability to fine-tune the wettability properties through manipulation of particle concentration and patterning parameters. This precise control of wettability enabled the creation of hydrophobic and hydrophilic regions on the surfaces, facilitating precise liquid manipulation and passive mixing. Furthermore, adjusting acoustic assembly patterns and exposure duration during the photopolymerization process allowed for the preprogramming of surface structure characteristics.

The researchers compared their findings with previous studies utilizing alternative methods for fabricating hierarchical surfaces, such as laser ablation, electrospinning, and soft lithography. The comparison highlighted the promising nature of acoustic-assisted photopolymerization in precisely controlling particle patterning, setting it apart as a powerful technique for fabricating complex hierarchical surfaces.

In summary, Professor Yayue Pan and Ketki Lichade have introduced the groundbreaking technique of acoustic-assisted photopolymerization for fabricating multimaterial hierarchical surfaces with intricate features. The study showcased the technique’s ability to precisely control particle patterning and emphasized its potential for surface engineering in various biomedical applications, including tissue culture, micro-assay chips, detection, chemical reactions, microfluidics, and directional liquid transport. This innovative approach paves the way for simplified, cost-effective, and environmentally friendly fabrication methods, opening doors to advancements in multiple fields. Indeed, the versatility of multimaterial hierarchical surfaces makes them promising for a wide range of applications in biomedicine, microfabrication, energy, and environmental fields. Ongoing research and development in this area continue to explore novel functionalities and applications for these surfaces.

Acoustic-Assisted Photopolymerization: Revolutionizing Fabrication of Multimaterial Hierarchical Surfaces - Advances in Engineering

About the author

Ms. Ketki M. Lichade is a Ph.D. candidate in the Department of Mechanical and Industrial Engineering at the University of Illinois at Chicago.  Under the supervision of Dr. Yayue Pan, Ms. Lichade has been conducting research in the field of photopolymerization-based Additive Manufacturing.  Her research interests are in the intersections of additive manufacturing, surface engineering, and bioinspired design.

About the author

Dr. Yayue Pan holds a Ph.D. degree from the University of Southern California.  Dr. Pan is currently working as an Associate Professor in the Department of Mechanical and Industrial Engineering at the University of Illinois at Chicago (UIC).  Her research focuses on Additive Manufacturing processes for the production of multi-material objects and multi-scale hierarchical structures, with applications in sensing and actuating devices, flexible electronics, energy management and storage, microfluidics, and biomedical devices.


Ketki M. Lichade, Yayue Pan. Fast and Simple Fabrication of Multimaterial Hierarchical Surfaces Using Acoustic Assembly Photopolymerization (AAP). Advanced Materials Interfaces, Volume 10, Issue 1, January 2023, 2201981.

Go To Advanced Materials Interfaces

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