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Light-induced Patterning and Grafting for Slippery Surfaces based on Silane-coated Nanoporous Structures

This protocol describes a light-induced method for fabricating spatially patterned slippery surfaces via digital light processing (DLP) and ...

Changwon National University

Evaporation-induced particle aggregation in drying droplets is of significant importance in the prevention of pathogen transfer due to the possibility of indirect fomite transmission of the infectious virus particles. In this study, particle aggregation was directionally controlled using contact line dynamics (pinned or slipping) and geometrical gradients on microstructured surfaces by the systematic investigation of the evaporation process on sessile droplets and sprayed microdroplets laden with virus-simulant nanoparticles. Using this mechanism, we designed robust particle capture surfaces by significantly inhibiting the contact transfer of particles from fomite surfaces. For the proof-of-concept, interconnected hexagonal and inverted pyramidal microwall were fabricated using ultraviolet-based nanoimprint lithography, which is considered to be a promising scalable manufacturing process. We demonstrated the potentials of an engineered microcavity surface to limit the contact transfer of particle aggregates deposited with the evaporation of microdroplets by 93% for hexagonal microwall and by 96% for inverted pyramidal microwall. The particle capture potential of the interconnected microstructures was also investigated using biological particles, including adenoviruses and lung-derived extracellular vesicles. The findings indicate that the proposed microstructured surfaces can reduce the indirect fomite transmission of highly infectious agents, including norovirus, rotavirus, or SARS-CoV-2, via respiratory droplets.

Microstructured Surfaces for Reducing Chances of Fomite Transmission via Virus-Containing Respiratory Droplets.

The main challenge in preparing a flexible mold stamp using roll-to-roll nanoimprint lithography is to simultaneously increase the imprintable area with a minimized perceptible seam. However, the current methods for stitching multiple small molds to fabricate large-area molds and functional surfaces typically rely on the alignment mark, which inevitably produces a clear alignment mark and stitched seam. In this study, we propose a mark-less alignment by the pattern itself method inspired by moiré technique, which uses the Fourier spectral analysis of moiré patterns formed by superposed identical patterns for alignment. This method is capable of fabricating scalable functional surfaces and imprint molds with quasi-seamless and alignment mark-free patterning. By harnessing the rotational invariance property in the Fourier transform, our approach is confirmed to be a simple and efficient method for extracting the rotational and translational offsets in overlapped periodic or nonperiodic patterns with a minimized stitched region, thereby allowing for the large-area and quasi-seamless fabrication of imprinting molds and functional surfaces, such as liquid-repellent film and micro-optical sheets, that surpass the conventional alignment and stitching limits and potentially expand their application in producing large-area metasurfaces.

Quasi-seamless stitching for large-area micropatterned surfaces enabled by Fourier spectral analysis of moiré patterns.

Owing to their unique structural robustness, interconnected reentrant structures offer multifunctionality for various applications. a scalable multistep roll-to-roll printing method is proposed for fabricating reentrant microcavity surfaces, coined as wetting-induced interconnected reentrant geometry (WING) process. The key to the proposed WING process is a highly reproducible reentrant structure formation controlled by the capillary action during contact between prefabricated microcavity structure and spray-coated ultraviolet-curable resins. It demonstrates the superior liquid repellency of the WING structures, which maintain large contact angles even with low-surface-tension liquids, and their robust capability to retain solid particles and liquids under external forces. In addition, the scalable and continuous fabrication approach addresses the limitations of existing methods, providing a cost-effective and high-throughput solution for creating multifunctional reentrant surfaces for anti-icing, biofouling prevention, and particle capture.

Scalable Multistep Roll-to-Roll Printing of Multifunctional and Robust Reentrant Microcavity Surfaces via a Wetting-Induced Process.

The coffee-ring effect, while harnessed in diverse fields such as biosensing and printing, poses challenges for achieving uniform particle deposition. Controlling this phenomenon is thus essential for precision patterning. This study proposes a novel method to regulate coffee-ring formation by tuning surface wettability via integrated nanoporous and hexagonal microstructures. Four distinct surface types were fabricated using UV nanoimprint lithography: planar, porous planar, hexagonal wall, and porous hexagonal wall. The evaporation behavior of colloidal droplets and subsequent particle aggregation were analyzed through contact angle measurements and confocal microscopy. Results demonstrated that nanoscale porosity significantly increased surface wettability and accelerated evaporation, while the hexagonal pattern enhanced droplet stability and suppressed contact line movement. The porous hexagonal surface, in particular, enabled the formation of connected dual-ring patterns with higher particle accumulation near the contact edge. This synergistic design facilitated both stable evaporation and improved localization of particles. The findings provide a quantitative basis for applying patterned porous surfaces in evaporation-driven platforms, with implications for enhanced sensitivity and reproducibility in surface-enhanced Raman scattering (SERS) and other biosensing applications.

Harnessing Nanoporous Hexagonal Structures to Control the Coffee Ring Effect and Enhance Particle Patterning.

The primary challenge in creating controllable liquid-based materials lies in managing the structural complexities and multiscale interfaces that govern solid, liquid, and gas phase interactions. Current fabrication methods for liquid-infused surfaces lack topological flexibility, limiting them to planar and simple-patterned structures. Conversely, digitally fabricating slippery architectural materials marks a significant shift towards scalable microprinting of complex, topologically slippery designs. This paper introduces a method for digitally fabricating slippery objects with solid-liquid composite interfaces and geometric design freedom. The slippery architecture has been demonstrated through digital printing of photopolymerization-induced multiphase materials and photoinduced grafting, enabling precise control over structural topologies and slippery properties of infused liquids. This versatile platform facilitates the fabrication of structures at multiple scales, enhancing liquid manipulation, droplet evaporation, and biomedical microfluidic chip design. These methods advance beyond conventional techniques, showcasing the potential of architected slippery surfaces with controlled structural scales.

Article	Year
Microstructured Surfaces for Reducing Chances of Fomite Transmission via Virus-Containing Respiratory Droplets. ACS nano\| PubMed ID: 34339604	2021
Quasi-seamless stitching for large-area micropatterned surfaces enabled by Fourier spectral analysis of moiré patterns. Nature communications\| PubMed ID: 37072425	2023
Scalable Multistep Roll-to-Roll Printing of Multifunctional and Robust Reentrant Microcavity Surfaces via a Wetting-Induced Process. Advanced materials (Deerfield Beach, Fla.)\| PubMed ID: 39572924	2025
Harnessing Nanoporous Hexagonal Structures to Control the Coffee Ring Effect and Enhance Particle Patterning. Molecules (Basel, Switzerland)\| PubMed ID: 40807321	2025
Digitally fabricated 3D slippery architectures for multifunctional liquid manipulation. Nature communications\| PubMed ID: 41073399	2025

Woo Young Kim

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