Summary
UCLA researchers have developed a template-free, roll-to-roll method for creating semi-regular micro-/nano-scale 3D surface textures on viscoelastic polymer coatings by exploiting ribbing instabilities under shear stress. The process enables scalable manufacture of functional textured surfaces without using molds or templates.
Background
Micro- and nano-structured surface interfaces are known to produce desirable functionalities (e.g. superhydrophobicity, self-cleaning, biofouling resistance, radiative cooling, optical effects), but existing fabrication methods often require costly templates or lithographic tools, which limit scalability and raise cost. Biologically inspired materials (e.g. lotus leaf, insect cuticle, shark skin) show how nature employs complex surface geometries; replicating these at scale is challenging. There is a need for manufacturing processes that can produce functional surface textures at large area, low cost, and with adjustable geometry without templates.
Innovation
This invention uses viscoelastic polymer coatings which, when subjected to shear stress during a roll-to-roll coating process, spontaneously form “ribbing” instabilities — semi-regular 3D features—without needing templates. Process parameters (roller speed, gap, shear rate) and behavior of polymer or polymer composite (including nanoparticle additives) allow tuning of texture periodicity (spacing), height, and pattern regularity. Nano-/microstructure dimensions (spacing from ~25 µm to several hundreds of µm) and roughness can be controlled. Materials such as PDMS, polyurethanes, or fluoropolymer nanocomposites (with e.g. silica, TiO₂, CNTs etc.) may be used. The method supports large-area substrates via roll coating and is compatible with multilayer or bilayer systems.
Advantages
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No need for templates or molds, reducing capital cost and simplifying manufacturing.
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Scalable and continuous process (roll-to-roll), suitable for large area production.
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Adjustable geometry (spacing, height) through tuning of shear and composite parameters.
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Supports diverse polymers and nanocomposites, enabling customization of material properties.
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Enables surfaces with functional properties: superhydrophobicity, self-cleaning, anti-biofouling, enhanced radiative cooling, optical or thermal emission tuning.
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Potential to integrate on flexible or curved substrates, or over coatings / films already in use.
Potential Applications
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Exterior surfaces of buildings, roofs, or facades for passive daytime cooling.
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Self-cleaning and anti-biofouling coatings (e.g. marine, infrastructure, solar panels).
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Hydrophobic / water-repellent surfaces (e.g. outdoor gear, textiles, wearable devices).
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Optical or thermal interface coatings—e.g. for enhanced emissivity, radiation shielding surfaces.
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Coatings for sensors or optical components where microstructure enhances light scattering or reduces glare.
Patent
US 2023/0302489 A1 — Template-free method for manufacturing of semi-regular functional micro-structured interfaces in viscoelastic materials
Priority Date: March 23, 2022; Publication Date: September 28, 2023.
Template-free method for manufacturing of semi-regular functional micro-structured interfaces in viscoelastic materials (US20230302489A1)