Direct Fabrication of Micro/Nano-Patterned Surfaces by Vertical-Directional Photofluidization of Azobenzene Materials

Anisotropic movement of azobenzene materials (i.e., azobenzene molecules incorporated in polymer, glass, or supramolecules) has provided significant opportunities for the fabrication of micro/nanoarchitectures. The examples include circular holes, line gaps, ellipsoidal holes, and nanofunnels. However, all of the previous studies have only focused on the lateral directional movement for the structural shaping of azobenzene materials. Herein, we propose structural shaping based on a vertical directional movement of azobenzene materials. To do this, light with oblique incidence, containing normal direction light polarization, was illuminated onto azobenzene materials film contact with patterned elastomeric molds (i.e., PDMS) so that the resulting vertical directional movement of azobenzene materials fills in the cavities of the molds and results in pattern formation. As a result, a range of patterns with sizes of features from micro- to sub-100 nm scale was successfully fabricated in a large area (few cm2), and the structural height was deterministically controlled by simply adjusting irradiation time. In addition to the notable capability of fabricating the single-scale structures, the technique provides a facile way to fabricate complex hierarchical multiscale structures, ensuring its versatility and wide applicability to various applications. As a selected exemplary application of the multiscale structures, a superhydrophobic surface has been successfully demonstrated

Directional Superficial Photofluidization for Deterministic Shaping of Complex 3D Architectures

The fabrication of micro- and nanostructures is one of the cornerstones of current materials science and technology. There is a strong interest in processing methods capable of manufacturing engineered complex structures on a large area. A method that is gaining a growing attention in this context is based on surface reshaping of photosensitive materials, such as certain azobenzene derivatives by way of a process of light-induced mass migration, also described as “athermal photofluidization”. Here, we apply this method to prestructured substrate, converting simple periodic structures initially patterned only in two dimensions into complex-shaped three-dimensional (3D) structures by a single processing step over a large area. The optical variables of the irradiating beam are used to gain unprecedented deterministic control on the resulting 3D architectures. We also provide some initial demonstrations of the potential application of this novel shaping method, including unidirectional wetting surfaces and micro- and nanoscaled fluidic channel manufactured with it

Fabrication of Free-Standing, Self-Aligned, High-Aspect-Ratio Synthetic Ommatidia

Free-standing, self-aligned, high-aspect-ratio (length to cross-section, up to 15.5) waveguides that mimic insects’ ommatidia are fabricated. Self-aligned waveguides under the lenses are created after exposing photoresist SU-8 film through the negative polydimethylsiloxane (PDMS) lens array. Instead of drying from the developer, the waveguides are coated with poly­(vinyl alcohol) and then immersed into a mixture of PDMS precursor and diethyl ether. The slow drying of diethyl ether, followed by curing and peeling off PDMS, allows for the fabrication of free-standing waveguides without collapse. We show that the synthetic ommatidia can confine light and propagate it all the way to the tips

Direct Fabrication of Micro/Nano-Patterned Surfaces by Vertical-Directional Photofluidization of Azobenzene Materials

Anisotropic movement of azobenzene materials (i.e., azobenzene molecules incorporated in polymer, glass, or supramolecules) has provided significant opportunities for the fabrication of micro/nanoarchitectures. The examples include circular holes, line gaps, ellipsoidal holes, and nanofunnels. However, all of the previous studies have only focused on the lateral directional movement for the structural shaping of azobenzene materials. Herein, we propose structural shaping based on a vertical directional movement of azobenzene materials. To do this, light with oblique incidence, containing normal direction light polarization, was illuminated onto azobenzene materials film contact with patterned elastomeric molds (i.e., PDMS) so that the resulting vertical directional movement of azobenzene materials fills in the cavities of the molds and results in pattern formation. As a result, a range of patterns with sizes of features from micro- to sub-100 nm scale was successfully fabricated in a large area (few cm2), and the structural height was deterministically controlled by simply adjusting irradiation time. In addition to the notable capability of fabricating the single-scale structures, the technique provides a facile way to fabricate complex hierarchical multiscale structures, ensuring its versatility and wide applicability to various applications. As a selected exemplary application of the multiscale structures, a superhydrophobic surface has been successfully demonstrated

Flexible, Elastic, and Superhydrophobic/Superoleophilic Adhesive for Reusable and Durable Water/Oil Separation Coating

This study investigates a highly flexible/stretchable and mechanically durable superhydrophobic/superoleophilic coating for efficient oil/water separation and oil absorption. The coating is applied via a simple immersion process using a mixed solution of a biocompatible adhesive (ethyl cyanoacrylate, ECA), a highly stretchable polymer (polycaprolactone, PCL), and superhydrophobic/superoleophilic nanoparticles (fluorine-coated silica nanoparticles, F-SiO2 NPs) in a solvent, followed by solvent evaporation and ECA polymerization. Polymerized ECA (poly-ECA) in the coating material strongly adheres the F-SiO2 NPs to the substrate surface, while PCL bestows the rigid poly-ECA with high flexibility. A coated polyurethane sponge exhibits superhydrophobicity (water contact angle of >150°), while retaining robust mechanical stability and flexibility/elasticity. This provides an efficient means of cleaning oil spills with high selectivity, even after mechanical abrasion (>99% separation efficiency is retained after 120 tape test cycles and 50 rubbing test cycles), with excellent reusability

Direct Fabrication of Micro/Nano-Patterned Surfaces by Vertical-Directional Photofluidization of Azobenzene Materials

Anisotropic movement of azobenzene materials (<i>i</i>.<i>e</i>., azobenzene molecules incorporated in polymer, glass, or supramolecules) has provided significant opportunities for the fabrication of micro/nanoarchitectures. The examples include circular holes, line gaps, ellipsoidal holes, and nanofunnels. However, all of the previous studies have only focused on the lateral directional movement for the structural shaping of azobenzene materials. Herein, we propose structural shaping based on a vertical directional movement of azobenzene materials. To do this, light with oblique incidence, containing normal direction light polarization, was illuminated onto azobenzene materials film contact with patterned elastomeric molds (<i>i</i>.<i>e</i>., PDMS) so that the resulting vertical directional movement of azobenzene materials fills in the cavities of the molds and results in pattern formation. As a result, a range of patterns with sizes of features from micro- to sub-100 nm scale was successfully fabricated in a large area (few cm²), and the structural height was deterministically controlled by simply adjusting irradiation time. In addition to the notable capability of fabricating the single-scale structures, the technique provides a facile way to fabricate complex hierarchical multiscale structures, ensuring its versatility and wide applicability to various applications. As a selected exemplary application of the multiscale structures, a superhydrophobic surface has been successfully demonstrated

Flexible, Elastic, and Superhydrophobic/Superoleophilic Adhesive for Reusable and Durable Water/Oil Separation Coating

This study investigates a highly flexible/stretchable and mechanically durable superhydrophobic/superoleophilic coating for efficient oil/water separation and oil absorption. The coating is applied via a simple immersion process using a mixed solution of a biocompatible adhesive (ethyl cyanoacrylate, ECA), a highly stretchable polymer (polycaprolactone, PCL), and superhydrophobic/superoleophilic nanoparticles (fluorine-coated silica nanoparticles, F-SiO2 NPs) in a solvent, followed by solvent evaporation and ECA polymerization. Polymerized ECA (poly-ECA) in the coating material strongly adheres the F-SiO2 NPs to the substrate surface, while PCL bestows the rigid poly-ECA with high flexibility. A coated polyurethane sponge exhibits superhydrophobicity (water contact angle of >150°), while retaining robust mechanical stability and flexibility/elasticity. This provides an efficient means of cleaning oil spills with high selectivity, even after mechanical abrasion (>99% separation efficiency is retained after 120 tape test cycles and 50 rubbing test cycles), with excellent reusability

Flexible, Elastic, and Superhydrophobic/Superoleophilic Adhesive for Reusable and Durable Water/Oil Separation Coating

This study investigates a highly flexible/stretchable and mechanically durable superhydrophobic/superoleophilic coating for efficient oil/water separation and oil absorption. The coating is applied via a simple immersion process using a mixed solution of a biocompatible adhesive (ethyl cyanoacrylate, ECA), a highly stretchable polymer (polycaprolactone, PCL), and superhydrophobic/superoleophilic nanoparticles (fluorine-coated silica nanoparticles, F-SiO2 NPs) in a solvent, followed by solvent evaporation and ECA polymerization. Polymerized ECA (poly-ECA) in the coating material strongly adheres the F-SiO2 NPs to the substrate surface, while PCL bestows the rigid poly-ECA with high flexibility. A coated polyurethane sponge exhibits superhydrophobicity (water contact angle of >150°), while retaining robust mechanical stability and flexibility/elasticity. This provides an efficient means of cleaning oil spills with high selectivity, even after mechanical abrasion (>99% separation efficiency is retained after 120 tape test cycles and 50 rubbing test cycles), with excellent reusability

Flexible, Elastic, and Superhydrophobic/Superoleophilic Adhesive for Reusable and Durable Water/Oil Separation Coating

This study investigates a highly flexible/stretchable and mechanically durable superhydrophobic/superoleophilic coating for efficient oil/water separation and oil absorption. The coating is applied via a simple immersion process using a mixed solution of a biocompatible adhesive (ethyl cyanoacrylate, ECA), a highly stretchable polymer (polycaprolactone, PCL), and superhydrophobic/superoleophilic nanoparticles (fluorine-coated silica nanoparticles, F-SiO2 NPs) in a solvent, followed by solvent evaporation and ECA polymerization. Polymerized ECA (poly-ECA) in the coating material strongly adheres the F-SiO2 NPs to the substrate surface, while PCL bestows the rigid poly-ECA with high flexibility. A coated polyurethane sponge exhibits superhydrophobicity (water contact angle of >150°), while retaining robust mechanical stability and flexibility/elasticity. This provides an efficient means of cleaning oil spills with high selectivity, even after mechanical abrasion (>99% separation efficiency is retained after 120 tape test cycles and 50 rubbing test cycles), with excellent reusability

Flexible, Elastic, and Superhydrophobic/Superoleophilic Adhesive for Reusable and Durable Water/Oil Separation Coating

This study investigates a highly flexible/stretchable and mechanically durable superhydrophobic/superoleophilic coating for efficient oil/water separation and oil absorption. The coating is applied via a simple immersion process using a mixed solution of a biocompatible adhesive (ethyl cyanoacrylate, ECA), a highly stretchable polymer (polycaprolactone, PCL), and superhydrophobic/superoleophilic nanoparticles (fluorine-coated silica nanoparticles, F-SiO2 NPs) in a solvent, followed by solvent evaporation and ECA polymerization. Polymerized ECA (poly-ECA) in the coating material strongly adheres the F-SiO2 NPs to the substrate surface, while PCL bestows the rigid poly-ECA with high flexibility. A coated polyurethane sponge exhibits superhydrophobicity (water contact angle of >150°), while retaining robust mechanical stability and flexibility/elasticity. This provides an efficient means of cleaning oil spills with high selectivity, even after mechanical abrasion (>99% separation efficiency is retained after 120 tape test cycles and 50 rubbing test cycles), with excellent reusability