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

Abstract

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 cm), 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.

Recent Progress in Preparation and Anti-Icing Applications of Superhydrophobic Coatings

“…The resultant sample surface displayed higher non-wettability with the apparent contact angle reaching 171 • and contact angle hysteresis as low as 5 • . Furthermore, Hee-Tak Kim group proposed a structural shape based on the vertical movement of azo-material driven by directional photofluidization imprint lithography (DPIL) [95], as shown in Figure 8. The technique provides a facile approach to fabricate complex hierarchical micro-nanostructures.…”

Multimodal control of liquid crystalline mesophases from surfactants with photoswitchable tails

“…Azobenzene is commonly used as a prototypical molecular switch as it undergoes a trans-cis photoisomerisation under UV irradiation, 20,21 which can be reversed over many cycles with either blue light or heat. [22][23][24] Upon incorporation into a surfactant, photoisomerisation leads to a substantial change in the geometry, hydrophilicity and packing of azobenzene photosurfactants (AzoPS) at both the molecular and micellar level. [25][26][27] However, while conventional surfactants self-assemble into a variety of LLC polymorphs at concentrations significantly above the critical micelle concentration (cmc), reports of LLC phase formation in pure AzoPS systems are still rare.…”

Hydrocipher: Bioinspired Dynamic Structural Color‐Based Cryptographic Surface

“…The values were also invariant (0.92 ± 0.09) with the cycling, as shown in Figure b. This high reversibility can be attributed to the covalent bonds between the micropillars and hydrogel layer, which withstands the stress at the hydrogel/micropillar interface generated by the volume change of the surrounding hydrogel …”

“…Although the grating diffraction develops a relatively faint color, it provides a wider viewing angle and higher angle dependency; 3D and 1D colloidal crystals and cholesteric liquid crystals show bright reflection colors only for specular reflection, at which a blueshift from red to blue requires the change of the angle as large as several tens of degrees . In addition, the structures can be easily produced by simple micromolding processes such as soft lithography and imprinting . Due to these advantages, the diffraction gratings with straight line, spiral, and butterfly‐like 2D patterns have been employed to develop diffraction colors in the banknote .…”