Enhanced Flexible Mold Lifetime for Roll‐to‐Roll Scaled‐Up Manufacturing of Adhesive Complex Microstructures

Abstract

Various functional complex 3D patterned surfaces with micro‐ or nanostructures have been developed and their superior performances over non‐patterned smooth surfaces proven. However, it is challenging to mass‐produce such complex micro‐/nanopatterned surfaces, which limits their commercialization drastically. Although roll‐to‐roll (R2R) manufacturing using flexible molds has been implemented for mass‐production of such functional surfaces, the poor mold repeatability issue has not been resolved yet. Here, a strategy to significantly improve the repeatability of the micropatterned flexible silicone molds over 1000 cycles against highly adhesive polyurethane acrylates (PUAs) in UV light curing based R2R systems by using a two‐step curing process is reported. The mold repeatability is drastically increased from 10s of cycles to over 1000 cycles through the proposed strategy in spite of the complicated 3D undercut geometry and high tackiness of the microstructure. This two‐step process would enable scaled‐up production of micro‐/nanostructured adhesives, such as gecko‐inspired microfiber adhesives as demonstrated in this study, as well as various other functional micro‐/nanostructured surfaces by enhancing the flexible mold lifetime.

It's time for an update—A perspective on fuel cell electrodes

“…Techniques that allow wettability control of polymers, [28] incorporating new 2D materials with proton transport capabilities, [29] biomimetic designs, [30] and 3D printing with control over metal distribution [31] and type [32] are a few examples. Additionally, leveraging comparatively mature coating technologies such as for battery electrodes, [33] solar cells, [34] and light emitting devices [35] can inspire new methods for high-throughput fabrication of alternative electrodes. Particularly for electrode structures that rely on patterned templates, which pose greater challenge for high-throughput fabrication, leveraging semiconductor manufacturing technologies could offer an attractive solution for scaling up.…”

Bioinspired Microstructured Adhesives with Facile and Fast Switchability for Part Manipulation in Dry and Wet Conditions

“…[8,9] Inspired by those attachment systems, there have been mainly two most popular bioinspired adhesives: the mushroom-shaped structure inspired by the ladybird beetle's footpad [10,11] and the wedge-shaped structure inspired by the gecko's footpad. [8,12,13] While the mushroom-shaped structures showed high attachment forces thanks to the crack trapping, surface defect adaptation, and prevention of stress concentration, [14][15][16][17] they are difficult to switch between sticky and non-sticky states, which is the most important factor in temporary attachment. [18][19][20] In addition, due to the limitations of the fabrication methods, the shape and size of the contact tips were limited, which reduced the attachment performance.…”

Photothermal‐Driven Crawlable Soft Robot with Bionic Earthworm‐Like Bristle Structure

“…This idea is completely different from the previously reported systems that used ultrafine setae imitating the gecko's foot to achieve reversible adhesion through the van der Waals force and make the robot move. [23][24][25][26][27][28][29] The ideal adhesion for "gecko's foot" systems is essential for these kinds of DOI: 10.1002/aisy.202300540 Remote stimuli-responsive movable soft robots without the need for complex 3D deformation processes and specific working environments is an unsolved problem and urgent need. In this work, under the inspiration of mother nature, a novel strategy of simple combination of the bionic bristles structure and the photothermal-driven reversible shape change liquid crystal polymer (LCP) actuator is proposed to work out this difficulty.…”

“…This idea is completely different from the previously reported systems that used ultrafine setae imitating the gecko's foot to achieve reversible adhesion through the van der Waals force and make the robot move. [ 23–29 ] The ideal adhesion for “gecko's foot” systems is essential for these kinds of structural designs of microfibrillar tip shapes, which will also inevitably increase the difficulty of robot preparation. In contrast, the motion mechanism for our design does not require the structure design of bristle tip shapes, just that the simple solid fiber will meet the requirement.…”