Scalable and continuous fabrication of bio-inspired dry adhesives with a thermosetting polymer

Abstract

Many research groups have developed unique micro/nano-structured dry adhesives by mimicking the foot of the gecko with the use of molding methods. Through these previous works, polydimethylsiloxane (PDMS) has been developed and become the most commonly used material for making artificial dry adhesives. The material properties of PDMS are well suited for making dry adhesives, such as conformal contacts with almost zero preload, low elastic moduli for stickiness, and easy cleaning with low surface energy. From a performance point of view, dry adhesives made with PDMS can be highly advantageous but are limited by its low productivity, as production takes an average of approximately two hours. Given the low productivity of PDMS, some research groups have developed dry adhesives using UV-curable materials, which are capable of continuous roll-to-roll production processes. However, UV-curable materials were too rigid to produce good adhesion. Thus, we established a PDMS continuous-production system to achieve good productivity and adhesion performance. We designed a thermal roll-imprinting lithography (TRL) system for the continuous production of PDMS microstructures by shortening the curing time by controlling the curing temperature (the production speed is up to 150 mm min-1). Dry adhesives composed of PDMS were fabricated continuously via the TRL system.

Engineering Micropatterned Dry Adhesives: From Contact Theory to Handling Applications

“…The rising demand for such a new technology brings with it several open questions related to specific applications, such as reliability and long‐term durability. The feasibility of large‐scale fabrication has recently been demonstrated by roll‐to‐roll fabrication in the groups of Kwak and co‐workers and Jeong and co‐workers . In this way, the universal phenomenon of adhesion will, through modulation by micropatterning, very likely be exploited in numerous future applications.…”

Continuous Fabrication of Wide-Tip Microstructures for Bio-Inspired Dry Adhesives via Tip Inking Process

“…Mushroom-shaped microstructure-based dry adhesives are expected to be applied in various fields, thanks to their unique properties, such as strong adhesive force, repeatability, durability, reversibility, and self-cleaning [1][2][3][4][5][6][7][8][9]. e application is evident not only in daily necessities but also in industries as a very strong adhesive on a smooth surface.…”

“…However, in order for dry adhesives to be widely used, the efficiency of the production process needs to be increased. Until now, dry adhesives have been made by fabricating a silicon master using a complex surface micromachining process and then replicating thermosetting or UV-curable resins [1][2][3][4][5][6][7][8][9][10][11][12][13]. In most dry adhesives, because of the larger spatula or mushroom shape, it was very difficult and costly to fabricate a silicon master [4,14].…”

“…However, this method is very difficult to produce a mold with a negative mushroom shape in the form of a film, and further development is required for high-yield production. In order to overcome these material limitations, a continuous production process using thermosetting polymers has been developed [5]. Polydimethylsiloxane (PDMS), which is mainly used for dry adhesives, has a very good conformal contact property and has excellent adhesion performance when it is made with dry adhesives.…”

“…However, since this material generally takes about 1 hour to cure, continuous production is difficult to achieve. Lee et al have developed a technology that can produce a continuous roll-to-roll type by thinning the sample and increasing the curing temperature to shorten the time [5]. In order to produce a dry adhesive having a wide tip for high-performance adhesives, the resin must be completely filled with a mold having a negative tip structure.…”