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Yi, Hoon,Hwang, Insol,Lee, Jeong Hyeon,Lee, Dael,Lim, Haneol,Tahk, Dongha,Sung, Minho,Bae, Won-Gyu,Choi, Se-Jin,Kwak, Moon Kyu,Jeong, Hoon Eui American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.16
<P>A simple yet scalable strategy for fabricating dry adhesives with mushroom-shaped micropillars is achieved by a combination of the roll-to-roll process and modulated UV-curable elastic poly(urethane acrylate) (e-PUA) resin. The e-PUA combines the major benefits of commercial PUA and poly(dimethylsiloxane) (PDMS). It not only can be cured within a few seconds like commercial PUA but also possesses good mechanical properties comparable to those of PDMS. A roll-type fabrication system equipped with a rollable mold and a UV exposure unit is also developed for the continuous process. By integrating the roll-to-roll process with the e-PUA, dry adhesives with spatulate tips in the form of a thin flexible film can be generated in a highly continuous and scalable manner. The fabricated dry adhesives with mushroom-shaped microstructures exhibit a strong pull-off strength of up to ∼38.7 N cm<SUP>–2</SUP> on the glass surface as well as high durability without any noticeable degradation. Furthermore, an automated substrate transportation system equipped with the dry adhesives can transport a 300 mm Si wafer over 10 000 repeating cycles with high accuracy.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-16/am503901f/production/images/medium/am-2014-03901f_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am503901f'>ACS Electronic Supporting Info</A></P>
Significant Adhesion Enhancement of Bioinspired Dry Adhesives by Simple Thermal Treatment
Minho Seong,Joosung Lee,Insol Hwang,Hoon Eui Jeong 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.6 No.3
Bioinspired dry adhesives with micropillar arrays can be harnessed for precise and environment-friendly manufacturing. This study presents a simple and robust approach for developing synthetic dry adhesives with significantly enhanced adhesion strength without sophisticated structural modification or chemical surface treatment. We show that when dry adhesives with micropillar arrays are annealed at slightly elevated temperatures of 150–200 °C, their adhesion strengths are remarkably enhanced (maximum normal adhesion: 50.0 N cm−2) compared to those that are not treated thermally (normal adhesion: 17.6 N cm−2). The enhanced adhesion levels obtained by simple annealing surpass those of previously reported dry adhesives having nanoscale hairs with high aspect ratios or mushroom-like pillars with large tips. Experimental investigations regarding the chemical structure, surface roughness, surface energy, and elastic modulus of the dry adhesive samples indicate that the enhanced adhesion originates from the annealing-induced enhancement of the adhesive’s elastic modulus
Bio-inspired frictional pads made of CNT composites for high temperature process
Hoon Yi,Minho Sung,Insol Hwang,Hangil Ko,Hyun-ha Park,Hoon Eui Jeong 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
During the assembly process of semiconductors or display devices, silicon wafers or glass substrates, which are usually very thin, large, and fragile, should be carefully handled with high accuracy. Moreover, there should be no surface contamination on the substrates. Thus, bio-inspired mushroom-shaped adhesive pads have strong potential to replace existing techniques such as vacuum suction or electrostatic chucks since dry adhesives enable precise manipulation of various substrates without any surface contamination in a reversible, repeatable, and durable manner. To fabricate mushroom-shaped dry adhesives, poly(dimethyl siloxane) (PDMS) have been widely used because they have favorable mechanical properties such as low elastic modulus and high elongation break, which allows for simple and reliable prototyping. Furthermore, the low elastic modulus of the PDMS allows the replicated structures to make a conformal contact against varying substrates even under low preload and therefore exhibit a high level of adhesion strength. In spite of these advantages, the PDMS shows inherent limitations in maintaining its form and adhesion strength at high temperature (> 200 ℃), which brings restrictions on practical application for various high-temperature manufacturing process. To address this limitation, we suggest bio-inspired adhesive pads using carbon nanotube (CNT) composite which have enhanced durability and stability at high-temperature conditions.