Durability Improvement of Synthetic Dry Adhesives by Metal Coatings

Gyuhe Kim,Hui Yun Hwang,Taechang Ahn

doi:10.1155/2017/1696038

Gyuhe Kim, Hui Yun Hwang + Show 1 more

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https://doi.org/10.1155/2017/1696038

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Abstract

Gecko-like synthetic dry adhesives (SDAs) have adhesion comparable to that of a real Gecko’s foot, but with very low durability. To address this problem, self-cleaning or stiff core embedding methods have been proposed. However, the proposed methods require special locomotion or complicated manufacturing. In this study, we suggested a metal coating on synthetic dry adhesives to improve durability. SDAs were fabricated via PDMS. Then, metals such as indium, zinc, and gold were coated on the SDAs. The adhesion tests show that the indium- and zinc-coated microstructures have a higher shear adhesion strength than the noncoated ones. Also, the shear adhesion strength of noncoated SDAs was only 14.5% of the initial strength while that of the zinc-coated ones was 35.6% after 200 times of attachment and detachment. We could find PDMS debris and fractures on noncoated SDAs, which results in weakening of the adhesion strength. On the other hand, a relatively high hardness, strength, and stiffness of the zinc coating layers reduced the wear and fractures of the micropatterns, which led to an improved durability in the SDAs. From these tests, we can conclude that the metal coating method could improve the durability of the SDAs.

Highlights

Many researchers have engineered systems with a higher efficiency by adopting novel features that have been observed in nature
In the initial phase, micro- or nanopatterned structures with a high aspect ratio were designed for synthetic dry adhesives (SDAs), and their adhesion characteristics were evaluated using a pull-off test, friction test, and peeling test [17,18,19]
The shear adhesion strength of the SDAs coated with indium increased from 3.9 kPa to 10.9 kPa when the indium thickness increased from 2 nm to 4 nm, and the shear adhesion strength with an indium thickness ranging from 4 nm to 10 nm decreased from 10.9 kPa to 4.51 kPa

Summary

Introduction

Many researchers have engineered systems with a higher efficiency by adopting novel features that have been observed in nature. Polymers or elastomers such as polydimethylsiloxane (PDMS) have been widely used for SDAs due to their flexibility and ease of fabrication These materials have a low stiffness and strength, which reduces the adhesion strength of the micro- and nanopillars due to fiber collapse, abrasion, and fracture [1, 22, 42,43,44]. This limits SDAs to only a single application, such as medical patches, whereas demand for applications for robot hands and transportation equipment for clean rooms requires a more durable adhesion. Maintaining the adhesion strength of the SDAs can Advances in Materials Science and Engineering

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