Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers

Smart adhesives that can be applied and removed on demand play an important role in modern life and manufacturing. However, current smart adhesives made of elastomers suffer from the long-standing challenges of the adhesion paradox (rapid decrease in adhesion strength on rough surfaces despite adhes...

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Main Authors: Linghu, Changhong, Liu, Yangchengyi, Tan, Yee Yuan, Sing, Marcus Jun Heng, Tang, Yuxuan, Zhou, Aiwu, Wang, Xiufeng, Li, Dong, Gao, Huajian, Hsia, K. Jimmy
Other Authors: School of Mechanical and Aerospace Engineering
Format: Article
Language:English
Published: 2023
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Online Access:https://hdl.handle.net/10356/170061
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spelling sg-ntu-dr.10356-1700612023-08-26T16:48:11Z Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers Linghu, Changhong Liu, Yangchengyi Tan, Yee Yuan Sing, Marcus Jun Heng Tang, Yuxuan Zhou, Aiwu Wang, Xiufeng Li, Dong Gao, Huajian Hsia, K. Jimmy School of Mechanical and Aerospace Engineering School of Chemical and Biomedical Engineering Institute of High-Performance Computing, A*STAR Engineering::Mechanical engineering Engineering::Chemical technology Smart Adhesives Adhesion Paradox Smart adhesives that can be applied and removed on demand play an important role in modern life and manufacturing. However, current smart adhesives made of elastomers suffer from the long-standing challenges of the adhesion paradox (rapid decrease in adhesion strength on rough surfaces despite adhesive molecular interactions) and the switchability conflict (trade-off between adhesion strength and easy detachment). Here, we report the use of shape-memory polymers (SMPs) to overcome the adhesion paradox and switchability conflict on rough surfaces. Utilizing the rubbery-glassy phase transition in SMPs, we demonstrate, through mechanical testing and mechanics modeling, that the conformal contact in the rubbery state followed by the shape-locking effect in the glassy state results in the so-called rubber-to-glass (R2G) adhesion (defined as making contact in the rubbery state to a certain indentation depth followed by detachment in the glassy state), with extraordinary adhesion strength (>1 MPa) proportional to the true surface area of a rough surface, overcoming the classic adhesion paradox. Furthermore, upon transitioning back to the rubbery state, the SMP adhesives can detach easily due to the shape-memory effect, leading to a simultaneous improvement in adhesion switchability (up to 103, defined as the ratio of the SMP R2G adhesion to its rubbery-state adhesion) as the surface roughness increases. The working principle and the mechanics model of R2G adhesion provide guidelines for developing stronger and more switchable adhesives adaptable to rough surfaces, thereby enhancing the capabilities of smart adhesives, and impacting various fields such as adhesive grippers and climbing robots. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University Published version We acknowledge financial support by the Ministry of Education (MOE) of Singapore under Academic Research Fund Tier 2 (T2EP50122- 0001). C.L. acknowledges a Graduate Research Scholarship sup-ported by the MOE of Singapore. Y.L. acknowledges the scholarship support as Visiting PhD Student from the China Scholarship Council. K.J.H. acknowledges a research start- up grant (002271- 00001) from the Nanyang Technological University. H.G. acknowledges a research start-up grant (002479-00001) from the Nanyang Technological University and the Agency for Science, Technology and Research (A*STAR) and the use of the A*STAR Computational Resource Centre, Singapore, and National Supercomputing Centre, Singapore. H.G. and D.L. also acknowledge support from the MOE of Singapore AcRF Tier 1 (Grant RG120/21). 2023-08-23T02:09:13Z 2023-08-23T02:09:13Z 2023 Journal Article Linghu, C., Liu, Y., Tan, Y. Y., Sing, M. J. H., Tang, Y., Zhou, A., Wang, X., Li, D., Gao, H. & Hsia, K. J. (2023). Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers. Proceedings of the National Academy of Sciences, 120(13), e2221049120-. https://dx.doi.org/10.1073/pnas.2221049120 0027-8424 https://hdl.handle.net/10356/170061 10.1073/pnas.2221049120 36940332 2-s2.0-85150672450 13 120 e2221049120 en T2EP50122- 0001 002271- 00001 002479-00001 RG120/21 Proceedings of the National Academy of Sciences © 2023 the Author(s). Published by PNAS. This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY- NC-ND). application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Mechanical engineering
Engineering::Chemical technology
Smart Adhesives
Adhesion Paradox
spellingShingle Engineering::Mechanical engineering
Engineering::Chemical technology
Smart Adhesives
Adhesion Paradox
Linghu, Changhong
Liu, Yangchengyi
Tan, Yee Yuan
Sing, Marcus Jun Heng
Tang, Yuxuan
Zhou, Aiwu
Wang, Xiufeng
Li, Dong
Gao, Huajian
Hsia, K. Jimmy
Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers
description Smart adhesives that can be applied and removed on demand play an important role in modern life and manufacturing. However, current smart adhesives made of elastomers suffer from the long-standing challenges of the adhesion paradox (rapid decrease in adhesion strength on rough surfaces despite adhesive molecular interactions) and the switchability conflict (trade-off between adhesion strength and easy detachment). Here, we report the use of shape-memory polymers (SMPs) to overcome the adhesion paradox and switchability conflict on rough surfaces. Utilizing the rubbery-glassy phase transition in SMPs, we demonstrate, through mechanical testing and mechanics modeling, that the conformal contact in the rubbery state followed by the shape-locking effect in the glassy state results in the so-called rubber-to-glass (R2G) adhesion (defined as making contact in the rubbery state to a certain indentation depth followed by detachment in the glassy state), with extraordinary adhesion strength (>1 MPa) proportional to the true surface area of a rough surface, overcoming the classic adhesion paradox. Furthermore, upon transitioning back to the rubbery state, the SMP adhesives can detach easily due to the shape-memory effect, leading to a simultaneous improvement in adhesion switchability (up to 103, defined as the ratio of the SMP R2G adhesion to its rubbery-state adhesion) as the surface roughness increases. The working principle and the mechanics model of R2G adhesion provide guidelines for developing stronger and more switchable adhesives adaptable to rough surfaces, thereby enhancing the capabilities of smart adhesives, and impacting various fields such as adhesive grippers and climbing robots.
author2 School of Mechanical and Aerospace Engineering
author_facet School of Mechanical and Aerospace Engineering
Linghu, Changhong
Liu, Yangchengyi
Tan, Yee Yuan
Sing, Marcus Jun Heng
Tang, Yuxuan
Zhou, Aiwu
Wang, Xiufeng
Li, Dong
Gao, Huajian
Hsia, K. Jimmy
format Article
author Linghu, Changhong
Liu, Yangchengyi
Tan, Yee Yuan
Sing, Marcus Jun Heng
Tang, Yuxuan
Zhou, Aiwu
Wang, Xiufeng
Li, Dong
Gao, Huajian
Hsia, K. Jimmy
author_sort Linghu, Changhong
title Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers
title_short Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers
title_full Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers
title_fullStr Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers
title_full_unstemmed Overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers
title_sort overcoming the adhesion paradox and switchability conflict on rough surfaces with shape-memory polymers
publishDate 2023
url https://hdl.handle.net/10356/170061
_version_ 1779156291974856704