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    Present and future of surface-enhanced Raman scattering
    (Washington, DC : ACS Publications, 2020) Langer, Judith; de Aberasturi, Dorleta Jimenez; Aizpurua, Javier; Alvarez-Puebla, Ramon A.; Auguié, Baptiste; Baumberg, Jeremy J.; Bazan, Guillermo C.; Bell, Steven E.J.; Boisen, Anja; Brolo, Alexandre G.; Choo, Jaebum; Cialla-May, Dana; Deckert, Volker; Fabris, Laura; Faulds, Karen; de Abajo, F. Javier García; Goodacre, Royston; Graham, Duncan; Haes, Amanda J.; Haynes, Christy L.; Huck, Christian; Itoh, Tamitake; Käll, Mikael; Kneipp, Janina; Kotov, Nicholas A.; Kuang, Hua; Le Ru, Eric C.; Lee, Hiang Kwee; Li, Jian-Feng; Ling, Xing Yi; Maier, Stefan A.; Mayerhöfer, Thomas; Moskovits, Martin; Murakoshi, Kei; Nam, Jwa-Min; Nie, Shuming; Ozaki, Yukihiro; Pastoriza-Santos, Isabel; Perez-Juste, Jorge; Popp, Juergen; Pucci, Annemarie; Reich, Stephanie; Ren, Bin; Schatz, George C.; Shegai, Timur; Schlücker, Sebastian; Tay, Li-Lin; Thomas, K. George; Tian, Zhong-Qun; Van Duyne, Richard P.; Vo-Dinh, Tuan; Wang, Yue; Willets, Katherine A.; Xu, Chuanlai; Xu, Hongxing; Xu, Yikai; Yamamoto, Yuko S.; Zhao, Bing; Liz-Marzán, Luis M.
    The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.
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    Zirconium-Catalyzed Atom-Economical Synthesis of 1,1-Diborylalkanes from Terminal and Internal Alkenes
    (Weinheim : Wiley-VCH, 2020) Wang, Xianjin; Cui, Xin; Li, Sida; Wang, Yue; Xia, Chungu; Jiao, Haijun; Wu, Lipeng
    A general and atom-economical synthesis of 1,1-diborylalkanes from alkenes and a borane without the need for an additional H2 acceptor is reported for the first time. The key to our success is the use of an earth-abundant zirconium-based catalyst, which allows a balance of self-contradictory reactivities (dehydrogenative boration and hydroboration) to be achieved. Our method avoids using an excess amount of another alkene as an H2 acceptor, which was required in other reported systems. Furthermore, substrates such as simple long-chain aliphatic alkenes that did not react before also underwent 1,1-diboration in our system. Significantly, the unprecedented 1,1-diboration of internal alkenes enabled the preparation of 1,1-diborylalkanes. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
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    Sliding Mechanism for Release of Superlight Objects from Micropatterned Adhesives
    (Weinheim : Wiley-VCH, 2022) Wang, Yue; Zhang, Xuan; Hensel, René; Arzt, Eduard
    Robotic handling and transfer printing of micrometer-sized superlight objects is a crucial technology in industrial fabrication. In contrast to the precise gripping with micropatterned adhesives, the reliable release of superlight objects with negligible weight is a great challenge. Slanted deformable polymer microstructures, with typical pillar cross-section 150 µm × 50 µm, are introduced with various tilt angles that enable a reduction of adhesion by a switching ratio of up to 500. The experiments demonstrate that the release from a smooth surface involves sliding of the contact during compression and subsequent peeling of the object during retraction. The handling of a 0.5 mg perfluorinated polymer micro-object with high accuracy in repeated pick-and-place cycles is demonstrated. Based on beam theory, the forces and moments acting at the tip of the microstructure are analyzed. As a result, an expression for the pull-off force is proposed as a function of the sliding distance and a guide to an optimized design for these release structures is provided.
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    Bioinspired Underwater Adhesion to Rough Substrates by Cavity Collapse of Cupped Microstructures
    (Weinheim : Wiley-VCH, 2021) Wang, Yue; Hensel, René
    Underwater or wet adhesion is highly desirable for numerous applications but is counteracted by the liquids in the contact which weaken intermolecular attraction. The problem is exacerbated in conjunction with surface roughness when liquids partially remain in grooves or dimples of the substrate. In the present study, a cupped microstructure with a cavity inspired by suction organs of aquatic animals is proposed. The microstructures (cup radius of 100 µm) are made from polyurethane using two-photon lithography followed by replica molding. Adhesion to rough substrates is emulated experimentally by a micropatterned model substrate with varying channel widths. Pull-off stresses are found to be about 200 kPa, i.e., twice atmospheric pressure. Evaluation of force–displacement curves together with in situ observations reveal the adhesion mechanism, which involves adaptation to surface roughness and an elastic force induced by the collapse of the cavity that holds sealed contact with the substrate during retraction. This new microarchitecture may pave the way for next generation microstructures applicable to real, rough surfaces under wet conditions.