Martin Wegener, Institute of Nanotechnology, KIT

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Prof. Dr. Martin Wegener, Director and Research Unit Chair at Institute of Nanotechnology (INT), KIT, Germany, will give a seminar “3D mechanical metamaterials” , on Wednesday, June 27th, 2018 at 03:00 p.m. in Pierre Cotton Room, Institut Fresnel.

Abstract : We review our recent work on 3D mechanical metamaterials, especially on 3D porous elastic (poroelastic) metamaterials and 3D chiral micropolar metamaterials. In 3D poroelastic metamaterials, one has to distinguish between the volume taken by the constituent material and the effective volume that is bordered by the overall porous structure. The effective compressibility is defined as the ordinary compressibility, except that it refers to the effective volume rather than the volume. The effective compressibility does not underlie the same constraints and bounds as the ordinary compressibility. In particular, the static effective compressibility can be negative [1,2,3] and can exceed the compressibility of air under ambient conditions [3].
3D chiral micropolar metamaterials (see figure) combine broken centrosymmetry and a unit cell of finite size. This combination allows for obtaining degrees of freedom that are forbidden in Cauchy elasticity but that are allowed in Eringen micropolar elasticity. In the static case, micropolar elasticity enables the coupling of translational and rotational degrees of freedom [4]. In the dynamic case [5], micropolar elasticity enables mechanical activity, the counterpart of optical activity in optics. Mechanical activity can, e.g., be used for mode conversion.

References
[1] J. Qu et al., Appl. Phys. Lett. 110, 171901 (2017)
[2] J. Qu et al., Phys. Rev. X 7, 041060 (2017)
[3] J. Qu et al., unpublished (2018)
[4] T. Frenzel et al., Science 358, 1072 (2017)
[5] T. Frenzel et al., unpublished (2018)

Biography : After completing his PhD in physics in 1987 at Johann Wolfgang Goethe-Universität Frankfurt (Germany), he spent two years as a postdoc at AT&T Bell Laboratories in Holmdel (U.S.A.). From 1990-1995 he was professor (C3) at Universität Dortmund (Germany), since 1995 he is professor (C4, later W3) at Institute of Applied Physics of Karlsruhe Institute of Technology (KIT). Since 2001 he has a joint appointment as department head at Institute of Nanotechnology (INT) of KIT, since 2016 he is director at INT. From 2001-2014 he was the coordinator of the DFG-Center for Functional Nanostructures (CFN) at KIT. His research interests comprise ultrafast optics, (extreme) nonlinear optics, near-field optics, optical laser lithography, photonic crystals, optical, mechanical, electronic, and thermodynamic metamaterials, as well as transformation physics. This research has led to various awards and honors, among which are the Alfried Krupp von Bohlen und Halbach Research Award 1993, the Baden-Württemberg Teaching Award 1998, the DFG Gottfried Wilhelm Leibniz Award 2000, the European Union René Descartes Prize 2005, the Baden-Württemberg Research Award 2005, the Carl Zeiss Research Award 2006, the Hector Research Award 2008, the SPIE Prism Award 2014 for the start-up company Nanoscribe GmbH, the Stifterverband Science Award – Erwin-Schrödinger Prize 2016, and the Technology Transfer Prize of the German Physical Society 2017/18. In 2014, 2015, 2016, and 2017, Thompson Reuters listed him as “Highly Cited Researcher” (top 1%). He is a member of Leopoldina, the German Academy of Sciences (since 2006), Fellow of the Optical Society of America (since 2008), and Honorary Professor at Huazhong University of Science & Technology, Wuhan, China (2014).

Contact : martin.wegener chez kit.edu

Invitation : Claude Amra, Concept group