S3E10
Episode 10 (March 21, 2021)
Simon Bettscheider
Leibniz institute for new materials
Haocheng Quan
Leibniz institute for new materials
Mingchao Liu
University of Oxford
Measuring the adhesive performance of bio-inspired micropatterned surfaces
Abstract of Talk 1
Geckos and insects can adhere to surfaces using physical forces and the principle of contact splitting. This concept can be mimicked in technical applications by micropatterning soft surfaces to create fibrillar dry adhesives. The performance of such fibrillar adhesives is commonly measured in tensile tests with axisymmetric probes having either a flat punch or spherical geometry. When using spherical probes, the measured performance depends strongly on the compressive preload applied when making contact and on the geometry of the probe. Comparing the performance of fibrillar adhesives measured in different experiments is therefore not possible. We explore this issue by extending previous theoretical treatments of this problem and demonstrate that existing continuum theories cannot accurately describe the performance of fibrillar adhesives. We show that the local adhesive strength of the fibrils is a measurement-independent performance indicator and present an experimental procedure and a convenient simulation tool to extract it.
Biosketch of Speaker 1
Simon Bettscheider is Ph.D. candidate at the Leibniz Institute for New Materials (INM) in Saarbrücken, Germany. He received a B.Sc. degree in Mechanical Engineering from Oregon State University and a B.Sc. and M.Sc. degree in Materials Science from Saarland University. Supervised by Prof. Eduard Arzt at INM and Prof. Bob McMeeking and Prof. Kimberly Foster at the University of California, Santa Barbara, he researched into micropatterned adhesives that mimic nature’s principle of contact splitting. His current research focuses on colloidal and physical properties of ultrathin nanowires.
Materials design of dermal armors and hydration-induced actuation in plants
Abstract of Talk 1
Through billions of years of evolution, nature develops numerous efficient structural and functional materials, which manifest various fascinating properties that are superior to synthetic counterparts. In this presentation, I will briefly introduce two topics: the materials design of fish scales and hydro-actuated reversible deformation of pine cones. In the first topic, the scales of two fish (coelacanth and carp) will be discussed and their toughening mechanisms will be compared. The uncovered Bouligand-type structures confer these scales strength, toughness and light weight synergistically, which can provide inspiration for developing new structural materials. In the second topic, the mechanisms of hydration induced actuations in many plant organs will be summarized and some new findings from a classic example, pine cone, will be discussed in details. Our findings provide an interdisciplinary perspective combining materials science, structural engineering and biology, as well as offering some design models for development of novel smart responsive materials.
Biosketch of Speaker 1
Dr. Haocheng Quan obtained his PhD from UC San Diego in 2019, under the supervision of Prof. Marc A. Meyers. In 2020, he started working as a postdoc at Leibniz Institute for New Materials in Germany, under supervision of Prof. Eduard Arzt and Dr. Rene Hensel. His research mainly focuses on: 1) discovering the connection between the hierarchical structure and mechanical performance of various biological materials; 2) improving the strength and toughness of synthetic materials by implementing the design strategies identified in nature, and 3) developing novel non-destructive adhesive materials inspired by gecko feet. He has published several papers in Nature Reviews Materials, Materials Today, Advanced Functional Materials, Matter, etc. He also likes cruising, scuba diving and hiking, which perfectly combines his hobbies with his research interests.
Spider-morphs: Designing 3D shapes from multiple tapered elasticæ
Abstract of Talk 3
Foldable three-dimensional (3D) structures are important in a wide range of engineering applications. Transforming flat two-dimensional (2D) sheets with cuts into 3D structures, or kirigami, has emerged as an exciting manufacturing paradigm. However, achieving a particular 3D shape usually requires multiple materials and/or the application of external stimuli. Here we introduce a design framework for forming approximately axisymmetric 3D structures by harnessing the buckling of multiple tapered elastic sheets (the legs) connected in a central portion (the body). Together this creates a spider-like structure that morphs in 3D: a spider-morph. We design spider-morphs that deform into axisymmetric 3D structures with positive, negative, and variable Gaussian curvature. We conduct both numerical simulations and physical experiments to verify our theoretical approach.
Biosketch of Speaker 3
Dr. Mingchao Liu is currently a Newton International Fellow at the Mathematical Institute, University of Oxford, sponsored by the Royal Society. He graduated from Tsinghua University in 2018 with a PhD in Engineering from the Department of Engineering Mechanics. During his PhD study, he spent six months in 2017 as a visiting research fellow at the University of Sydney under the support of the Endeavour Research Fellowship. Prior to this, He received his B.S. in Engineering Mechanics from Shandong University in 2013. His current research is mainly focused on elastic instability and its application in morphing structures and mechanical metamaterials.
Guest Host: Xuan Zhang
Dr. Xuan Zhang has been researching at the Leibniz Institute in Saarbrücken with funding from the Humboldt Foundation. Zhang studied Mechanical Engineering at Tsinghua University in Beijing, where she received her doctorate in 2018. Under the guidance of Prof. Eduard Arzt, head of the program area “Functional Microstructures” and chairman of the INM management board, she will devote the next two years to research on so-called metamaterials. These materials have a defined microstructure and thus new mechanical properties that also allow new applications. They will be manufactured by a 3D printer. The design is developed beforehand using computer-based simulations. Such metamaterials are used, for example, in adhesive systems, where the microstructure enables the adhesion to be switched on and off.