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Symmetry breaking and multi-functionality – artificial vs. biological morphogenesis

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Artificial materials exhibiting symmetry breaking, such as dynamic shape-change behaviour, are parsimonious, compared to biological systems, both in terms of number of components and mechanisms. This elegance allows us to study in greater fundamental detail their mechanisms and potential to control such behaviour. Symmetry breaking in living systems is often achieved by reaction-diffusion coupling, but recently nonlinearities in material properties have been shown key to achieving morphogenesis. We explore ways to break symmetry from the macroscopic to the molecular level. We have discovered fundamentally novel mechanisms to direct growth, shape change, and have a vision to develop them in the fields of artificial muscles, adaptive structures, and for bringing insights in the processes of morphogenesis.

We show examples of engineering the symmetry breaking and dynamics for multiple structures and processes, on multiple lengthscales – from nanometers to centimeters. We demonstrate the formation of Janus and other asymmetric particles, which form as a result of coupling of chemical reactions to non-linear mechanical properties of materials[1,2]. We also demonstrate the opposite effects – how mechanical deformations and molecular interactions can help one simplify chemical syntheses3.Further, we also demonstrate that even without reactions, the material properties and geometry alone could cause symmetry breaking. By bending a spherical cap and a cone shell, we characterize the instabilities and show novel behaviors, both static and dynamic. Upon inversion of the magnetic spherical cap, for example, using high speed video, we have captured and modelled an intermediate asymmetric quasi-stable state4.

Equilibrium deformations also show symmetry breaking – both macroscopic, and in phase-separation. We explore the energetics of these transitions in recent results. We combine the geometrical approaches with chemistry to achieve combinatorial multifunctionality. Instead of designing all the desired functions in a single molecule, we use controlled internal phase separation in a material to introduce existing materials with already optimized functions, and interweave them into one. We show how this spatial separation of just 3 phases and 20 functions would lead to over 8000 trifunctional materials. We demonstrate such interpenetrating networks with the separate individual functions, as well as emerging effects.

Finally, we describe molecular mechanisms we have discovered for bottom-up shape change in liquid droplets. It relies only on transformations inside the droplets and, without any external applied fields, is able to generate a number of regular geometric shapes, including octahedra, hexagons, rhomboids, triangles and fibers. We explain the transitions between these shapes and methods to control them in both the liquid and solid state. This scalable process is a molecularly based method for symmetry breaking on various scales.[6] I will outline a number of implications for further fundamental discoveries and for potential applied explorations in symmetry breaking, manufacturing and nanoscience.

The motivation for my talk at the Sainsbury lab is to exchange some ideas about morphogenesis, both artificial and plant-based, and generate new ideas (in synthetic biology?) at points of intersecting interest.

References:

[1] Ding T, Baumberg J, Smoukov SK, Harnessing Nonlinear Rubber Swelling for Bulk Synthesis of Anisotropic Hybrid Nanoparticles with Tunable Metal-Polymer Ratios, J. Mater. Chem. C, 2, 8745-8749 (2014) DOI : 10.1039/c4tc01660b

[2] Wang Y, Ding T, Baumberg J, Smoukov SK, Symmetry Breaking Polymerization: One-Pot Synthesis of Plasmonic Hybrid Janus Nanoparticles, Nanoscale 7, 10344-10349 (2015) DOI : 10.1039/c5nr01999k

[3] Marshall, JE, Gallagher S, Terentjev EM, Smoukov SK, Anisotropic Colloidal Micromuscles from Liquid Crystal Elastomers, J. Am. Chem. Soc., 136 (1), 474-479 (2014), DOI : 10.1021/ja410930g

[4] Loukaides E, Seffen KA, Smoukov SK, Magnetic Actuation and Transition Shapes of a Bistable Spherical Cap, Intl. J. Smart & Nano Mater. (2015) DOI : 10.1080/19475411.2014.997322

[5] Khaldi A, Plesse C, Vidal F, Smoukov SK, Designing Smarter Materials with Interpenetrating Polymer Networks, accepted in Adv. Mater. 27 (30), 4418–4422 (2015) DOI : 10.1002/adma.201500209

[6] Denkov N, Tcholakova S, Lesov I, Cholakova D, Smoukov SK, Self-Shaping of Droplets via Formation of Intermediate Rotator Phases upon Cooling, NATURE 528 , 392–395 (2015), DOI : 10.1038/nature16189

Bio: Stoyan Smoukov is the Head of the Active and Intelligent Materials group in the Department of Materials Science and Metallurgy at the University of Cambridge, where he has been since 2012. He is leading the work on an ERC grant EMATTER , as well as several industrial collaborations. He is the author of 54 journal papers, cited over 1550 times, with H-index of 18. He received his M.Sc. and Ph.D. in Physical/Analytical chemistry at Northwestern University with Prof. Brian Hoffman. His post-doctoral work was all at departments of Chemical Engineering, first at the Illinois Institute of Technology (Profs. Venerus and Schieber), then back in Northwestern (Prof. Grzybowski). He then joined North Carolina State University, working with Prof. Orlin Velev, first as Visiting Assistant Professor, and then promoted to Research Assistant Professor. His work in NC State was on reconfigurable assembly and disassembly of magnetic Janus particles, as well on a novel method for fabricating bulk amounts of inexpensive nanofibers, which has been spun off into a successful startup company. Stoyan Smoukov’s current research interests are focused on fundamental investigations of multi-responsive materials, materials in confinement, as well as the use of geometry and processing technologies for achieving responsiveness.

This talk is part of the Sainsbury Laboratory Seminars series.

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