报告题目：Topology & Technology of Knots: From Chinese Knotting to Active Topological Matter
Ivan I. Smalyukh is a full professor at the Department of Physics at CU-Boulder, which he joined in 2007. He is also a founding fellow of Renewable Sustainable Energy Institute and Materials Science Engineering Program and directs the Soft Matter Physics Group at CU-Boulder. His research focuses on soft matter and biological systems, including liquid crystals, colloids, polymers, bacteria, gels, biomaterials and their photonic, electro-optic and energy-related applications. He has published more than 200 SCI papers, including many inNature (2),Science (3),Nature Materials(4),Nature Communications(5),PANSand many others. He is a fellow of the American Physical Society (APS). He received many awards, including the Bessel and Glenn Brown Awards, the PECASE Award from the White House and the GSoft Award from the American Physical Society.
Humankind has been obsessed with knots in religion, culture and daily life for millennia, with archeological examples of knotting preserved from prehistoric times. In science, starting from Gauss, Kelvin and Skyrme, knots in fields were postulated behaving like particles, but experimentally they were found only as transient features and couldn’t self-assemble into three-dimensional crystals. We introduce energetically stable knots in helical fields of chiral liquid crystals, which we call “heliknotons”. While spatially localized and freely diffusing in all directions, they resemble colloidal particles and atoms, self-assembling into triclinic and other crystalline lattices with open and closed structures. These knots are robust and topologically distinct from the host medium, though in liquid crystals they can be morphed and reconfigured by weak stimuli under conditions like in displays, exhibiting giant electrostriction of the ensuing crystals. A combination of free-energy-minimizing numerical modeling and imaging uncovers the internal structure and topology of individual helical field knots and various hierarchical crystalline organizations that they form. I will discuss how such structures can be used to realize knotting on micrometer and nanometer scales, with the topological field configurations decorated by nanoparticles made of gold and other inorganic compounds to pre-engineer physical behavior and material properties, as well as to realize active-matter-like behavior.