题目：In- and Out-of-equilibrium Behavior of Colloid Clusters with Broken Symmetries
报告人：Ning Wu (吴宁）教授
Department of Chemical & Biological Engineering, Colorado School of Mines,
USA
时间：7月29日（周三）上午10:30
地点：独墅湖校区401号楼一楼会议室
欢迎广大师生踊跃参加！
医学部欧洲杯官网
放射医学及交叉学科研究院
Abstract
Colloids are critical in our daily life and modern technologies. Among which the colloidal clusters, consisting of several particles aggregated into a predefined structure, emerge as an important family of the colloidal genome. Scientifically, the in- and out-of-equilibrium behavior of colloidal clusters are fundamentally different from conventional particles because of their intrinsic asymmetry in geometric, interfacial, and compositional properties. Technologically, recent computations predict a number of new optical properties arising from the electromagnetic-field coupling of individual constituents within and between clusters in a periodic array. However, scalable fabrication of well-controlled clusters is challenging, which severely limits our fundamental understanding and prevents their practical implementation.
In this talk, we will discuss our recent efforts in the synthesis, assembly, and application of colloidal clusters. In particular, we will show that these particles possess orientation-dependent interactions under applied electric fields. Surprisingly rich patterns and crystalline arrays (such as Ising-like lattices, graphene-like structures, and quasicrystalline mesophases) can be obtained in experiments. Our theoretical modeling and numerical simulation further demonstrate that the competition and balance between electrostatic and electro-hydrodynamic interactions dictate different phases and assembly paths between anisotropic particles. Breaking symmetry is also an important strategy to induce propulsion of micro- and nano-objects in low Reynolds number flow. Here, we will describe a new type of particle propulsion mechanism that is based on breaking the symmetry of electrokinetic flow using low power AC electric fields. Both linear and circular motions of colloidal clusters can be conveniently controlled by a series experimental parameters. In the last part of this talk, we will discuss several energy-related applications of colloidal clusters.
Selected publications:
1. Fuduo Ma, Sijia Wang, David T. Wu, and Ning Wu, "Electric-Field Induced Assembly and Propulsion of Chiral Colloidal Clusters", Proceedings of the National Academy of Sciences,112, 6307-6312 (2015).
2. Fuduo Ma, David T. Wu, and Ning Wu, "Formation of Colloidal Molecules Induced by Alternating-Current Electric Fields", Journal of the American Chemical Society 135, 7839-7842 (2013), featured in JACS Spotlights
3. Fuduo Ma, Sijia Wang, Lois Smith, and Ning Wu, "Two-dimensional Assembly of Symmetric Colloidal Dimers under Electric Fields", Advanced Functional Materials 22, 4334-4343 (2012), featured on the cover and highlighted by Materials View
Short Biosketch
Dr. Ning Wu joined Colorado School of Mines as an Assistant Professor of Chemical Engineering in fall 2010. He holds a B. Eng. in Chemical Engineering from the National University of Singapore, and a Ph. D in Chemical Engineering from Princeton University. Before joining CSM he worked at Harvard University as a postdoctoral researcher. His research interest lies in synthesizing and controlling the structures of colloidal particles at different length scales, which are important for the development of efficient photovoltaics, novel colloidal emulsifiers, multi-functional nanomotors, as well as biomedical diagnostic/therapeutic systems. He received NSF Career award 2015. His work has also been funded by NSF, DOE, NASA, and ACS-PRF. His recent work have been featured on the cover of Advanced Functional Materials, selected by spotlights in the Journal of the American Chemical Society, and published in the Proceedings of the National Academy of Sciences.