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Sungyon Lee and Xiang Cheng: Particle self-assembly on the moving fluid-fluid interface

The ability of disparate parts to spontaneously form complex macroscopic structures is one of the hallmarks of living matter and has driven engineers and scientists alike to achieve the same feat with synthetic materials [1]. In particular, the advent of microelectronics and digital displays has led to the fabrication of 2D structures based on the directed self-assembly of mesoscopic objects on the fluid-fluid interface [2]. More recently, the research in 2D self-assembly has been extended to microscopic colloids both on flat and curved fluid-fluid interfaces [3], fueled by its potential for generating new functional materials. In the current studies, the focus is on the particles themselves, while the fluid-fluid interface remains mostly a passive site onto which particles can self-organize. The overall objective of this MRSEC Seed project is to shift the focus onto the interface itself and experimentally investigate the dynamic coupling between the fluid-fluid interface and the particle assembly. Distinct from on-going studies, the fluid-fluid interface will be allowed to dynamically deform, bringing a new level of controllability to achieve new macroscopic structures. Presently, we will focus on the dynamic particle assembly upon the expansion and shrinkage of the fluid-fluid interface, as the fluid is injected into or drained from a spatially varying channel, such as a funnel (see Figure 1(a)). In addition, we will measure the surface rheology of resultant particle-laden surfaces, in order to understand the kinetics of particle assembly on the interface.

[1] Z. Zeravcic, V.N. Manoharan and M.P. Brenner, “Colloquium: Toward living matter with colloidal particles,” Rev. Mod. Phys. 89, 031001 (2017). [2] N. Bowden, A. Terfort, J. Carbeck and G.M. Whitesides, “Self-Assembly of Mesoscale Objects into Ordered Two-Dimensional Arrays,” Science 276, 5310 (1997). [3] I.B. Liu, N. Sharifi-Mood and K.J. Stebe, “Capillary Assembly of Colloids: Interactions on Planar and Curved Interfaces,” Annu. Rev. Condens. Matter Phys. 9, 1 (2018).

National Science Foundation

Funded by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013

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