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Xiang Cheng: Using confocal microscopy to study the dynamics and rheology of supercooled colloidal liquids under confinement


Confocal microscopy showing a cross-section and a 3D reconstruction of a colloidal liquid confinedin a cavity and SEM showing pinned particles at boundary. Colloidal particles are made of PMMA

(a) and (b) Confocal microscopy showing a cross-section and a 3D reconstruction of a colloidal liquid confinedin a cavity. (c) SEM showing pinned particles at boundary. Colloidal particles are made of PMMA.

Understanding the nature of the glass transition is one of the most challenging problems in materials science. Although ubiquitous and technically important, glasses still elude a comprehensive and well-accepted theoretical explanation. A molecular glass forms when the temperature of a liquid is quickly quenched below its glass transition temperature. The transition between a liquid and a glass is reminiscent of the well-studied thermodynamic phase transition. This similarity has inspired intensive research into the topic, however decades’ research has not been able to unambiguously identify static correlation and structural signature in supercooled liquids going through the glass transition. Cheng’s project will adapt a new strategy proposed recently in theory, which holds promise to reveal a novel static correlation in the glass transition in experiments.

Cheng will use confocal microscopy to investigate the dynamics of supercooled colloidal liquids under strong confinement. Previous studies have shown that supercooled colloidal liquids exhibit many hallmarks of molecular glass-forming liquids and thus serve as an excellent model for probing the glass transition. The research goals are two-fold: i. Fundamentally, Cheng will directly verify the static correlation proposed by the random first-order transition theory (RFOT). ii. Practically, Cheng will investigate the rheological properties of confined colloidal liquids, which have potential impact in technical applications such as the design of new lubricants and coating liquids for microelectromechanical systems (MEMS).





The University is funded through the National Science Foundation MRSEC Program, Award DMR-1420013


Contact Information

UMN MRSEC

435 Amundson Hall, 421 Washington Ave. SE, Minneapolis, MN, 55455

P: 612-626-0713 | F: 612-626-7805