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High-throughput measurement of elastic moduli of microfibers by rope coiling

Professor Anderson H.C. Shum, professor and Dr. Yuan Liu, postdoctoral fellow, from the Department of Mechanical Engineering (HKU), have collaborated with scientists Professor Howard A. Stone, Dr. Janine K. Nunes (both from Princeton University) and Dr. Jack Lo (KFUPM) to develop a novel and promising method for assessing the flexibility of elastic microfibers at high throughput. The research was recently published in the prestigious scientific journal Proceedings of the National Academy of Sciences (PNAS) in March 2024.

Details of the publication:

“High-throughput measurement of elastic moduli of microfibers by rope coiling”

Yuan Liu, Jack H. Y. Lo, Janine K. Nunes, Howard A. Stone, and Ho Cheung Shum


There are many fields where it is of interest to measure the elastic moduli of tiny fragile fibers, such as filamentous bacteria, actin filaments, DNA, carbon nanotubes, and functional microfibers. The elastic modulus is typically deduced from a sophisticated tensile test under a microscope, but the throughput is low and limited by the time-consuming and skill-intensive sample loading/unloading. Here, we demonstrate a simple microfluidic method enabling the high-throughput measurement of the elastic moduli of microfibers by rope coiling using a localized compression, where sample loading/unloading are not needed between consecutive measurements. The rope coiling phenomenon occurs spontaneously when a microfiber flows from a small channel into a wide channel. The elastic modulus is determined by measuring either the buckling length or the coiling radius. The throughput of this method, currently 3,300 fibers per hour, is a thousand times higher than that of a tensile tester. We demonstrate the feasibility of the method by testing a nonuniform fiber with axially varying elastic modulus. We also demonstrate its capability for in situ inline measurement in a microfluidic production line. We envisage that high-throughput measurements may facilitate new applications such as screening or sorting by mechanical properties and real-time control during production of microfibers.

Note: Pictures are reproduced under the terms of the CC-BY license. [Proc. Natl. Acad. Sci. U.S.A. 121, e2303679121, 2024]

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