My group studies soft materials physics, biophysics and fluid mechanics in experiments. We are particularly interested in emergent flow phenomena in soft materials and biological systems and aim to understand their microscopic structural and dynamic origins. Our research is driven by fundamental questions in statistical and biological physics, as well as engineering issues related to the design and processing of soft and bio-materials.
In our research, we apply state-of-the-art imaging techniques including high-speed photography, confocal microscopy and digital holographic microscopy to image fluid flow at small spatial scales and fast time scales. By integrating the concepts from transport phenomena, thermodynamics, statistical mechanics, colloidal and interfacial science, rheology and biochemical engineering, we develop quantitative understandings of the intriguing flow properties of soft matter and bio-materials under both equilibrium and non-equilibrium conditions. Some recent examples of our research include the study of swimming microorganisms in complex environments, the collective dynamics of dense bacterial suspensions, the rheology of colloidal suspensions, the dynamics of drop impact, and the emergent collective phenomena of granular robotic systems. We collaborate broadly with theory and simulation groups within and outside the University of Minnesota.
T.-P. Sun, F. Alvarez-Novoa, K. Andrade, P. Gutierrez, L. Gordillo, and X. Cheng, “Stress distribution and surface shock wave of drop impact”, Nat. Commun. 13, 1703 (2022). (Selected in Editors’ Highlights)
S. Kamdar, S. Shin, P. Leishangthem, L. F. Francis, X. Xu, and X. Cheng, “The colloidal nature of complex fluids enhances bacterial motility”, Nature 603, 819 (2022).
Y. Qiao, X. Ma, Z. Liu, M. A. Manno, N. C. Keim, and X. Cheng, “Tuning the rheology and microstructure of particle-laden fluid interfaces with Janus particles”, J. Colloid Interf. Sci. 618, 241 (2022).
X. Cheng, T.-P. Sun, and L. Gordillo, “Drop Impact Dynamics: Impact Force and Stress Distributions”, Annu. Rev. Fluid Mech. 54, 57 (2022).
Z. Liu, W. Zeng, X. Ma, and X. Cheng, “Density Fluctuations and Energy Spectra of 3D Bacterial Suspensions”, Soft Matter 17, 10806 (2021). (Featured on the front cover)
Y. Peng, Z. Liu, and X. Cheng, “Imaging the emergence of bacterial turbulence: phase diagram and transition kinetics”, Sci. Adv. 7, eabd1240 (2021).
S. Guo, D. Samanta, Y. Peng, X. Xu, and X. Cheng, "Symmetric shear banding and swarming vortices in bacterial 'superfluids'", Proc. Natl. Acad. Sci. USA 115, 7212 (2018).
Y. Peng, L. Lai, Y.-S. Tai, K. Zhang, X. Xu, and X. Cheng, “Diffusion of ellipsoids in bacterial suspensions”, Phys. Rev. Lett. 116, 068303 (2016). (Selected as “Editors’ Suggestion”)
B. Zhang and X. Cheng, “Structures and dynamics of glass-forming colloidal liquids under spherical confinement”, Phys. Rev. Lett. 116, 098302 (2016). (Selected as “Editors’ Suggestion” with Synopsis)
R. Zhao, Q. Zhang, H. Tjugito, and X. Cheng, "Granular impact cratering by liquid drops: Understanding raindrop imprints through an analogy to asteroid strikes", Proc. Natl. Acad. Sci. USA 112, 342 (2015).
X. Cheng, J. H. McCoy, J. N. Israelachvili, and I. Cohen, “Imaging the Microscopic Structure of Shear Thinning and Thickening Colloidal Suspensions”, Science 333, 1276 (2011)