Xiang Cheng
University of Minnesota, MN·Engineering
Tiny swimmers and moving fluids shape life at the microscale. Bacteria spin corkscrew-shaped tails to swim, algae and cilia beat to push fluid, and dense crowds of swimming cells stir up swirling flows.
- Fields
Engineering
Biophysics
Physics
- Topics
active matter
bacterial turbulence
active fluids
- Grants
- 6 known grants, through Jan 2031
What they work on
- Engineer a fluorescent bacterial strain with tunable swimming speed and tumble frequency, and image single cells inside dense suspensions to link individual swimming to local turbulent flow and test competing active-matter theories.
- Control bacterial turbulence by combining on-demand tuning of individual swimming with geometric confinement, in order to study how turbulence starts and how energy cascades, and to develop a light-tunable optorheological fluid.
- Determine how hydrodynamic interactions, hook elasticity and motor torque fluctuations synchronize Escherichia coli flagella into a bundle, using scaled physical models, engineered mutants and immersed-boundary simulations.
- Map the 3D flow around beating flagella of wild-type and mutant Chlamydomonas reinhardtii algae with high-speed tracking holographic microscopy, and connect abnormal flagellar structure to defects in fluid transport.
- Build a machine-learning-guided numerical model of algal flagellar flow to study the efficiency, optimization and synchronization of flagellar beating and the behavior of algal suspensions.
- Test how thin elastic, mechanically heterogeneous and non-Newtonian substrates change drop splashing, linking the onset of splashing to impact pressure distribution, with input from industrial coating engineers.
More about the research
In all of these, the physics of fluid flow decides what happens. This research program builds physical model systems and new imaging methods to understand how small moving structures interact with the fluid around them. It asks how motion at the level of one cell or one filament gives rise to flows at much larger scales. The work is organized around three biological fluid problems: bacterial turbulence, bacterial flagellar bundles, and the flow made by beating algal flagella. A separate industry-linked project studies how liquid drops hit surfaces.
Why it matters
Understanding flagellar flow could help explain how faulty cilia cause ciliopathies, disorders that impair processes such as airway mucus clearance, and point toward ways to restore fluid transport. Insights into bacterial swimming bear on microbial motility and chemotaxis. Controllable active fluids and light-tunable viscosity could inform targeted drug delivery, soft robotics and advanced manufacturing. Substrate-controlled drop impact could improve industrial multi-layer coatings and printing on soft surfaces.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
Closest labs
On Shun Pak
Santa Clara University, CA·Engineering
Use robophysical models, robots that mimic swimming bacteria, together with theory to determine how non-Newtonian fluid behaviors such as shear thinning or elasticity change bacterial swimming.
Nuris Figueroa-Morales
University of Colorado Boulder, CO·Physics·Early-career
Derive a slender body theory, a model of thin moving filaments, for a single bacterial flagellum in a nematic liquid crystal, and test it with experiments and simulations of the Ericksen-Leslie and Beris-Edwards fluid models.
Harishankar Manikantan
University of California-Davis, CA·Engineering·Early-career
Use asymptotic theory to calculate hydrodynamic interactions between pairs of particles in realistic non-Newtonian interfaces, including membranes and monolayers whose resistance to flow changes with deformation.
The school
University of Minnesota: 88 labs on PI Pages, $1.4B a year on research, 722 research doctorates a year.
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