Complex Fluids: Dynamics of Inclusions and Microrheology

Gold nanorods in wormlike micelle solutions under shear assemble into ordered structures that depend on the micelle phase. Full paper by Mhanna, et al.

The dynamics of complex fluids is a key area of study in the field of soft matter.  In collaboration with the Leheny Lab at JHU, we have developed new approaches that use tailored magnetic and other nanoparticles as dynamical probes to study the properties of such systems. Current projects include the study of active nematic liquid crystals driven by external forces and the influence of shear on the ordering of colloidal nanorods in worm-like micelle solutions.  These approaches have also enabled us to study a variety of other important phenomena, including how the interactions of magnetic nanoparticles with nematic liquid crystals can lead to a variety of surprising “lift” forces that hold promise for new methods of manipulating magnetic colloids, and also microrheological studies of complex fluids in confined geometries, including protein layer formation at aqueous interfaces.

  1. Phase-dependent shear-induced order of nanorods in isotropic and nematic wormlike micelle solutions, R. Mhanna, J. Lee, S. Narayanan, D. H. Reich, and R. L. Leheny, Nanoscale 11, 7875-7884 (2019).
  2. Colloidal transport within nematic liquid crystals with arrays of obstacles, K. Chen, O. J. Gebhardt, R. Devendra, G. Drazer, R. D. Kamien, D. H. Reich, and R. L. Leheny,  Soft Matter 14, 83-91 (2018).
  3. Anisotropic colloidal transport and periodic stick-slip motion in cholesteric finger textures, K. Chen, L. P. Metcalf, D. P. Rivas, D. H. Reich and R. L. Leheny, Soft Matter 11:4189-4196 (2015).
  4. Anisotropic Stokes drag and dynamic lift on cylindrical colloids in a nematic liquid crystal, J. B. Rovner, C. Lapointe, D. H. Reich, and R. L. Leheny, Rev. Lett.105, 228301 (2010).
  5. Elastic torque and the levitation of metal wires by a nematic liquid crystal, C. Lapointe, A. Hultgren, D. M. Silevitch, E. J. Felton, D. H. Reich, and R. L. Leheny, Science303, 652-655 (2004).