Mohammadigoushki Group

Soft Matter | Fluid Dynamics | Instabilities | Rheology | NMR | Flow Visualization

Our research generally focuses on studying flow and dynamics of soft materials for applications in energy, oil & gas as well as biotechnology. The primary goal of our research is to discover new phenonemon in soft materials and to investigate the connection between molecular and macroscale properties of these systems. Towards this goal, We combine a range of experimental and theoretical techniques including Rheometry, Digital Particle Image Velocimetry, Particle Tracking Velocimetry, Fluorescence Microscopy, NMR diffusometry, and MR Velocimetry among others.

Kinetics and Microstructural Origins of Shear Banding in Wormlike Micelles:

Shear-banding, i.e. discontinuities in the velocity gradient in a flowing material, is reported in a broad range of complex fluids including polymers, grannular materials, suspensions and wormlike micelles. Wormlike micelles provide a model fluid for studies of shear banding. The goal of this project is to understand the dynamics of shear banding by connecting the macroscale behavior to molecular level parameters via a combination of 1) Highspeed flow imaging and rheology (Rheo-PTV) and 2) Rheo-NMR techniques.
Passive and Active Particle Motion in Complex Fluids: Multiphase flow of particles in complex fluids is a critical aspect in technological applications and life-science. Examples include well drilling, and hydraulic fracturing in oil-gas sector or swimming of cells and microorganisms in soil or mucus (our body). We study a range of problems that involve motion of passive particles (video in the right) or swimmers (video to the left) in viscoelastic fluids by coupling particle tracking velocimetry, particle image velocimetry, flow birefringency and computational modeling.

NMR Spectroscopy of Macromolecules and Proteins: Nuclear Magnetic Resounance (NMR) is extremely sensitive to subtle changes in microstructure of macromolecules or proteins. The goal of this research is to employ NMR based techniques that are available to us through National High Magnetic Field Laboratory (NHMFL) to scrutinize the microscale dynamics and structure of macromolecules and proteins. The figure below shows 1D NMR spectra of a viscoelastic surfactant solution at various diffusion weighting.

Extensional Rheology of Complex Fluids: Extensional rheology of complex fluids is important in a variety of industrial processes, such as coating, injection molding, extruding, and inkjet printing. We study elongational rheology of a range of complex fluids including living polymers via a combination of a custom built Capillary Breakup Extensional Rheometer (CaBER; video in the left) , Dripping onto Substrate (DoS; video on the right), and Small Light Angle Scattering techniques.