Interfacial Soft Materials Lab | Zhu Research Group
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Research Interest and Current Projects
Research Interests
   
1
 Molecular/macromolecular structure and dynamics at surface and interface.
2
 Experimental physics of soft condense matter, colloidal dispersions, polymers and biomaterials.
3
 AC-electrokinetic and microfluidic techniques for new complex fluid structures, molecular/colloidal manipulation and assembly.
4
 Bio- and nano-tribology; mechanics of biomaterials.
 
Current Research Projects
 
1

Molecular design and Chacterization of Stimuli-Responsive Polymer Thin Films for Biolubrication, Non-fouling Coatings and Nanofiltration
2

Glassy dynamics of confined colloidal suspensions

3

Manipulation, assembly and controlled release of colloids, macromolecules and supramolecular aggregates by AC-Electric Fields

4
Nanoparticle-Lipid Membrane Interactions and Their Implications on Cytotoxicity and Drug Delivery
5

Electrowetting and interfacial hydrodynamics
   
Molecular Design of Responsive Polymer Thin Films
 
biolubrication

This project focuses on understanding and materials design of biocompatible polymer interfaces for lubricious medical surfaces and biofouling-preventive coatings, as well as for applications such as prosthetic implants, contact lenses, and drug delivery coatings. The broad perspectives are, by judicious actions of polymer surface textures and external forcing, to control friction and intermolecular interactions on demand for rational molecular materials design. This in turn may have a broad impact on health, energy and other technical areas, with the possibility of achieving more effective non-biofouling coatings, better lubricious implant surfaces and devices, and improvement in related products.

We combines the surface-initiated atom transfer radical polymerization (ATRP) combined with Langmuir-Blodgett (LB) thin film deposition to graft surface-tethered smooth stimuli-responsive polymer brushes of well controlled grafting density and brush thickness on a solid surface. We use laser single-molecule imaging and spectroscopy to examine the structural dynamics and interfacial rheological properties of protein macromolecules on the stimul-responsive polymer brush thin films with comparison to those on self-assemble monolayer, both of whose surface hydrophobicity can be varied.

Learn more about this project, click here.
 
Glassy Dynamics of Confined Colloids
   
MGR

We are interested in the confinement effect on the phase transition and mechanical stability of colloidal thin films. We use the home-built confocal SFA to study the effects of film thickness (down to 1-2 particle layers), shear excitation and surface texture on the microscopic packing configuration of confined colloids in 3-dimensions. We develop image analysis algorithm to track multi-particles’ motion simultaneously in time series, which can be directly compared to the work of computer simulation yet without simulation’s time-scale limitation. The transit structure in confined suspension will significantly affect the mobility and relaxing processes of colloids and consequently the rheological properties of entire colloidal thin films. Therefore, quantifying the change of colloidal phase structure as well as its effect on the extent of the dynamic retardation near the glass transition is a major goal of this project.

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Manipulation and Assembly of Colloids and Macromolecules by AC-Dielectrotrophoresis
 
 

We exploit the AC-electrokinetic effects in non-uniform AC-electric fields to manipulate and assemble a variety of complex fluids. In our recent work on studying the dielectrophoresis and assembly of binary latex particles, we observe strong dependence of AC-field frequency, colloidal particle size and medium conductivity on dielectrophoretic (DEP) behavior. The applicable assembly frequency window determined by the low-frequency threshold and DEP crossover frequency can be effectively tuned by varying medium conductivity and particle size, suggesting that the dynamic double-layer effect plays a critical role in the interfacial polarization of micron to sub-micron sized particles.  The segregation and structure p-DEP induced colloidal aggregation in binary suspensions are a result from combined DEP mobility and hydrodynamic diffusivity of binary particles in aqueous suspension.

Recently, we extend the DEP manipulation to micelles, liposomes and polymers. By tuning the AC-field frequency, we can effectively stretch/coil polyelectrolytes, break/assembly micelles and liposomes, as well as varying the docking of DNAs with functionalized colloidal probes, which also leads us to further understanding the AC-polarization mechanism in complex systems.

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Nanocolloid-Lipid Membrane Interactions
 
MLV
 

With the emerging of various functional nanocolloidal materials, it becomes critical to understand the interactions between nanoparticles and cell membranes in order to effectively use them for broad biomedical application yet with minimal cytotoxicity. We recently start to examine the effect of s nanoparticles (NPs) of varied composition, structure, and surface chemisty on the dynamics and morphology of supported lipid bilayers (SLBs). Above a critical NP concentration, the disruption of SLBs occurs and is possibly accompanied with the formation and rapid growth of lipid-poor regions, or so called “pores”, on NP-adsorbed SLBs or even fluid-gel phase transion of lipid membrane, which has potential implications on cytotoxicity and drug delivery

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AC-Electrowetting and Interfacial Hydrodynamics
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Last modified on Auguste 2011