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 of intelligient lubricous biofilms, biolubrication and friction at soft polymeric interface
2

Glassy dynamics of confined colloidal suspensions

3

Manipulation, assembly and controlled release of molecules, colloids, macromolecules and supramolecular aggregates by AC-dielectrotrophoresis

4
DNA docking with functionalized colloidal probes
5

Liposome synthesis, encapsulation and manipulation

 
6
 Spray, capture and dynamics of nano-aerosols in microfluidics and porous polymeric media
 
7
 Electrowetting and interfacial hydrodynamics
Molecular Design of Intelligent Lubricious Biofilms
 
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 Molecules, 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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DNA Docking with Functionalized Collidal Probes
 
 

In collaboration with Prof. H-C Chang and the Microfluidics and Medical Diagnostic Center, we examine the DNA docking with oligo-functionalized colloidal particles and carbon nanotubes with and without applied AC-electric fields. Based on the fluorescence intensity and measured autocorrelation by using FCS, we examine the docking dynamics and hybridization kinetics of DNA-colloid complex. It is observed the application of AC-fields could significantly speed up the transport process of DNAs and colloidal probes as welll as surprisingly enhancing DNA hybridization.

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Liposome Synthesis, Encapsulation and Manipulation
 
MLV
 

This project is to investigate a hybrid phospholipid liposome system coated with biocompatible shells or nanoparticles for liposome stability and interior encapsulations of polymers/probes in the aqueous core to modulate internal rheology and controlled chemical release. Using AC-electroformation of giant unilamellar vesicles and multilamellar vesicles, macromolecules or molecular probes used to tailor the internal rheology of liposomes are encapsulated in the aqueous core of liposomes. We further examine the DEP behaviros and AC-electrokinetic manipulations of this complex systme with varied encapsulates and suspension media. We also use the microrheology techique to further examine the role of the confined, crowded geometry on the dynamical responses of encapsulated macromolecules and molecular probes in this unique hollow and deformable colloidal system.

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Spray, capture and dynamics of nano-aerosols in microfluidics and porous polymeric media
 
 

This project focuses on the filtration of submicron liquid and particle aerosols (<300 nm) in straight-channels with micron-sized dimensions, most relevant to protective filter designs against chemical and biological agents delivered in air-borne aerosols, is inadequately understood to allow intelligent designs of the monolith filters. At these small scales, filtration is complicated by Brownian fluctuation of the nano-aerosol (which is different in the bulk and within the channel), aerosol adhesion and plasticity, entrance aggregation, aerosol/wall electro-static interaction and aerosol rotation at the wall. Other than gross collection efficiency over bulk filters, there has been little in-situ characterization and understanding of these key fundamental phenomena at the micron to nanometer scales of the channel and its entrance. In this project, we examine the intra-channel and entrance nano-aerosol fluctuation by FCS, and quantify the adhesion, adsorption, and aggregation dynamics as functions of particle/channel dimension and electrostatic interaction. This is a joint project with Prof. H.-C. Chang's group at Notre Dame.

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AC-Electrowetting and Interfacial Hydrodynamics
multiring   Check back later for more info.

 

Last modified on October 20, 2008