Complex Fluids and BioPhotonics Laboratory

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Optical Coherence Tomography (OCT)-Gravimetry-Video method for studying the drying process of colloidal system

Latex, a colloidal system of polymer particles suspended in water, is consumed in large quantities each year as waterborne coatings on various material substrates. To understand the mechanism of drying mechanism, we integrate Optical Coherence Tomography (OCT) with gravimetric and video analysis (called “OCT-Gravimetry-Video” method) to monitor the internal structure, the water evaporation rate and the appearance of a latex coating simultaneously. New drying phenomena and mechanism were provided. [H. Huang, Y. Huang, C. Zhou, W. Lau, H. D. Ou-Yang, M. S. El-Aasser]

Cell mechanics of cell division

The cortical actomyosin layer below the membrane of dividing cells and the astral microtubules of the mitotic spindle are coupled through internal feedback mechanisms that regulate the cell’s local and global mechanical properties. We study the perturbation of mitotic Hela cells with localized force and the cellular response using fluorescence imaging. [M.-T. Wei] [Collaborator: Dr. Vavylonis and Dr. Jedlicka]


Electrical origin forces such as dielectrophoresis (DEP) and AC electroosmosis (ACEO) have been widely investigated for the purpose of sample pretreatment and analysis. Recent development has witnessed that both DEP and ACEO have great potential in sample transportation, sorting, mixing, etc on microfluidic devices. We intend achieving quantification methods of DEP force and ACEO flow on an individual particle. [J. Wang; HJ Park; M.-T. Wei]

M.-T. Wei et al.Biomicrofluidics 3 012003 (2009); H. Park et al.Electrophoresis 33 2491 (2012); J. Wang et al. Electrophoresis 34 1915 (2013).

Microfluidics for bionanoparticles

Concentration of HIV viral particles in blood of adolescent and infant individuals can be below detection range.  Locally concentrating viral particles in blood samples can lead to faster detections and prognosis. [Y. Hu; C. Wentz; C. Phillips ] [Collaborators: Dr. Cheng]

Y. Hu et al. Biomedical Optics Express 4 1646 (2013).

Microrheology in living cells

Biological intracellular stresses generated by molecular motors can actively modify cytoskeletal network causing intracellular mechanical responses. We study out-of-equilibrium microrheology in living cells and correlation of the cell microrheology and the biological functions. [M.-T. Wei] [Collaborator: Dr. Ghadiali]

M.-T. Wei et. al. Optics Express 16 8594 (2008); H. C. Yalcin et al.Am J Physiol Lung Cell Mol Physiol 297 L881 (2009); H. D. Ou-yang et al. Annu. Rev. Phys. Chem. 61 421 (2010).

Nanophotonics and nanocolloid physics

We study nanophotonics, which is to develop novel materials or devices using engineered metallic nanostructures. The ability to grasp and control the optical or plasmonic effect on the nanometer scale opens new windows to applications raging from biosensing, nanomedicine to super-resolution imaging and high-density information storage. [J. Fu; L. Zhou] [Collaborators: Dr. Dierolf; Dr. Zhan]

L. Ling et. al. Optics Express 21 6618 (2013). J. Fu et. al. Optics Letters 38 3995 (2013).

Non-equilibrium active matter

In this study, we use optical tweezers, dielectrophoresis, and analytical centrifugation to look forward to erecting perfect dynamic laws for non-equilibrium systems such as living cells or active particles.

Optical bottles

We present a novel method, the optical bottle, that uses a focused laser beam to trap and analyze optically confined multiple nanoparticles. By using optical forces to compress and confine nanoparticles, we have developed a non-invasive method to study nanoparticle behavior in situ. [J. Junio]

J. Junio et al., Solid State Communications 150 1003 (2010); J. Junio et al., Optical Letter 36 1497 (2011)

Optical binding

Optical binding has been proposed to be responsible for the cluster formation of micron size dielectric spheres in coherent light fields. We use optical tweezers to study the optical binding forces and compare with theoretical results. [M.-T. Wei] [Collaborator: Dr. Ng ]

M-T Wei, et. al. SPIE Proc. 7400 (2009)

Soft Materials

We present a rheology study of associating polymers. The associating polymers are telechelic, composed of a water-soluble backbone terminated by hydrophobic moieties. In aqueous solutions, these polymers self-assemble to form micellar structures. We use a combination of the Maxwell model and the Rouse model to describe the polymer structure.

L. A. Hough et. al. PRE 73 031802 (2006); C. Y. Park et al. Rev. Sci. Instrum. 82 094702 (2011); C. Ha et al. Physica A 392 3497 (2013).