Dr. Jing Wang Profile

Dr. Jing Wang

MEMS Engineer at Calient Technologies

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Publications (2)

Proceedings Article | 19 February 2007 Paper

Development and applications of an optical tweezer-based microrheometer: case studies of biomaterials and living cells

Jing Wang, Huseyin Yalcin, Angela Lengel, Corey Hewitt, H. Daniel Ou-Yang

Proceedings Volume 6441, 644112 (2007) https://doi.org/10.1117/12.701324

KEYWORDS: Particles, Confocal microscopy, Anisotropy, Microscopes, Imaging systems, Optical tweezers, Phase shifts, Silica, Calibration, Mirrors

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The investigation of mechanical properties of living biological cells and biomaterials is challenging because they are inhomogeneous and anisotropic at microscopic scales, and often time-dependent over a broad time scale. Through three case studies of biomaterials and living cells, we demonstrate that a novel, oscillating optical tweezer-based imaging microrheometer developed recently in our laboratory has overcome many technical barriers posed by the complexity of biological systems. In this paper, we present the working principle, system setup and calibration of the imaging microrheometer, and report the groundbreaking results of the three applications: gelation dynamics of cross-linkable hyaluronan acid (HA) hydrogels; Mechanical in-homogeneity and anisotropy in purified microtubule networks; and effects of drug treatment and temperature variation on the mechanical properties of in vitro human alveolar epithelial cells. In each case, micro beads inserted in the materials, or attached to the cell membrane were used as probes for optical trapping. The probe particle was set into a forced harmonic oscillation by oscillating optical tweezers. Position sensing optics and phase lock-in signal processing allow the determination of the amplitude and phase shift of the particle motion at high sensitivity. The complex mechanical modulus G^* is then calculated from the amplitude and the phase shift. The rheometer system is capable of measuring dynamic local mechanical moduli in the broad frequency range of 1.3-1000 Hz at a sampling rate of 2 data point per second across a wide dynamic range (1~20,000 dyne/cm²). Integration of the rheometer system with spinning disk confocal microscopy enables the study of micromechanical properties and the microstructure of the sample simultaneously. Combination of dual-axis, piezo-electric activated mirror and 2-D position sensing detector gives the rheometer system the capability of investigating mechanical anisotropy in highly structured biological samples.

Proceedings Article | 11 September 2006 Paper

The design and biological applications of dual-beam oscillating optical tweezer-based imaging cytorheometer

H. D. Ou-Yang, J. Wang

Proceedings Volume 6326, 63261O (2006) https://doi.org/10.1117/12.681266

KEYWORDS: Particles, Optical tweezers, Confocal microscopy, Lung, Optical amplifiers, Polymers, Spatial resolution, Objectives, Microscopes, Calibration

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Because of its non-invasive nature, optical tweezers have emerged as a popular tool for the studies of complex fluids and biological cells and tissues. The capabilities of optical tweezer-based experimental instruments continue to evolve for better and broader applications, through new apparatus designs and integrations with microscopic imaging techniques. In this paper, we present the design, calibration and applications of a powerful microrheometer that integrates a novel high temporal and spatial resolution dual-beam oscillating optical tweezer-based cytorheometer (DOOTC) with spinning disk confocal microscopy. The oscillating scheme detects the position of micron-size probe particles via a phase-sensitive lock-in amplifier to greatly enhance sensitivity. The dual-beam scheme ensures that the cytorheometer is insensitive to sample specimen background parameter variances, and thus enables the investigation of micromechanical properties of biological samples, which are intrinsically inhomogeneous. The cytorheometer system is demonstrated to be capable of measuring dynamic local mechanical moduli in the frequency range of 0.1-150 Hz at up to 2 data point per second and with nanometer spatial resolutions, while visualizing and monitoring structural properties in situ. We report the results of system applications in the studies of bovine skin gelatin gel, purified microtubule assemblies, and human alveolar epithelial cells. The time evolution of the storage moduli G' and the loss moduli G'' of the gel is recorded for undisturbed gel-forming process with high temporal resolution. The micromechanical modulus G* of polymerized microtubule network as a function of frequency are shown to be both inhomogeneous and anisotropic consistent with local structures revealed by confocal imaging. The mechanical properties of A549 human lung cells as a function of temperature will be reported showing significant decrease in cell stiffness at higher temperature.

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