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Microsystems for Fluorescent Spectroscopy of Cells

Sponsor: NSF ECCS

Light emitted from fluorescent proteins and nanomaterials provides important information for biologists to elucidate genetic transcription in cells, protein bindings at cell membranes, and, molecular-level physiological properties of tissue. A technological breakthrough in biophotonics and molecular imaging significantly advances scientific knowledge leading to drug discovery and disease prevention. This research has developed a novel device for the purpose of establishing a miniature biophotonic flow cytometry technology for point-of-care disease diagnostics. Our device consists of a soft grating material repeatedly stretched by a micromachine fabricated on a silicon chip and is optically coupled with the interrogation zone of a microfluidic flow channel device. Changing its light dispersing property with mechanical strain, the soft material permits very fast and sensitive wavelength tuning for spectral differentiation of fluorescently labeled biological particles flowing through the channel. The research team aims to extend this technology to precisely differentiate prostate cancer stem cells, which state-of-the-art cancer biology research has identified as highly suspected culprits of the life-threatening disease.


SEM image of on-chip strain-tunable soft polymer nano-grating optical filter. The device is coupled with a microfluidic chamber via an optical fiber to achieve high-speed, high-sensitivity fluorescence spectral acquisition for detecting fluorescently labeled cells and biophotonic particle flows.


Illustrations of the device operation for spectroscopic measurements.  (a) The MEMS comb drive actuators stretch the elastomeric grating causing the optical diffraction angle to dynamically vary. The slit in front of the detector only allows the intensity of a narrow spectral band of the dispersed light to be detected. (b) Image of the microbridge with grating imprint at initial state. (c) Image of the microbridge stretched to alter the grating spacing.

References:

Y.-C. Tung and K. Kurabayashi, “Nanoimprinted Strain-Controlled Elastomeric Gratings for Optical Wavelength Tuning,” Appl. Phys. Lett., 86, 161113 2005.

S.C. Truxal, Y.-C. Tung, and K. Kurabayashi, “High-speed deformation of soft lithographic nanograting patterns for ultrasensitive optical spectroscopy,” Appl. Phys. Lett., 92, 051116, 2008.

S.C. Truxal, Y.-C. Tung, and K. Kurabayashi, “A flexible nanograting integrated onto silicon micromachines by soft lithographic replica molding and assembly,” IEEE J. Microelectromechanical Systems, 17, 393- 401, 2008.

N.-T. Huang, S.C. Truxal, Y.-C. Tung, A. Hsiao, S. Takayama, and K. Kurabayashi, “High-speed tuning of visible laser wavelength using a nanoimprinted grating optical tunable filter,” Appl. Phys. Lett., 95, 211106, 2009.

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