Biophotonics Laboratory
California Institute of Technology


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Xin HengXin Heng


M.S., Applied Physics, Caltech 2003, USA
B.S., Physics, with honors, Nanjing University, China, 2002

Research Projects

1) Optofluidic microscopy - A method for implementing a high resolution optical microscope on a chip
This project aims at creating an optical microscope on a microfluidic chip that contains no bulk optical elements. It is termed the Optofluidic microscope, or OFM.

There are inherent advantages of using optics in microfluidic applications. For example, light interrupts fluids negligibly and it is non-destructive to biological samples. We attempt to revolutionize the concept of microfluidic circuitry by miniaturizing this optical imaging unit while using microfluidics for sample delivery. In recent experiments, high resolution, high throughput imaging has been successfully demonstrated by using one of the most popular animal models, Caenorhabditis elegans (C. elegans). Out first prototype device has also been used to perform nematode phenotyping, in which field subtle morphological variations between different genotypes were usually qualitatively described. The advantages of OFM make it perfectly suited as a highly-automated system that requires nearly no labor-intensive observation or sample counting. More modalities such as Raman imaging, fluorescence and spectroscopy can be readily integrated into this system. We strongly believe OFM is a significant advancement in the development of the next-generation optics-lab-on-a-chip that will improve the quality of life by modernizing biomedical research and clinical testing.

2) A high resolution optofluidic microscope with a stable optical trap
In previous work, we combined OFM with microfluidics and demonstrated the first OFM prototype with C. elegans imaging. Relatively large apertures (600 nm in diameter) were used, and the resulting resolution was only comparable with a conventional microscope. In this work, we use subwavelength nanoapertures (<200nm in diameter) to demonstrate high resolution OFM. Furthermore, we choose optical tweezers as our new sample manipulation scheme. In this design, optical tweezers immobilize cells and then move them across the nanoaperture array with a constant speed. The stable optical trap is formed above an aluminum surface and the cells are able to remain in close proximity with the nanoaperture plane throughout scanning. We prove that optical trapping is a promising technique to combine with OFM. High imaging throughput of OFM can be accomplished by employing an optical trap array.

3) Homodyne based optical coherence microscopy
This project is to bridge confocal laser scanning microscope (CLSM) and optical coherence tomography (OCT) and thus create a new imaging modality in the field of tomography imaging. It is named Optical Coherence Microscope (OCM). OCM distinguishes itself from conventional OCT configurations because of its capability of delivering micron-level volumetric (3D) resolution in biomedical imaging by combining the 'gating' ability of low-coherence interferometer and the high-N.A. of CLSM imaging technique.

For more details, please refer to the website of my colleague, Zahid Yaqoob.

4) Microfluidic display
The project specifically aims at making use of the state of the art microfluidic technology to build a fluorescence display. It is a new concept that differs from any other existing scheme such as CRT, LCD and plasma display. It will be competitive in the display market because of its low cost, fast modulation and compact size.

For more details, please refer to the website of my colleague, Xiquan Cui.


Xin Heng, David Erickson, L. Ryan Baugh, Zahid Yaqoob, Paul W. Sternberg, Demetri Psaltis and Changhuei Yang, Optofluidic microscopy- a method for implementing a high resolution optical microscope on a chip, Lab on a Chip 6 (10): 1274 - 1276, 2006.

Xin Heng, Xiquan Cui, David Knapp, Jigang Wu, Zahid Yaqoob, E. J. McDowell, Demetri Psaltis and Changhuei Yang, Determining the resolution limit of nano aperture based optical imaging or sensing device, Optics Express 14 (22): 10410 - 10425, 2006.

For other co-written articles of mine, please check the websites of my colleagues or the 'Publications' section.