Confocal Brillouin microscopy for three-dimensional mechanical imaging

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Acoustically induced inelastic light scattering, first reported in 1922 by Brillouin1, allows non-contact, direct readout of the viscoelastic properties of a material and has widely been investigated for material characterization2, structural monitoring3 and environmental sensing4. Extending the Brillouin technique from point sampling spectroscopy to imaging modality5 would open up new possibilities for mechanical imaging, but has been challenging because rapid spectrum acquisition is required. Here, we demonstrate a confocal Brillouin microscope based on a fully parallel spectrometer—a virtually imaged phased array—that improves the detection efficiency by nearly 100-fold over previous approaches. Using the system, we show the first cross-sectional Brillouin imaging based on elastic properties as the contrast mechanism and monitor fast dynamic changes in elastic modulus during polymer crosslinking. Furthermore, we report the first in situ biomechanical measurement of the crystalline lens in a mouse eye. These results suggest multiple applications of Brillouin microscopy in biomedical and biomaterial science.

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Figure 1: Principle and schematic of the experimental set-up.
Figure 2: Brillouin spectra of various samples.
Figure 3: Cross-sectional Brillouin image of an intraocular lens.
Figure 4: Real-time monitoring during UV-induced crosslinking of polymer.
Figure 5: In situ characterization of the crystalline lens in a mouse eye.


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This work was supported by the US Department of Defense (FA9550-04-1-0079) and the Center for Integration of Medicine and Innovative Technologies (CIMIT). We thank P. Kim for preparing the eye sample, C.P. Lin for lending us the CCD camera, and I.E. Kochevar and R.W. Redmond for helpful comments.

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Correspondence to Seok Hyun Yun.

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Scarcelli, G., Yun, S. Confocal Brillouin microscopy for three-dimensional mechanical imaging. Nature Photon 2, 39–43 (2008) doi:10.1038/nphoton.2007.250

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