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Nanotechnology Seminar, Wednesday, March 13th, 12:00
IKI Auditorium, Building 51, room 015
Cryogenic-Scanning Electron Microscopy (cryo-SEM): How can it contribute to your research?
Benjamin Palmer
Chemistry Department, Ben-Gurion University of the Negev
Abstract:
We present an overview of Cryogenic-Scanning Electron Microscopy (cryo-SEM) - a state of the art electron imaging technique which enables high resolution imaging of nanometer scale features in fully hydrated samples. In conventional SEM, biological samples and soft materials must be dehydrated to be imaged at high vacuum, which often leads to alterations in the native structure of the materials. Cryo-SEM combines cryo-preservation techniques with high-resolution SEM, enabling biological tissues and soft, wet-materials to be imaged in a “close-to-life" state. The cryo-SEM technique is having a transformative impact in life sciences, bio-medical and soft matter research.
We illustrate the benefits of cryo-SEM with examples from the author's own work on natural optical systems (1, 2) where cryo-SEM was used to provide a rationalization for two of nature's most remarkable visual systems: the concave-mirrored eyes of the scallop (3) and the reflecting compound eyes of crustaceans (4). These visual systems are extremely unusual as they use mirrors rather than lenses to form images. The mirrors are formed from stacks of organic crystals interspersed with cytoplasm arranged in the form of a Bragg reflector. By imaging the samples in a close-to-life state using cryo-SEM, we show how the function of the eyes depend on the ability of the organisms to exquisitely control the hierarchical organization of the mirrors from the structure and morphology of the substituent reflecting organic crystals at the nanoscale to the overall shape of the mirrors at the millimeter scale.
Finally, we discuss the plans to establish a cryo-SEM facility at BGU and suggest future directions and possible applications of cryo-SEM in both life science and materials science.
1. B. A. Palmer, D. Gur, S. Weiner, L. Addadi, D. Oron, The organic crystalline materials of vision: structure-function considerations from the nanometer to the millimeter scale. Adv. Mater. 30, 1800006 (2018).
2. D. Gur, B. A. Palmer, S. Weiner, L. Addadi, Light manipulation by guanine crystals in organisms: biogenic scatterers, mirrors, multilayer reflectors and photonic crystals. Adv. Func. Mater. 1603514, (2017).
3. B. A. Palmer et al., The image-forming mirror in the eye of the scallop. Science 358, 1172 (2017).
4. B. A. Palmer et al., Optically functional isoxanthopterin crystals in the mirrored eyes of decapod crustaceans. Proc. Natl. Acad. Sci. U.S.A. 115, 2299 (2018).
