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Self-assembly of amorphous calcium carbonate microlens arrays.

Lee K, Wagermaier W, Masic A, Kommareddy KP, Bennet M, Manjubala I, Lee SW, Park SB, Cölfen H, Fratzl P - Nat Commun (2012)

Bottom Line: The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant.CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms.This shows that advanced optical materials can be generated by a simple mineral precipitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam 14424, Germany.

ABSTRACT
Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO(3) microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation.

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Characterization of the focal length of the microlens array.(a,b) Fluorescence and brightfield confocal images of the microlens array and (c,d) characterization of the focal length of the microlenses. (a) x–y plane image of the microlens array resulting from the overlay of the brightfield image (grey scale) showing the microlenses, and the fluorescence image (green) showing the fluorescently labelled chitosan coating of the microscope coverslip. The brightfield and fluorescence images were recorded simultaneously by illumination/excitation at 488 nm and collection at 488 and 530 nm (± 25 nm), respectively. The circular dashed line shows the localization of a microlens in the array. (b) x–z plane image that represents a cross-section through a stack of images taken at different depths in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thick dashed line is aligned with the fluorescence from the chitosan coating and corresponds to the glass surface. The thin dashed line (semicircle) indicates the microlens curved surface. (c) x–y plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses, at a depth in the sample equal to their focal length. Image c corresponds to the depth at which a dashed line on image d has been drawn. (d) x–z plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses. The image results from a cross-section taken through a stack of images recorded at different depth in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thin dashed vertical lines in a and b (c and d, respectively) are a guide to the eye to match the images in the x-direction. The diagram in the middle of the figure shows a schematic of the confocal microscope with one microlens (grey filled semicircle) on a chitosan-coated (green line) cover glass (white box) and the beam path (red dotted lines).
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f3: Characterization of the focal length of the microlens array.(a,b) Fluorescence and brightfield confocal images of the microlens array and (c,d) characterization of the focal length of the microlenses. (a) x–y plane image of the microlens array resulting from the overlay of the brightfield image (grey scale) showing the microlenses, and the fluorescence image (green) showing the fluorescently labelled chitosan coating of the microscope coverslip. The brightfield and fluorescence images were recorded simultaneously by illumination/excitation at 488 nm and collection at 488 and 530 nm (± 25 nm), respectively. The circular dashed line shows the localization of a microlens in the array. (b) x–z plane image that represents a cross-section through a stack of images taken at different depths in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thick dashed line is aligned with the fluorescence from the chitosan coating and corresponds to the glass surface. The thin dashed line (semicircle) indicates the microlens curved surface. (c) x–y plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses, at a depth in the sample equal to their focal length. Image c corresponds to the depth at which a dashed line on image d has been drawn. (d) x–z plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses. The image results from a cross-section taken through a stack of images recorded at different depth in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thin dashed vertical lines in a and b (c and d, respectively) are a guide to the eye to match the images in the x-direction. The diagram in the middle of the figure shows a schematic of the confocal microscope with one microlens (grey filled semicircle) on a chitosan-coated (green line) cover glass (white box) and the beam path (red dotted lines).

Mentions: The light path through an ACC microlens array and the focal length are characterized by confocal microscopy as shown in Fig. 3 (ref. 26). Figure 3c shows 11 spots corresponding to the light of a collimated laser beam focused at the back focal plane of the microlens array as shown in Fig. 3a. The beam waists at the focal plane of the microlenses were uniform in size and smaller than 1.2 μm (measured at full width at 1/e2). The x–z plane images in Fig. 3b,d show the position of the chitosan coating at the surface of the microlenses in contact with the microscope coverslip and the converging light path at the back plane of the microlenses, respectively. To calculate the focal length of the microlenses, we measured their thickness by atomic force microscopy line scans and the distance from the back plane of the microlenses and the focused point (Supplementary Fig. S5). We measured a focal length of 7.2±0.3 μm. The focal length of the microlenses focusing in the glass coverslip was calculated using the relation, 1 where R=3.1±0.2 μm is the radius of curvature calculated based on the geometry of 11 microlenses measured by atomic force microscopy line scans, and nglass and nACC are refractive indices of glass (1.50) and ACC (1.58, taken from the measured value of 1.5791–1.5830 by Merten and group27), respectively. Entering these parameters into equation (1), we find f=8.0±0.5 μm.


Self-assembly of amorphous calcium carbonate microlens arrays.

Lee K, Wagermaier W, Masic A, Kommareddy KP, Bennet M, Manjubala I, Lee SW, Park SB, Cölfen H, Fratzl P - Nat Commun (2012)

Characterization of the focal length of the microlens array.(a,b) Fluorescence and brightfield confocal images of the microlens array and (c,d) characterization of the focal length of the microlenses. (a) x–y plane image of the microlens array resulting from the overlay of the brightfield image (grey scale) showing the microlenses, and the fluorescence image (green) showing the fluorescently labelled chitosan coating of the microscope coverslip. The brightfield and fluorescence images were recorded simultaneously by illumination/excitation at 488 nm and collection at 488 and 530 nm (± 25 nm), respectively. The circular dashed line shows the localization of a microlens in the array. (b) x–z plane image that represents a cross-section through a stack of images taken at different depths in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thick dashed line is aligned with the fluorescence from the chitosan coating and corresponds to the glass surface. The thin dashed line (semicircle) indicates the microlens curved surface. (c) x–y plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses, at a depth in the sample equal to their focal length. Image c corresponds to the depth at which a dashed line on image d has been drawn. (d) x–z plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses. The image results from a cross-section taken through a stack of images recorded at different depth in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thin dashed vertical lines in a and b (c and d, respectively) are a guide to the eye to match the images in the x-direction. The diagram in the middle of the figure shows a schematic of the confocal microscope with one microlens (grey filled semicircle) on a chitosan-coated (green line) cover glass (white box) and the beam path (red dotted lines).
© Copyright Policy - open-access
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f3: Characterization of the focal length of the microlens array.(a,b) Fluorescence and brightfield confocal images of the microlens array and (c,d) characterization of the focal length of the microlenses. (a) x–y plane image of the microlens array resulting from the overlay of the brightfield image (grey scale) showing the microlenses, and the fluorescence image (green) showing the fluorescently labelled chitosan coating of the microscope coverslip. The brightfield and fluorescence images were recorded simultaneously by illumination/excitation at 488 nm and collection at 488 and 530 nm (± 25 nm), respectively. The circular dashed line shows the localization of a microlens in the array. (b) x–z plane image that represents a cross-section through a stack of images taken at different depths in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thick dashed line is aligned with the fluorescence from the chitosan coating and corresponds to the glass surface. The thin dashed line (semicircle) indicates the microlens curved surface. (c) x–y plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses, at a depth in the sample equal to their focal length. Image c corresponds to the depth at which a dashed line on image d has been drawn. (d) x–z plane image of the light from a collimated laser beam (650±10 nm) focused by the microlenses. The image results from a cross-section taken through a stack of images recorded at different depth in the sample. The plane shown corresponds to the position indicated by a solid white line on image a. The thin dashed vertical lines in a and b (c and d, respectively) are a guide to the eye to match the images in the x-direction. The diagram in the middle of the figure shows a schematic of the confocal microscope with one microlens (grey filled semicircle) on a chitosan-coated (green line) cover glass (white box) and the beam path (red dotted lines).
Mentions: The light path through an ACC microlens array and the focal length are characterized by confocal microscopy as shown in Fig. 3 (ref. 26). Figure 3c shows 11 spots corresponding to the light of a collimated laser beam focused at the back focal plane of the microlens array as shown in Fig. 3a. The beam waists at the focal plane of the microlenses were uniform in size and smaller than 1.2 μm (measured at full width at 1/e2). The x–z plane images in Fig. 3b,d show the position of the chitosan coating at the surface of the microlenses in contact with the microscope coverslip and the converging light path at the back plane of the microlenses, respectively. To calculate the focal length of the microlenses, we measured their thickness by atomic force microscopy line scans and the distance from the back plane of the microlenses and the focused point (Supplementary Fig. S5). We measured a focal length of 7.2±0.3 μm. The focal length of the microlenses focusing in the glass coverslip was calculated using the relation, 1 where R=3.1±0.2 μm is the radius of curvature calculated based on the geometry of 11 microlenses measured by atomic force microscopy line scans, and nglass and nACC are refractive indices of glass (1.50) and ACC (1.58, taken from the measured value of 1.5791–1.5830 by Merten and group27), respectively. Entering these parameters into equation (1), we find f=8.0±0.5 μm.

Bottom Line: The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant.CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms.This shows that advanced optical materials can be generated by a simple mineral precipitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam 14424, Germany.

ABSTRACT
Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO(3) microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation.

Show MeSH
Related in: MedlinePlus