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Spirulina-templated metal microcoils with controlled helical structures for THz electromagnetic responses.

Kamata K, Piao Z, Suzuki S, Fujimori T, Tajiri W, Nagai K, Iyoda T, Yamada A, Hayakawa T, Ishiwara M, Horaguchi S, Belay A, Tanaka T, Takano K, Hangyo M - Sci Rep (2014)

Bottom Line: Spirulina varies its diameter, helical pitch, and/or length against growing environment.Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils.A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

View Article: PubMed Central - PubMed

Affiliation: 1] Iyoda Supra-Integrated Material Project, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST), 4259 Nagatsuta-Cho, Midori-Ku, Yokohama, Kanagawa 226-8503, Japan [2] Research Society for Biotemplate Technology, 4259 Nagatsuta-Cho, Midori-Ku, Yokohama, Kanagawa 226-8503, Japan.

ABSTRACT
Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

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Related in: MedlinePlus

Dependence of helical shape and handedness of μcoil on optically active response.(a), (b) Ellipticity angle spectra of μcoil-dispersion paraffin sheets were summarized into series of LH μcoils and RH μcoils as well as reference samples. All of samples contained 2 wt% in the paraffin matrices. The coil numbers and their Lfree/N values are depicted in insets. The RH μcoil shows laevorotation with ellipticity angle of opposite sign against the LH case. The intensity of ellipticity angle decreased and also the inversion frequency, where occurs the sign inversion from negative to positive for LH μcoil and opposite inversion for RH μcoil, shifted toward lower frequency region as the Lfree/N became smaller. Dispersion sheets of straight copper wire and freeze-dried LH template-2 with 54 μm in Lfree/N showed no spectral features, which ensures the optical activity specific to the metal helical microstructure. (c) Ellipticity angle spectra of LH μcoil-4 and RH μcoil-1 selected as enantiomeric pair. (d) Ellipticity angle at 1.5 THz as a function of Lfree/N. The value from the straight copper wire was depicted with parenthesis at 0 μm in pitch.
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f5: Dependence of helical shape and handedness of μcoil on optically active response.(a), (b) Ellipticity angle spectra of μcoil-dispersion paraffin sheets were summarized into series of LH μcoils and RH μcoils as well as reference samples. All of samples contained 2 wt% in the paraffin matrices. The coil numbers and their Lfree/N values are depicted in insets. The RH μcoil shows laevorotation with ellipticity angle of opposite sign against the LH case. The intensity of ellipticity angle decreased and also the inversion frequency, where occurs the sign inversion from negative to positive for LH μcoil and opposite inversion for RH μcoil, shifted toward lower frequency region as the Lfree/N became smaller. Dispersion sheets of straight copper wire and freeze-dried LH template-2 with 54 μm in Lfree/N showed no spectral features, which ensures the optical activity specific to the metal helical microstructure. (c) Ellipticity angle spectra of LH μcoil-4 and RH μcoil-1 selected as enantiomeric pair. (d) Ellipticity angle at 1.5 THz as a function of Lfree/N. The value from the straight copper wire was depicted with parenthesis at 0 μm in pitch.

Mentions: The variety of μcoils fabricated through systematic control of helical structures of Spirulina biotemplates enables us to experimentally evaluate structure-specific chiral electromagnetic responses. As references, it was confirmed that the dispersion sheets containing the straight copper wire and freeze-dried LH template-2 showed optical inactive. All of LH μcoils gave the similar spectral features of their ellipticities as the LH μcoil-1, i.e., negative sign at 0.5 THz and positive one above 1.0 THz (Fig. 5a). At the same peak frequencies, the RH μcoils exhibited opposite signs of ellipticities (Fig. 5b). The LH μcoil-4 and RH μcoil-1 were selected here as enantiomeric pair with similar Lfree/N values. The ellipticities of the enantiomeric pair obviously showed mirror-image spectra with opposite signs; +15° for LH μcoil-4, -10° for RH μcoil-1 at 2.0 THz (Fig. 5c). Separately, another sheet containing a racemic mixture of LH and RH μcoils with 1 wt% each traced the average of individual ellipticity angle spectrum, meaning no peaks with flat spectral feature (Fig. S21). The frequency showing sign inversion in ellipticity angle spectrum resulted in peak of rotation angle (Fig. S22). Therefore, it came to light that the LH μcoil emits the RH elliptical polarization and vice versa above the sign inversion frequency. That is to say, the LH μcoil shows dextrorotation and the RH one does levorotation.


Spirulina-templated metal microcoils with controlled helical structures for THz electromagnetic responses.

Kamata K, Piao Z, Suzuki S, Fujimori T, Tajiri W, Nagai K, Iyoda T, Yamada A, Hayakawa T, Ishiwara M, Horaguchi S, Belay A, Tanaka T, Takano K, Hangyo M - Sci Rep (2014)

Dependence of helical shape and handedness of μcoil on optically active response.(a), (b) Ellipticity angle spectra of μcoil-dispersion paraffin sheets were summarized into series of LH μcoils and RH μcoils as well as reference samples. All of samples contained 2 wt% in the paraffin matrices. The coil numbers and their Lfree/N values are depicted in insets. The RH μcoil shows laevorotation with ellipticity angle of opposite sign against the LH case. The intensity of ellipticity angle decreased and also the inversion frequency, where occurs the sign inversion from negative to positive for LH μcoil and opposite inversion for RH μcoil, shifted toward lower frequency region as the Lfree/N became smaller. Dispersion sheets of straight copper wire and freeze-dried LH template-2 with 54 μm in Lfree/N showed no spectral features, which ensures the optical activity specific to the metal helical microstructure. (c) Ellipticity angle spectra of LH μcoil-4 and RH μcoil-1 selected as enantiomeric pair. (d) Ellipticity angle at 1.5 THz as a function of Lfree/N. The value from the straight copper wire was depicted with parenthesis at 0 μm in pitch.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4017220&req=5

f5: Dependence of helical shape and handedness of μcoil on optically active response.(a), (b) Ellipticity angle spectra of μcoil-dispersion paraffin sheets were summarized into series of LH μcoils and RH μcoils as well as reference samples. All of samples contained 2 wt% in the paraffin matrices. The coil numbers and their Lfree/N values are depicted in insets. The RH μcoil shows laevorotation with ellipticity angle of opposite sign against the LH case. The intensity of ellipticity angle decreased and also the inversion frequency, where occurs the sign inversion from negative to positive for LH μcoil and opposite inversion for RH μcoil, shifted toward lower frequency region as the Lfree/N became smaller. Dispersion sheets of straight copper wire and freeze-dried LH template-2 with 54 μm in Lfree/N showed no spectral features, which ensures the optical activity specific to the metal helical microstructure. (c) Ellipticity angle spectra of LH μcoil-4 and RH μcoil-1 selected as enantiomeric pair. (d) Ellipticity angle at 1.5 THz as a function of Lfree/N. The value from the straight copper wire was depicted with parenthesis at 0 μm in pitch.
Mentions: The variety of μcoils fabricated through systematic control of helical structures of Spirulina biotemplates enables us to experimentally evaluate structure-specific chiral electromagnetic responses. As references, it was confirmed that the dispersion sheets containing the straight copper wire and freeze-dried LH template-2 showed optical inactive. All of LH μcoils gave the similar spectral features of their ellipticities as the LH μcoil-1, i.e., negative sign at 0.5 THz and positive one above 1.0 THz (Fig. 5a). At the same peak frequencies, the RH μcoils exhibited opposite signs of ellipticities (Fig. 5b). The LH μcoil-4 and RH μcoil-1 were selected here as enantiomeric pair with similar Lfree/N values. The ellipticities of the enantiomeric pair obviously showed mirror-image spectra with opposite signs; +15° for LH μcoil-4, -10° for RH μcoil-1 at 2.0 THz (Fig. 5c). Separately, another sheet containing a racemic mixture of LH and RH μcoils with 1 wt% each traced the average of individual ellipticity angle spectrum, meaning no peaks with flat spectral feature (Fig. S21). The frequency showing sign inversion in ellipticity angle spectrum resulted in peak of rotation angle (Fig. S22). Therefore, it came to light that the LH μcoil emits the RH elliptical polarization and vice versa above the sign inversion frequency. That is to say, the LH μcoil shows dextrorotation and the RH one does levorotation.

Bottom Line: Spirulina varies its diameter, helical pitch, and/or length against growing environment.Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils.A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

View Article: PubMed Central - PubMed

Affiliation: 1] Iyoda Supra-Integrated Material Project, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST), 4259 Nagatsuta-Cho, Midori-Ku, Yokohama, Kanagawa 226-8503, Japan [2] Research Society for Biotemplate Technology, 4259 Nagatsuta-Cho, Midori-Ku, Yokohama, Kanagawa 226-8503, Japan.

ABSTRACT
Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

Show MeSH
Related in: MedlinePlus