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

Kaori Kamata,Mitsuteru Ishiwara,Satoshi Horaguchi,Toshiaki Hayakawa,Keisuke Takano,Atsushi Yamada,Amha Belay,Keiji Nagai,Soichiro Suzuki,Masanori Hangyo,Zhenzi Piao,Takuo Tanaka,Tomokazu Iyoda,Takahiro Fujimori,Wataru Tajiri

doi:10.1038/srep04919

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.

Highlights

Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists
We have suggested collaborating with nature, i.e., biotemplating process, which directly borrows the natural microstructures for new material fabrications (Fig. 1)
Its helical structure is very sensitive against the environmental conditions, which should be strong advantage to exploit a variety of diameter, pitch, and handedness

Summary

Introduction

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. 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. We describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. If we can find effective factors controlling the structures from various environmental conditions, the biotemplating process would have unlimited potential and will be global strategy for material development. Development of biotemplating process using Spirulina can achieve mass production of microcoil (mcoil), which is currently manufactured by precision machining or lithography one by one. No function specific to its helical microstructure has yet been discovered

Methods

Results

Conclusion