Spiral Photonic Actuator
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Spiral Photonic Actuator K.-Y. Jin,1 S.-K. Park,1 J.-H. Jang,2 C. Y. Koh,2 M. J. Graham,3 S.-J. Park,1 C. Nah,1 M.-H. Lee,1 S. Z. D. Cheng,3 E. L. Thomas2 , and K.-U. Jeong,1,2,3 1 Polymer Materials Fusion Research Center and Department of Polymer-Nano Science & Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756, South Korea. 2 Institute for Soldier Nanotechnologies and Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA. 3 Department of Polymer Science, The University of Akron, Akron, OH, USA.
ABSTRACT There has been a significant effort to create spiral sensors by changing either the periodic dspacing of the structure or the dielectric constants of the materials by combining the multifaceted environmental responsiveness of polymer hydrogels with dielectrical structures.1 Reversible spiral switches with dimensional functionalities that respond to chemical environment were constructed. When the spiral photonic actuator was swollen in hydrophilic acetic acid, right-handed spiral structures are formed, while the spiral photonic actuator was swollen in hydrophobic hexane, left-handed spiral structures are formed. All actuators returned back to the transparent planar state after deswelling processes. These reversible spiral photonic actuators can be applied in the application of mechanical actuators, electrical devices, and optical components. INTRODUCTION Soft polymeric materials have been widely used to fabricate intelligent soft materials and complex structures for various practical applications. Examples include photonic crystals,2-6 actuators,7-11 and spiral structures,12-17 which are of particular interests for the next generation of biological and electro-optical technologies. The three-dimensional (3D) structure is applicable to many important geometric structures in biological polymers such as proteins and deoxyribonucleic acid. In addition to biology, spiral structures have been intensively studied and developed in electro-optical material science and technology.18-20 The simplest bio-mimetic actuator is the 1D cantilever. Among many materials, polymers have been key building blocks in the fabrication of actuator because of their ability to change shape and size due to environmental changes such as ionic character, pH, temperature and solvent.21-25 One of the most well known photonic crystals is the opal which has a periodic structure. The regular photonic crystals can affect the propagation of electromagnetic waves in the same way as the periodic potential in a semiconductor crystal affects the motion of electrons, by defining allowed and forbidden electronic energy bands.26 The absence of allowed propagating modes for a range of wavelengths inside the structures gives rise to distinct optical phenomena such as inhibited spontaneous emission, and lossless reflection enabling low-loss-waveguiding.27 Recently, there has been significant effort put into creating photonic actuators by changing either the periodic d-spacing of the
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