Two photon polymerization (TPP) lithography has been established as a powerful tool to develop 3D fine structures of polymer materials, opening up a wide range applications such as micro-electromechanical systems (MEMS). TPP lithography is also promising for 3D micro fabrication of nanocomposites embedded with nanomaterials such as metal nanoparticles. Here, we make use of TPP lithography to fabricate 3D micro structural single wall carbon nanotube (SWCNT)/polymer composites. SWCNTs exhibit remarkable mechanical, electrical, thermal and optical properties, which leads to enhance performances of polymers by loading SWCNTs. SWCNTs were uniformly dispersed in an acrylate UV-curable monomer including a few amounts of photo-initiator and photo-sensitizer. A femtosecond pulsed laser emitting at 780 nm was focused onto the resin, resulting in the photo-polymerization of a nanometric volume of the resin through TPP. By scanning the focus spot three dimensionally, arbitrary 3D structures were created. The spatial resolution of the fabrication was sub-micrometer, and SWCNTs were embedded in the sub-micro sized structures. The fabrication technique enables one to fabricate 3D micro structural SWCNT/polymer composites into desired shapes, and thus the technique should open up the further applications of SWCNT/polymer composites such as micro sized photomechanical actuators.
We present a fabrication method of gold nanorod/ polymer composite microstructures by means of a femtosecond
near-infrared laser light. The mechanism of this method is based on a cooperation of two optical reactions;
two-photon polymerization (TPP) reaction only at the surface of gold nanorods, and optical accumulation of gold
nanorods in photo-polymerizable resin. Gold nanorods were mass-produced by seed mediated growth method, and
were mono-dispersed in photo-resin. The wavelength of the laser light was tuned resonant to two-photon
absorption of the photo-resin, and also close to a longitudinal local surface plasmon resonance (LSPR) mode of the
gold nanorods. The laser light excited LSPR onto gold nanorods, resulting in the formation of thin polymer layer
only at their surface through TPP. Concurrently occurring optical accumulation of gold nanorods by continuous
irradiation of laser light, gold nanorods got together into focus spot. The TPP layer at the surface of gold nanorods
worked as a glue to stick one another for forming their aggregated structure in micro/nano scale. By controlling
the intensity and the exposure time of laser light, an optimal condition was found to induce dominant polymerization
without any thermal damages. The scanning of the focus spot makes it possible to create arbitrary micro/nano
structures. This method has a potential to create plasmonic optical materials by controlling the alignment of gold
nanorods.
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