Laser direct writing of multifunctional micro/nano devices using carbon nanotube–polymer composites

To unleash the full potential of two-photon polymerization (TPP) as a promising technique for three-dimensional (3D) fabrication of functional micro/nanostructures, multi-walled carbon nanotubes (MWNT) as filling materials were incorporated into polymer resins. Scanning electron microscopy images and polarized Raman spectra showed that the MWNTs with concentrations up to 0.2 wt % were uniformly distributed throughout the polymer matrix by thiol functionalization. A near-infrared femtosecond pulsed laser beam was focused into the composite resins, resulting in the 3D fabrication of arbitrary micro/nano architectures. The obtained MWNT-thiol-acrylate (MTA) composite structures exhibited significantly enhanced electrical conductivity and mechanical strength, and maintained high optical transmittance at the same time. Furthermore, MWNTs were self-aligned along the laser scanning direction in thiol-acrylate polymer, resulting in high electrical anisotropic effect of the MTA composites. Based on this highly conductive MTA composite photoresist, various functional micro/nano architectures and devices have been successfully fabricated, including photonic crystals, micromodels, microcapacitors and microresistors. Precise assembly of MWNTs with ∼100 nm spatial resolution was achieved by the combination of TPP and direct pyrolysis. This technique enables 3D precise printing of multifunctional micro/nano devices and holds great potential to pave a way for wide applications of carbon nanotubes, such as 3D electronics, integrated photonics and micro/nanoelectromechanical systems (MEMS/NEMS).