Browsing by Author "Shankar, Akash"

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    Flexible polydimethylsiloxane/multi-walled carbon nanotubes membranous metacomposites with negative permittivity
    (Elsevier, 2017-09) Sun, Kai; Xie, Peitao; Wang, Zhongyang; Su, Tongming; Shao, Qian; Ryu, JongEun; Zhang, Xihua; Guo, Jiang; Shankar, Akash; Li, Jianfeng; Fan, Runhua; Cao, Dapeng; Guo, Zhanhu; Department of Mechanical Engineering, School of Engineering and Technology
    Metacomposites with negative electromagnetic parameters can be promising substitute for periodic metamaterials. In this paper, we devoted to fabricating flexible metacomposite films, which have great potential applications in the field of wearable cloaks, sensing, perfect absorption and stretchable electronic devices. The conductivity and the complex permittivity were investigated in flexible polydimethylsiloxane (PDMS)/multi-walled carbon nanotubes (MWCNTs) membranous nanocomposites, which were fabricated via in-situ polymerization process. With the increase of conductive one-dimension carbon nanotubes concentration, there was a percolation transition observed in conduction due to the formation of continuous networks. The dielectric dispersion behavior was also analyzed in the spectra of complex permittivity. It is indicated that the conduction and polarization make a combined effect on the dielectric loss in flexible PDMS/MWCNTs composites. The negative permittivity with a dielectric resonance was obtained, and was attributed to the induced electric dipoles.
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    Reinforcement of Cu Nanoink Film with Extended Carbon Nanofibers for Large Deformation of Printed Electronics
    (Office of the Vice Chancellor for Research, 2016-04-08) Kim, Jeonghwan; Shankar, Akash; Zhu, Jiahua; Choi, Daniel S.; Guo, Zhanhu; Ryu, Jong Eun
    Metallic nanoparticle inks (nanoinks) have attracted great interest in the manufacturing of printed flexible electronics. However, micro-cracks and pores generated during the sintering process deteriorate mechanical and electrical characteristics of the sintered nanoink film. To alleviate these problems, we demonstrated the use of very long carbon nanofiber (CNF, average length 200 μm) to reinforce the sintered nanoink films. In this study, different weight fractions of CNFs are dispersed into the Cu nanoink to improve the mechanical bending characteristics. Scanning electron micrographs (SEM) shows improved dispersion of oxidized CNF in the nanoink compared to the as-received CNF. The composite nanoinks are stencil printed on polyethylene terephthalate (PET) film and sintered by intense pulsed light system using Xe-flash. The electrical measurements show 90 %, 65 %, and 66 % improved electrical conductivity in the composite nanoink film (0.7 % of oxidized CNF) compared to the pure Cu nanoink under the 75 mm, 50 mm, and 25 mm of bending radii, respectively.