Flexible and Robust 2D Arrays of Silver Nanowires Encapsulated within Freestanding Layer-by-Layer Films

Authors

  • R. Gunawidjaja,

    1. Department of Materials Science and Engineering, Iowa State University, Gilman Hall, Ames, IA 50011, USA
    2. Present adress: School of Materials Science and Engineering, Georgia Institute of Technology, Love Building, Atlanta, GA 30332, USA
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  • C. Jiang,

    1. Department of Materials Science and Engineering, Iowa State University, Gilman Hall, Ames, IA 50011, USA
    2. Present adress: School of Materials Science and Engineering, Georgia Institute of Technology, Love Building, Atlanta, GA 30332, USA
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  • S. Peleshanko,

    1. Department of Materials Science and Engineering, Iowa State University, Gilman Hall, Ames, IA 50011, USA
    2. Present adress: School of Materials Science and Engineering, Georgia Institute of Technology, Love Building, Atlanta, GA 30332, USA
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  • M. Ornatska,

    1. Department of Materials Science and Engineering, Iowa State University, Gilman Hall, Ames, IA 50011, USA
    2. Present adress: School of Materials Science and Engineering, Georgia Institute of Technology, Love Building, Atlanta, GA 30332, USA
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  • S. Singamaneni,

    1. Department of Materials Science and Engineering, Iowa State University, Gilman Hall, Ames, IA 50011, USA
    2. Present adress: School of Materials Science and Engineering, Georgia Institute of Technology, Love Building, Atlanta, GA 30332, USA
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  • V. V. Tsukruk

    1. Department of Materials Science and Engineering, Iowa State University, Gilman Hall, Ames, IA 50011, USA
    2. Present adress: School of Materials Science and Engineering, Georgia Institute of Technology, Love Building, Atlanta, GA 30332, USA
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  • The authors thank M. C. LeMieux, M. E. McConney, and H. Ko for technical assistance and invaluable help. The PDMS substrate was generously provided by A. Nolte, MIT. This work is supported by AFOSR, FA9550-05-1-0209 and NSF-NIRT-0 506 832 grants.

Abstract

Freestanding layer-by-layer (LbL) films encapsulating controlled volume fractions (ϕ = 2.5–22.5 %) of silver nanowires are fabricated. The silver nanowires are sandwiched between poly(allylamine hydrochloride)/poly(styrene sulfonate) (PAH/PSS) films resulting in nanocomposite structures with a general formula of (PAH/PSS)10PAH Ag(PAH/PSS)10PAH. The Young's modulus, toughness, ultimate stress, and ultimate strain are evaluated for supported and freestanding structures. Since the diameter of the nanowires (73 nm) is larger than the thickness of the LbL films (total of about 50 nm), a peculiar morphology is observed with the silver nanowires protruding from the planar LbL films. Nanowire-containing LbL films possess the ability to sustain significant elastic deformations with the ultimate strain reaching 1.8 %. The Young's modulus increases with increasing nanowire content, reaching about 6 GPa for the highest volume fraction, due to the filler reinforcement effect commonly observed in composite materials. The ultimate strengths of these composites range from 60–80 MPa and their toughness reaches 1000 kJ m–3 at intermediate nanowire content, which is comparable to LbL films reinforced with carbon nanotubes. These robust freestanding 2D arrays of silver nanowires with peculiar optical, mechanical, and conducting properties combined with excellent micromechanical stability could serve as active elements in microscopic acoustic, pressure, and photothermal sensors.

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