title: Gradient Polymer Nanofoams for Encrypted Recording of Chemical Events.
abstract: We have fabricated gradient-grafted nanofoam films that are able to record the presence of volatile chemical compounds in an offline regime. In essence, the nanofoam film (100-300 nm thick) is anchored to a surface cross-linked polymer network in a metastable extended configuration that can relax back to a certain degree upon exposure to a chemical vapor. The level of the chain relaxation is associated with thermodynamic affinity between the polymer chains and the volatile compounds. In our design, the chemical composition of the nanofoam film is not uniform; therefore, the film possesses a gradually changing local affinity to a vapor along the surface. Upon vapor exposure, the nonuniform changes in local film morphology provide a permanent record or "fingerprint" for the chemical event of interest. This permanent modification in the film structure can be directly detected via changes not only in the film surface profile but also in the film optical characteristics. To this end, we demonstrated that sensing/recording nanofoam films can be prepared and interrogated on the surfaces of optical waveguides, microring optical resonators. It is important that the initial surface profile and structure of the nanofoam film are encrypted by the distinctive conditions that were used to fabricate the film and practically impossible to replicate without prior knowledge.
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Nikolay
authors.initials: N
authors.lastname: Borodinov
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Anna Paola
authors.initials: AP
authors.lastname: Soliani
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Galabura
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Bogdan
authors.initials: B
authors.lastname: Zdyrko
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Carley
authors.initials: C
authors.lastname: Tysinger
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Spencer
authors.initials: S
authors.lastname: Novak
authors.affiliation: Microphotonics Center and Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Qingyang
authors.initials: Q
authors.lastname: Du
authors.affiliation: Microphotonics Center and Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Yizhong
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Microphotonics Center and Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Vivek
authors.initials: V
authors.lastname: Singh
authors.affiliation: Microphotonics Center and Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Zhaohong
authors.initials: Z
authors.lastname: Han
authors.affiliation: Microphotonics Center and Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Juejun
authors.initials: J
authors.lastname: Hu
authors.affiliation: Microphotonics Center and Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Lionel
authors.initials: L
authors.lastname: Kimerling
authors.affiliation: Microphotonics Center and Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Anuradha Murthy
authors.initials: AM
authors.lastname: Agarwal
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.|College of Optics and Photonics, University of Central Florida , Orlando, Florida 32816, United States.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Richardson
authors.affiliation: Department of Materials Science and Engineering, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Igor
authors.initials: I
authors.lastname: Luzinov
keywords: gradient polymer films; microring optical resonators; nanofoams; polymer grafting; sensors