Research ArticleBIOMIMETIC

Artificial cilia as autonomous nanoactuators: Design of a gradient self-oscillating polymer brush with controlled unidirectional motion

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Science Advances  31 Aug 2016:
Vol. 2, no. 8, e1600902
DOI: 10.1126/sciadv.1600902
  • Fig. 1 Gradient self-oscillating polymer brush.

    Illustration of the self-oscillating polymer brush inducing unidirectional propagation of the chemical wave.

  • Fig. 2 Preparation of the gradient self-oscillating polymer brush.

    Preparation of the gradient self-oscillating polymer brush grafted on the glass surfaces by saATRP. (1) Immobilization of the ATRP initiator onto the glass substrate. ClMPETMS, ((Chloromethyl)phenylethyl)trimethoxy silane. (2) Preparation of gradient poly(NIPAAm-r-NAPMAm) by saATRP. DMF, dimethylformamide. (3) Conjugation of Ru(bpy)3 to the amino group of NAPMAm. DMSO, dimethyl sulfoxide.

  • Fig. 3 Amount of poly(NIPAAm-r-NAPMAm) grafted on the glass substrate.

    Dependence of the amount of grafted polymer on the gap distance (D) between the sacrificial anode and the ATRP initiator–immobilized glass substrate.

  • Fig. 4 AFM observation.

    (A to C) Height image (A), phase image (B), and cross-sectional analysis (C) of the self-oscillating polymer brush in the reduced state. Outer solution: 0.81 M HNO3 and 0.15 M NaCl. (D to F) Height image (D), phase image (E), and cross-sectional analysis (F) of the self-oscillating polymer brush in the oxidized state. Outer solution: 0.81 M HNO3 and 0.15 M NaBrO3.

  • Fig. 5 Characterization of the gradient polymer brush.

    (A) Illustration for the position on the gradient self-oscillating polymer brush–modified glass substrate. (B) The C/Si values analyzed by XPS at each position of the gradient self-oscillating polymer brush. Inset: Illustration of the gradient self-oscillating polymer brush showing the direction of x axis. (C) Cross-sectional analysis of the fluorescence intensity of the gradient self-oscillating polymer brush observed by fluorescence microscopy.

  • Fig. 6 Chemical wave propagation.

    (A) Propagation of the chemical wave on the gradient self-oscillating polymer brush observed by fluorescence microscopy. Scale bar, 500 μm. The time interval between each image is 10 s, and the temperature is 25°C. Outer solution: [HNO3] = 0.81 M, [NaBrO3] = 0.15 M, [MA] = 0.10 M. (B) Chemical wave profiles obtained by image analysis of each image shown in (A). (C) Spatiotemporal pattern of the chemical wave propagation on the gradient self-oscillating polymer brush. (D) Oscillating profiles at two different positions with large and small Ru amounts on the gradient self-oscillating polymer brush. The distance between the Ru large and Ru small is 200 μm.

  • Table 1 Elemental analyses.

    Elemental analysis at each position of the gradient self-oscillating polymer brush shown in Fig. 4A. n.d., note detected.

    Atom (%)
    PositionSiClRuCNOC/SiN/C
    019.71.3n.d.41.31.336.42.10.03
    123.20.7n.d.30.31.644.21.30.05
    218.00.60.139.64.337.42.20.11
    36.60.60.263.49.819.49.60.15
    42.00.50.172.311.014.136.40.15
    51.40.40.273.211.013.857.20.15
    621.60.60.131.72.743.31.50.08
    722.10.9n.d.30.82.144.11.40.07

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/8/e1600902/DC1

    fig. S1. Mechanism of saATRP.

    fig. S2. AFM observation for the flat surface.

    fig. S3. AFM observation for the gradient surface.

    fig. S4. Spatiotemporal analysis of the BZ reaction.

    movie S1. Chemical wave propagation.

    Mechanism for the BZ reaction (Field-Körös-Noyes model)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Mechanism of saATRP.
    • fig. S2. AFM observation for the flat surface.
    • fig. S3. AFM observation for the gradient surface.
    • fig. S4. Spatiotemporal analysis of the BZ reaction.
    • Mechanism for the BZ reaction (Field-Körös-Noyes model)
    • Legend for movie S1

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.mov format). Chemical wave propagation.

    Files in this Data Supplement:

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