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Functional droplets that recognize, collect, and transport debris on surfaces

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Science Advances  28 Oct 2016:
Vol. 2, no. 10, e1601462
DOI: 10.1126/sciadv.1601462
  • Fig. 1 Illustration of HA NP capture using functional, polymer-stabilized emulsion droplets.
  • Fig. 2 Synthesis of polymers 3, 4, and 6.

    (Insets) Chemical structure of the 3-bromopyridine–substituted Grubbs catalyst and the aromatic region of the 1H NMR spectra of polymers 3 and 4.

  • Fig. 3 Optical micrographs and TEM images of HA NPs before and after pickup.

    (A) Optical micrograph (scale bar, 500 μm) of HA NPs coated on a Si substrate before attempted NP pickup (inset: corresponding SEM image of the same substrate as the outset; scale bar, 500 nm). (B) Optical (main) and SEM (inset) images of the Si substrate after NP pickup (scale bars, 500 μm for the outset and 500 nm for the inset). (C) TEM image of dried HA NPs (scale bar, 100 nm). (D) TEM image of a portion of a dried droplet showing the presence of HA NPs (scale bar, 500 nm).

  • Fig. 4 Visualization of HA NP pickup using alizarin-labeled NPs.

    (A) Commercial HA NP suspended in ethanol before staining. (B) Alizarin-labeled HA NPs suspended in ethanol. (C) Fluorescence micrograph of alizarin-labeled HA NP–coated substrate. (D) Same substrate after HA NP pickup using polymer 4–stabilized droplets. (E) Fluorescence micrograph of polymer 4–stabilized droplets following NP pickup. Scale bars (C to E), 500 μm.

  • Fig. 5 Illustration of HA NP pickup and drop-off.

    The oil-in-water emulsion droplets stabilized by polymer 4 pick up HA NPs from the Si substrate and then drop them off downstream on the PDA-coated Si substrate or PET film.

  • Fig. 6 HA NPs picked up by oil-in-water droplets stabilized by polymer 4 and dropped off on PDA-coated Si substrate.

    (A) Fluorescence micrograph of alizarin-labeled HA NP–coated substrates before pickup. (B) Fluorescence micrograph of PDA-coated Si substrate before drop-off and SEM image of PDA-coated Si substrate before drop-off (inset). (C) Fluorescence micrograph of alizarin-labeled HA NP–coated substrates after pickup. (D) Fluorescence micrograph of PDA-coated Si substrate after drop-off and SEM image of PDA-coated Si substrate after drop-off (inset). Scale bars, 500 μm for the micrographs and 500 nm for the SEM images [insets of (B) and (D)].

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/10/e1601462/DC1

    fig. S1. 13C NMR spectra of polymers 3 and 4.

    fig. S2. 1H NMR spectra of polymers 3 and 4.

    fig. S3. Oil-in-water emulsion droplets stabilized by polymer 4.

    fig. S4. Experimental setup for picking up HA NPs.

    fig. S5. Control experiments using pH 7 water and droplets stabilized by polymer 6.

    fig. S6. HA NP–coated silicon substrate before and after pickup in 0.1 M NaOH solution.

    fig. S7. HA NP–coated Si substrate before and after rinsing with pH 4 HCl solution.

    fig. S8. Picking up HA NPs using polymer 4 in Ca2+-rich solution.

    fig. S9. Positive electrospray spectrum of an aqueous catechol/CaCl2 (1:1 molar ratio) mixture in MeOH/water (1:1).

    fig. S10. Picking up HA NPs from PDMS substrate.

    fig. S11. Picking up HA NPs from mica.

    fig. S12. Picking up HA NPs from PET film.

    fig. S13. Optical micrographs of HA NPs picked up by oil-in-water droplets stabilized by polymer 4 and dropped off on PDA-coated Si substrate taken under white light.

    fig. S14. HA NPs picked up by oil-in-water droplets stabilized by polymer 4 and dropped off on PET film.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. 13C NMR spectra of polymers 3 and 4.
    • fig. S2. 1H NMR spectra of polymers 3 and 4.
    • fig. S3. Oil-in-water emulsion droplets stabilized by polymer 4.
    • fig. S4. Experimental setup for picking up HA NPs.
    • fig. S5. Control experiments using pH 7 water and droplets stabilized by polymer 6.
    • fig. S6. HA NP–coated silicon substrate before and after pickup in 0.1 M NaOH solution.
    • fig. S7. HA NP–coated Si substrate before and after rinsing with pH 4 HCl solution.
    • fig. S8. Picking up HA NPs using polymer 4 in Ca2+-rich solution.
    • fig. S9. Positive electrospray spectrum of an aqueous catechol/CaCl2 (1:1 molar ratio) mixture in MeOH/water (1:1).
    • fig. S10. Picking up HA NPs from PDMS substrate.
    • fig. S11. Picking up HA NPs from mica.
    • fig. S12. Picking up HA NPs from PET film.
    • fig. S13. Optical micrographs of HA NPs picked up by oil-in-water droplets stabilized by polymer 4 and dropped off on PDA-coated Si substrate taken under white light.
    • fig. S14. HA NPs picked up by oil-in-water droplets stabilized by polymer 4 and dropped off on PET film.

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