Research ArticleSOFT MATTER PHYSICS

Mimosa Origami: A nanostructure-enabled directional self-organization regime of materials

See allHide authors and affiliations

Science Advances  24 Jun 2016:
Vol. 2, no. 6, e1600417
DOI: 10.1126/sciadv.1600417
  • Fig. 1 Preparation and characterization of the superhydrophilic-superhydrophobic Janus bilayer.

    (A) Schematic illustration of the Janus bilayer assembly: a multifunctional stack is fabricated by sequential electrospinning of a protective PVP, a superhydrophilic PCL, and a superhydrophobic PVC nanofiber layers on paper. This stack is shaped in a functional geometry and completed by adhering a PS nanofiber layer to a flexible PDMS substrate on the PVC surface by van der Waals (VDW) interaction. The protective PVP layer and paper are easily peeled off by hand. (B) Optical photographs show the isolated Janus bilayer and its cohesive and stretching properties. (C and D) SEM analysis at low-magnification (8.8k) and high-magnification (70k) images (insets, bottom right) of the Janus bilayer PVC and PCL surfaces and their contrasting wetting (insets, upper right). (E) FTIR spectroscopic analysis of the multilayer stack and isolated Janus bilayer confirming its PCL (orange line) and PVC (green line) composition. a.u., arbitrary units. (F) Dynamic mechanical stress-strain analysis (tension mode) of the Janus bilayer showing a soft rubbery nature, with a Young’s modulus (E) of 4.85 MPa.

  • Fig. 2 Demonstration of directional self-organization via Mimosa Origami self-assembly.

    (A) Optical photographs of the spontaneous directional self-organization response of a rectangular-shaped Janus bilayer. A pinpoint water droplet stimulus results in the immediate self-assembly of a centimeter-long microchannel. (B) This rapid motion is reminiscent of the stimulus-response propagation during the negative tropism of the M. pudica’s leaflets. (C) The folded Janus bilayers are spontaneously unfolded by immersion in an ethanol bath. Restoration of the initial surface properties allows a novel folding cycle, demonstrating the full reversibility of this self-organization state. (D) FTIR spectroscopic analysis showing the variation in the surface composition of the Janus bilayer during the folding and unfolding cycle. (E) Schematic illustrations of capillary-induced unfolding of the self-assembled microchannel.

  • Fig. 3 Mimosa Origami self-assembly mechanism and theoretical analysis.

    (A) Optical photographs of the directional self-assembly of the Janus bilayers into a closed microchannel. (B) Schematic description of the self-assembly process: initially, a water-tight bulb is formed by the rapid folding (33 ms) of the Janus bilayer terminal around a water droplet. Thereafter, the waterfront slowly advances from the bulb to the dry PCL surface. Once sufficient water has collected, the wet Janus bilayer strip folds rapidly, forming a hollow 3D cross section. This leads to the Mimosa Origami propagation (400 ms cm−1) of the folding stimulus by longitudinal propulsion of the waterfront and orthogonal folding of the Janus bilayer strip. (C) Theoretical model of the minimal strip width required for the spontaneous Mimosa Origami self-assembly regime as a function of the surface roughness and characteristic contact angle (θe).

  • Fig. 4 Application of the Mimosa Origami directional self-organization to microfluidics.

    (A) Waterfront displacement from the bulb during Mimosa Origami self-assembly as a function of the strip width and time. (B) Maximal displacement and velocity as a function of strip width and 1/width fit. (C) Water instantaneous velocity as a function of the time since water droplet release on the Janus bilayer terminal surface and comparison against the LWR equation for an ideal circular capillary. (D to G) Exemplary modular microfluidic designs obtained by the self-assembly of functionally shaped Janus bilayer strips, including (D) mixing bulb channel, (E) curved tapering channel, (F) T junctions, and (G) U turns.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/6/e1600417/DC1

    Supplementary Text

    Supplementary Calculations

    Supplementary Material Data

    Supplementary Equations

    fig. S1. Synthesis of nanostructured Janus bilayer by sequential electrospinning.

    fig. S2. SA analysis of the superhydrophobic layers.

    fig. S3. Morphological characterization (SEM) of the supporting and sacrificial layers.

    fig. S4. Hemiwicking superhydrophilic nature of the PCL layer.

    fig. S5. Separation of the Janus bilayer from the PVP protective layer.

    fig. S6. Static self-assembly of Janus bilayers.

    fig. S7. Janus bilayer and PCL monolayer response on hydrophilic (paper) substrates.

    fig. S8. Qualitative wetting characterization of 2- and 3-mm strips of Janus bilayer and PCL monolayer on a hydrophilic paperboard.

    fig. S9. Enlarged images of initial Janus bilayer folding.

    fig. S10. Representative thermodynamic states of the Janus bilayer during self-assembly.

    fig. S11. Response of the PVC side of the Janus bilayer to water.

    fig. S12. Mimosa Origami of a 2-mm strip of Janus bilayer and PCL monolayer on the PDMS-PS substrates.

    fig. S13. Decreasing stimulus propagation rate for a 2-mm-wide strip and a stimulus droplet size of 40 μl.

    table. S1. Width-to-diameter ratios of Mimosa Origami–assembled microchannels.

    table. S2. Material properties of Janus bilayers.

    movie S1. Static self-assembling properties of circular-shaped Janus bilayer demonstrating artificial tropism in response to a microdroplet.

    movie S2. Mimosa Origami assembly of the Janus bilayer strips on a superhydrophobic PS-PDMS substrate.

    movie S3. Mimosa Origami assembly of the Janus bilayer strips performing double right-angle turns on a superhydrophobic PS-PDMS substrate.

    movie S4. Mimosa Origami assembly of the Janus bilayer strips performing longer and tighter double right-angle turns on a superhydrophobic PS-PDMS substrate.

    movie S5. Mimosa Origami assembly of the Janus bilayer strips on a superhydrophobic PS-PDMS substrate.

    movie S6. Modular microfluidics: Janus-based Mimosa Origami strips with double-ended bulbs on a superhydrophobic PS-PDMS substrate showing in-channel droplet mixing.

    movie S7. Modular microfluidics: Janus-based Mimosa Origami strips with double-ended bulbs, with a central bulb on a superhydrophobic PS-PDMS substrate, showing in-bulb droplet mixing.

    movie S8. Modular microfluidics: Janus-based Mimosa Origami strips at a T-junction, showcasing double-ended split for potential in multichannel capabilities.

    movie S9. Cyclic insertion and removal of water from an as-assembled microfluidics channel, showcasing suitability toward pump-aided microfluidic designs.

    References (3744)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • Supplementary Calculations
    • Supplementary Material Data
    • Supplementary Equations
    • fig. S1. Synthesis of nanostructured Janus bilayer by sequential electrospinning.
    • fig. S2. SA analysis of the superhydrophobic layers.
    • fig. S3. Morphological characterization (SEM) of the supporting and sacrificial layers.
    • fig. S4. Hemiwicking superhydrophilic nature of the PCL layer.
    • fig. S5. Separation of the Janus bilayer from the PVP protective layer.
    • fig. S6. Static self-assembly of Janus bilayers.
    • fig. S7. Janus bilayer and PCL monolayer response on hydrophilic (paper) substrates.
    • fig. S8. Qualitative wetting characterization of 2- and 3-mm strips of Janus bilayer and PCL monolayer on a hydrophilic paperboard.
    • fig. S9. Enlarged images of initial Janus bilayer folding.
    • fig. S10. Representative thermodynamic states of the Janus bilayer during self-assembly.
    • fig. S11. Response of the PVC side of the Janus bilayer to water.
    • fig. S12. Mimosa Origami of a 2-mm strip of Janus bilayer and PCL monolayer on the PDMS-PS substrates.
    • fig. S13. Decreasing stimulus propagation rate for a 2-mm-wide strip and a stimulus droplet size of 40 μl.
    • table. S1. Width-to-diameter ratios of Mimosa Origami–assembled microchannels.
    • table. S2. Material properties of Janus bilayers.
    • Legends for movies S1 to S9
    • References (3744)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.mp4 format). Static self-assembling properties of circular-shaped Janus bilayer demonstrating artificial tropism in response to a microdroplet.
    • movie S2 (.mp4 format). Mimosa Origami assembly of the Janus bilayer strips on a superhydrophobic PS-PDMS substrate.
    • movie S3 (.mp4 format). Mimosa Origami assembly of the Janus bilayer strips performing double right-angle turns on a superhydrophobic PS-PDMS substrate.
    • movie S4 (.mp4 format). Mimosa Origami assembly of the Janus bilayer strips performing longer and tighter double right-angle turns on a superhydrophobic PS-PDMS substrate.
    • movie S5 (.mp4 format). Mimosa Origami assembly of the Janus bilayer strips on a superhydrophobic PS-PDMS substrate.
    • movie S6 (.mp4 format). Modular microfluidics: Janus-based Mimosa Origami strips with double-ended bulbs on a superhydrophobic PS-PDMS substrate showing in-channel droplet mixing.
    • movie S7 (.mp4 format). Modular microfluidics: Janus-based Mimosa Origami strips with double-ended bulbs, with a central bulb on a superhydrophobic PS-PDMS substrate, showing in-bulb droplet mixing.
    • movie S8 (.mp4 format). Modular microfluidics: Janus-based Mimosa Origami strips at a T-junction, showcasing double-ended split for potential in multichannel capabilities.
    • movie S9 (.mp4 format). Cyclic insertion and removal of water from an as-assembled microfluidics channel, showcasing suitability toward pump-aided microfluidic designs.

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article