Research ArticleMATERIALS SCIENCE

Acoustophoretic printing

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Science Advances  31 Aug 2018:
Vol. 4, no. 8, eaat1659
DOI: 10.1126/sciadv.aat1659
  • Fig. 1 Acoustophoretic printing.

    (A) Schematic view of acoustophoretic printing, in which the radiation pressure provides an additional force that aids drop formation and ejection. (B) Optical images of droplets formed as a function of varying acoustophoretic forces and nozzle diameter d (left), images obtained under simple dripping mode (Fg), and log-log plot of droplet volume and maximum ejection frequency over the range of acoustophoretic forces explored (right). (C) Schematic view of a two-component nozzle that delivers a mixture of water and PEG (molecular weight = 8000 g/mol) ranging from 0 to 60 wt % PEG (viscosity between 1 and 1000 mPa·s, respectively) (left), optical images of droplets generated during acoustophoretic printing of these model fluids (middle), and log-log plot of droplet volume as a function of ink viscosity (right, black bars denote 1 pixel = 9 μm). (D) Acoustophoretic printing of prototypical yield stress fluids composed of 0.2 to 1.0 wt % carbopol in water alongside images of an ink vial containing a carbopol solution of 1.0 wt % (left, middle) and log-log plot of shear stress as a function of shear rate for these solutions.

  • Fig. 2 Principle and acoustophoretic properties of the subWAVE.

    (A) Schematic view of the subwavelength acoustophoretic voxel ejector (left). The resonance (schematically shown in red) leads to high acoustic pressure amplification while keeping the field strongly confined (right). (B) Side view of the experimental setup (top) and close-up of the tapered nozzle (λ ≈ 14 mm) (bottom). Calculated vertical force distribution inside the subWAVE (C) and its experimental validation (D). (E) Schematic illustration of acoustophoretic printing, which shows that when the total acoustophoretic and gravitational forces exceed the capillary force, droplet detachment and outcoupling from the subWAVE enable patterning on any substrate. (F) Log-log plot of vertical force generated within the subWAVE as a function of drop volume compared to a classical standing-wave levitator.

  • Fig. 3 Drop-on-demand acoustophoretic printing.

    (A) Drop-on-demand printing of a rasterized (large-area) image, in which fluid dispensing is synchronized with the substrate movement to provide spatial control over the patterned droplets. (B) Schematic view of droplet deposition (top) illustrating the exit angle α, drop trajectory Δ, distance L between the nozzle and substrate, and offset distance between subWAVE exit and substrate. Images of patterned droplet traces as a function of acoustophoretic pressure ga. Scale bar, 2 mm. (C) Plot of positional accuracy of droplets deposited via acoustophoretic printing as a function of this offset distance L. The subWAVE can be placed as close as 1 mm (0.07λ) from the substrate without hindering the drop deposition process. (Note that the drop trajectory and exit angle are plotted as SDs.)

  • Fig. 4 Acoustophoretic printing of food, optical, biological, and electrically conductive materials.

    (A) Schematic illustration of the broad Z range enabled by acoustophoretic printing, which extends over nearly six orders of magnitude, and corresponding images of droplets patterned by this approach. Note that the typical Z range for inkjet printing is highlighted in red. Scale bars, 500 μm. (B) Honey droplets printed on white chocolate. (C) Optical adhesive resin printed in a spiral motif yielding a microlens array. (D) Acoustophoretic printing of hMSC-laden collagen I ink for viability testing and patterning. (a) Bright-field images of printed droplets composed of hMSCs in a collagen I matrix (geq = 43g) cultured for 7 days. (b) Cell viability of acoustophoretically printed droplets with increasing acoustic force (n = 6). n.s., not significant. (c) Bright-field image of patterned droplets at day 17 (geq = 18g). (d) Representative confocal microscopy images of an immunofluorescently stained, printed droplet (geq = 43g) cultured to day 17 and a higher-magnification region stained for CD105 (green), CD90 (red), CD45 (gray), and nuclei [4′,6-diamidino-2-phenylindole (DAPI), blue]. (E) Acoustophoretic printing of a liquid metal ink composed of eGaIn patterned as individual droplets at room temperature in noncontact mode.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/8/eaat1659/DC1

    Materials and Methods

    Supplementary Analysis

    Fig. S1. Horizontal acoustophoretic printing of liquid droplets.

    Fig. S2. Acoustophoretic printing of viscous fluids.

    Fig. S3. The Fabry-Perot resonator.

    Fig. S4. Acoustophoretic 3D printing of aqueous polymer solution.

    Fig. S5. Droplet trajectory accuracy and distribution.

    Fig. S6. Acoustophoretic printing of honey droplets.

    Fig. S7. Acoustophoretic bioprinting.

    Fig. S8. Classical acoustophoretic levitator.

    Fig. S9. Scaling and nozzle effects on acoustophoretic forces.

    Fig. S10. Pressure drop as function of nozzle diameter.

    Table S1. Primary antibodies and markers of interest.

    Movie S1. Acoustophoretic printing of liquids using different nozzle diameters d and equivalent accelerations geq.

    Movie S2. Horizontal acoustophoretic printing of a 1:1 water-glycerol mixture.

    Movie S3. Acoustophoretic printing of single droplet of honey compared to simple dripping.

    Movie S4. Confocal z-stack movie and 3D renderings of acoustophoretically printed droplets composed of hMSCs suspended in a collagen I matrix.

    Movie S5. Acoustophoretic printing of liquid metal droplets, in which 3D structures are assembled in a contact-free manner (real time).

  • Supplementary Materials

    The PDF file includes:

    • Materials and Methods
    • Supplementary Analysis
    • Fig. S1. Horizontal acoustophoretic printing of liquid droplets.
    • Fig. S2. Acoustophoretic printing of viscous fluids.
    • Fig. S3. The Fabry-Perot resonator.
    • Fig. S4. Acoustophoretic 3D printing of aqueous polymer solution.
    • Fig. S5. Droplet trajectory accuracy and distribution.
    • Fig. S6. Acoustophoretic printing of honey droplets.
    • Fig. S7. Acoustophoretic bioprinting.
    • Fig. S8. Classical acoustophoretic levitator.
    • Fig. S9. Scaling and nozzle effects on acoustophoretic forces.
    • Fig. S10. Pressure drop as function of nozzle diameter.
    • Table S1. Primary antibodies and markers of interest.
    • Legend for Movies S1 to S5

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Acoustophoretic printing of liquids using different nozzle diameters d and equivalent accelerations geq.
    • Movie S2 (.mp4 format). Horizontal acoustophoretic printing of a 1:1 water-glycerol mixture.
    • Movie S3 (.mp4 format). Acoustophoretic printing of single droplet of honey compared to simple dripping.
    • Movie S4 (.mp4 format). Confocal z-stack movie and 3D renderings of acoustophoretically printed droplets composed of hMSCs suspended in a collagen I matrix.
    • Movie S5 (.mp4 format). Acoustophoretic printing of liquid metal droplets, in which 3D structures are assembled in a contact-free manner (real time).

    Files in this Data Supplement:

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