Research ArticleENGINEERING

Electrically assisted 3D printing of nacre-inspired structures with self-sensing capability

See allHide authors and affiliations

Science Advances  05 Apr 2019:
Vol. 5, no. 4, eaau9490
DOI: 10.1126/sciadv.aau9490
  • Fig. 1 Schematic diagram of the electrically assisted 3D-printing platform for the construction of nacre-inspired structures.

    (A) Diagram of the electrically assisted 3D-printing device. (B) Illustration of the bottom-up projection-based stereolithography process. (C and D) Schematic diagrams showing the alignment of GNs under the electric field and alignment mechanisms, respectively. (E) 3D-printed nacre with aGNs and SEM images showing surface and cross-section morphology. DMD, digital micromirror device; PDMS, polydimethylsiloxane.

  • Fig. 2 The 3D-printing process.

    (A) Nacre model by SolidWorks (from Dassault Systèmes), sliced using our DMD-based stereolithography software to generate projection patterns. (B) rGNs are aligned by the electric field (blue dotted arrow shows the direction) to generate aGNs during the 3D-printing process; after the alignment, the composites solidify after light exposure (yellow part), the alignment of GNs is kept in the composites, and then the build plate peels after the layer is complete to print additional layers with aGNs. (C) Compression of natural nacre and SEM images of the fracture surface, showing crack deflection (yellow arrowheads) and crack branching (red arrowheads) in (D) and crack deflection between layers in (E). (F) 3D-printed nacre with 2 wt % aGNs under loading with crack deflection and branching in (G). (H) SEM image showing deflection between layers (yellow arrowheads).

  • Fig. 3 Mechanical property and microstructure study of 3D-printed nacre.

    (A) Comparison of compression properties of the 3D-printed nacre with different loadings and alignments. (B) Crack propagation in MJ/rGNs nacre with the breaking of rGNs. (C and F) Simulations of stress distribution of MJ/rGNs and MJ/aGNs by COMSOL Multiphysics, respectively. (D) Comparison of maximum compression load for the 3D-printed nacre with different mass ratios of GNs. (E) Crack deflection of MJ/aGNs nacre and bridging and interlocking of aGNs.

  • Fig. 4 Comparison of fracture toughness by three-point bending test.

    (A to C) Compression force versus resistance change for pure MJ, MJ/2 wt % rGNs, and MJ/2 wt % aGNs, respectively (with inset SEM images showing the related fracture surfaces). (D) Comparison of fracture toughness for crack initiation (KIC) and stable crack propagation (KJC) of the 3D-printed nacre with the natural nacre. (E) Comparison of specific toughness and specific strength of the 3D-printed nacre with others’ work (inset shows the specific strength with density for various nacre-inspired composites). R-curves of the 3D-printed nacre (F) and the natural nacre (G). Simulations of stress distribution by COMSOL Multiphysics for the 3D-printed nacre with rGNs (H) and aGNs (I).

  • Fig. 5 3D-printed smart helmet with anisotropic electrical property.

    (A) Anisotropic electrical property of the 3D-printed nacre. (B) Changes of electrical resistance with different GNs loadings and alignments. (C) Schematic diagram showing the layered polymer/GNs structure with anisotropic electrical resistance. (D) 3D-printing process of a self-sensing smart helmet. Demonstration of the wearable sensor on a Lego bicycle rider showing different self-sensing properties for the 3D-printed helmets with rGNs (E) and aGNs (F). (G) Circuit design for the tests. Compression force of the 3D-printed helmets with related compression displacements and resistance changes for rGNs (H) and aGNs (I), respectively. (Photo credit: Yang Yang, Epstein Department of Industrial and Systems Engineering, University of Southern California.)

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/4/eaau9490/DC1

    Supplementary Discussion

    Fig. S1. Surface modification of GN and FTIR spectrum results.

    Fig. S2. SEM images of fracture surfaces of the pure MJ polymer and MJ/GNs composites with rGNs and aGNs without and with surface modification, respectively.

    Fig. S3. Schematic diagram and optical microscopic images show the alignment of GNs under the electric field.

    Fig. S4. Picture of the natural nacre and SEM images.

    Fig. S5. Sliced patterns of nacre model and SEM results of the 3D-printed nacre.

    Fig. S6. Comparison of fracture surfaces of the natural nacre with the 3D-printed nacre.

    Fig. S7. Changes of cure depth with the fraction of GNs.

    Fig. S8. Demonstration of the bonding between the MJ polymer matrix and GN fillers.

    Fig. S9. Crack deflection and the brick-and-mortar structure in the natural nacre and the 3D-printed nacre.

    Fig. S10. A comparison of fracture behavior of the 3D-printed nacre and the natural nacre.

    Fig. S11. The schematic diagram shows the drop-tower impact test setup for 3D printed helmet with rGNs and aGNs.

    Fig. S12. The standard three-point bending tests were performed to study the flexural strength of the 3D-printed structures.

    Fig. S13. The setup to test the resistance change of the 3D-printed helmet during compression.

    Fig. S14. A comparison of the resistance changes of the 3D-printed helmets with different loadings of rGNs and aGNs during compression.

    Fig. S15. Illustration of the microstructure of the 3D-printed nacre with rGNs and aGNs.

    Fig. S16. The calculation of the interconnection of GNs in 3D-printed structures.

    Table S1. Comparison of alignment of fillers in polymer-based composites using different methods.

    Table S2. Comparison of densities, shape complexity, and electrical conductivity of nacre-inspired structures fabricated using different methods.

    Movie S1. Self-sensing capability of 3D-printed helmet with rGNs.

    Movie S2. Self-sensing capability of 3D-printed smart helmet with aGNs.

    References (4960)

  • Supplementary Materials

    The PDF file includes:

    • Supplementary Discussion
    • Fig. S1. Surface modification of GN and FTIR spectrum results.
    • Fig. S2. SEM images of fracture surfaces of the pure MJ polymer and MJ/GNs composites with rGNs and aGNs without and with surface modification, respectively.
    • Fig. S3. Schematic diagram and optical microscopic images show the alignment of GNs under the electric field.
    • Fig. S4. Picture of the natural nacre and SEM images.
    • Fig. S5. Sliced patterns of nacre model and SEM results of the 3D-printed nacre.
    • Fig. S6. Comparison of fracture surfaces of the natural nacre with the 3D-printed nacre.
    • Fig. S7. Changes of cure depth with the fraction of GNs.
    • Fig. S8. Demonstration of the bonding between the MJ polymer matrix and GN fillers.
    • Fig. S9. Crack deflection and the brick-and-mortar structure in the natural nacre and the 3D-printed nacre.
    • Fig. S10. A comparison of fracture behavior of the 3D-printed nacre and the natural nacre.
    • Fig. S11. The schematic diagram shows the drop-tower impact test setup for 3D printed helmet with rGNs and aGNs.
    • Fig. S12. The standard three-point bending tests were performed to study the flexural strength of the 3D-printed structures.
    • Fig. S13. The setup to test the resistance change of the 3D-printed helmet during compression.
    • Fig. S14. A comparison of the resistance changes of the 3D-printed helmets with different loadings of rGNs and aGNs during compression.
    • Fig. S15. Illustration of the microstructure of the 3D-printed nacre with rGNs and aGNs.
    • Fig. S16. The calculation of the interconnection of GNs in 3D-printed structures.
    • Table S1. Comparison of alignment of fillers in polymer-based composites using different methods.
    • Table S2. Comparison of densities, shape complexity, and electrical conductivity of nacre-inspired structures fabricated using different methods.
    • References (4960)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.avi format). Self-sensing capability of 3D-printed helmet with rGNs.
    • Movie S2 (.avi format). Self-sensing capability of 3D-printed smart helmet with aGNs.

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article