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Review
. 2016 Feb;138(2):021006.
doi: 10.1115/1.4032423.

Three-Dimensional-Printing of Bio-Inspired Composites

Free PMC article
Review

Three-Dimensional-Printing of Bio-Inspired Composites

Grace Xiang Gu et al. J Biomech Eng. .
Free PMC article

Abstract

Optimized for millions of years, natural materials often outperform synthetic materials due to their hierarchical structures and multifunctional abilities. They usually feature a complex architecture that consists of simple building blocks. Indeed, many natural materials such as bone, nacre, hair, and spider silk, have outstanding material properties, making them applicable to engineering applications that may require both mechanical resilience and environmental compatibility. However, such natural materials are very difficult to harvest in bulk, and may be toxic in the way they occur naturally, and therefore, it is critical to use alternative methods to fabricate materials that have material functions similar to material function as their natural counterparts for large-scale applications. Recent progress in additive manufacturing, especially the ability to print multiple materials at upper micrometer resolution, has given researchers an excellent instrument to design and reconstruct natural-inspired materials. The most advanced 3D-printer can now be used to manufacture samples to emulate their geometry and material composition with high fidelity. Its capabilities, in combination with computational modeling, have provided us even more opportunities for designing, optimizing, and testing the function of composite materials, in order to achieve composites of high mechanical resilience and reliability. In this review article, we focus on the advanced material properties of several multifunctional biological materials and discuss how the advanced 3D-printing techniques can be used to mimic their architectures and functions. Lastly, we discuss the limitations of 3D-printing, suggest possible future developments, and discuss applications using bio-inspired materials as a tool in bioengineering and other fields.

Figures

Fig. 1
Fig. 1
Illustration of design process of bio-inspired synthetic materials, structures, and applications through the interaction between biological materials and 3D-printing. Biological materials are optimized through evolution and are an inspiration for scientists and engineers. 3D-printing together with modeling has become an efficient predictive tool to understand nature and create improved bio-inspired synthetic materials.
Fig. 2
Fig. 2
(a) Biological bone's seven levels of hierarchy from the nanoscale to macroscale. Adapted from Launey et al. [15]. Copyright 2010 by Annual Reviews. (b) Toughening mechanisms of bone include molecular uncoiling, fibrillar sliding, and microcracking on the smaller scales, and the larger scales include collagen–fibril bridging, uncracked-ligament bridging, and crack deflection. Adapted from Launey et al. [15]. Copyright 2010 by Annual Reviews. (c) Self-healing process of bone includes: inflammatory response, repair stage, and the remodeling stage.
Fig. 3
Fig. 3
(a) Hierarchical structure of red abalone from nano-, to micro-, to meso-, to macroscales. Reproduced with permission from Sun and Bhushan [20]. Copyright 2012 by The Royal Society of Chemistry. (b) Nacre has different compressive and tensile strengths under different loading directions [37]. Nacre's anisotropic nature allows it to endure high compressive forces, which can be beneficial for underwater designs such as a submarine. (c) Turtle shell architecture allows the shell to be flexible at small strains and strong in high strains, which can help improve protection designs. (d) Tensile stress–strain curve for different parts of the squid beak wing. The tensile stress decreases along the compositional gradient from highest being heavily tanned to the lowest being untanned parts. Reproduced with permission from Miserez et al. [38]. Copyright 2008 by The American Association for the Advancement of Science. (e) Schematic showing attachment of a submarine mussel to a stone via the mussel byssus. The proximal part (50 MPa) is more elastic and the distal part (500 MPa) is stiffer [39].
Fig. 4
Fig. 4
Analysis of the influence of spinning process and protein chain length on the formation of continuous and robust silk fibers. (a) Synthetic silk protein model and main building blocks. Building block named “A” represents poly(alanine) and the hydrophobic domain. Building block named “B” represents GGX (X = R, L, Y, or Q) rich and the hydrophilic domain. Hydrophobic A domain forms β-sheet crystals for stiffness and strength. Hydrophilic B domain forms the semi-amorphous phase for extensibility of the silk fiber. Adapted from Lin et al. [58]. Copyright 2015 by Nature Publishing Group. (b) Schematic of the natural spinning process. A highly concentrated unfolded protein solution flows through the spinning duct and undergoes shear flow and elongation. The pH decreases, and the spinning dope is subjected to ion exchange: phosphate and potassium ions are added while water, sodium, and chloride ions are extracted. The produced silk is aligned and rich in β-sheet crystals. (c) Influence of shear flow and protein chain length on the formation of silk fibers. Adapted from Lin et al. [58]. Copyright 2015 by Nature Publishing Group. (i) Single protein snapshot for H(AB)4 (short protein chain) and H(AB)12 (long protein chain). Building block named “H” is introduced for purification and is hydrophilic. H(AB)4 and H(AB)12 results after equilibration (before shear flow). (ii) H(AB)4 and H(AB)12 results after equilibration (before shear flow). (iii) H(AB)4 and H(AB)12 results after shear flow.
Fig. 5
Fig. 5
(a) Hierarchical structure of human hair. (b) Schematic of hair fiber coiled–coil protein composed of alpha-helices, connected by disulfide bond. (c) Schematic of a three-strand model composed of three alpha-helices connected by a cluster of disulfide bond with different geometric arrangement and strength.
Fig. 6
Fig. 6
(a) Using simple model material building blocks, Dimas et al. manufactured bio-inspired composites with 3D printing and tested the synthesized specimens to compare model predictions to experimental results [84]. Copyright 2013 by John Wiley and Sons. (b) Mirzaeifar et al. observed bone-like printed samples with different hierarchies. The difference between the cracked samples performance and the uncracked samples for the largest hierarchy is the smallest, indicating more defect tolerance as hierarchy increases. Crack propagation for different samples is shown and is much more delocalized for the higher hierarchy levels. Reprinted (adapted) with permission from Mirzaeifar et al. [85]. Copyright 2015 by American Chemical Society. (c) Optimization of composites using stiff and soft building blocks similar to natural materials.
Fig. 7
Fig. 7
(a) 3D printing of a triangular honeycomb composite and illustration of the progressive alignment of fillers within the nozzle during composite ink deposition. Adapted from Compton and Lewis [7]. Copyright 2014 by John Wiley and Sons. (b) Printed glass scaffold SEM images. Adapted from Fu et al. [90]. Copyright 2011 by John Wiley and Sons. (c) 3D-printed sacrificial 3D structure to make vascular template. Adapted from Gergely et al. [91]. Copyright 2015 by John Wiley and Sons.
Fig. 8
Fig. 8
SEM image of sharkskin denticles. (a) and (b) Environmental scanning electron microscope images of bonnethead shark skin surface and denticles located at its head. Adapted from Wen et al. [9]. Copyright 2014 by The Company of Biologists Ltd. (c) SEM image of the synthetic shark skin membrane. Adapted from Wen et al. [9]. Copyright 2014 by The Company of Biologists, Ltd. 3D-printed rigid regular shaped and spaced bio-inspired denticles fixed on a flexible membrane.
Fig. 9
Fig. 9
Geometry and mechanical behavior of seahorse tail. Adapted from Porter et al. [98]. Copyright 2015 by The American Association for the Advancement of Science. (a) μCT image of seahorse tail skeleton and its cross section. The tail is composed of a series of square components constituted of four L-shaped bone plates surrounding the central vertebral column. (b) and (c) 3D-printed prototypes of seahorse (b) bio-inspired square tail and (c) hypothetical cylindrical tail, in (i) bending and (ii) twisting position. (iii) Elastic deformation just before strut disjoining of prototypes seahorse tail.
Fig. 10
Fig. 10
Schematic of 3D-printed bio-inspired suture interface with different tailored waveforms (antitrapezoidal, rectangular, trapezoidal, and triangular) [100]
Fig. 11
Fig. 11
Influence of material distribution on web strength under different types of loading. Adapted from Qin et al. [99]. Copyright 2015 by Nature Publishing Group. (a) Web geometry. Left: Computational model. Right: 3D-printed bio-inspired spider web. Radius of the web is R = 50.8 mm. (b) Snapshots of simulations of the web under (up) local load on four spiral threads and (down) homogenously distributed uniform load. (c) Plot of Fpeak/M versus ds2/dr2,where Fpeak is the peak force, M is the total mass of the web, ds is the diameter of spiral threads and dr is the diameter of radial threads. The maximum peak force occurs: (1) under local load on four spiral threads when dsdr, and (2) under uniform loading when ds dr.
Fig. 12
Fig. 12
(a) Photo of our HA 3D-printer, adapted for HA ink extrusion via pressurized air. Air is pushed through the top of syringe in order to extrude material out of nozzle below onto substrate, while print bed moves. The printer bed moves in the x,y-direction while the nozzle moves in the z-direction. The syringe and nozzle can easily be changed to accommodate different materials. (b) As the 3D-printer constructed in the Buehler lab uses pressure extrusion to print viscoelastic material, the flow rate for HA ink at varying pressures was recorded when the ink was loaded in a 10 cc syringe. A linear trend is observed and shows that with increasing pressure, the flow rate increases.
Fig. 13
Fig. 13
(a) 3D-model of helicoidal structural pattern and (b) SEM of Mantis shrimp helicoid geometry. Adapted from Weaver et al. [53]. Copyright 2012 by The American Association for the Advancement of Science. (c) 3D-model of helicoid geometry constructed for finite element characterization. (d)–(f) Mantis shrimp helicoid geometry extruded using self-supporting HA ink material.

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