3D Printing of Hierarchical Silk Fibroin Structures

Abstract

Like many other natural materials, silk is hierarchically structured from the amino acid level up to the cocoon or spider web macroscopic structures. Despite being used industrially in a number of applications, hierarchically structured silk fibroin objects with a similar degree of architectural control as in natural structures have not been produced yet due to limitations in fabrication processes. In a combined top-down and bottom-up approach, we exploit the freedom in macroscopic design offered by 3D printing and the template-guided assembly of ink building blocks at the meso- and nanolevel to fabricate hierarchical silk porous materials with unprecedented structural control. Pores with tunable sizes in the range 40-350 μm are generated by adding sacrificial organic microparticles as templates to a silk fibroin-based ink. Commercially available wax particles or monodisperse polycaprolactone made by microfluidics can be used as microparticle templates. Since closed pores are generated after template removal, an ultrasonication treatment can optionally be used to achieve open porosity. Such pore templating particles can be further modified with nanoparticles to create a hierarchical template that results in porous structures with a defined nanotopography on the pore walls. The hierarchically porous silk structures obtained with this processing technique can potentially be utilized in various application fields from structural materials to thermal insulation to tissue engineering scaffolds.

Engineering the Future of Silk Materials through Advanced Manufacturing

“…Additionally, although the 3D printed silk structures are usually on the macroscale, the mesoscale structures and the nanoscale structures can also be controlled by using mechanical stress and dopants. For example, the pore size of the silk hydrogel in the nanoscale can be controlled by the inclusion sacrificial nanoparticles with varying sizes . The hierarchically organized silk scaffold serves can be used as physical cues to direct the stem cell differentiation .…”

Macroporous materials: microfluidic fabrication, functionalization and applications

“…Besides, Sommer et al 359 used monodisperse PCL particles obtained by microfluidics 360 as sacrificed templates, combining with the 3D printing technique, to fabricate hierarchical silk porous materials with unprecedented structural control shown in Fig. 54.…”

3D Printing of Silk Protein Structures by Aqueous Solvent‐Directed Molecular Assembly

“…From a broader perspective, many other mature 3D printing and artificial manufacturing approaches for various polymers may not be appropriate for manufacturing proteinaceous structures. For example, high temperature‐induced phase‐transition, covalent (chemical or photochemical) and ionic crosslinking, and reinforcing and supporting materials seem to deviate far from the aqueous solvent‐based natural strategy and are generally insufficient to direct protein assembly, thus resulting in proteinaceous structures with either the mechanical performance severely inferior to that of natural counterparts, limited shaping capability, or both . For example, the thermoplastic processing of squid Suck Ring Teeth protein generated single fibers instead of 3D layered structures .…”