Bioinspired 3D Printing of Functional Materials by Harnessing Enzyme‐Induced Biomineralization

Abstract

Nature builds structurally ordered and environmentally adaptive composite materials by harnessing biologically catalyzed mineralization under mild conditions. Despite recent advancements in engineering conventional materials with microorganisms through biomimetic mineralization, it remains difficult to produce mineralized composites that integrate the hierarchical structure and living attributes of their natural counterparts. Here, a kind of functional material is developed by integrating 3D printed hydrogel architectures with enzyme-induced biomineralization. It is shown that the enzyme-induced mineralization intensely transforms flexible and soft hydrogels (modulus of 125 kPa) to rigid (150 MPa) and highly mineralized hydrogel composites. Coupling with embedded 3D printing, sophisticated and mineralized freeform architectures are fabricated in the absence of sacrificial inks, which were previously unattainable through conventional manufacturing strategies. Moreover, by exploiting multi-material 3D printing to tailor the construct composition, exquisite control over the mineral distribution within the hydrogel constructs can be achieved, thus composite materials with tessellated architectures and unconventional mechanics could be obtained. The study provides a viable means to fabricate composite materials with highfidelity architectures and tailored mechanical properties, unlocking paths to the next generation of functional materials and structures by integrating 3D printing with biomineralization.

Advances in 3D Gel Printing for Enzyme Immobilization

“…There are several common ways to formulate the ink for reaching desirable rheological properties. These include partial gelation through weak physical crosslinking [ 70 , 71 , 72 ], addition of colloidal clay particles [ 19 , 24 ], emulsification [ 44 ], partial gelation by enzymatic crosslinking [ 43 , 73 ], introduction of polymer entanglements [ 23 , 69 ] and addition of fused silica nanoparticles [ 74 ]. As shown in Figure 5 a, including silica nanoparticles significantly increased the apparent ink viscosity while adding enzyme into the mixture did not affect the overall shear thinning behavior of the hydrogel ink.…”

“…A common challenge facing photo-crosslinked hydrogels, or all hydrogels in general, is their weak mechanical properties. Chen et al [ 74 ] used DIW coupled with UV curing to print photo-crosslinkable acrylamide-based resin loaded with alkaline phosphatase (ALP). The printed hydrogel lattices were then immersed in calcium glycerophosphate (CaGP) solution for biomineralization over a period of 7 days.…”

“… Evaluation of printability of hydrogel inks: ( a ) apparent viscosity vs. shear rate and ( b ) storage moduli (G′) and loss moduli (G″) vs. shear stress measured at oscillatory frequency of 1 Hz (reproduced with permission from Ref. [ 74 ]). …”

“…( B ) Multi-scale observations of the mineral growth in hydrogel (reproduced with permission from Ref. [ 74 ]).…”

Integrated 3D printing of flexible electroluminescent devices and soft robots

“…Multi-material 3D printing, on the other hand, is an emerging high-throughput and programmable manufacturing technique that enables the creation of multi-component 2D and 3D intricate objects from a wide range of functional viscoelastic materials, offering a viable strategy for achieving this goal [18][19][20] . However, despite recent progress in 3D printed electronics, such as displays, wearable electronics, solidstate lightings, and biomedical electronics 21,22 , the fabrication of sophisticated EL devices through multi-material 3D printing remains largely unexplored [23][24][25] .…”