Abstract
Aiming at the production of light, porous, conductive, biosafe composites, in this paper we are presenting a novel fabrication method for monolithic, three-dimensional (3D) graphene foam (GF)/porous polymer composites. The synthesis adopts a novel process architecture by using Ni foam templates in an inductive heating chemical vapor deposition growth process, and by removing Ni chemically while retaining graphene integrity by the reversible application of cyclododecane (CD); finally, nondestructive coating procedures with polycaprolactone (PCL) solutions have been developed. The composites can be optimized to enhance electrical conduction, flexibility and mechanical properties, while mixing PCL and CD allows to coat the GF with a novel mesoporous polymer coating. By tuning the GF properties, the typical electrical resistance of the 3D forms can be reduced to a few 10 s of Ohms, values that are maintained after the PCL coatings. The current study achieved a GF fraction ranging between 1 and 7.3 wt%, with even the lower graphene content composites showing acceptable electrical and mechanical properties. The properties of these conductive 3D-GF/PCL composites are in line with the requirements for applications in the field of nerve tissue engineering.Graphical abstract
Highlights
Graphene and graphene-based materials are currently under study for many different applications in diverse fields such as batteries [1], solar cells [2], corrosion prevention [3], chemical sensors [4] and water purification [5]; among these, fields biomedicine and tissue engineering [6] show excellent premises
When graphene materials are randomly distributed in the polymeric matrix in the form of powders or flakes, the electrical conductivity of the composite strongly depends on the electron percolation across different conductive flakes: If the density is low, few conductive paths are available, and the composite exhibits a low overall conductivity [15]
Polymer composites based on graphene materials flakes can be prepared in the form of porous scaffolds by various methods such as solvent casting, gas foaming, phase separation, melt molding technique, emulsification, freeze-drying/lyophilization, electrospinning, microfluidic technique, photopolymerization, micromolding and bioprinting; each technique leads to composite scaffolds with different properties [16]
Summary
Graphene and graphene-based materials are currently under study for many different applications in diverse fields such as batteries [1], solar cells [2], corrosion prevention [3], chemical sensors [4] and water purification [5]; among these, fields biomedicine and tissue engineering [6] show excellent premises. When applying fillers made of interconnected and monolithic networks of graphene (3Dgraphene) where electrons can move freely, the electrical conductivity is higher [11, 17, 18] and almost independent of graphene loading Due to this attractive feature, the preparation of 3D-graphene/ polymer composites has been investigated and several different preparation methods have been reported [15, 17, 19]. In order to avoid the solvent bath, problematic for the sample integrity, we rather applied cyclododecane (CD) [31] as a temporary protective layer This waxy solid coats graphene materials to assist the wet etching of nickel, and it is removed by mild thermal processes only. PCL is applied to the free-standing 3D-GF
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