Multi-material nanofiber composites have recently attracted attention, as they introduce new opportunities for regulating mechanical, electrical, and biological properties. The majority of previously reported nanoscale composites have incorporated particulate materials (e.g. metallic nanoparticles) or carbon nanotubes. Integrating multiple types of polymer fibers at the nanoscale will enable the development of scaffolds whose mechanical properties can be easily regulated through material selection and the ratio of components.
Toward this goal, we have developed a novel manufacturing method for multi-material composite nanofabrics. Current fiber fabrication techniques (e.g. multi-nozzle electrospinning) are challenged by applications requiring multi-phase nanotextiles or orthogonal solvents. The centrifugal force-based rotary jet spinning (RJS) system has the potential to overcome these limitations by eliminating the reliance on electric fields for fiber formation and reducing the number of processing parameters.
We fabricated tough multi-material polymer nanofabrics using a custom-designed dual chamber RJS reservoir. Using infrared spectroscopy and tensile testing, we compared the mechanical and structural properties of multi-material fabrics and single fiber blends. Our conclusions:
Multi-material polymer fabrics are tougher than their pure components
Mechanical properties of composite nanofabrics can be tuned by varying the polymer ratio and composition.
The system can be used to fabricate nanotextiles using orthogonal (incompatible) solvents
Dual Chamber Rotary Jet Spinning Reservoir
Setup of Dual Chamber Reservoir with Polymer Precursor Solutions (blue and red)
Illustration of multi-material nanofabric fabrication using rotary jet spinning (RJS) and the dual chamber reservoir (DCR). Inset: Cutaway side view of the DCR. Inner and outer chambers are denoted in blue and red, respectively.
Adapted from N. Sinatra et al, 2017.
Multi-Material Nanofabric Manufacturing
Fabricating Nanocomposites Using
Orthogonal Polymers + Solvents
(inset) Scanning electron micrograph of multi-material
PVDF-TrFE/Polyurethane (PU) nanofabric.
FTIR spectra of pure PVDF-TrFE, pure polyurethane, and
multi-material PVDF-TrFE/PU nanofabrics. This plot shows that both materials are present in the multi-material nanotextile.
Using traditional nanofiber manufacturing, polymers with orthogonal (immiscible) solvents are unable to be produced together. This constraint limits production of nanofabric composites between a wide range of elastic, conductive, and piezoelectric polymers, among other substrates. We overcame this challenge by separating precursor polymer solutions and removing reliance on electric fields, thereby decreasing the number of processing parameters and increasing throughput.
The RJS dual chamber reservoir can be used to fabricate multi-material nanotextiles using orthogonal (incompatible) polymers and solvents.
As a proof of concept, we chose the piezoelectric co-polymer PVDF-TrFE, which has limited solubility in most organic solvents used for nanofiber production. Many PVDF-TrFE-based sensors rely on sandwiching fibrous mats between elastic sheets to increase flexibility. By producing a composite nanofabric using PVDF-TrFE and elastic polyurethane (PU), this method has the potential to preserve the piezoelectricity of the co-polymer while incorporating an elastomer on the nanoscale as a mechanical support.