3D printing is used extensively in product prototyping and continues to emerge as a viable option for the direct manufacture of final parts. It is known that dielectric materials with relatively high real permittivity—which are required in important technology sectors such as electronics and communications—may be 3D printed using a variety of techniques. Among these, the fused deposition of polymer composites is particularly straightforward but the range of dielectric permittivities available through commercial feedstock materials is limited. Here we report on the fabrication of a series of composites composed of various loadings of BaTiO3 microparticles in the polymer acrylonitrile butadiene styrene (ABS), which may be used with a commercial desktop 3D printer to produce printed parts containing user-defined regions with high permittivity. The microwave dielectric properties of printed parts with BaTiO3 loadings up to 70 wt% were characterised using a 15 GHz split post dielectric resonator and had real relative permittivities in the range 2.6–8.7 and loss tangents in the range 0.005–0.027. Permittivities were reproducible over the entire process, and matched those of bulk unprinted materials, to within ~1%, suggesting that the technique may be employed as a viable manufacturing process for dielectric composites.

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Additive manufacturing of complex structures with spatially varying electromagnetic properties can enable new applications in high-technology sectors such as communications and sensors. This work presents the fabrication method as well as microstructural and dielectric characterization of bespoke composite filaments for fused deposition modeling (FDM) 3D printing of microwave devices with a high relative dielectric permittivity ϵ=11 in the GHz frequency range. The filament is composed of 32 vol % of ferroelectric barium titanate (BaTiO3) micro-particles in a polymeric acrylonitrile butadiene styrene (ABS) matrix. An ionic organic ester surfactant was added during formulation to enhance the compatibility between the polymer and the BaTiO3. To promote reproducible and robust printability of the fabricated filament, and to promote plasticity, dibutyl phthalate was additionally used. The combined effect of 1 wt % surfactant and 5 wt % plasticizer resulted in a uniform, many hundreds of meters, continuous filament of commercial quality capable of many hours of uninterrupted 3D printing. We demonstrate the feasibility of using the high dielectric constant filament for 3D printing through the fabrication of a range of optical devices. The approach herein may be used as a guide for the successful fabrication of many types of composite filament with varying functions for a broad range of applications.

Electrospinning of an aqueous poly(vinyl alcohol) and glycine solution has been used to produce nanofibers with an embedded crystalline glycine exclusively in the form of the β polymorph. The β-glycine nanocrystals are highly oriented within the polymer fibers and present good polar properties. Piezoelectric and nonlinear optical responses have been quantitatively examined showing piezoelectric coefficient d eff = 12.5 pm/V and an effective nonlinear optical susceptibility two times greater than that of potassium dihydrogen phosphate (KDP). Additionally, although bulk β-glycine is metastable at room temperature, when confined inside the polymeric nanofibers, it is shown to be remarkably stable.

In-plane aligned nanofibers of organic 2-methyl-4-nitroaniline (MNA) were produced by the electrospinning technique using a 1:1 weight ratio with poly(l-lactic acid). The fibers are capable of enormous efficient optical second harmonic generation as strong as pure MNA crystals in powder form. Structural, spectroscopic, and second harmonic generation polarimetry studies show that the MNA crystallizes within the fibers in an orientation in which the aromatic rings of MNA are predominantly orientated edge-on with respect to the plane of the fiber array and with their dipole moments aligned with the fiber axis. The results show that the electrospinning technique is an effective method to fabricate all-organic molecular functional devices based on polymer nanofibers with guest molecules possessing strong nonlinear optical and/or polar properties.