During its early development stages, 3D printing was primarily used for rapid prototyping, whereas it is currently employed to fabricate products in various fields, including aerospace, automobile production, dentistry, architecture, and food. The photopolymerization of the polymer used for 3D printing is precise and provides excellent surface roughness but has lower mechanical strength than traditional manufacturing methods. In this study, Multi-walled Carbon Nanotubes (MWCNTs) were blended with urethane acrylate-based resin as a filler. Mechanical strength enhancement was confirmed using a DLP 3D printer. The stabilities of MWCNT dispersions in resin were verified, and viscosity and curing depth measurements were conducted to establish 3D printing parameters. Tensile and flexural strengths were higher for an MWCNT length of 50 μm than one of 100 μm, and maximum values were obtained at an MWCNT content of 0.1 phr. Under optimal conditions, tensile and flexural strengths increased by 2.1 and 1.8-fold, respectively.

Recent developments in additive manufacturing (AM) process have led us to fabricate many mechanical and electrical components or devices into complex geometries. Within existing AM processes, laser is widely used as an energy source to selectively sinter particles with a powder bed fusion (PBF) process or cure photopolymers with a vat photopolymerization (VPP) process. This study investigated the applicability of the SLS process for silver nanoparticles (Ag NPs)-photopolymer inks to fabricate micro-scale conductive patterns. With Ag NPs-photopolymer inks prepared with different mixture ratios and pasted on a polyethylene terephthalate (PET) substrate, a pulse width modulation (PWM) signal-controlled 405 nm laser was applied to these inks to selectively sinter and cure the Ag NPs and the photopolymer simultaneously. The final conductive patterns were obtained after a rinse in ethanol to remove un-sintered and un-cured regions of the inks. Microstructures, thickness profiles, pattern width, electrical resistance, and resistivity of the fabricated patterns were investigated by varying the PWM duty and the laser exposure time. Effects of different numbers of scan lines in the pattern and nanoparticle mixture ratios were also investigated. The proposed method is cost effective and easy with fast patterning capabilities. It will leverage practical advances in AM industries.

Micro-/nano-scale biological ‘soft’ structures have attracted increasing interest in biomedical research, including the study of cell-material interactions. However, most materials of micro-/nano-fabrication are not suitable for biological applications, as they require extensive post-processing or exhibit high mechanical stiffness. On the other hand, soft materials exhibiting high cytocompatibility require long fabrication times with a decreased spatial resolution of features. Thus, a facile fabrication technique of micro-/nano-scale structures of biological soft materials using a cost-effective and high-throughput method is needed. To achieve this, this study proposed a one-step 3D microfabrication method for biological soft materials in cooperation with a light-induced self-focusing photo-polymerization, a controlled oxygen reaction-diffusion, and digital microprinting. For instance, it was anticipated that this microfabrication technique of soft material provides efficient simple 3D scaffold platform that can address the questions of neural mechanobiology studies on the interaction between biological artificial axons bundle and neurons.