Printability and functional performance of DIW-fabricated LSR/TiO₂ composite ink

Abstract

Abstract. Direct Ink Writing (DIW) has become an effective additive manufacturing method to print complex structures of elastomers with high-viscosity printable inks. As part of this research, LSR/TiO₂ composite inks were developed and tested to determine their printability and functional performance in DIW processing. The preparations of 5 ink compositions with 1-5 wt% TiO₂ nanoparticles were first performed with liquid silicone rubber (LSR), catalyst, and glycerol as a rheological modifier. A pre-trial experiment was carried out to determine the extrusion characteristics and dimensional stability of the developed inks. Among the tested compositions, the one with 5 wt% TiO₂ was found to be the most stable in forming filaments and for the purpose of giving excellent geometry retention upon deposition. Thus, this ink was optimized and chosen to perform another characterization of the material and printing analyses. The rheological measurements showed that the higher the content of TiO₂, the more the rheology was increased and extrusion was achievable. The X-ray diffraction analysis revealed the existence of rutile-phase TiO₂ in the silicone matrix without any change of structure. Thermogravimetric analysis demonstrated the existence of good thermal stability of the composite to about 350°C, and scanning electron microscopy depicted the relatively uniform distribution of nanoparticles in the elastomer matrix. Moreover, DIW printing experiments were able to print different geometries such as straight filaments, rectilinear tracks, multilayer sheets, and solid discs with controlled processing environments. The findings indicate that the developed LSR/TiO₂ composite ink has the right rheological, structural, and thermal qualities to be confidently DIW-fabricated silicone-based functional structures.