This paper considers inkjet printing of optical quality 3D nano-composites from diethylene-glycol diacrylate monomer (DEGDA) containing ZrO 2 nanoparticles at varying concentrations. One application for the composites is for gradient refractive index (GRIN) lenses. The process involves printing of a nanoparticle loaded monomer "ink" onto a substrate and then photopolymerizing the monomer layer by layer using UV light. The results of the study confirm that the presence of nanoparticles favorably affects the reaction kinetics. The reaction rate and chemical conversion are enhanced considerably by the nanoparticles. A seamless interface between the layers, which are 20 m thick, may be achieved if the conversion level of the layer onto which ink is deposited is limited at 60 to 80 %. Dynamic mechanical analysis (DMA) data indicate that both the glass transition and sub Tg viscoelastic properties are influenced by the nanoparticles. When nanoparticles are introduced the Tg relaxation shifts to lower temperatures and a sub Tg relaxation appears whose intensity increases with particle concentration. These results are consistent with a molecular confinement model involving a lower crosslink density rubbery layer at the polymer-particle interfaces.
Requirements for the miniaturization of electronics are constantly increasing as more and more functions are aimed to be integrated into a single device. At the same time, there are strong demands for low-cost manufacturing, environmental compatibility, rapid prototyping, and small-scale productions due to fierce competition, policies, rapid technical progress, and short innovation times. Altogether, those challenges cannot be sufficiently addressed by simply using either printed or silicon electronics. Instead, the synergies from combining those two technologies into so-called hybrid electronics create novel opportunities for advanced capabilities and new areas of applications. In the first part of this review, printing and patterning technologies are presented with potential compatibility with conventional electronics manufacturing techniques. They can be utilized for the fabrication of highly complex structures. Nonetheless, up-scalability, integration, and adaptation for industrial fabrication remain challenging due to technically limiting factors. Consequently, a special focus is placed on the up-scalability, availability of commercial printing, and manufacturing machines, as well as processing challenges for high-volume industrial applications. The second part of this review further provides an overview of exciting and innovative application possibilities of printed electronics, emphasizing sensor applications, as well as additively manufactured integrated circuits.
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