In this study, we report a neo-conceptive three-dimensionally (3D) crossing manifold micromixer (CMM) embedded in microchannel. Fabricated by sequential processes of photolithography and two photon absorption stereolithography, this leads to a microfluidic system with a built-in micromixer in a site controlled manner. The effectiveness of CMM is investigated numerically and experimentally. Through the numerical simulation, it is estimated that a high mixing ratio of 90% can be obtained even in a channel length shorter than five times the channel width. This compares well with the conventional passive type of micromixers that have a gradual increase in mixing efficiency with the length of the channel. Furthermore, the mixing performance of the realized CMM built-in microchannel is observed by confocal microscopy.

Various wearable electronic devices have been developed for extensive outdoor activities. The key metrics for these wearable devices are high touch sensitivity and good mechanical and thermal stability of the flexible touchscreen panels (TSPs). Their dielectric constants (k) are important for high touch sensitivities. Thus, studies on flexible and transparent cover layers that have high k with outstanding mechanical and thermal reliabilities are essential. Herein, an unconventional approach for forming flexible and transparent cellulose nanofiber (CNF) films is reported. These films are used to embed ultralong metal nanofibers that serve as nanofillers to increase k significantly (above 9.2 with high transmittance of 90%). Also, by controlling the dimensions and aspect ratios of these fillers, the effects of their nanostructures and contents on the optical and dielectric properties of the films have been studied. The length of the nanofibers can be controlled using a stretching method to break the highly aligned, ultralong nanofibers. These nanofiber-embedded, high-k films are mechanically and thermally stable, and they have better Young's modulus and tensile strength with lower thermal expansion than commercial transparent plastics. The demonstration of highly sensitive TSPs using high-k CNF film for smartphones suggests that this film has significant potential for next-generation, portable electronic devices.

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