A new type of three-dimensional (3D) serpentine microchannel reactor was fabricated by thermally bonding stacked polyimide films to greatly improve the mixing efficiency by transversal vortices at low Reynolds number (Re). The effects of Re, flow ratio R, and channel width on the mixing performance were investigated using the Villermaux−Dushman method, in which the segregation index X S was utilized to quantify the mixing efficiency. The results showed that X S decreased with increasing Re, decreasing R, and reducing channel width. Then, a computational fluid dynamics model was employed to analyze the flow characteristics. The vortices that varied periodically along the 3D serpentine microchannel significantly improved the mixing efficiency. Furthermore, the application of the 3D serpentine microchannel reactor in the biohydration of acrylonitrile demonstrated that the new design is very promising for fast reactions that are limited by mass transfer resistance.

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Mechanically close-to-bone carbon-fiber-reinforced poly-ether-ether-ketone (CFR-PEEK)-based orthopedic implants are rising to compete with metal implants, due to their X-ray transparency, superior biocompatibility, and body-environment stability. While real-time strain assessment of implants is crucial for the postsurgery study of fracture union and failure of prostheses, integrating precise and durable sensors on orthopedic implants remains a great challenge. Herein, a laser direct-write technique is presented to pattern conductive features (minimum sheet resistance <1.7 𝛀 sq -1 ) on CRF-PEEK-based parts, which can act as strain sensors. The as-fabricated sensors exhibit excellent linearity (R 2 = 0.997) over the working range (0-2.5% strain). While rigid silicon-or metal-based sensor chips have to be packaged onto flat surfaces, all-carbon-based sensors can be written on the complex curved surfaces of CFR-PEEK joints using a portable laser mounted on a six-axis robotic manipulator. A wireless transmission prototype is also demonstrated using a Bluetooth module. Such results will allow a wider space to design sensors (and arrays) for detailed loading progressing monitoring and personalized diagnostic applications.

Zigzag is a classic microchannel configuration with unique modifiable geometric parameters (bending angles and overlapped regions) compared with other serpentine geometries. It provides an additional potential for application-oriented micromixer design. In this work, diverse novel three-dimensional (3D) zigzag micromixer configurations were proposed and investigated based on classic zigzag planar geometries. These micromixers consist of misaligned inlet junction parts and 3D zigzag mixing parts with various bending angles and overlapped regions. The mixing performance, mixing mechanism, and pressure drop characteristics of these micromixers were investigated by numerical simulation. Furthermore, selected 3D micromixer geometries were fabricated into polyimide-based microfluidic chips by efficient and low-cost manufacturing techniques. The Villermaux–Dushman experiment has been conducted in these customized chips, which exhibits promising prospects in biochemical applications.