Polymeric micro devices are gaining huge market potential in broad areas of medical devices, diagnostic devices, drug delivery, and optical applications. Current research is focusing on developing functional polymeric micro devices on a mass-production scale. Microinjection moulding is a promising technique suitable for fabricating polymeric micro devices. This review aims to summarise the primary achievements that have been achieved in various aspects of microinjection moulding of polymer micro devices, consisting of micro parts and micro surface structures. The relationships of the machine, process, rheology, tooling, micro/nanoscale replication, morphology, properties, and typical applications are reviewed in detail. Finally, a conclusion and challenges are highlighted.

To address the challenges of deteriorated surface morphology and insufficient mechanical and tribological performance in Ni/MoS₂ nanocomposite coatings, this study proposes a novel ultrasonic-assisted electrodeposition method coupled with in situ SiC abrasive particle polishing. This synergistic approach enables refined crystallization, enhanced particle dispersion, and dynamic surface smoothing by simultaneously introducing ultrasonic cavitation and hard-particle dynamics into the deposition environment. The experimental results demonstrate that under an optimized ultrasonic power density (18 W/cm²), the surface roughness of the Ni and Ni/MoS₂ coatings is reduced by 41 % and 70 %, respectively. The microhardness increased 2.5-fold for Ni and 3.4-fold for Ni/MoS₂ compared to the coatings fabricated without ultrasound and abrasive SiC particle treatment. Remarkably, the corresponding friction coefficients decrease to 0.2 and 0.1, respectively, with wear rates reduced by 60 % and 75 %, respectively. The self-lubricating MoS₂ further contributed by forming a uniform lubricating film under the combined effect of ultrasound dispersion and abrasive SiC particle polishing. This work establishes a fundamental framework for multi-field synergistic modulation during electrodeposition, offering a versatile route for the fabrication of high-performance defect-suppressed coatings for micro/nanoscale precision components.