Cyclic olefin copolymers (COC) are amorphous, transparent thermoplastics composed of cyclic olefin monomers (norbornene) and linear olefins (ethene). They are increasingly utilized as fabrication materials for microsystems and microfluidic devices, owing to their promising features of low water absorption, high electrical insulation, long-term stability of surface treatments, and resistance to a broad variety of acids and solvents. Many manufacturing processes for COC-based devices have been developed in recent decades. These methodologies are categorized as replication methods or fast prototyping as common in fabrication of thermoplastic microfluidic devices. This review gives a full discussion of the features of COCs, the various production processes, and the numerous selected applications in microfluidic platforms. The review also explores COC's composition and fundamental features, as well as fabrication processes and applications in a variety of fields, investigates the material's potential advantages and uses, and attempts to create a comprehensive list of COC's possible benefits. Due to their unique features and simplicity of fabrication, COCs are projected to advance the future of microfluidics, microsystems, and optofluidics.

Recent years have witnessed an increased interest in the development of nanoparticles (NPs) owing to their potential use in a wide variety of biomedical applications, including drug delivery, imaging agents, gene therapy, and vaccines, where recently, lipid nanoparticle mRNA-based vaccines were developed to prevent SARS-CoV-2 causing COVID-19. NPs typically fall into two broad categories: organic and inorganic. Organic NPs mainly include lipid-based and polymer-based nanoparticles, such as liposomes, solid lipid nanoparticles, polymersomes, dendrimers, and polymer micelles. Gold and silver NPs, iron oxide NPs, quantum dots, and carbon and silica-based nanomaterials make up the bulk of the inorganic NPs. These NPs are prepared using a variety of top-down and bottom-up approaches. Microfluidics provide an attractive synthesis alternative and is advantageous compared to the conventional bulk methods. The microfluidic mixing-based production methods offer better control in achieving the desired size, morphology, shape, size distribution, and surface properties of the synthesized NPs. The technology also exhibits excellent process repeatability, fast handling, less sample usage, and yields greater encapsulation efficiencies. In this article, we provide a comprehensive review of the microfluidic-based passive and active mixing techniques for NP synthesis, and their latest developments. Additionally, a summary of microfluidic devices used for NP production is presented. Nonetheless, despite significant advancements in the experimental procedures, complete details of a nanoparticle-based system cannot be deduced from the experiments alone, and thus, multiscale computer simulations are utilized to perform systematic investigations. The work also details the most common multiscale simulation methods and their advancements in unveiling critical mechanisms involved in nanoparticle synthesis and the interaction of nanoparticles with other entities, especially in biomedical and therapeutic systems. Finally, an analysis is provided on the challenges in microfluidics related to nanoparticle synthesis and applications, and the future perspectives, such as large-scale NP synthesis, and hybrid formulations and devices. Graphical abstract

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