Development of Rapid and High-Precision Colorimetric Device for Organophosphorus Pesticide Detection Based on Microfluidic Mixer Chip

Acoustohydrodynamic micromixers: Basic mixing principles, programmable mixing prospectives, and biomedical applications

Acoustohydrodynamic micromixers offer excellent mixing efficiency, cost-effectiveness, and flexible controllability compared with conventional micromixers. There are two mechanisms in acoustic micromixers: indirect influence by induced streamlines, exemplified by sharp-edge micromixers, and direct influence by acoustic waves, represented by surface acoustic wave micromixers. The former utilizes sharp-edge structures, while the latter employs acoustic wave action to affect both the fluid and its particles. However, traditional micromixers with acoustic bubbles achieve significant mixing performance and numerous programmable mixing platforms provide excellent solutions with wide applicability. This review offers a comprehensive overview of various micromixers, elucidates their underlying principles, and explores their biomedical applications. In addition, advanced programmable micromixing with impressive versatility, convenience, and ability of cross-scale operations is introduced in detail. We believe this review will benefit the researchers in the biomedical field to know the micromixers and find a suitable micromixing method for their various applications.

An overview on state-of-art of micromixer designs, characteristics and applications

Micromixers are characterized based on characteristics such as excellent mixing efficiency, low reagent cost and flexible controllability compared with conventional reactors in terms of macro size. A variety of designs and applications of micromixers have been proposed. The focus of current reviews is restricted to micromixer structures. Each type of micromixer has characteristics corresponding to its structure, which determines the suitable application areas. This paper provides an overview connecting micromixer designs and their applications. First, the typical designs and mixing mechanisms of both passive and active micromixers are summarized. Then, application cases of micromixers, including chemical, biological and medical applications, are presented. The characteristics, including the advantages and restrictions of different micromixers, are discussed. Finally, the future perspective of micromixer design is proposed. It is predictable that micromixers will have widespread applications by integrating two or more different mixing methods together. This review would be beneficial to guide the design of micromixers applied for specific purposes.

Research progress on pesticide residue detection based on microfluidic technology

The problem of pesticide residue contamination has attracted widespread attention and poses a risk to human health. The current traditional pesticide residue detection methods have difficulty meeting rapid and diverse field screening requirements. Microfluidic technology integrates functions from sample preparation to detection, showing great potential for quick and accurate high-throughput detection of pesticide residues. This paper reviews the latest research progress on microfluidic technology for pesticide residue detection. First, the commonly used microfluidic materials are summarized, including silicon, glass, paper, polydimethylsiloxane, and polymethyl methacrylate. We evaluated their advantages and disadvantages in pesticide residue detection applications. Second, the current pesticide residue detection technology based on microfluidics and its application to real samples are summarized. Finally, we discuss this technology's present challenges and future research directions. This study is expected to provide a reference for the future development of microfluidic technology for pesticide residue detection.

Time-efficient fabrication method for 3D-printed microfluidic devices

Recent developments in 3D-printing technology have provided a time-efficient and inexpensive alternative to the fabrication of microfluidic devices. At present, 3D-printed microfluidic systems face the challenges of post-processing, non-transparency, and being time consuming, limiting their practical application. In this study, a time-efficient and inexpensive fabrication method was developed for 3D-printed microfluidic devices. The material for 3D-printed microfluidic chips is Dowsil 732, which is used as a sealant or encapsulant in various industries. The curing time and surface hydrophobicity of the materials were evaluated. The results indicated that the surface of Dowsil 732 is hydrophilic. An optimization model of the direct ink writing method is proposed to establish a time-efficient and accurate fabrication method for microfluidic devices. The results indicate that the optimization model can effectively describe the change trend between printing speed, printing pressure, and channel wall accuracy, and the model accuracy rate exceeds 95%. Three examples-a micromixer, concentration gradient generator, and droplet generator-were printed to demonstrate the functionality and feasibility of the fabrication method.

Preparation and Characterization of Pendimethalin Microcapsules Based on Microfluidic Technology

Microencapsulation of pesticides is a promising attempt to reduce environmental pollution and prevent the active ingredients from the interference of external factors. In this paper, pendimethalin microcapsules were prepared by the interfacial polymerization of 4,4-methylenediphenyl diisocyanate (MDI) and ethylenediamine (EDA) based on microfluidic technology. Effects of the microchannel structure, reaction temperature, surfactant type, and fluid flow rates were investigated and evaluated. The results showed that pendimethalin microcapsules prepared under suitable conditions had a smooth surface, good monodispersity, a high encapsulation efficiency (96.7%), and excellent thermal stability. The size and morphology control of microcapsules were realized by adjusting the flow rates of the continuous phase and the hydrophilic monomer EDA aqueous solution. The release of pendimethalin had a sustained release characteristic that was closely related to the morphology of microcapsules. Compared with the pendimethalin emulsifiable concentrate, pendimethalin microcapsules exhibited outstanding herbicidal activity in the weed control experiments. Therefore, pendimethalin microcapsules with tunable properties were successfully obtained from the microfluidic device and showed great potential in agricultural applications.