Surface-Enhanced Raman Scattering (SERS) is emerging as a promising strategy for the quantification of immunoglobulin G (IgG) due to its inherent high sensitivity and specificity; however, it remains challenging to integrate SERS detection with a microfluidic system in a simple, efficient and low-cost manner. Here, we report on a novel bifunctional plasmonic-magnetic particle-based immunoassay, in which plasmonic nanoparticles act as soluble SERS immunosubstrates, whereas magnetic particles are for promoting micromixing in a microfluidic chip. With this novel SERS immunosubstrate in conjunction with the unique microfluidic system, we could substantially reduce the assay time from 4 hours to 80 minutes as well as enhance the detection specificity by about 70% in comparison to a non-microfluidic immunoassay. Compared to previous microfluidic SERS systems, our strategy offers a simple microfluidic chip design with only one well for mixing, washing and detection.

Current diagnosis of infectious diseases such as Hendra virus (HeV) relies mostly on laboratory-based tests. There is an urgent demand for rapid diagnosis technology to detect and identify these diseases in humans and animals so that disease spread can be controlled. In this study, an integrated lab-on-a-chip device using a magnetic nanoparticle immunoassay is developed. The key features of the device are the chaotic fluid mixing, achieved by magnetically driven motion of nanoparticles with the optimal mixing protocol developed using chaotic transport theory, and the automatic liquid handling system for loading reagents and samples. The device has been demonstrated to detect Hendra virus antibodies in dilute horse serum samples within a short time of 15 minutes and the limit of detection is about 0.48 ng ml. The device platform can potentially be used for field detection of viruses and other biological and chemical substances.

The bead-based immunoassay requires not only efficient mixing but also good control of bead-surfacearea-to-sample-volume ratio to realise accurate and reproducible detection of low concentration samples. This paper reports the development of a microfluidic platform with the reproducible and efficient bubbleinduced micromixing for bead disaggregation and immunoassay of prostate-specific antigen (PSA). The platform consists of a microfluidic chip with a microchamber and rectangular traps for capturing air bubbles and a home-made controller to generate sound wave using an external piezo transducer. Methods for reproducible bubble formation and bubble size control during mixing are explored. The influence of driving voltage, PDMS thickness and the substrate material on the mixing efficiency is characterised by mixing a fluorescence dye and a buffer solution. The optimised acoustic microstreaming is able to break clusters with hundreds of beads and homogenise individual beads over the microchamber. Immunoassay with efficient micromixing has been applied to PSA immunoassay with greatly reduced detection time. This study provides a practical guide for the design and development of the bubble-induced acoustic micromixers for bead disaggregation and on-chip immunoassays.

The rapid and reliable detection of chemical and biological agents in the field is important for many applications such as national security, environmental monitoring, infectious diseases screening, and so on. Current commercially available devices may suffer from low field deployability, specificity, and reproducibility, as well as a high false alarm rate. This paper reports the development of a portable lab-on-a-chip device that could address these issues. The device integrates a polymer multiplexed microchip system, a contactless conductivity detector, a data acquisition and signal processing system, and a graphic/user interface. The samples are pre-treated by an on-chip capillary electrophoresis system. The separated analytes are detected by conductivity-based microsensors. Extensive studies are carried out to achieve satisfactory reproducibility of the microchip system. Chemical warfare agents soman (GD), sarin (GB), O-ethyl S-[2-diisoproylaminoethyl] methylphsophonothioate (VX), and their degradation products have been tested on the device. It was demonstrated that the device can fingerprint the tested chemical warfare agents. In addition, the detection of ricin and metal ions in water samples was demonstrated. Such a device could be used for the rapid and sensitive on-site detection of both chemical and biological agents in the future.

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