Chuanjin Cui

Droplet microfluidics has been widely used in biological, chemical, and medical research owing to its advantages of miniaturization, high throughput, and low reagent consumption. However, limited sensitivity and optical path length in on-chip absorbance detection remain major challenges for droplet-based microfluidic analysis. Traditional absorbance detection suffers from low sensitivity due to the extremely short optical path in microfluidic channels, while existing optical path extension methods have drawbacks such as complex fabrication, easy droplet rupture, or strict incident angle requirements. To address these issues, this study developed a droplet microfluidic absorbance detection platform integrating optical fibers, on-chip micromirrors, external fluidic actuation, and an absorbance detection module. Microchannel sidewalls filled with low-melting-point metal act as mirrors; the multi-reflection optical path, combined with optical fibers and micromirrors, compensates for insufficient light manipulation and effectively extends the absorption path length, improving sensitivity and accuracy. Using this method, the detection limit for methylene blue solution was 20 μM, and the sensitivity for Escherichia coli (E. coli) suspension was doubled compared with traditional Nanodrop OD600 measurement. This device features low fabrication difficulty and cost and stable detection, providing a proof-of-concept strategy for enhanced absorbance detection in droplet microfluidic systems.

Particle separation technology is widely applied in fields such as biomedicine, chemical analysis, and environmental monitoring. As an efficient particle separation method, surface acoustic wave (SAW)-based microfluidic technology enables precise particle manipulation and separation by establishing an acoustic field within microchannels, offering advantages such as device miniaturization, low cost, and ease of integration. This study proposes a novel separation method based on the synergistic interaction between deterministic lateral displacement (DLD) and tilted standing surface acoustic wave. By reconfiguring the function of the DLD array into ‘sheathless focusing units,’ a highly ordered particle inlet flow is provided for subsequent acoustic separation. Experimental results demonstrate that the integrated device successfully achieved high-efficiency separation of 5 µ m and 15 µ m particles, with both purity and efficiency exceeding 98%. Compared to single-technique approaches, this synergistic strategy significantly enhances separation purity, efficiency, and operational stability under sheathless conditions. This study provides a feasible solution for the application of acoustofluidic technology in the field of particle separation, offering certain theoretical reference value and engineering application potential.

In recent years, the point-of-care testing (POCT) device for nucleic acid detection has received extensive attention. POCT device provides rapid, high sensitivity and accuracy of on-site diagnosis and can quantify the nucleic acid in clinical samples in real time. The integration of microfluidics ensures accurate fluid control, minimizes sample volume, and improves detection efficiency. In addition, POCT devices can conduct multichannel analysis, facilitate continuous monitoring, and provide comprehensive quantitative data. Due to its portability, cost-effectiveness, and ease of use, POCT device represents a promising solution for extensive, reliable, and timely nucleic acid detection in various medical environments. This review summarizes the research and development of nucleic acid detection POCT devices based on microfluidic technology in recent years, and the development trend of the device has prospected.