Microfluidic-based sheath flow focusing methods have been widely used for efficiently isolating, concentrating, and detecting pathogenic bacteria for various biomedical applications due to their enhanced sensitivity and exceptional integration. However, such a microfluidic device usually needs complicated device fabrication and sample dilution, hampering the efficient and sensitive identification of target bacteria. In this study, we develop and fabricate a sheath-assisted and pneumatic-induced nano-sieve device for achieving the improved on-chip concentration and sensitive detection of Staphylococcus aureus (MRSA). The optimized nanochannel design with diverging configuration is beneficial to the regulation of the hydrodynamic flow while the sheath flow is focusing the sample to the confined region as expected. Per the experimental finding, a high flow ratio (sheath flow/sample flow) presents enhanced target concentration by comparing with a low flow ratio. With this setup, MRSA bacteria with an extremely low concentration of ∼100 CFU mL-1 are successfully and sensitively detected under a fluorescence microscope, less than 30 min, demonstrating a reliable sheath-enhanced concentration and on-chip detection for target bacteria. Additionally, the theoretical model introduced here further rationalizes the working principle of our nano-sieve device, potentially guiding the optimization of next generation devices for highly sensitive and accurate on-chip bacteria detection at a much lower concentration level below 100 CFU mL-1.

中文翻译：

---

鞘层增强浓度和芯片上检测细菌，从极低浓度水平开始。


基于微流体的鞘流聚焦方法因其增强的灵敏度和出色的集成性而被广泛用于各种生物医学应用中的高效分离、浓缩和检测病原菌。然而，这种微流控装置通常需要复杂的装置制造和样品稀释，阻碍了目标细菌的高效和灵敏识别。在这项研究中，我们开发和制造了一种鞘辅助和气动诱导纳米筛装置，以实现对金黄色葡萄球菌 （MRSA） 的改进片上浓度和灵敏检测。具有发散配置的优化纳米通道设计有利于流体动力学流的调节，而鞘流如预期的那样将样品聚焦到受限区域。根据实验结果，与低流速比相比，高流速比（鞘流/样品流）表现出更高的目标浓度。通过这种设置，在荧光显微镜下，不到 30 分钟即可成功、灵敏地检测到浓度极低（∼100 CFU mL-1）的 MRSA 细菌，证明对目标细菌具有可靠的鞘增强浓度和芯片检测。此外，这里介绍的理论模型进一步合理化了我们纳米筛设备的工作原理，有可能指导下一代设备的优化，以便在低于 100 CFU mL-1 的低浓度水平下进行高灵敏度和准确的片上细菌检测。