This paper reports a novel method, opto-acousto-fluidic microscopy, for label-free detection of droplets and cells in microfluidic networks. Leveraging the optoacoustic effect, the microscopic system possesses capabilities of visualizing flowing droplets, analyzing droplet contents, and detecting cell populations encapsulated in droplets via the sensing of acoustic waves induced by the intrinsic light-absorbance of matter.

In this work, we develop a new opto-acouto-fludic microsopic system, which employs a high-speed one-dimensional galvanometer scanner and an ultrafast pulse laser (600 kHz). The new system has achieved a high two-dimensional frame rate of up to 2500 Hz with a lateral resolution of 1.7 μm and an axial resolution of 36 μm at the imaging plane. To demonstrate the improved performance of the new system compared to our previous one, we carried out experiments to image the flowing droplets generated with T-junction and flow focusing configurations. We also successfully imaged dynamic migration of magneto particles subjected to non-uniform magnetic field in the microchannel. The results suggest that our new system has sufficient spatiotemporal resolutions to carry out studies for high throughput microfluidic applications.

Acute leukemia (AL) is one of the top life-threatening diseases. Accurate typing of AL can significantly improve its prognosis. However, conventional methods for AL typing often require cell staining, which...

Refractive index (RI) sensing plays an important role in analytical chemistry, medical diagnosis, and environmental monitoring. The optofluidic technique is considered to be an ideal tool for RI sensor configuration for its high integration, high sensitivity, and low cost. However, it remains challenging to achieve RI measurement in real time with high sensitivity and low detection limit (DL) simultaneously. In this work, we design and fabricate a RI sensor with an arched optofluidic waveguide by monitoring the power loss of the light passing through the waveguide, which is sandwiched by the air-cladding and the liquid-cladding under test, we achieve RI detection of the sample in real time and with high sensitivity. Furthermore, both numerical simulation and experimental investigation show that our RI sensor can be designed with different geometric parameters to cover multiple RI ranges with high sensitivities for different applications. Experimental results illustrate that our sensor is capable to achieve a superior sensitivity better than −19.2 mW/RIU and a detection limit of 5.21×10−8 RIU in a wide linear dynamic range from 1.333 to 1.392, providing a promising solution for real-time and high-sensitivity RI sensing.

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