Label-free image-encoded microfluidic cell sorter with a scanning Bessel beam

Area of Science:

• Biomedical Engineering
• Microfluidics
• Optical Cell Sorting

Background:

• Conventional microfluidic cell sorters face limitations due to one-dimensional flow confinement, leading to blurred cell images and hindering feature-based sorting.
• Gaussian laser beams used in current systems have a limited depth of focus, causing cell distribution outside the focal plane.

Purpose of the Study:

• To develop a microfluidic cell sorter utilizing a Bessel-Gaussian beam for an ultra-long depth of focus, improving cell image quality.
• To enable label-free cell sorting based on extracted features from photomultiplier tube (PMT) detector output waveforms.

Main Methods:

• Implementation of a Bessel-Gaussian beam illumination system within a microfluidic device to achieve an extended depth of focus.
• Development of a label-free sorting mechanism that analyzes temporal waveforms from a PMT detector.
• Utilizing a temporal-spatial transformation algorithm for offline reconstruction of cell images.

Main Results:

• >85% of cells passing through the system produced focused images, significantly reducing blurring.
• High sorting purity achieved for polystyrene beads (97%), SKNO1 leukemia cells (97%), and *Scenedesmus* green algae (98%).
• Strong correlations were observed between PMT output temporal waveforms and cell image features, validated by image reconstruction.

Conclusions:

• The Bessel-Gaussian beam cell sorter effectively overcomes the depth-of-focus limitations of conventional systems.
• Label-free cell sorting based on PMT waveform analysis is a viable and accurate method for cell characterization and separation.
• This technology offers a low-cost, high-information, and disposable solution for advanced cell sorting applications.