Micro Flow Cytometer Chip Integrated with Micro-Pumps/Micro-Valves for Multi-Wavelength Cell Counting and Sorting

Abstract

Flow cytometry is a popular technique for counting and sorting of individual cells. This study presents a new chip-based flow cytometer capable of cell injection, counting and switching in an automatic format. The new microfluidic system is also capable of multi-wavelength detection of fluorescence-labeled cells by integrating multiple buried optical fibers within the chip. Instead of using large-scale syringe pumps, this study integrates micro-pumps and micro-valves to automate the entire cell injection and sorting process. By using pneumatic serpentine-shape (S-shape) micro-pumps to drive sample and sheath flows, the developed chip can generate hydrodynamic focusing to allow cells to pass detection regions in sequence. Two pairs of optical fibers are buried and aligned with the microchannels, which can transmit laser light sources with different wavelengths and can collect induced fluorescence signals. The cells labeled with different fluorescent dyes can be excited by the corresponding light source at different wavelengths. The fluorescence signals are then collected by avalanche photodiode (APD) sensors. Finally, a flow switching device composed of three pneumatic micro-valves is used for cell sorting function. Experimental data show that the developed flow cytometer can distinguish specific cells with different dye-labeling from mixed cell samples in one single process. The target cell samples can be also switched into appropriate outlet channels utilizing the proposed microvalve device. The developed microfluidic system is promising for miniature cell-based biomedical applications.

Multi-wavelength microflow cytometer using groove-generated sheath flow

“…The locations of the fibers surrounding the interrogation region was a compromise between the need to position the fibers near the fluidic core to deliver and collect light at multiple wavelengths and the size of the individual fibers themselves, which limited their proximity to each other. The methods reported previously for using fibers with flow cytometers were not applicable for alignment of multiple fibers focused on one location in the microfluidic channel 13,37–39. Therefore, channel width was set to 390 μm to allow enough room to align the fiber tips around the interrogation region.…”

A microfluidic passive pumping Coulter counter

“…Microfluidic methods for hydrodynamic focusing have been reported before Nieuwenhuis et al (2004); Simonnet and Groisman (2006); Chang et al (2007); Hairer and Vellekoop (2007); Yang and Hsieh (2007); Rodriguez-Trujillo et al (2008); Scott et al (2008); Watkins et al (2009), but none have used passive pumping. As shown in Figure 2, the relative radii of droplets on the focusing and sample inlets affects the width of the outer focusing streams and the inner sample stream.…”

Detection of unlabeled particles in the low micrometer size range using light scattering and hydrodynamic 3D focusing in a microfluidic system

“…Building on previously published work [], we designed and fabricated a two‐layer channel structure (consisting of PDMS and SU‐8 on a glass substrate, see Fig. B) to enable 3D hydrodynamic focusing, while, at the same time, allowing for the possibility to integrate microoptical elements.…”