Flow cytometry is a popular technique for counting and sorting individual cells. This study presents and demonstrates a new cell counting/sorting system integrated with several essential components including a micromachined flow cytometer chip device, an optical detection system and a data analysis and control system to achieve the functions of cell sample injection, optical signal detection and cell collection. By using MEMS technology, we have integrated several microfluidic components such as micro pneumatic pumps/valves onto a polymer-based chip device. Three pneumatic micropumps are used to provide the hydrodynamic driving force for both sample and sheath flows such that hydrodynamic flow focusing can be achieved, and a micro flow switch device comprising three pneumatic microvalves located downstream of the micro sample flow channel is used for cell collection. Cell samples of human lung cancer cells labelled with commercially available fluorescent dyes have been detected and collected successfully utilizing the developed device. The real-time image of dye-labelled cell samples being excited and detected can be monitored and observed through the LCD panel by a custom designed CCD/APD holder and moving stage. Finally, micro flow switch devices were used to successfully sort the cells into the desired outlet channel, and the counting results of the specific cell samples were monitored through the counting panel. The current study focuses on the setup of the overall system. The proposed flow cytometer system has several advantages such as portability, low cost and easy operation process. The size of the system is 37 cm × 16 cm × 18 cm and the weight is 3.5 kg. The error rate of counting and sorting was 1.5% and 2%, respectively. The sorting frequency of the microvalve device is calculated to be 120 cells min−1. The developed microfluidic chip device could be a promising tool for cell-based application fields such as profiling, counting and sorting.

This study presents a new suction-type, pneumatically driven microfluidic device for liquid delivery and mixing. The three major components, including two symmetrical, normally closed micro-valves and a sample transport/mixing unit, are integrated in this device. Liquid samples can be transported by the suction-type sample transport/mixing unit, which comprised a circular air chamber and a fluidic reservoir. Experimental results show that volume flow rates ranging from 50 to 300 ll/min can be precisely controlled during the sample transportation processes. Moreover, the transport/mixing unit can also be used as a micro-mixer to generate efficient mixing between two reaction chambers by regulating the time-phased deformation of the polydimethylsiloxane (PDMS) membranes. A mixing efficiency as high as 98.4% can be achieved within 5 s utilizing this prototype pneumatic microfluidic device. Consequently, the development of this new suction-type, pneumatic microfluidic device can be a promising tool for further biological applications and for chemical analysis when integrated into a micro-total analysis system (l-TAS) device.

Micromixers are commonly employed for chemical or biological analysis in micro-total-analysis-system applications. Mixing performance is important since it allows for rapid and efficient chemical or biological reactions. This study, therefore, reports a new vortex-type micromixer which utilizes pneumatically driven membranes to generate a swirling flow in a mixing chamber. The micromixer chip is fabricated by using micro-electro-mechanical-systems technology as well as a computer-numerically controlled machine for rapid prototyping. Two different membrane layouts and driving frequencies are evaluated to determine if there is a significant improvement in the mixing performance. Experimental results indicate that the mixing efficiency increases with increasing driving frequencies and the mixing time is reduced by approximately tenfold as the driving frequency increases from 1 to 6 Hz. A mixing efficiency as high as 95% can be achieved, in time periods as short as 0.6 and 0.7 s for the two-and four-membrane layouts, respectively. Furthermore, numerical simulations are also employed to characterize the swirling flow field, the concentration distribution and the mixing mechanism as well. Combined experimental data and numerical results illustrate the fluid dynamic phenomena that allow for rapid mixing in this vortex-type micromixer.

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This paper reports a new polymeric, aspheric SU-8 microlens array using a soft replica molding method and its application to cell counting. A bio-detection system comprising the SU-8 microlens array with its three-dimensional convex geometry, a micro flow cytometer chip and an optical detection module is demonstrated. A polymethyl methacrylate (PMMA) template is first fabricated and then the SU-8 microlens array is replicated using a new fabrication process. The developed array has four sizes of microlens, with diameters of 50, 100, 150 and 200 µm. Experimental results show that the surface roughness of the microlens was only 10.2 nm for the SU-8 polymer material. The microlens had good surface uniformity and excellent optical properties with calculated focal lengths ranging from tens to hundreds of micrometers, depending on their dimensions. A microlens with a high numerical aperture ranging from 0.3 to 0.75 was achieved. The microlens array can be used to increase the efficiency of the optical detection, allowing high-resolution detection and providing a high signal-to-noise ratio. The microlens array has the potential to be widely used for optical or biophotonic applications and for the integration of microfluidic devices. In order to demonstrate its capability, the developed microlens array was integrated with a micro flow cytometer for cell counting applications. Successful counting of fluorescent-labeled human lung cancer cells is demonstrated using the developed method.

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