Immunological Analyses of Whole Blood via “Microfluidic Drifting” Based Flow Cytometric Chip

Backscattering-Based Discrimination of Microparticles Using an Optofluidic Multiangle Scattering Chip

In this research, we designed and fabricated an optofluidic chip for the detection and differentiation of single particles via the combination of backscattered (BSC) and forward-scattered (FSC) or side-scattered (SSC) light intensity. The high sensitivity of BSC light to the refractive index of the particles enabled an effective approach for the differentiation of individual particles based on the type of material. By recording BSC as well as FSC and SSC light intensities from single particles, transiting through the illumination zone in a microfluidic channel, the size and type of material could be detected simultaneously. The analysis of model samples of polystyrene (PS), as a primary microplastic particle, and silica microspheres showed substantially higher BSC signal values of PS because of a larger refractive index compared to the silica. The scatter plots correlating contributions of BSC (FSC-BSC and SSC-BSC) allowed a clear differentiation of PS and silica particles. To demonstrate the great potential of this methodology, two "real-life" samples containing different types of particles were tested as application examples. Commercial toothpaste and peeling gel products, as primary sources of microplastics into effluents, were analyzed via the optofluidic chip and compared to results from scanning electron microscopy. The scattering analysis of the complex samples enabled the detection and simultaneous differentiation of particles such as microplastics according to their differences in the refractive index via distinctive areas of high and low BSC signal values. Hence, the contribution of BSC light measurements in multiangle scattering of single particles realized in an optofluidic chip opens the way for the discrimination of single particles in a liquid medium in manifold fields of application ranging from environmental monitoring to cosmetics.

Sheathless microflow cytometer utilizing two bulk standing acoustic waves

In recent years, microflow cytometry has become a popular research field because of its potential to provide low-cost and disposable chips for complex cell analyses. Herein, we demonstrate a sheathless microflow cytometer which integrates a bulk standing acoustic wave based microchip capable of three dimensional cell focusing. Flow cytometry was successfully demonstrated using this system with a coefficient of variation (CV) of 2.16% with standard calibration beads. The sensitivities calibrated by rainbow beads are 518 MEFL in fluorescein Isothiocyanate (FITC) channel and 264 MEPE in P-phycoerythrin (PE) channels, respectively. The linearities are more than 99% in both channels. The capability of the proposed microflow cytometer is further demonstrated by immunologically labeled leukocytes differentiation in blood. This acoustic-based microflow cytometer did not require any sheath flows or complex structures and can be mass produced. Because of the simple fluid channel, the chip can be easily made pipeless, disposable for applications requiring no cross contamination. Moreover, with the gentle and bio-compatible acoustic waves used, this technique is expected to maintain the viability of cells and other bioparticles.

A Design of Microfluidic Chip with Quasi-Bessel Beam Waveguide for Scattering Detection of Label-Free Cancer Cells

Light scattering detection in microfluidic chips provides an important tool to identify cancer cells without any label processes. However, forward small-angle scattering signals of cells, which are related to their sizes and morphologies, are hard to be detected accurately when scattering angle is less than 11° in microfluidic chips by traditional lighting design due to the influence of incident beam. Therefore, cell's size and morphology being the golden standard for clinical detection may lose their efficacy in recognizing cancer cells from healthy ones. In this article, a novel lighting design in microfluidic chips is put forward in which traditional incident Gaussian beam can be modulated into quasi-Bessel beam by a microprism and waveguide. The quasi-Bessel beam's advantages of nondiffraction theoretically make forward scattering (FS) detection less than 11° possibly. Our experimental results for peripheral blood lymphocytes of human beings and cultured HeLa cells show that the detection rates increase by 47.87% and 46.79%, respectively, by the novel designed microfluidic chip compared to traditional Gaussian lighting method in microfluidic chips. © 2019 International Society for Advancement of Cytometry.

Micro-optics for microfluidic analytical applications

This critical review summarizes the developments in the integration of micro-optical elements with microfluidic platforms for facilitating detection and automation of bio-analytical applications.

Sheathless Microflow Cytometry Using Viscoelastic Fluids

Microflow cytometry is a powerful technique for characterization of particles suspended in a solution. In this work, we present a microflow cytometer based on viscoelastic focusing. 3D single-line focusing of microparticles was achieved in a straight capillary using viscoelastic focusing which alleviated the need for sheath flow or any other actuation mechanism. Optical detection was performed by fiber coupled light source and photodetectors. Using this system, we present the detection of microparticles suspended in three different viscoelastic solutions. The rheological properties of the solutions were measured and used to assess the focusing performance both analytically and numerically. The results were verified experimentally, and it has been shown that polyethlyene oxide (PEO) and hyaluronic acid (HA) based sheathless microflow cytometer demonstrates similar performance to state-of-the art flow cytometers. The sheathless microflow cytometer was shown to present 780 particles/s throughput and 5.8% CV for the forward scatter signal for HA-based focusing. The presented system is composed of a single capillary to accommodate the fluid and optical fibers to couple the light to the fluid of interest. Thanks to its simplicity, the system has the potential to widen the applicability of microflow cytometers.

Integrating Cell Phone Imaging with Magnetic Levitation (i-LEV) for Label-Free Blood Analysis at the Point-of-Living

There is an emerging need for portable, robust, inexpensive, and easy-to-use disease diagnosis and prognosis monitoring platforms to share health information at the point-of-living, including clinical and home settings. Recent advances in digital health technologies have improved early diagnosis, drug treatment, and personalized medicine. Smartphones with high-resolution cameras and high data processing power enable intriguing biomedical applications when integrated with diagnostic devices. Further, these devices have immense potential to contribute to public health in resource-limited settings where there is a particular need for portable, rapid, label-free, easy-to-use, and affordable biomedical devices to diagnose and continuously monitor patients for precision medicine, especially those suffering from rare diseases, such as sickle cell anemia, thalassemia, and chronic fatigue syndrome. Here, a magnetic levitation-based diagnosis system is presented in which different cell types (i.e., white and red blood cells) are levitated in a magnetic gradient and separated due to their unique densities. Moreover, an easy-to-use, smartphone incorporated levitation system for cell analysis is introduced. Using our portable imaging magnetic levitation (i-LEV) system, it is shown that white and red blood cells can be identified and cell numbers can be quantified without using any labels. In addition, cells levitated in i-LEV can be distinguished at single-cell resolution, potentially enabling diagnosis and monitoring, as well as clinical and research applications.

Acoustofluidic Fluorescence Activated Cell Sorter

Selective isolation of cell subpopulations with defined biological characteristics is crucial for many biological studies and clinical applications. In this work, we present the development of an acoustofluidic fluorescence activated cell sorting (FACS) device that simultaneously performs on-demand, high-throughput, high-resolution cell detection and sorting, integrated onto a single chip. Our acoustofluidic FACS device uses the "microfluidic drifting" technique to precisely focus cells/particles three dimensionally and achieves a flow of single-file particles/cells as they pass through a laser interrogation region. We then utilize short bursts (150 μs) of standing surface acoustic waves (SSAW) triggered by an electronic feedback system to sort fluorescently labeled particles/cells with desired biological properties. We have demonstrated continuous isolation of fluorescently labeled HeLa cells from unlabeled cells at a throughput of ∼1200 events/s with a purity reaching 92.3 ± 3.39%. Furthermore, 99.18% postsort cell viability indicates that our acoustofluidic sorting technique maintains a high integrity of cells. Therefore, our integrated acoustofluidic FACS device is demonstrated to achieve two-way cell sorting with high purity, biocompatibility, and biosafety. We believe that our device has significant potential for use as a low-cost, high-performance, portable, and user-friendly FACS instrument.

Shape-controlled synthesis of hybrid nanomaterials via three-dimensional hydrodynamic focusing

Shape-controlled synthesis of nanomaterials through a simple, continuous, and low-cost method is essential to nanomaterials research toward practical applications. Hydrodynamic focusing, with its advantages of simplicity, low-cost, and precise control over reaction conditions, has been used for nanomaterial synthesis. While most studies have focused on improving the uniformity and size control, few have addressed the potential of tuning the shape of the synthesized nanomaterials. Here we demonstrate a facile method to synthesize hybrid materials by three-dimensional hydrodynamic focusing (3D-HF). While keeping the flow rates of the reagents constant and changing only the flow rate of the buffer solution, the molar ratio of two reactants (i.e., tetrathiafulvalene (TTF) and HAuCl4) within the reaction zone varies. The synthesized TTF-Au hybrid materials possess very different and predictable morphologies. The reaction conditions at different buffer flow rates are studied through computational simulation, and the formation mechanisms of different structures are discussed. This simple one-step method to achieve continuous shape-tunable synthesis highlights the potential of 3D-HF in nanomaterials research.