Development of Coplanar Electro-Wetting Based Microfluidic Sorter to Select Micro-Particles in High Volume Throughput at Milliliter Amount within Twenty Minutes

Direct count of fluorescent microspheres in a microfluidic chip based on the capillary electrophoresis method

Fluorescent microspheres (FMs) are tiny particles with special functions that are widely employed in biological research. Counting of microscale FMs is a great challenge by capillary electrophoresis. Herein we developed a method to count 2 μm FMs based on a microfluidic chip with a gradual change in inner size. Such a microfluidic chip can inhibit sample blocking at the inlet of the capillary. The results showed that FMs migrated in the wide part of the microchannel side by side, and then passed through the narrow part one by one. There was a linear relationship between the number of peaks in the electropherogram and concentration of FMs if they were running in the microchannel for more than 20 min. A high separation voltage may lead to aggregation of FMs in the microchannels, and about 2 × 10⁴ FMs can be counted within 30 min by this microfluidic chip.

iSort enables automated complex microfluidic droplet sorting in an effort to democratize technology

Fluorescence-activated droplet sorting (FADS) is a widely used microfluidic technique for high-throughput screening. However, it requires highly trained specialists to determine optimal sorting parameters, and this results in a large combinatorial space that is challenging to optimize systematically. Additionally, it is currently challenging to track every single droplet within a screen, leading to compromised sorting and "hidden" false-positive events. To overcome these limitations, we have developed a setup in which the droplet frequency, spacing, and trajectory at the sorting junction are monitored in real time using impedance analysis. The resulting data are used to continuously optimize all parameters automatically and to counteract perturbations, resulting in higher throughput, higher reproducibility, increased robustness, and a beginner-friendly character. We believe this provides a missing piece for the spreading of phenotypic single-cell analysis methods, similar to what we have seen for single-cell genomics platforms.

Modeling, simulation, and optimization of electrowetting-on-dielectric (EWOD) devices

With widespread research studies on electrowetting-on-dielectric (EWOD) for droplet manipulation in the field of lab-on-a-chip, how to improve the driving capability of droplets has increasingly attracted enormous interest. Aiming to decrease driving voltages and improve driving effectiveness, this paper studies the modeling, simulation, and optimization of EWOD devices. The theoretical model is refined mainly in consideration of the saturation effect of the contact angle and then verified by both simulation and experiments. As a design guide to decrease the driving voltage, a theoretical criterion of droplet splitting, the most difficult one among four basic droplet manipulations, is developed and then verified by experimental results. Moreover, a novel sigmoid electrode shape is found by the optimization method based on finite element analysis and achieves better driving effectiveness and consistent bidirectional driving capability, compared with the existing electrode shapes. Taken together, this paper provides an EWOD analysis and optimization method featuring a lower voltage and a better effectiveness and opens up opportunities for optimization designs in various EWOD-based applications.

Electrowetting-on-dielectric (EWOD): Current perspectives and applications in ensuring food safety

Digital microfluidic (DMF) platforms have contributed immensely to the development of multifunctional lab-on-chip systems for performing complete sets of biological and analytical assays. Electrowetting-on-dielectric (EWOD) technology, due to its outstanding flexibility and integrability, has emerged as a promising candidate for such lab-on-chip applications. Triggered by an electrical stimulus, EWOD devices allow precise manipulation of single droplets along the designed electrode arrays without employing external pumps and valves, thereby enhancing the miniaturization and portability of the system towards transcending important laboratory assays in resource-limited settings. In recent years, the simple fabrication process and reprogrammable architecture of EWOD chips have led to their widespread applications in food safety analysis. Various EWOD devices have been developed for the quantitative monitoring of analytes such as food-borne pathogens, heavy metal ions, vitamins, and antioxidants, which are significant in food samples. In this paper, we reviewed the advances and developments in the design of EWOD systems for performing versatile functions starting from sample preparation to sample detection, enabling rapid and high-throughput food analysis.