Effective Cell and Particle Sorting and Separation in Screen-Printed Continuous-Flow Microfluidic Devices with 3D Sidewall Electrodes

In recent years, microfluidic dielectrophoresis (DEP) devices, as one of the most promising tools for cell and particle sorting and separation, are facing the bottleneck in the development of practical products due to the high-cost yet low-yield device manufacturing via traditional microelectromechanical systems (MEMS) and the challenge of maintaining the cell viability during DEP treatment. In this paper, we demonstrate a facile, low-cost, and high-throughput method of constructing continuous-flow microfluidic DEP devices via screen-printing technology. The new device configuration and operation strategy not only facilitate cell and particle sorting and separation using 3D electrodes as sidewalls of microchannel but also improve cell viability by reducing the exposure time of cells to high electrical-field gradients. Furthermore, we propose and validate a semiempirical formula with which to simplify the complicated calculation and plotting of DEP spectra. As a consequence, the optimal DEP parameters and crossover frequencies can be obtained directly using our devices instead of typical electrorotation method. To evaluate the performance of a screen-printed continuous flow microfluidic DEP device, a suspension containing polystyrene (PS) microspheres and erythrocytes is used as the biosample. Our results show that a high sorting efficiency (ca. 93%) with a high cell viability (hemolysis ratio of <4.8%) can be achieved, indicating the excellent performance and promising application of such devices for cell and particle sorting and separation

Enhancement of Enzymatic Activity Using Microfabricated Poly(ε-caprolactone)/Silica Hybrid Microspheres with Hierarchically Porous Architecture

In this paper, we present a novel and facile microfluidic method to fabricate hierarchically porous poly­(ε-caprolactone)/silica hybrid microspheres and further investigate in detail their performance as enzyme carriers by three famous proteins and enzymes. Because of the synergy effect between sol–gel process and solvent extraction in microdroplets, hierarchically porous architecture can be formed in situ without the use of porogens and templates. More importantly, the surface porosity or the specific surface area of such microspheres can be precisely tuned via adjusting the hydrolysis/condensation rate by ammonia catalyst and thus the competition between the two above-mentioned processes. Fluorescein isothiocyanate-bovine serum albumin, alcohol dehydrogenase, and superoxide dismutase are immobilized via either physical adsorption or covalent binding to evaluate the performance of hierarchically porous microspheres as enzyme carriers. All the qualitative and quantitative data including fluorescence images, enzymatic activity, immobilization yield, and activity yield prove that enzymes covalently immobilized on hierarchically porous microspheres exhibit the optimal immobilization capacity, enzymatic activity, stability, and reusability, which shows very promising application of such microspheres in enzymatic catalysis