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Recently, microparticles have been used as nanoporous membranes in microfluidic devices, contributing to various bioassays on a chip. Here, we report a self-assembled particle membrane (SAPM) integrated microfluidic device that concentrates particles into an aimed microchamber array by using evaporation-driven capillary forces, and manipulates the chemical environment of the microchamber array by sequentially introducing different solutions. We demonstrate that the SAPM-integrated microchamber array can concentrate microparticles and microbial cells up to 120-fold for 2 h and 35-fold for 1 h, respectively, resulting in remarkably high concentration factors. Additionally, we demonstrate that the microchamber array has high potential as a chemostat-like bioreactor because it can actively manipulate the initial seeding number of bacterial cells and continuously supply and sequentially switch fresh nutrients to them. As an example of various applications, the chemostat-like bioreactor was used as a microbial biosensor platform that enabled microbial sensor cells to respond more efficiently and rapidly to external stimuli, such as heavy metal ions. This was made possible by almost eliminating the initial lag phase that dramatically shortened the whole assay time. Notably, the SAPM-integrated microchamber array not only facilitates various bioassays on a chip but also provides unprecedented experimental platforms to study microorganisms in a simple and convenient manner. [ABSTRACT FROM AUTHOR]

This communication presents a microfluidic method for size-based cell sorting, which provides a simple and robust approach for cell cycle synchronization by manual and stand-alone operation. [ABSTRACT FROM AUTHOR]

Progress in neurological research has experienced bottlenecks owing to the limited availability of purified primary neurons. Since neuronal cells are non-proliferative, it is necessary to obtain purified neurons from animal models or human patients for experimental work. However, currently available methods for purifying primary neurons are time-consuming (taking approximately 1 week), and suffer from insufficient viability and purity. Here, we report a method for rapid enrichment of neurons from the mouse embryonic dorsal root ganglion (DRG), using a fully-automated continuous centrifugal microfluidics (CCM) based neuron purification disc (NPD). Non-neuronal cells were removed via negative depletion by combining density gradient centrifugation and immunomagnetic separation. The CCM-NPD platform enables effective isolation of intact neurons within 13 min, which is approximately 800 times faster than the conventional chemical purification method. Furthermore, the neurons purified using the CCM-NPD platform showed better neurite growth, along with higher viability (93.5%) and purity (97.0%) after 1 week of culture, compared to the chemical purification method. Therefore, the proposed automated and rapid system yields purified DRG neurons with high viability and purity, while avoiding the use of harsh chemicals. We believe this system will significantly mitigate the shortage of purified primary neurons and advance neurological research. [ABSTRACT FROM AUTHOR]

Nanoparticle separation techniques are of significant importance in nanoscience and nanotechnological applications and different concentration gradients, electric/dielectric forces, flow/pressure fields, and acoustic waves have been intensively investigated. However, precise separation of nanoparticles has many technical challenges in terms of sizes, shapes, and material properties, limiting the separation resolution, capability, applicability, throughput and so on. In this study, we present a microfluidic device for continuous separation of nanoparticles by combining diffusiophoresis (DP) and electrophoresis (EP) to achieve high separation performance. Concentration gradients formed from sodium chloride (NaCl) and potassium acetate (K-acetate) passively drive the diffusiophoretic migration of nanoparticles. Simultaneously, a low electric potential is additionally applied to impose a synergistic effect on nanoparticle migration by size and surface charge, which is called low-electric-potential-assisted DP (LEPDP). Using a LEPDP-based separation device, we demonstrate the separation of nanoparticles having different sizes (diameters of 500, 200, and 50 nm) and under different surface-charge conditions (carboxylated polystyrene, silica, and polylactide). The resulting separation performance exceeded 95%, in terms of size uniformity, which is about two times better than that obtained using DP alone. We also emphasize that the enhancement of separation performance only needs a small voltage (<1 V), thereby demonstrating that our multiphysical approach could be utilized for high-resolution and portable nanoparticle separation on a chip without the side effects associated with high electric fields. Lastly, we ensure that rapid and precise bio/chemical sensing and analysis of various nanosized particles would be envisioned by strategically combining two nonlinear but synergistic migration effects. [ABSTRACT FROM AUTHOR]