Highly efficient treatment of industrial wastewater by solution plasma with low environmental load.

Advanced oxidation techniques are efficient processes to dispose of organic contaminants in industrial wastewater with low secondary pollution. The solution plasma technique was featured as an advanced oxidation technique with low secondary pollution and high efficiency. However, the solution plasma technique reported previously could only treat wastewater of less than 200 mL owing to the limited plasma generated by only one pair of electrodes. In this work, multiple pairs of electrodes were installed at the bottom of the reaction vessel to generate plasma for decomposing methylene blue trihydrate (MB) and methyl orange (MO) solutions with a batch amount of 18 L/batch. The solution plasma technique was compared with direct ozonation in decomposition of MB and MO wastewater. A surprising phenomenon is that MO was more readily decomposed than MB by using direct ozonation, whereas the removal of MO was too low, and MB was more readily decomposed than MO by using the solution plasma technique.

Sequential operation droplet array: an automated microfluidic platform for picoliter-scale liquid handling, analysis, and screening.

This contribution describes a sequential operation droplet array (SODA) system, a fully automated droplet-based microfluidic system capable of performing picoliter-scale liquid manipulation, analysis, and screening. The SODA system was built using a tapered capillary-syringe pump module and a two-dimensional (2D) oil-covered droplet array installed on an x-y-z translation stage. With the system, we developed a novel picoliter-scale droplet depositing technique for forming a 2D picoliter-droplet array. On this basis, an automated droplet manipulation method with picoliter precision was established using the programmable combination of the capillary-based liquid aspirating-depositing and the moving of the oil-covered droplet array, the so-called "aspirating-depositing-moving" (ADM) method. Differing from the previously reported droplet systems based on microchips, microcapillaries, or digital microfluidics, this method can achieve complete and flexible droplet manipulations, including droplet assembling, generation, indexing, transferring, splitting, and fusion in the picoliter range, endowing the present system with ultralow sample/reagent consumptions and substantial versatility in analysis and screening for multiple different samples. To demonstrate its feasibility and versatility, we applied the SODA system in multiple experiments required in drug screening, including the screening of inhibitors for capases-1 from a chemical library, the measurement of IC50 values for the identified inhibitors, and the screening of the synergistic effect of multiple inhibitors. In the experiments, the consumptions of samples and reagents are only 60-180 pL for each droplet microreactor, which are commonly 3-5 orders of magnitude lower than those of conventional multiwell plate systems, and 1-2 orders of magnitude lower than other droplet-based microfluidic systems for multiple sample screening. The ability of the SODA system in performing complicated and multistep droplet manipulations was further demonstrated in the serial dilution of nanoliter-scale inhibitor droplets with concentrations spanning 6 orders of magnitude for IC50 profiling, which includes droplet generation, indexing, splitting, transferring, and fusion with picoliter precision.

Droplet-based microfluidic flow injection system with large-scale concentration gradient by a single nanoliter-scale injection for enzyme inhibition assay.

We described a microfluidic chip-based system capable of generating droplet array with a large scale concentration gradient by coupling flow injection gradient technique with droplet-based microfluidics. Multiple modules including sample injection, sample dispersion, gradient generation, droplet formation, mixing of sample and reagents, and online reaction within the droplets were integrated into the microchip. In the system, nanoliter-scale sample solution was automatically injected into the chip under valveless flow injection analysis mode. The sample zone was first dispersed in the microchannel to form a concentration gradient along the axial direction of the microchannel and then segmented into a linear array of droplets by immiscible oil phase. With the segmentation and protection of the oil phase, the concentration gradient profile of the sample was preserved in the droplet array with high fidelity. With a single injection of 16 nL of sample solution, an array of droplets with concentration gradient spanning 3-4 orders of magnitude could be generated. The present system was applied in the enzyme inhibition assay of ß-galactosidase to preliminarily demonstrate its potential in high throughput drug screening. With a single injection of 16 nL of inhibitor solution, more than 240 in-droplet enzyme inhibition reactions with different inhibitor concentrations could be performed with an analysis time of 2.5 min. Compared with multiwell plate-based screening systems, the inhibitor consumption was reduced 1000-fold.