Liquid handling and actuation by means of controlling surface tension has proven to have many advantages in small-scale applications due to the surface tension force dominance over body forces. In 1875, Lippmann first explored the phenomenon of the surface tension of liquids modulated with an electric field, which is called an electrowetting effect. When an electric potential is applied between a liquid and a solid electrode, the charge redistribution modifies the surface tension at the liquid−solid interface where the like-charge repulsion decreases the work by expanding the surface area. Due to the benefits of large forces in micro/meso scales, a fast response time in the range of microseconds, and low-power operation, the electrowetting technology has been used for numerous applications, including lab-on-a-chip, electronic display, thermal management, energy harvesting, and surface science.

In this talk, a broad perspective of the electrowetting technology will be presented from materials to its optics and solar applications. A novel high-capacitance dielectric material, called an ion gel, is first introduced which not only offers 2 to 3 orders higher capacitance (c ≈ 10 μF/cm²) than that of conventional dielectrics such as SiO₂, but also is simply fabricated by either a spin or dip-coating method. This high-capacitance ion gel dielectric is used for an electrowetting-driven liquid prism that achieved the highest beam steering performance ever demonstrated. We further discuss an arrayed form of the liquid prisms with a large aperture area and potential applications for a tunable Fresnel lens and solar indoor lighting.

In this work, we introduce a novel microdevice capable of single-step neutrophil sorting from whole blood directly for multiplexed functional phenotyping (chemotaxis and NETosis) (Fig. 1A). Diabetes mellitus (DM) is a metabolic disorder characterized by chronic hyperglycaemia, resulting in increased oxidative stress, chronic low-grade inflammation and endothelial dysfunction [1]. Neutrophils are key effector cells of the innate immunity, and are known to play a pivotal role in diabetic pathophysiology [2]. However, study of neutrophil dysfunctions remains technically challenging due to difficulties in isolating “touch-free” neutrophils in their native state using conventional leukocyte isolation methods (density gradient centrifugation and blood lysis). Microfluidics technologies have been recently developed for neutrophil studies, but require additional leukocyte preparation or manual washing steps to efficiently purify neutrophils from whole blood [3, 4].  Herein, we report an integrated microfluidics biochip for single step neutrophil purification and functional phenotyping using small blood volume (fingerprick) for point-of-care diabetes testing.

The microdevice is fabricated using polydimethylsiloxane (PDMS) and consists of a margination channel, 20×20 µm (W×H) with 2 side chambers 400×20 µm (W×H). As whole blood (~10 µL) is pumped through the straight channel, deformable red blood cells (RBCs) migrate laterally towards the axial centre (Fahraeus effect), resulting in margination of other cell types (platelets and leukocytes) into the smaller side channels (Fig. 1B). Neutrophils are selectively captured in the anti-CD66b-functionalized surface and then exposed to a stable diffusion-based gradient of either chemoattractant (fMLP) or calcium ionophore (AZ23187), to study chemotaxis or formation of neutrophil extracellular traps (NETosis) respectively (Fig. 1C). Time-lapse imaging and single cell image analysis are performed to probe chemotaxis (migrating cells and chemotactic velocity) and NETosis (nuclear membrane degradation) phenotypes.

A 10-fold leukocyte enrichment was achieved at the side outlets (Fig. 2A) and leukocyte differential count using flow cytometry analysis also showed ~50% decrease in neutrophil concentration in the eluent collected from anti-CD66b-coated side outlets, indicating efficient on-chip neutrophil capture (Fig. 2B). We next measured the fluorescence intensity along the side chamber using FITC dye preloaded in the reservoir proximal to the connecting side channels, and linescans at various time points showed that the diffusion gradient remained linear and stable for 2 hours (Fig. 3B). For chemotaxis assay we successfully demonstrated migration of captured healthy neutrophils towards the chamber preloaded with fMLP (200 nM) within 2 hours (Fig. 3C). For NETosis assay, glucose-treated neutrophils (30 mM) exhibited an increase in NETosis (P < 0.05) than untreated and mannitol-treated (30 mM) neutrophils (Fig. 4A, B).

The unique strategy of integrating microfluidic neutrophil sorting with cellular functional assays facilitates user operation and the developed diagnostic platform can be further advanced for point-of-care inflammatory profiling and precision medicine approaches. We envision that characterization of neutrophil chemotaxis in diabetes patients can provide direct evidence in microvascular compilations in diabetes and be used as surrogate biomarkers for monitoring endothelial dysfunction, arterial stiffness, peripheral markers of inflammation and oxidative stress in metabolic diseases.

Curved river has the unique geomorphological characteristics, and provides diverse habitats for instream and riparian living organisms as well. Human activities caused stress on river habitat which makes river restoration be necessary by taking effective methods. In order to solve the problem of how to restore the river morphology, Chishui River is selected as the research area and fish is selected as the biological indicator in this study. Geomorphological index of curved river is defined based on the river ecosystem integrity. Through field investigation and numerical simulation, quantitative method of the geomorphological index is researched. Then the geomorphological characteristics of certain rare and endemic fishes in Chishui River are confirmed according to their life habits. The response of fish habitat suitability to geomorphological characteristics alteration is researched by hydrodynamic model. The research of curved river habitat characteristics analysis and its ecological responses will provide direct theoretical supports for mitigation the ecological effects of hydraulic and hydroelectric engineering development in southwest area.

In this study, a microfluidic device with a light modulation system was developed to analyze microalgal photosythesis and respiration via real-time monitoring of oxygen production/consumption rates (OPR and OCR) based on based on phase-based phosphorescence lifetime detection within a microfluidic device. Besides, we also demonstrated our proposed device for water toxicity analysis and more particularly Diuron herbicide detection in water. The basic detection principle was based on monitoring disturbances in metabolic photosynthetic activities of algae induced by the presence of Diuron herbicide. Algal response, evaluated through variations in oxygen production rates (OPR) of algae, was different due to inhibition effect of the herbicide on photosynthesis in the presence of Diuron herbicide at 0.2–1 µM in the examined sample.

Organic halogens were closely watched in the marine for their persistence and ecotoxicological risk. The adsorbable organic halogens (AOX), as a sum indicator for the variety of organic halogens, was studied the concentration in seawater and sediment samples at 12 sites in the Hangzhou Bay (Fig.1). The results showed that the AOX concentrations in the sea water of Hangzhou Bay varied from 140.6±45.6 μg/L to 716.1±62.3 μg/L, much higher than the reported data in many other water bodies (Fig.2). However, the AOX concentration in the sediment of the Hangzhou Bay was relatively low, only 11.3±2.4 to 112.7±7.2 mg/kg, as probably resulted from the influence of the Yangtze River. Eleven WWTPs, the capacity of which covered 64.7% of the total capacity of all 141 WWTPs around the Hangzhou Bay, were with annually discharged amount of no more than 3.2% of the AOX concentration in the Hangzhou Bay. However, their impact was still inneglectible considering the accumulative and refractory nature of the AOX compounds.

The AOX in the Hangzhou Bay was predominantly artificial rather than nature produced. It was reported that naturally produced AOX significantly dependent on water quality indicators such as pH, Cl^- and TOC, while the above correlation could be broken when suffered the artificial wastewater. The Pearson correlation coefficients r in the seawater of the Hangzhou Bay were 0.190 (p=0.553), -0.423 (p=0.170), -0.222 (p=0.487) and -0.540 (p=0.07) between AOX and COD, pH, salinity and TOC, respectively, all insignificant at 5% level. In addition, the AOX /TOC ratio in the seawater of the Hangzhou Bay varied from 21.7 to 628.2 g/kg, one order of magnitude higher than those reported in literature.

This paper reports a new insight into the evolution of Effluent organic matters (EfOM) during ozonation and advanced oxidation process (AOPs), such as UV/H₂O₂ and UV/PS, revealed by fluorescence-PARAFAC. EfOM posed risks to receiving aquatic environments due to the complex compositions [1]. Based on previous reports, ozonation and advanced oxidation processes showed excellent performance during organic micropollutants removal and biotoxicity reduction. The principal reactions during ozonation and AOPs were shown in Table 1. However, it was lack of knowledge on evolution of EfOM during ozonation and AOP. Fluorescence coupled with PARAFAC was a useful tool to trace the EfOM [2]. So this study introduced a new insight into the EfOM transformation and oxidant kinetics during different oxidation processes.

Methods

All experiments were performed under batch test. DOC was determined using a TOC -VCPH analyser. UV absorbance was measured with a UV-VISIBLE Spectrophotometer. Fluorescence EEMs were created using a fluorescence Spectrophotometer. PARAFAC was modeled with DOMfluor Toolbox.

Results and Discussion

The water quality of secondary effluent was shown in Table 2. Four components were identified based on fluorescence-PARAFAC, including three humic-like substances (C1，C2 and C4) and a tryptophan-like substances (C3) (Fig. 1). C1, C2 and C4were related to the humic-like substances, and C3 was related to protein-like substances. These components were commonly found in secondary effluent [2]. The degradation of UV₂₅₄, DOC and PARAFAC components during all processes fitted well with pseudo-first-order kinetic. The degradation of PARAFAC components during ozonation was faster than that during AOP. With higher oxidants dosage, indicators removal rates and oxidants decline rates were both increased. This made a new insight into the use of oxidants during AOP.

Conclusion

Fluorescence components were more sensitive indicators than UV₂₅₄ and DOC in indicating the evolution of EfOM. Ozonation was an outstanding pretreatment process for AOP for its higher apparent reaction rate with fluorescence indicators. Moreover, efficiencies of ozonation and AOP could be observed by monitoring the change of fluorescence components, thus controlling the oxidants dosage dynamically.

Functional nucleic acid (FNA) is a hot biological recognition element for the construction of DNA biosensor. Typical FNA includes aptamer, DNAzyme and base pair mismatch oligonucleotides. Each type of FNA targets for different molecules, ranging from metal ions to macromolecules. Fluorescein labeled FNA strands and streptavidin molecules could be conjugated by heterobifunctional crosslinkers, forming triple functional DNA-protein conjugates as signal probes for environmental contaminants detection. An evanescent wave based optical sensing plartform is used to demonstrate this DNA-protein conjugate-mediated sensing concept. Using the platform, signal probes could be specifically captured onto desthiobiotin modified sensing surface, leading to fluorescence emissions induced by the evanescent field. The novel detection strategy enables facile detection of three typical environmental contaminants (ochratoxin A, Pb²⁺ and Hg²⁺) with high specificities and low detection limits at low nanomolar level. Moreover, the sensing surface is robust enough for more than 200 sensing cycles and can be stored at room temperature over one month. It is reasonable to believe the DNA-protein conjugate-mediated evanescent wave fluorescent biosensing method can be ported to other solid surfaces, such as the planar waveguide platform, using evanescent wave induced emission or other techniques like surface enhanced Raman scattering (SERS) and local surface plasmon resonance (LSPR).

In recent years there has been a rising interest in the environmental sector of natural sciences, as an increase in pollution in the environment has been observed. The industrial activity to sustain an ever-growing human population leads to the uncontrolled release of pollutants, e.g lead. As a result, rigorous limits have been set for the maximum allowed concentration for each pollutant in the environment. Since the content of pollutants occurring in natural ecosystems should be kept as low as possible, there is an ongoing search for analytical methods with ever-lower detection limits. For that, ion-selective electrodes (ISEs) are constantly investigated as they poses several desired properties for an environmental sensor. Namely, they are portable and relatively inexpensive and with maintenance limited to a minimum. The environmental analysis of ions requires the sensor to operate at low and ultra-low concentrations of analyte.  Thus, extending the sensitivity range of the ISEs by lowering the detection limit is required. In this presentation, the newest measurement protocols and application of ISEs for lowering the detection limit and measurements of ionic pollutants in natural waters will be discussed.

The measurement and control of humidity is imperative for environments including medical (e.g. diagnostic tools, operating theatres, rehabilitation wards), manufacturing (e.g. glasses, coatings, optical fibers), agricultural (e.g. greenhouses, crop fields), food (e.g. baking, drying, storage) and buildings (e.g. museums, heritage buildings).  Recent advances in humidity sensors that are both fast and sensitive are discussed. Optical sensors are inherently immune to electromagnetic interference. In-house fabricated planar optical sensor heads can reach a sensitivity of 310 nm/100%RH (e.g. 6×10^-3%RH detection limit). In-house developed fiber-optic sensor heads can achieve a response time of 3 ms, which is the fastest ever reported. A new type of touchless control based on humidity signals is also presented, which can compete against sound- and gesture-based technologies, with unique applications.

Individual phenotypic variations exist ubiquitously in biology. Much evidence shows scarce cells can determine the fate of a population. Identifying and studying such a small group of key individuals from naturally occurring environmental microorganisms remains a significant challenge, since the vast majority of them remain “dark matter”. Even for cultivable microorganisms in the laboratory, individual difference is often masked by conventional methods that use the average response from a population. In this context, our work has focused on integration of microfluidic platforms with advanced imaging and Raman spectroscopic technologies for single cell analysis and sorting. Our approaches enable quantitative and real time analysis of individual cells within a population, without the need for extrinsic and external labelling processes.

Here, I will illustrate these approaches with two recent examples: 1) An automated Raman activated single cell sorting system that allowed us to continuously sort individual cells directly from their native fluids (e.g. microbial communities from the ocean) based on their physiological activity. 2) A quantitative single-cell growth platform that reveals a diversity of individual growth behaviors in a population under well-controlled stress microenvironments. These platforms enabled us to reveal hidden key individuals and their roles in the survival and function of a population, and helped develop a better understanding of bacterial responses to environmental challenges. As such, they provide a powerful tool for microbiology research with many potential applications in environmental science, synthetic biology and drug discovery.