We introduce for the first time a new product line able to make high accuracy measurements of a number of water chemistry parameters in situ: i.e., submerged in the environment including in the deep sea (to 6,000 m). This product is based on the developments of in situ lab on chip technology at the National Oceanography Centre (NOC), and the University of Southampton and is produced under license by Clearwater Sensors Ltd., a start-up and industrial partner in bringing this technology to global availability and further developing its potential. The technology has already been deployed by the NOC, and with their partners worldwide over 200 times including to depths of ∼4,800 m, in turbid estuaries and rivers, and for up to a year in seasonally ice-covered regions of the arctic. The technology is capable of making accurate determinations of chemical and biological parameters that require reagents and which produce an electrical, absorbance, fluorescence, or luminescence signal. As such it is suitable for a wide range of environmental measurements. Whilst further parameters are in development across this partnership, Nitrate, Nitrite, Phosphate, Silicate, Iron, and pH sensors are currently available commercially. Theses sensors use microfluidics and optics combined in an optofluidic chip with electromechanical valves and pumps mounted upon it to mix water samples with reagents and measure the optical response. An overview of the sensors and the underlying components and technologies is given together with examples of deployments and integrations with observing platforms such as gliders, autonomous underwater vehicles and moorings.
Molecular diffusive membranes play crucial roles in the field of microfluidics for biological applications e.g., 3D cell culture and biosensors. Hydrogels provide a range of benefits such as free diffusion of small molecules, cost-effectiveness, and the ability to be produced in bulk. Among various hydrogels, Pluronic F127 can be used for cell culture purposes due to its biocompatibility and flexible characteristics regarding its environment. Aqueous solutions of Pluronic F127 shows a reversible thermo-thickening property, which can be manipulated by introduction of ions. As a result, controlled diffusion of ions into the solution of Pluronic F127 can result in a controlled gel formation. In this study, the flow of immiscible solutions of Pluronic and sodium phosphate inside a Y-shaped microchannel is simulated using the level set method, and the effects of volume flow rates and temperature on the gel formation are investigated. It is indicated that the gel wall thickness can decrease by either increasing the Pluronic volume flow rate or increasing both volume flow rates while increasing the saline volume flow rate enhances the gel wall thickness. Below a critical temperature value, no gel wall is formed, and above that, a gel wall is constructed, with a thickness that increases with temperature. This setup can be used for drug screening, where gel wall provides an environment for drug-cell interactions.Article Highlights Parallel flow of Pluronic F127 and saline solutions inside a Y-shaped microchannel results in formation of a gel wall at their interface. The numerical analysis reveals the impact of each inlet flow rate and temperature on gel wall thickness and movement. The findings indicate that the gel wall has a low but steady velocity toward the saline solution. Graphical abstract
Interactions between temperature and toxicity of heavy metals to algae have so far received only little attention. Though, knowledge on such interactions seems indispensable to understand the ecological effects of simultaneous thermal and heavy metal pollution of surface waters.At our laboratory, the effects of mercury(II) on growth of the green alga Scenedesmus acutus in relation to temperature has been studied in batch cultures (Huisman et al., 1980). At 15 ~ mercury(II) appeared to inhibit growth at concentrations as low as 0.05 rag 1-1; complete inhibition was not observed in the range of concentrations tested. At 20 ~ almost complete inhibition of growth was found at the highest concentration tested (0.9 mg-1-1). At 25 ~ complete inhibition was already attained at a mercury(II) concentration of 0.5 mg. 1-1, whereas at 30~ growth was even completely inhibited at a mercury(II) concentration of 0.1 mg-1 -1 In experiments to be described here, the effect of cadmium on algal growth has been studied, again in relation to temperature. To this end, an axenic culture of S. acutus was grown in a Cdcontaining mineral medium, buffered at pH 7.5, which, in addition, contained the metal buffer methyl iminodiaeetic acid (MIMDA) in a series of concentrations such as to obtain a range of free Cd-concentrations between 0 and 0.11 mg. I-1. The cultures were aerated with air enriched with 1% CO2 and incubated on a Gallenkamp orbital shaker (100 rpm) under continuous light. Experiments were performed at three temperatures: 15 ~ 20 ~ and 30 ~ Biomass concentrations were determined by measuring light absorbance at 750 nm, which has previously been shown to give a reliable estimate of algal growth (Vollenweider, 1969).Examples of growth curves obtained at 15 ~ are presented in Fig.
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