Using lithography-based microfluidic technology, we produce monodisperse single-core microcapsules with UV-cured TPGDA (triprophylene glycol diacrylate) shells. We show that the geometrical and mechanical characteristics of the microcapsules can be predicted on a quantitative basis and tuned by varying the flow conditions. Shell thicknesses are varied by changing the flow rates of the inner or intermediate phases, according to mass conservation constraint. Off-centering of the core with respect to the shell is controlled by varying the shell phase viscosity. The mechanical properties of the capsules can be varied by changing the flow conditions and are quantitatively predicted by a numerical simulation. The simulation moreover provides a correct qualitative description of their rupture. As a whole, the work carried out in the present paper shows, on a quantitative basis, that microfluidic technology allows to finely control the geometrical and mechanical properties of microcapsules generated on chip. The level of control we reach here is not accessible, by far, to conventional technologies. Combined with parallelization, the present work opens routes toward the production of novel families of monodisperse microcapsules with tunable properties.

This work describes a design strategy to scale up microfluidics for producing monodispersed emulsions. Scale-up to 180 microfluidic devices with tight distribution of droplet size has been achieved (coefficient of variation CV ∼ 5%) by designing a system that is capable of operating easily without active control on single devices within the microfluidic platform. This has been achieved by using existing knowledge gained in the formation of monodispersed emulsions using a single device. We have identified three important factors affecting the scale-up of microfluidic systems that can benefit industrial scale-up processing. First, we used a network model simulation (Matlab) to evaluate two different branching layouts used to distribute liquids from a single manifold into the parallelized device network. We checked how fabrication tolerances could affect droplet formation, and as a result of this step, the ladder-type layout was preferred to the tree-type arrangement. The second important contribution of this work is the introduction of separate drainage manifolds for the two phases connecting all the input streams which have improved the performance and the operability of the system. Finally, we introduced a large opening after a short channel (150 μm) downstream of the junction where the droplet is formed. This opening acts like a reservoir to damp any pressure variation which could travel back to the inlet point and disturb the flow of neighboring devices.

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This paper describes a technique to perform traceable temperature measurements of the seawater column and seawater surface, based on optical fiber Bragg gratings. The paper explains the different phases of the work done: design of the optical fibers, its optical and thermal calibration and onsite measurements of the seawater temperature. In the design of these thermometers, special attention was paid to the involved materials in order to prevent any damage due to the exposure to such rugged environment. The fibers were subjected to optical and thermal calibration, with the aim to get traceable measurements and reliable uncertainty calculation of the seawater temperature. The fibers were deployed in the Mediterranean sea and water temperatures were continuously monitored and compared with the most common used thermometer in these environment, CTD, located in the submarine observatory OBSEA. This paper is part of a Special Issue entitled VSI: 2017 IMEKO TC 19. Research Highlights  A technique, based on fiber Bragg gratings (FBG), to measure traceable seawater temperature was developed  Design, characterization together with the optical and thermal calibration of the FBG was performed  Onsite seawater temperature measurements and its continuous monitoring by using FBG were performed in the Mediterranean submarine observatory OBSEA Abbreviations CTD, device to measure conductivity, temperature of the seawater and depth; FBG, Fiber Bragg Grating; OBSEA, underwater observatory (www.obsea.es); Pt-100, platinum resistance thermometer with a value of 100 Ω at the triple point of water; Pt-25, platinum resistance thermometer with a value of 25 Ω at the triple point of water

In this paper we propose and demonstrate two alternative methods for the high-precision calibration of fiber Bragg grating (FBG) interrogators. The first method is based on the direct comparison between the wavelength measurements of the interrogator under test and a calibrated wavemeter, while analyzing a simulated symmetric Bragg grating constructed by a tunable filter and a fiber mirror. This first method is applicable to most commercial systems but presents an uncertainty limited by the spectral width and the wavelength stability of the tunable filter. The second method consists in measuring multiple reference absorption lines of calibrated absorption gas cells. This second method presents lower uncertainties, limited only by the optical resolution of the interrogator and the wavelength uncertainty of the reference cell absorption lines. However, it imposes more restrictive requirements on the interrogator software. Both methods were experimentally demonstrated by calibrating multiple commercial systems, reaching uncertainties down to 0.63 pm at a central wavelength of 1550 nm.