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The protection of steel against marine biofouling is usually achieved by the application of protective coatings. In this work, an antifouling coating based on alginate biopolymer was developed using the electrophoretic deposition method. Zinc cations have been incorporated into the material to obtain some anti-algae / bacteria properties and calcium cations have been included to contribute to its jellification. The coatings produces were characterized by XRD, SEM, EDX and XPS techniques: the microscopic coatings fully and uniformly covered the steel samples. Results of the biological assays have demonstrated the impact of the coating on marine bacteria and microalgae; the values are comparable to those obtained in bioassays using copper-based alginate coatings. The antifouling effect of the coatings was equivalent to the potency of a high-volume hydrogel effect. These low-cost biocompatible coatings can be attractive in a wide variety of marine applications.

In this study, a sensor based on the development of a planar antenna immersed in sediments dedicated to water content monitoring in this type of material is proposed and experimentally validated. It is produced by a conventional Printed Circuit Board (PCB) manufacturing process on a double-sided metalized FR4 substrate. The sensitivity of the sensor is ensured by the variation of the real part of the complex dielectric permittivity of sediments with water content at around 1 GHz. As shown, in this frequency range, electrode polarization and Maxwell–Wagner polarization e ects become negligible, leading to only a bulk water polarization sensitivity. The sensor operates in the reflection mode by monitoring the variation of the resonant frequency as a function of the sediment density through the S11 reflection measurements. An experimental sensitivity of 820 MHz.g..1.cm3 was achieved. Despite the simplification of data interpretation at the considered frequency, the influence of ionic species such as NaCl in sediments on the real part of the relative complex dielectric permittivity is highlighted. This demonstrates the importance of considering a second parameter such as the S11 level at low frequency or the electrical conductivity to extract the density from the frequency measurements.

Microorganisms have the ability to settle on nearly all man-made surfaces in contact with seawater and subsequently to form biofilm. Biofilms control and removal is necessary in the sectors of maritime transport, energy... In this work, we present the development of new pure calcium, zinc or copper alginate, but also mixed Ca/Cu and Ca/Zn alginate hydrogels. These materials have been evaluated for their potential inhibition of adhesion of two key biofilm-forming microalgae Halamphora coffeaeformis and Cylindrotheca closterium). All the tested materials have presented high adhesion inhibition about 80%). Copper-base materials present a high toxicity against H. coffeaeformis. Pure zinc alginate is also toxic for this strain. However, the addition of calcium in zinc alginate leads to the toxicity reduction. The toxicity of these materials differs according to the strains. Consequently, mixed zinc/calcium alginate are efficient at inhibiting microalgal adhesion with a low level of cells toxicity. These alginate hydrogels are promising materials because they are efficient, cheap, easy to develop and eco-friendly.