Bacterial colonization of polymer-based coatings remains a major concern in marine and industrial environments, yet reported trends regarding the influence of surface properties on bacterial attachment remain difficult to compare across studies. In this work, we investigate the respective roles of surface energetics and mechanical properties in the early stages of bacterial colonization by explicitly distinguishing static adhesion from retention under mechanical solicitation. A series of hydrophobic polymer films with controlled chemistry, roughness, and thickness were prepared and characterized in terms of wettability, elastic modulus, and viscoelastic response. Static adhesion of Pseudomonas aeruginosa PAO1 was quantified under conditions preventing dewetting and air-liquid interface formation. Under these conditions, adhesion correlates with the critical surface tension of the substrates, highlighting the role of interfacial energetics in governing initial attachment on hydrophobic polymer surfaces. In contrast, bacterial retention under shear cannot be rationalized by surface energetics or elastic stiffness alone. Retention levels instead correlate with the viscoelastic loss factor tan δ, indicating that mechanical dissipation at the interface plays a dominant role in resistance to detachment. These results emphasize the importance of controlling experimental conditions and of clearly separating adhesion from retention when evaluating bacterial interactions with polymer coatings. They further suggest that viscoelastic dissipation constitutes a relevant descriptor for bacterial persistence under flow, beyond classical surface energy and stiffness considerations.

The use of flax (Linum usitatissimum L.) fibres for textile dates back to several millennia; in Ancient Egypt flax was widely used in many everyday items. While flax fibres continue to diversify today as composite reinforcements, the study of their historical use is highly relevant when it comes to their durability; archaeological samples offer unique lenses for understanding changes in intrinsic fibre properties after long-time periods. Through a comprehensive examination of ancient Egyptian flax fibres from four archaeological artefacts, this study carries out a detailed characterisation of the fibre ultrastructure and micromechanical properties by combining nanoindentation (NI) and atomic force microscopy (AFM). This work highlights the complementary of these techniques for both heritage and materials science; it demonstrates on some samples, the remarkable cell wall stiffness, even after thousands of years, which is a key element for the bio-based composites sector, to better understand the degradation mechanisms of plant fibres.

Understanding how substrate mechanics influence bacterial adhesion and retention is essential for controlling biofilm formation on synthetic materials. Studies on soft polymers such as PDMS are often confounded by uncontrolled variations in surface chemistry and topography. In this work, a PS-PIB bilayer system was designed to decouple surface chemistry from mechanics, enabling independent control of stiffness while maintaining constant surface properties. Static adhesion assays with Pseudomonas aeruginosa PAO1 showed that initial attachment was insensitive to substrate modulus when surface chemistry and roughness were held constant. In contrast, retention under shear flow decreased with increasing stiffness and correlated more closely with the work of separation obtained from nanoindentation experiments. This parameter, which integrates both adhesive and dissipative contributions, is introduced as an empirical descriptor of interfacial mechanical resistance. Retention data were described by a power-law model consistent with stochastic frameworks of multivalent adhesion, reflecting population heterogeneity in the number and strength of adhesive contacts. Altogether, these findings suggest that viscoelastic dissipation is a key factor influencing P. aeruginosa PAO1 detachment under flow and highlight the need for future studies using bacterial mutants and diverse species to assess the generality of this correlation across different adhesion strategies.

The aim of this work is to investigate the effect of ultra-soft hydrogel coatings on bacterial adhesion. To achieve this, chitosan hydrogel coatings were prepared and characterized in terms of physicochemical surface properties (roughness, hydrophobicity), mechanical characteristics (elastic modulus, crosslink density), as well as their hydration and swelling capacities. Physicochemical properties, such as roughness and hydrophobicity, were confirmed to remain consistent. Two model marine bacterial strains, a non-motile Gram-positive Bacillus sp. 4J6 and a motile Gram-negative Vibrio harveyi, were selected for this study. The assessment of their adhesion on the coatings was performed under flow and analyzed by confocal laser scanning microscopy. The results suggest that bacterial adhesion decreases as the amount of cross-linking agent (citric acid) is reduced, while changes in hydration, swelling rates and stiffness (elastic modulus) - all influenced by the degree of cross-linking - were less pronounced. Notably, the variations in elastic modulus (from 1.98 to 2.29 KPa), hydration (from 76 % to 62 %) and swelling rate (from 125 % to 65 %) after immersion in deionized water were remarkably minimal. This study highlights the complexity of understanding the mechanisms of bacterial adhesion to hydrogel coatings, challenges widely accepted views on the impact of stiffness on bacterial adhesion, and emphasizes the need to

Silicone elastomer coatings have shown successful fouling release ability in recent years. To further enhance the design of silicone coatings, it is necessary to fully understand the mechanisms that contribute to their performance. The objective of this study was to examine the relationship between the molecular weight of polydimethylsiloxane (PDMS) and antibioadhesion efficiency. PDMS-based coatings were prepared via a condensation reaction, with a controlled molecular weight ranging from 0.8 to 10 kg·mol−1. To evaluate changes in surface wettability and morphology, contact angle experiments and atomic force microscopy (AFM) were performed. Finally, the antibioadhesion and self-cleaning performance of PDMS coatings was carried out during in situ immersion in Lorient harbor for 12 months. Despite small variations in surface properties depending on the molecular weight, strong differences in the antibioadhesion performance were observed. According to the results, the best antibioadhesion efficiency was obtained for coatings with an Mn between 2 and 4 kg·mol−1 after 12 months. This paper provides for the first time the impact of the molecular weight of PDMS on antibioadhesion efficiency in a real marine environment.

Silicone materials are widely used in fouling release coatings, but developing eco-friendly protection via biosourced coatings, such as polyhydroxyalcanoates (PHA) presents a major challenge. Anti-bioadhesion properties of medium chain length PHA and short chain length PHA films are studied and compared with a reference Polydimethylsiloxane coating. The results highlight the best capability of the soft and low-roughness PHA-mcl films to resist bacteria or diatoms adsorption as compared to neat PDMS and PHBHV coatings. These parameters are insufficient to explain all the results and other properties related to PHA crystallinity are discussed. Moreover, the addition of a low amount of PEG copolymers within the coatings, to create amphiphilic coatings, boosts their anti-adhesive properties. This work reveals the importance of the physical or chemical ambiguity of surfaces in their anti-adhesive effectiveness and highlights the potential of PHA-mcl film to resist the primary adhesion of microorganisms.

Biofilms, responsible for many serious drawbacks in the medical and marine environment, can grow on abiotic and biotic surfaces. Commercial anti-biofilm solutions, based on the use of biocides, are available but their use increases the risk of antibiotic resistance and environmental pollution in marine industries. There is an urgent need to work on the development of ecofriendly solutions, formulated without biocidal agents, that rely on the anti-adhesive physico-chemical properties of their materials. In this context, exopolysaccharides (EPSs) are natural biopolymers with complex properties than may be used as anti-adhesive agents. This study is focused on the effect of the EPS MO245, a hyaluronic acid-like polysaccharide, on the growth, adhesion, biofilm maturation, and dispersion of two pathogenic model strains, Pseudomonas aeruginosa sp. PaO1 and Vibrio harveyi DSM19623. Our results demonstrated that MO245 may limit biofilm formation, with a biofilm inhibition between 20 and 50%, without any biocidal activity. Since EPSs have no significant impact on the bacterial motility and quorum sensing factors, our results indicate that physico-chemical interactions between the bacteria and the surfaces are modified due to the presence of an adsorbed EPS layer acting as a non-adsorbing layer.

The development of biofouling is a major problem for marine industries. The conception of antifouling and fouling release coatings, with controlled physical-chemical properties is a promising strategy. Among them, amphiphilic systems, such as those composed of a hydrophobic polydimethylsiloxane matrix and a hydrophilic polyethyleneglycol additive are the most efficient and up to date. Despite their effectiveness, these systems are questioned due to the petrochemical origin of PDMS. The aim of this project was to substitute the PDMS matrix with a biopolymer, poly(3-hydroxybuyrate-co-3-hydroxyvalerate) and to improve its anti-adhesion properties through the elaboration of an amphiphilic system, via the addition of PEG or PHBHHx-b-PEG copolymer. The results, including the physico-chemical properties of PHBHV based coatings and static adhesion tests on a marine bacterium, Bacillus 4J6 and a diatom, Phaeodactylum tricornutum are compared with those of PDMS and PEG-modified PDMS coatings. Real antiadhesion activity was obtained for the PHBHV/PHBHHx-b-PEG system for a promising eco-friendly strategy.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) were used to prepare microbeads, with diameter ranging from 50 to 100 µm, by an emulsion-evaporation process. The emulsification-evaporation process enables the formation of spherical polyhydroxyalcanoate beads, with crystalline rates similar to the ones of the former polymer and with important surface roughness as compared to amorphous polylactic acid smooth beads. The mechanical properties of the different PHA beads are also found to be intimately linked with their crystalline content, with modulus varying between 1 and 7 GPa. The degradation behavior of these PHA microbeads was tested under marine environment and revealed a rapid degradation, similar to cellulose, and a degradation rate correlated with the crystalline content. These results emphasize the possibility and interest in developing PHA materials with tunable functions and degradation properties.

PLA-flax non-woven composites are promising materials, coupling high performance and possible degradation at their end of life. To explore their ageing mechanisms during garden composting, microstructural investigations were carried out through scanning electron microscopy (SEM) and atomic force microscopy (AFM). We observe that flax fibres preferentially degrade ‘inwards’ from the edge to the core of the composite. In addition, progressive erosion of the cell walls occurs within the fibres themselves, ‘outwards’ from the central lumen to the periphery primary wall. This preferential degradation is reflected in the decrease in indentation modulus from around 23 GPa for fibres located in the preserved core of the composite to 3–4 GPa for the remaining outer-most cell wall crowns located at the edge of the sample that is in contact with the compost. Ageing of the PLA matrix is less drastic with a relatively stable indentation modulus. Nevertheless, a change in the PLA morphology, a significant decrease in its roughness and increase of porosity, can be observed towards the edge of the sample, in comparison to the core. This work highlights the important role of intrinsic fibre porosity, called lumen, which is suspected to be a major variable of the compost ageing process, providing pathways of entry for moisture and microorganisms that are involved in cell wall degradation.

The present work is focused on better understanding of the interfacial interactions of SBA-15 mesoporous silica particles with flax fibers.In order to overcome the inherent complexity of flax fiber surface composition we have prepared model polysaccharide surfaces representing the main component of the flax fibers, e.g.cellulose, polygalacturonic acid (PGUA), and xyloglucan (XG) with thicknesses of about 200 nm, 100 nm, and 110 nm, respectively.The ξ-potential measurements of both silica and polysaccharides were performed in aqueous solutions as a function of pH and ionic strength.ξ-potential, AFM and SEM results supported the important role of electrostatic interactions in the silica adsorption on polysaccharide surfaces, since silica adsorption increased remarkably with ionic strength.The adsorption density of the SBA-15 onto the various polysaccharides was Cellulose > PGUA > XG, and the maximum was observed at pH = 4. Urea used as hydrogen bonds breaker reduced significantly the adsorption of SBA-15 on the polysaccharide surfaces, which highlighted the significant contribution of hydrogen bonding in the adsorption process.It was observed that most adsorbed SBA-15 particles were resistant to ultrasonic washing, which revealed their strong irreversible adsorption.Finally, direct adsorption experiments on both raw and treated real flax fibers yielded results consistent with those of model surfaces showing the important role of the surface fibers treatments on the improvement of the interfacial adhesion of the silica particles with flax fibers.The remarkable affinity of the SBA-15 particles with treated flax fibers is encouraging to design superinsulators composites with tuneable mechanical performances.

After years of inadequate use and the emergence of multidrug resistant (MDR) strains, the efficiency of "classical" antibiotics has decreased significantly. New drugs to fight MDR strains are urgently needed. Bacteria hold much promise as a source of unusual bioactive metabolites. However, the potential of marine bacteria, except for Actinomycetes and Cyanobacteria, has been largely underexplored. In the past two decades, the structures of several antimicrobial compounds have been elucidated in marine Proteobacteria. Of these compounds, polyketides (PKs), synthesised by condensation of malonyl-coenzyme A and/or acetyl-coenzyme A, and non-ribosomal peptides (NRPs), obtained through the linkage of (unusual) amino acids, have recently generated particular interest. NRPs are good examples of naturally modified peptides. Here, we review and compile the data on the antimicrobial peptides isolated from marine Proteobacteria, especially NRPs.

Le but ici est de fabriquer des elements optiques diffractifs (EODs) performants, selon un procede simple a mettre en œuvre et pour un cout raisonnable, sachant qu’un EOD est un dispositif capable de modifier par diffraction la distribution spatiale d’un faisceau lumineux. La lumiere diffractee par l’element forme plusieurs fronts d’ondes qui interferent et se recombinent pour donner naissance a la repartition lumineuse souhaitee, dans le plan de reconstruction. Ces composants optiques doivent en particulier repondre aux besoins actuels des industriels qui pourraient les utiliser. Dans notre cas, les EODs agissent sur la phase de l’onde. Pour cela, les differences de marche optique d’un point a un autre correspondent a des variations locales d’epaisseur generees dans le materiau support. Les motifs constituant ce relief sont calcules a partir des caracteristiques de l’onde incidente et de la figure de diffraction souhaitee a la sortie de l’EOD. A Telecom Bretagne, le materiau le plus utilise dans ce domaine est une photoresine (PR), peu couteuse et simple a mettre en œuvre par photolithographie. La fabrication de l’EOD en PR est effectuee par ecriture directe grâce au phototraceur fonctionnant a 436 nm (longueur d’onde en accord avec le domaine d’absorption de la PR) et utilisant comme masque un micro-ecran a cristaux liquides, qui a l’avantage d’etre reconfigurable selon le motif a creer. Le motif a reproduire est image dans la couche photosensible grâce a une optique de reduction. Apres developpement, l’element subit des post-traitements afin d’acquerir ses proprietes optimales. Cependant, ces EODs en photoresine ne donnant pas toujours entiere satisfaction face aux nouvelles demandes, l’etude s’est tournee vers la fabrication d’EODs avec un materiau sol-gel hybride (SGH) commercialement disponible, l’Ormocomp de la famille des ORMOCER®s. Son interet par rapport a la PR reside dans le fait que c’est un materiau hybride ou sont simultanement presentes des composantes inorganiques et des composantes organiques (proprietes mecaniques du materiau proches de celles du verre tout en ayant la possibilite de micro- ou nano-structuration par voie photochimique). Cette formulation absorbe jusque vers 400 nm et autorise l’utilisation de la raie a 365 nm des lampes a vapeur de mercure, mais pas de celle du phototraceur fonctionnant a 436 nm. Afin d’y remedier, la nouvelle generation d’EODs est creee par moulage dans le sol-gel hybride du relief initialement cree dans la photoresine. L’objectif etant alors de generer dans le SGH un relief inverse et semblable a celui de la PR, la caracterisation des reliefs correspondant aux EODs a initialement ete effectuee a l’aide d’un microscope interferometrique. Les deux types de relief etant en concordance et presentant les memes hauteurs (de l’ordre de 500 nm), le procede de transfert a principalement ete valide par l’analyse des proprietes optiques correspondant aux differentes microstructures. Mais afin d’essayer d’aller plus loin, une etude complementaire, situee en amont de tout ce qui etait precedemment realise, a ete mise en place. Elle repose sur la caracterisation par microscopie a force atomique aux echelles submicroniques des reliefs induits dans les deux types de polymere. C’est alors par comparaison des caracteristiques des structures creees dans la photoresine avec celles des elements obtenus par moulage dans le sol-gel hybride qu’il est possible d’acceder a de nouvelles informations devant permettre d’optimiser le procede propose, donc d’ameliorer les performances des composants optiques consideres. De par ses meilleures proprietes optiques, mecaniques, thermiques et chimiques comparees a celles de la photoresine, le materiau sol-gel hybride ici propose apparait aujourd’hui comme un materiau de choix dans le contexte actuel de miniaturisation croissante des systemes optiques. En particulier, il permet d’acceder a une gamme de micro-optiques diffractives repondant a de nouveaux besoins industriels. De plus, la technique de recopie proposee ouvre la voie a la fabrication de petites series reproductibles d’EODs en sol-gel hybride, sur mesure, a partir d’un unique moule SGH.

This paper describes an analysis of the parameters that influence the adherence properties between flax fibres and PLLA. Microdroplet debonding tests have been used, together with Atomic Force and Scanning Electron Microscopy. The apparent interfacial shear strength of flax/PLLA is significantly higher than that of glass/PP and similar to that of glass/unsaturated polyester. Comparison of results for glass fibres and flax with and without release agent indicate a large contribution of thermal residual stresses to interface properties. The multi-layer nature of vegetal fibres affects debonding mechanisms and partial peeling of the fibre is noted. The cohesion of the fibre cell-wall must therefore also be considered.A water treatment of flax fibres (72h at 23°C) is shown to result in a small drop in tensile properties but a significant increase in interfacial shear strength and friction stress. Drying for 14h at 105°C reduces fibre Young's modulus and failure strength and also reduces fibre/matrix adhesion by 20%. More extensive fibre peeling is observed after drying, indicating that drying affects fibre wall cohesion.

Natural fiber-reinforced polymers or biocomposites are becoming increasingly popular as an environment friendly alternative to traditional glass fiber-reinforced thermoplastics. The mechanical properties of reinforced biocomposites, such as flax/polylactic acid (PLA), are largely governed by the level of interfacial interactions between the two constituents apart from their intrinsic properties. The hierarchical organization of various polysaccharides present in natural fibers results in complex mechanisms at the interface which are still poorly understood and difficult to analyze through a traditional approach that rely on indirect assessments. The possibility of measuring direct adhesion force between individual particles using the colloidal force microscopy has been exploited here by developing an experimental set-up in which a micrometer colloidal PLA bead is brought into close contact with molecularly smooth polysaccharide surfaces that mimic the main constituents of flax fibers, cellulose, hemicellulose, and pectins. Adhesion force measurements performed under ambient and low relative humidity conditions indicate that cellulose/PLA is the weakest interface in the biocomposite. Moreover, the results emphasize the important role of water molecules for the more hydrophilic polymers in flax fibers that takes place in the fundamental forces involved in the adhesion phenomena at the biocomposite interface.

The effect of alkali and enzymatic treatments on flax fibre morphology, mechanical, and adhesion properties was investigated. The multilength scale analysis allows for the correlation of the fibre's morphological changes induced by the treatments with mechanical properties to better explain the adherence properties between flax and PLA. The atomic force microscopy (AFM) images revealed the removal of primary layers, upon treatments, down to cellulose microfibrils present in the secondary layers. The variation in mechanical properties was found to be dependent, apart from the crystalline content, on interaction between cellulose microfibrils and encrusting polysaccharides, pectins and hemicelluloses, in the secondary layers. Finally, microbond tests between the modified fibres and PLA emphasize the important role of the outer fibre's surface on the overall composite properties. It was observed here that gentle treatments of the fibres, down to the oriented microfibrils, are favourable to a better adherence with a PLA drop. This paper highlights the important role of amorphous polymers, hemicellulose and pectin, in the optimisation of the adhesion and mechanical properties of flax fibres in the biocomposite.

The overall mechanical properties of natural fibre reinforced biocomposites are largely governed by the intrinsic strength of reinforcement fibres as well as by the level of adhesion between the fibres and the matrix polymer. The research work reported in this manuscript presents a model investigation of the adhesion properties of the major polysaccharides in flax and a polylactic acid polymer matrix, and a correlation between these interactions and the final mechanical properties of the fibre and the composite. The main objective of this multi-length scale analysis is to better understand the complex role of the different polysaccharides present in flax fibres at the biocomposite interface. We first submit a raw flax fibre to two separate treatments, an enzymatic and an alkali one, which are known to indirectly promote the adherence between the reinforcement fibre and a PLA matrix. The detailed investigation of the morphology, mechanical and adherence properties of the treated fibres allows to observe the removal of the middle and primary layers down to the cellulose microfibrils networks of the secondary layers, and underlines the importance of limiting the attack of encrusting amorphous hemicellulose matrix within the secondary layer that is essential both in order to maintain interesting material properties and to promote adhesion with PLA. In a second time, we adapt the colloidal force microscopy to directly probe interaction forces between PLA and the different polymers in flax fibre. The system was first tested on cellulose and PLA to estimate the Hamaker constant and the work of adhesion. From the Nardin and Schultz equation, the experimental data obtained by local techniques such as AFM were found to be more realistic, in contrast, with those obtained from averaging techniques that are known to be not suited for heterogeneous samples such as flax fibres. The colloidal force microscopy was thus used to selectively measure all the possible. Interaction between the different polysaccharides of the fibres and the PLA matrix to qualitatively identity the weakest interaction system in a biocomposite. The results underline the important interactions of PLA matrix with both hemicellulose and pectin materials, even at low humidity rate. We postulated that the high water content of these two polysaccharides may be responsible for several mechanisms of interaction with PLA, such as hydrogen bonds, capillary forces or inter-diffusion processes. In parallel, adhesion force mapping of real raw and treated flax fibre’s surface by AFM force-volume technique give complementary results that underline an important adhesion with these two polysaccharides