A model material simulating the mechanical and surface properties of a real human skin was developed for use as a substrate in adhesion-to-skin evaluation. It is a protein-lipid composition possessing film-forming ability. The composition is based on gelatin plasticized by glycerol, polysaccharides and a mixture of lipids that mimick the skin's lipid structure and creates a hydrophobic surface. To enhance the material hydrolytic stability, the composition was cross-linked by formaldehyde, producing a water-swellable but insoluble matrix. The surface topography of a real skin was achieved by a silicone replica technique. Thin films with thickness of 100 ± 10 µm were cast. The effect of the components ratio and preparation technique on the film mechanical, surface and hydrolytic properties was studied. Based on the results obtained, a formulation having mechanical and surface properties comparable to that of a human skin was selected. The relevance of the model material was evaluated in lap-shear and 180 • -peel adhesion tests and the results were compared to a finger or a forearm skin of ten healthy volunteers (in vivo tests). For validation purposes, commercial surgical tapes Micropore™ and Transpore™ and Mylar ® polyester film were also used. The effects of substrate, adhesive, conditions of the joint preparation and the test employed on adhesion strength were studied. The results obtained show that the mechanical and surface properties of the model material are close to those of the human skin.

ResearchCite this article: Dimartino S, Mather AV, Alestra T, Nawada S, Haber M. 2015 Experimental and computational analysis of a novel flow channel to assess the adhesion strength of sessile marine organisms. Bioadhesives produced by marine macroalgae represent a potential source of inspiration for the development of water-resistant adhesives. Assessing their adhesion strength, however, remains difficult owing to low volumes of adhesive material produced, low solubility and rapid curing time. These difficulties can be circumvented by testing the adhesion strength of macroalgae propagules attached to a substrate. In this paper, we present a simple, novel flow channel used to test the adhesion strength of the germlings of the fucalean alga Hormosira banksii to four substrates of biomedical relevance (PMMA, agar, gelatin and gelatin þ lipid). The adhesion strength of H. banksii germlings was found to increase in a time-dependent manner, with minimal adhesion success after a settlement period of 6 h and maximum adhesion strength achieved 24 h after initial settlement. Adhesion success increased most dramatically between 6 and 12 h settlement time, while no additional increase in adhesion strength was recorded for settlement times over 24 h. No significant difference in adhesion strength to the various substrates was observed. Computational fluid dynamics (CFD) was used to estimate the influence of fluid velocity and germling density on drag force acting on the settled organisms. CFD modelling showed that, on average, the drag force decreased with increasing germling number, suggesting that germlings would benefit from gregarious settlement behaviour. Collectively, our results contribute to a better understanding of the mechanisms allowing benthic marine organisms to thrive in hydrodynamically stressful environments and provide useful insights for further investigations.