Preventing freshwater mussel attachment at the adhesion interface

Kimmins, Kenneth (1), James, Bryan (2), Nguyen, Minh-Tam (2), Hatton, Benjamin (1, 2), Sone, Eli (1, 2, 3)

(1) Institute of Biomaterials and Biomedical Engineering, University of Toronto

(2) Department of Materials Science and Engineering, University of Toronto

(3) Faculty of Dentistry, University of Toronto

Freshwater mussels adhere underwater with remarkable strength. Weakening the interface between the mussel adhesive and the substrate (‘plaque-substrate interface’) is essential in developing targeted antifouling strategies, but current approaches do not take this into consideration. Oil-infused polydimethylsiloxane (iPDMS) has shown promise in preventing bacterial and marine fouling owing to its omniphobic surface oil layer, where free polymer chains of silicone oil are contained within a cross-linked silicone elastomer as a swollen polymer network, acting as a liquid physical barrier. To date, however, its effectiveness against freshwater mussel biofouling has not been evaluated.

iPDMS substrates with varying levels of oil saturation were fabricated, and then presented to mussels for reattachment in a simulated freshwater environment for 3 days. For each substrate, its saturation ratio (ratio representing the extent of saturation) and slide angle (critical angle where a water droplet completely rolls off the substrate without pinning) were measured. Following mussel reattachment, a mechanical tensile test was conducted to measure the detachment force of each mussel on sub-saturated and fully saturated iPDMS. The modes of adhesion failure were tracked in order to determine the effect of oil saturation levels on the plaque-substrate interface.

The frequency of mussel reattachment decreased with increased iPDMS saturation, displaying no reattachment at full saturation and near full saturation. There was an increased occurrence of complete adhesion failures as saturation levels increased. These results suggest that the surface oil layer acts to weaken the plaque-substrate interfacial adhesion. Characterization of iPDMS after the 3-day period showed significant changes in the slide angle of sub-saturated iPDMS but not for fully saturated iPDMS, despite no observed oil loss in either group. This may be due to the substrate being more prone to microfouling; with insufficient oil volume infused, the substrate surface may not have full oil coverage, providing areas where microfouling can take place. Further characterization of the surface oil layer distribution will be conducted to ascertain this. Employing iPDMS as an antifouling coating shows promise as a solution against freshwater mussel adhesion. This work also aids in understanding the antifouling mechanism of iPDMS and the role of the plaque-substrate interface in freshwater mussel adhesion.