Surface Mechanical Properties of the Spore Adhesive of the Green Alga Ulva |
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Authors: | Gilbert C Walker Yujie Sun Senli Guo John A Finlay Maureen E Callow James A Callow |
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Affiliation: |
a Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
b Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
c School of Biosciences, University of Birmingham, Birmingham, UK |
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Abstract: | The mechanical properties of the adhesive produced by spores of the green, marine, fouling alga Ulva linza are reported. Atomic force microscopy studies were performed and nanoindentation data were analyzed using a model for an asymmetric indenter. Freshly secreted adhesive is characterized by multiple layers. We found that the modulus of the outer ∼600-nm thick layer was about 0.2 ± 0.1 MPa, whereas the modulus of the inner layer was about 3 ± 1 MPa. Older adhesive showed the formation of a “crust” of harder material with a yield strength of ∼20 MPa at a loading rate of 2.5 × 10-6 N · s-1. Mechanical properties under tension are also described, and extension profiles that showed either constant or nonlinear force changes with tip-sample separation were observed. Models for both kinds of behavior are described. The work of adhesion between poly-dimethylsiloxane (PDMS)-coated AFM tips and the adhesive was determined to be less than 1.5 mJ · m-2. |
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Keywords: | Ulva Marine alga Atomic force microscope PDMS Bioadhesive |
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