Page 47 - Handbook of Adhesion Promoters

40 Mechanisms of Adhesion

Figure 2.45. Illustration of the ion diffusion process through the semi-permeable membrane. Bacteria and printed
2+
3+
circuit boards particles were separated by the membrane, and only Fe ions (Fe and Fe ) and Cu ions could pass
through the membrane pores. [Adapted, by permission, from Silva, RA; Park, J; Lee, E; Park, J; Choi, SQ; Kim,
H, Separation Purification Technol., 143, 169-76, 2015.]
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purity. Other influences include an abutment, cement, and oral environment (saliva and
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proteins from blood and soft tissue).
Microbiological adhesion is not always unwelcome occurrence. Here is an example
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of utilization of copper extraction from discarded printed circuit boards. Figure 2.45
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explains idea of recovery of copper from the boards. Acidithiobacillus ferrooxidans was
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used as the bacterial attachment. Within the first hour of the experiment, 4.3x10 cells
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were attached per gram of printed circuit boards. The bacteria was capable of extracting
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1.46 g/l of copper.
Barnacles attach to a wide variety of surfaces underwater and show substrate-spe-
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cific adhesion mechanisms. The barnacle species Balanus crenatus has adhesive com-
posed of globular structures (the diameter of the smallest globules approximately 30
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nm). The barnacle adhesive contains approximately 90% proteins. Water uptake is
thought to be a mechanism that increases the volume of the adhesive whenever there are
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distances or gaps to be bridged. The adhesive is a porous material because of which it is
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more flexible, resistant to fracture, and it permits water circulation.
The biological systems, such as octopus, sea urchins, starfishes, etc. have energeti-
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cally advantageous attachment and detachment strategies. Figure 2.46 shows the results
of 3D reconstruction of histological and magnetic resonance images using the Amira soft-
ware to analyze octopus suckers used to accomplish adhesion for an extended period of
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time, with a negligible energetic effort.