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One example of a superhydrophobic surface in nature is the Lotus leaf. [12] Lotus leaves have a typical contact angle of θ ∼ 160 ∘ {\displaystyle \theta \sim 160^{\circ }} , ultra low water adhesion due to minimal contact areas, and a self cleaning property which is characterised by the Cassie-Baxter equation. [ 13 ]
An example of a UV treatment where UV radiation is the primary factor that effects the surface preparation is with the use of excimer lasers. Excimer lasers are extremely high energy and use to create pulses of radiation. When the laser makes contact with the surface of the adherend, it removes a layer of material, therefore cleaning the surface.
To incorporate the effect of adhesion in Hertzian contact, Johnson, Kendall, and Roberts [5] formulated the JKR theory of adhesive contact using a balance between the stored elastic energy and the loss in surface energy. The JKR model considers the effect of contact pressure and adhesion only inside the area of contact.
Differential adhesion hypothesis (DAH) is a hypothesis that explains cellular movement during morphogenesis with thermodynamic principles. In DAH tissues are treated as liquids consisting of mobile cells whose varying degrees of surface adhesion cause them to reorganize spontaneously to minimize their interfacial free energy. [1]
Likewise, contaminants, especially those which, due to their low surface tension, counteract wetting by the adhesive (for example, oils, release agents, etc.) hinder the adhesion interaction. Contaminants form, as it were, a barrier between the adhesive and the substrate which cannot be bridged by the adhesion forces due to their short reach.
A number of adhesion promotion methods have been developed to enhance PTFE bond strength. The primary methods currently used in industry are sodium etching and plasma etching. Results of ion beam treatment and laser surface roughening have also been reported in the literature, but do not have a significant presence as commercial processes.
STM image of a quinacridone adsorbate.The self-assembled supramolecular chains of the organic semiconductor are adsorbed on a graphite surface.. Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces.
The water drops maintain their spherical shape due to the superhydrophobicity of the petal (contact angle of about 152.4°), but do not roll off because the petal surface has a high adhesive force with water. [41] When comparing the "petal effect" to the "lotus effect", it is important to note some striking differences. The surface structure of ...