Surface characterization and wetting properties of coconut scale insects (Aspidiotus destructor signoret and aspidiotus rigidus Reyne)

• Main Author: Mariano, Meril Kate K.
• Format: text
• Language: English
• Published: Animo Repository 2019
• Subjects: Aspidiotus destructor; Coconut palm; Biomimetics; Contact angle; Biology
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/7158
• Institution: De La Salle University

Biological surface is one of the many inspirations for biomimetic designs. Biomimetics is a field of material science wherein solutions for problems are answered by mimicking nature. The coconut scale insects Aspidiotus destructor and Aspidiotus rigidus scale covers showed potential as it is capable of resisting wetting. In addition, their scale cover surface topology could be a potential key for identifications that may be unique for each species. These insects together with their substrate Cocos nucifera leaves were investigated for its surface wetting properties in relation to their surface characters using an optical contact angle meter and scanning electron microscopy (SEM), respectively. The obtained contact angle (CA) allowed for the calculation of the rate of wettability, drop asymmetry (DA) and surface free energy (SFE). The study showed that an outward stacked layer formed in a concentric pattern was present in A. destructor while that of A. rigidus is a less conspicuous concentric pattern formed by bumps and wax protrusions, Cocos nucifera in contrast is composed of fissured layer of wax and secondary veins in some portions of the leaves. Furthermore, the SEM revealed that A. rigidus has more and longer wax protrusions compared to A. destructor. In relation to the wetting properties, the CA of A. destructor (102.66+ O ) is less than that of A. rigidus (102.77+ O ) which suggests that the protrusions are positively correlated to the CA. Cocos nucifera, on the other hand showed a more wettable CA which ranges from 93O -71O . The relationship of the surface microstructures to the resulted CA were further supported by the calculated rate of wettability, DA and SFE. Using Principal component analysis, it showed that the wetting properties of A rigidus is completely different from that of A. destructor. This indicates that wetting properties could serve as an identifying character in addition to the surface characters.