Synchronous measurement of tribocharge and force at the footpads of freely moving animals
Hypothesis on electrostatic attraction mechanisms involving the hairy adhesion of climbing animals has been a matter of controversy for several years. The detection of tribocharge and forces at attachment organs of animals is a practical method of clarifying the dispute with respect to electrostatic attraction in the attachment of animals. Nonetheless, the tribo-electrification is rarely examined in the contact-adhesion of animals (especially in their free and autonomous attachment) due to the lack of available devices. Therefore, the present study involves establishing a method and an apparatus that enables synchronous detection of tribocharge and contact forces to study tribo-electrification in the free locomotion of geckos. A type of a combined sensor unit that consists of a three-dimensional force transducer and a capacitor-based charge probe is used to measure contact forces and tribocharge with a magnitude corresponding to several nano-Coulombs at a footpad of geckos when they climb vertically upward on an acrylic oligomer substrate. The experimental results indicate that tribocharge at the footpads of geckos is related to contact forces and contact areas. The measured charge allows the expectation of an exact attraction with magnitude corresponding to dozens of newtons per square meter and provides a probability of examining tribo-electrification in animal attachment from a macro level.
Keywordstribocharge forces synchronous measurement animal free locomotion
The authors extend their sincere appreciation to Wenbo Wang for raising geckos and aiding in performing the 3D microscopy and to the reviewers for their constructive advices. This study was supported by grants from the National Natural Science Foundation of China (Grants No. 51435008) and funding from the Jiangsu Innovation Program for Graduate Education (Grants No. KYLX16_0328). All applicable institutional and/or national guidelines for the care and use of animals were followed in the study.
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