Meeting Abstract
Geckos use millions of hair-like protrusions on their toe pads (setae) to utilize weak intermolecular van der Waal bond forces and achieve strong adhesion to a variety of substrates. These substrates vary in quality (i.e., moisture, roughness, temperature), namely in the tropics where conditions can be extreme. Tokay geckos (Gekko gecko) are native to the tropics, which endure high temperature and humidity. Interestingly, adhesive performance of Tokay geckos is inversely proportional to temperature and directly proportional to humidity (i.e., adhesion increases as humidity increases, but only at low temperature). In humidity the setae, composed of heterogeneous alpha and beta keratinous proteins and associated lipids, soften and become more adhesive. This behavior does not account for temperature and its interaction with humidity. Current literature fails to characterize the isolated effects of temperature and humidity on gecko adhesion, nor does it isolate an important sub-parameter: surface temperature. Geckos are ectotherms, so their body temperature is dictated by ambient temperature. In previous experiments only ambient temperature was varied, potentially complicating adhesion results. The experiments neglect the superheated substrates geckos naturally encounter. To investigate the effect of surface temperature on gecko adhesion we heated glass substrate to a range of temperatures (23 – 55°C) reported as the surface temperature of exposed canopy branches. We predicted that adhesive performance does not vary as a function of surface temperature, supporting the importance of relative humidity in gecko adhesion. The results of our study will help us better understand the adhesive mechanisms responsible for temperature and humidity dependent adhesive performance in geckos.
