| Popis: |
Tree frogs adhere to surfaces using their toe pads. These pads secrete a fluid which enables them to adhere using a temporary adhesive mechanism known as wet adhesion. In keeping with the principles that govern this type of mechanism, the toe pads should be capable of adhering sufficiently and detaching effortlessly. However, the vast majority of research in this area has centred on static experiments, thus giving no real indication of the dynamic activity of the animal. Therefore, one aspect of this PhD project was to investigate the biomechanics of tree frog locomotion, focussing particularly on the kinematics and forces involved during toe pad detachment. Tree frog toe pads do indeed possess a rapid, efficient detachment mechanism, the toe pads simply peeling off of the surface from the rear, requiring very little force. The impact of this at higher scales was reflected in the force profiles of individual limbs, and in the global kinematics of the frog during locomotion. In addition to this, the wet adhesive mechanism itself was investigated by assessing the performance of tree frogs in a range of challenging conditions, including on overhangs and flooded surfaces. The latter condition compromises a key component of the wet adhesive mechanism; however, torrent frogs perpetually clamber across wet rocks in the vicinity of waterfalls, and yet are able to maintain their attachment. Therefore, the second aspect of this project was to compare the adhesive capabilities of tree- and torrent frogs, and propose explanations for the differences in their performance. Whilst comparable on dry, smooth surfaces, the adhesion of torrent frogs on rough, flooded substrates was far superior to that of tree frogs. Several explanations for this are offered, including the utilisation of a greater proportion of their ventral contact area, and a toe pad morphology that is optimised for such conditions. The results of this PhD project may provide a functional and morphological ‘blueprint’ for the development of toe pad mimics that can adhere in wet conditions. |
