Complex surface structure and locomotion

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In this project the PI will investigate, experimentally and theoretically, the role of complex biological integuments in animal locomotion. Two parallel research thrusts are planned: one investigation on the terrestrial limbless locomotion of snakes, and the other on the collective locomotion of semi-aquatic insects. A series of integrated experimental and theoretical investigations will be conducted on the propulsion of snakes on horizontal surfaces. Snakes exhibit four modes of locomotion, including lateral undulation, side winding, rectilinear progression and an accordion-like concertina motion. The goal of this research is to rationalize these limbless propulsion mechanisms. An existing theoretical framework will be adapted for investigation of the snake gaits. Particular attention will be given to assessing the snake's gains in efficiency and speed from dynamic lifting of its body during locomotion. Measurements of the snake's weight distribution during slithering will be obtained qualitatively using birefringent gelatin techniques and quantitatively using arrays of pressure transducers. An understanding of dynamic load-bearing mechanisms will shed insight onto the snake's energy budget and mechanisms for reducing abrasive wear. For the second part of the project, combined experimental and theoretical investigations will be made on the locomotion of insects that live above and below the water surface. An exploratory investigation will be conducted on the mechanisms by which fire ant colonies, whose individuals are hydrophilic and cannot swim, collectively form floating structures, ant balls that allow them to survive floods. Contact angles of the individuals and frozen ant balls will be measured and the dynamics of ants within the ball observed. A series of investigations of the locomotion of aquatic insects and gastropods will also be conducted, focusing on their wetting properties, propulsion using cilia and the body shapes which give them underwater stability near the free surface. The PI will develop an interdisciplinary undergraduate course in animal bio-locomotion in order to draw together students of biology and engineering and increase the visibility of integrative research. A bio-inspired walking-on-water theme will be planned for the school's annual design competition for mechanical engineering juniors. The PI will mentor two local high school students under the Intel Science Talent Search, in which he once participated.