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Proceedings Paper

The Texas horned lizard as model for robust capillary structures for passive directional transport of cooling lubricants
Author(s): Philipp Comanns; Kai Winands; Mario Pothen; Raya A. Bott; Hermann Wagner; Werner Baumgartner
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Paper Abstract

Moisture-harvesting lizards, such as the Texas horned lizard Phrynosoma cornutum, have remarkable adaptations for inhabiting arid regions. Special skin structures, in particular capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and to transport it to the snout for ingestion. This fluid transport is passive and directional towards the lizard's snout. The directionality is based on geometric principles, namely on a periodic pattern of interconnected half-open capillary channels that narrow and widen. Following a biomimetic approach, these principles were transferred to technical prototype design and manufacturing. Capillary structures, 50 μm to 300 μm wide and approx. 70 μm deep, were realized by use of a pulsed picosecond laser in hot working tool steel, hardened to 52 HRC. In order to achieve highest functionality, strategies were developed to minimize potential structural inaccuracies, which can occur at the bottom of the capillary structures caused by the laser process. Such inaccuracies are in the range of 10 μm to 15 μm and form sub-capillary structures with greater capillary forces than the main channels. Hence, an Acceleration Compensation Algorithm was developed for the laser process to minimize or even avoid these inaccuracies. The capillary design was also identified to have substantial influence; by a hexagonal capillary network of non-parallel capillaries potential influences of sub-capillaries on the functionality were reduced to realize a robust passive directional capillary transport. Such smart surface structures can lead to improvements of technical systems by decreasing energy consumption and increasing the resource efficiency.

Paper Details

Date Published: 22 April 2016
PDF: 11 pages
Proc. SPIE 9797, Bioinspiration, Biomimetics, and Bioreplication 2016, 979711 (22 April 2016); doi: 10.1117/12.2218873
Show Author Affiliations
Philipp Comanns, RWTH Aachen Univ. (Germany)
Kai Winands, Fraunhofer-Institut für Produktionstechnologie IPT (Germany)
Mario Pothen, Fraunhofer-Institut für Produktionstechnologie IPT (Germany)
Raya A. Bott, RWTH Aachen Univ. (Germany)
Hermann Wagner, RWTH Aachen Univ. (Germany)
Werner Baumgartner, Johannes Kepler Univ. Linz (Austria)

Published in SPIE Proceedings Vol. 9797:
Bioinspiration, Biomimetics, and Bioreplication 2016
Raúl J. Martín-Palma; Akhlesh Lakhtakia; Mato Knez, Editor(s)

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