Variability in Mechanical Properties of Insect Tracheal Tubes

Insects employ a network of tracheal tubes to transport oxygen directly to every cell of the body. During respiration, these tubes undergo localized and rhythmic deformations due to local variation in their structural and mechanical properties. In order to elucidate the mechanisms of insect respiration, mechanical tests on ring sections of tracheal tubes extracted from American Cockroaches were conducted. A total of 33 specimens collected from 14 tracheal tubes located in the upper thorax of the insects were successfully tested. The ultimate tensile strength (22.6 ± 13.3 MPa), ultimate strain (1.57 ± 0.68 %), elastic modulus (1740 ± 840 MPa), and toughness (0.175 ± 0.156 MJm ⁻³) were measured in the radial direction. The mechanical properties of ring sections excised from the same tracheal tube were shown to exhibit less variability than those of ring sections excised from different tracheal tubes. The results of this study will help in determining the relationship between the mechanics and structure of tracheal tube thus ultimately leading to the creation of novel bio-inspired micro-systems.