Mechanical properties of tracheal tubes in the American cockroach (Periplaneta americana)

Insects breathe using an extensive network of flexible air-filled tubes. In some species, the rapid collapse and reinflation of these tubes is used to drive convective airflow, a system that may have bio-inspired engineering applications. The mechanical behavior of these tracheal tubes is critical to understanding how they function in this deformation process. Here, we performed quasi-static tensile tests on ring sections of the main thoracic tracheal trunks from the American cockroach (Periplaneta americana) to determine the tracheal mechanical properties in the radial direction. The experimental findings indicate that the stress–strain relationships of these tracheal tubes exhibit some nonlinearities. The elastic modulus of the linear region of the stress–strain curves tubes was found to be 1660 ± 512 MPa. The ultimate tensile strength, ultimate strain and toughness were found to be 23.7 ± 7.33 MPa, 2.0 ± 0.7% and 0.207 ± 0.153 MJ m−3, respectively. This study is the first experimental quantification of insect tracheal tissue, and represents a necessary step toward understanding the mechanical role of tracheal tubes in insect respiration. (Some figures in this article are in colour only in the electronic version)