Variation in the mechanical properties of tracheal tubes in the American cockroach

Abstract

The insect cuticle serves the protective role of skin and the supportive role of the skeleton while being lightweight and flexible to facilitate flight. The smart design of the cuticle confers camouflage, thermo-regulation, communication, self-cleaning, and anti-wetting properties to insects. The mechanical behavior of the internal cuticle of the insect in tracheae remains largely unexplored due to their small size. In order to characterize the material properties of insect tracheae and understand their role during insect respiration, we conducted tensile tests on ring sections of tracheal tubes of American cockroaches (Periplaneta americana). A total of 33 ring specimens collected from 14 tracheae from 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 MJ m −3 ) were measured. We examined the high variance in mechanical properties statistically and demonstrated that ring sections excised from the same trachea exhibit comparable mechanical properties. Our results will form the basis for future studies aimed at determining the structure-function relationship of insect tracheal tubes, ultimately inspiring the design of multi-functional materials and structures.

Structure of tracheae and the functional implications for collapse in the American cockroach

“…Y and ν are the Young's modulus and the Poisson ratio of the tracheal tubes, respectively. They were set as Y=1.7 GPa and ν=0.3, based on our previous studies on tracheal material properties [13,14]. The tube's length was set to L=4 mm, the thickness to t=4 μm, and the semi-major axis to a=400 μm.…”

“…Modern imaging methods and preparation techniques can greatly enhance our knowledge about the microstructure of these tracheae. They may reveal not only how such microstructure relates to their respiratory function, but also how it affects their material behavior, which has been recently characterized [13,14].…”