Meeting Abstract
77.4 Sunday, Jan. 6 Dynamic Mechanical Properties of the Elastic Protein, Resilin DUDEK, DM*; GOSLINE, JM; Univ. of British Columbia; Univ. of British Columbia dudek@zoology.ubc.ca
Elastic proteins are used in animals where long-range elasticity is needed for either energy storage, for damping of vibrations, for restoring structures to their resting position without involving muscles, and for allowing frequent, repeated, rapid deformations of material. Resilin, an elastic protein in arthropods, can withstand strains in excess of 3.0 with perfect recovery and suffers neither from creep or stress relaxation in static experiments. A highly versatile material, it can be found in insect structures used for locomotion, breathing, feeding, sound production, vision, and as a base for sensory hairs. Despite its obvious importance in the biomechanics of insects, the extent of our knowledge of resilin�s dynamic mechanical properties is limited to a single study by Jensen and Weis-Fogh (1962) with a sample size of one locust prealar arm (76% resilin). Using an unconventional method to determine resilience (R), they reported an often quoted and quite remarkable 97% resilience at low frequency decreasing slightly to 93% at 200 Hz. Using a conventional method (R = e-2&pi*tan(&delta)), Gosline (1980) reanalyzed this data and calculated that resilience actually decreases below 50% at high frequency. We tested the dynamic properties of the pleuro-subalar tendon of dragonflies (>99% resilin) from 1-200 Hz at temperatures between 1-80 ° C. We found resilin to function on its rubber plateau, with a complex modulus on the order of 1 MPa and a phase shift of between 0.02-0.05 radians. We calculate that resilin is highly resilient at frequencies up to 100 Hz, but appears to be entering a viscoelastic transition between 100-200 Hz where resilience values begin to fall (R~75% at 200 Hz). This transition may help explain why resilin-containing structures used at high rates are so relatively large. Funded by NSF IRFP to DMD.
