Meeting Abstract

17.2  Tuesday, Jan. 4  Form and function in the wing membrane of bats CHENEY, J.A.*; BEARNOT, A; BREUER, K.S.; SWARTZ, S.M.; Brown University; Brown University; Brown University; Brown University jorn_cheney@brown.edu

Bat wings deform dramatically in flight. Kinematic measurements of bats during flight show that the skin which makes up the plagiopatagium, the region of the wing between the body and digit V, can undergo both spanwise and chordwise length changes of more than 50%. The elastic modulus of wing membrane skin, like that of most biological materials, is nonlinear with extremely high compliance at low strains (<0.1 MPa), that increase over an order of magnitude at higher biologically realistic strains. Wing tissue is also highly anisotropic and extremely tough, reaching very high strains before failure. Surprisingly, the wing tissue shows what we describe as a ‘pseudo’ negative Poisson’s ratio. In contrast to the complexity of the mechanical properties of the wing tissue, the architecture of the tissue has been reported as being a quite simple mesh-like network of elastin sandwiched between two layers of collagenous dermis. We describe anatomical studies that demonstrate that the connective tissue network of the wing is more complex than originally described, and show how the structural anisotropy we observe can better explain wing skin mechanical behavior.