(322g) Elasticity of Small-Volume Biological Soft Matter By Cavitation Rheology

We evaluate the application of cavitation rheology to characterize the elasticity of biological soft matter that may be confined to volumes as small as 1 µL. Cavitation rheology, a technique developed by Zimberlin et. al (Soft Matter, 3(6), 765-767, 2007), is a simple, rapid method to characterize the mechanical properties of materials that can be approximated as linearly elastic by creating a bubble, or cavity, in a relatively small volume of the material. This technique relates the critical pressure necessary to form the cavity to the material elasticity in a limit where the bubble size is small relative to size of the specimen. For characterization of small volumes of biological soft matter, such as surface adherent bacterial biofilms, this method must be extended to accommodate situations in which the cavitation volume is finite relative to the specimen volume. We therefore investigated the underlying principles of cavitation rheology. From basic elasticity theory, we mathematically related the critical pressure to the sample elasticity for finite sample volumes and evaluated the results by numerical simulation. We use semi-dilute solutions of polyethylene oxide (PEO) to test the performance of cavitation rheology in the limit of small volumes and applied the method to evaluate the elasticity of Staphylococcus epidermidis biofilms.