Viscoelastic Properties of Membranes Measured by Spherical Indentation

A series of bulk gels and free-standing membranes were fabricated from identical gelatin melts. Viscoelastic indentation load-relaxation tests were performed for both material geometries, where the indentation approximates a half-space for the bulk gels and a drumhead deformation test for the membranes. Elastic modulus values increased with gelatin concentration and gel strength and decreased with increasing indentation strain. There was more extensive load-relaxation in larger strain membranes. Numerical values of modulus were consistent between the two testing geometries, again exhibiting strain-dependent decreases. The membrane indentation method shows promise for characterizing the viscoelastic responses of biological tissue membranes and individual cells with potential application as a diagnostic technique.