Mechanical characterisation of reticulated albumin capsule membranes

Abstract

We used a microfluidic technique in order to study the mechanical properties of cross-linked albumin capsule membranes. The capsules were produced from aqueous human serum albumin (HSA) solutions with concentrations of 15%, 20%, 25% and 30% (w/v). The radii were in the range 55-80 m. We find that the capsules follow the neo-Hookean law, which is strain-softening and depends on one parameter, the surface shear modulus. A possible pre-inflation effect due to osmolarity is accounted for by imposing various values of pre-inflation. Small values of pre-inflation are sufficient to fit the data, which indicates that the capsule membrane is under small osmotic stress. Accounting for pre-inflation changes only slightly the surface shear elastic modulus of the membrane. Whatever the pre-inflation ratio, the shear modulus sharply increases with the HSA concentration from a low-value plateau.