Second-order elasticity of soft multilayer capsules: Universal relations and parametric studies

Composite gels are of key interest in bioengineering, e.g., as replacement tissues and substrates for stem cell cultures. Although gel elasticity plays a pivotal role in many bio-functions, there is insufficient knowledge on the effect of elastic nonlinearity, multilayer configuration and chemical concentration. To address such issues, multilayer capsules subjected to dilatation fluctuations are investigated using second-order elasticity, validated by universal curves for uniaxial tension and swelling of homogeneous gels. Detailed simulations show that the material inhomogeneity, elastic nonlinearity, shell thicknesses and fluctuation profile all have significant influence on the elastic fields, and hence may be selected to induce favorable microenvironment such as a tensile or compressive stress state appropriate for the targeted functionalities.