Tunable viscoelasticity of binary colloidal gels

The mechanical properties of colloidal gels depend strongly on the inter-particle interactions. We investigate the potential to engineer the linear viscoelastic properties of colloidal gels at low volume fractions by mixing two types of home-made polystyrene-poly(N-isopropylacrylamide) core-shell particles of largely different attraction strengths, 5kT and 30kT. We show that we can systematically tune the viscoelastic moduli of the binary mixtures by two orders of magnitude, and the spectra of the relaxation time by seven orders of magnitude, simply by altering their mixing proportions. Using confocal fluorescence microscopy and differential dynamic microscopy, we link these changes in the mechanical properties to the microscopic characteristics of the structure and dynamics of the gel networks.