Newtonian to non-newtonian fluid transition of a model transient network

Giovanni Nava, Tie Yang, Valerio Vitali, Paolo Minzioni, Ilaria Cristiani, Francesca Bragheri, Roberto Osellame, Lucas Bethge, Sven Klussmann, Elvezia Maria Paraboschi, Rosanna Asseltaf and Tommaso Bellini

The viscosity of gel-forming fluids is notoriously complex and its study can benefit from new model systems that enable a detailed control of the network features. Here we use a novel and simple microfluidic-based active microrheology approach to study the transition from Newtonian to non-Newtonian behavior in a DNA hydrogel whose structure, connectivity, density of bonds, bond energy and kinetics are strongly temperature dependent and well known. In a temperature range of 15 °C, the system reversibly and continuously transforms from a Newtonian dispersion of low-valence nanocolloids into a strongly shear-thinning fluid, passing through a set of intermediate states where it behaves as a power-law fluid. We demonstrate that the knowledge of network topology and bond free energy enables to quantitatively predict the observed behavior using established rheology models.

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