Figure 1

(a) Rheometer with the transparent adjustable stage on the Olympus IX-81 inverted fluorescent confocal microscope. (b) Schematic depiction of our rheometric molecular imaging setup. (c) Storage and loss moduli ($G^{\prime }$ and $G^{\prime \prime }$) curves for the two DNA solutions at $23°\mathrm{C}$ as well as the normalized shear stress $\sigma$ by the plateau modulus $G_{\mathrm{pl}}$ as a function normalized shear rate (i.e., Wi) shown in the inset, where $G_{\mathrm{pl}}$ were estimated from the $G^{\prime }$ and $G^{\prime \prime }$ curves.Reuse & Permissions

Figure 2

(a) Velocity profile in the parallel disk geometry at the shear rate of $0.02{\mathrm{s}}^{-1}$ showing homogeneous shear, where the inset shows the shear stress growth as a function of time. (b) Corresponding coiled conformation of DNA anywhere across the gap at this low shear rate. (c) The stress growth as a function of time at ${\dot{\gamma }}_{\mathrm{app}}=0.5{\mathrm{s}}^{-1}$, where the inset indicates no slip prior to the stress overshoot and slip afterward the stress maximum. (d) Time-dependent conformational changes of DNA in the slip layer, where the arrow with “Shear” indicates that the DNA orientation is along the shearing direction. (e) The conformation of DNA across the gap during steady slip at ${\dot{\gamma }}_{\mathrm{app}}=0.5{\mathrm{s}}^{-1}$ ($t=100\mathrm{s}$).Reuse & Permissions

Figure 3

(a) Slip velocity $V_s$ versus Wi for both concentrations of 1.0% and 0.5% with $Z=55$ and 22, respectively. The velocity of bulk DNA molecules close to surface in absence of slip, i.e., for $\mathrm{Wi}<1$, obeys $V_{\mathrm{ns}}=R_g\times {\dot{\gamma }}_{\mathrm{ns}}$, where $R_g$ is the coil size and ${\dot{\gamma }}_{\mathrm{ns}}$ is the imposed shear rate. (b) The scaling of the bulk shear rate ${\dot{\gamma }}_b$ and slip length $b$ as a function of Wi for 1.0% DNA.Reuse & Permissions

Figure 4

(a) Steady-state velocity profile at ${\dot{\gamma }}_{\mathrm{app}}=5.0{\mathrm{s}}^{-1}$ and $t=60\mathrm{s}$, with the inset showing the shear stress growth. (b) The corresponding conformations of DNA in the slip layer during tumbling in steady state (at $t=60\mathrm{s}$) at an apparent shear rate of $5.0{\mathrm{s}}^{-1}$.Reuse & Permissions