The intermittent dynamics may also reveal material properties of the gel and its interaction with the channel walls. The frequency of ablation is presumably determined by a balance of adhesion forces and viscous shear forces, µ γ. Increases in ∆P at constant Q T suggest increasing local velocity and thus increasing shear forces. While alginate solution viscosity µ depends on alginate concentration, intermittent deposition/ablation behavior occurs at lower alginate concentrations in which the viscosity is similar to water. Therefore, the shear forces in the intermittent regime vary due to the shear rate rather than changes in viscosity, and accordingly with the velocity gradient within the cross-section of the channel. Using the measured peaks in ∆P , Eq. 1 can be used to estimate the degree of radial occlusion of the channel and thus the increase in local shear rate γ. In this way we estimate that the shear stresses at peak pressure, or the ablation stresses, are on the order of 1-10 Pa. Based on the relative increases in driving pressure, as seen in Fig. 3a and 3c, gels formed in lower concentration conditions experience more shear stress before ablation than those formed in the higher concentration conditions .