Cohesive behaviors of hydrogel under large-scale bridging

It has been recently revealed that large-scale bridging mechanism can be invoked to drastically improve the debonding resistance of hydrogel adhesion, but the optimization of the improvement remains elusive. Aiming at shedding light on the optimization, the present paper investigates the cohesive behaviors of hydrogel under the condition of large-scale bridging in 90-degree peel. A quasi-static model is established based on the principle of minimum potential energy, with the traction-separation law determined from experiments. The model is proved reliable in predicting the force-displacement response and the backing profile up to the peak peel force. Further theoretical analyses indicate that, within the range of interest, the peak peel force decreases with the extended length, increases with the Young's modulus of backing, increases then plateaus with the adhesion length and the thickness and bending stiffness of backing. In addition, the vertical displacement at peak peel force escalates with the extended length, remains mostly constant with varying adhesion length, declines with the Young's modulus of backing, and declines then stabilizes with increasing thickness and bending stiffness of backing. These theoretical insights may help tailor the material properties and geometric parameters for on-demand design of hydrogel adhesion as well as other soft adhesives for biomedicine and engineering.