A semi-analytical model elaborates the effect of cohesive zone on the peeling behaviors of heterogeneous thin films

Film-substrate systems are prevalent in various industries, and manipulation of their adhesion strength is essential to guarantee their desired functionalities. Inspired by the heterogeneous characteristic of geckos’ spatulae, heterogeneous adhesion devices are proposed for enhanced directional adhesion, but experimental measurements of their adhesion strength are significantly lower than the theoretical predictions. This discrepancy is likely due to the cohesive zone, a factor that was usually overlooked in previous theoretical models. To elucidate the effects of the cohesive zone on the peeling behavior of bio-inspired heterogeneous thin films, we developed a semi-analytical model based on energy principles. In the model, the peeling force can be determined by two dimensionless parameters: the heterogeneity factor and the cohesive-zone factor. The heterogeneity factor significantly strengthens the adhesion when peeling from the soft side to the stiff side, and weakens the adhesion when peeling from the opposite direction. This indicates that heterogeneity simultaneously facilitates the attachment in soft-stiff direction and the detachment in stiff-soft direction. The cohesive-zone factor partially offsets the attachment enhancement by heterogeneity; however, the cohesive-zone factor has marginal impact on the detachment enhancement. This study systematically reveals the combined effects of heterogeneity and cohesive zone on the peeling behaviors of bio-inspired heterogeneous thin films and provides useful guidelines for the design of smart attachment/detachment adhesion systems.

For more details, please refer to our paper by the link below:
https://doi.org/10.1016/j.tws.2025.113357