Based on the observation of the natural senescence and experiment of the drying process of leaves, we establish phenomenological buckling models to explain the curled configuration of dried leaves, where the driving force is the differential contraction strain field. In the minimalist model, through a systematic study, the averaged buckling curvature is correlated with the aspect ratio and normalized size of the leaf, as well as the magnitude of the differential strain. In the refined model, the role of the vascular system is emphasized. Several main characteristics discovered through theoretical/ numerical studies are validated by proof-of-concept experiments using various types of leaves. The findings in this paper not only shed some light on the intriguing natural phenomena, but also may enable potential applications in three-dimensional fabrications using mechanical self-assembly.
The work is supported by National Natural Science Foundation of China (50928601), World Class University program from National Research Foundation of Korea (R32-2008-000-20042- 0), Changjiang Scholar Program from Ministry of Education of China, National Science Foundation (CMMI-0643726), and DARPA (W91CRB-11-C-0112).