| With broad potential applications in micro/nano-fabrication and bioengineering, the pattern self-assembled in thin film/substrate systems driven by buckling instability has become a focal point of research. However, most previous studies were limited to planar film/substrate systems, yet the curved substrates are highly relevant to quite a few natural and biological systems as well as three-dimensional (3D) engineering microcomponents.;In this dissertation, a comprehensive numerical and theoretical analysis is carried out on the mechanics underpinning the self-assembled buckling patterns of thin films on compliant curved substrates. Several fundamental geometries of the curved substrate as well as their combinations are investigated, focusing on the substrate curvature effect: the spheroidal shape that is often observed in quite a few natural fruits, vegetables, cells, and tissues; the cylindrical system that is often encountered in engineering microcomponents and plants; and their combination which mimics fingertips. For each system, comprehensive numerical simulations are carried out and the governing material and system parameters are identified from the palettes of buckle patterns, and simplified analytical models are established so that the closed-form formulae may be employed to effectively predict the wrinkle characteristics. The uncovered mechanical principles are useful for explaining the morphogenesis of quite a few natural and biological systems, as well as guiding the mechanical self-assembly fabrication of 3D micro and nano structures and devices.;Motivated by the intriguing undulating morphologies in some fruits and vegetables, a mechanics framework on the elastic buckling of a model spheroidal film/substrate system is first established, which effectively reproduces the global appearances of quite a few natural and biological systems. The buckle pattern is driven by anisotropic and inhomogeneous stress field of the film. The effect of curvature as well as its coupling with other material and geometrical parameters is revealed through numerical simulations and analytical models.;A comprehensive study on the instability of cylindrical film/substrate systems further provides guidelines for 3D micro-fabrications of gear-like microdevices. The mechanical self-assembly approach is inherently simple, quick, cost-effective, and applicable to a large range of materials and 3D structures that are not suitable for conventional photolithography. Spur gears and internal gears are available using isotropic films, and gears with inclined, herringbone, or reticular teeth are possible through the manipulation of anisotropy. The self-assembly fabrication is further extended to conical, spherical, and spheroidal substrates.;The combination of a half spherical head with a half cylinder resembles the shape of a fingertip. The underlying mechanics governing the wrinkling behavior of fingertips upon water immersion is numerically and analytically investigated. Theoretical guidance for the design of anti-aging and wrinkle-removal cosmetic products is established.;Additional manipulation of mechanical self-assembly can be realized via the gradient of film thickness or stiffness, thin film plastic deformation, as well as heterogeneity in mismatched deformation. These factors were neglected in previous studies, pilot numerical analyses are carried out and the potential mechanisms are unveiled in the present dissertation. The potential applications include the fabrication of branched fluid channels, channel networks, as well as the design of stretchable electronics.;The subject of mechanical self-assembly is a wide open area with numerous exciting potentials in engineering and biology remaining to be explored. |
