Harnessing the interface mechanics of hard films and soft substrates for 3D assembly by controlled buckling

Abstract

Techniques for forming sophisticated, 3D mesostructures in advanced, functional materials are of rapidly growing interest, owing to their potential uses across a broad range of fundamental and applied areas of application. Recently developed approaches to 3D assembly that rely on controlled buckling mechanics serve as versatile routes to 3D mesostructures in a diverse range of high-quality materials and length scales of relevance for 3D microsystems with unusual function and/or enhanced performance. Nonlinear buckling and delamination behaviors in materials that combine both weak and strong interfaces are foundational to the assembly process, but they can be difficult to control, especially for complex geometries. This paper presents theoretical and experimental studies of the fundamental aspects of adhesion and delamination in this context. By quantifying the effects of various essential parameters on these processes, we establish general design diagrams for different material systems, taking into account 4 dominant delamination states (wrinkling, partial delamination of the weak interface, full delamination of the weak interface, and partial delamination of the strong interface). These diagrams provide guidelines for the selection of engineering parameters that avoid interface-related failure, as demonstrated by a series of examples in 3D helical mesostructures and mesostructures that are reconfigurable based on the control of loading-path trajectories. Three-dimensional micromechanical resonators with frequencies that can be selected between 2 distinct values serve as demonstrative examples.

Long wavy copper stretchable interconnects fabricated by continuous microcorrugation process for wearable applications

“…silicon wafers. On the other hand, a vertical wavy structure of metal interconnects with substrate wrinkling has been developed for high‐density wiring . Since the wavy structure is formed in the vertical direction with respect to an electrode substrate, a large number of electrodes can be patterned on the substrate.…”

“…On the other hand, a vertical wavy structure of metal interconnects with substrate wrinkling has been developed for high-density wiring. [30][31][32][33][34][35] Since the wavy structure is formed in the vertical direction with respect to an electrode substrate, a large number of electrodes can be patterned on the substrate. Previous studies have reported that to form a vertical wave shape, patterned electrodes can be attached to a prestretched rubber substrate that become wrinkled when the rubber returns to its natural state, [31][32][33] while In and Out of plain wrinkled electrodes have been developed for improving their stretchability.…”

“…Previous studies have reported that to form a vertical wave shape, patterned electrodes can be attached to a prestretched rubber substrate that become wrinkled when the rubber returns to its natural state, [31][32][33] while In and Out of plain wrinkled electrodes have been developed for improving their stretchability. 34 Wavy electrodes with centimeter scale large waves that were conductive polymer-coated bending fiber, 36 3D printed helical structure, 37,38 have been also constructed. However, the length of wavy electrodes is limited to several centimeters [33][34][35]39,40 because of the small rubber stretching machines and micromachining tools.…”

“…34 Wavy electrodes with centimeter scale large waves that were conductive polymer-coated bending fiber, 36 3D printed helical structure, 37,38 have been also constructed. However, the length of wavy electrodes is limited to several centimeters [33][34][35]39,40 because of the small rubber stretching machines and micromachining tools. Therefore, a continuous processing system to make long vertically wavy high conductive interconnects has been required especially for electronic textile applications.…”

An Inverse Design Method of Buckling-Guided Assembly for Ribbon-Type 3D Structures

“…Because of the compatibility with the well-established planar fabrication technologies, this approach can achieve high-speed, parallel assembly of 3D mesostructures with a broad range of thin-film materials and feature sizes, thereby paving the way to the development of novel micro-devices [7,[33][34][35][36]. Recent progress showed that strategic designs of 2D precursor structures [28,29,37] and deformable substrates [38][39][40] as well as the integration schemes [41][42][43][44] can substantially enrich the accessible range of 3D topologies. For example, the structured elastomer substrates with kirigami designs can introduce local rotational motions of the bonding sites to enable the formation of structures with chiral features and morphable shapes [39].…”