A Generic Soft Encapsulation Strategy for Stretchable Electronics

Recent progress in stretchable forms of inorganic electronic systems has established a route to new classes of devices, with particularly unique capabilities in functional bio-interfaces, because of their mechanical and geometrical compatibility with human tissues and organs. A reliable approach to physically and chemically protect the electronic components and interconnects is indispensable for practical applications, since a direct exposure to the environment could lead to failure or damage of fragile elements. Although recent reports describe various options in soft, solid encapsulation, the development of approaches that do not significantly reduce the stretchability remains an area of continued focus. Here, we reported a generic, soft encapsulation strategy that is applicable to a wide range of stretchable interconnect designs, including those based on two-dimensional (2D) serpentine configurations, 2D fractalinspired patterns, and 3D helical configurations. This strategy forms the encapsulation while the system is in a pre-strained state, in contrast to the traditional approach that involves the strain-free configuration, followed by release of the pre-strain to complete the process. Combined theoretical modeling and experimental measurements highlight the deformation mechanisms of the interconnects encapsulated using both the proposed and the traditional strategy. A systematic comparison reveals that substantial enhancements (e.g., ~ 6.0 times for 2D serpentine, ~ 4.0 times for 2D fractal and ~ 2.6 times for 3D helical) in the stretchability can be achieved through use of the proposed strategy. Demonstrated applications in highlystretchable light-emitting diodes (LEDs) systems that can be mounted onto complex curvilinear surfaces illustrate the general capabilities in functional device systems.