Flexible Polymeric Substrates for Electronic Applications

The miniaturization of electronics has been following Moore's Law for decades and has resulted in the development of sequentially evolutionized multifunctional nanoengineered devices. The conventional electronic devices are processed over planar hierarchically nanopatterned substrates having mechanical rigidity and stiffness which limit the degree of utility due to its inability to interface with soft curvilinear morphology, brittle nature, and inferior optical transparency. However, flexible substrates assembled over polymeric framework would, therefore, play a key role by offering light weighted thin film architecture, wearability, improved optical transparency, and morphological configuration to curvilinearity. The flexibility of substrate is defined when the material is processed such that individual component complies to a comparable degree of bending without deterioration of electronic/optoelectronic performance. Since the fabricated structure is pliable, the mechanical integrity of the structure governs the electromechanical performance of flexible electronic devices. The structure may undergo delamination, which occurs due to the stress field gradient developed due to the coefficient of thermal expansion, thereby generating a built-in strain potentially capable of breaking the adhering bonds. This article provides a consolidated review of numerous processing techniques to fabricate flexible electronics ranging from printing, sol-gel, chemical vapor deposition to chemical synthesis route, etc. and their applications in thin-film transistors, solar cells, sensors, health monitoring e-skins, optical devices, etc. along with a theoretical mechanical two layer film substrate model.