Interfacial adhesion in flexible electronics: Materials, structures and applications

Flexible electronics, featuring low thinness, high conformability, multifunctionality, and high portability, have revolutionized the interaction experiences of human beings. This emerging technology is also ushering in groundbreaking advancements in intelligent manufacturing, humanoid robots, and digital medicine. However, the diverse functionalities and applications of flexible electronics often require integration of multilayer interfaces in devices. The assembly of such multilayer and multimaterial structures frequently faces challenges of interfacial incompatibilities of interfaces, including the mismatch in mechanical properties, chemistry, and functionalities. These challenges can compromise the long-term reliability and efficiency of either the interfaces in a device or the interface between a device and human tissues/robots. A seamlessly integrated flexible electronic device not only mitigates the risk of interfacial delamination but also enhances the mechanical stability of the device in dynamic or multifaceted environments. This manuscript offers an exhaustive review on tough interfaces in flexible electronics enabled by physical interactions, covalent chemical bonds or structural designs. Moreover, considering their primary applications — skin-wearables, implantable, and robotics — we delve into the latest breakthroughs, persistent challenges, and pragmatic strategies associated with reinforced adhesive interfaces. Such a discussion furnishes invaluable perspectives for the conceptualization and fabrication of highly durable flexible devices.