Thermally Controlled, Patterned Graphene Transfer Printing for Transparent and Wearable Electronic/Optoelectronic System

Graphene has been highlighted as a platform material in transparent electronics and optoelectronics, including flexible and stretchable ones, due to its unique properties such as optical transparency, mechanical softness, ultrathin thickness, and high carrier mobility. Despite huge research efforts for graphene-based electronic/optoelectronic devices, there are remaining challenges in terms of their seamless integration, such as the high-quality contact formation, precise alignment of micrometer-scale patterns, and control of interfacial-adhesion/local-resistance. Here, a thermally controlled transfer printing technique that allows multiple patterned-graphene transfers at desired locations is presented. Using the thermal-expansion mismatch between the viscoelastic sacrificial layer and the elastic stamp, a "heating and cooling" process precisely positions patterned graphene layers on various substrates, including graphene prepatterns, hydrophilic surfaces, and super-hydrophobic surfaces, with high transfer yields. A detailed theoretical analysis of underlying physics/mechanics of this approach is also described. The proposed transfer printing successfully integrates graphene-based stretchable sensors, actuators, light-emitting diodes, and other electronics in one platform, paving the way toward transparent and wearable multifunctional electronic systems.