Transfer Printing of Sub-5 μm Graphene Electrodes for Flexible Microsupercapacitors.

Printed graphene microsupercapacitors (MSCs) are attractive for scalable and low-cost on-chip energy storage for distributed electronic devices. Although electronic devices have experienced significant scaling to smaller formats, the corresponding miniaturization of energy storage components has been limited, with a typical resolution of ∼30 μm for printed graphene patterns to date. Transfer printing is demonstrated here for patterning graphene electrodes with fine line and spacing resolution less than 5 μm. The resulting devices exhibit an exceptionally small footprint (∼0.0067 mm2), which provides, to the best of our knowledge, the smallest printed graphene MSCs. Despite this, the devices retain excellent performance with a high areal capacitance of ∼6.63 mF/cm2 along with excellent electrochemical stability and mechanical flexibility, resulting from an efficient nonplanar electrode structure and an optimized two-step photoannealing method. As a result, this miniaturization strategy facilitates the on-chip integration of printed graphene MSCs to power emerging electronic devices.