Effective and Scalable Graphene Ink Production for Printed Microsupercapacitors

Microsupercapacitors (MSCs) are increasingly important for the commercialization of miniaturized electronics thanks to their efficient use of space and seamless integration capabilities. Traditional manufacturing methods are often complex and costly, hindering large-scale production. In contrast, printing technologies offer a commercially viable alternative by enabling simpler, cost-effective, and high-output fabrication processes. Leveraging graphene, renowned for its outstanding conductivity and stability, further enhances commercial productivity by removing the need for separate current collectors, thus, streamlining manufacturing and reducing costs. This study introduces a novel fluidic liquid-phase exfoliation (FLPE) technique for creating graphene-based MSCs. By utilizing a coil-shaped tubing reactor within an ultrasonic bath, this method efficiently exfoliates graphite, yielding stable graphene inks at various concentrations. These inks are suitable for both inkjet and screen printing, forming interdigitated electrodes with decent conductivity. The resulting MSCs exhibit high areal capacitance, exceptional cycle stability, and a robust mechanical performance. Notably, inkjet-printed patterns surpass screen-printed ones in electrochemical and mechanical performance (50.6 and 40.2 μF/cm² at 1 μA/cm² for inkjet and screen printing, respectively) due to film morphology variations influenced by ink rheology. This research underscores the critical influence of ink rheology on the morphology and performance of printed graphene patterns, offering valuable insights into the progression of printed electronics.