Ultrathin Organic Microsupercapacitors for E-Skin and Implantable Electronics

Ultrathin energy storage and harvesting are rapidly developing for medical applications and wearable electronics. Powering implantable electronics requires thin and ultra-flexible energy storage devices, with suitable packaging material to prevent foreign body response or maintain a stable barrier. Using organic materials is promising to overcome these problems and printing methods enable scalable fabrication of all organic batteries or supercapacitors. Printing/coating methods are proven to achieve all printed symmetric microsupercapacitors (μSCs) on ultrathin parylene C substrates, where both electrode and gel electrolyte are based on the cheap and abundant biopolymer, cellulose¹. Paper electrodes provide mechanically robust, nanoporous networks for high energy density devices. The procedure of making paper electrodes allows an overall device thickness of around 10 µm, which can provide conformal device architecture. Another aspect of achieving smaller dimensions is parylene peel off technique, where high performance nanomaterials can be patterned as interdigitated structures. This method allows interdigitated electrodes down to 10 µm for cathodes. In our work, we have employed finite element analysis to calculate stress and strain in μSCs under different bending conditions, where an experimental bending radius of 2.5 mm is reached. These organic devices show long-term operation capability (90% of capacitance retention after 10⁴ cycles) and mechanical robustness (capacitance retention of 98% after 1000 cycles of bending). The developed skin like devices with organic materials are promising for supplying power to large area, scalable and low-cost wearables, and implants.<br/>1. M. G. Say, I. Sahalianov, R. Brooke, L. Migliaccio, E. Glowacki, M. Berggren, M. J. Donahue, I. Engquist, Adv. Mater. Technol. 2022, 2101420.