Direct ink writing of fluoropolymer/CNT-based superhydrophobic and corrosion-resistant electrodes for droplet energy harvesters and self-powered electronic skins

Highlights: • Superhydrophobic and corrosion-resistant electrodes are fabricated using direct ink writing (DIW) method. • Fluoropolymer (FP)/CNT ink is synthesized by a simple method of mixing FP solutions and CNTs. • FP/CNT electrodes are mechanically and chemically robust. • A droplet-based electricity generator (DEG) with DIW-fabricated FP/CNT electrodes can power 50 LEDs. • Self-powered touch sensing function is realized on an electronic skin device with DIW-fabricated FP/CNT electrodes. Self-powered devices and systems that operate by harnessing environmental mechanical energies including raindrops and body motions have been extensively explored owing to their promising applications. In practical applications, these devices are often exposed to humid conditions or directly contact aqueous solutions. Here, we report the development of chemically inert and superhydrophobic electrode based on fluoropolymer (FP)/carbon-nanotube (CNT) that circumvents undesired metal electrode corrosion, deformation, and damage in harsh environments. The electrode surface can be patterned on flexible surfaces via direct ink writing (DIW), and no damage or corrosion is detected even being bent 10,000 times or immersed into salt/acid/alkaline solutions for 20 h. The integration of such robust electrodes with hydrophobic tribo-materials enables the construction of droplet-based electricity generators (DEGs) that exhibit an instantaneous current and power outputs of 2 mA and 0.12 W, respectively, and that light up 50 LEDs by one water droplet. Self-powered touch sensing function is also demonstrated on FP/CNT-based electronic skin, offering the broad applicability of the proposed electrode preparation strategy for self-powered devices.