Morphology and electrical properties of high-speed flexography-printed graphene.

Printed graphene electrodes have been demonstrated as a versatile platform for electrochemical sensing, with numerous examples of rapid sensor prototyping using laboratory-scale printing techniques such as inkjet and aerosol jet printing. To leverage these materials in a scalable production framework, higher-throughput printing methods are required with complementary advances in ink formulation. Flexography printing couples the attractive benefits of liquid-phase graphene printing with large-scale manufacturing. Here, we investigate graphene flexography for the fabrication of electrodes by analyzing the impacts of ink and process parameters on print quality and electrical properties. Characterization of the printed patterns reveals anisotropic structure due to striations along the print direction, which is related to viscous fingering of the ink. However, high-resolution imaging reveals a dense graphene network even in regions of sparse coverage, contributing to robust electrical properties even for the thinnest films (< 100 nm). Moreover, the mechanical and environmental sensitivity of the printed electrodes is characterized, with particular focus on atmospheric response and thermal hysteresis. Overall, this work reveals the conditions under which graphene inks can be employed for high-speed flexographic printing, which will facilitate the development of graphene-based sensors and related devices.

Titanium hydride nanoparticles and nanoinks for aerosol jet printed electronics.

Conductive inks commonly rely on oxidation-resistant metallic nanoparticles such as gold, silver, copper, and nickel. The criterion of air stability limits the scope of material properties attainable in printed electronic devices. Here we present an alternative approach based on air-stable nanoscale metal hydrides. Conductive patterns based on titanium hydride (TiH2) nanoinks were successfully printed on polyimide under ambient atmosphere and cured using intense pulsed light processing. Nanoparticles of TiH2 were generated by heating TiH2 powder in octylamine followed by wet ball milling, yielding <100 nm platelets. The addition of a suitable polymer dispersant during ball milling yielded stable colloidal dispersions suitable for liquid-phase processing. Aerosol jet printing of the resultant TiH2 nanoinks was demonstrated on glass and polyimide substrates, with a resolution as fine as 20 µm. Following intense pulsed light curing, samples on polyimide were found to exhibit a sintered, porous morphology with an electrical sheet resistance of ∼150 Ω â–¡-1.