“The demand for advanced functionalities in electronic devices is gaining traction in the scientific and industrial communities. In this context, printed electronics offer several advantages, such as low-cost processing and large-scale production compatibility, and are being studied for a wide range of applications in a variety of industries, including sensors, actuators, and electronics. Printing techniques, such as screen or inkjet printing, enable the production of electronic devices that are low in cost, easily scalable for industrial production, and flexible, while also being a more environmentally friendly technology. An ink typically contains at least three major components: nano- or microparticles, organic binder/additive dispersed or dissolved in solvent(s).
Among the different materials, graphene is one of the most suitable materials for the development of inks. Reduced graphene oxide is a two-dimensional (2D) material with exceptional mechanical, thermal, and electrical properties, making it an excellent choice for printed flexible electronics. Unlike metals, which may be scarce and cause environmental issues during extraction and refining, graphene can be produced from graphite in a highly scalable manner.
Most graphene inks use organic solvents such as N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF), both of which are toxic even at low concentrations, making them unsuitable for industrial production. As a result, there is an urgent need to replace those solvents with environmentally friendly alternatives. Bio-based solvents such as p-cymene, cyrene, cyclopentyl methyl ether (CPME), 2-methyl tetrahydrofuran (2-MeTHF), and dimethyl sulfoxide (DMSO) are viable options for developing printable high-performance devices.
This work will present several environmentally friendly formulations. Water-soluble polyvinylpyrrolidone (PVP), the natural and water-soluble polymer carboxymethyl cellulose (CMC), a chemical, thermal, and radiation-resistant polymer, poly(vinylidene fluoride) (PVDF), and elastomeric styrene-ethylene-butylene-styrene (SEBS) have all been used to create a variety of formulations. To achieve good rheological properties, the formulations were optimised in terms of the filler/binder ratio and solid content. The screen-printed films can achieve sheet resistance lower than Rsq< 100 Ω/sq. Furthermore, the multifunctionality of the inks is demonstrated by their use in a variety of sensing applications, including thermosensitive, piezoresistive, an 8-inch capacitive touch sensor, and humidity sensors. The materials’ multifunctionality is demonstrated, as is their potential for printed electronics while remaining environmentally friendly and biocompatible, with the PVP formulation capable of being thermoformed.