Introduction

The speed at which electronics have entered every aspect of human life is expected to spike rapidly with the advent of wearable electronics and the internet of Things. Consequently, this sector’s waste generation will increase massively due to the fast obsolescence of existing electrical goods. Currently, most electrical components are inorganic, non-degradable, and bulk. Often, they can incorporate toxic substances such as heavy metals, brominated flame retardants, and polyhalogenated molecules, which are detrimental to the environment if disposed of incorrectly. To facilitate the management of e-waste, researches have turned to plant-based electronics called “Plant-e-tronics”. Plants are naturally biodegradable and present outstanding mechanical properties (e.g., flexibility and lightweight) which can be adapted and exploited for the fabrication of various electronic components.

Technical features

Presented is a cellulose-based composite material that is versatile, flexible, robust, partially biodegradable, and low-cost. Such composite is made by impregnating cellulose with an ink comprising protein-polymeric binders and electrically conductive nanomaterials (e.g., graphene nanoplatelets, carbon nanofiber, carbon nanotube, carbon black, silver nanoparticles, gold nanoparticles, aluminum nanoparticles, or mixtures of the above). The composite can be used in various applications, from electromagnetic shielding to antennas, photovoltaics cells and wearable electronics. The binder in the conductive ink is composed of at least one plant-derived protein (50-75 wt %) and aleuritic acid (25-45 wt %). The fabrication procedure is as follows:

1. The binding part of the ink consisting of at least one plant-derived protein (gliadin and/or zein,) and aleuritic acid. These materials are first dissolved in a solvent mixture;
2. The conductivity of the ink is obtained by dispersing an electrically conductive nanomaterial in the ink;
3. One side of the cellulose is then coated with the conductive ink;
4. Hot pressing is used on the coated cellulose substrate to fully impregnate the conductive ink within the cellulose material and to polymerize the aleuritic acid.

Possible Applications

• EMI shielding for security and defence, flexible antennas, photovoltaics electrodes, spectroscopy, optoelectronics, imaging, space science and biological sensing.

Advantages

• Flexible, biodegradable, easy to fabricate, and low-cost;
• Use of naturally occurring substances;
• No plasticizers required;
• Low environmental impact.