Keratin-Graphene Nanocomposite: Transformation of Waste Wool in Electronic Devices

Abstract

Electronic devices, designed to be long lasting, are commonly made with rigid, nondegradable materials. This, together with the presence of rare and toxic elements, creates significant issues for their waste management. The production of electronic devices, made with biodegradable materials that are sourced from waste streams of the agricultural sector, will create the premises for circular economy systems in the electronics sector that will increase its sustainability. Here, this new approach has been demonstrated by using keratin, the protein extracted from waste wool clips, combined with graphene to produce protein-based electronic materials. Resistors plane capacitors and inductors were fabricated, characterized and then assembled together to obtain analogue electrical circuits, such as, high-pass filters or resonators. Morphological structures, electrical characteristics, thermal stability and mechanical properties were fully investigated. Finally, a water-based ink of keratin and graphene was used to functionalize cellulose, obtaining flexible electrodes with remarkable sheet resistances (≈ 10 Ω/sq), ohmic I-V curves were obtained and the electrical conductivity after folding/unfolding cycles was measured. All the processing and fabrication methods used water as the only solvent. The described approach produced easily disposable electronics materials with reduced fingerprint on the environment, demonstrating that keratin from wool waste is an excellent candidate for the creation of circular economy systems in the electronics sector. The proposed valorization of waste materials for electronics applications is named "wastetronics".

Graphene oxide incorporated waste wool/PAN hybrid fibres

“…Therefore, the government, industry and academic researchers are focusing on the development of degradable but effective electronic devices using a green and sustainable fabrication process to overcome the environmental issues created by the e-wastes 2 . The selection and utilisation of bio-based agricultural waste materials to produce electronic devices are one of the prime aspects 3 . In production of electronic devices, the development of electrically conductive fibres has led to the fabrication and utilisation of textiles in smart applications (E-Textiles).…”

Green Biocomposites for Thermoelectric Wearable Applications

“…[31,44] Indeed, nanoparticles and nanostructures demonstrated a high potential to revolutionize TE materials increasing their efficiency. [18,[45][46][47][48][49] Among nanostructured materials, large-scale available carbon-based nanofillers, e.g., graphene nanoplatelets (GnPs), carbon nanofibers (CnFs), and multiwalled carbon nanotubes (CnTs), have been reported to be beneficial in a range of applications such as flexible [43,[50][51][52][53][54][55][56][57][58][59][60] and wearable [39,61] electronics, composites for thermal management [62,63] , electrodiagnostic [64,65] , structural reinforcement [52,63,66,67] , gas barrier [68] , solar cells [69][70][71] , electromagnetic interference shielding [53,64,72] and robotics [51,73] . Similarly, an increased interest in using these carbon-based nanomaterials has been also reported for TE applications, [24,33,[74][75][76]…”

Graphene–Polyurethane Coatings for Deformable Conductors and Electromagnetic Interference Shielding

“…The flexible conductor was subjected to extreme bending such that would be found in a foldable device or clothing; the conductor was folded in half (i.e., 180°) and unfolded repeatedly (Figure 2D). [ 60 ] To ensure a consistent fold, the fold edge was compressed with a 1.5 kg weight on each cycle. The ratio R flat / R 0 transverse to the fold line direction for 20 fold–unfold cycles is shown in Figure 2D.…”