Fully biodegradable printed electronic sensors based on biomass-derived graphene inks and agripapers

While printed electronic sensors present significant opportunities for the Internet of Things (IoT), industrial-scale production of these devices also raises numerous environmental concerns, including electronic waste generation and critical mineral depletion. Here, we circumvent these issues by demonstrating high-performance biodegradable printed electronic sensors based exclusively on agripaper substrates and graphene inks sourced from biomass. The agripaper substrate is produced from miscanthus and hemp, which are hardy, drought-tolerant agricultural crops. Meanwhile, the sensing layer is composed of cellulose nanocrystals derived from miscanthus, and graphene nanoplatelets derived from hardwood biochar. These plant-based printing materials are renewable, biodegradable, and readily processable at scale. The resulting printed electronic sensors exhibit superlative humidity sensitivity, showing a relative resistance change of 2.6 over a humidity range of 35–85% RH with response and recovery times of ~1 second and ~4 seconds, respectively. These sensors also perform well under humidity cycling and possess minimal confounding temperature dependence, outperforming traditional devices based on plastic substrates and metallic inks. By utilizing biomass for all raw materials, this additive manufacturing methodology is sustainable, minimizes supply chain risks, and provides an enabling step towards a circular bioeconomy.