Environmentally Friendly CO2-Derived Polycarbonate/Biopolymer Mixed Substrates and Hydroxypropyl Cellulose-Based Conductive Inks for Screen-Printed Piezoresistive Sensors

Environmental concerns arise over traditional printed circuit boards (PCBs) due to the large amount of materials required for their production, which complicates their recyclability and degradability. In the transition toward low environmental impact materials, printed electronics (PE) allow the use of polymeric substrates, meeting eco-friendly criteria. In this context, six sustainable printable substrates have been prepared consisting of three carbon dioxide-derived polycarbonates (CO2–PCs) blended with degradable polymers. CO2–PCs are synthesized from the reaction between epoxide and CO2 offering an alternative and sustainable greener synthesis in contrast to bisphenol A polycarbonates (BPA-PCs). A selection process among the six substrates was conducted in order to determine the most suitable one for piezoresistive (PR) applications. Based on characterization results, the poly(ethylene)carbonate (PEC)/polybutylene succinate (PBS) blend, referred to as PEC 1, has emerged as the most appropriate candidate. The substrate exhibits a contact angle (CA) ≈ 61.4 ± 0.6°, a melting temperature (Tm) ≈ 89.1 °C, Young’s modulus (E) ≈ 88.8 ± 14.9 MPa, and a strain at break (εb) ≈ 946.6 ± 117.8%. On this substrate, 8- and 16-line strain gauges have been screen-printed using a water-based hydroxypropyl cellulose (HPC)/nitrogen-doped reduced graphene oxide (N-rGO) sustainable ink. The sensitivity of screen-printed gauges has been evaluated, where the 8-line strain gauge demonstrated higher linearity with electrical resistance variation under bending. As the printed substrates constitute the largest part of many sensors, this work contributed to the transition from petrochemical polymers to sustainable options in order to bridge the gap toward eco-friendly paths.