Calligraphic pencil-on-paper strain sensors

Paper-based electronic devices, known as “papertronics”, have gained attention recently for their ease of fabrication, economic viability, biodegradability, and versatility in flexible electronics. However, sophisticated graphite deposition methods limit their development. This study presents a simple, fast, and inexpensive fabrication method for a tunable, hand-drawn papertronic strain sensor. A real-time resistance monitoring system was developed for the pencil-on-paper (PoP) strain sensor fabrication. The sensor's resistance was also controlled through sodium chloride (NaCl) impregnation and its performance was evaluated by variations in paper substrate and graphite source through different commercially available pencils. Results showed that NaCl-treated sensors had relative resistance change values of 120–160% compared to untreated samples with 20–40% relative resistance change values.