An Inkjet-printed Strain Sensor with a Carbon-Silver-Polyimide Topology

This paper presents a fully printed strain sensor consisting of carbon ink [1] coating layer and interdigitated shape silver (Ag) ink electrodes solidified on a polyimide (PI) substrate. The carbon ink provides an output of an increase in resistance when the substrate is bent because the occurred cracks break electrical conducting pathways in the solidified ink layer [2]. Improving on the works with only single carbon ink layer [2], an addition of the Ag ink electrodes brings extra resistance increase due to the occurrence of metallic cracks. A 1.5 × 1.5 cm size strain sensor is fabricated to verify the performance of our proposed topology. The results show that the maximum resistance change ratio of the sensor with interdigitated electrodes reaches 7.9%, which is ∼12.5% higher than that using carbon ink alone. Because of the low-cost fabrication and the improved sensing capability, our proposed strain sensor can be further optimized for wearable electronics and structure health monitoring applications.