Rapid Fabrication of Flexible and Stretchable Strain Sensor by Chitosan‐Based Water Ink for Plants Growth Monitoring

Rapid fabrication of flexible and stretchable sensors is essential for the emerging applications of wearable devices. In this study, a chitosan‐based water ink realizes fabrication of flexible and stretchable stain sensor by simply writing the ink and leaving it to dry for ≈15 min at room temperature. It is found that chitosan is an excellent binding material. The fabricated sensor shows an excellent gauge factor of 64 within strain 1%–8%, and can be stretched up to 60%. More importantly, the sensor can be directly written on the subject, and sensors written on plants show that plants can response to mechanical injuries within a few minutes. These results show that this method reduces the energy and time consumption in the fabrication procedure, realizes direct fabrication of sensors on subjects for wearable monitoring, and meets the requirements for personalized and on‐site applications. So, this chitosan‐based ink provides an attractive strategy for the fabrication and application of wearable devices.