Laser Direct Writing of Flexible Sensor Arrays Based on Carbonized Carboxymethylcellulose and Its Composites for Simultaneous Mechanical and Thermal Stimuli Detection.

Multifunctional sensing devices with high flexibility, high sensitivity, and scalable fabrication are inevitable components of Internet of Things (IoT) for human-machine interfaces, structural health monitoring, and soft robots. Herein, high-performance flexible sensor arrays using carboxymethylcellulose (CMC) and its composite were developed for mechanical and thermal stimuli detection by laser direct writing. CMC contains abundant carbon precursors for strainsensitive laser-carbonized CMC (LC-CMC), while the incorporation of graphene oxide (GO) into CMC leads to the formation of thermal- sensitive laser-carbonized GO/CMC (LC-GO/CMC). The LC-CMC-based strain sensor delivers gauge factors of 487.7 (strain < 8.5%) and 8557 (8.5% < strain < 14%), with long-term stability over 10 000 cycles. With 0.2 wt % GO, the LC-GO/CMC-based device provides a temperature coefficient of resistance of -0.289% degrees C-1, higher than the Cr-based commercial sensor. The potential application of the devices in IoT is proved by combining the near-field communication technology with the LC-CMC-based device to monitor the strain suffered by 316L stainless steel during the fatigue test. Moreover, an integrated device based on the strain and temperature sensing arrays accomplishes the simultaneous measurement of temperature and mechanical deformation in real time.