Silver-decorated laser-induced graphene for a linear, sensitive, and almost hysteresis-free piezoresistive strain sensor.

A new approach has recently emerged in graphene synthesis by direct laser writing (LIG), which is highly economical and scalable, unlike previous methods. Here, the sputtering method has been used to coat silver onto the laser-induced graphene-based sensor. The results demonstrate that the chosen approach substantially impacts the expected outcomes. The initial resistance values were consistent across the different sensor samples. The average resistance was slightly lower in the silver-coated samples compared to the uncoated samples, demonstrating the effectiveness of the Ag coating in enhancing the electrical conductivity of the LIG material. However, the difference in resistance was not statistically significant. The electromechanical behavior of the Ag-coated LIG strain sensor was tested under cyclic tensile strain. The gauge factor increased from 12.9-14.7 for the uncoated LIG sensor to 17.2-26.7 for the Ag-coated sensor, with the difference growing at higher strains. At 5%, 30%, and 70% strain, the gauge factor increased by 30%, 80%, and 82%, respectively. Sensors measuring 1-70% strain were developed, enabling use in various applications. Blood pulse measurements showed the silver-coated sample produced more uniform and reliable results than the uncoated sample. The number of beats matched a commercial pulse oximeter. This sensitivity, linearity, and reliability demonstrate the potential for commercializing these sensors.