Using Screen Printing Technology to Fabricate Flexible Sodium Ion Sensors

This study focused on the development of Na⁺ ion sensing devices on a flexible substrate and investigated the impact of various additive materials on its sensing performance. For the Na⁺ ion sensing aspect, the film on the carbon working electrode used tert-butyl calix[4]arene tetraethyl acetate as the ion carrier. The main component of the film was polyvinyl chloride (PVC), with a plasticizer added to enhance its flexibility, ensuring better adaptation to the flexible substrate. In this base formulation, graphene oxide (GO) or multi-walled carbon nanotubes (MWCNTs) were incorporated into the sensing electrode to explore their effects on Na⁺ ion sensing capabilities. The results demonstrated that adding MWCNTs significantly improved the sensor's sensitivity to Na⁺ ions. In addition, the study used the response slope to Na⁺ ions as a comparative reference for selectivity by calculating the ratio of the Na⁺ ion response slope to the response slopes of other ions (such as K⁺ and Ca²⁺). The findings showed that the sensors with MWCNTs exhibited better selectivity than the others with GO, and therefore, further analysis was performed on the response time of the sensors with MWCNTs. The results indicated that incorporating MWCNTs reduced the sensors' response time and enhanced their overall sensitivity. However, excessive addition of MWCNTs would lead to a decrease in the selectivity of the fabricated sensors. This suggests that while MWCNTs offer promising improvements in performance, their concentration must be carefully optimized to maintain the sensors' selectivity.