Experimental investigation into geometry-dependent practical behavior of all-solid-state reference electrodes

Almost all electroanalytical measurements require reference electrodes, creating a growing demand for low-cost, mass-producible, and stable reference electrodes. This study developed all-solid-state reference electrodes (ASSRE) via scalable manufacturing methods by using a combination of screen-printing and slot-die coating techniques. The correlation between the dimension of the reference membrane (RM) and the performance of the reference electrode was established by monitoring the potentiometric performances of electrodes with varying three-dimensional morphologies. Results indicated that the electrochemical performance of ASSRE is significantly influenced by their geometry. Increasing either the RM thickness or area enhances the ASSRE performance, particularly in terms of long-term stability and electrode-to-electrode reproducibility. The optimal performance was achieved by ASSRE with 160 µm thickness and 5 × 5 mm² area, exhibiting a low potential drift of 0.36 µV/h over 120 h, reproducibility of the standard potential within 0.2 mV, insensitivity to most interfering ions, and a 3-month shelf life. The reference electrode can be integrated into solid-state ion selective electrode (ISE), effectively replacing the conventional reference electrode. This study proposed a strategy to enhance the practical performance of flexible printed reference electrodes by optimizing their three-dimensional parameters.