Abstract
Printed impedimetric ion-selective sensors based on interdigitated electrodes (IDEs) enable low-cost and flexible ion sensing, yet the role of electrode geometry under practical printing constraints remains poorly understood. Here, dispense-printed carbon IDEs were systematically optimized by varying finger length and interelectrode gap to study their effect on interfacial capacitance and impedimetric response. Capacitance measurements and analytical IDE modeling reveal a tradeoff between electrical performance and printability, yielding an optimized geometry with a 7 mm finger length and a 250 μm gap. Dispense-printed potassium sensors integrating a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solid-contact layer and a drop-cast ion-selective membrane show stable, concentration-dependent responses from 0.1 to 100 mM. At 10 kHz, the normalized impedance change reaches up to 39% per decade. These results highlight geometry-aware IDE design for scalable printed impedimetric ion sensors.