Screen printed electrodes for capacitive level sensors

The paper reports on the fabrication and characterization of low-cost electrodes for capacitive level sensors realized on a flexible substrate. The aim is to prepare conductive electrodes by printing of silver and PEDOT:PSS pastes on coated PET foil. Individual capacitors in the form of interdigital electrodes (IDT) were designed with different finger width/spacing dimensions from 300/300 μm to 800/800 μm, a finger length 10 mm and 15 mm and an overall length of 100 mm. The printed structures were thermally laminated with covering PET foil. The sensitivity of the fabricated devices was characterized in liquids with different relative permittivity and conductivity (water and oil). The highest measured sensitivity was 0.7 pF/mm and 0.08pF/mm for water and oil respectively.