Chemico-Capacitive Sensing via Dielectric Loading

Capacitive sensing is a powerful, digital-CMOS compatible sensing approach that has been under-utilized in industry beyond proximity sensing. Notable efforts that attempt to broaden the use capacitive sensing have predominantly focused on electrode functionalization that modify the metal surface to capture a targeted molecule that alters its measured capacitance. In the present work we concentrate on a novel use of capacitive sensing via changes to its dielectric layer that adsorb a material of interest, hence leading to measurable differences in its characteristics. Printed interdigitated capacitors capped with dielectrics capable of selectively adsorbing Zn ions and heavy metal ions are presented as examples to the proposed dielectric loading approach. Magadiite (Na
₂
Si
₁₄
O
₂₉
) provides the high selectivity for Zn and Dowex G26 (DG26) ion exchange resin serves as a dielectric with high affinity toward heavy-metal ions. Measured characteristics of these simple but effective capacitors show that they can be especially beneficial in low-cost sensing solutions that seek to qualitatively and quantitatively monitor a given analyte for contamination of a target metal. Moreover, our work attests to significant but little explored potential of capacitive sensing for chemical monitoring with high accuracy and low cost.