Development and experimental verification of analytical models for printable interdigital capacitor sensors on paperboard

Printed interdigital capacitor (IDC) on paperboard is a promising solution for low-cost sensors in intelligent packaging applications. The currently available analytical models of multi-layered IDCs are targeted to those fabricated by conventional semiconductor process. For this reason, we have adapted two promising models and assessed their accuracies by comparison with experimental data. We modified these models by treating the paper as non-infinite thick substrate and taking the effect of printed metal thickness into account. The models are studied further to reveal the relationship between the response of capacitance change and various geometric parameters which enables a quick way of obtaining the optimum IDC structure design. The modified Gevorgian model fits our experimental data best, and the sensitivity of IDCs is largely affected by its spatial wavelength and the thickness of sensing material layer, while the finger number, length and metallization ratio have minor impact.