Non-invasive liquid recognition based on interdigital capacitor

In this paper we investigated the possibility to conduct a non-invasive identification process of liquid samples packed in glass and polypropylene containers. Interdigital capacitor (IDC) structures were designed as solid (build using standard PCB fabrication procedure) and flexible (paper based) structure. Testing was performed using benzene, olive oil, acetone, alcohol, methanol, purified water and formaldehyde. Sample volume and container influence was examined. Information about the sample is available on a 2 × 16 character and through RS232 connection on PC. Experiments showed promising in building a portable and cost-effective sensing unit for on-field application where it is necessary to discriminate between several packed liquid samples.