Interdigital capacitor-based passive lc resonant sensor for improved moisture sensing

Kristian Chavdarov Dimitrov, Sanghun Song, Hyungjun Chang, Taejun Lim, Yongshik Lee, Byung Jae Kwak

Research output: Contribution to journalLetterpeer-review

5 Citations (Scopus)


Herein, a passive low-profile moisture sensor design based on radio frequency identification (RFID) technology is proposed. The sensor consists of an LC resonant loop, and the sensing mechanism is based on the fringing electric field generated by the capacitor in the circuit. A standard planar inductor and a two-layer interdigital capacitor (IDC) with a significantly higher fringing capacitance compared to that of a conventional parallel plate capacitor (PPC) are used, resulting in improved frequency offset and sensitivity of the sensor. Furthermore, a sensor tag was designed to operate at an 8.2 MHz electronic article surveillance (EAS) frequency range and the corresponding simulation results were experimentally verified. The IDC-and PPC-based capacitor designs were comprehensively compared. The proposed IDC sensor exhibits enhanced sensitivity of 10% in terms of frequency offset that is maintained over time, increased detection distance of 5%, and more than 20% increase in the quality factor compared to sensors based on PPC. The sensor’s performance as a urine detector was experimentally qualified. Additionally, it was shown experimentally that the proposed sensor shows a faster response to moisture. Both simulation and experimental data are presented and elucidated herein.

Original languageEnglish
Article number6306
Pages (from-to)1-13
Number of pages13
JournalSensors (Switzerland)
Issue number21
Publication statusPublished - 2020 Nov 1

Bibliographical note

Funding Information:
Acknowledgments: This work was supported by QUI Inc.

Publisher Copyright:
© 2020 by the authors. Licensee MDPI, Basel, Switzerland.

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Biochemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Electrical and Electronic Engineering


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