title: A zero power harmonic transponder sensor for ubiquitous wireless μL liquid-volume monitoring.
abstract: Autonomous liquid-volume monitoring is crucial in ubiquitous healthcare. However, conventional approach is based on either human visual observation or expensive detectors, which are costly for future pervasive monitoring. Here we introduce a novel approach based on passive harmonic transponder antenna sensor and frequency hopping spread spectrum (FHSS) pattern analysis, to provide a very low cost wireless μL-resolution liquid-volume monitoring without battery or digital circuits. In our conceptual demonstration, the harmonic transponder comprises of a passive nonlinear frequency multiplier connected to a metamaterial-inspired 3-D antenna designed to be highly sensitive to the liquid-volume within a confined region. The transponder first receives some FHSS signal from an interrogator, then converts such signal to its harmonic band and re-radiates through the antenna sensor. The harmonic signal is picked up by a sniffer receiver and decoded through pattern analysis of the high dimensional FHSS signal strength data. A robust, zero power, absolute accuracy wireless liquid-volume monitoring is realized in the presence of strong direct coupling, background scatters, distance variance as well as near-field human-body interference. The concepts of passive harmonic transponder sensor, metamaterial-inspired antenna sensor, and FHSS pattern analysis based sensor decoding may help establishing cost-effective, energy-efficient and intelligent wireless pervasive healthcare monitoring platforms.
authors.affiliation: Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, United States of America.|Maxim Integrated, Dallas, TX 75240, United States of America.
authors.forename: Haiyu
authors.initials: H
authors.lastname: Huang
authors.affiliation: Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202, United States of America.
authors.forename: Pai-Yen
authors.initials: PY
authors.lastname: Chen
authors.affiliation: Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, United States of America.
authors.forename: Cheng-Hsien
authors.initials: CH
authors.lastname: Hung
authors.affiliation: Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, United States of America.
authors.forename: Ranjit
authors.initials: R
authors.lastname: Gharpurey
authors.affiliation: Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, United States of America.
authors.forename: Deji
authors.initials: D
authors.lastname: Akinwande
mesh_terms: D000465:Algorithms; D006801:Humans; D008962:Models, Theoretical; D058998:Remote Sensing Technology; D015203:Reproducibility of Results; D059015:Wireless Technology