Steven Go

Development of radio-frequency identification sensors based on organic electronic sensing materials for selective detection of toxic vapors

Selective vapor sensors are demonstrated that involve the combination of (1) organic electronic sensing materials with diverse response mechanisms to different vapors and (2) passive 13.56 MHz radio-frequency identification (RFID) sensors with multivariable signal transduction. Intrinsically conducting polymers such as poly(3,4-ethylenedioxythiophene) and polyaniline (PANI) were applied onto resonant antennas of RFID sensors. These sensing materials are attractive to facilitate the critical evaluation of our sensing concept because they exhibit only partial vapor selectivity and have well understood diverse vapor response mechanisms. The impedance spectra Z(f) of the RFID antennas were inductively acquired followed by spectral processing of their real Zre(f) and imaginary Zim(f) parts using principal components analysis. The typical measured 1σ noise levels in frequency and impedance magnitude measurements were 60 Hz and 0.025 Ω, respectively. These low noise levels and the high sensitivity of the resona...

Selective quantitation of vapors and their mixtures using individual passive multivariable RFID sensors

We demonstrate passive (battery-free) radio frequency identification (RFID) devices for selective and sensitive chemical vapor sensing in the presence of ambient interfering gases. We developed two approaches for RFID sensing (1) when a sensing material is applied onto the resonant antenna to alter its impedance response and (2) when a complementary sensor is attached across an antenna and an integrated circuit (IC) memory chip to alter the impedance response of the sensor. In both approaches, these RFID sensors combine several measured parameters of impedance response with the multivariate analysis of these parameters. Thus, these individual sensors provide a unique capability of multiparameter sensing and rejection of environmental interferences. Sensitivity of developed RFID sensors provides detection of vapors at part-per-billion and part-per-million concentrations. Selectivity of developed RFID sensors facilitates selective quantitation of different individual vapors and their mixtures with a single sensor. Our passive RFID sensors were interrogated by the sensor reader at distances ranging from 0 to 33 cm and demonstrated their reliable operation even at the largest tested distance. In our sensing implementations, not the sensor but the sensor reader provides a 16-bit resolution and high signal-to-noise of the acquired signal. Rejection of interferences with a single sensor and the independence from costly proprietary RFID memory chips that have an analog input promise to impact numerous sensing applications.

Selective detection of chemical species in liquids and gases using radio-frequency identification (RFID) sensors

We demonstrate selective and sensitive chemical sensing based on battery-free passive radio frequency identification (RFID) sensors. Developed sensors are illustrated in sensing of ions and organic solvents in water and toxic vapors in air. These sensors are immune to variable ambient conditions, including air bubbles (in water sensing) and uncontrolled levels of relative humidity (in gas sensing).