Introduction 7315 1.1. Diversity of Monitoring Needs of Volatiles 7315 1.2. Chemical Interferences As the Key Noise Parameter for Wireless Sensors 7316 1.3. Goals and Scope of This Review 7317 1.4. Topics That Are Out of Scope of This Review 7317 2. Anatomy of Wireless Gas Sensors 7317 2.1. Active and Passive Wireless Sensors 7318 2.2. Transducers for Wireless Passive Sensors 7319 2.3. RFID Sensors 7320 2.4. Key Performance Factors of Wireless Sensors 7320 2.5. Summary of Specific Requirements for Wireless Gas Sensors 7321 3. Need for Transducers with Multiple Response Mechanisms 7321 3.1. Limitations of Sensor Arrays for Tethered and Wireless Gas Sensing 7322 3.2. Data Processing 7322 3.3. Multivariate Sensing 7323 4. Integration of Sensing Materials with Transducers 7323 6.3. System Approach for Development of Wireless Gas Sensors 7345 6.4. Path Forward 7345 Author Information 7346 Biographies 7346 Acknowledgment 7347 References 7347
The market demands for new sensors for food quality and safety stimulate the development of new sensing technologies that can provide an unobtrusive sensor form factor, battery-free operation, and minimal sensor cost. Intelligent labeling of food products to indicate and report their freshness and other conditions is one of important possible applications of such new sensors. We have applied passive (battery-free) radio frequency identification (RFID) sensors for highly sensitive and selective detection of food freshness and bacterial growth. In these sensors, the electric field generated in the RFID sensor antenna extends out from the plane of the RFID sensor and is affected by the ambient environment providing the opportunity for sensing. This environment may be in the form of a food sample within the electric field of the sensing region or a sensing film deposited onto the sensor antenna. Examples of applications include monitoring of freshness of milk, freshness of fish, and bacterial growth in a solution. Unlike other food freshness monitoring approaches that require a thin film battery for operation of an RFID sensor and fabrication of custom-made sensors, our developed passive RFID sensing approach combines advantages of both battery-free and cost-effective sensor design and offers response selectivity that is impossible to achieve with other individual sensors.
Articles you may be interested inCdSe quantum dots-poly(3-hexylthiophene) nanocomposite sensors for selective chloroform vapor detection at room temperature Highly sensitive passive radio frequency identification based sensor systems Rev. Sci. Instrum. 81, 025106 (2010); 10.1063/1.3316804Metal-ferroelectric-metal capacitor based persistent memory for electronic product code class-1 generation-2 uhf passive radio-frequency identification tag Comparison of organic diode structures regarding high-frequency rectification behavior in radio-frequency identification tagsSelective vapor sensors are demonstrated that involve the combination of ͑1͒ organic electronic sensing materials with diverse response mechanisms to different vapors and ͑2͒ passive 13.56 MHz radio-frequency identification ͑RFID͒ sensors with multivariable signal transduction. Intrinsically conducting polymers such as poly͑3,4-ethylenedioxythiophene͒ and polyaniline ͑PANI͒ 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 Ž ͑f͒ of the RFID antennas were inductively acquired followed by spectral processing of their real Z re ͑f͒ and imaginary Z im ͑f͒ parts using principal components analysis. The typical measured 1 noise levels in frequency and impedance magnitude measurements were 60 Hz and 0.025 ⍀, respectively. These low noise levels and the high sensitivity of the resonant RFID sensor structures resulted in NH 3 determinations with the 3 detection limit down to 20 ppb. This achieved detection limit was 25-50-fold better over chemoresistor sensors based on PANI films and nanowires.
We demonstrate roll-to-roll (R2R) fabrication of highly selective, battery-free radio frequency identification (RFID) sensors on a flexible polyethylene terephthalate (PET) polymeric substrate. Selectivity of our developed RFID sensors is provided by measurements of their resonance impedance spectra, followed by the multivariate analysis of spectral features, and correlation of these spectral features to the concentrations of vapors of interest. The multivariate analysis of spectral features also provides the ability for the rejection of ambient interferences. As a demonstration of our R2R fabrication process, we employed polyetherurethane (PEUT) as a "classic" sensing material, extruded this sensing material as 25, 75, and 125-μm thick films, and thermally laminated the films onto RFID inlays, rapidly producing approximately 5000 vapor sensors. We further tested these RFID vapor sensors for their response selectivity toward several model vapors such as toluene, acetone, and ethanol as well as water vapor as an abundant interferent. Our RFID sensing concept features 16-bit resolution provided by the sensor reader, granting a highly desired independence from costly proprietary RFID memory chips with a low-resolution analog input. Future steps are being planned for field-testing of these sensors in numerous conditions.
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