Saranraj Karuppuswami

In this paper, an RFID coupled batteryless digital sensor tag is proposed for detecting Ammonia in packaged food. An interdigitated capacitive sensor coated with a thin film of Polyaniline(PANi) that has a higher affinity towards Ammonia is used as a sensing element. To determining the sensitivity of the sensing element, (i) Wireless Near field Short range technique (Capacitance change), and (ii) Direct Probing (Resistance change) techniques are evaluated. The short range technique consists of an inductor coupled to the interdigitated capacitor to form an LC tank and the resonance (capacitance) change due to Ammonia loading is read using a pick-up coil. The direct probe technique uses two wires to measure the resistance across the interdigitated capacitor as a function of Ammonia concentration. Among the two techniques, for demonstrating long range sensing with digitization, direct probing is chosen as this is more stable and can detect a minimum of 3 ppm of Ammonia at room temperature with a response time of 30 min and recovery time of 60 min. The long range approach consists of an RF front end with an antenna and an energy harvester and a low power digital backend that converts the sensor data into bits for transmission. The entire system is passive in nature and does not require an external power supply for operation making it a low cost and simple solution that can be easily integrated as part of the RFID infrastructure. The ID integrated sensor tags are used for a myriad of quality control applications across the food supply chain spectrum.

In this paper, an identification integrated pH sensor tag is presented for wireless pH sensing applications. Two electrodes based on silver/silver chloride and antimony/antimony oxide were fabricated using the standard lithography process. The electrode pair showed a linear response for different pH solutions ranging from 4.3 to 10.7 with a sensitivity of 46 mV/pH. The passive pH sensor tag was implemented using a transceiver antenna, an energy harvesting circuit and a low power digital modulation circuit. The digital modulation circuit generates an identification and converts the analog pH voltage into 8-bit digital bits. The pH sensor tag demonstrated wireless digital bit transfer at a data rate of 0.595 Kbps. No external battery power is required to activate and operate the sensor tag and hence the sensor tag is passive in nature. In a complete wireless measurement setup, a read range of 45 cm was achieved for the sensor tag at transmit power of 15 dBm. The prototype was fabricated by integrating sensor and discrete components on top of a low cost PCB.

In this paper, a harmonic RFID (hRFID) system is proposed to overcome the challenges that limits the capabilities of a conventional UHF RFID system such as self-jamming and multi-path interference without any extensive modifications to the existing infrastructure. The proposed system exploits the third harmonic generation from the existing RFID chips for communication. The system is realized by designing an additional RF interface layer between the conventional RFID interrogator and the RFID tag. The interface layer transmits the query signal at the fundamental frequency and receives the backscattered harmonic signal from the RFID tag. It down converts the backscattered third harmonic signal to the fundamental frequency, and feeds it back to the conventional UHF interrogator for extracting the information. A dual band antenna design is also shown for improving the radiation efficiency of hRFID tags using a conventional RFID ICs with improved signal to noise ratio (SNR) and increased read range. A path is shown for improving the hRFID system by performing a study that relates the read range, RFID IC’s sensitivity, and the noise level with efficiency. The proposed system can be easily adapted to any of the current RFID applications.

In this paper, we propose a blockchain inspired internet-of-things architecture for creating a transparent food supply chain. The architecture uses a proof-of-object based authentication protocol, which is analogous to the cryptocurrency’s proof-of-work protocol. The complete architecture was realized by integrating a RFID based sensor at the physical layer and blockchain at the cyber layer. The RFID provides a unique identity of the product and the sensor data, which helps in real time quality monitoring. For this purpose, a small feature size 900 MHz RFID coupled sensor was fabricated and demonstrated for real time sensor data acquisition. The blockchain architecture aids in creating a tamper-proof digital database of the food packages at each instance. A detailed security analysis was performed to investigate the vulnerability of the proposed architecture under different types of cyber attacks.

A wireless antibody-free biosensor for rapid detection of pathogenic bacteria in milk was developed using dextrincapped gold nanoparticles (d-AuNP) as markers. The developed system consists of an interdigitated capacitor coupled to an inductor forming an inductor-capacitor (LC) resonant tank; a “Smart” vial onto which E. coli C3000 suspended in milk matrix adheres and are labeled with d-AuNP markers; and a wireless pick up coil. Detection is based on impedance loading of the interdigitated sensor by d-AuNP bound to the pathogenic bacteria. The resonance frequency shift of the LC tank is correlated with the concentration of E. coli cells in the milk. The sensors are field-operable and can detect bacteria counts as low as 5 log CFU/ml within an hour. Spectrophotometry is used to verify the sensitivity of the developed sensor. The resonance frequency of these sensors can be easily designed to match the existing radio frequency identification (RFID) frequency bands. The developed tag holds potential application in detection of a variety of pathogenic bacteria for quality control along the liquid food supply chain.

The design, analysis, and fabrication of a prototype triaxial applicator is described. The applicator provides both reflected and transmitted signals that can be used to characterize the electromagnetic properties of materials in situ. A method for calibrating the probe is outlined and validated using simulated data. Fabrication of the probe is discussed, and measured data for typical absorbing materials and for the probe situated in air are presented. The simulations and measurements suggest that the probe should be useful for measuring the properties of common radar absorbing materials under usual in situ conditions.

In this paper, a LC (inductor capacitor) wireless gas sensor is demonstrated for the identification of volatile organic compounds (VOC's) in the air environment. A near-field LC resonant tank consisting of an interdigitated capacitor fabricated on a porous flexible substrate coupled with an inductor coil is used as a sensor and its resonance is interrogated using an external pick up coil. The porous substrate enables capillary condensation of volatiles leading to a change in effective dielectric constant of the substrate which in turn shifts the resonance frequency. The designed sensor has multiple reuse capability and is applicable for continuous monitoring of volatiles such as methanol, iso-propyl alcohol, acetone and n-octane. The proposed sensor can wirelessly detect a 0.15 cc volume of volatiles in air making it highly sensitive. These sensors can be integrated with passive RFIDs in an array format for simultaneous detection of multiple volatile gases similar to an electronic nose. It can also be integrated with food packages to detect volatiles from food along the supply chain for quality control applications.