Table of Contents

COVER

TITLE PAGE

DEDICATION

VISIONARY STATEMENT

PREFACE

RFID AND RF SENSORS
SIGNIFICANCE OF CHIPLESS RFID
WHY INCORPORATION OF SENSING ELEMENTS IN CHIPLESS RFID TAGS—THE HYPOTHESIS OF THE BOOK?
OVERALL OBJECTIVE
REFERENCES

ACKNOWLEDGMENTS

ABBREVIATIONS

SYMBOLS

CHAPTER 1: INTRODUCTION

1.1 TRACKING ID TECHNOLOGY
1.2 CHIPLESS RFID SENSOR SYSTEM
1.3 PROPOSED CHIPLESS RFID SENSOR
1.4 CHAPTER OVERVIEW
REFERENCES

CHAPTER 2: LITERATURE REVIEW

2.1 INTRODUCTION
2.2 TRADITIONAL RFID SENSORS
2.3 CHALLENGES AND LIMITATIONS OF CURRENT CHIPLESS RFID SENSORS
2.4 MOTIVATION FOR A NOVEL CHIPLESS RFID SENSOR
2.5 PROPOSED CHIPLESS RFID SENSOR
2.6 CONCLUSION
REFERENCES

CHAPTER 3: PASSIVE MICROWAVE DESIGN

3.1 INTRODUCTION
3.2 CHAPTER OVERVIEW
3.3 THEORY
3.4 DESIGN
3.5 SIMULATION AND MEASURED RESULTS
3.6 CONCLUSION
REFERENCES

CHAPTER 4: SMART MATERIALS FOR CHIPLESS RFID SENSORS

4.1 INTRODUCTION
4.2 SENSING MATERIALS
4.3 TEMPERATURE SENSING MATERIALS
4.4 HUMIDITY SENSING MATERIALS
4.5 H SENSING MATERIALS
4.6 GAS SENSING MATERIALS
4.7 STRAIN AND CRACK SENSING MATERIALS
4.8 LIGHT SENSING MATERIALS
4.9 OTHER POTENTIALS SMART MATERIALS FOR RF SENSING
4.10 DISCUSSION
4.11 CONCLUSION
REFERENCES

CHAPTER 5: CHARACTERIZATION OF SMART MATERIALS

5.1 INTRODUCTION
5.2 CHARACTERIZATION OF MATERIALS FOR MICROWAVE SENSING
5.3 X-RAY DIFFRACTION
5.4 RAMAN SCATTERING SPECTROSCOPY
5.5 SECONDARY ION MASS SPECTROMETER
5.6 TRANSMISSION ELECTRON MICROSCOPY
5.7 SCANNING ELECTRON MICROSCOPE
5.8 ATOMIC FORCE MICROSCOPY
5.9 INFRARED SPECTROSCOPY (FOURIER TRANSFORM INFRARED REFLECTION)
5.10 SPECTROSCOPIC ELLIPSOMETRY
5.11 UV–VISIBLE SPECTROPHOTOMETERS
5.12 ELECTRICAL CONDUCTIVITY MEASUREMENT
5.13 MICROWAVE CHARACTERIZATION (SCATTERING PARAMETERS—COMPLEX PERMITTIVITY, DIELECTRIC LOSS, AND REFLECTION LOSS) FOR SENSING MATERIALS
5.14 DISCUSSION ON CHARACTERIZATION OF SMART MATERIALS
5.15 CONCLUSION
REFERENCES

CHAPTER 6: CHIPLESS RFID SENSOR FOR NONINVASIVE PD DETECTION AND LOCALIZATION

6.1 INTRODUCTION
6.2 THEORY
6.3 PD LOCALIZATION USING CASCADED MULTIRESONATOR-BASED SENSOR
6.4 SIMULTANEOUS PD DETECTION
6.5 CONCLUSION
REFERENCES

CHAPTER 7: CHIPLESS RFID SENSOR FOR REAL-TIME ENVIRONMENT MONITORING

7.1 INTRODUCTION
7.2 PHASE 1. HUMIDITY SENSING POLYMER CHARACTERIZATION AND SENSITIVITY ANALYSIS
7.3 PHASE 2. CHIPLESS RFID HUMIDITY SENSOR
7.4 CONCLUSION
REFERENCES

CHAPTER 8: CHIPLESS RFID TEMPERATURE MEMORY AND MULTIPARAMETER SENSOR

8.1 INTRODUCTION
8.2 PHASE 1: CHIPLESS RFID MEMORY SENSOR
8.3 PHASE 2: CHIPLESS RFID MULTIPARAMETER SENSOR
8.4 CONCLUSION
REFERENCES

CHAPTER 9: NANOFABRICATION TECHNIQUES FOR CHIPLESS RFID SENSORS

9.1 CHAPTER OVERVIEW
9.2 FABRICATION TECHNIQUES
9.3 Electrodeposition
9.4 PHYSICAL VAPOR DEPOSITION
9.5 WET CHEMICAL SYNTHESIS
9.6 PLASMA PROCESSING
9.7 ETCHING
9.8 LASER PROCESSING
9.9 LITHOGRAPHY
9.10 SURFACE OR BULK MICROMACHINING
9.11 PRINTING TECHNIQUES
9.12 DISCUSSION ON NANOFABRICATION TECHNIQUES
9.13 CHIPLESS RFID SENSORS ON FLEXIBLE SUBSTRATES
9.14 CONCLUSION
REFERENCES

CHAPTER 10: CHIPLESS RFID READER ARCHITECTURE

10.1 INTRODUCTION
10.2 READER ARCHITECTURE
10.3 OPERATIONAL FLOWCHART OF A CHIPLESS RFID READER
10.4 CONCLUSION
REFERENCES

CHAPTER 11: CASE STUDIES

11.1 INTRODUCTION
11.2 FOOD SAFETY
11.3 HEALTH
11.4 EMERGENCY SERVICES
11.5 SMART HOME
11.6 AGRICULTURAL INDUSTRY
11.7 INFRASTRUCTURE CONDITION MONITORING
11.8 TRANSPORTATION AND LOGISTICS
11.9 AUTHENTICATION AND SECURITY
11.10 POWER INDUSTRY
11.11 CONCLUSION AND ORIGINAL CONTRIBUTIONS
REFERENCES

INDEX

End User License Agreement

List of Illustrations

CHAPTER 1: INTRODUCTION

Figure 1.1 Evolution of tracking ID technology
Figure 1.2 Block diagram of generic RFID system
Figure 1.3 Advancement of application areas of tracking ID technology with time
Figure 1.4 Functional evolution and features of tracking ID technology (a) optical barcode, (b) illustration of chipless RFID tag, and (c) illustration of chipless RFID sensor
Figure 1.5 Generic block diagram of proposed chipless RFID sensor system
Figure 1.6 Overall research aim and chapter overview

CHAPTER 2: LITERATURE REVIEW

Figure 2.1 Basic block diagram of active RFID sensor tag [6]
Figure 2.2 Classification of chipless RFID tag sensors
Figure 2.3 Generic SAW-based RFID tag [28]
Figure 2.4 Interrogation and coding of delay-line-based chipless tag [32]
Figure 2.5 Block diagram of retransmission-based chipless RFID tag
Figure 2.6 Operating principle of LH delay-line-based chipless RFID tag [40]

CHAPTER 3: PASSIVE MICROWAVE DESIGN

Figure 3.1 Overview of passive microwave components presented in this book
Figure 3.2 Organization of theory section
Figure 3.3 (a) Proposed λ/2 type tri-section SIR structure with two quarter wavelength tri-step SIRs as in (b) (here O is the short terminal)
Figure 3.4 Layout of a semicircular patch antenna on air gap layer
Figure 3.5 Illustration of N-slot rectangular patch
Figure 3.6 Illustration of frequency shifting technique for data encoding
Figure 3.7 ELC resonator and equivalent circuit
Figure 3.8 Dielectric sensing using superstrate
Figure 3.9 General structure of cascaded multiresonator-based chipless RFID sensor
Figure 3.10 Illustration of chipless RFID tag with multiple parameter sensing
Figure 3.11 Layout of the tri-section SIR at 825 MHz. The simulation was performed on Taconic TLX_0 substrate with relative permittivity ϵ_r = 2.45 and tan δ = 0.0019 and substrate thickness h = 0.5 mm. The CPW line was matched to 50 Ω. All the measurements are in millimeters
Figure 3.12 Surface current distribution of the SIR structure at (a) 1 GHz (outside resonant condition) and (b) 825 MHz
Figure 3.13 Photograph of fabricated SIR structure on Taconic TLX_0 substrate
Figure 3.14 Fabricated semicircular patch antenna: (a) top view; (b) perspective view
Figure 3.15 Photograph of UWB patch antenna connected to SIR filter for chipless RFID sensor operation
Figure 3.16 Layout of slot-loaded patch utilizing binary encoding. The dimensions are W = 5.5 mm; L = 6.8 mm; S_w = 0.2 mm; L_gap = 0.4 mm. Substrate Taconic TLX_0; height, h = 0.5 mm; ϵ_r = 2.45; tan δ = 0.0019 (not drawn to scale)
Figure 3.17 Layout of slot-loaded rectangular patch utilizing frequency shifting technique for data encoding. The simulation is performed in CST MWS with Taconic TLX_0 as substrate with a substrate height of 0.5 mm; ϵ_r = 2.45 and tan δ of 0.0019. The dimensions are W = 7.3 mm; L = 6.8 mm; L_gap = 0.3 mm; S_w = 0.2 mm
Figure 3.18 Illustration of frequency shifting technique for data encoding. Here, a particular slot can encode data bits 01, 10, and 11 depending on its resonant frequency
Figure 3.19 Layout of ELC resonator. The dimensions are S = 6 mm; L_s = 1.75 mm; G_s = 0.7 mm; W_s = 0.4 mm. Substrate Taconic TLX_0; height, h = 0.5 mm; ϵ_r = 2.45; tan δ = 0.0019
Figure 3.20 (a) Simulated E-field concentration at a frequency outside resonance (6 GHz). (b) E-field concentration at resonant frequency (6.96 GHz)
Figure 3.21 Design procedure for backscatterer-based chipless RFID sensor
Figure 3.22 Layout of chipless RFID tag sensor. The simulation was performed in CST MWS with Taconic TLX_0 as substrate with substrate height of 0.5 mm; ϵ_r = 2.45, and tan δ = 0.0019. The overall dimensions are 15 mm × 6.8 mm. Gap between two resonators G = 3 mm
Figure 3.23 Simulated current density of high data density, compact tag at frequency, (a) ELC resonator, (b) slot S₁, (c) slot S₂, and (d) slot S₃
Figure 3.24 Layout of chipless RFID tag sensor for multiple parameter sensing. The simulation was performed in CST MWS with Taconic TLX_0 as substrate with substrate height of 0.5 mm, ϵ_r = 2.45, and tan δ = 0.0019. The overall dimensions are 25 mm × 8 mm. The gap between resonators is 3 mm
Figure 3.25 Layout of compact, high data density tag sensor. W_n = 10 mm; L_n = 8 mm; S_w = 0.3 mm; L_gap = 0.2 mm; G_n = 0.6 mm; l_s = 1.75 mm; W_s = 0.4 mm; G_s = 0.6 mm
Figure 3.26 Simulated current density of high data density, compact tag at frequency, (a) ELC resonator, (b) slot S₁, (c) S₂, and (d) S₃
Figure 3.27 Simulated and measured insertion loss of 825 MHz SIR
Figure 3.28 Measured return loss (S₁₁) of semicircular patch antenna
Figure 3.29 Measured radiation pattern of patch antenna on air gap layer with LC matching section at the feed probe (a) E-plane and (b) H-plane
Figure 3.30 Measured insertion loss of (a) 775 MHz SIR (01), (b) 825 MHz SIR (10), and (c) cascaded SIR filters (00)
Figure 3.31 Simulated RCS magnitude versus frequency for the slot-loaded patch shown in Figure 3.16 for data bit combinations (a) “000,” (b) “010,” (c) “100” and (d) “001”
Figure 3.32 Simulated RCS magnitude versus frequency for tag 1, tag 2, and tag 3. The resonant frequencies of the tags are shown in Table 3.4 (column 4)
Figure 3.33 Photographs of fabricated tags
Figure 3.34 Experimental setup for tag measurement using two horn antennas. The right antenna is transmitting (Tx) and the left antenna is receiving (Rx)
Figure 3.35 Measured transmission coefficient (calibrated) versus frequency for tag 1, tag 2, and tag 3. The resonant frequencies of the tags are shown in Table 3.4 (column 4)
Figure 3.36 Simulated RCS magnitude versus frequency for the ELC resonator at 6.96 GHz
Figure 3.37 (a) Photograph of fabricated ELC resonator and (b) measured transmission coefficient of ELC resonator
Figure 3.38 Simulated tag sensor RCS versus frequency
Figure 3.39 (a) Photographs of fabricated tag sensor and (b) measured transmission coefficient of overall tag sensor
Figure 3.40 Simulated RCS spectrum of multiple parameter chipless RFID tag sensor
Figure 3.41 (a) Photographs of fabricated tag sensor and (b) measured transmission coefficient of overall tag sensor
Figure 3.42 Simulated RCS spectrum of highly compact chipless RFID tag sensor
Figure 3.43 (a) Photograph of fabricated tag sensor and (b) measured transmission coefficient of the tag sensor

CHAPTER 4: SMART MATERIALS FOR CHIPLESS RFID SENSORS

Figure 4.1 Flow diagram of content of the smart materials chapter
Figure 4.2 Classification of materials depending on the conductivity scale
Figure 4.3 Classification of sensing materials
Figure 4.4 Dielectric constant change of phenanthrene during sublimation [17]
Figure 4.5 Nyquist plots of measured cell impedance at (a) −10 °C and (b) 80 °C. EIS measurements were conducted at Monash Materials Engineering Laboratory
Figure 4.6 Measured conductivity of P₁₄PF₆ for various temperatures
Figure 4.7 Chemical formulas for (a) Kapton polymer and (b) PVA
Figure 4.8 Photograph of SIR filter loaded with CdS photoresistor
Figure 4.9 Measured |S₂₁| versus frequency for photoresistor-loaded SIR for different light intensities
Figure 4.10 Plot of resonant frequencies and |S₂₁| at initial resonance (710 MHz)
Figure 4.11 (a) Graphene wireless sensor, (b) sensor on tooth, (c) wireless readout of sensor, and (d) binding of pathogenic bacteria on graphene nanotransducer
Figure 4.12 APTES-modified SiNW sensor with pH sensing
Figure 4.13 Flexible multiparameter sensors based on nanoparticle
Figure 4.14 Ultrasensitive-flexible-silver-nanoparticle-based nanocomposite-resistive sensor for ammonia detection
Figure 4.15 Various smart materials versus physical parameters

CHAPTER 5: CHARACTERIZATION OF SMART MATERIALS

Figure 5.1 Flow diagram of contents of the chapter
Figure 5.2 Smart materials characterization techniques
Figure 5.3 Principle of X-ray diffraction technique
Figure 5.4 XRD picture of ZnO thin film
Figure 5.5 Energy level diagrams for Stokes and anti-Stokes inelastic scattering
Figure 5.6 Raman spectra of microcrystalline silicon film
Figure 5.7 High-resolution micrographs of silver nanoparticles with diameters ranging from 2 to 12 nm
Figure 5.8 FE-SEM images of flower-like ZnO nanorods with different magnifications synthesized by sol-hydrothermal process [7]
Figure 5.9 AFM picture of ZnO thin film
Figure 5.10 Typical FTIR spectra of microcrystalline silicon films
Figure 5.11 Schematic of SE measurement technique
Figure 5.12 Linearly polarized light incidence at interface with a semi-infinite medium
Figure 5.13 Schematic of light incidence into ambient-film-substrate
Figure 5.14 Measurement arrangement of spectroscopic phase modulated ellipsometer
Figure 5.15 Nominal sample structure
Figure 5.16 Optical model for surface roughness: (a) actual sample with nonabrupt “rough surface,” (b) optical model with “effective” roughness layer
Figure 5.17 (a) Continuous variation in the optical properties of the “graded” film and (b) approximation of the graded film with discrete layers
Figure 5.18 Flow chart of the procedure for an ellipsometric experiment
Figure 5.19 A typical cross-sectional TEM image and SE analysis
Figure 5.20 Transmittance spectra of Al-doped ZnO film measured by ultraviolet–visible (UV–vis) spectroscopy
Figure 5.21 Schematic of photoconductivity measurement
Figure 5.22 Dielectric measurement kits: (a) 1-port solid/liquid; 2-port (b) waveguide and (c) line resonators
Figure 5.23 Measured electric permittivity versus frequency for PVA water solution

CHAPTER 6: CHIPLESS RFID SENSOR FOR NONINVASIVE PD DETECTION AND LOCALIZATION

Figure 6.1 Organization of the chapter on noninvasive PD detection and localization
Figure 6.2 Proposed cascaded multiresonator-based chipless RFID PD sensor
Figure 6.3 Overview of proposed PD sensor system
Figure 6.4 Illustration of multiresolution effect in STFT analysis. The window length for the three cases is (a) M₁, (b) M₂, and (c) M₃. Here, M₁ > M₂ > M₃
Figure 6.5 Time-domain concurrent signals (a) without time delay and (b) with time delay. Here the signals from sensor S₁, S₂, and S₃ are separated by t₁, t₂, and t₃ seconds
Figure 6.6 Time–frequency representation of the signals shown in (a) panel (a) of Figure 6.5 and (b) panel (b) of Figure 6.5
Figure 6.7 (a) PD calibrator CAL2B and (b) oscilloscope DSA 72004
Figure 6.8 (a) Time-domain PD signal and (b) power spectrum of time-domain PD signal in (a)
Figure 6.9 Block diagram of the experimental setup
Figure 6.10 Captured PD signal in time domain transmitting through sensor (a) S₁, (b) S₂, and (c) S₃. Power spectrum of captured PD signal transmitting through (d) S₁, (e) S₂, and (f) S₃
Figure 6.11 Measured RF energy for three sensors for PD apparent charge of 10, 20, and 50 pC
Figure 6.12 2-D projection of surface plot obtained from spectrogram analysis on the PD signals captured (a) directly shown in Figure 6.8(a) and through the sensors (b) S₁, (c) S₂, and (d) S₃ (the location of signal attenuation is highlighted)
Figure 6.13 2-D projection of spectrogram for signal transmitted through sensor S₁ (a)–(c) refer to cases 1–3 in Table 6.1 (here the location of signal attenuation is highlighted)
Figure 6.14 Experimental setup for validating simultaneous PD detection
Figure 6.15 Captured combined time-domain signal from HV Unit 1 and Unit 2 shown in Figure 6.14
Figure 6.16 2-D projection of the spectrogram for signal shown in Figure 6.15. Plots (a)–(c) refer to cases 1–3 in Table 6.2 (here the location of signal attenuation is highlighted)

CHAPTER 7: CHIPLESS RFID SENSOR FOR REAL-TIME ENVIRONMENT MONITORING

Figure 7.1 Organization of the chapter on real-time environment monitoring
Figure 7.2 CPW line with smart material as superstrate
Figure 7.3 (a) Photograph of fabricated SIR resonator at 1025 MHz for humidity sensing polymer characterization (b) measured insertion loss (S₂₁) and reflection loss (S₁₁) of the SIR resonator
Figure 7.4 (a) Block diagram of overall experimental setup, (b) photograph of humidity sensing experiment carried out at Monash Microwave Antennas and RFID Sensors laboratory
Figure 7.5 Plot of relative humidity and temperature against time measured inside the chamber using data logger
Figure 7.6 Magnitude of measured insertion loss (S₂₁) versus frequency for different humidity conditions with Kapton as superstrate
Figure 7.7 Phase of measured insertion loss (S₂₁) versus frequency for different humidity conditions with Kapton as superstrate
Figure 7.8 Group delay of measured insertion loss (S₂₁) versus frequency for different humidity conditions with Kapton as superstrate
Figure 7.9 Magnitude of measured insertion loss (S₂₁) versus frequency for different humidity conditions with PVA as superstrate
Figure 7.10 Phase of measured insertion loss (S₂₁) versus frequency for different humidity conditions with PVA as superstrate
Figure 7.11 Group delay of measured insertion loss (S₂₁) versus frequency for different humidity conditions with PVA as superstrate
Figure 7.12 Measured sensitivity curve of the SIR resonator for resonant frequency (f_r) versus relative humidity (RH)
Figure 7.14 Measured sensitivity curve of the SIR resonator for normalized maximum group delay versus relative humidity (RH)
Figure 7.13 Measured sensitivity curve of the SIR resonator for normalized selectivity of resonance versus relative humidity (RH)
Figure 7.15 General structure of backscatterer-based chipless RFID humidity sensor
Figure 7.16 (a) Experimental setup inside the Esky chamber and (b) fabricated chipless RFID tag sensor on TLX_0 substrate
Figure 7.17 Measured transmission coefficient (calibrated) (S₂₁) versus frequency for the chipless RFID humidity sensor with PVA coating
Figure 7.18 Magnitude of measured insertion loss (S₂₁) versus frequency of ELC resonator with PVA superstrate for various RHs
Figure 7.19 Phase of measured insertion loss (S₂₁) versus frequency of ELC resonator with PVA superstrate for various RHs
Figure 7.20 Group delay of measured insertion loss (S₂₁) versus frequency of ELC resonator with PVA superstrate for various RHs
Figure 7.21 Measured sensitivity curve of the ELC resonator for resonant frequency (f_r) versus relative humidity (RH)
Figure 7.23 Measured sensitivity curve of the ELC resonator for maximum group delay versus relative humidity (RH)
Figure 7.24 Hysteresis curve for RH sensor

CHAPTER 8: CHIPLESS RFID TEMPERATURE MEMORY AND MULTIPARAMETER SENSOR

Figure 8.1 Organization of the chapter on chipless RFID memory and multiparameter sensor
Figure 8.2 Dielectric behavior of (a) reversible temperature-sensing material and (b) irreversible temperature-sensing material
Figure 8.3 Experimental setup in Monash Material Engineering Department Laboratory for preparation of 1 mole phenanthrene: THF solution
Figure 8.4 (a) Photograph of phenanthrene-loaded ELC resonator. (b) ELC resonator after sublimation
Figure 8.5 Measured resonant frequency of ELC resonator versus time for the set temperatures 65, 75, 85, and 95 °C
Figure 8.6 Measured magnitude of transmission coefficient (S₂₁) of ELC resonator for different times at 85 °C
Figure 8.7 Measured phase of transmission coefficient (S₂₁) of ELC resonator for different times at 85 °C
Figure 8.8 Measured magnitude of transmission coefficient (S₂₁) of ELC-coupled chipless RFID tag (inset photo) for temperature threshold sensing
Figure 8.9 Illustration of a backscatterer-based chipless RFID multiparameter sensor
Figure 8.10 Photograph of humidity and temperature sensing tag sensor
Figure 8.11 Measured magnitude of transmission coefficient (S₂₁) of multiple parameter chipless RFID tag
Figure 8.12 Measured magnitude of transmission coefficient (S₂₁) of multiple parameter chipless RFID tag for humidity sensing below threshold temperature (25 °C)
Figure 8.13 Measured magnitude of transmission coefficient (S₂₁) of sensing ELC resonators for humidity monitoring below threshold temperature (25 °C)
Figure 8.14 Measured magnitude of transmission coefficient (S₂₁) of sensing ELC resonators for humidity monitoring above threshold temperature (85 °C)

CHAPTER 9: NANOFABRICATION TECHNIQUES FOR CHIPLESS RFID SENSORS

Figure 9.1 Contents flow diagram of this chapter
Figure 9.2 Classification of fabrication techniques
Figure 9.3 Various nanofabrication techniques
Figure 9.4 Electrolyte cell for the deposition of copper from copper sulfate solution
Figure 9.5 Thin-film evaporation setup
Figure 9.6 Schematic of a two electrode setup for RF sputtering deposition
Figure 9.7 Schematics of molecular beam epitaxy growth chamber molecular beam
Figure 9.8 Synthesis step of metal nanoparticles in wet chemical method
Figure 9.9 The schematic diagram of the low- and high-pressure high-density microwave plasma utilizing the spoke antenna and wave guide, respectively
Figure 9.10 Typical etching process
Figure 9.11 Overview of the various applications and parameter regimes employed in laser processing. PLA/PLD, pulsed-laser ablation/deposition; LA, laser annealing; LC, laser cleaning; LIS, laser-induced isotope separation/IR-laser photo chemistry; MPA/MPI, multiphoton absorption/ionization; LSDW/LSCW, laser-supported detonation/combustion waves; LCVD, laser-induced chemical vapor deposition; LEC, laser-induced electrochemical plating/etching; RED/OX, long pulse or CW CO₂-laser-induced reduction/oxidation
Figure 9.12 (a) Design of tag on polymer substrate by CST software and (b) fabricated tag on polymer substrate by laser etching
Figure 9.13 Measured S₂₁ magnitude and phase for pH sensor at different pH environment
Figure 9.14 Optical mask types
Figure 9.15 UV radiation is deposited on the substrate surface
Figure 9.16 Flowchart of a typical photolithography process
Figure 9.17 Steps in optical printing using photolithography
Figure 9.18 Typical sequential steps of EBL
Figure 9.19 The essentials of NIL
Figure 9.20 Classification of nanoimprint lithography (NIL)
Figure 9.21 Steps in thermal imprint lithography
Figure 9.22 A basic scheme of UVNIL process
Figure 9.23 (a) Reverse contact UVNIL–RUVNIL, (b) three-layer woodpile-like structure by RUVNIL, (c) cross-section of a two-layer woodpile-like structure—no evidence of polymer flow in grooves.
Figure 9.24 SEM image of the fabricated template. The inset image shows the detail of the template
Figure 9.25 (a) Schematic view of the NW transfer steps by trilayer NIL on SU8/SiO₂/PMMA structure; (b) SEM image of the sample after imprint; and (c) SEM image of the sample after removing PMMA and formation of undercut
Figure 9.26 Surface micromachining techniques
Figure 9.27 (a) The screen-printing process; (b) lines on an alumina tube screen-printed with IKO screen printer model T-620-80200
Figure 9.28 The process illustration for the screen-printing process
Figure 9.29 Inkjet printing: (a) continuous inkjet (CIJ) printing: multiple deflection system; (b) drop on-demand (DOD) system: single droplets ejected through an orifice at a specific point or time
Figure 9.30 Inkjet-printed sensor tag
Figure 9.31 Fabrication of polyaniline-based gas sensors using piezoelectric inkjet and screen printing for the detection of hydrogen sulfide (interdigitated electrodes with inkjet-printed films of (a) PANI, (b) PANI-(preexposure), and (c) PANI-(postexposure). Insets compare optical microscopy of the electrode digits and sensor films
Figure 9.32 A sensor microarray realized by laser printing of polymers
Figure 9.33 The process to print the conductive tracks and sensing materials simultaneously on a polymer substrate
Figure 9.34 The roll-to-roll printable chipless RFID sensor

CHAPTER 10: CHIPLESS RFID READER ARCHITECTURE

Figure 10.1 Overall architecture of chipless RFID sensor reader
Figure 10.2 Detailed architecture of RF module
Figure 10.3 Photograph of RF module of chipless RFID reader developed by MMARS lab
Figure 10.4 Operation of a VCO for discrete tuning voltage
Figure 10.5 Functional block diagram of a chipless RFID reader [1]
Figure 10.6 A flow diagram of chipless RFID reader operation

CHAPTER 11: CASE STUDIES

Figure 11.1 Illustration of wireless sensor network in multidimensional applications
Figure 11.2 Application areas of chipless RFID sensor network
Figure 11.3 Chipless RFID sensor in food safety and quality control
Figure 11.4 Coke can and milk carton with chipless RFID sensors
Figure 11.5 (a) A typical milk carton tagged with chipless RFID pH sensor, (b) highly compact chipless RFID sensor using ELC resonator, and (c) cross section of resonator structure showing different layer of materials
Figure 11.6 Application areas of chipless RFID sensors in healthcare
Figure 11.7 Traditional wristband type chipped RFID tag reading
Figure 11.8 Wristband type printed chipless RFID tag for patient tracking
Figure 11.9 Monitoring implant healing after surgery
Figure 11.10 A smart bandage by researchers at Seoul National University can record muscle activity and trigger the release of a drug.
Figure 11.11 Wireless e-pill monitoring
Figure 11.12 Illustration of e-pedigree proposed by GS1
Figure 11.13 Various applications of chipless RFID sensors in emergency services
Figure 11.14 Future smart home embedded with wireless sensor
Figure 11.15 Proposed chipless RFID-based WSN in agricultural fields
Figure 11.16 (a) 100 AUD with probable line of folding, (b) delay line scatterer, (c) theoretical stress–strain curve for polymer note, and (d) resonant frequency versus stress for delay-line scatterer fabricated on polymer notes
Figure 11.17 Illustration of a power distribution monitoring system using RFID sensor network

List of Tables

CHAPTER 3: PASSIVE MICROWAVE DESIGN

Table 3.1 Critical Parameters of L-slot Semicircular Patch Antenna
Table 3.2 Data Bit Represented by Cascaded Multiresonator-based Chipless RFID Sensor
Table 3.3 Value of Frequency Shifting Parameters and Corresponding Frequency Band
Table 3.4 Simulated Frequency Shifting Parameter and Corresponding Resonant Frequency for Designed Tags

CHAPTER 4: SMART MATERIALS FOR CHIPLESS RFID SENSORS

Table 4.1 Measured NSL-6112 Photoresistor Impedances for Varying Light Intensities at UHF
Table 4.2 List of Smart Materials with Their Advantages and Limitations
Table 4.3 Summary of Smart Materials with Microwave Sensing Capabilities

CHAPTER 5: CHARACTERIZATION OF SMART MATERIALS

Table 5.1 A Summary of Characterization Techniques for Sensing Materials

CHAPTER 6: CHIPLESS RFID SENSOR FOR NONINVASIVE PD DETECTION AND LOCALIZATION

Table 6.1 Values of Window Length and Time Resolution for Different Observations in Figure 6.13
Table 6.2 Calculated and Measured Time Delay for Different Observations for The Experimental Setup in Figure 6.16

CHAPTER 7: CHIPLESS RFID SENSOR FOR REAL-TIME ENVIRONMENT MONITORING

Table 7.1 Sensitivity Parameters for Kapton and PVA Dielectrics

CHAPTER 9: NANOFABRICATION TECHNIQUES FOR CHIPLESS RFID SENSORS

Table 9.1 Different Fabrication Methods of Sensing Materials
Table 9.2 Different Fabrication Techniques of Sensors

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To my mother, beloved wife, Sima, and son, Dhritisundar, and daughter, Joyeeta

PREFACE

RFID AND RF SENSORS

Radio frequency identification (RFID) is an emerging wireless technology for automatic identifications, access controls, tracking, security and surveillance, database management, inventory control, and logistics. However, the application-specific integrated circuits (ASICs) in the chipped RFID tags make the tag costly and hinder their applications in mass tagging. Chipless RFID tags are voids of these microchips. Some chipless RFID are fully printable passive microwave and mm-wave circuits. They can be produced very cheaply. Integration of physical parameter sensors with chipless RFID will open up a new domain for energy-efficient housing, control and monitoring of perishable items, equipment, and people. In the new millennium, low-cost ubiquitous tagging and sensing of objects, homes, and people will make the system efficient, reduce wastage, and lower the healthcare budget. This book presents various sensing techniques incorporated in the chipless RFID systems.

The RFID has two main components—a tag and a reader. The reader sends an interrogating radio signal to the tag. In return, the tag responds with a unique identification code to the reader. The reader processes the returned signal from the tag into a meaningful identification code. Some tags coupled with RF sensors can also provide data of surrounding environment such as temperature, relative humidity, pressure or impact, moisture content, and location.

The tags are classified into active, semi-active, and passive tags based on their onboard power supplies. An active tag contains onboard battery to energize the processing chip and amplify signals. A semiactive tag contains a battery as well, but the battery is used only to energize the chip, hence yielding better longevity compared to the active tag. A passive tag does not have a battery. It scavenges power for its processing chip from the interrogating signal from the tag, hence last forever. However, the processing power and reading distance is limited by the transmitted power of the reader.

SIGNIFICANCE OF CHIPLESS RFID

As stated earlier, the main constraint of mass deployment of RFID tags for low-cost item tagging is the cost of the tag. The main cost comes from the microchip of the tag. If the chip can be removed without losing functionality of the tag, then the tag can be produced in subcents and has the potential to replace the optical barcode.

The optical barcode has limitations in operation such as each barcode is individually read, needs human intervention, and has less data handling capability. Soiled barcodes cannot be read and barcodes need line-of-sight operation. Despite these limitations, the low-cost benefit of the optical barcode makes it very attractive as it is printed almost without any extra cost. Therefore, there is a pressing need to remove the ASIC from the RFID tag to make it competitive in deployment to coexist or replace trillions of optical barcodes printed each year. The solution is to remove the ASIC from the RFID tag. The tag should be fully printable on low-cost substrates such as paper and plastics similar to the optical barcodes. A reliable prediction by the respected RFID research organization IDTechEx advocates [1] that 60% of the total tag market will be occupied by the chipless tag if the tag can be made in less than one cent.

However, removal of signal processing ASIC from the tag is not a trivial task. It needs tremendous investigation and investment in designing low-cost but robust passive microwave circuits and antennas using conductive ink on low-cost substrates. However, obtaining high fidelity response from low-cost lossy materials is very difficult. To overcome these challenges, new materials characterization and fabrication processes are to be innovated for chipless RFID tags and sensors. In the interrogation and decoding sides of the RFID system is the development of the RFID reader, which is capable to read the chipless RFID tag. The authors' group has tremendous progress in this frontier developing multiple chipless RFID tag readers in 2.45, 24, and 60 GHz frequency bands. Currently, only a few fully printable chipless RFID tags, which are in the inception stage, are reported in the literature. They are a capacitive gap coupled dipole array [2], a reactively loaded transmission line [3], a ladder network [4], and finally, a piano and a Hilbert curve fractal resonators [5]. These tags are in prototype stage and no further development in commercial grade is reported so far. Only commercially successful chipless RFID is RF-SAW, but they are not printable and expensive [6]. There is much stride to develop thin-film transistor circuit (TFTC) chipless tags to attract huge market of high-frequency (HF) tags [7]. However, they are complex circuits and need complex fabrication processes. To fill up the gap in the literature of the potential chipless RFID field, the author's chipless RFID research team has been working on the paradigm chipless RFID tag since 2004. The designed tag has mainly targeted to tag Australian polymer banknotes, library access cards, and apparels [8–11].

Significant successes have been achieved to tag not only the polymer banknotes but also many low-cost items such as books, postage stamps, secured documents, bus tickets, and hung-tags for apparels. The technology relies on encoding spectral signatures and decoding the amplitude and phase of the spectral signature. The other methods are phase encoding of backscattered spectral signals and time-domain delay lines. So far as many as more than 10 chipless RFID tags [8–11] and three generations of readers [12] are designed. The proof-of-concept technology is being transferred to the banknote polymer and paper for low-cost item tagging. These tags have potential to coexist or replace trillions of optical barcodes printed each year [9]. To this end, it is imperative to invest in low-loss conducting ink, high-resolution printing process, and characterization of laminates on which the tag will be printed. The design needs to push in higher frequency bands to accommodate and increase the number of bits in the chipless tag to compete with optical barcodes. The book has addressed all these issues in 11 chapters.

WHY INCORPORATION OF SENSING ELEMENTS IN CHIPLESS RFID TAGS—THE HYPOTHESIS OF THE BOOK?

While successes are achieved in very low-cost multibit chipless tag design, there are pressing needs to extend the functionality for real-time wireless sensing and monitoring of physical parameters such as temperature, relative humidity, pressure or impact, moisture content, sensing of noxious gases, light intensity, and location of objects [13–16]. In these pursuits, various sensing materials that are compatible with the printable RF/microwave electronics are also investigated. Various smart materials that are identified for low-cost chipless RFID sensor fabrication are (i) ionic plastic crystals, whose ionic conductivity changes due to organic molecule defects and the movement of crystals; (ii) conductive polymers (PEDOTs), whose conductivity increases with frequency; (iii) composite/conjugate polymer, mixed with conductive and nonconductive polymers [17]; and (iv) nanostructured metal oxides that exhibit multifunctional properties and are very susceptible to external environmental changes, such as pressure, temperature, and electric fields [18]. Implementation of these smart materials in fully printable multibit chipless RFID tags brings many new innovations in areas such as new chipless RFID tag design, metamaterial-based high-Q resonator design for sensing purposes, microwave and mm-wave frequency characterization of smart materials, fabrication of integrated chipless RFID sensors, and finally evaluations of such sensing devices in various ambient environments. The book aims to address all these issues mentioned above to make the chipless RFID sensors a viable commercial product for mass deployment. The book covers all these materials in five sections: (i) Introduction to chipless RFID sensors; (ii) RFID sensors design; (iii) smart materials; (iv) fabrication, integration, and testing; and finally (v) applications. The book presents many new designs, concepts, and results in the new field. The authors believe the book will create a significant impact in the research community.

OVERALL OBJECTIVE

In recent decades, RFID has been revolutionizing supply chain management, security, and access controls by tagging items and personnel. The mandate of tagging manufactured items by vendors of retail giant Walmart has accelerated the impact of using RFID [19]. However, RFID has not become a low-cost item tagging device like optical barcodes due to its high cost per tag. Mass deployment of RFID technology will only be possible if the tag is made chipless and fully printable like the barcode. There are a few books on conventional chipped tags in the market. A couple of books on chipless RID tags and readers have been published by the author's group in recent years.

Adding sensing capabilities with the chipless RFID tags will open up many new application areas such as agriculture, construction, health care, energy sectors, retails, public transportations, logistics, and supply chain management.

No book on chipless RFID sensors has been published yet. This will be the first effort to publish a book in the niche area of the chipless RFID sensors based on the outcomes of fundamental research conducted by the author's research group from 2009. Once the chipless RFID tag sensors are made fully printable similar to the optical barcode, it will revolutionize the mass market of low-cost and perishable item tagging and sensing.

REFERENCES

1. P. Harrop and R. Das. Printed and Chipless RFID Forecasts, Technologies & Players 2011–2021 [Online]. Available: http://www.idtechex.com/research/reports/printed-and-chipless-rfid-forecasts-technologies-and-players-2011-2021-000254.asp.
2. I. Jalaly and I. D. Robertson, “RF barcodes using multiple frequency bands,” in Microwave Symposium Digest, 2005 IEEE MTT-S International, 2005, p. 4.
3. S. Shrestha, J. Vemagiri, M. Agarwal, and K. Varahramyan, “Transmission line reflection and delay-based ID generation scheme for RFID and other applications,” International Journal of Radio Frequency Identification Technology and Applications, vol. 1, pp. 401–416, 2007.
4. S. Mukherjee, “System for identifying radio-frequency identification devices,” US20070046433.
5. J. McVay, A. Hoorfar, and N. Engheta, “Theory and experiments on Peano and Hilbert curve RFID tags”, Proceedings of SPIE, 6248, Wireless Sensing and Processing, 624808, doi: 10.1117/12.666911, 2006.
6. S. Preradovic, N. C. Karmakar, and I. Balbin, “RFID Transponders,” IEEE Microwave Magazine, vol. 9, pp. 90–103, 2008.
7. R. Das and P. Harrop. Chip-less RFID Forecasts, Technologies & Players 2006–2016 [Online]. Available: http://www.idtechex.com/products/en/view.asp?productcategoryid=96.
8. S. Preradovic, “Chipless RFID System for Barcode Replacement,” Doctor of Philosophy, Department of Electrical and Computer Systems Engineering, Monash University, 2009.
9. S. Preradovic and N. C. Karmakar, “Chipless RFID: bar code of the future,” IEEE Microwave Magazine, vol. 11, pp. 87–97, 2010.
10. S. Preradovic, I. Balbin, N. C. Karmakar, and G. F. Swiegers, “Multiresonator-based chipless RFID system for low-cost item tracking,” IEEE Transactions on Microwave Theory and Techniques, vol. 57, pp. 1411–1419, 2009.
11. M. A. Islam and N. Karmakar, “Compact printable chipless RFID system using polarization diversity,” Monash University, 2011.
12. N. C. Karmakar, S. M. Roy, and M. S. Ikram, “Development of smart antenna for RFID reader,” in RFID, 2008 IEEE International Conference on, 2008, pp. 65–73.
13. E. M. Amin and N. Karmakar, “Development of a chipless RFID temperature sensor using cascaded spiral resonators,” presented at the IEEE SENSORs 2011, 2011.
14. E. M. Amin, N. Karmakar, and S. Preradovic, “Towards an intelligent EM barcode,” in Electrical & Computer Engineering (ICECE), 2012 7th International Conference on, 2012, pp. 826–829.
15. E. M. Amin and N. Karmakar, “Partial discharge monitoring of high voltage equipment using chipless RFID sensor,” presented at the Asia-Pacific Microwave Conference, Melbourne, Australia, 2011.
16. E. M. Amin, S. Bhuiyan, N. Karmakar, and B. Winther-Jensen, “A novel EM barcode for humidity sensing,” in RFID (RFID), 2013 IEEE International Conference on, 2013, pp. 82–87.
17. J. R. Terje and A. Skotheim, Conjugated Polymers: Processing and Applications, 3rd ed: CRC Press, 2007, p. 207.
18. J. Xia, C. Sui, H. Wang, T. Xu, B. Yan, and Y. Liu, “Optical temperature sensor based on ZnO thin film's temperature-dependent optical properties,” Review of Scientific Instruments, vol. 82, pp. 084901–3, 2011.
19. M. Roberti. (2005). Wal-Mart Begins RFID Process Changes. Available: http://www.rfidjournal.com/article/view/1385.