Professor Ferran Martín (PhD, IEEE Fellow), Paris Vélez (PhD, Senior Member IEEE), Jonathan Muñoz-Enano (Graduate Student Member IEEE), and Lijuan Su (PhD, Member IEEE) are researchers at CIMITEC, a Research and Technology-Transfer Centre (headed by Ferran Martín) affiliated to the Departament d’Enginyeria Electrònica at the Universitat Autònoma de Barcelona (UAB), in Spain. Their activity in recent years has been mainly devoted to the design and applications of planar microwave sensors. They have generated dozens of journal papers and conference contributions related to the topic, published in the top international journals and conferences in the field of sensors and microwave technologies.

• PrefaceAcknowledgments1 Introduction to Planar Microwave Sensors1.1 Sensor performance indicators, classification criteria, and general overview of sensing technologies1.1.1 Performance indicators1.1.2 Sensors’ classification criteria1.1.3 Sensing technologies1.1.3.1 Optical sensors1.1.3.2 Magnetic sensors1.1.3.3 Acoustic sensors1.1.3.4 Mechanical sensors1.1.3.5 Electric sensors1.2 Microwave sensors1.2.1 Remote sensing: RADARs and radiometers1.2.2 Sensors for in situ measurement of physical parameters and material properties: non-remote sensors1.2.2.1 Classification of non-remote microwave sensors1.2.2.2 Resonant cavity sensors1.2.2.3 The Nicolson-Ross-Weir (NRW) method1.2.2.4 Coaxial probe sensors1.2.2.5 Planar sensors1.3 Classification of planar microwave sensors1.3.1 Contact and contactless sensors1.3.2 Wired and wireless sensors1.3.3 Single-ended and differential-mode sensors1.3.4 Resonant and non-resonant sensors1.3.5 Reflective-mode and transmission-mode sensors1.3.6 Sensor classification by frequency of operation1.3.7 Sensor classification by application1.3.8 Sensor classification by working principle1.3.8.1 Frequency-variation sensors1.3.8.2 Phase-variation sensors1.3.8.3 Coupling-modulation sensors1.3.8.4 Frequency-splitting sensors1.3.8.5 Differential-mode sensors1.3.8.6 RFID sensors1.4 Comparison of planar microwave sensors with other sensing technologiesReferences2 Frequency-Variation Sensors2.1 General working principle of frequency-variation sensors2.2 Transmission-line resonant sensors2.2.1 Planar resonant elements for sensing2.2.1.1 Semi-lumped metallic resonators2.2.1.2 Semi-lumped slotted resonators2.2.2 Sensitivity analysis2.2.3 Sensors for dielectric characterization2.2.3.1 CSRR-based microstrip sensor2.2.3.2 DB-DGS-based microstrip sensor2.2.4 Measuring material and liquid composition2.2.5 Displacement sensors2.2.6 Sensor arrays for biomedical analysis2.2.7 Multi-frequency sensing for selective determination of material composition2.3 Other frequency-variation resonant sensors2.3.1 One-port reflective-mode submersible sensors2.3.2 Antenna-based frequency-variation resonant sensors2.4 Advantages and drawbacks of frequency-variation sensorsReferences3 Phase-Variation Sensors3.1 General working principle of phase-variation sensors3.2 Transmission-line phase-variation sensors3.2.1 Transmission-mode sensors3.2.1.1 Transmission-mode four-port differential sensors3.2.1.1.1 Sensor structure and analysis3.2.1.1.2 Sensor implementation and application to dielectric characterization and comparators3.2.1.2 Two-port sensors based on differential-mode to common-mode conversion detectors and sensitivity enhancement3.2.1.2.1 Differential-mode to common-mode conversion detector3.2.1.2.2 Analysis and sensitivity optimization3.2.1.2.3 Sensor design3.2.1.2.4 Comparator functionality3.2.1.2.5 Dielectric constant measurements3.2.1.2.6 Microfluidic sensor. Solute concentration measurements3.2.2 Reflective-mode sensors3.2.2.1 Sensitivity enhancement by means of step-impedance open-ended lines3.2.2.2 Highly-sensitive dielectric constant sensors3.2.2.3 Displacement sensors3.2.2.4 Reflective-mode differential sensors3.3 Resonant-type phase-variation sensors3.3.1 Reflective-mode sensors based on resonant sensing elements3.3.2 Angular displacement sensors3.3.2.1 Cross-polarization in split ring resonator (SRRs) and complementary SRR (CSRR) loaded lines3.3.2.2 Slot-line/SRR configuration3.3.2.3 Microstrip-line/CSRR configuration3.4 Phase-variation sensors based on artificial transmission lines3.4.1 Sensors based on slow-wave transmission lines3.4.1.1 Sensing through the host line3.4.1.2 Sensing through the patch capacitors3.4.2 Sensors based on composite right/left handed (CRLH) lines3.4.3 Sensors based on electro-inductive wave (EIW) transmission lines3.5 Advantages and drawbacks of phase-variation sensorsReferences4 Coupling-Modulation Sensors4.1 Symmetry properties in transmission lines loaded with single symmetric resonators4.2 Working principle of coupling-modulation sensors4.3 Displacement and velocity coupling-modulation sensors4.3.1 One-dimensional and two-dimensional linear displacement sensors4.3.2 Angular displacement and velocity sensors4.3.2.1 Axial configuration and Analysis4.3.2.1.1 Coplanar waveguide (CPW) stator4.3.2.1.2 Microstrip stator4.3.2.2 Edge configuration. Electromagnetic rotary encoders4.3.2.2.1 CPW stator4.3.2.2.2 Microstrip stator4.3.2.2.3 Resolution and accuracy4.3.3 Electromagnetic linear encoders4.3.3.1 Strategy for synchronous reading. Quasi-absolute encoders4.3.3.2 Application to motion control4.4 Coupling-modulation sensors for dielectric characterization4.5 Advantages and drawbacks of coupling-modulation sensorsReferences5 Frequency-Splitting Sensors5.1 Working principle of frequency-splitting sensors5.2 Transmission lines loaded with pairs of coupled resonators5.2.1 CPW transmission lines loaded with a pair of coupled SRRs5.2.2 Microstrip transmission lines loaded with a pair of coupled CSRRs5.2.3 Microstrip transmission lines loaded with a pair of coupled SIRs5.3 Frequency-splitting sensors based on cascaded resonators5.4 Frequency-splitting sensors based on the splitter/combiner configuration5.4.1 CSRR-based splitter/combiner sensor: analysis and application to dielectric characterization of solids5.4.2 Microfluidic SRR-based splitter/combiner frequency-splitting sensor5.5 Other approaches for coupling cancellation in frequency-splitting sensors5.5.1 MLC-based frequency-splitting sensor5.5.2 SRR-based frequency-splitting sensor implemented in microstrip technology5.6 Other frequency-splitting sensors5.6.1 Frequency-splitting sensors operating in bandpass configuration5.6.2 Frequency-splitting sensors for two-dimensional alignment and displacement  measurements5.7 Advantages and drawbacks of frequency-splitting sensorsReferences6 Differential-Mode Sensors6.1 The differential-mode sensor concept6.2 Differential sensors based on the measurement of the cross-mode transmission coefficient6.2.1 Working principle6.2.2 Examples and applications6.2.2.1 Microfluidic sensor based on open complementary split ring resonators (OCSRRs) and application to complex permittivity and electrolyte concentration measurements in liquids6.2.2.2 Microfluidic sensor based on SRRs and application to electrolyte concentration measurements in aqueous solutions6.2.2.3 Microfluidic sensor based on DB-DGS resonators and application to electrolyte concentration measurements in aqueous solutions6.2.2.4 Prototype for measuring electrolyte content in urine samples6.3 Reflective-mode differential sensors based on the measurement of the cross-mode reflection coefficient6.4 Other differential sensors6.5 Advantages and drawbacks of differential-mode sensorsReferences7 RFID Sensors for IoT Applications7.1 Fundamentals of RFID7.2 Strategies for RFID sensing7.2.1 Chip-based RFID sensors7.2.1.1 Electronic sensors7.2.1.2 Electromagnetic sensors7.2.2 Chipless-RFID sensors7.2.2.1 Time-domain sensors7.2.2.2 Frequency-domain sensors7.3 Materials and fabrication techniques7.4 Applications7.4.1 Healthcare, wearables and implants7.4.2 Food, smart packaging and agriculture7.4.3 Civil engineering: structural health monitoring (SHM)7.4.4 Automotive industry, smart cities and space7.5 Commercial solutions, limitations and future prospectsReferences8 Comparative Analysis and Concluding RemarksAcronymsIndex

Professor Ferran Martín (PhD, IEEE Fellow), Paris Vélez (PhD, Senior Member IEEE), Jonathan Muñoz-Enano (Graduate Student Member IEEE), and Lijuan Su (PhD, Member IEEE) are researchers at CIMITEC, a Research and Technology-Transfer Centre (headed by Ferran Martín) affiliated to the Departament d’Enginyeria Electrònica at the Universitat Autònoma de Barcelona (UAB), in Spain. Their activity in recent years has been mainly devoted to the design and applications of planar microwave sensors. They have generated dozens of journal papers and conference contributions related to the topic, published in the top international journals and conferences in the field of sensors and microwave technologies.

• PrefaceAcknowledgments1 Introduction to Planar Microwave Sensors1.1 Sensor performance indicators, classification criteria, and general overview of sensing technologies1.1.1 Performance indicators1.1.2 Sensors’ classification criteria1.1.3 Sensing technologies1.1.3.1 Optical sensors1.1.3.2 Magnetic sensors1.1.3.3 Acoustic sensors1.1.3.4 Mechanical sensors1.1.3.5 Electric sensors1.2 Microwave sensors1.2.1 Remote sensing: RADARs and radiometers1.2.2 Sensors for in situ measurement of physical parameters and material properties: non-remote sensors1.2.2.1 Classification of non-remote microwave sensors1.2.2.2 Resonant cavity sensors1.2.2.3 The Nicolson-Ross-Weir (NRW) method1.2.2.4 Coaxial probe sensors1.2.2.5 Planar sensors1.3 Classification of planar microwave sensors1.3.1 Contact and contactless sensors1.3.2 Wired and wireless sensors1.3.3 Single-ended and differential-mode sensors1.3.4 Resonant and non-resonant sensors1.3.5 Reflective-mode and transmission-mode sensors1.3.6 Sensor classification by frequency of operation1.3.7 Sensor classification by application1.3.8 Sensor classification by working principle1.3.8.1 Frequency-variation sensors1.3.8.2 Phase-variation sensors1.3.8.3 Coupling-modulation sensors1.3.8.4 Frequency-splitting sensors1.3.8.5 Differential-mode sensors1.3.8.6 RFID sensors1.4 Comparison of planar microwave sensors with other sensing technologiesReferences2 Frequency-Variation Sensors2.1 General working principle of frequency-variation sensors2.2 Transmission-line resonant sensors2.2.1 Planar resonant elements for sensing2.2.1.1 Semi-lumped metallic resonators2.2.1.2 Semi-lumped slotted resonators2.2.2 Sensitivity analysis2.2.3 Sensors for dielectric characterization2.2.3.1 CSRR-based microstrip sensor2.2.3.2 DB-DGS-based microstrip sensor2.2.4 Measuring material and liquid composition2.2.5 Displacement sensors2.2.6 Sensor arrays for biomedical analysis2.2.7 Multi-frequency sensing for selective determination of material composition2.3 Other frequency-variation resonant sensors2.3.1 One-port reflective-mode submersible sensors2.3.2 Antenna-based frequency-variation resonant sensors2.4 Advantages and drawbacks of frequency-variation sensorsReferences3 Phase-Variation Sensors3.1 General working principle of phase-variation sensors3.2 Transmission-line phase-variation sensors3.2.1 Transmission-mode sensors3.2.1.1 Transmission-mode four-port differential sensors3.2.1.1.1 Sensor structure and analysis3.2.1.1.2 Sensor implementation and application to dielectric characterization and comparators3.2.1.2 Two-port sensors based on differential-mode to common-mode conversion detectors and sensitivity enhancement3.2.1.2.1 Differential-mode to common-mode conversion detector3.2.1.2.2 Analysis and sensitivity optimization3.2.1.2.3 Sensor design3.2.1.2.4 Comparator functionality3.2.1.2.5 Dielectric constant measurements3.2.1.2.6 Microfluidic sensor. Solute concentration measurements3.2.2 Reflective-mode sensors3.2.2.1 Sensitivity enhancement by means of step-impedance open-ended lines3.2.2.2 Highly-sensitive dielectric constant sensors3.2.2.3 Displacement sensors3.2.2.4 Reflective-mode differential sensors3.3 Resonant-type phase-variation sensors3.3.1 Reflective-mode sensors based on resonant sensing elements3.3.2 Angular displacement sensors3.3.2.1 Cross-polarization in split ring resonator (SRRs) and complementary SRR (CSRR) loaded lines3.3.2.2 Slot-line/SRR configuration3.3.2.3 Microstrip-line/CSRR configuration3.4 Phase-variation sensors based on artificial transmission lines3.4.1 Sensors based on slow-wave transmission lines3.4.1.1 Sensing through the host line3.4.1.2 Sensing through the patch capacitors3.4.2 Sensors based on composite right/left handed (CRLH) lines3.4.3 Sensors based on electro-inductive wave (EIW) transmission lines3.5 Advantages and drawbacks of phase-variation sensorsReferences4 Coupling-Modulation Sensors4.1 Symmetry properties in transmission lines loaded with single symmetric resonators4.2 Working principle of coupling-modulation sensors4.3 Displacement and velocity coupling-modulation sensors4.3.1 One-dimensional and two-dimensional linear displacement sensors4.3.2 Angular displacement and velocity sensors4.3.2.1 Axial configuration and Analysis4.3.2.1.1 Coplanar waveguide (CPW) stator4.3.2.1.2 Microstrip stator4.3.2.2 Edge configuration. Electromagnetic rotary encoders4.3.2.2.1 CPW stator4.3.2.2.2 Microstrip stator4.3.2.2.3 Resolution and accuracy4.3.3 Electromagnetic linear encoders4.3.3.1 Strategy for synchronous reading. Quasi-absolute encoders4.3.3.2 Application to motion control4.4 Coupling-modulation sensors for dielectric characterization4.5 Advantages and drawbacks of coupling-modulation sensorsReferences5 Frequency-Splitting Sensors5.1 Working principle of frequency-splitting sensors5.2 Transmission lines loaded with pairs of coupled resonators5.2.1 CPW transmission lines loaded with a pair of coupled SRRs5.2.2 Microstrip transmission lines loaded with a pair of coupled CSRRs5.2.3 Microstrip transmission lines loaded with a pair of coupled SIRs5.3 Frequency-splitting sensors based on cascaded resonators5.4 Frequency-splitting sensors based on the splitter/combiner configuration5.4.1 CSRR-based splitter/combiner sensor: analysis and application to dielectric characterization of solids5.4.2 Microfluidic SRR-based splitter/combiner frequency-splitting sensor5.5 Other approaches for coupling cancellation in frequency-splitting sensors5.5.1 MLC-based frequency-splitting sensor5.5.2 SRR-based frequency-splitting sensor implemented in microstrip technology5.6 Other frequency-splitting sensors5.6.1 Frequency-splitting sensors operating in bandpass configuration5.6.2 Frequency-splitting sensors for two-dimensional alignment and displacement  measurements5.7 Advantages and drawbacks of frequency-splitting sensorsReferences6 Differential-Mode Sensors6.1 The differential-mode sensor concept6.2 Differential sensors based on the measurement of the cross-mode transmission coefficient6.2.1 Working principle6.2.2 Examples and applications6.2.2.1 Microfluidic sensor based on open complementary split ring resonators (OCSRRs) and application to complex permittivity and electrolyte concentration measurements in liquids6.2.2.2 Microfluidic sensor based on SRRs and application to electrolyte concentration measurements in aqueous solutions6.2.2.3 Microfluidic sensor based on DB-DGS resonators and application to electrolyte concentration measurements in aqueous solutions6.2.2.4 Prototype for measuring electrolyte content in urine samples6.3 Reflective-mode differential sensors based on the measurement of the cross-mode reflection coefficient6.4 Other differential sensors6.5 Advantages and drawbacks of differential-mode sensorsReferences7 RFID Sensors for IoT Applications7.1 Fundamentals of RFID7.2 Strategies for RFID sensing7.2.1 Chip-based RFID sensors7.2.1.1 Electronic sensors7.2.1.2 Electromagnetic sensors7.2.2 Chipless-RFID sensors7.2.2.1 Time-domain sensors7.2.2.2 Frequency-domain sensors7.3 Materials and fabrication techniques7.4 Applications7.4.1 Healthcare, wearables and implants7.4.2 Food, smart packaging and agriculture7.4.3 Civil engineering: structural health monitoring (SHM)7.4.4 Automotive industry, smart cities and space7.5 Commercial solutions, limitations and future prospectsReferences8 Comparative Analysis and Concluding RemarksAcronymsIndex

Professor Ferran Martín (PhD, IEEE Fellow), Paris Vélez (PhD, Senior Member IEEE), Jonathan Muñoz-Enano (Graduate Student Member IEEE), and Lijuan Su (PhD, Member IEEE) are researchers at CIMITEC, a Research and Technology-Transfer Centre (headed by Ferran Martín) affiliated to the Departament d’Enginyeria Electrònica at the Universitat Autònoma de Barcelona (UAB), in Spain. Their activity in recent years has been mainly devoted to the design and applications of planar microwave sensors. They have generated dozens of journal papers and conference contributions related to the topic, published in the top international journals and conferences in the field of sensors and microwave technologies.

• PrefaceAcknowledgments1 Introduction to Planar Microwave Sensors1.1 Sensor performance indicators, classification criteria, and general overview of sensing technologies1.1.1 Performance indicators1.1.2 Sensors’ classification criteria1.1.3 Sensing technologies1.1.3.1 Optical sensors1.1.3.2 Magnetic sensors1.1.3.3 Acoustic sensors1.1.3.4 Mechanical sensors1.1.3.5 Electric sensors1.2 Microwave sensors1.2.1 Remote sensing: RADARs and radiometers1.2.2 Sensors for in situ measurement of physical parameters and material properties: non-remote sensors1.2.2.1 Classification of non-remote microwave sensors1.2.2.2 Resonant cavity sensors1.2.2.3 The Nicolson-Ross-Weir (NRW) method1.2.2.4 Coaxial probe sensors1.2.2.5 Planar sensors1.3 Classification of planar microwave sensors1.3.1 Contact and contactless sensors1.3.2 Wired and wireless sensors1.3.3 Single-ended and differential-mode sensors1.3.4 Resonant and non-resonant sensors1.3.5 Reflective-mode and transmission-mode sensors1.3.6 Sensor classification by frequency of operation1.3.7 Sensor classification by application1.3.8 Sensor classification by working principle1.3.8.1 Frequency-variation sensors1.3.8.2 Phase-variation sensors1.3.8.3 Coupling-modulation sensors1.3.8.4 Frequency-splitting sensors1.3.8.5 Differential-mode sensors1.3.8.6 RFID sensors1.4 Comparison of planar microwave sensors with other sensing technologiesReferences2 Frequency-Variation Sensors2.1 General working principle of frequency-variation sensors2.2 Transmission-line resonant sensors2.2.1 Planar resonant elements for sensing2.2.1.1 Semi-lumped metallic resonators2.2.1.2 Semi-lumped slotted resonators2.2.2 Sensitivity analysis2.2.3 Sensors for dielectric characterization2.2.3.1 CSRR-based microstrip sensor2.2.3.2 DB-DGS-based microstrip sensor2.2.4 Measuring material and liquid composition2.2.5 Displacement sensors2.2.6 Sensor arrays for biomedical analysis2.2.7 Multi-frequency sensing for selective determination of material composition2.3 Other frequency-variation resonant sensors2.3.1 One-port reflective-mode submersible sensors2.3.2 Antenna-based frequency-variation resonant sensors2.4 Advantages and drawbacks of frequency-variation sensorsReferences3 Phase-Variation Sensors3.1 General working principle of phase-variation sensors3.2 Transmission-line phase-variation sensors3.2.1 Transmission-mode sensors3.2.1.1 Transmission-mode four-port differential sensors3.2.1.1.1 Sensor structure and analysis3.2.1.1.2 Sensor implementation and application to dielectric characterization and comparators3.2.1.2 Two-port sensors based on differential-mode to common-mode conversion detectors and sensitivity enhancement3.2.1.2.1 Differential-mode to common-mode conversion detector3.2.1.2.2 Analysis and sensitivity optimization3.2.1.2.3 Sensor design3.2.1.2.4 Comparator functionality3.2.1.2.5 Dielectric constant measurements3.2.1.2.6 Microfluidic sensor. Solute concentration measurements3.2.2 Reflective-mode sensors3.2.2.1 Sensitivity enhancement by means of step-impedance open-ended lines3.2.2.2 Highly-sensitive dielectric constant sensors3.2.2.3 Displacement sensors3.2.2.4 Reflective-mode differential sensors3.3 Resonant-type phase-variation sensors3.3.1 Reflective-mode sensors based on resonant sensing elements3.3.2 Angular displacement sensors3.3.2.1 Cross-polarization in split ring resonator (SRRs) and complementary SRR (CSRR) loaded lines3.3.2.2 Slot-line/SRR configuration3.3.2.3 Microstrip-line/CSRR configuration3.4 Phase-variation sensors based on artificial transmission lines3.4.1 Sensors based on slow-wave transmission lines3.4.1.1 Sensing through the host line3.4.1.2 Sensing through the patch capacitors3.4.2 Sensors based on composite right/left handed (CRLH) lines3.4.3 Sensors based on electro-inductive wave (EIW) transmission lines3.5 Advantages and drawbacks of phase-variation sensorsReferences4 Coupling-Modulation Sensors4.1 Symmetry properties in transmission lines loaded with single symmetric resonators4.2 Working principle of coupling-modulation sensors4.3 Displacement and velocity coupling-modulation sensors4.3.1 One-dimensional and two-dimensional linear displacement sensors4.3.2 Angular displacement and velocity sensors4.3.2.1 Axial configuration and Analysis4.3.2.1.1 Coplanar waveguide (CPW) stator4.3.2.1.2 Microstrip stator4.3.2.2 Edge configuration. Electromagnetic rotary encoders4.3.2.2.1 CPW stator4.3.2.2.2 Microstrip stator4.3.2.2.3 Resolution and accuracy4.3.3 Electromagnetic linear encoders4.3.3.1 Strategy for synchronous reading. Quasi-absolute encoders4.3.3.2 Application to motion control4.4 Coupling-modulation sensors for dielectric characterization4.5 Advantages and drawbacks of coupling-modulation sensorsReferences5 Frequency-Splitting Sensors5.1 Working principle of frequency-splitting sensors5.2 Transmission lines loaded with pairs of coupled resonators5.2.1 CPW transmission lines loaded with a pair of coupled SRRs5.2.2 Microstrip transmission lines loaded with a pair of coupled CSRRs5.2.3 Microstrip transmission lines loaded with a pair of coupled SIRs5.3 Frequency-splitting sensors based on cascaded resonators5.4 Frequency-splitting sensors based on the splitter/combiner configuration5.4.1 CSRR-based splitter/combiner sensor: analysis and application to dielectric characterization of solids5.4.2 Microfluidic SRR-based splitter/combiner frequency-splitting sensor5.5 Other approaches for coupling cancellation in frequency-splitting sensors5.5.1 MLC-based frequency-splitting sensor5.5.2 SRR-based frequency-splitting sensor implemented in microstrip technology5.6 Other frequency-splitting sensors5.6.1 Frequency-splitting sensors operating in bandpass configuration5.6.2 Frequency-splitting sensors for two-dimensional alignment and displacement  measurements5.7 Advantages and drawbacks of frequency-splitting sensorsReferences6 Differential-Mode Sensors6.1 The differential-mode sensor concept6.2 Differential sensors based on the measurement of the cross-mode transmission coefficient6.2.1 Working principle6.2.2 Examples and applications6.2.2.1 Microfluidic sensor based on open complementary split ring resonators (OCSRRs) and application to complex permittivity and electrolyte concentration measurements in liquids6.2.2.2 Microfluidic sensor based on SRRs and application to electrolyte concentration measurements in aqueous solutions6.2.2.3 Microfluidic sensor based on DB-DGS resonators and application to electrolyte concentration measurements in aqueous solutions6.2.2.4 Prototype for measuring electrolyte content in urine samples6.3 Reflective-mode differential sensors based on the measurement of the cross-mode reflection coefficient6.4 Other differential sensors6.5 Advantages and drawbacks of differential-mode sensorsReferences7 RFID Sensors for IoT Applications7.1 Fundamentals of RFID7.2 Strategies for RFID sensing7.2.1 Chip-based RFID sensors7.2.1.1 Electronic sensors7.2.1.2 Electromagnetic sensors7.2.2 Chipless-RFID sensors7.2.2.1 Time-domain sensors7.2.2.2 Frequency-domain sensors7.3 Materials and fabrication techniques7.4 Applications7.4.1 Healthcare, wearables and implants7.4.2 Food, smart packaging and agriculture7.4.3 Civil engineering: structural health monitoring (SHM)7.4.4 Automotive industry, smart cities and space7.5 Commercial solutions, limitations and future prospectsReferences8 Comparative Analysis and Concluding RemarksAcronymsIndex