Chi-yen Shen - Academia.edu (original) (raw)

Papers by Chi-yen Shen

Research paper thumbnail of Room-Temperature NH3 Gas Surface Acoustic Wave (SAW) Sensors Based on Graphene/PPy Composite Films Decorated by Au Nanoparticles with ppb Detection Ability

Polymers

Exhaled human breath analysis has great potential for the diagnosis of diseases in non-invasive w... more Exhaled human breath analysis has great potential for the diagnosis of diseases in non-invasive way. The 13C-Urea breath test for the diagnosis of Helicobacter pylori infection indicates the ammonia concentration of 50–400 ppb in the breath. This work successfully developed a surface acoustic wave (SAW) resonator based on graphene/polypyrrole composite films decorated by gold nanoparticles (AuNPs–G/PPy) with sensitivity and selectivity to detect ammonia in parts-per-billion concentrations, which is promising for the accurate diagnosis of H. pylori infection. XRD, EDS, and SEM characterized the AuNPs–G/PPy nanocomposites, providing comprehensive insights into their structural, compositional, and morphological properties. The gas-sensing capabilities of the fabricated SAW sensors were extensively investigated, focusing on their response to NH3 gas at ambient temperature. The concentration of ammonia gas was effectively quantified by monitoring the frequency shift of the SAW device. No...

Research paper thumbnail of Propagation Characteristics of Surface Acoustic Wave and Properties of Gas Sensors on Quartz

Springer eBooks, 2010

The simulation of wave propagation in periodic piezoelectric surface acoustic wave (SAW) structur... more The simulation of wave propagation in periodic piezoelectric surface acoustic wave (SAW) structures was reported in this study. Firstly, space harmonics method (SHM) was used to analyze Rayleigh SAW propagation under a periodic Al grating. The results of SAW ...

Research paper thumbnail of Piezoelectric sensor for sensitive determination of metal ions based on the phosphate-modified dendrimer

Smart Materials and Structures, Jul 18, 2016

Heavy metal ions arising from human activities are retained strongly in water; therefore public w... more Heavy metal ions arising from human activities are retained strongly in water; therefore public water supplies must be monitored regularly to ensure the timely detection of potential problems. A phosphate-modified dendrimer film was investigated on a quartz crystal microbalance (QCM) for sensing metal ions in water at room temperature in this study. The chemical structures and sensing properties were characterized by Fourier transform infrared spectroscopy and QCM measurement, respectively. This phosphate-modified dendrimer sensor can directly detect metal ions in aqueous solutions. This novel sensor was evaluated for its capacity to sense various metal ions. The sensor exhibited a higher sensitivity level and shorter response time to copper(II) ions than other sensors. The linear detection range of the prepared QCM based on the phosphate-modified dendrimer was 0.0001 ~ 1 μM Cu(II) ions (R2 = 0.98). The detection properties, including sensitivity, response time, selectivity, reusability, maximum adsorption capacity, and adsorption equilibrium constants, were also investigated.

Research paper thumbnail of The Sensing Properties of L-Glutamic Acid Hydrochloride Coated on Surface Acoustic Wave Ammonia Gas Sensors (Proceedings of The 5Th East Asian Conference on Chemical Sensors: The 33RD Chemical Sensor Symposium)

Proceedings of the Chemical Sensor Symposium, Dec 1, 2001

Research paper thumbnail of An Evolutionary Method of Neural Network in System Identification

International journal of intelligent information systems, 2016

Research paper thumbnail of Piezoelectric microsensor for selective detection of low concentrations of ammonia

Solid-state Electronics, Dec 1, 2021

Research paper thumbnail of MOESM7 of Origination and selection of ABCDE and AGL6 subfamily MADS-box genes in gymnosperms and angiosperms

Additional file 7. The AGL6/AGL13 genes in Bayesian tree and the Bayesian posterior probability v... more Additional file 7. The AGL6/AGL13 genes in Bayesian tree and the Bayesian posterior probability values in tree.

Research paper thumbnail of MOESM1 of Origination and selection of ABCDE and AGL6 subfamily MADS-box genes in gymnosperms and angiosperms

Additional file 1. Sequence numbers of 27 plant species.

Research paper thumbnail of Sensitive and Label-free Detection of Cartilage Oligomeric Matrix Protein on Quartz Crystal Microbalance

Osteoarthritis (OA), the most common joint disease, is due to articular cartilage degradation, le... more Osteoarthritis (OA), the most common joint disease, is due to articular cartilage degradation, leading to joint destruction. The most common methods for diagnosing OA are done using radiographs and enzyme-linked immunosorbent assay (ELISA) method which are specific but require specialized laboratory facilities and highly trained personal. To avoid invasive methods for diagnosis, the current study describes a novel non-invasive detection method for osteoarthritis urine biomarkers. A highly selective and specific monoclonal antibodies, cartilage oligomeric matrix protein (COMP), were used to immobilize on a quartz crystal microbalance (QCM) sensor. The developed QCM sensor for COMP detection showed good sensitivity, linearity, specificity and reliability.

Research paper thumbnail of Piezoelectric sensor for sensitive determination of metal ions based on the phosphate-modified dendrimer

Smart Materials and Structures, 2016

Heavy metal ions arising from human activities are retained strongly in water; therefore public w... more Heavy metal ions arising from human activities are retained strongly in water; therefore public water supplies must be monitored regularly to ensure the timely detection of potential problems. A phosphate-modified dendrimer film was investigated on a quartz crystal microbalance (QCM) for sensing metal ions in water at room temperature in this study. The chemical structures and sensing properties were characterized by Fourier transform infrared spectroscopy and QCM measurement, respectively. This phosphate-modified dendrimer sensor can directly detect metal ions in aqueous solutions. This novel sensor was evaluated for its capacity to sense various metal ions. The sensor exhibited a higher sensitivity level and shorter response time to copper(II) ions than other sensors. The linear detection range of the prepared QCM based on the phosphate-modified dendrimer was 0.0001 ~ 1 μM Cu(II) ions (R2 = 0.98). The detection properties, including sensitivity, response time, selectivity, reusability, maximum adsorption capacity, and adsorption equilibrium constants, were also investigated.

Research paper thumbnail of ShearHorizontal Surface Acoustic WaveSensors BasedonPolyaniline forAmmoniaGasSensing

Research paper thumbnail of MOESM2 of Origination and selection of ABCDE and AGL6 subfamily MADS-box genes in gymnosperms and angiosperms

Additional file 2. Txt files of 27 species and 381 sequences.

Research paper thumbnail of Prediction of Substance Concentration in Simulated Moving Bed by Ultraviolet Sensor and Neural Network

Sensors and Materials, 2020

Research paper thumbnail of Nitric oxide sensing properties of a surface acoustic wave sensor with copper-ion-doped polyaniline/tungsten oxide nanocomposite film

Sensors and Actuators B: Chemical, 2017

Research paper thumbnail of Synthesis and anti-fungal effect of silver nanoparticles-chitosan composite particles

International journal of nanomedicine, 2015

Silver nanoparticles have been used in various fields, and several synthesis processes have been ... more Silver nanoparticles have been used in various fields, and several synthesis processes have been developed. The stability and dispersion of the synthesized nanoparticles is vital. The present article describes a novel approach for one-step synthesis of silver nanoparticles-embedded chitosan particles. The proposed approach was applied to simultaneously obtain and stabilize silver nanoparticles in a chitosan polymer matrix in-situ. The diameter of the synthesized chitosan composite particles ranged from 1.7 mm to 2.5 mm, and the embedded silver nanoparticles were measured to be 15±3.3 nm. Further, the analyses of ultraviolet-visible spectroscopy, energy dispersive spectroscopy, and X-ray diffraction were employed to characterize the prepared composites. The results show that the silver nanoparticles were distributed over the surface and interior of the chitosan spheres. The fabricated spheres had macroporous property, and could be used for many applications such as fungicidal agents ...

Research paper thumbnail of A Room-Temperature Surface Acoustic Wave Ammonia Sensor Based on rGO/DPP2T-TT Composite Films

Sensors

Surface acoustic wave (SAW) sensors based on reduced graphene oxide/poly (diketopyrrolopyrrolethi... more Surface acoustic wave (SAW) sensors based on reduced graphene oxide/poly (diketopyrrolopyrrolethiophene-thieno [3,2-b]thiophene-thiophene) (rGO/DPP2T-TT) composite sensing films for the detection of ammonia were investigated at room temperature in this study. The rGO/DPP2T-TT composite films were deposited onto ST-X quartz SAW resonators by a drop-casting method. FESEM, EDS, and XRD characterizations showed that the rGO/DPP2T-TT composite film was successfully synthesized and exhibited numerous wrinkles and a rough structure, which are crucial for gas adsorption. The frequency response to 500–1400 ppb ammonia shown by the prepared SAW sensor coated with rGO/DPP2T-TT composite film increased linearly as the ammonia concentration increased. The sensor based on a rGO/DPP2T-TT composite film exhibited a positive frequency shift of 55 Hz/ppm, and its frequency response to 500 ppb ammonia was 35 Hz. The sensors thus show promising potential in detecting sub-ppm concentration levels of NH3...

Research paper thumbnail of The Optimal Crane Scheduling for Chemical Polishing Process Based on Expert System

International Journal of Modeling and Optimization, 2018

It is well known that the manufacturing process of many industrial products requires the crane li... more It is well known that the manufacturing process of many industrial products requires the crane lifting and delivering. The use of crane can not only reduce the cost of manual handling, but also increase the production's capacity. Thus, how to design an accurate, efficient and optimal crane scheduling becomes a very important issue in the industrial manufacturing process, especially to the electronic industry. This paper presents an optimal crane scheduling and control for the multiple manufacturing processes of electronic surface treatment based on the entire plant design. The expert system with "time-axis" method is used to find the minimum number of cranes needed for the entire plant design. The surface treatment of electronic industry is used as the example for the whole design process. The result shows that the optimal crane scheduling developed can not only have the optimal cranes' control, but also fit the requirement of minimum cycling time of each manufacturing process.

Research paper thumbnail of Identification of Simulated Moving Bed Dynamic System by Neural Network

Sensors and Materials, 2021

This paper presents a study about the possibility of system identification for a simulated moving... more This paper presents a study about the possibility of system identification for a simulated moving bed (SMB), which is an important step for developing a smart SMB automatic control mechanism with a precise control capability. An SMB is a very complex and nonlinear system that is constructed from multiple columns in series and complex valve arrangements. All feed mixtures and solvents and the desorbent flow are controlled by the columns and valve devices at a fixed switching time. Thus, if the operational behavior of an SMB system can be identified in advance, then the precise control of the system can be achieved easily. In this study, the neural network (NN) technique was used to identify an SMB system. From the experimental results shown, an NN was found to be a very effective tool for SMB system identification.

Research paper thumbnail of Sparklan Antenna in Indoor Positioning Application

Sensors and Materials, 2019

In this paper, the study of a Sparklan antenna used for indoor positioning (IP) is presented. The... more In this paper, the study of a Sparklan antenna used for indoor positioning (IP) is presented. The completed sensing hardware infrastructure is composed of six Sparklan AX-106M antennas and one Zigbee module. An indoor area with a size of 64 m 2 in the building of Sue-Te University is used as the experimental field and a database including 704 sensed points with six received signal strength (RSS) signals is firstly constructed as the reference object locations. The RSSs of six antennas are used for object positioning estimation using a fuzzy estimator. To demonstrate the superiority of the developed IP system (IPS), several experiments were conducted. Experimental results show that the positioning performance of the IPS we developed is still accurate even when some antennas are disabled.

Research paper thumbnail of Enhanced Sensitive Surface Acoustic Wave Device Designed for Nitric Oxide Gas Detection

Sensors and Materials, 2019

Surface acoustic wave (SAW) devices equipped with an electrode-width-controlled (EWC)/ single-pha... more Surface acoustic wave (SAW) devices equipped with an electrode-width-controlled (EWC)/ single-phase unidirectional transducer (SPUDT) and fabricated on ST-X quartz were proposed and found to have low insertion loss and single-mode capability. The devices were then used to determine parts-per-billion levels of nitric oxide (NO). A new modified equivalent circuit (EC) model was used to model and analyze the characteristics of SAW devices prior to their fabrication. The small-signal frequency responses (S 21) obtained by simulation and measurement were consistent. A feedback-loop oscillator was used to design SAW-resonatorstabilized oscillators that provided stable oscillation. A SAW oscillator with an EWC/SPUDT structure was used to provide fundamental signals with high output power, induce high harmonic suppression, and realize long-term frequency stability. SAW devices with an EWC/ SPUDT structure were coated with a Cu 2+ /PANI/WO 3-sensitive layer to successfully determine parts-per-billion levels of NO. For a NO concentration of 50 ppb in dry air, the frequency shift in the SAW sensor with the EWC/SPUDT structure is 502 Hz. Moreover, the response and recovery time are 40 and 112 s, respectively. The sensitivity of NO detection for a concentration range of 20-80 ppb is approximately 4.2 Hz/ppb (~3.43 kHz/mg/m 3).

Research paper thumbnail of Room-Temperature NH3 Gas Surface Acoustic Wave (SAW) Sensors Based on Graphene/PPy Composite Films Decorated by Au Nanoparticles with ppb Detection Ability

Polymers

Exhaled human breath analysis has great potential for the diagnosis of diseases in non-invasive w... more Exhaled human breath analysis has great potential for the diagnosis of diseases in non-invasive way. The 13C-Urea breath test for the diagnosis of Helicobacter pylori infection indicates the ammonia concentration of 50–400 ppb in the breath. This work successfully developed a surface acoustic wave (SAW) resonator based on graphene/polypyrrole composite films decorated by gold nanoparticles (AuNPs–G/PPy) with sensitivity and selectivity to detect ammonia in parts-per-billion concentrations, which is promising for the accurate diagnosis of H. pylori infection. XRD, EDS, and SEM characterized the AuNPs–G/PPy nanocomposites, providing comprehensive insights into their structural, compositional, and morphological properties. The gas-sensing capabilities of the fabricated SAW sensors were extensively investigated, focusing on their response to NH3 gas at ambient temperature. The concentration of ammonia gas was effectively quantified by monitoring the frequency shift of the SAW device. No...

Research paper thumbnail of Propagation Characteristics of Surface Acoustic Wave and Properties of Gas Sensors on Quartz

Springer eBooks, 2010

The simulation of wave propagation in periodic piezoelectric surface acoustic wave (SAW) structur... more The simulation of wave propagation in periodic piezoelectric surface acoustic wave (SAW) structures was reported in this study. Firstly, space harmonics method (SHM) was used to analyze Rayleigh SAW propagation under a periodic Al grating. The results of SAW ...

Research paper thumbnail of Piezoelectric sensor for sensitive determination of metal ions based on the phosphate-modified dendrimer

Smart Materials and Structures, Jul 18, 2016

Heavy metal ions arising from human activities are retained strongly in water; therefore public w... more Heavy metal ions arising from human activities are retained strongly in water; therefore public water supplies must be monitored regularly to ensure the timely detection of potential problems. A phosphate-modified dendrimer film was investigated on a quartz crystal microbalance (QCM) for sensing metal ions in water at room temperature in this study. The chemical structures and sensing properties were characterized by Fourier transform infrared spectroscopy and QCM measurement, respectively. This phosphate-modified dendrimer sensor can directly detect metal ions in aqueous solutions. This novel sensor was evaluated for its capacity to sense various metal ions. The sensor exhibited a higher sensitivity level and shorter response time to copper(II) ions than other sensors. The linear detection range of the prepared QCM based on the phosphate-modified dendrimer was 0.0001 ~ 1 μM Cu(II) ions (R2 = 0.98). The detection properties, including sensitivity, response time, selectivity, reusability, maximum adsorption capacity, and adsorption equilibrium constants, were also investigated.

Research paper thumbnail of The Sensing Properties of L-Glutamic Acid Hydrochloride Coated on Surface Acoustic Wave Ammonia Gas Sensors (Proceedings of The 5Th East Asian Conference on Chemical Sensors: The 33RD Chemical Sensor Symposium)

Proceedings of the Chemical Sensor Symposium, Dec 1, 2001

Research paper thumbnail of An Evolutionary Method of Neural Network in System Identification

International journal of intelligent information systems, 2016

Research paper thumbnail of Piezoelectric microsensor for selective detection of low concentrations of ammonia

Solid-state Electronics, Dec 1, 2021

Research paper thumbnail of MOESM7 of Origination and selection of ABCDE and AGL6 subfamily MADS-box genes in gymnosperms and angiosperms

Additional file 7. The AGL6/AGL13 genes in Bayesian tree and the Bayesian posterior probability v... more Additional file 7. The AGL6/AGL13 genes in Bayesian tree and the Bayesian posterior probability values in tree.

Research paper thumbnail of MOESM1 of Origination and selection of ABCDE and AGL6 subfamily MADS-box genes in gymnosperms and angiosperms

Additional file 1. Sequence numbers of 27 plant species.

Research paper thumbnail of Sensitive and Label-free Detection of Cartilage Oligomeric Matrix Protein on Quartz Crystal Microbalance

Osteoarthritis (OA), the most common joint disease, is due to articular cartilage degradation, le... more Osteoarthritis (OA), the most common joint disease, is due to articular cartilage degradation, leading to joint destruction. The most common methods for diagnosing OA are done using radiographs and enzyme-linked immunosorbent assay (ELISA) method which are specific but require specialized laboratory facilities and highly trained personal. To avoid invasive methods for diagnosis, the current study describes a novel non-invasive detection method for osteoarthritis urine biomarkers. A highly selective and specific monoclonal antibodies, cartilage oligomeric matrix protein (COMP), were used to immobilize on a quartz crystal microbalance (QCM) sensor. The developed QCM sensor for COMP detection showed good sensitivity, linearity, specificity and reliability.

Research paper thumbnail of Piezoelectric sensor for sensitive determination of metal ions based on the phosphate-modified dendrimer

Smart Materials and Structures, 2016

Heavy metal ions arising from human activities are retained strongly in water; therefore public w... more Heavy metal ions arising from human activities are retained strongly in water; therefore public water supplies must be monitored regularly to ensure the timely detection of potential problems. A phosphate-modified dendrimer film was investigated on a quartz crystal microbalance (QCM) for sensing metal ions in water at room temperature in this study. The chemical structures and sensing properties were characterized by Fourier transform infrared spectroscopy and QCM measurement, respectively. This phosphate-modified dendrimer sensor can directly detect metal ions in aqueous solutions. This novel sensor was evaluated for its capacity to sense various metal ions. The sensor exhibited a higher sensitivity level and shorter response time to copper(II) ions than other sensors. The linear detection range of the prepared QCM based on the phosphate-modified dendrimer was 0.0001 ~ 1 μM Cu(II) ions (R2 = 0.98). The detection properties, including sensitivity, response time, selectivity, reusability, maximum adsorption capacity, and adsorption equilibrium constants, were also investigated.

Research paper thumbnail of ShearHorizontal Surface Acoustic WaveSensors BasedonPolyaniline forAmmoniaGasSensing

Research paper thumbnail of MOESM2 of Origination and selection of ABCDE and AGL6 subfamily MADS-box genes in gymnosperms and angiosperms

Additional file 2. Txt files of 27 species and 381 sequences.

Research paper thumbnail of Prediction of Substance Concentration in Simulated Moving Bed by Ultraviolet Sensor and Neural Network

Sensors and Materials, 2020

Research paper thumbnail of Nitric oxide sensing properties of a surface acoustic wave sensor with copper-ion-doped polyaniline/tungsten oxide nanocomposite film

Sensors and Actuators B: Chemical, 2017

Research paper thumbnail of Synthesis and anti-fungal effect of silver nanoparticles-chitosan composite particles

International journal of nanomedicine, 2015

Silver nanoparticles have been used in various fields, and several synthesis processes have been ... more Silver nanoparticles have been used in various fields, and several synthesis processes have been developed. The stability and dispersion of the synthesized nanoparticles is vital. The present article describes a novel approach for one-step synthesis of silver nanoparticles-embedded chitosan particles. The proposed approach was applied to simultaneously obtain and stabilize silver nanoparticles in a chitosan polymer matrix in-situ. The diameter of the synthesized chitosan composite particles ranged from 1.7 mm to 2.5 mm, and the embedded silver nanoparticles were measured to be 15±3.3 nm. Further, the analyses of ultraviolet-visible spectroscopy, energy dispersive spectroscopy, and X-ray diffraction were employed to characterize the prepared composites. The results show that the silver nanoparticles were distributed over the surface and interior of the chitosan spheres. The fabricated spheres had macroporous property, and could be used for many applications such as fungicidal agents ...

Research paper thumbnail of A Room-Temperature Surface Acoustic Wave Ammonia Sensor Based on rGO/DPP2T-TT Composite Films

Sensors

Surface acoustic wave (SAW) sensors based on reduced graphene oxide/poly (diketopyrrolopyrrolethi... more Surface acoustic wave (SAW) sensors based on reduced graphene oxide/poly (diketopyrrolopyrrolethiophene-thieno [3,2-b]thiophene-thiophene) (rGO/DPP2T-TT) composite sensing films for the detection of ammonia were investigated at room temperature in this study. The rGO/DPP2T-TT composite films were deposited onto ST-X quartz SAW resonators by a drop-casting method. FESEM, EDS, and XRD characterizations showed that the rGO/DPP2T-TT composite film was successfully synthesized and exhibited numerous wrinkles and a rough structure, which are crucial for gas adsorption. The frequency response to 500–1400 ppb ammonia shown by the prepared SAW sensor coated with rGO/DPP2T-TT composite film increased linearly as the ammonia concentration increased. The sensor based on a rGO/DPP2T-TT composite film exhibited a positive frequency shift of 55 Hz/ppm, and its frequency response to 500 ppb ammonia was 35 Hz. The sensors thus show promising potential in detecting sub-ppm concentration levels of NH3...

Research paper thumbnail of The Optimal Crane Scheduling for Chemical Polishing Process Based on Expert System

International Journal of Modeling and Optimization, 2018

It is well known that the manufacturing process of many industrial products requires the crane li... more It is well known that the manufacturing process of many industrial products requires the crane lifting and delivering. The use of crane can not only reduce the cost of manual handling, but also increase the production's capacity. Thus, how to design an accurate, efficient and optimal crane scheduling becomes a very important issue in the industrial manufacturing process, especially to the electronic industry. This paper presents an optimal crane scheduling and control for the multiple manufacturing processes of electronic surface treatment based on the entire plant design. The expert system with "time-axis" method is used to find the minimum number of cranes needed for the entire plant design. The surface treatment of electronic industry is used as the example for the whole design process. The result shows that the optimal crane scheduling developed can not only have the optimal cranes' control, but also fit the requirement of minimum cycling time of each manufacturing process.

Research paper thumbnail of Identification of Simulated Moving Bed Dynamic System by Neural Network

Sensors and Materials, 2021

This paper presents a study about the possibility of system identification for a simulated moving... more This paper presents a study about the possibility of system identification for a simulated moving bed (SMB), which is an important step for developing a smart SMB automatic control mechanism with a precise control capability. An SMB is a very complex and nonlinear system that is constructed from multiple columns in series and complex valve arrangements. All feed mixtures and solvents and the desorbent flow are controlled by the columns and valve devices at a fixed switching time. Thus, if the operational behavior of an SMB system can be identified in advance, then the precise control of the system can be achieved easily. In this study, the neural network (NN) technique was used to identify an SMB system. From the experimental results shown, an NN was found to be a very effective tool for SMB system identification.

Research paper thumbnail of Sparklan Antenna in Indoor Positioning Application

Sensors and Materials, 2019

In this paper, the study of a Sparklan antenna used for indoor positioning (IP) is presented. The... more In this paper, the study of a Sparklan antenna used for indoor positioning (IP) is presented. The completed sensing hardware infrastructure is composed of six Sparklan AX-106M antennas and one Zigbee module. An indoor area with a size of 64 m 2 in the building of Sue-Te University is used as the experimental field and a database including 704 sensed points with six received signal strength (RSS) signals is firstly constructed as the reference object locations. The RSSs of six antennas are used for object positioning estimation using a fuzzy estimator. To demonstrate the superiority of the developed IP system (IPS), several experiments were conducted. Experimental results show that the positioning performance of the IPS we developed is still accurate even when some antennas are disabled.

Research paper thumbnail of Enhanced Sensitive Surface Acoustic Wave Device Designed for Nitric Oxide Gas Detection

Sensors and Materials, 2019

Surface acoustic wave (SAW) devices equipped with an electrode-width-controlled (EWC)/ single-pha... more Surface acoustic wave (SAW) devices equipped with an electrode-width-controlled (EWC)/ single-phase unidirectional transducer (SPUDT) and fabricated on ST-X quartz were proposed and found to have low insertion loss and single-mode capability. The devices were then used to determine parts-per-billion levels of nitric oxide (NO). A new modified equivalent circuit (EC) model was used to model and analyze the characteristics of SAW devices prior to their fabrication. The small-signal frequency responses (S 21) obtained by simulation and measurement were consistent. A feedback-loop oscillator was used to design SAW-resonatorstabilized oscillators that provided stable oscillation. A SAW oscillator with an EWC/SPUDT structure was used to provide fundamental signals with high output power, induce high harmonic suppression, and realize long-term frequency stability. SAW devices with an EWC/ SPUDT structure were coated with a Cu 2+ /PANI/WO 3-sensitive layer to successfully determine parts-per-billion levels of NO. For a NO concentration of 50 ppb in dry air, the frequency shift in the SAW sensor with the EWC/SPUDT structure is 502 Hz. Moreover, the response and recovery time are 40 and 112 s, respectively. The sensitivity of NO detection for a concentration range of 20-80 ppb is approximately 4.2 Hz/ppb (~3.43 kHz/mg/m 3).