Haleh Nazemi - Academia.edu (original) (raw)
Papers by Haleh Nazemi
Sensors
With the development of technology, systems gravitate towards increasing in their complexity, min... more With the development of technology, systems gravitate towards increasing in their complexity, miniaturization, and level of automation. Amongst these systems, ultrasonic devices have adhered to this trend of advancement. Ultrasonic systems require transducers to generate and sense ultrasonic signals. These transducers heavily impact the system’s performance. Advancements in microelectromechanical systems have led to the development of micromachined ultrasonic transducers (MUTs), which are utilized in miniaturized ultrasound systems. Piezoelectric micromachined ultrasonic transducers (PMUTs) exhibit higher capacitance and lower electrical impedance, which enhances the transducer’s sensitivity by minimizing the effect of parasitic capacitance and facilitating their integration with low-voltage electronics. PMUTs utilize high-yield batch microfabrication with the use of thin piezoelectric films. The deposition of thin piezoelectric material compatible with complementary metal-oxide sem...
According to the Canadian Cancer Society, lung cancer is the one of the leading causes of cancer ... more According to the Canadian Cancer Society, lung cancer is the one of the leading causes of cancer death. It has been shown that cancer survival chance depends on factors including the availability of early detection and diagnostic tools such as miniaturized and sensitive gas sensor. This can detect the released volatiles in addition to be implementable in portable electronics, which decisively improves the patient’s survival rate. Therefore, in this thesis and in an effort to develop high-sensitive and miniaturized gas sensor, a microelectromechanical systems (MEMS) platform is utilized. In this work, a sensitive gas sensor is proposed by employing capacitive micromachined ultrasonic transducer (CMUT) configuration due to its high sensitivity, low LOD and reversibility. The comprehensive analytical model is proposed for this circular bilayer CMUT-based gas sensor for the first time, which includes all the known critical design parameters of the sensor. The model also includes effects...
Encyclopedia of Sensors and Biosensors, 2021
2020 IEEE International Ultrasonics Symposium (IUS), 2020
This paper presents a theoretical model and an experimental validation of a two-port multiple mov... more This paper presents a theoretical model and an experimental validation of a two-port multiple moving membrane capacitive micromachined ultrasonic transducer. The developed transducer includes a stack of two flexible membranes suspended on a fixed electrode. The transducer is fabricated utilizing a sacrificial technique, PolyMUMPs, and with a resonant frequency of 1.8 MHz. Electrical measurements are conducted using an impedance analyzer in order to investigate the influence of the transducer's additional moving membrane on the device effective cavity height. This, consequently, influences the transducer acoustic power generation. The deigned two port transducer enables a dynamic change in the effective cavity height through adjusting the applied DC bias voltage. The experimental results validate this hypothesis and are shown in agreement with the theoretical results.
Sensors, 2020
Microelectromechanical system (MEMS)-based mass sensors are proposed as potential candidates for ... more Microelectromechanical system (MEMS)-based mass sensors are proposed as potential candidates for highly sensitive chemical and gas detection applications owing to their miniaturized structure, low power consumption, and ease of integration with readout circuits. This paper presents a new approach in developing micromachined mass sensors based on capacitive and piezoelectric transducer configurations for use in low concentration level gas detection in a complex environment. These micromachined sensors operate based on a shift in their center resonant frequencies. This shift is caused by a change in the sensor’s effective mass when exposed to the target gas molecules, which is then correlated to the gas concentration level. In this work, capacitive and piezoelectric-based micromachined sensors are investigated and their principle of operation, device structures and configurations, critical design parameters and their candidate fabrication techniques are discussed in detail.
Sensors, 2021
This work is a comprehensive review of sensing materials, which interact with several target gase... more This work is a comprehensive review of sensing materials, which interact with several target gases pertinent to agricultural monitoring applications. Sensing materials which interact with carbon dioxide, water vapor (relative humidity), hydrogen sulfide, ethylene and ethanol are the focus of this work. Performance characteristics such as dynamic range, recovery time, operating temperature, long-term stability and method of deposition are discussed to determine the commercial viability of the sensing materials considered in this work. In addition to the sensing materials, deposition methods are considered to obtain the desired sensing material thickness based on the sensor’s mechanism of operation. Various material classes including metal oxides, conductive polymers and carbon allotropes are included in this review. By implementing multiple sensing materials to detect a single target analyte, the issue of selectivity due to cross sensitivity can be mitigated. For this reason, where p...
Micromachines, 2020
Advancements in microfabrication technologies and novel materials have led to new innovations in ... more Advancements in microfabrication technologies and novel materials have led to new innovations in miniaturized gas sensors that can identify miniscule changes in a complex environment. Micromachined resonators with the capability to offer high sensitivity and selectivity in array integration make mass loading a potential mechanism for electronic nose applications. This paper investigates the mass sensing characteristics of progressive capacitive based micromachined resonators as potential candidates for volatile organic compound detection where also there is a need for miniaturized array configuration. In this paper, a detailed investigative review of the major three geometric designs of capacitive based micromachined resonators, namely, the microcantilever, the microbridge and the clamped membrane sensors is performed. Although many reviews are present in literature regarding mass sensors, however there is a gap in the literature regarding the common capacitive based micromachined m...
Sensors, 2019
Micro- and nano-sensors lie at the heart of critical innovation in fields ranging from medical to... more Micro- and nano-sensors lie at the heart of critical innovation in fields ranging from medical to environmental sciences. In recent years, there has been a significant improvement in sensor design along with the advances in micro- and nano-fabrication technology and the use of newly designed materials, leading to the development of high-performance gas sensors. Advanced micro- and nano-fabrication technology enables miniaturization of these sensors into micro-sized gas sensor arrays while maintaining the sensing performance. These capabilities facilitate the development of miniaturized integrated gas sensor arrays that enhance both sensor sensitivity and selectivity towards various analytes. In the past, several micro- and nano-gas sensors have been proposed and investigated where each type of sensor exhibits various advantages and limitations in sensing resolution, operating power, response, and recovery time. This paper presents an overview of the recent progress made in a wide ra...
Capacitive Micromachined Ultrasonic Transducers (CMUTs) have been introduced as an alternative ca... more Capacitive Micromachined Ultrasonic Transducers (CMUTs) have been introduced as an alternative candidate to piezoelectric transducers for ultrasonic imaging applications due to their better acoustic matching and higher bandwidth. In this paper and in an unconventional approach, a CMUT configuration is used as a highly-sensitive gas sensor that operates based on the measured frequency shifts in response to the mass of absorbed target analytes. In this work, a new complex bi-layer CMUT gas sensor model is developed that comprises the effect of sensing material properties as well as the sensor structural materials and geometrical design parameters to optimize and enhance the sensor sensitivity based on the application. The proposed analytical model is further utilized to design a high-sensitivity CMUT sensor for low concentration detection of gas molecules. The analytical model analysis and finite element method simulations are also conducted and compared. The results show a high achie...
Sensors
With the development of technology, systems gravitate towards increasing in their complexity, min... more With the development of technology, systems gravitate towards increasing in their complexity, miniaturization, and level of automation. Amongst these systems, ultrasonic devices have adhered to this trend of advancement. Ultrasonic systems require transducers to generate and sense ultrasonic signals. These transducers heavily impact the system’s performance. Advancements in microelectromechanical systems have led to the development of micromachined ultrasonic transducers (MUTs), which are utilized in miniaturized ultrasound systems. Piezoelectric micromachined ultrasonic transducers (PMUTs) exhibit higher capacitance and lower electrical impedance, which enhances the transducer’s sensitivity by minimizing the effect of parasitic capacitance and facilitating their integration with low-voltage electronics. PMUTs utilize high-yield batch microfabrication with the use of thin piezoelectric films. The deposition of thin piezoelectric material compatible with complementary metal-oxide sem...
According to the Canadian Cancer Society, lung cancer is the one of the leading causes of cancer ... more According to the Canadian Cancer Society, lung cancer is the one of the leading causes of cancer death. It has been shown that cancer survival chance depends on factors including the availability of early detection and diagnostic tools such as miniaturized and sensitive gas sensor. This can detect the released volatiles in addition to be implementable in portable electronics, which decisively improves the patient’s survival rate. Therefore, in this thesis and in an effort to develop high-sensitive and miniaturized gas sensor, a microelectromechanical systems (MEMS) platform is utilized. In this work, a sensitive gas sensor is proposed by employing capacitive micromachined ultrasonic transducer (CMUT) configuration due to its high sensitivity, low LOD and reversibility. The comprehensive analytical model is proposed for this circular bilayer CMUT-based gas sensor for the first time, which includes all the known critical design parameters of the sensor. The model also includes effects...
Encyclopedia of Sensors and Biosensors, 2021
2020 IEEE International Ultrasonics Symposium (IUS), 2020
This paper presents a theoretical model and an experimental validation of a two-port multiple mov... more This paper presents a theoretical model and an experimental validation of a two-port multiple moving membrane capacitive micromachined ultrasonic transducer. The developed transducer includes a stack of two flexible membranes suspended on a fixed electrode. The transducer is fabricated utilizing a sacrificial technique, PolyMUMPs, and with a resonant frequency of 1.8 MHz. Electrical measurements are conducted using an impedance analyzer in order to investigate the influence of the transducer's additional moving membrane on the device effective cavity height. This, consequently, influences the transducer acoustic power generation. The deigned two port transducer enables a dynamic change in the effective cavity height through adjusting the applied DC bias voltage. The experimental results validate this hypothesis and are shown in agreement with the theoretical results.
Sensors, 2020
Microelectromechanical system (MEMS)-based mass sensors are proposed as potential candidates for ... more Microelectromechanical system (MEMS)-based mass sensors are proposed as potential candidates for highly sensitive chemical and gas detection applications owing to their miniaturized structure, low power consumption, and ease of integration with readout circuits. This paper presents a new approach in developing micromachined mass sensors based on capacitive and piezoelectric transducer configurations for use in low concentration level gas detection in a complex environment. These micromachined sensors operate based on a shift in their center resonant frequencies. This shift is caused by a change in the sensor’s effective mass when exposed to the target gas molecules, which is then correlated to the gas concentration level. In this work, capacitive and piezoelectric-based micromachined sensors are investigated and their principle of operation, device structures and configurations, critical design parameters and their candidate fabrication techniques are discussed in detail.
Sensors, 2021
This work is a comprehensive review of sensing materials, which interact with several target gase... more This work is a comprehensive review of sensing materials, which interact with several target gases pertinent to agricultural monitoring applications. Sensing materials which interact with carbon dioxide, water vapor (relative humidity), hydrogen sulfide, ethylene and ethanol are the focus of this work. Performance characteristics such as dynamic range, recovery time, operating temperature, long-term stability and method of deposition are discussed to determine the commercial viability of the sensing materials considered in this work. In addition to the sensing materials, deposition methods are considered to obtain the desired sensing material thickness based on the sensor’s mechanism of operation. Various material classes including metal oxides, conductive polymers and carbon allotropes are included in this review. By implementing multiple sensing materials to detect a single target analyte, the issue of selectivity due to cross sensitivity can be mitigated. For this reason, where p...
Micromachines, 2020
Advancements in microfabrication technologies and novel materials have led to new innovations in ... more Advancements in microfabrication technologies and novel materials have led to new innovations in miniaturized gas sensors that can identify miniscule changes in a complex environment. Micromachined resonators with the capability to offer high sensitivity and selectivity in array integration make mass loading a potential mechanism for electronic nose applications. This paper investigates the mass sensing characteristics of progressive capacitive based micromachined resonators as potential candidates for volatile organic compound detection where also there is a need for miniaturized array configuration. In this paper, a detailed investigative review of the major three geometric designs of capacitive based micromachined resonators, namely, the microcantilever, the microbridge and the clamped membrane sensors is performed. Although many reviews are present in literature regarding mass sensors, however there is a gap in the literature regarding the common capacitive based micromachined m...
Sensors, 2019
Micro- and nano-sensors lie at the heart of critical innovation in fields ranging from medical to... more Micro- and nano-sensors lie at the heart of critical innovation in fields ranging from medical to environmental sciences. In recent years, there has been a significant improvement in sensor design along with the advances in micro- and nano-fabrication technology and the use of newly designed materials, leading to the development of high-performance gas sensors. Advanced micro- and nano-fabrication technology enables miniaturization of these sensors into micro-sized gas sensor arrays while maintaining the sensing performance. These capabilities facilitate the development of miniaturized integrated gas sensor arrays that enhance both sensor sensitivity and selectivity towards various analytes. In the past, several micro- and nano-gas sensors have been proposed and investigated where each type of sensor exhibits various advantages and limitations in sensing resolution, operating power, response, and recovery time. This paper presents an overview of the recent progress made in a wide ra...
Capacitive Micromachined Ultrasonic Transducers (CMUTs) have been introduced as an alternative ca... more Capacitive Micromachined Ultrasonic Transducers (CMUTs) have been introduced as an alternative candidate to piezoelectric transducers for ultrasonic imaging applications due to their better acoustic matching and higher bandwidth. In this paper and in an unconventional approach, a CMUT configuration is used as a highly-sensitive gas sensor that operates based on the measured frequency shifts in response to the mass of absorbed target analytes. In this work, a new complex bi-layer CMUT gas sensor model is developed that comprises the effect of sensing material properties as well as the sensor structural materials and geometrical design parameters to optimize and enhance the sensor sensitivity based on the application. The proposed analytical model is further utilized to design a high-sensitivity CMUT sensor for low concentration detection of gas molecules. The analytical model analysis and finite element method simulations are also conducted and compared. The results show a high achie...