Papers by Mawahib Abdalrahman
Characterization of embedded microheater of a CMOS–MEMS gravimetric sensor device
Microelectronics Journal, 2016
A CMOS-MEMS device for mass detection has been designed using 2008 CoventorWare software and fabr... more A CMOS-MEMS device for mass detection has been designed using 2008 CoventorWare software and fabricated using 0.35źm CMOS technology. This paper reports the characterization of the microheater and the temperature sensor embedded in the device. The measured resistances of the microheater and the temperature sensor were found to be close to the modeled values within ~4.2% error. The average temperature coefficient of resistance (TCR) of the temperature sensor of five dies was determined by increasing or decreasing the temperature in a range of 25°C-100°C. The resistance of the temperature sensor was found to increase with either an increase in ambient temperature or the voltage applied to the microheater, with a correlation factor of 0.99. The average TCR was found to be 0.0034/°C for the increasing temperature and 0.0036/°C for the decreasing temperature as compared to 0.0037°C reported in the literature, indicating an error of 8.1% and 3.5%, respectively. These differences between the measured and reported values are believed to be due to fabrication tolerances in the design dimensions or the material properties. The humidity was found to have a negligible effect on the resistance of the temperature sensor for increasing humidity levels from 40% to 90%. The repeatability of the measurements has shown low standard errors, which gives confidence in the reliability of the fabricated device.
Journal of Sensors, 2016
Diabetes is currently screened invasively by measuring glucose concentration in blood, which is i... more Diabetes is currently screened invasively by measuring glucose concentration in blood, which is inconvenient. This paper reports a study on modeling and simulation of a CMOS-MEMS sensor for noninvasive screening of diabetes via detection of acetone vapor in exhaled breath (EB). The sensor has two structures: movable (rotor) and fixed (stator) plates. The rotor plate is suspended on top of the stator by support of four flexible beams and maintaining certain selected initial gaps of 5, 6, 7, 8, 9, 10, or 11 μm to form actuation and sensing parallel plate capacitors. A chitosan polymer of varied thicknesses (1–20 μm) is deposited on the rotor plate and modeled as a sensing element for the acetone vapor. The minimum polymer coating thickness required to detect the critical concentration (1.8 ppm) of acetone vapor in the EB of diabetic subjects is found to be 4–7 μm, depending on the initial gap between the rotor and stator plates. However, to achieve sub-ppm detection limit to sense the...
2015 6th International Conference on Intelligent Systems, Modelling and Simulation, 2015
This research studies longitudinal and transverse polysilicon resistors deposited in the maximum ... more This research studies longitudinal and transverse polysilicon resistors deposited in the maximum stress points of a CMOS-MEMS resonator for mass detection. The longitudinally mounted resistors were found to increase with the stress and giving maximum of resistance change of 10 to 23 when the actuation voltage was varied from 50 to 180 V, while the transverse resistors were found to decrease from 0.8 to 0.4 for the given voltages. Possible Wheatstone bridge configurations were studied to get the maximum output voltage, which was found to be 14 mV when two equal longitudinal resistors are connected with two equal external resistors to form a half bridge configuration.
Design and modeling of a CMOS-MEMS capacitive resonator based on bonded-dies for gas detection
2014 5th International Conference on Intelligent and Advanced Systems (ICIAS), 2014
This paper presents a capacitive CMOS-MEMS resonator for mass detection. Mass detection is used i... more This paper presents a capacitive CMOS-MEMS resonator for mass detection. Mass detection is used in many applications such as chemical industries and biomedical diagnosis. The technique used for this work is two dies bonded in parallel direction to get change in the capacitance whenever there is a change in mass and the device is electro-statically actuated. The resonance frequency of the resonator without polymer layer is found to be 17.195 kHz. The mass sensitivity and gas sensitivity are found to be 3.78 μHz/fg and 26.99 μHz/ppb, respectively. The damping ratio is found to be 1.44 in air due to squeeze film damping.
Design and Modeling of a CMOS MEMS Gravimetric Sensor
Applied Mechanics and Materials, 2013
Design and modeling of a CMOS MEMS device using 0.35 µm CMOS technology is used to achieve high s... more Design and modeling of a CMOS MEMS device using 0.35 µm CMOS technology is used to achieve high sensitivity on mass sensing is presented in this paper. The purpose of this paper is to investigate the effect of increasing beams lengths which support the membrane of the device, on the resonance frequency to achieve high sensitivity. A study on the effect of added mass on the device on natural frequency is also conducted. Mass sensitivity of this device is found to be 153 mHz/ng. At damping ratio of 0.0002, the resonant frequency of the resonator is 19.04 kHz with quality factor 3500.
Emboli or Air bubble detection is vital for many medical procedures involving Extracorporeal Bloo... more Emboli or Air bubble detection is vital for many medical procedures involving Extracorporeal Blood Circuits or ECBC e.g. hemodialysis, hemofiltration and cardiopulmonary bypass .This risk has increased as negative pressures are developed between the arterial fistula needle and the blood pump in the ECBC machine. This study suggests a capacitor device to detect the presence of air bubbles by measuring change in the output voltage. The capacitor has two platinum plates with area 0.75 cm 2. The distance between the plates is 1 cm and Dextran70 fluid is introduced as the dielectric material between the plates. This solution replaces blood to avoid clotting whilst conducting the experiment. This device is connected with a resistor i.e. 100 kΩ to form a low pass filter circuit. The change of output voltage is measured when there is a change of dielectric material of the capacitor due to the appearance of an air bubble in the stream. The sensitivity of the capacitor device is found to be 8.28 mV/ nF at 2 MHz
Capacitive Air Bubble Detector for Moving Blood in Artifical Kidney
Air bubbles detection is important for many medical procedures such as artificial kidney and open... more Air bubbles detection is important for many medical procedures such as artificial kidney and open heart surgery. Change in the output voltage across a capacitor device is used to detect the presence of air bubbles. The capacitor has two plates of platinum with area 1.5 cm 2 ; distance between the plates is 1 cm and a Dextran fluid is used as the dielectric material. The Dextran solution is used instead of blood to avoid clotting while conducting the experiment. This device is placed in a low pass filter circuit to measure the change of output voltage when there is a change of dielectric constant of the capacitor due to the appearance of air bubbles in stream of the capacitor. The sensitivity of the capacitor device was found to be 2 mV/0.079pF at 250 kHz.
Characterization of Embedded Microheater of a CMOS-MEMS Gravimetric Sensor Device
A CMOS–MEMS device for mass detection has been designed using 2008 CoventorWare software and fabr... more A CMOS–MEMS device for mass detection has been designed using 2008 CoventorWare software and fabricated using 0.35 µm CMOS technology. This paper reports the characterization of the microheater and the temperature sensor embedded in the device. The measured resistances of the microheater and the temperature sensor were found to be close to the modeled values within ~4.2% error. The average temperature coefficient of resistance (TCR) of the temperature sensor of five dies was determined by increasing or decreasing the temperature in a range of 25 °C–100 °C. The resistance of the temperature sensor was found to increase with either an increase in ambient temperature or the voltage applied to the microheater, with a correlation factor of 0.99. The average TCR was found to be 0.0034/°C for the increasing temperature and 0.0036/°C for the decreasing temperature as compared to 0.0037 °C reported in the literature, indicating an error of 8.1% and 3.5%, respectively. These differences between the measured and reported values are believed to be due to fabrication tolerances in the design dimensions or the material properties. The humidity was found to have a negligible effect on the resistance of the temperature sensor for increasing humidity levels from 40% to 90%. The repeatability of the measurements has shown low standard errors, which gives confidence in the reliability of the fabricated device.
Diabetes is currently screened invasively by measuring glucose concentration in blood, which is i... more Diabetes is currently screened invasively by measuring glucose concentration in blood, which is inconvenient. This paper reports a study on modeling and simulation of a CMOS-MEMS sensor for noninvasive screening of diabetes via detection of acetone vapor in exhaled breath (EB). The sensor has two structures: movable (rotor) and fixed (stator) plates. The rotor plate is suspended on top of the stator by support of four flexible beams and maintaining certain selected initial gaps of 5, 6, 7, 8, 9, 10, or 11 í µí¼m to form actuation and sensing parallel plate capacitors. A chitosan polymer of varied thicknesses (1–20 í µí¼m) is deposited on the rotor plate and modeled as a sensing element for the acetone vapor. The minimum polymer coating thickness required to detect the critical concentration (1.8 ppm) of acetone vapor in the EB of diabetic subjects is found to be 4–7 í µí¼m, depending on the initial gap between the rotor and stator plates. However, to achieve sub-ppm detection limit to sense the acetone vapor concentration (0.4–1.1 ppm) in the EB of healthy people, up to 20 í µí¼m polymer thickness is coated. The mathematically modeled results were verified using the 2008 CoventorWare simulation software and a good agreement within a 5.3% error was found between the modeled and the simulated frequencies giving more confidence in the predicted results.
This article describes the modeling, simulation and experimental verification of the properties o... more This article describes the modeling, simulation and experimental verification of the properties of five different macro-scale piezoelectric (PZT) cantilevers for the prediction and deduction of properties of their micro-scale counterparts in relation to their mass sensitivity. In order to investigate the relationship between resonant frequency, quality factor and mass sensitivity, piezoelectric cantilevers of different lengths from 40 mm to 10 mm are utilized keeping the other parameters constant. On the basis of the test definition and the feedback received from a reference accelerometer is mounted on shaker table, the control signal is generated by the controller unit, and the signal is amplified using an IMV MA1 type amplifier that can produce a maximum output. Then the amplified signal is fed to the shaker unit. The output from the piezoelectric is recorded and analyzed using a DEWE-3023-dsa-x type dynamic signal analyzer. Different masses are attached to the free end of the cantilevers and the change in resonance frequency measured. The main advantages of cantilevers as sensing mechanisms are their high sensitivity, low cost, high response, and low power consumption. Through this study we discover that the sensitivity is a strong function of attached mass, highest sensitivity achieved at law attached mass and stumpy PZT cantilever.
In this paper, a CMOS-MEMS resonator is fabricated with embedded micro-heater and temperature sen... more In this paper, a CMOS-MEMS resonator is fabricated with embedded micro-heater and temperature sensor for application in the detection of ammonia in exhaled breath. The resonator is fabricated using commercial 0.35 µm CMOS technology. An aluminium micro-heater and temperature sensor is used to control the temperature of the sensing layer for the detection of ammonia. The measured value of the temperature sensor resistance is determined at room temperature (24.3 °C) and is found to be 184.8 Ω compared to the calculated value of 189.85 Ω, thereby showing good agreement within an error of 0.57 %. The temperature coefficient of resistance (TCR) of the sensor is determined by measuring its resistance variation as a function of temperature from 25 °C to 100°C in 5°C increments. It is found to be 3.68×10−3/ °C and 3.79×10−3/ °C for the increasing and decreasing temperature measurements, respectively, with a percentage error of 5.6 % and 2.8 %, respectively, compared to the standard value of 3.9×10−3/ °C available in the literature. The effect of the humidity on the TCR is examined in the humidity range of 30 % RH to 90 % RH for the same temperature range of 25 °C to-40 °C and the humidity is found to have a negligible effect on the TCR of the temperature sensor.
This research studies longitudinal and transverse polysilicon resistors deposited in the maximum ... more This research studies longitudinal and transverse polysilicon resistors deposited in the maximum stress points of a CMOS-MEMS resonator for mass detection. The longitudinally mounted resistors were found to increase with the stress and giving maximum of resistance change of 10 to 23 when the actuation voltage was varied from 50 to 180 V, while the transverse resistors were found to decrease from 0.8 to 0.4 for the given voltages. Possible Wheatstone bridge configurations were studied to get the maximum output voltage, which was found to be 14 mV when two equal longitudinal resistors are connected with two equal external resistors to form a half bridge configuration.
Design and Modeling of a CMOS MEMS Gravimetric Sensor
Applied Mechanics and Materials, 2013
ABSTRACT
Exhaled breath (EB) contains thousands of volatile and nonvolatile biomolecules. EB ana... more Exhaled breath (EB) contains thousands of volatile and nonvolatile biomolecules. EB analysis is non-invasive and convenient to patients than blood or urine tests. The exhaled biomolecules have long been studied and recognized to have some potential biomarkers for
diagnosis of diseases, evaluation of metabolic disorders and monitoring drug efficiency. For instance, Biomarkers such as exhaled hydrogen peroxide (H2O2) and exhaled nitric oxide are associated with inflammatory lung diseases, ammonia is used as a biomarker for kidney diseases
and exhaled acetone is related to glucose concentration in blood and so it is used for diabetes diagnosis. H2O2 concentration in EB increases with the severity of lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and adult respiratory distress syndrome (ARDS). Different methods are used to measure H2O2in exhaled breath condensate (EBC). In EBC the EB is collected in a condensate unit and then H2O2 concentration in the collected sample is detected using titrimetric, spectrophotometry, fluorescence, chemiluminescence and electrochemical sensors. Recently, some works have been done to measure the concentration of H2O2 in its vapor phase without a need for condensation units. The aim of this paper is to review and summarize the current methods being used to measure the concentration of H2O2 in EB to identify inflammatory lung diseases, and to discuss the advantages and disadvantages of these methods.
This paper reports modeling and simulation of
polysilicon piezoresistors as sensing mechanism usi... more This paper reports modeling and simulation of
polysilicon piezoresistors as sensing mechanism using commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process. The CMOS-MEMS resonator is designed to detect
change in mass. The designed piezoresistors are composed of two types; longitudinal and transverse. CMOS polysilicon thin film is used as the piezoresistive sensing material. The finite element analysis (FEA) software CoventorWare is adopted to simulate the piezoresistors and hence, compare its values with the modeled one. When actuation voltage is applied to the piezoresistors, it generates a change in resistance which is detected by the change in current. The percentage difference between simulated stressed
and unstressed current is found to be 0.28 % and 0.47 % while
the difference in the resistance between the model and simulation is 1.96 % and 4.54 % for the transverse and longitudinal piezoresistors, respectively.
This research studies longitudinal and transverse
polysilicon resistors deposited in the maximum ... more This research studies longitudinal and transverse
polysilicon resistors deposited in the maximum stress points of
a CMOS-MEMS resonator for mass detection. The
longitudinally mounted resistors were found to increase with
the stress and giving maximum of resistance change of 10 to 23
when the actuation voltage was varied from 50 to 180 V,
while the transverse resistors were found to decrease from 0.8
to 0.4 for the given voltages. Possible Wheatstone bridge
configurations were studied to get the maximum output
voltage, which was found to be 14 mV when two equal
longitudinal resistors are connected with two equal external
resistors to form a half bridge configuration.
Air bubbles detection is important for many medical
procedures such as artificial kidney and open... more Air bubbles detection is important for many medical
procedures such as artificial kidney and open heart
surgery. Change in the output voltage across a capacitor
device is used to detect the presence of air bubbles. The
capacitor has two plates of platinum with area 1.5 cm2
;
distance between the plates is 1 cm and a Dextran fluid is
used as the dielectric material. The Dextran solution is
used instead of blood to avoid clotting while conducting
the experiment. This device is placed in a low pass filter
circuit to measure the change of output voltage when
there is a change of dielectric constant of the capacitor
due to the appearance of air bubbles in stream of the
capacitor. The sensitivity of the capacitor device was
found to be 2 mV/0.079pF at 250 kHz.
—Air bubbles have been detected in human circulation
of end-stage renal disease patients who are ... more —Air bubbles have been detected in human circulation
of end-stage renal disease patients who are treated by hemodialysis.
The consequence of air embolism, air bubbles, is under recognized
and usually overlooked in daily practice. This paper shows results of
a capacitor based detection method that capable of detecting the
presence of air bubbles in the blood stream in different frequencies.
The method is based on a parallel plates capacitor made of platinum
with an area of 1.5 cm2 and a distance between the two plates is 1cm.
The dielectric material used in this capacitor is Dextran70 solution
which mimics blood rheology. Simulations were carried out using
RC circuit at two frequencies 30Hz and 3 kHz and results compared
with experiments and theory. It is observed that by injecting air
bubbles of different diameters into the device, there were significant
changes in the capacitance of the capacitor. Furthermore, it is
observed that the output voltage from the circuit increased with
increasing air bubble diameter. These results demonstrate the
feasibility of this approach in improving air bubble detection in
Hemodialysis.
This paper presents a capacitive CMOS-MEMS
resonator for mass detection. Mass detection is used i... more This paper presents a capacitive CMOS-MEMS
resonator for mass detection. Mass detection is used in many
applications such as chemical industries and biomedical
diagnosis. The technique used for this work is two dies bonded
in parallel direction to get change in the capacitance whenever
there is a change in mass and the device is electro-statically
actuated. The resonance frequency of the resonator without
polymer layer is found to be 17.195 kHz. The mass sensitivity
and gas sensitivity are found to be 3.78 µHz/fg and 26.99
µHz/ppb, respectively. The damping ratio is found to be 1.44 in
air due to squeeze film damping.
Air bubbles detection is important for many medical procedures such as artificial kidney and open... more Air bubbles detection is important for many medical procedures such as artificial kidney and open heart surgery. Change in the output voltage across a capacitor device is used to detect the presence of air bubbles. The capacitor has two plates of platinum with area 1.5 cm2;distance between the plates is 1 cm and a Dextran fluid is used as the dielectric material. The Dextran solution is used instead of blood to avoid clotting while conducting the experiment. This device is placed in a low pass filter circuit to measure the change of output voltage when there is a change of dielectric constant of the capacitor due to the appearance of air bubbles in stream of the capacitor. The sensitivity of the capacitor device was found to be 2 mV/0.079pF at 250 kHz
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Papers by Mawahib Abdalrahman
diagnosis of diseases, evaluation of metabolic disorders and monitoring drug efficiency. For instance, Biomarkers such as exhaled hydrogen peroxide (H2O2) and exhaled nitric oxide are associated with inflammatory lung diseases, ammonia is used as a biomarker for kidney diseases
and exhaled acetone is related to glucose concentration in blood and so it is used for diabetes diagnosis. H2O2 concentration in EB increases with the severity of lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and adult respiratory distress syndrome (ARDS). Different methods are used to measure H2O2in exhaled breath condensate (EBC). In EBC the EB is collected in a condensate unit and then H2O2 concentration in the collected sample is detected using titrimetric, spectrophotometry, fluorescence, chemiluminescence and electrochemical sensors. Recently, some works have been done to measure the concentration of H2O2 in its vapor phase without a need for condensation units. The aim of this paper is to review and summarize the current methods being used to measure the concentration of H2O2 in EB to identify inflammatory lung diseases, and to discuss the advantages and disadvantages of these methods.
polysilicon piezoresistors as sensing mechanism using commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process. The CMOS-MEMS resonator is designed to detect
change in mass. The designed piezoresistors are composed of two types; longitudinal and transverse. CMOS polysilicon thin film is used as the piezoresistive sensing material. The finite element analysis (FEA) software CoventorWare is adopted to simulate the piezoresistors and hence, compare its values with the modeled one. When actuation voltage is applied to the piezoresistors, it generates a change in resistance which is detected by the change in current. The percentage difference between simulated stressed
and unstressed current is found to be 0.28 % and 0.47 % while
the difference in the resistance between the model and simulation is 1.96 % and 4.54 % for the transverse and longitudinal piezoresistors, respectively.
polysilicon resistors deposited in the maximum stress points of
a CMOS-MEMS resonator for mass detection. The
longitudinally mounted resistors were found to increase with
the stress and giving maximum of resistance change of 10 to 23
when the actuation voltage was varied from 50 to 180 V,
while the transverse resistors were found to decrease from 0.8
to 0.4 for the given voltages. Possible Wheatstone bridge
configurations were studied to get the maximum output
voltage, which was found to be 14 mV when two equal
longitudinal resistors are connected with two equal external
resistors to form a half bridge configuration.
procedures such as artificial kidney and open heart
surgery. Change in the output voltage across a capacitor
device is used to detect the presence of air bubbles. The
capacitor has two plates of platinum with area 1.5 cm2
;
distance between the plates is 1 cm and a Dextran fluid is
used as the dielectric material. The Dextran solution is
used instead of blood to avoid clotting while conducting
the experiment. This device is placed in a low pass filter
circuit to measure the change of output voltage when
there is a change of dielectric constant of the capacitor
due to the appearance of air bubbles in stream of the
capacitor. The sensitivity of the capacitor device was
found to be 2 mV/0.079pF at 250 kHz.
of end-stage renal disease patients who are treated by hemodialysis.
The consequence of air embolism, air bubbles, is under recognized
and usually overlooked in daily practice. This paper shows results of
a capacitor based detection method that capable of detecting the
presence of air bubbles in the blood stream in different frequencies.
The method is based on a parallel plates capacitor made of platinum
with an area of 1.5 cm2 and a distance between the two plates is 1cm.
The dielectric material used in this capacitor is Dextran70 solution
which mimics blood rheology. Simulations were carried out using
RC circuit at two frequencies 30Hz and 3 kHz and results compared
with experiments and theory. It is observed that by injecting air
bubbles of different diameters into the device, there were significant
changes in the capacitance of the capacitor. Furthermore, it is
observed that the output voltage from the circuit increased with
increasing air bubble diameter. These results demonstrate the
feasibility of this approach in improving air bubble detection in
Hemodialysis.
resonator for mass detection. Mass detection is used in many
applications such as chemical industries and biomedical
diagnosis. The technique used for this work is two dies bonded
in parallel direction to get change in the capacitance whenever
there is a change in mass and the device is electro-statically
actuated. The resonance frequency of the resonator without
polymer layer is found to be 17.195 kHz. The mass sensitivity
and gas sensitivity are found to be 3.78 µHz/fg and 26.99
µHz/ppb, respectively. The damping ratio is found to be 1.44 in
air due to squeeze film damping.