Muhammad Ali Shah - Academia.edu (original) (raw)

Papers by Muhammad Ali Shah

Sensors

The study investigates the effect of changing various input parameters on the pressure responses ... more The study investigates the effect of changing various input parameters on the pressure responses at acoustic cavities of a droplet-based acoustic printing device consisting of a Fabry–Pérot (FP) resonator and a standing wave-source chamber. The standing wave of the acoustic radiation pressure at the FP resonator is analyzed. The behavior of the standing wave and acoustic radiation force at the FP resonator is presented and compared with the measured results by varying the position of the standing wave-generating plate. The pressure changes inside the standing wave-source chamber are investigated and discussed to determine the reason for the sudden high-pressure drop at the FP resonator. Furthermore, the effects of inserting the nozzle and droplet inside the FP resonator on the standing wave and acoustic radiation force are analyzed. Experimental analysis is performed by collecting acoustic pressure data at the outlet of the FP resonator. The simulated and measured pressure drop beha...

Polymers, 2021

Divinylsiloxane-bis-benzocyclobutene (DVS-BCB) has attracted significant attention as an intermed... more Divinylsiloxane-bis-benzocyclobutene (DVS-BCB) has attracted significant attention as an intermediate bonding material, owing to its excellent properties. However, its applications are limited, due to damage to peripheral devices at high curing temperatures and unoptimized compressive pressure. Therefore, it is necessary to explore the compressive pressure condition for DVS-BCB bonding. This study demonstrates an optimization process for void-free DVS-BCB bonding. The process for obtaining void-free DVS-BCB bonding is a vacuum condition of 0.03 Torr, compressive pressure of 0.6 N/mm2, and curing temperature of 250 °C for 1 h. Herein, we define two factors affecting the DVS-BCB bonding quality through the DVS-BCB bonding mechanism. For strong DVS-BCB bonding, void-free and high-density chemical bonds are required. Therefore, we observed the DVS-BCB bonding under various compressive pressure conditions at a relatively low temperature (250 °C). The presence of voids and high-density cr...

Micromachines, 2020

2017 IEEE 12th International Conference on Nano/Micro Engineered and Molecular Systems (NEMS)

Journal of Sensors, 2016

This paper reports on designing a single-structure triaxes MEMS capacitive gyroscope which is cap... more This paper reports on designing a single-structure triaxes MEMS capacitive gyroscope which is capable of measuring the three angular velocities on a single drive. A Z-shaped beam for the support of folded coupling spring has been applied to suppress the unwanted mode and decrease the stress effect at the spring ends. The unique coupling spring has changed the driving motion, due to which slide film damping in the driving mode has been reduced. This reduction can lead to higher performance of the sensor with less requirements on vacuum level which decreases the cost of fabrication. Simulation analysis has been performed in COMSOL Multiphysics and Matlab Simulink to finalize the design for fabrication. After finite element analysis, the driving, x-sensing, z-sensing, and y-sensing are, respectively, found to be 13.30 KHz, 13.40 KHz, 13.47 KHz, and 13.51 KHz.

Journal of Sensors

This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of ... more This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of this review is to identify the issues in MEMS microphone designs and thoroughly discuss the state-of-the-art solutions that have been presented by the researchers to improve performance. Considerable research work has been carried out in capacitive MEMS microphones, and this field has attracted the research community because these designs have high sensitivity, flat frequency response, and low noise level. A detailed overview of the omnidirectional microphones used in the applications of an audio frequency range has been presented. Since the microphone membrane is made of a thin film, it has residual stress that degrades the microphone performance. An in-depth detailed review of research articles containing solutions to relieve these stresses has been presented. The comparative analysis of fabrication processes of single- and dual-chip omnidirectional microphones, in which the membranes ...

This paper reports the design and analysis of a single drive mass three axis Microelectromechanic... more This paper reports the design and analysis of a single drive mass three axis Microelectromechanical systems (MEMS) gyroscope. The proposed MEMS gyroscope contains a unique and simple coupling spring to couple the driving masses. Due to the use of this coupling spring, the stress effect on the spring ends is reduced as it is attached at two points with the driving mass. Moreover, the unwanted motions of the driving mass can be suppressed due to the use of the two spring beams for the support of the central spring. After FEA simulation using COMSOL Multiphysics tool, a first driving mode of the proposed design has been achieved. Other modes were achieved for the pitch, roll and yaw sensing parts. The simulated resonant frequencies are 15.20 kHz for the driving mode, 15.21 kHz for the pitch sensing mode, 15.32 kHz for the roll sensing mode and 15.59 kHz for the yaw sensing mode, respectively.

A dual axis microelectromechanicalsystem (MEMS) seismometer targeted for building monitoring syst... more A dual axis microelectromechanicalsystem (MEMS) seismometer targeted for building monitoring system during earthquake has been simulated for a full scale of ±5g acceleration. The design uses the capacitive effect for vibration sensing. This comb drive capacitive MEMS seismometer consists of 8 springs with two proof masses. The device is very low cross axis sensitive (almost negligible cross axis error). The cross axis sensitivities of X-axis are 0.001% and 0.00009% towards Y-and Z-axes respectively, while the Y-axis cross axis sensitivities towards X-axis is 0.000005% and Zaxis is 0.0001% when maximum input acceleration of 5g is applied. COMSOL Multiphysics (V. 5.0) has been used to compute the eigenfrequencies and static responses of the device. Von-mises stresses were applied at X-and Y-axes for the estimations of fracture in the springs under 5g acceleration. From simulation results, the displacement sensitivities of X-axis=0.114µm/g and Y-axis=0.204µm/g while capacitive sensitivities of X-axis=0.551pF/g and Y-axis= 0.346pF/g were calculated.

After a piezoelectric inkjet printhead jets the first droplet, the actuating membrane still vibra... more After a piezoelectric inkjet printhead jets the first droplet, the actuating membrane still vibrates, creating residual vibrations in the ink channel, which can degrade the inkjet printhead performance. For suppressing these vibrations, an optimized actuating voltage waveform with two pulses must be obtained, of which the first pulse is used for jetting and the second pulse is used to suppress the residual vibrations. In this study, the pressure history within the ink channel of a recirculating piezoelectric inkjet printhead was first acquired using lumped element modeling. Then, for suppressing residual vibrations, a bipolar voltage waveform was optimized via analysis of the tuning time (t t), dwell time (t d2), rising time (t r2), falling time (t f2), and voltage amplitude of the second pulse. Two voltage waveforms, Waveform 01 and Waveform 02, were optimized thereafter. In Waveform 01, t t = 2 µs, t d2 = 2 µs, and t r2 and t f2 = 1 µs were finalized as the optimal parameters; in the case of another waveform, the optimal parameters of t d2 , t r2 , and t f2 were found to be 4, 1, and 1 µs, respectively. The optimal voltage amplitude of the second pulse was found to be 1/3 the amplitude of the first pulse. On the basis of our analysis, the tuning time in Waveform 01 is the most sensitive parameter, and the performance yielded is even poorer than that yielded by standard waveform, if not optimized. Therefore, the other waveform is recommended for the suppression of residual vibrations.

The recirculation of ink in an inkjet printhead system keeps the ink temperature and viscosity co... more The recirculation of ink in an inkjet printhead system keeps the ink temperature and viscosity constant, and leads to the development of a high-performance device. Herein, we propose a recirculating piezo-driven micro-electro-mechanical system (MEMS)-based inkjet printhead that has a pressure chamber, a nozzle, and double restrictors. The design and characteristic analysis are performed using a two-port lumped element model (LEM) to investigate the effect of design parameters on the system responses. Using LEM, the jetting pressure at the pressure chamber, velocity at the nozzle inlet, meniscus pressure, and Helmholtz resonance frequency are predicted and the comparative analysis of the jetting pressure and velocity between LEM and the finite element method (FEM) simulation is conducted to validate our proposed LEM method. Furthermore, the effect of a change in major design parameters on the jetting pressure, velocity, and Helmholtz resonance frequency is analyzed. On the basis of this analysis, the optimized device dimensions are finalized. From our analysis, it is also concluded that the restrictor is more sensitive than the pressure chamber in terms of their variations in depth. As the cross-talk effect can occur due to an array of hundreds or thousands of nozzles, we investigated the effect of a single activated nozzle on the non-activated neighboring nozzles, as well as the effect of multi-activated nozzles on a single central nozzle using our proposed LEM.

This paper reports on designing a single-structure triaxes MEMS capacitive gyroscope which is cap... more This paper reports on designing a single-structure triaxes MEMS capacitive gyroscope which is capable of measuring the three angular velocities on a single drive. A Z-shaped beam for the support of folded coupling spring has been applied to suppress the unwanted mode and decrease the stress effect at the spring ends. The unique coupling spring has changed the driving motion, due to which slide film damping in the driving mode has been reduced. This reduction can lead to higher performance of the sensor with less requirements on vacuum level which decreases the cost of fabrication. Simulation analysis has been performed in COMSOL Multiphysics and Matlab Simulink to finalize the design for fabrication. After finite element analysis, the driving,-sensing,-sensing, and-sensing are, respectively, found to be 13.30 KHz, 13.40 KHz, 13.47 KHz, and 13.51 KHz.

This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of ... more This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of this review is to identify the issues in MEMS microphone designs and thoroughly discuss the state-of-the-art solutions that have been presented by the researchers to improve performance. Considerable research work has been carried out in capacitive MEMS microphones, and this field has attracted the research community because these designs have high sensitivity, flat frequency response, and low noise level. A detailed overview of the omnidirectional microphones used in the applications of an audio frequency range has been presented. Since the microphone membrane is made of a thin film, it has residual stress that degrades the microphone performance. An in-depth detailed review of research articles containing solutions to relieve these stresses has been presented. The comparative analysis of fabrication processes of single-and dual-chip omnidirectional microphones, in which the membranes are made up of single-crystal silicon, polysilicon, and silicon nitride, has been done, and articles containing the improved performance in these two fabrication processes have been explained. This review will serve as a starting guide for new researchers in the field of capacitive MEMS microphones.

Sensors

Polymers, 2021

Micromachines, 2020

2017 IEEE 12th International Conference on Nano/Micro Engineered and Molecular Systems (NEMS)

Journal of Sensors, 2016

Journal of Sensors

This paper reports on designing a single-structure triaxes MEMS capacitive gyroscope which is cap... more This paper reports on designing a single-structure triaxes MEMS capacitive gyroscope which is capable of measuring the three angular velocities on a single drive. A Z-shaped beam for the support of folded coupling spring has been applied to suppress the unwanted mode and decrease the stress effect at the spring ends. The unique coupling spring has changed the driving motion, due to which slide film damping in the driving mode has been reduced. This reduction can lead to higher performance of the sensor with less requirements on vacuum level which decreases the cost of fabrication. Simulation analysis has been performed in COMSOL Multiphysics and Matlab Simulink to finalize the design for fabrication. After finite element analysis, the driving,-sensing,-sensing, and-sensing are, respectively, found to be 13.30 KHz, 13.40 KHz, 13.47 KHz, and 13.51 KHz.

This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of ... more This paper reports a review about microelectromechanical system (MEMS) microphones. The focus of this review is to identify the issues in MEMS microphone designs and thoroughly discuss the state-of-the-art solutions that have been presented by the researchers to improve performance. Considerable research work has been carried out in capacitive MEMS microphones, and this field has attracted the research community because these designs have high sensitivity, flat frequency response, and low noise level. A detailed overview of the omnidirectional microphones used in the applications of an audio frequency range has been presented. Since the microphone membrane is made of a thin film, it has residual stress that degrades the microphone performance. An in-depth detailed review of research articles containing solutions to relieve these stresses has been presented. The comparative analysis of fabrication processes of single-and dual-chip omnidirectional microphones, in which the membranes are made up of single-crystal silicon, polysilicon, and silicon nitride, has been done, and articles containing the improved performance in these two fabrication processes have been explained. This review will serve as a starting guide for new researchers in the field of capacitive MEMS microphones.