Marwan Nafea | The University of Nottingham Malaysia Campus (original) (raw)

Journal Papers by Marwan Nafea

European Polymer Journal, 2021

Four-dimensional (4D) printing is gaining interest in the past few years. The prototyping freedom... more Four-dimensional (4D) printing is gaining interest in the past few years. The prototyping freedom of 3D printing coupled with the abilities of smart materials and their properties gave rise to a new field of active structures. 4D printed structures are responsive to outside stimuli, thus allowing them to change some of their characteristics. This behaviour presents a base for revolutionary advancements in the field of robotics, biomedicine, and industry. This review presents an overview of all steps involved in the 4D printing of shape memory polymers rooted in recent applications. Furthermore, this paper aims to provide researchers with a basis for design when choosing materials and printing methods that suit their application needs. The shape memory effect of 4D-printed designs, along with 4D printing techniques, and shape programming of the materials are discussed. Recent advances in 4D printing of shape memory polymers with their applications are the focus of this review, whether single or multi material, with the programming of such materials for specific actuation. In addition, this paper discusses multiple methods that can be used to control the shape memory effect of 4D-printed designs, which range from the designs of the structure, the materials used, the methods and orientations of printing, activation criteria, and others. Moreover, this paper explores the range of complexity in 4D printing, which allows for control of the actuation in terms of time, force, speed, and stages, opening a wide range of applications that could benefit from this technology.

Isolation of Fetal ECG Signals from Abdominal ECG Using Wavelet Analysis, 2020

Objective Monitoring the heartbeat of the fetus during pregnancy is a vital part in determining t... more Objective
Monitoring the heartbeat of the fetus during pregnancy is a vital part in determining their health. Current fetal heart monitoring techniques lack the accuracy in fetal heart rate monitoring and features acquisition, resulting in diagnostic medical issues. The demand for a reliable method of non-invasive fetal heart monitoring is of high importance.
Method
Electrocardiogram (ECG) is a method of monitoring the electrical activity produced by the heart. The extraction of the fetal ECG (FECG) from the abdominal ECG (AECG) is challenging since both ECGs of the mother and the baby share similar frequency components, adding to the fact that the signals are corrupted by white noise. This paper presents a method of FECG extraction by eliminating all other signals using AECG. The algorithm is based on attenuating the maternal ECG (MECG) by filtering and wavelet analysis to find the locations of the FECG, and thus isolating them based on their locations. Two signals of AECG collected at different locations on the abdomens are used. The ECG data used contains MECG of a power of five to ten times that of the FECG.
Results
The FECG signals were successfully isolated from the AECG using the proposed method through which the QRS complex of the heartbeat was conserved, and heart rate was calculated. The fetal heart rate was 135 bpm and the instantaneous heart rate was 131.58 bpm. The heart rate of the mother was at 90 bpm with an instantaneous heart rate of 81.9 bpm.
Conclusion
The proposed method is promising for FECG extraction since it relies on filtering and wavelet analysis of two abdominal signals for the algorithm. The method implemented is easily adjusted based on the power levels of signals, giving it great ease of adaptation to changing signals in different biosignals applications.

PDMS-based dual-channel pneumatic micro-actuator, Oct 24, 2019

This paper presents a monolithic novel polydimethylsiloxane-based dual-channel bellows-structured... more This paper presents a monolithic novel polydimethylsiloxane-based dual-channel bellows-structured pneumatic actuator, fabricated through a sacrificial molding technique. A finite element analysis was performed to find the optimal structure and analyze the bending performance of the square-bellows actuator. The actuator was designed with an overall cross-sectional area of 5 × 5 mm2, while its structural parameters were characterized in terms of 8, 12, 16 and 20 number of bellows. The actuator models were fabricated using acrylonitrile butadiene styrene-based sacrificial molds to form the channel and bellows structures. The experimental validation has revealed that the actuator having highest number of bellows with a size of 5 × 5 × 68.4 mm3 attained a smooth bi-directional bending motion, with maximum angles of −65° and 75°, and force of 0.166 and 0.221 N under left and right channel actuation, respectively, at 100 kPa pressure. Hence, the state-of-the-art dual-channel square-bellows actuator was able to achieve an optimal bi-directional bending with slight variations to change in temperature, which would push the boundaries of soft robotics toward the development of safer and more flexible robotic surgical tools.

A Multi-Segmented Shape Memory Alloy-based Actuator System for Endoscopic Applications, Jul 3, 2019

This paper describes the design, fabrication and testing of a shape memory alloy based actuator s... more This paper describes the design, fabrication and testing of a shape memory alloy based actuator system to provide three degrees of freedom bending with high flexibility and repeated use capability without any performance loss for minimally invasive surgery. The flexibility, long-term endurance and thermal characteristics of this system were studied. The system consisted of 3 segments, front, middle and back. Thermal simulations showed an increase in temperature of 1–2 °C at the segment nearest to the activated segment and a temperature increase of 1 °C at the segment furthest from the activated segment. Transformation strain simulations showed that the 8 mm width design has the lowest strain (2 %). The average maximum bending angle was above 30° across most actuator segments but a reformation angle of only 50 % of the maximum angle. The endurance test showed that all actuators can operate for 7,000 actuation cycles with a standard deviation of 0.6154, 0.8293 and 0.0364 mm for sections A, B and C, respectively. The system was capable of high angle of bending across all segments and capable of continuous long-term use with little performance deviation. The system will allow surgeons to have more flexibility during surgery and thus enable reaching difficult regions in minimally invasive surgery.

Modeling and simulation of a wirelessly-powered thermopneumatic micropump for drug delivery applications, May 20, 2019

This paper presents modeling and finite element analysis of a thermopneumatic micropump with a n... more This paper presents modeling and finite element analysis of a thermopneumatic micropump with a novel design that does not affect the temperature of the working fluid. The micropump is operated by activating a passive wireless heater using wireless power transfer when the magnetic field is tuned to match the resonant frequency of the heater. The heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element. The solution inside the reservoir is pumped through a microchannel that ends with an outlet hole. The thermal and pumping performances of the micropump are analyzed using finite element method over a low range of Reynold’s number ⩽ 10 that is suitable for various biomedical applications. The results demonstrate promising performance with a maximum flow rate of ∼2.86 μL/min at a chamber temperature of 42.5 ºC, and a maximum pumping pressure of 406.5 Pa. The results show that the developed device can be potentially implemented in various biomedical areas, such as implantable drug delivery applications.

A wirelessly-controlled piezoelectric microvalve for regulated drug delivery, Jul 15, 2018

This paper reports a novel wireless control of a normally-closed piezoelectric microvalve activat... more This paper reports a novel wireless control of a normally-closed piezoelectric microvalve activated by a wireless inductor-capacitor (LC) resonant circuit, and enabled by an external magnetic field. The LC circuit is formed by connecting a multilayer coil to a piezoelectric actuator (PEA) that behaves as a capacitor and a resistor in parallel. The LC circuit is activated by modulating the field frequency to its resonant frequency (fr) of 10 kHz, which matches the optimal operating frequency of the device, while considering the resonant frequency of the PEA. The working fluid is stored in an 88.9 μL polydimethylsiloxane balloon reservoir that pumps the liquid due to the difference in pressure, which eliminates the need for a pump. The design of the device was optimized using several analytical and experimental approaches. This device was fabricated using a time and cost-effective out-of-clean-room fabrication process. The valving performance was initially characterized in air, then in phosphate buffered saline (PBS) solution to mimic the drug release kinetics into human interstitial body fluids. Maximum flow rate values of 8.91 and 7.42 μL/min are achieved in air and PBS solution respectively, at a maximum input pressure value of ∼13 kPa. A programmed short-term delivery of desired liquid volumes in separate batches shows that the volumes are delivered into air and PBS solution with maximum percentage errors of 7.49% and 7.91%, respectively. Additionally, a programmed 3-day long-term reliability test shows that the device was able to achieve desired flow rate values between 160 and 320 μL/day in air and PBS solution with a maximum percentage error of 3.11% and 4.39%, respectively. The results show that the developed device has high potential to be used in drug delivery applications.

Metamodel-based Optimization of a PID Controller Parameters for a Coupled-tank System, Jul 1, 2018

Liquid flow and level control are essential requirements in various industries, such as paper man... more Liquid flow and level control are essential requirements in various industries, such as paper manufacturing, petrochemical industries, waste management, and others. Controlling the liquids flow and levels in such industries is challenging due to the existence of nonlinearity and modeling uncertainties of the plants. This paper presents a method to control the liquid level in a second tank of a coupled-tank plant through variable manipulation of a water pump in the first tank. The optimum controller parameters of this plant are calculated using radial basis function neural network metamodel. A time-varying nonlinear dynamic model is developed and the corresponding linearized perturbation models are derived from the nonlinear model. The performance of the developed optimized controller using metamodeling is compared with the original large space design. In addition, linearized perturbation models are derived from the nonlinear dynamic model with time-varying parameters.

Optimal Two-Degree-of-Freedom Control for Precise Positioning of a Piezo-Actuated Stage, Dec 31, 2017

Microelectromechanical systems (MEMS) based positioning stages are composed of a piezoelectric ac... more Microelectromechanical systems (MEMS) based positioning stages are composed of a piezoelectric actuator (PEA) and a positioning mechanism. Hysteresis is one of the major factors that limit the positional accuracy of piezo-actuated stages. This paper presents a novel method for designing a two-degree-of-freedom (2DOF) controller for precise positioning of a MEMS-based piezo-actuated stage, where Bouc-Wen hysteresis model is used to represent the hysteresis behavior of the PEA. A Luenberger observer-based feed-forward controller is designed, and then integrated with a Particle Swarm Optimization (PSO)-based Proportional-Integral-Derivative (PID) controller to form a 2DOF controller. Optimal PID gains are obtained based on a new fitness function proposed to reduce the displacement error and achieve a fast response time. The results show that using the proposed 2DOF controller reduces the error to be in the range of 0.03 – 1.31% of the maximum displacement when the system is operated in the range of 1 – 50 Hz.

Frequency-Controlled Wireless Passive Thermopneumatic Micromixer, Apr 24, 2017

This paper reports a novel wireless control of a thermopneumatic zigzag micromixer achieved by se... more This paper reports a novel wireless control of a thermopneumatic zigzag micromixer achieved by selectively activating two passive wireless heaters enabled by an external radiofrequency magnetic field. The two heaters, which are designed to have different resonant frequency (fr) values of 100 and 130 MHz, are selectively activated by modulating the field frequency to their corresponding fr values. Each heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element, while the solutions pumped from each reservoir are mixed in a zigzag micromixing element that ends with an outlet hole. Mixing is achieved in a relatively short mixing length of a 2 mm, and was investigated over a low range of Reynold's number (Re) ≤ 10 that is suitable various biomedical applications. The numerically simulated and measured results of the proposed micromixer have shown mixing efficiencies values higher than 82% for the whole range of Re. The optimal activation switching time of the heaters is 10 s, at which the micromixer achieves a steady value of the maximum mixing efficiency after ~65 s. The micromixer provides mixing-ratio controllability with a maximum flow rate and pressure drop of ~3.4 μL/min and ~385.22 Pa, respectively.

Design and fabrication of a novel XYθz monolithic micro-positioning stage driven by NiTi shape-memory-alloy actuators, Sep 16, 2016

This paper reports a new shape-memory-alloy (SMA) micro-positioning stage. The device has been mo... more This paper reports a new shape-memory-alloy (SMA) micro-positioning stage. The device has been monolithically micro-machined with a single fabrication step. The design comprises a moving stage that is manipulated by six SMA planar springs actuators to generate movements with three degrees of freedom. The overall design is square in shape and has dimensions of 12 mm × 12 mm × 0.25 mm. Localized thermomechanical training for shape setting of SMA planar springs was performed using electrical current induced heating at restrained condition to individually train each of the six actuators to memorize a predetermined shape. For actuation, each SMA actuator is individually driven using Joule heating induced by an electrical current. The current flow is controlled by an external pulse-width modulation signal. The thermal response and heat distribution were simulated and experimentally verified using infrared imaging. The micro-positioning results indicated maximum stage movements of 1.2 and 1.6 mm along the x- and y-directions, respectively. Rotational movements were also demonstrated with a total range of 20°. The developed micro-positioning device has been successfully used to move a small object for microscopic scanning applications.

Development of a shape-memory-alloy micromanipulator based on integrated bimorph microactuators, Jun 16, 2016

This paper reports a novel structure of a shape-memory-alloy (SMA) micromanipulator with gripping... more This paper reports a novel structure of a shape-memory-alloy (SMA) micromanipulator with gripping mechanism. A featured integration of multiple SMA bimorph microactuators has been utilized to form a micromanipulator with three degrees of freedom. The design consists of two links (SMA sheets) and a gripper at the end of the second joint. The overall dimensions of the micromanipulator are 33 mm × 9 mm × 3 mm. The displacement of each actuator is controlled by a heating circuit that generates a pulse-width modulation signal. Theoretical modeling of SMA actuators is studied and verified with simulation. The SMA micromanipulator is able to move in the x- and y-axis by 7.1 mm and 5.2 mm, respectively, resulting in a maximum displacement of 8.9 mm. The micro-gripper has a maximum opening gap between its fingers of 1.15 mm. The micromanipulator has a temporal response of 7.5 s and 9 s for its x- and y-axis. The maximum actuation force generated by the x- and y-axis was around 100 mN and 130 mN, respectively. The developed micromanipulator has been successfully used to move a small object.

Thermomechanical behavior of bulk NiTi shape‑memory‑alloy microactuators based on bimorph actuation, Jul 7, 2015

Shape-memory-alloy (SMA) has attracted considerable attention in recent years as a smart and effi... more Shape-memory-alloy (SMA) has attracted considerable attention in recent years as a smart and efficient material, due to its unique properties. SMA microactuators became one of the potential solutions for unresolved issues in microelectromechanical systems (MEMS). This paper presents a thermomechanical behavior analysis of bimorph SMA structure and studies the effect of varying the SMA layer thickness, the type of stress layer and its thickness, and the processing temperature on the displacement of the microactuator. Furthermore, the analyzed results were verified by experimental work, where the fabrication of the SMA microactuators followed the standards of the MEMS fabrication process. SiO2, Si3N4 and Poly-Si were used as stress layers. The fabrication results showed that the bimorph SMA structure achieved maximum displacement when SiO2 was used. The SMA structure with dimensions of 10 mm (length) × 2 mm (width) × 80 µm (thickness), had maximum displacement of 804 µm when 4.1 µm of SiO2 layer was deposited at a temperature of 400 °C.

Thermal analysis of wirelessly powered thermo-pneumatic micropump based on planar LC circuit, Jun 30, 2016

This paper studies the thermal behavior of a wireless powered micropump operated using thermo-pne... more This paper studies the thermal behavior of a wireless powered micropump operated using thermo-pneumatic actuation. Numerical analysis was performed to investigate the temporal conduction of the planar inductor-capacitor (LC) wireless heater and the heating chamber. The result shows that the temperature at the heating chamber reaches steady state temperature of 46.7°C within 40 seconds. The finding was further verified with experimental works through the fabrication of the planar LC heater (RF sensitive actuator) and micropump device using MEMS fabrication technique. The fabricated device delivers a minimum volume of 0.096 μL at the temperature of 29°C after being thermally activated for 10 s. The volume dispensed from the micropump device can precisely controlled by an increase of the electrical heating power within the cut-off input power of 0.22 W. Beyond the power, the heat transfer to the heating chamber exhibits non-linear behavior. In addition, wireless operation of the fabricated device shows successful release of color dye when the micropump is immersed in DI-water containing dish and excited by tuning the RF power.

Wireless powered thermo-pneumatic micropump using frequency-controlled heater, Jun 22, 2015

This paper reports a novel, wirelessly powered micropump based on thermo-pneumatic actuation usin... more This paper reports a novel, wirelessly powered micropump based on thermo-pneumatic actuation using a frequency-controlled heater. The micropump operates wirelessly through the energy transfer to a frequency-dependent heater, which was placed underneath the heating chamber of the pump. Heat is generated at the wireless heater when the external magnetic field is tuned to the resonant frequency of the heater. The enclosed air in the chamber expands and forces the liquid to flow out from the reservoir. The developed device is able to pump a total volume of 4 ml in a single stroke when the external field frequency is tuned to the resonant frequency of the heater at the output power of 0.22 W. Multiple strokes pumping are feasible to be performed with the volume variation of ∼2.8% between each stroke. Flow rate performance of the micropump ranges from 1.01 μL/min to 5.24 μL/min by manipulating the heating power from 0.07 W to 0.89 W. In addition, numerical simulation was performed to study the influence of the heat transfer to the sample liquid. The presented micropump exclusively offers a promising solution in biomedical implantation devices due to its remotely powered functionality, free from bubble trapping and biocompatible feature.

Resonant Control of a Single-Link Flexible Manipulator, Jan 15, 2014

This paper presents resonant control of a single-link flexible manipulator based on the resonant ... more This paper presents resonant control of a single-link flexible manipulator based on the resonant modes frequencies of the system. A flexible manipulator system is a single-input multi-output (SIMO) system with motor torque as an input and hub angle and the tip deflection as outputs. The previous system which is modeled using the finite element method is considered, and the resonant modes of the system are determined. Two negative feedback controllers are used to control the system. The inner feedback control loop designed using the resonant frequencies adds damping to the system and suppress the vibration effect around the hub angle. For the outer feedback control loop, a proportional integral controller is designed to achieve a zero steady state error so that a precise tip positioning can be achieved. Simulation results are presented and discussed to show the effectiveness of the resonant control scheme.

Dynamic Hysteresis Based Modeling Of Piezoelectric Actuators, Jan 15, 2014

Conference Papers by Marwan Nafea

Detecting Sensor Coordination in a Calibrated Lightning Locating System, 2019

A number of applications use the information from lightning locating systems. Public individuals ... more A number of applications use the information from lightning locating systems. Public individuals rarely have their own lightning detection networks; thus they rely on national Lightning Locating Systems (LLSs) or weather forecasters. Therefore, local LLS is useful for public to warn them as soon as the sensors detect the lightning strike. An accurate location estimation of Cloud to Ground (CG) flashes is required to be obtained by applying available detecting methods. Common lightning locating system (LLS) uses various detection techniques such as Time Difference of Arrival (TDOA), Magnetic Direction Finding (MDF) and interferometry. However, these techniques have their own positive points and disadvantages. Low accuracy, high cost, time synchronization problems are several of these weaknesses. Therefore, calibrating the lightning detecting sensors has direct impact on the accuracy of a LLS. In this study, a calibrated LLS including the cross loop antennas, parallel plate antennas and GPS cards with data loggers have been installed at each of the three stations to capture the waveforms and to save the time stamps of incoming signals for further analyses. The captured waveforms of a real lightning discharge were investigated to measure the accuracy of a calibrated system.

Hybrid PSO-Tuned PID and Hysteresis-Observer Based Control for Piezoelectric Micropositioning Stages, 2019

Piezo-actuated micropositioning stages consist of a piezoelectric actuator that operates a positi... more Piezo-actuated micropositioning stages consist of a piezoelectric actuator that operates a positioning system. Hysteresis nonlinearity is one of the significant variables limiting the positioning precision of these stages. This paper introduces a technique of developing a hybrid controller for a precise positioning tracking of a piezoelectric micropositioning system. Bouc-Wen nonlinear hysteresis model is utilized to denote the hysteresis nonlinear phenomenon of the piezo-actuated system. A hysteresis observer-based feedforward controller is designed based on Luenberger observer. This feedforward controller is then coupled with a particle swarm optimization (PSO)-based proportional-integral-derivative (PID) feedback controller to form a hybrid controller. A new fitness function is used to compute the optimal PID gains. This fitness function is intended to reduce the overshoot, steady-state error, and the rise and settling times. The findings of this work indicate that using the developed controller structure can significantly decrease the hysteresis effect. In addition, the proposed structure shows the ability to reduce the error is to 0.046% of the maximum displacement range. Such performance demonstrates that the proposed hybrid control structure is efficient for precise micropositioning applications.

Geometrical Analysis of Diffuser-Nozzle Elements for Valveless Micropumps, 2019

This paper reports a geometrical analysis and tuning-approach for diffuser-nozzle elements for va... more This paper reports a geometrical analysis and tuning-approach for diffuser-nozzle elements for valveless micropumps. Finite element analysis studies are performed in order to investigate the impact of the angle, curvature ratio, and length of the diffuser on the pumping efficiency. Parametric sweep studies are implemented at Reynolds number (Re) values ranging from 10 to 100 while observing the pressure coefficients in the nozzle and diffuser directions, as well as the flow separation and the resultant efficiency of the diffuser. The results suggest that a diffuser with an angle of 10° and a curvature ratio of 0.4 possesses the highest efficiency among the other diffusers within the Re range of this study. In addition, it is observed that the length of the diffuser has a positive effect on the efficiency, where the length is usually restricted by the overall size of the device. The results provide comprehensive designing guidelines for diffusers elements that can be used in microfluidic devices for various biomedical applications.

PDMS-based Dual-Channel Pneumatic Microactuator Using Sacrificial Molding Fabrication Technique, 2019

This paper presents a novel polydimethylsiloxane-based dual-channel bellows-structured pneumatic ... more This paper presents a novel polydimethylsiloxane-based dual-channel bellows-structured pneumatic actuator, fabricated through sacrificial molding technique. A finite element analysis was performed to find the optimum structure and analyze the bending performance of the square-bellows actuator. The actuator was fabricated using acrylonitrile butadiene-styrene-based sacrificial mold to form the channel and bellow structures with an overall actuator size of 5 × 5 × 27.6 mm 3 . The experimental validation has revealed that the actuator attained a smooth bi-directional bending motion with maximum angles of -25° and 35° and force of -0.168 and 0.212 N under left and right channel actuation, respectively, at 100 kPa pressure. Hence, the state-of-the-art dual channels square-bellows actuator was able to achieve an optimum bi-directional bending with low input pressure, which would push the boundaries of soft robotics towards the development of more safe and flexible robotic surgical tools.