RF and Microwave Conference, 2006. RFM 2006. International, 2006
The last decade has seen an unprecedented rise in the usage of mobile phone technology. This sudd... more The last decade has seen an unprecedented rise in the usage of mobile phone technology. This sudden technological shift has confused and concerned the general public over potential health risks due to electromagnetic field (EMF) radiation. This uncertainty is largely due to unfamiliarity with the technological concepts involved, and is best addressed via education. In this paper, we will introduce the efforts of the World Health Organization (WHO) and the University of Malaya, Malaysia, to design and implement a Web-based educational portal on EMF for children. This portal uses Macromediareg Flashreg, and utilizes multimedia and interactive exhibits as well as simple instructional language and concepts to introduce the curriculum
3rd Kuala Lumpur International Conference on Biomedical Engineering 2006, 2007
The temperature model of therapeutic ultrasound for human tissue is important in order to design ... more The temperature model of therapeutic ultrasound for human tissue is important in order to design an accurate instrumental assessment and calibration of therapeutic ultrasound device. The focus of this study is to verify temperature effects of ultrasound on tissues and explore the possibility of proposing a preliminary temperature model. A series of experiment had been conducted to clarify the relationship between output intensity and site of target tissue with temperature change in a phantom-tissue model for 10 minutes exposure of 3 MHz therapeutic ultrasound. It was found that 3 MHz ultrasound provided effectual heating at the superficial tissue, which is 1 cm from surface. It was also found that the experimental data had provided the necessary evidence for the development of preliminary temperature model. The temperature model had been produced by selecting suitable trend line for the graph of experimental data particularly for the temperature change at site of 1 cm from tissue surface. In conclusion, the preliminary finding of this study is the temperature effect of therapeutic ultrasound in homogeneous phantomtissue model has a suitable pattern to be modeled into a simple mathematical equation. This study also proposed further study to develop more reliable and holistic evidence-based temperature model.
5th Kuala Lumpur International Conference on Biomedical Engineering 2011, 2011
Dielectrophoresis is an electrical phenomenon that occurs when a polarisable particle is placed i... more Dielectrophoresis is an electrical phenomenon that occurs when a polarisable particle is placed in non-uniform electrical fields. The magnitude of the generated force is dependent upon the electrophysiological make-up of the particle, therefore the specific DEP profile may be attained for any polarisable particles based on the intrinsic electrical properties alone. Any changes to these parameters may be detected by observing the corresponding DEP spectra. Despite having the advantages of being non-invasive, DEP applications are still not widely used due to the time-consuming processes involved.
This study presents the preliminary outcomes in the development of a semi-automated DEP-based cell characterisation tool that allowed concurrent DEP experiments to be conducted serially, thus significantly reducing the time taken to complete the required sets of experiments. The results showed that the system is capable of producing a DEP spectrum for K562 leukaemic cells between the 10 kHz to 1 MHz range in less than 10 minutes, when recorded at eight points per decade.
When biij came into being in early 2005, it was
envisioned as a tool for the dissemination of sc... more When biij came into being in early 2005, it was
envisioned as a tool for the dissemination of scientific
knowledge. Today, biij continues to fulfill this role,
having gone through a process of evolution and growth.
In the early days [1], the email system was the main
means of communication. All manuscript submissions,
including its figures and images, were sent as email
attachments to the managing editor. The subsequent
reviewing stages were also done via email. To simplify
the tracking process, the managing editor developed an
in-house software to view and update the status of each
of the submitted manuscripts. It was developed using the
Active Server Pages (ASP) programming language and a
Microsoft Access database, and is only viewable by the
editors. Although the software served its purpose well,
the journal has grown so much so that its requirements
for additional features far outweigh the resources that
were currently available.
Dielectrophoresis (DEP) has been used for many years for the analysis of the electrophysiological... more Dielectrophoresis (DEP) has been used for many years for the analysis of the electrophysiological properties of cells. However, such analyses have in the past been time-consuming, such that it can take 30 min or more to collect sufficient data to make valid interpretations from a single DEP spectrum. This has limited the application of the technology to a rapid tool for non-invasive, label-free research in areas from drug discovery to diagnostics. In this paper we present the development of a programmable, multi-channel DEP system for rapid biophysical assessment of populations of biological cells. A new assay format has been developed for continuous near-real-time monitoring, using simultaneous application of up to eight alternating current electrical signals to independently addressable dot microelectrodes in an array format, allowing a DEP spectrum to be measured in 20 s, with a total cycle time between measurements of 90 s. To demonstrate the system, human leukaemic K562 cells were monitored after exposure to staurosporine and valinomycin. The DEP response curves showed the timing and manner in which the membrane properties changed for the actions of these two drugs at the early phase of induction. This technology shows the great potential for increasing our understanding of the role of electrophysiology in drug action, by observing the changes in electrical characteristics as they occur.
3rd Kuala Lumpur International Conference on Biomedical Engineering 2006, 2007
Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tu... more Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tumors with rich macroscopic and microscopic blood supply. The main risks related to this procedure are bleeding and implantation of tumor cells in the needle tract. From numerous conducted studies, it was found that heating the needle tract using a radiofrequency (RF) ablation system has a potential to minimize these effects. However, this solution requires the use of specially designed RF needles which would make the procedure relatively expensive and complicated. Thus, in order to solve this problem, we propose a simple solution by using readily available biopsy needles connected to an RF generator. In order to do so, we have designed and developed an adapter to interface between these two devices. A bovine liver has been used as a sample tissue for the experimental procedure. The delivery of the RF was varied by varying the values for delivered power, power delivery duration, and insertion depth. The results showed that the size of the coagulation necrosis region is affected by all of the parameters tested. In general, the size of the region is enlarged with higher delivery of RF power, longer duration of power delivery, and shallower needle insertion.
Polyvinyl alcohol (PVA) membranes have long been used in many applications, most notably in a num... more Polyvinyl alcohol (PVA) membranes have long been used in many applications, most notably in a number of recent biomedical applications. These applications include the encapsulation of hybrid-type artificial organs,1-3 the controlled release of specific molecules,4,5 targeted drug delivery systems,6,7 enhanced wound dressings,8,9 and myriad other applications that utilize the semi-permeability and high biocompatibility of PVA. Nevertheless, prior to its designation for use as the biomaterial of choice in the design and development processes of artificial tissue fabrication applications, the exact nature of PVA's physiological properties needs to be ascertained. In particular, the permeability and the diffusion coefficient are two important parameters that need to be analyzed. The experimental results can subsequently be used to determine the appropriate fabrication technique and design geometry for the design and development of the required tissue engineering applications.
RF and Microwave Conference, 2006. RFM 2006. International , 2006
An ongoing global online survey was initiated in October 2005 to compile and analyse information ... more An ongoing global online survey was initiated in October 2005 to compile and analyse information on the understanding of mobile phone technology and EMF among school children. Since November 2005 and till July 23, 2006, a total of 1,711 responses were recorded from 60 countries. The number of male respondents (n = 653, 38.2%) roughly equalled the female (n = 626, 36.6%), with an average age of 14.0 (plusmn2.8 SD) years. Almost 60% of the respondents do not own a mobile phone; and almost 60% of the respondents admitted that they did not know that mobile phones use EMF to function. Roughly two-thirds of the respondents also reported to not knowing that mobile phones can cause harmful effects. Out of those who believed so, a majority reported headache as the main problem
Biomedical Engineering and Sciences (IECBES), 2012 IEEE EMBS Conference on, 2012
Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophys... more Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophysiological properties of bioparticles by applying non-uniform electric fields generated through special electrodes. Various electrode geometries have been developed to address different applications. Simulation of the electric field strength over electrodes is essential in order to optimize the generated DEP force for enhancing cell manipulation. This paper describes the study of electric field distribution over planar multiple microarray dot electrode using numerical modeling of Comsol Multiphysics 4.2a®. Results show that the electric field strength is axisymmetrical around the centre of the dot aperture and that is higher at the dot edges than the dot centers. Further studies will be conducted to investigate the effect of applying different frequencies, varying dots size and adding ground plane in between the electrode dots.
Biomedical Engineering and Sciences (IECBES), 2012 IEEE EMBS Conference on, 2012
Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophys... more Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophysiological properties of bioparticles by applying non-uniform electric fields generated through special electrodes. Various electrode geometries have been developed to address different applications. Simulation of the electric field strength over electrodes is essential in order to optimize the generated DEP force for enhancing cell manipulation. This paper describes the study of electric field distribution over planar multiple microarray dot electrode using numerical modeling of Comsol Multiphysics 4.2a®. Results show that the electric field strength is axisymmetrical around the centre of the dot aperture and that is higher at the dot edges than the dot centers. Further studies will be conducted to investigate the effect of applying different frequencies, varying dots size and adding ground plane in between the electrode dots.
International Journal of Electrochemical Science, 2012
Physical manipulation of polarizable particles generated by the transient force when placed in no... more Physical manipulation of polarizable particles generated by the transient force when placed in non-uniform electrical fields is termed dielectrophoresis. The electrophysiological make-up of the particle and the surrounding medium decides the magnitude of the force; hence specific DEP profile may be acquired for any polarizable particles based on the electrical properties of the membrane and cytoplasm alone. Any changes to these parameters may be detected, in turn, by observing the corresponding DEP spectra. The reason DEP is not applied widely in spite of its non-invasiveness primarily is that the process is time consuming. The proposed DEP-based lab-on-chip application of semi-automated cell electrophysiology characterization allowed concurrent DEP experiments to be conducted serially, which significantly reduced the required experiment time. This capability is achieved via the employment of a planar microelectrode with modified dot microarray geometry. The results showed that the system is capable of producing a complete DEP spectrum profile for K562 leukemic cells between the 1 kHz to 1 MHz frequency range in less than 10 minutes.
During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulat... more During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulation and characterization due to its non-invasiveness. It is very useful in the trend towards point-of-care systems. Currently, most efforts are focused on using DEP in biomedical applications, such as the spatial manipulation of cells, the selective separation or enrichment of target cells, high-throughput molecular screening, biosensors and immunoassays. A significant amount of research on DEP has produced a wide range of microelectrode configurations. In this paper; we describe the microarray dot electrode, a promising electrode geometry to characterize and manipulate cells via DEP. The advantages offered by this type of microelectrode are also reviewed. The protocol for fabricating planar microelectrodes using photolithography is documented to demonstrate the fast and cost-effective fabrication process. Additionally; different state-of-the-art Lab-on-a-Chip (LOC) devices that have been proposed for DEP applications in the literature are reviewed. We also present our recently designed LOC device, which uses an improved microarray dot electrode configuration to address the challenges facing other devices. This type of LOC system has the capability to boost the implementation of DEP technology in practical settings such as clinical cell sorting, infection diagnosis, and enrichment of particle populations for drug development.
Journal of the Mechanical Behavior of Biomedical Materials, 2013
The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ce... more The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000 °C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0–50 w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150 °C and 1250 °C with a 5 h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15 wt% of Al2O3 powder at 1250 °C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500–700 nm after sintering process.
International Journal of Electrochemical Science, Apr 1, 2012
Ni and Al elemental powder mixtures with composition Ni75Al25 (at %) were mechanically alloyed in... more Ni and Al elemental powder mixtures with composition Ni75Al25 (at %) were mechanically alloyed in a planetary ball mill under different mechanical alloying (MA) durations. X-ray diffraction (XRD), scanning electron microscope (SEM) and simultaneous thermal analysis (STA) were conducted to study phase transformations, morphology changes and thermal property of Ni-Al mixture during MA. Ni3Al intermetallic compound was formed successfully after 10h of milling, which was the shortest formation period that ever reported for this intermetallic compound. The nanocrystalline Ni3Al with the lowest crystallite size of 12.6nm was synthesized. Refinement of crystallite size with increasing internal strain was significant as milling duration was increased gradually. During formation of the Ni3Al, the powder particles have undergone incidents of welding, microforging, fracturing, rewelding and agglomeration.
Computer Methods and Programs in Biomedicine, Jan 1, 2014
this detection task, in this study, we extracted the heart rate (HR) from the ECG signals and use... more this detection task, in this study, we extracted the heart rate (HR) from the ECG signals and used them as base signal for further analysis. We then analyzed the HR signals of both normal and CAD subjects using (i) time domain, (ii) frequency domain and (iii) nonlinear techniques. The following are the nonlinear methods that were used in this work: Poincare plots, Recurrence Quantification Analysis (RQA) parameters, Shannon entropy, Approximate Entropy (ApEn), Sample Entropy (SampEn), Higher Order Spectra (HOS) methods, Detrended Fluctuation Analysis (DFA), Empirical Mode Decomposition (EMD), Cumulants, and Correlation Dimension. As a result of the analysis, we present unique recurrence, Poincare and HOS plots for normal and CAD subjects. We have also observed significant variations in the range of these features with respect to normal and CAD classes, and have presented the same in this paper. We found that the RQA parameters were higher for CAD subjects indicating more rhythm. Since the activity of CAD subjects is less, similar signal patterns repeat more frequently compared to the normal subjects. The entropy based parameters, ApEn and SampEn, are lower for CAD subjects indicating lower entropy (less activity due to impairment) for CAD. Almost all HOS parameters showed higher values for the CAD group, indicating the presence of higher frequency content in the CAD signals. Thus, our study provides a deep insight into how such nonlinear features could be exploited to effectively and reliably detect the presence of CAD.
4th Kuala Lumpur International Conference on Biomedical Engineering 2008, 2008
The Department of Biomedical Engineering, at the Faculty of Engineering, University of Malaya was... more The Department of Biomedical Engineering, at the Faculty of Engineering, University of Malaya was established in the 1997/1998 academic session with an intake of 20 students and five academic staff. The Department has undergone numerous changes in the structure of its degree programme, with each one of them recognised and fully accredited by the Engineering Accreditation Council and Ministry of Higher Education. The Department has played an active role at national and global levels, in the areas of biomedical engineering education and research collaboration. Several initiatives have been planned to ensure the Department stays at the forefront of disseminating biomedical engineering innovations in Malaysia.
Calcium silicate hydrate (CSH) consisting of nanosheets has been successfully synthesized assiste... more Calcium silicate hydrate (CSH) consisting of nanosheets has been successfully synthesized assisted by a tip ultrasonic irradiation (UI) method using calcium nitrate (Ca(NO3)·4H2O), sodium silicate (Na2SiO3·9H2O) and sodium dodecyl sulfate (SDS) in water. Systematic studies found that reaction time of ultrasonic irradiation and concentrations of surfactant (SDS) in the system were important factors to control the crystallite size and morphologies. The products were characterized by X-ray power diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrometry (FTIR). The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the CSH. These characterization techniques revealed the successful formation of a crystalline phase with an average crystallite size of about 13 nm and nanosheet morphology at a reaction time of 10 min UI with 0.2 g SDS in solvent which were found to be optimum time and concentrations of SDS for the synthesis of CSH powders.
Journal of the Mechanical Behavior of Biomedical Materials, 2012
This study describes the synthesis of Al2O3/SiC/ZrO2 functionally graded material (FGM) in bio-im... more This study describes the synthesis of Al2O3/SiC/ZrO2 functionally graded material (FGM) in bio-implants (artificial joints) by electrophoretic deposition (EPD). A suitable suspension that was based on 2-butanone was applied for the EPD of Al2O3/SiC/ZrO2, and a pressureless sintering process was applied as a presintering. Hot isostatic pressing (HIP) was used to densify the deposit, with beneficial mechanical properties after 2 h at 1800 degrees C in Ar atmosphere. The maximum hardness in the outer layer (90 vol.% Al2O3 + 10 vol.% SiC) and maximum fracture toughness in the core layer (75 vol.% Al2O3 + 10 vol.% SiC + 15 vol.% ZrO2) composite were 20.8 +/- 0.3 GPa and 8 +/- 0.1 MPa m(1/2), respectively.
The results, when compared with results from Al2O3/ZrO2 FGM, showed that SiC increased the compressive stresses in the outer layers, while the inner layers were under a residual tensile stress. (C) 2012 Elsevier Ltd. All rights reserved.
World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China
Lab-on-chip devices have been proven to be advantageous in terms of selective collection, manipu... more Lab-on-chip devices have been proven to be advantageous in terms of selective collection, manipulation and separation of cells and particles. Numerous physical methods have been employed in the development of such devices, and alternating current (AC) electrokinetics was one of the chosen techniques due to its selectivity, efficacy, noninvasiveness, and low fabrication costs. Recently it has been shown that, by employing a specific AC electrokinetics technique called dielectrophoresis, it was possible to fabricate an addressable microarray dots in creating axisymmetrical AC fields over a planar microelectrode within a chamber containing the cell sample. Each of these dots received different input frequency values in order to create the required field with specific gradient strength, thus enabling dielectrophoretic experiments to take place in rapid succession. The objective of this study is to simulate the generation of the said electromagnetic fluxes over the microarray dots using finite element methods. Materials and Methods: Three different materials, namely copper, gold, and indium tin oxide were used, and simulated at different input frequencies and environment. Results and Discussion: The results indicate that the generated AC electric fields are satisfactory in creating the required DEP effects within a chamber height of 200 μm. Different electrode materials and environment produced no significant difference (p >0.05) in terms of the maximum and minimum electrical gradient strengths. Further investigation with regards to the optimal distance in between the dots is warranted in order to create consistent dielectrophoretic effects with optimal particle density.
RF and Microwave Conference, 2006. RFM 2006. International, 2006
The last decade has seen an unprecedented rise in the usage of mobile phone technology. This sudd... more The last decade has seen an unprecedented rise in the usage of mobile phone technology. This sudden technological shift has confused and concerned the general public over potential health risks due to electromagnetic field (EMF) radiation. This uncertainty is largely due to unfamiliarity with the technological concepts involved, and is best addressed via education. In this paper, we will introduce the efforts of the World Health Organization (WHO) and the University of Malaya, Malaysia, to design and implement a Web-based educational portal on EMF for children. This portal uses Macromediareg Flashreg, and utilizes multimedia and interactive exhibits as well as simple instructional language and concepts to introduce the curriculum
3rd Kuala Lumpur International Conference on Biomedical Engineering 2006, 2007
The temperature model of therapeutic ultrasound for human tissue is important in order to design ... more The temperature model of therapeutic ultrasound for human tissue is important in order to design an accurate instrumental assessment and calibration of therapeutic ultrasound device. The focus of this study is to verify temperature effects of ultrasound on tissues and explore the possibility of proposing a preliminary temperature model. A series of experiment had been conducted to clarify the relationship between output intensity and site of target tissue with temperature change in a phantom-tissue model for 10 minutes exposure of 3 MHz therapeutic ultrasound. It was found that 3 MHz ultrasound provided effectual heating at the superficial tissue, which is 1 cm from surface. It was also found that the experimental data had provided the necessary evidence for the development of preliminary temperature model. The temperature model had been produced by selecting suitable trend line for the graph of experimental data particularly for the temperature change at site of 1 cm from tissue surface. In conclusion, the preliminary finding of this study is the temperature effect of therapeutic ultrasound in homogeneous phantomtissue model has a suitable pattern to be modeled into a simple mathematical equation. This study also proposed further study to develop more reliable and holistic evidence-based temperature model.
5th Kuala Lumpur International Conference on Biomedical Engineering 2011, 2011
Dielectrophoresis is an electrical phenomenon that occurs when a polarisable particle is placed i... more Dielectrophoresis is an electrical phenomenon that occurs when a polarisable particle is placed in non-uniform electrical fields. The magnitude of the generated force is dependent upon the electrophysiological make-up of the particle, therefore the specific DEP profile may be attained for any polarisable particles based on the intrinsic electrical properties alone. Any changes to these parameters may be detected by observing the corresponding DEP spectra. Despite having the advantages of being non-invasive, DEP applications are still not widely used due to the time-consuming processes involved.
This study presents the preliminary outcomes in the development of a semi-automated DEP-based cell characterisation tool that allowed concurrent DEP experiments to be conducted serially, thus significantly reducing the time taken to complete the required sets of experiments. The results showed that the system is capable of producing a DEP spectrum for K562 leukaemic cells between the 10 kHz to 1 MHz range in less than 10 minutes, when recorded at eight points per decade.
When biij came into being in early 2005, it was
envisioned as a tool for the dissemination of sc... more When biij came into being in early 2005, it was
envisioned as a tool for the dissemination of scientific
knowledge. Today, biij continues to fulfill this role,
having gone through a process of evolution and growth.
In the early days [1], the email system was the main
means of communication. All manuscript submissions,
including its figures and images, were sent as email
attachments to the managing editor. The subsequent
reviewing stages were also done via email. To simplify
the tracking process, the managing editor developed an
in-house software to view and update the status of each
of the submitted manuscripts. It was developed using the
Active Server Pages (ASP) programming language and a
Microsoft Access database, and is only viewable by the
editors. Although the software served its purpose well,
the journal has grown so much so that its requirements
for additional features far outweigh the resources that
were currently available.
Dielectrophoresis (DEP) has been used for many years for the analysis of the electrophysiological... more Dielectrophoresis (DEP) has been used for many years for the analysis of the electrophysiological properties of cells. However, such analyses have in the past been time-consuming, such that it can take 30 min or more to collect sufficient data to make valid interpretations from a single DEP spectrum. This has limited the application of the technology to a rapid tool for non-invasive, label-free research in areas from drug discovery to diagnostics. In this paper we present the development of a programmable, multi-channel DEP system for rapid biophysical assessment of populations of biological cells. A new assay format has been developed for continuous near-real-time monitoring, using simultaneous application of up to eight alternating current electrical signals to independently addressable dot microelectrodes in an array format, allowing a DEP spectrum to be measured in 20 s, with a total cycle time between measurements of 90 s. To demonstrate the system, human leukaemic K562 cells were monitored after exposure to staurosporine and valinomycin. The DEP response curves showed the timing and manner in which the membrane properties changed for the actions of these two drugs at the early phase of induction. This technology shows the great potential for increasing our understanding of the role of electrophysiology in drug action, by observing the changes in electrical characteristics as they occur.
3rd Kuala Lumpur International Conference on Biomedical Engineering 2006, 2007
Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tu... more Percutaneous image-guided needle biopsy is typically performed in highly vascular organs or in tumors with rich macroscopic and microscopic blood supply. The main risks related to this procedure are bleeding and implantation of tumor cells in the needle tract. From numerous conducted studies, it was found that heating the needle tract using a radiofrequency (RF) ablation system has a potential to minimize these effects. However, this solution requires the use of specially designed RF needles which would make the procedure relatively expensive and complicated. Thus, in order to solve this problem, we propose a simple solution by using readily available biopsy needles connected to an RF generator. In order to do so, we have designed and developed an adapter to interface between these two devices. A bovine liver has been used as a sample tissue for the experimental procedure. The delivery of the RF was varied by varying the values for delivered power, power delivery duration, and insertion depth. The results showed that the size of the coagulation necrosis region is affected by all of the parameters tested. In general, the size of the region is enlarged with higher delivery of RF power, longer duration of power delivery, and shallower needle insertion.
Polyvinyl alcohol (PVA) membranes have long been used in many applications, most notably in a num... more Polyvinyl alcohol (PVA) membranes have long been used in many applications, most notably in a number of recent biomedical applications. These applications include the encapsulation of hybrid-type artificial organs,1-3 the controlled release of specific molecules,4,5 targeted drug delivery systems,6,7 enhanced wound dressings,8,9 and myriad other applications that utilize the semi-permeability and high biocompatibility of PVA. Nevertheless, prior to its designation for use as the biomaterial of choice in the design and development processes of artificial tissue fabrication applications, the exact nature of PVA's physiological properties needs to be ascertained. In particular, the permeability and the diffusion coefficient are two important parameters that need to be analyzed. The experimental results can subsequently be used to determine the appropriate fabrication technique and design geometry for the design and development of the required tissue engineering applications.
RF and Microwave Conference, 2006. RFM 2006. International , 2006
An ongoing global online survey was initiated in October 2005 to compile and analyse information ... more An ongoing global online survey was initiated in October 2005 to compile and analyse information on the understanding of mobile phone technology and EMF among school children. Since November 2005 and till July 23, 2006, a total of 1,711 responses were recorded from 60 countries. The number of male respondents (n = 653, 38.2%) roughly equalled the female (n = 626, 36.6%), with an average age of 14.0 (plusmn2.8 SD) years. Almost 60% of the respondents do not own a mobile phone; and almost 60% of the respondents admitted that they did not know that mobile phones use EMF to function. Roughly two-thirds of the respondents also reported to not knowing that mobile phones can cause harmful effects. Out of those who believed so, a majority reported headache as the main problem
Biomedical Engineering and Sciences (IECBES), 2012 IEEE EMBS Conference on, 2012
Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophys... more Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophysiological properties of bioparticles by applying non-uniform electric fields generated through special electrodes. Various electrode geometries have been developed to address different applications. Simulation of the electric field strength over electrodes is essential in order to optimize the generated DEP force for enhancing cell manipulation. This paper describes the study of electric field distribution over planar multiple microarray dot electrode using numerical modeling of Comsol Multiphysics 4.2a®. Results show that the electric field strength is axisymmetrical around the centre of the dot aperture and that is higher at the dot edges than the dot centers. Further studies will be conducted to investigate the effect of applying different frequencies, varying dots size and adding ground plane in between the electrode dots.
Biomedical Engineering and Sciences (IECBES), 2012 IEEE EMBS Conference on, 2012
Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophys... more Dielectrophoresis (DEP) has been proven as a method of manipulating and analyzing the electrophysiological properties of bioparticles by applying non-uniform electric fields generated through special electrodes. Various electrode geometries have been developed to address different applications. Simulation of the electric field strength over electrodes is essential in order to optimize the generated DEP force for enhancing cell manipulation. This paper describes the study of electric field distribution over planar multiple microarray dot electrode using numerical modeling of Comsol Multiphysics 4.2a®. Results show that the electric field strength is axisymmetrical around the centre of the dot aperture and that is higher at the dot edges than the dot centers. Further studies will be conducted to investigate the effect of applying different frequencies, varying dots size and adding ground plane in between the electrode dots.
International Journal of Electrochemical Science, 2012
Physical manipulation of polarizable particles generated by the transient force when placed in no... more Physical manipulation of polarizable particles generated by the transient force when placed in non-uniform electrical fields is termed dielectrophoresis. The electrophysiological make-up of the particle and the surrounding medium decides the magnitude of the force; hence specific DEP profile may be acquired for any polarizable particles based on the electrical properties of the membrane and cytoplasm alone. Any changes to these parameters may be detected, in turn, by observing the corresponding DEP spectra. The reason DEP is not applied widely in spite of its non-invasiveness primarily is that the process is time consuming. The proposed DEP-based lab-on-chip application of semi-automated cell electrophysiology characterization allowed concurrent DEP experiments to be conducted serially, which significantly reduced the required experiment time. This capability is achieved via the employment of a planar microelectrode with modified dot microarray geometry. The results showed that the system is capable of producing a complete DEP spectrum profile for K562 leukemic cells between the 1 kHz to 1 MHz frequency range in less than 10 minutes.
During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulat... more During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulation and characterization due to its non-invasiveness. It is very useful in the trend towards point-of-care systems. Currently, most efforts are focused on using DEP in biomedical applications, such as the spatial manipulation of cells, the selective separation or enrichment of target cells, high-throughput molecular screening, biosensors and immunoassays. A significant amount of research on DEP has produced a wide range of microelectrode configurations. In this paper; we describe the microarray dot electrode, a promising electrode geometry to characterize and manipulate cells via DEP. The advantages offered by this type of microelectrode are also reviewed. The protocol for fabricating planar microelectrodes using photolithography is documented to demonstrate the fast and cost-effective fabrication process. Additionally; different state-of-the-art Lab-on-a-Chip (LOC) devices that have been proposed for DEP applications in the literature are reviewed. We also present our recently designed LOC device, which uses an improved microarray dot electrode configuration to address the challenges facing other devices. This type of LOC system has the capability to boost the implementation of DEP technology in practical settings such as clinical cell sorting, infection diagnosis, and enrichment of particle populations for drug development.
Journal of the Mechanical Behavior of Biomedical Materials, 2013
The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ce... more The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000 °C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0–50 w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150 °C and 1250 °C with a 5 h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15 wt% of Al2O3 powder at 1250 °C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500–700 nm after sintering process.
International Journal of Electrochemical Science, Apr 1, 2012
Ni and Al elemental powder mixtures with composition Ni75Al25 (at %) were mechanically alloyed in... more Ni and Al elemental powder mixtures with composition Ni75Al25 (at %) were mechanically alloyed in a planetary ball mill under different mechanical alloying (MA) durations. X-ray diffraction (XRD), scanning electron microscope (SEM) and simultaneous thermal analysis (STA) were conducted to study phase transformations, morphology changes and thermal property of Ni-Al mixture during MA. Ni3Al intermetallic compound was formed successfully after 10h of milling, which was the shortest formation period that ever reported for this intermetallic compound. The nanocrystalline Ni3Al with the lowest crystallite size of 12.6nm was synthesized. Refinement of crystallite size with increasing internal strain was significant as milling duration was increased gradually. During formation of the Ni3Al, the powder particles have undergone incidents of welding, microforging, fracturing, rewelding and agglomeration.
Computer Methods and Programs in Biomedicine, Jan 1, 2014
this detection task, in this study, we extracted the heart rate (HR) from the ECG signals and use... more this detection task, in this study, we extracted the heart rate (HR) from the ECG signals and used them as base signal for further analysis. We then analyzed the HR signals of both normal and CAD subjects using (i) time domain, (ii) frequency domain and (iii) nonlinear techniques. The following are the nonlinear methods that were used in this work: Poincare plots, Recurrence Quantification Analysis (RQA) parameters, Shannon entropy, Approximate Entropy (ApEn), Sample Entropy (SampEn), Higher Order Spectra (HOS) methods, Detrended Fluctuation Analysis (DFA), Empirical Mode Decomposition (EMD), Cumulants, and Correlation Dimension. As a result of the analysis, we present unique recurrence, Poincare and HOS plots for normal and CAD subjects. We have also observed significant variations in the range of these features with respect to normal and CAD classes, and have presented the same in this paper. We found that the RQA parameters were higher for CAD subjects indicating more rhythm. Since the activity of CAD subjects is less, similar signal patterns repeat more frequently compared to the normal subjects. The entropy based parameters, ApEn and SampEn, are lower for CAD subjects indicating lower entropy (less activity due to impairment) for CAD. Almost all HOS parameters showed higher values for the CAD group, indicating the presence of higher frequency content in the CAD signals. Thus, our study provides a deep insight into how such nonlinear features could be exploited to effectively and reliably detect the presence of CAD.
4th Kuala Lumpur International Conference on Biomedical Engineering 2008, 2008
The Department of Biomedical Engineering, at the Faculty of Engineering, University of Malaya was... more The Department of Biomedical Engineering, at the Faculty of Engineering, University of Malaya was established in the 1997/1998 academic session with an intake of 20 students and five academic staff. The Department has undergone numerous changes in the structure of its degree programme, with each one of them recognised and fully accredited by the Engineering Accreditation Council and Ministry of Higher Education. The Department has played an active role at national and global levels, in the areas of biomedical engineering education and research collaboration. Several initiatives have been planned to ensure the Department stays at the forefront of disseminating biomedical engineering innovations in Malaysia.
Calcium silicate hydrate (CSH) consisting of nanosheets has been successfully synthesized assiste... more Calcium silicate hydrate (CSH) consisting of nanosheets has been successfully synthesized assisted by a tip ultrasonic irradiation (UI) method using calcium nitrate (Ca(NO3)·4H2O), sodium silicate (Na2SiO3·9H2O) and sodium dodecyl sulfate (SDS) in water. Systematic studies found that reaction time of ultrasonic irradiation and concentrations of surfactant (SDS) in the system were important factors to control the crystallite size and morphologies. The products were characterized by X-ray power diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectrometry (FTIR). The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the CSH. These characterization techniques revealed the successful formation of a crystalline phase with an average crystallite size of about 13 nm and nanosheet morphology at a reaction time of 10 min UI with 0.2 g SDS in solvent which were found to be optimum time and concentrations of SDS for the synthesis of CSH powders.
Journal of the Mechanical Behavior of Biomedical Materials, 2012
This study describes the synthesis of Al2O3/SiC/ZrO2 functionally graded material (FGM) in bio-im... more This study describes the synthesis of Al2O3/SiC/ZrO2 functionally graded material (FGM) in bio-implants (artificial joints) by electrophoretic deposition (EPD). A suitable suspension that was based on 2-butanone was applied for the EPD of Al2O3/SiC/ZrO2, and a pressureless sintering process was applied as a presintering. Hot isostatic pressing (HIP) was used to densify the deposit, with beneficial mechanical properties after 2 h at 1800 degrees C in Ar atmosphere. The maximum hardness in the outer layer (90 vol.% Al2O3 + 10 vol.% SiC) and maximum fracture toughness in the core layer (75 vol.% Al2O3 + 10 vol.% SiC + 15 vol.% ZrO2) composite were 20.8 +/- 0.3 GPa and 8 +/- 0.1 MPa m(1/2), respectively.
The results, when compared with results from Al2O3/ZrO2 FGM, showed that SiC increased the compressive stresses in the outer layers, while the inner layers were under a residual tensile stress. (C) 2012 Elsevier Ltd. All rights reserved.
World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China
Lab-on-chip devices have been proven to be advantageous in terms of selective collection, manipu... more Lab-on-chip devices have been proven to be advantageous in terms of selective collection, manipulation and separation of cells and particles. Numerous physical methods have been employed in the development of such devices, and alternating current (AC) electrokinetics was one of the chosen techniques due to its selectivity, efficacy, noninvasiveness, and low fabrication costs. Recently it has been shown that, by employing a specific AC electrokinetics technique called dielectrophoresis, it was possible to fabricate an addressable microarray dots in creating axisymmetrical AC fields over a planar microelectrode within a chamber containing the cell sample. Each of these dots received different input frequency values in order to create the required field with specific gradient strength, thus enabling dielectrophoretic experiments to take place in rapid succession. The objective of this study is to simulate the generation of the said electromagnetic fluxes over the microarray dots using finite element methods. Materials and Methods: Three different materials, namely copper, gold, and indium tin oxide were used, and simulated at different input frequencies and environment. Results and Discussion: The results indicate that the generated AC electric fields are satisfactory in creating the required DEP effects within a chamber height of 200 μm. Different electrode materials and environment produced no significant difference (p >0.05) in terms of the maximum and minimum electrical gradient strengths. Further investigation with regards to the optimal distance in between the dots is warranted in order to create consistent dielectrophoretic effects with optimal particle density.
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Papers by Nahrizul Kadri
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4133623
http://link.springer.com/chapter/10.1007/978-3-540-68017-8_149
This study presents the preliminary outcomes in the development of a semi-automated DEP-based cell characterisation tool that allowed concurrent DEP experiments to be conducted serially, thus significantly reducing the time taken to complete the required sets of experiments. The results showed that the system is capable of producing a DEP spectrum for K562 leukaemic cells between the 10 kHz to 1 MHz range in less than 10 minutes, when recorded at eight points per decade.
http://link.springer.com/chapter/10.1007/978-3-642-21729-6_145
envisioned as a tool for the dissemination of scientific
knowledge. Today, biij continues to fulfill this role,
having gone through a process of evolution and growth.
In the early days [1], the email system was the main
means of communication. All manuscript submissions,
including its figures and images, were sent as email
attachments to the managing editor. The subsequent
reviewing stages were also done via email. To simplify
the tracking process, the managing editor developed an
in-house software to view and update the status of each
of the submitted manuscripts. It was developed using the
Active Server Pages (ASP) programming language and a
Microsoft Access database, and is only viewable by the
editors. Although the software served its purpose well,
the journal has grown so much so that its requirements
for additional features far outweigh the resources that
were currently available.
http://www.biij.org/2009/1/e1/
http://onlinelibrary.wiley.com/doi/10.1002/elps.201100033/full
http://link.springer.com/chapter/10.1007/978-3-540-68017-8_61
http://eprints.um.edu.my/5045/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3161234/
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4133609
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6498060&tag=1
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6498060&tag=1
electrochemsci.org/papers/vol7/7065633.pdf
http://www.mdpi.com/1424-8220/13/7/9029
www.sciencedirect.com/science/article/pii/S1751616113003664
electrochemsci.org/papers/vol7/7043765.pdf
www.sciencedirect.com/science/article/pii/S0169260713002964
http://link.springer.com/chapter/10.1007/978-3-540-69139-6_22
www.sciencedirect.com/science/article/pii/S1350417713001831
The results, when compared with results from Al2O3/ZrO2 FGM, showed that SiC increased the compressive stresses in the outer layers, while the inner layers were under a residual tensile stress. (C) 2012 Elsevier Ltd. All rights reserved.
http://www.sciencedirect.com/science/article/pii/S1751616112001038
http://link.springer.com/chapter/10.1007/978-3-642-29305-4_83
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4133623
http://link.springer.com/chapter/10.1007/978-3-540-68017-8_149
This study presents the preliminary outcomes in the development of a semi-automated DEP-based cell characterisation tool that allowed concurrent DEP experiments to be conducted serially, thus significantly reducing the time taken to complete the required sets of experiments. The results showed that the system is capable of producing a DEP spectrum for K562 leukaemic cells between the 10 kHz to 1 MHz range in less than 10 minutes, when recorded at eight points per decade.
http://link.springer.com/chapter/10.1007/978-3-642-21729-6_145
envisioned as a tool for the dissemination of scientific
knowledge. Today, biij continues to fulfill this role,
having gone through a process of evolution and growth.
In the early days [1], the email system was the main
means of communication. All manuscript submissions,
including its figures and images, were sent as email
attachments to the managing editor. The subsequent
reviewing stages were also done via email. To simplify
the tracking process, the managing editor developed an
in-house software to view and update the status of each
of the submitted manuscripts. It was developed using the
Active Server Pages (ASP) programming language and a
Microsoft Access database, and is only viewable by the
editors. Although the software served its purpose well,
the journal has grown so much so that its requirements
for additional features far outweigh the resources that
were currently available.
http://www.biij.org/2009/1/e1/
http://onlinelibrary.wiley.com/doi/10.1002/elps.201100033/full
http://link.springer.com/chapter/10.1007/978-3-540-68017-8_61
http://eprints.um.edu.my/5045/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3161234/
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4133609
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6498060&tag=1
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6498060&tag=1
electrochemsci.org/papers/vol7/7065633.pdf
http://www.mdpi.com/1424-8220/13/7/9029
www.sciencedirect.com/science/article/pii/S1751616113003664
electrochemsci.org/papers/vol7/7043765.pdf
www.sciencedirect.com/science/article/pii/S0169260713002964
http://link.springer.com/chapter/10.1007/978-3-540-69139-6_22
www.sciencedirect.com/science/article/pii/S1350417713001831
The results, when compared with results from Al2O3/ZrO2 FGM, showed that SiC increased the compressive stresses in the outer layers, while the inner layers were under a residual tensile stress. (C) 2012 Elsevier Ltd. All rights reserved.
http://www.sciencedirect.com/science/article/pii/S1751616112001038
http://link.springer.com/chapter/10.1007/978-3-642-29305-4_83