Search results

This paper aims to present the capacitance characterization of tapered dielectrophoresis (DEP) microelectrodes as micro-electro-mechanical system sensor and actuator device. The application of DEP-on-a-chip (DOC) can be used to evaluate and correlate the capacitive sensing measurement at an actual position and end station of liquid suspended targeted particles by DEP force actuator manipulation.

The capability of both, sensing and manipulation was analysed based on capacitance changes corresponding to the particle positioning and stationing of the targeted particles at regions of interest. The mechanisms of DEP sensor and actuator, designed in DOC applications were energized by electric field of tapered DEP microelectrodes. The actual DEP forces behaviour has been also studied via quantitative analysis of capacitance measurement value and its correlation with qualitative analysis of positioning and stationing of targeted particles.

The significance of the present work is the ability of using tapered DEP microelectrodes in a closed mode system to simultaneously sense and vary the magnitude of manipulation.

The integration of DOC platform for contactless electrical-driven with selective detection and rapid manipulation can provide better efficiency in in situ selective biosensors or bio-detection and rapid bio-manipulation for DOC diagnostic and prognostic devices.

The purpose of this paper is to visualize protein manipulation using dielectrophoresis (DEP) as a substantial perspective on being an effective protein analysis and biosensor method as DEP is able to be used as a means for manipulation, fractionation, pre-concentration and separation. This research aims to quantify DEP using an electrochemical technique known as cyclic voltammetry (CV), as albumin is non-visible without any fluorescent probe or dye.

The principles of DEP were generated by an electric field on tapered DEP microelectrodes. The principle of CV was analysed using different concentrations of albumin on a screen-printed carbon electrode. Using preliminary data from both DEP and CV methods as a future prospect for the integration of both techniques to do electrical quantification of DEP forces.

The size of the albumin is known to be 0.027 µm. Engineered polystyrene particle of size 0.05 µm was selected to mimic the DEP actuation of albumin. Positive DEP of the sample engineered polystyrene particle was able to be visualized clearly at 10 MHz supplied with 20 Vpp. However, negative DEP was not able to be visualized because of the limitation of the apparatus. However, albumin was not able to be visualized under the fluorescent microscope because of its translucent properties. Thus, a method of electrical quantification known as the CV technique is used. The detection of bovine serum albumin (BSA) using the CV method is successful. As the concentration of BSA increases, the peak current obtained from the voltammogram decreases. The peak current can be an indicator of DEP response as it correlates to the adsorption of the protein onto the electrodes. The importance of the results from both CV and DEP shows that the integration of both techniques is possible.

The integration of both methods could give rise to a new technique with precision to be implemented into the dialyzers used in renal haemodialysis treatment for manipulation and sensing of protein albumin.

The purpose of this paper is to propose an alternative approach to improve the performance of microelectromechanical systems (MEMSs) silicon (Si) condenser microphones in terms of operating frequency and sensitivity through the introduction of a secondary material with a contrast of mechanical properties in the corrugated membrane.

Finite element method from COMSOL is used to analyze the MEMS microphones performance consisting of solid mechanic, electrostatic and thermoviscous acoustic interfaces. Hence, the simulated results could described the physical mechanism of the MEMS microphones, especially in the case of microphones with complex geometry. A 2-D model was used to simplify computation by applying axis symmetry condition.

The simulation results have suggested that the operating frequency range of the microphone could be extended to be operated beyond 20 kHz in the audible frequency range. The data showed that the frequency resonance of the microphone using a corrugated Si membrane with SiC as the embedded membrane is increased up to 70 kHz compared with 63 kHz for the plane Si membrane, whereas the microphone’s sensitivity is slightly decreased to −79 from −76 dB. Furthermore, the frequency resonance of a corrugated membrane microphone could be improved from 26 to 70 kHz by embedding the SiC material. Last, the sensitivity and frequency resonance value of the microphones could be modified by adjusting the height of the embedded material.

Based on these theoretical results, the proposed modification highlighted the advantages of simultaneous modifications of frequency and sensitivity that could extend the applications of sound and acoustic detections in the ultrasonic spectrum with an acceptable performance compared with the typical state-of-the-art Si condenser microphones.

The purpose of this paper is to use a particle velocity measurement technique on a tapered microelectrode device via changes of an applied voltage, which is an enhancement of the electric field density in influencing the dipole moment particles. Polystyrene microbeads (PM) have used to determine the responses of the dielectrophoresis (DEP) voltage based on the particle velocity technique.

Analytical modelling was used to simulate the particles’ polarization and their velocity based on the Clausius–Mossotti Factor (CMF) equation. The electric field intensity and DEP forces were simulated through the COMSOL numerical study of the variation of applied voltages such as 5 V p-p, 7 V p-p and 10 V p-p. Experimentally, the particle velocity on a tapered DEP response was quantified via the particle travelling distance over a time interval through a high-speed camera adapted to a high-precision non-contact depth measuring microscope.

The result of the particle velocity was found to increase, and the applied voltage has enhanced the particle trajectory on the tapered microelectrode, which confirmed its dependency on the electric field intensity at the top and bottom edges of the electrode. A higher magnitude of particle levitation was recorded with the highest particle velocity of 11.19 ± 4.43 µm/s at 1 MHz on 10 V p-p, compared to the lowest particle velocity with 0.62 ± 0.11 µm/s at 10 kHz on 7 V p-p.

This research can be applied for high throughout sensitivity and selectivity of particle manipulation in isolating and concentrating biological fluid for biomedical implications.

The comprehensive manipulation method based on the changes of the electrical potential of the tapered electrode was able to quantify the magnitude of the particle trajectory in accordance with the strong electric field density.

This paper aims to present the dielectrophoresis (DEP) force (FDEP), defined as microelectrofluidics mechanism capabilities in performing selective detection and rapid manipulation of blood components such as red blood cells (RBC) and platelets. The purpose of this investigation is to understand FDEP correlation to the variation of dynamic dielectric properties of cells under an applied voltage bias.

In this paper, tapered design DEP microelectrodes are used and explained. To perform the characterization and optimization by analysing the DEP polarization factor, the change in dynamic dielectric properties of blood components are observed according to the crossover frequency (f_xo) and adjustment frequency (f_adj) variation for selective detection and rapid manipulation.

Experimental observation of dynamic dielectric properties change shows clear correlation to DEP polarization factor when performing selective detection and rapid manipulation. These tapered DEP microelectrodes demonstrate an in situ DEP patterning efficiency more than 95%.

The capabilities of tapered DEP microelectrode devices are introduced in this paper. However, they are not yet mature in medical research studies for various purposes such as identifying cells and bio-molecules for detection, isolation and manipulation application. This is because of biological property variations that require further DEP characterization and optimization.

The introduction of microelectrofluidics using DEP microelectrodes operate by selective detecting and rapid manipulating via lateral and vertical forces. This can be implemented on precision health-care development for lab-on-a-chip application in microfluidic diagnostic and prognostic devices.

This study introduces a new concept to understand the dynamic dielectric properties change. This is useful for rapid, label free and precise methods to conduct selective detection and rapid manipulation of mixtures of RBC and platelets. Further, potential applications that can be considered are for protein, toxin, cancer cell and bacteria detections and manipulation. Implementation of tapered DEP microelectrodes can be used based on the understanding of dynamic dielectric properties of polarization factor analysis.

The purpose of this study is to design and characterize the dielectrophoretic (DEP) microelectrodes with various array structure arrangements in order to produce optimum non-uniform electric field for particle capture. The DEP-electrodes with 2D electrode structure was fabricated and characterized to see the effect of electrode structure configuration on the capture capability of the cells suspending in the solution.

The presented microelectrode array structures are made of planar conductive metal structure having same size and geometry. Dielectrophoretic force (F_DEP) generated in the fluidic medium is initially simulated using COMSOL Multi-physics performed on two microelectrodes poles, which is then continued on three-pole microelectrodes. The proposed design is fabricated using standard MEMS fabrication process. Furthermore, the effect of different sinusoidal signals of 5, 10 and 15 volt peak to peak voltage (V_pp) at fixed frequency of 1.5 MHz on capturing efficiency of microelectrodes were also investigated using graphite metalloids particles as the suspended particles in the medium. The graphite particles that are captured at the microelectrode edges are characterized over a given time period.

Based on analysis, the capturing efficiency of microelectrodes at the microelectrode edges is increased as voltage input increases, confirming its dependency to the F_DEP strength and direction of non-uniform electric field. This dependency to field consequently increases the surface area of the accumulated graphite. It is also showed that the minimum ratio of the surface accumulated area of captured graphite is 1, 2.75 and 9 μm2 for 5, 10 and 15 V_pp, respectively. The simulation result also indicates a significant improvement on the performance of microelectrodes by implementing third pole in the design. The third pole effect the particles in the medium by creating stronger non-uniform electric field as well as more selective force toward the microelectrodes’ edges.

The microelectrode array arrangement is found as a reliable method to increase the strength and selectivity of non-uniform electric field distribution that affect F_DEP. The presented findings are verified through experimental test and simulation results.

This paper aims to Separation and sorting of biological cells is desirable in many applications for analyzing cell properties, such as disease diagnostics, drugs delivery, chemical processing and therapeutics.

Acoustic energy-based bioparticle separation is a simple, viable, bio-compatible and contact-less technique using, which can separate the bioparticles based on their density and size, with-out labeling the sample particles.

Conventionally available bioparticle separation techniques as fluorescence and immunomagnetic may cause a serious threat to the life of the cells due to various compatibility issues. Moreover, they also require an extra pre-processing labeling step. Contrarily, label-free separation can be considered as an alternative solution to the traditional bio-particle separation methods, due to their simpler operating principles and lower cost constraints. Acoustic based particle separation methods have captured a lot of attention among the other reported label-free particle separation techniques because of the numerous advantages it offers.

This study tries to briefly cover the developments of different acoustic-based particle separation techniques over the years. Unlike the conventional surveys on general bioparticles separation, this study is focused particularly on the acoustic-based particle separation. The study would provide a comprehensive guide for the future researchers especially working in the field of the acoustics, in studying and designing the acoustic-based particle separation techniques.

The study insights a brief theory of different types of acoustic waves and their interaction with the bioparticles is considered, followed by acoustic-based particle separation devices reported till the date. The integration of acoustic-based separation techniques with other methods and with each other is also discussed. Finally, all major aspects like the approach, and productivity, etc., of the adopted acoustic particle separation methods are sketched in this article.

The hygroscopic properties of 3D-printed filaments and moisture absorption itself during the process result in dimensional inaccuracy, particularly for nozzle movement along the x-axis and for micro-scale features. In view of that, this study aims to analyze in depth the dimensional errors and deviations of the fused filament fabrication (FFF)/fused deposition modeling (FDM) 3D-printed micropillars (MPs) from the reference values. A detailed analysis into the variability in printed dimensions below 1 mm in width without any deformations in the printed shape of the designed features, for challenging filaments like polymethyl methacrylate (PMMA) has been done. The study also explores whether the printed shape retains the designed structure.

A reference model for MPs of width 800 µm and height 2,000 µm is selected to generate a g-code model after pre-processing of slicing and meshing parameters for 3D printing of micro-scale structure with defined boundaries. Three SETs, SET-A, SET-B and SET-C, for nozzle diameter of 0.2 mm, 0.25 mm and 0.3 mm, respectively, have been prepared. The SETs containing the MPs were fabricated with the spacing (S) of 2,000 µm, 3,200 µm and 4,000 µm along the print head x-axis. The MPs were measured by taking three consecutive measurements (top, bottom and middle) for the width and one for the height.

The prominent highlight of this study is the successful FFF/FDM 3D printing of thin features (<1mm) without any deformation. The mathematical analysis of the variance of the optical microscopy measurements concluded that printed dimensions for micropillar widths did not vary significantly, retaining more than 65% of the recording within the first standard deviation (SD) (±1 s). The minimum value of SD is obtained from the samples of SET-B, that is, 31.96 µm and 35.865 µm, for height and width, respectively. The %RE for SET-B samples is 5.09% for S = 2,000µm, 3.86% for S = 3,200µm and 1.09% for S = 4,000µm. The error percentage is so small that it could be easily compensated by redesigning.

The study does not cover other 3D printing techniques of additive manufacturing like stereolithography, digital light processing and material jetting.

The presented study can be potentially implemented for the rapid prototyping of microfluidics mixer, bioseparator and lab-on-chip devices, both for membrane-free bioseparation based on microfiltration, plasma extraction from whole blood, size-selection trapping of unwanted blood cells, and also for membrane-based plasma extraction that requires supporting microstructures. Our developed process may prove to be far more economical than the other existing techniques for such applications.

For the first time, this work presents a comprehensive analysis of the fabrication of micropillars using FDM/FFF 3D printing and PMMA in filament form. The primary focus of the study is to minimize the dimensional inaccuracies in the 3D printed devices containing thin features, especially in the area of biomedical engineering, by delivering benefits from the choice of the parameters. Thus, on the basis of errors and deviations, a thorough comparison of the three SETs of the fabricated micropillars has been done.

This study examined Muslim civil officers’ cash waqf giving decisions in Malaysia.

Using the theory of planned behaviour (TPB), the effects of the said factors on the decisions were examined using logistic analysis. A total of 583 Muslim civil officers were involved in this work. The discrete dependent variable measures whether a civil officer is a donor or non-donor cash waqf.

Results obtained indicate significant influences of attitude, subjective norm, perceived behavioural control and some demographic items on cash waqf giving decisions in Malaysia.

The findings attained were narrowed in terms of chosen geographical settings and the theory used.

This study provides a theoretical benchmark to enhance cash waqf giving decisions, which in turn can affect the waqf collection by the waqf institutions in Malaysia.

This study uniquely develops Muslim civil officers’ cash waqf giving decisions framework (CAGDEF) in measuring cash waqf giving decisions in Malaysia.

The peer review history for this article is available at: https://publons.com/publon/10.1108/IJSE-12-2023-0964.

This study aims to ascertain consumption values of Muslim tourists, attitudes, satisfaction and loyalty towards a Muslim-friendly accommodation, which has gained recognition from the Malaysian Government. Subsequently, an overall Muslim-friendly image was examined as a moderating variable within the associated relationship.

A quantitative research design with a purposive sampling technique was chosen through a sample size of 378 people in Malaysia and distributed via social media. The respondents were selected based on the Muslim-friendly accommodation recognition (MFAR) initiatives, a procedure of accreditation which acknowledges Muslim-friendly accommodation for tourists. To obtain data from those travellers, structured questionnaires were used. SmartPLS was used for data analysis in this study.

The values which were found to have an influence on attitude towards a Muslim-friendly accommodation are related to social, emotional, economic, functional, monetary and epistemic elements. On the other hand, hedonic, conditional, Islamic and altruistic values were found to be insignificant in determining the attitude towards a Muslim-friendly accommodation. Subsequently, an overall Muslim-friendly image was found to moderate the relationship between social, monetary and altruistic values and its link concerning attitude towards the accommodation, while the rest of the relationships were not significant. More importantly, attitude seems to have an impact on satisfaction, as well as its loyalty towards a Muslim-friendly accommodation.

Firstly, it begins with understanding Malaysia, one of the developing countries in Southeast Asia. Secondly, data was collected from participants using a survey method, from purposive sampling which may limit the findings’ generalizability. Thirdly, this study focussed exclusively on the perceived value dimensions associated with Muslim-friendly accommodation, thus, disregarding consumers who may associate with other types of tourism and hospitality elements.

The results provide a fresh insight and a better understanding regarding the consumption values and all of its related components towards customer loyalty of the Muslim-friendly accommodation in Malaysia. In addition, the findings deliver new information and a deeper understanding of relevant values in Malaysia’s Muslim-friendly accommodation, which can be used as a standard guideline by industry practitioners, local and abroad.

This research supports service providers in developing effective brand management strategies for their own businesses. Apparently, this study discovers that emotional values tend to be the most important values in determining attitude towards Muslim-friendly accommodation.

To the best of the authors’ knowledge, this is one of the studies examining the overall perceived Muslim-friendly image within the consumption values that are relevant from an Islamic viewpoint. It provides policymakers, as well as the industry players, some reliable approaches for enhancing Muslim-friendly accommodation.