Muhamad Ramdzan Buyong

A tapered aluminium microelectrode array for improvement of dielectrophoresis-based particle manipulation.

In this work, the dielectrophoretic force (FDEP) response of Aluminium Microelectrode Arrays with tapered profile is investigated through experimental measurements and numerical simulations. A standard CMOS processing technique with a step for the formation of a tapered profile resist is implemented in the fabrication of Tapered Aluminium Microelectrode Arrays (TAMA). The FDEP is investigated through analysis of the Clausius-Mossotti factor (CMF) and cross-over frequency (fxo). The performance of TAMA with various side wall angles is compared to that of microelectrodes with a straight cut sidewall profile over a wide range of frequencies through FEM numerical simulations. Additionally, electric field measurement (EFM) is performed through scanning probe microscopy (SPM) in order to obtain the region of force focus in both platforms. Results showed that the tapered profile microelectrodes with angles between 60° and 70° produce the highest electric field gradient on the particles. Also, the region of the strongest electric field in TAMA is located at the bottom and top edge of microelectrode while the strongest electric field in microelectrodes with straight cut profile is found at the top corner of the microelectrode. The latter property of microelectrodes improves the probability of capturing/repelling the particles at the microelectrode’s side wall.

Design, fabrication and characterization of dielectrophoretic microelectrode array for particle capture

Purpose – 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. Design/methodology/approach – The presented microelectrode array structures are made of planar conductive metal structure having same size and geometry. Dielectrophoretic force (FDEP) 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 (Vpp) at fixed frequency of 1.5 MHz on capturing effici...

Finite element modeling of dielectrophoretic microelectrodes based on a array and ratchet type

This research describes an investigation of nonuniform electric field for dielectrophoretic forces (FDEP) application in particles and cells manipulation. In an electro kinetics occurrence, a miniaturized array and ratchet type microelectrodes has been simulated. The study of optimal FDEP behavior on the electric field distribution for both type microelectrodes was characterized and optimized by finite element method, (FEM). A set of array and ratchet type microelectrode are biased to generate asymmetric electric field distribution. Normalization of microelectrode simulation result shows that array and ratchet type produced a comparable electric field strength and direction. Deployment of additional dimension for array type electrode, three poles produced the highest of electric field strength of 7.513 e7 V/m and displacement field direction of 2.758 e-3 C/m2. Simulation results are used to design a higher sensitive and selective of a dielectrophoretic (DEP) microelectrode for selection, collection and processing of particle and cell using optimal FDEP that determination advancement in the development of dielectrophoretic a lab-on-a-chip. Ultimately, the findings of this work is possible to contribute in medical sciences research for the enrichment of stem cell from bone narrow and peripheral blood form via integration DEP into a lab on a chip, (DLOC) concept application.

Dielectrophoretic characterization of array type microelectrodes

This research describes an investigation of nonuniform electric field for dielectrophoretic forces, FDEP application in particles manipulation. In an electrokinetics occurrence, a miniaturized array type of two poles microelectrodes has been simulated using engineered particle and tested using graphite metalloid particles. The particles can be attracted towards the regions of strong electric field depending upon the particles is more polarisable than the suspending medium. Dielectrophoresis offers the controllable, selective and accurate manipulation of target graphite metalloid particles. The surface area of graphite attracted to microelectrodes gradually increased starting from 4 seconds for 3412, 3845, and 3764 um2, hence 4589, 4465 and 4739 um2 at the 6 seconds mark and finally 5588, 5569 and 5644 um2 after 8 seconds for three different test run respectively. Further study of optimal FDEP behavior on the electric field distribution for three poles microelectrodes was characterized by finite element method, (FEM). The outcome, FDEP response is further improved by additional poles microelectrodes from top side, instead of side by side in term the strength and direction of electric and displacement field. Ultimately, the findings of this work is possible to contribute in medical sciences research for the enrichment of stem cell from bone narrow and peripheral blood form via integration DEP into a lab on a chip, DLOC concept application.

Fabrication of thin layer membrane using CMOS process for very low pressure sensor applications

A very low pressure sensor has been proposed to be used in the eye for glaucoma treatment with pressure ranging from 10 mmHg to 75 mmHg. This paper presents process development of thin layer membrane for very low pressure sensor application. The structure of the membrane consists of parallel plate which both top and bottom electrodes were fixed at both sides. Utilizing CMOS compatible process, fabrication of the thin layer membrane involved in three stages; i) hole opening etch, ii) sacrificial intermediate oxide release etch and iii) closing of etch holes. Our work focuses on the characterization of holes opening etch size for the intermediate oxide release. Another study was carried out to understand the behavior of sealing off the hole openings etch. This study involved different deposition technique such as LPCVD, PECVD and combination both of them. The findings from these experiments are presented in this paper.

Process characterization of wet etching for high aspect ratio microneedles development

Research on microneedles has been increasing rapidly as to overcome the drawbacks of conventional needle which can results in painful during injection, tissue damage and skin infection at the injected site. This paper presents characterization process of wet isotropic etch for solid microneedles array development. This approach utilizes HNA etchant to build the outer shape of solid microneedles. Works has been carried out to investigate the isotropic etching behavior of HNA in different temperature ranging from 20 to 50 degrees, various agitation rate ranging from 0 rpm to 450 rpm and on the various window size ranging from 100 μm to 500 μm. Characterization on those factor, determine the effect of vertical and lateral etch rate variations, surface quality and the geometry obtained. The experimental responses of vertical etch rate, lateral etch rate and high aspect ratio reported. The obtained etching properties will be applied to develop recipes to fabricate outer shape of solid microneedles’ tip.

Implementing the concept of dielectrophoresis in glomerular filtration of human kidneys

This paper describes a possible application of dielectrophoretic force (FDEP) in glomerular filtration part of mimic human kidney blood filtration process. In an electrokinetics occurrence, a miniaturized array type of two poles microelectrodes has been simulated, fabricated, and tested using engineered particles. The particles can be attracted laterally towards or repelled vertically from the regions of strong intensity electric field, depending upon whether the particles are more or less polarisable than the suspending medium. The FDEP response is further improved by application of tapered DEP electrode profile. The finding of this work is possible to contribute in medical sciences research such as integration of DEP into a lab on a chip (LOC) for application in filters implemented in artificial kidney.

Effect of microchannel geometry in fluid flow for PDMS based device

Microfluidic has become an important component in “lab on chip” device. This portable device has a lot of potential in medical diagnostic to inform the result spontaneously to the patient with only a small volume of sample and reagent. The devices fabrication using Polydimethylsiloxane has become conventional materials which use soft lithography technique developed by Whitesides. However, the inconvenience from this method is the channel fabricated will have a rectangular cross section. From macroscale perspectives, we suggest that circular shape is the best choice to obtain a better performance from the device even though the fabrication of circular microchannel is still a huge obstacle to be figured out. In this paper, we present a fluid flow simulation using finite element COMSOL module microfluidic for circular and rectangular microchannel. Through this simulation, we can see the impact of microchannel shape through the difference in pressure along with velocity and shear rate. From the simulation, the data provided show that a circular channel reduce almost 10 % of the pressure applied to flow the fluid but also 50% of the shear rate. The future work of this study is to fabricate a simple and low cost round microchannel and integrate it in the next lab on chip device.

Dielectrophoretic force response for Lactobacillus Casei

In this research, we discussed laboratory analysis of the dielectrophoretic force response (DFR) using Lactobacillus Casei. Platinum microelectrode array with ~ 80 μm spacing on glass substrate (PMA) are used to study dielectrophoretic behaviour for rod shaped Lactobacillus Casei with size of width 0.7 to 1.1 μm and length of 2 to 4 μm. An experiment was conducted under positive dielectrophoresis (PDEP), negative dielectrophoresis (NDEP) and crossover frequency (fxo) of Lactobacillus Casei over a wide range frequency from 0 Hz to 1 MHz. Implementation DFR proved the capability to streamed the lactobacillus from right to left side and from left to right side based input frequency tuned at fxo ~ 3550 Hz with 10% to 15% input frequency tolerance.

Characterization and optimization of seals-off for Very Low Pressure Sensors (VLPS) fabricated by CMOS MEMS process

In the world of MEMS processing today, fabrications of membrane are performed using bulk micromachining (BMM). However these techniques not easiest to integrate with CMOS standard process due to not compatible of the processing flow. An attractive alternative deployment of surface micromachining (SMM). There is a trend to use surface micromachining to their advantage of simplicity in design and fabrication process compatibility. This paper presents process development of thin layer membrane for very low capacitive pressure sensor application. The structure of the membrane consists of parallel plate which both top and bottom electrodes were fixed at both sides. Utilizing CMOS MEMS process compatible fabrication of the thin layer membrane involved in three stages; i) hole opening etch, ii) sacrificial intermediate oxide release etch and iii) closing of etch holes. Therefore seals-off process characterization and optimization experiment are presented in this paper, will spur advancement in the development of a CMOS MEMS product for very low capacitive pressure sensor.