Norazreen Abd Aziz

Characterization of HNA etchant for silicon microneedles array fabrication

Research on microneedles has been increasing rapidly to overcome the drawbacks of hypodermic needle which can results in painful injection, tissue damage and uncontrollable delivery rate. This paper presents process characterization of wet isotropic etching for solid microneedles array development. Work has been carried out to investigate the isotropic etching behavior in 17 different compositions of HNA solution. The experimental responses of vertical etch rate and lateral etch rate are presented. Resulting surface profiles from various HNA compositions are also reported. The etching properties will be applied to develop recipe to fabricate the optimum solid microneedles.

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.

Fabrication Study of Solid Microneedles Array Using HNA

This paper presents an approach for the process development of the out of plane silicon microneedles array fabrication. This study utilizes the wet etching technology using HNA to build a structure of sharp-tipped microneedles; biconvex-conical shaped. The height of the fabricated microneedle is 41.8 mum and the tip radii is 1.4 mum. Investigation on the effect of varying the mask opening window had been carried out. The design approach and the fabrication process are well explained here.

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.

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.

Size-based particles separation utilizing dielectrophoresis technique

This paper describes separation of 3 μm and 10 μm polystyrene particles using dielectrophoresis (DEP) technique. An array of tapered square electrodes with size of 1mm × 1mm and gap size of 80 μm are used in this study. the optimum input frequency in separation for both engineered particles by using droplet technique. Experiment was conducted under negative dielectrophoresis (NDEP), positive dielectrophoresis (PDEP) and crossover frequency of this engineered particles with range 0 to 1.5 MHz. Implementation of dielectrophoresis prove that the capability to manipulate particles based on input frequency tuned at 265 kHz which is FDEP equal to zero. The separation characteristic of polystyrene particles is compare with the separation characteristic of real biological cells i.e red blood cell (RBC) and platelet. Possible application of dielectrophoresis in separation is blood component separation.