Papers by Author: Jumril Yunas

Abstract: Microfluidics platform offers a great advantage in bio-sensing and clinical diagnostics miniaturization. The requirement of inexpensive and rapid-prototyping materials are essential in microfluidics device commercialization. This paper presents rapid prototyping of UV-curing Polyurethane Methacrylate (PUMA) microchannel from the Polydimethlsiloxane (PDMS) mold. Two techniques in PUMA microchannel UV-curing rapid prototyping have successfully demonstrated in this work. The first technique utilized thin film transparency sheet as PUMA resin top surface cover in facilitating PUMA UV-curing. The second method exploited confined nitrogen gas environment in Pyrex dish chamber in expediting PUMA curing under UV light exposure. In this work, two different approaches of fluidic interconnect tubings for PUMA microchannel inlet and outlet are also presented. Reversible bonding techniques using corona discharge treatment are utilized for bonding of PUMA microchannel and fluidic interconnect with PUMA, silicon, glass and PDMS substrate. Accomplishment of preliminary fluid flow testing using PUMA microchannel proved its capability for microfluidics applications.

Abstract: Microchannel of micron-to milimeter in dimension has been immensely used for fluid handling in transporting, mixing and separating biological cells in Lab-on-Chip (LoC) applications. In this paper, design, simulation and fabrication of Polydimethylsiloxane (PDMS) microfluidic channel are presented. The microchannel is designed with one inlet and outlet. A reservoir or chamber is proposed as an extra component in the microchannel design for ease of separating the intended biological cells as used in LoC magnetic separator and micro-incubator. Finite Element Analysis (FEA) shows laminar flow characteristic is maintained in the proposed microchannel design operating at volumetric flow rate between 0.5 to 1000 μL/min. In addition, pressure drop data across the microchannel are also been obtained from the FEA in determining the safe operation limit of the microchannel. The PDMS microchannels of two different chamber geometries have been successfully fabricated using replica molding technique from SU-8 negative photoresist mold. The fabricated SU-8 mold and the PDMS microchannel structure dimension are characterized using Scanning Electron Microscopy (SEM). Reversible bonding of PDMS microchannel layer and PDMS tubing layer has successfully accomplished by activating the PDMS surfaces using corona discharge. The preliminary testing of the microchannel confirmed its function for LoC continuous flow applications.

Abstract: A Planar square stack coupled inductor coils on silicon substrate has been fabricated using MEMS technology. The fabrication process utilized a simple, cost effective process technique as well as CMOS compatible resulting to a reproducible and good controlled process. The basic characteristics of the coupled inductors were discussed in wide range of operating frequency. The analysis results showed that the geometry of the inductor coil strongly affects the basic characteristics of the coils. The results of the study have promised a good prospect for the development of fully integrated planar magnetic field generator for sensing and actuating purposes.

Abstract: A new planar micro-transformer having sandwich spiral coil structure is fabricated using MEMS micro-fabrication technique. Stack interwinding coil is designed to achieve high coupling and higher winding number at relatively small coil area. In this work, stack sandwich interwinding coil structure is fabricated by bonding the substrates of the coil at connection pads using conductive epoxy material. This method replaces the use of conventional via connections that cause the most problem of current conductance in planar structures. The inductance of fabricated coil are measured at wide range of operating frequency using cascade GSG probe. The results show that the proposed technique is an alternative way in fabricating a simple and cost effective 3-dimensional structure of stack micro-transformer.

Abstract: This paper presents a simple process technique for the fabrication of valveless micro-pumps. The process design utilizes standard MEMS process using double-sided anisotropic silicon wet etching process with an additional adhesive bonding technique. The diffuser and nozzle element of the pump with depth of 50 µm, as well as a 150 µm thick silicon membrane are designed and fabricated using only 3 patterning process steps. A piezoelectric plate working at the frequency range from 0.1 kHz to 2 kHz is bonded on to the back side of the silicon membrane to create the membrane actuation. The patterning process of thick photoresist used as the adhesive layer for the substrate bonding is also discussed in detail. The fluid flow is observed and the process reproducibility is proven which show a good prospect for the future development of miniaturized valveless pump for biomedical application.

Abstract: In this paper, a theoretical analysis of thin film oxide resulted from lumped element model analysis using ASITIC simulation tool is presented. The study is aimed to investigate the effect of the oxide thickness on the electrical characteristics of planar micro-coils. Some important device parameters, such as parasitic capacitances and resistances caused by oxide and substrate layer, and quality factor of the planar coil, as well as the characteristic of the magnetic field coupled between the coils are analyzed in wide range of operating frequency. The simulation results show that there is significant influence of the oxide thickness to the device characteristics. It is shown that by increasing the thickness of the oxide layer on the substrate, a high Q-factor of 5 can be obtained, while the magnetic coupling is improved when the thickness of the oxide layer residing between metal layers is reduced.