Pei Ling Leow

Fabrication of Nanowire Using Ash Trimming Technique

The paper present a report on fabrication of Nanowire using plasma oxidation, we monitor changes by studying the morphology and Δw / Δh, the study also revealed that the proposed fabrication method could potentially be used to fabricate specific nanometer-scale structure and space structure with uniform surface morphology without any damage to the photoresist. Yet with reduced ashing time and without popping of the photoresist ashing process when the a fabricated is being carried out and subsequently trimmed to nanosize by plasma oxidation, the study also revealed the dramatic increase in aspect ratio as the structure reduces in lateral dimension.

Micropump Pattern Replication Using Printed Circuit Board (PCB) Technology

This article shows a low-cost rapid hot embossing poly (methylmeth acrylate) (PMMA)–based micropump replication with printed circuit board (PCB) mold. PCB material offers advantages of low cost, rigid, and rapid thermal response characteristic. Unlike conventional hot embossing setup, the presented process involved the usage of simple machinery tools: laboratory oven (heat transfer), G-clamp (force deliver), and two aluminium plates (isothermal heat plates). Diffuser and pump chamber were successfully imprinted with the depth of 450 µm and verified pump performance with other reported literatures. To avoid complex bonding process between actuator and membrane, electromagnetic pinch actuation is introduced. The micropump poses flow rate characteristic of 6.66 ml/min and a back pressure of 1.6 kPa under optimum pinch frequency.

Low cost diffuser based micropump using pinch actuation

Planar pinch micropump with the integration of two diffuser valve elements has been reported. The fabrication of the micropump is carried out by utilizing simple hot embossing technique for microdiffuser imprinting and spin coating for membrane construction. Parameter of diffuser design is optimized via finite element analysis (FEA). The experiment result shows that the pump works well at low frequency of 29 Hz.

Application of Infrared sensor for shape detection

This paper describes the use of multiple Infrared sensors to reconstruct a shape by detecting any changes in sensor displacement when there is an obstacle placed in front of the sensor. Meanwhile, the distance between IR sensors and the obstacle was set at 5 cm to minimize the noise contributed by the reflection of the sensor during data collection. A stepper motor was used in the experimental design to control the movement of an obstacle which rotates at 3600 for one complete cycle. Additionally, Arduino Software was used as a micro controller to control the switching mode of the sensor and CoolTerm Software was used to store the sensor output data in the text file format. For analysis, Matlab Software has been used to plot the graph of sensor value against the collected data. IR sensors are capable in measuring data up to 0.05 cm of resolution in displacement. Experimental results showed that by using IR sensors, it is possible to reconstruct a shape via plotting the graph for cylinder, hemisphere and ellipse shape obstacles.

Parametric study of a diffuser in a pressure driven micropump

This paper reports on the parametric study of a diffuser geometrical design for different opening angle, curvature ratio and velocity flow profile using finite element modeling (FEM) approach. The coupling effect of the designed diffuser with the actuator response is experimental studied, where two resonant peaks of the flow rate and back pressure at 2-70 Hz operating frequency are observed. The first peak occurs when the driving frequency is tuned to the natural frequency of actuator, whereas the second peak is due to the net flow characteristic of the diffuser. The experimental study is further extended to analyze the effect of the membrane thickness to the dynamic performance of the micropump. From the experiment, shifting of resonant frequency is noted when thinner membrane is utilized. The study provides a comprehensive guideline for the design parameters of a diffuser element.

Integration of electrochemical detection into micropumps for continuous monitoring system

This paper proposes the integration of electrochemical detection to micropumps for continuous monitoring of ferrocyanide ions. A homemade device is fabricated using 3D printing and casting techniques with a top and bottom layer of 0.5 mm and 3.0 mm, respectively. The volumetric flow and cyclic voltammetry performances of the device are evaluated at the actuator frequency of 10-50 Hz, in 10 Hz increments at concentrations of 2-10 mM, in 2 mM increments. The fabricated device exhibits maximum flow rate of 0.30405 ml/min in the reverse direction with resonance frequency of 20 Hz. The oxidation peak current at 16.02018 μA of 10 mM potassium ferrocyanide in 1 M potassium nitrate is noted. Among the various concentrations of potassium ferrocyanide, 10 mM of potassium ferrocyanide in 1 M potassium nitrate at the maximum flow rate shows the highest oxidation peak current at 16.02018 μA. The presented device offers the advantage of an affordable miniaturized bedside patient continuous monitoring system, due to its low fabrication cost. Additionally, the disposability nature of the device assures collected samples are unpolluted.