Pei Song Chee

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.

Soft dielectric elastomer actuator for micropump application

This paper reports a miniaturized soft dielectric elastomer actuator targeted at an active flow controlled application. The muscle-alike soft actuator buckles when subjected to a pre-stretch tensile force by a pull up spring that is made from 2 mm thick elastic plastic. The actuator forms an out-of-plane deflection in a conical frustum shape profile and couples with a pair of diffuser elements to rectify the fluid flow in a contraction and expansion mode. To achieve desired deflection, finite element analysis is deployed to study the geometrical design of the elastomer parameters. A maximum deflection of 0.42 mm is noted at 4.2 kV, where beyond this voltage, wrinkle is formed on the compliant electrode. The deflection dynamic response of each repetitive actuation cycle achieves high reliability at low operating frequency of 0.1 Hz and 0.25 Hz with the standard deviation of 1.4% and 1.25%, respectively. The frequency dependent characteristic of the device is determined by measuring the effective deflection at each frequency cycle. Experimental characterization of the fabricated micropump shows a successful maximum flow rate of 42 μL/s at an optimum frequency of 3 Hz.

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.

Polyvinylpyrrolidone/Multiwall Carbon Nanotube Composite Based 36° YX LiTaO3 Surface Acoustic Wave For Hydrogen Gas Sensing Applications

Poly‐vinyl‐pyrrolidone (PVP) /Multiwall Carbon Nanotubes (MWNTs) based Surface Acoustic Wave (SAW) sensors are fabricated and characterized, and their performances towards hydrogen gas are investigated. The PVP/MWNTs fibers composite are prepared by electrospinning of the composite aqueous solution deposited directly onto the active area of SAW transducers. Via scanning electron microscopy (SEM), the morphology of the deposited nanostructure material is observed. From the dynamic response, frequency shifts of 530 Hz (1% H2) and 11.322 kHz (0.25% H2) are recorded for the sensors contain of 1.525 g and 1.025 g PVP concentrations, respectively.

Ez430-chronos watch as a wireless health monitoring device

The paper describes a wireless health monitoring system, developed in LabVIEW, which is able to transmit and receive a patient’s body signal wirelessly to an eZ430- Chronossport watch.Patient’s vital body signal such as heart rate and percentage of oxygen saturation will be wirelessly transmitted to a programmable eZ430-Chronos watch to ease patient monitoring. The watch, used as a monitoring device will be worn by the doctor or any other individuals who is responsible in monitoring a patient’s condition (i.e.nurse or any of the patient’s family members). The system enables the user to be alerted immediately should any abnormalities occur to a monitored patient and he/she can be attended instantly. This would improve patient monitoring system remotely within the wireless protocol given.

Polyvinylpyrrolidone/multiwall carbon nanotube composite based 36° YX LiTaO 3 surface acoustic wave H 2 gas sensor

Poly-vinyl-pyrrolidone (PVP) is one of the actylene chemistry products founded by Prof Walter Reppe [1]. In most cases, PVP usually presents as an essential auxiliary, not an active substance itself [2]. Until recently, He et al. [3] has reported the application of PVP fibers as H2 gas sensor. Extending from the reported investigation, this work shows the gas sensing properties of PVP/MWNTs composite/36° YX LiTaO3 SAW device.

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.

A comparison of Principal Component Regression and Artificial Neural Network in VIS-SWNIR spectroscopy

Generally, non-linear predictive models should be superior to linear predictive models. The objective of this study is to compare the performance of soluble solid content (SSC) prediction via Artificial Neural Network with Principal Components (PCs-ANN) and Principal Component Regression (PCR) in Visible and Shortwave Near Infrared (VIS-SWNIR) (400 - 1000 nm) spectrum. The spectra of 116 Fuji Apple samples were separated into calibration set of 84 apple samples and testing set of 32 apple samples randomly. Firstly, multiplicative scattering correction (MSC) was used to pre-process the spectra. Secondly, Principal Component Regression (PCR) was used to obtain the optimal number of principal components (PCs). Thirdly, the optimal PCs were used as the inputs of both multiple linear regression (MLR) and Artificial Neural Network (ANN) models. The results from this study showed that the predictive performance was improved significantly when PCs-ANN with two neurons was used compared to the PCR.