Fabrication of A Diode-based Salt Solution Sensor

High blood pressure/hypertension is a severe medical issue among Malaysians that could be reduced by monitoring our salt/sodium intake. One way is to use intraoral salt sensor; this in-mouth method however may cause discomfort and adopts complex and costly fabrication processes. Hence, an external and reusable electronic device, that could be used as a “sweat-sensorâ€, is preferred in detecting the sodium intake of the body. In this study, a potentiometric diode-based salt solution sensor was designed and fabricated in order to detect different salt solution concentrations with applied external voltage. A p-n junction diode sensor was successfully designed and fabricated using four consecutive techniques; thermal wet oxidation, photolithography, thermal diffusion and metallization. The average sheet resistance and resistivity of the diode sensor were measured to be 3.50 x 105 ± 0.66 Ωâ„sq and 3.05 ± 0.5 Ωcm respectively. This sensor showed ideal I-V diode characteristics with a knee voltage of 11.5V in forward bias condition and breakdown voltage of -4 V in reverse bias condition. For salt concentration detection, the sensor was able to detect salt concentration changes with respect to current flow, up to 45 mg/mL

Development of a twin-head infusion pump for micromixing

Mixing is a crucial process in most of the industrial technology such as the operation of chemicals and fermentation reactors, combustion engines, polymer blends, and pharmaceutical formulations [1]. For handling a smaller volume of liquid, micromixing is a suitable method that can be applied. Micromixing (micromixer) is one of the microfluidic functions for mixing and blending liquids as precursors for biological process such as cell activation, enzyme reaction, and drug delivery system [2, 3]. There are several advantages of applying microfluidic device (micromixer) in the chemical technological processes such as processing accuracy, efficiency, minimum usage of reagents and ease of disposing of devices and fluids [3]. Basically, micromixers are categorised into passive and active micromixers. Passive micromixer consists of no moving parts and free from additional friction. It does not use external forces, fully dependent on molecular diffusion and chaotic advection for mixing process [4]. In contrast to active micromixers, external forces are applicable to active micromixers by implementing moving elements either within the microchannels, a time-variant, or a pressure field [5]. To create the pressure field differences for moving the liquid within the micromixer, an infusion pump is usually applied

Formation of Monolayer Polystyrene Array Template for Gold Nanomesh Structure

In this study, the preparation of monolayer array template was performed using 0.2 µm polystyrene (PS) nanospheres monodisperse micro particle deposited onto Indium Tin Oxide (ITO) coated glass substrate. The template was used to arrange the gold (Au) in nanomesh structure thus, enhance its homogeneity for having better sensitivity and repeatability in the plasmonic sensor application. PS nanosphere template was prepared by diluting 0.2 µm PS liquid with ethanol in the ratio of 1:3 and stirred with 400 rpm for 1 hours at 40 °C. Next, the PS solution was spin coated on ITO substrate at different speed variation starting from 200 rpm to 800 rpm in 3 minutes at room temperature. The template structure was then inspected with Field Emission-Scanning Electron Microscopy (FESEM). It was found that, the PS nanosphere template with 600 rpm speed shows the most orderly arrangement of PS array. Subsequently, the PS array template was used as a mask to deposit gold (Au) and performed via direct current (DC) sputtering method. Finally, the Au nanomesh structure was obtained using the lift ‒ off process of PS nanosphere template

Development of Rubber Substrate for More Robust Flexible Wearable Antenna at 2.4 GHz Application

In this work, a flexible microstrip patch antenna has been designed to be working at 2.4 GHz using rubber as the substrate material with permittivity of 3.0 and loss tangent of 0.02. The proposed antenna has been designed to achieve a good result of reflection coefficient, vswr, gain, directivity, and antenna efficiency at the selected operating frequency. The design of rectangular microstrip flexible antenna with two-element horizontal array has depicted a positive performance for wireless frequency band specifically at 2.4 GHz. The selected design has achieved a return loss of -49.659 dB, VSWR of 1.007, gain of 8.16 dBi, directivity of 9.21 dBi and 78.5% of total antenna efficiency. The proposed design is expected to be able to complement with the wearable innovation such as technology used on human body and is applicable for basic communication applications

Micromixers and applications

Mixing and dilutions are processes to combine or putting together one or more reagents such as biomolecules, enzyme, proteins and emulsions into the desired concentrations for further applications in chemical and biological applications. The mixing and diluting of chemical solutions in the laboratory require the use of large quantity of plasticwares, consume time and involve with laborious procedures. Micromixing based on microfluidic is a new innovative means to micromix reagents in microliters volume. The reactions of mixing in both active and passive micromixers are dependent on the mass transport phenomena, viscosity of fluid, molecular diffusion and convection. Reynold number indicates if the fluid flow through a channel is steady or turbulent, while Péclet number indicates the magnitude order between convective and diffusive transport. The success of micromixing is also greatly influenced by the velocity, concentration and pressure of fluids. Different methods for fabricating microfluidic device that include etching, thermoforming, polymer ablation, casting and soft-lithography will be reviewed. In addition, the applications of different designs of micromixers in fluid and particles mixing are illustrated in this chapter