Self-Adjusting Electrochemical Etching Technique for Producing Nanoporous Silicon Membrane

This chapter presents the technique in producing the nanoporous silicon membrane using electrochemical etching technique. Electrochemical etching technique is a self-adjusting technique due to its ability to control transfer of ion to form pore by manipulating certain parameters. There are several parameters that have been manipulated to study the effect of each parameter to the pore formation by characterizing each component. The project starts with fabrication of silicon membrane and then continues with characterization of HF concentration, current density, doping and also alcohol diluents using field emission scanning electron microscopy (FESEM). The effect of each parameter is discussed in terms of pore size, pore formation and pore structure. Finally, the pore with size less than 100 nm and columnar structure has formed using this technique. The star-shaped structure is also formed through this experimental setup. Improved nanoporous silicon membrane can be applied for filtration and separating particles, especially in an artificial kidney

Graphene for biomedical applications:a review

Since its discovery in 2004, graphene has enticed engineers and researchers from various fields to explore its possibilities to be incepted into various devices and applications. Graphene is deemed a ‘super’ material by researchers due to its extraordinary strength, extremely high surface-to-mass ratio and superconducting properties. Nonetheless, graphene has yet to find plausible footing as an electronics material. In biomedical field, graphene has proved useful in tissue engineering, drug delivery, cancer teraphy, as a component in power unit for biomedical implants and devices and as a vital component in biosensors. Graphene is used as scaffolding for tissue regeneration in stem cell tissue engineering, as active electrodes in supercapacitor for powering wearable and implantable biomedical devices and as detectors in biosensors. In tissue engineering, the extreme strength of monolayer graphene enables it to hold stem cell tissues as scaffold during in-vitro cell regeneration process. In MEMS supercapacitor, graphene’s extremely high surface-to-mass ratio enables it to be used as electrodes in order to increase the power unit’s energy and power densities. A small yet having high energy and power densities cell is needed to power often space constrainted biomedical devices. In FET biosensors, graphene acts as detector electrodes, owing to its superconductivity property. Graphene detector electrodes is capable of detecting target molecules at a concentration level as low as 1 pM, making it the most sensitive biosensor available today. Graphene continues to envisage unique and exciting applications for biomedical field, prompting continuous research which results and implementation could benefit the general public in decades to come

Spin-on-Glass (SOG) based insulator of stack coupled microcoils for MEMS sensors and actuators application

A comprehensive study on the SOG (Spin-on-Glass) based thin film insulating layer is presented. The SOG layer has been fabricated using simple MEMS technology which can play an important role as insulating layer of stack coupled microcoils. The fabrication process utilizes a simple, cost effective process technique as well as CMOS compatible resulting to a reproducible and good controlled process. It was observed that the spin speed and material preparation prior to the process affect to the thickness and surface quality of the layer. Through the annealing process at temperature 425oC in N2 atmospheric for 1 h, a 750 nm thin SOG layer with the surface roughness or the uniformity of about 1.5% can be achieved. Furthermore, the basic characteristics of the spiral coils, including the coupling characteristics and its parasitic capacitance were discussed in wide range of operating frequency. The results from this investigation showed a good prospect for the development of fully integrated planar magnetic field coupler and generator for sensing and actuating purposes

Pencirian pertumbuhan lapisan nano grafin di atas elektrod antara digit superkapasitor MEMS

Superkapasitor MEMS khususnya dengan reka bentuk elektrod antara digit (IDE), telah menarik minat pada masa kini dalam bidang seperti bioMEMS, bioperubatan implan, peranti kuasa elektronik dan aplikasi berkuasa tinggi disebabkan kapasiti pengecasannya yang tinggi. Kajian ini membentangkan superkapasitor MEMS dengan lapisan nano grafin tumbuh di atas elektrod. Superkapasitor MEMS terdiri daripada silikon dioksida (SiO2), nikel, grafin, polipirol (Ppy) dan lapisan alkohol polivinil (PVA). Tumpuan diberikan kepada fabrikasi struktur lapisan nano grafin atas elektrod superkapasitor MEMS melalui beberapa proses seperti pemendapan wap kimia secara peningkatan plasma (PECVD), penyejatan alur e dan salutan pusing. Grafin tumbuh melalui proses PECVD selama 10 minit pada kuasa 40 Watt dan pada suhu antara 400°C dan 1000°C. Spektrum Raman menunjukkan puncak pada 1340 dan 1580 cm-1 mewakili jalur D dan G . Puncak 2D wujud dalam julat 2600 - 3000 cm-1. Nisbah bagi keamatan puncak 2D terhadap puncak G pada 1000°C adalah 0.43 menunjukkan kualiti yang baik bagi banyak lapisan grafin

Performance of organic dyes for textile cotton fabric

This research was focus on optimum dye concentration for self-cleaning properties for uncoated and coated dyed cotton fabrics through physical and mechanical properties. The dyed cotton fabrics were coated with aqueous emulsion C6-fluorocarbon. C6-fluorocarbon is an organic coating consisting of solid particles where it will dissolve in a specific formulated solvent. Cotton fabrics have cellulose and abundant hydroxyl groups structure where it will make hydrophilic properties where the fiber can provide an appropriate environment for microorganism growth in contact with water and sweats. Therefore, aqueous emulsion C6-fluorocarbon was coated as a hydrophobic coating to overcome the problem of dyed cotton fabric. Moreover, this research was aim to find the optimum concentration of dye with superhydrophobic layer and the comparison of natural dyes with synthetic dye, Golden Yellow with physical and mechanical tests. The test involved were water contact angle, crocking, weather resistance of fabric, washing, abrasion and bursting test. It was found that F (wt/wt%) was the optimum dye concentration and has the highest contact angle. The coated dyed fabric has higher mechanical and physical properties compared to the uncoated dyed fabric which can replace the usage of synthetic dye

A review: properties of silicon carbide materials in MEMS application

The paper presents the review properties of silicon carbide materials in the MEMS application. The study aims to explore silicon carbide in MEMS technology which considers the development of microscale and integrated devices that combine electronics, electrical and mechanical elements. MEMS has become a key area micro-device technology which incorporates materials, mechanical, electrical, chemical and optical disciplines as well as fluid engineering. The prevalence of MEMS technology in harsh environments has grown tremendously in recent years, especially at high temperatures up to 1240 ̊C, wider bandgap (2.3 – 3.4 eV), a higher breakdown field (30 × 105 V/cm), a higher thermal conductivity (3.2 – 4.9 W/cm- K), a higher saturation velocity (2.5 × 107 cm/s), higher oxidation, corrosive environments and higher radiation. Recent developments in robust MEMS for extreme environments such as MEMS pressure sensors have been widely used in ships, warships, gas turbine engines, cars and biomedical equipment. The growing demand for MEMS pressure sensors with high-temperature operating capabilities, mainly for automotive, gas turbine engine and aerospace applications was investigated from this study as alternative silicon carbide to silicon in the fabrication of these devices

Interdigitated MEMS Supercapacitor for Powering Heart Pacemaker

Power MEMS can be defined as microelectromechanical systems for power generation and energy conversion. Energy harvesting has become an increasingly popular option for powering electronic devices as a long-lasting power source. Energy scavenging is defined as the process by which the energy is derived such as vibration, solar, wind, and thermal. Energy harvesting from the environment can prolong the life cycle and reduce the maintenance costs of electronic devices. Among the various sources of energy storage, Among the various of energy storage, supercapacitor has recently gained much interest in fields such as bioMEMS, biomedical implants and power electronic devices due to its advantages such as high power density, rapid charge and discharge and unlimited number of recharge cycles. In biomedical and bioMEMS systems, an energy storage device is needed to power other active biomedical devices within the system. For implantable devices such as a heart pacemaker, the power requirement is in the range of 30–100 μW. Microsupercapacitors play an important role in energy harvesting system, such as collecting energy from ambient energy sources. Human body is very resourceful in generating micropower in the form of heat dissipation, deformation of elastic tissue, and motion. Due to the advantages of MEMS energy harvesting system, the system can be use widely for biomedical implant devices, such as heart pacemakers and hearing aids, and can be used for a long time and without the need for battery replacement. In this work, planar and double-stacked interdigital electrode supercapacitor designs were modeled using Coventorware software. From simulation, it is observed that for planar structure, the specific capacitance is 0.22 mF/cm−2, and for double-stacked structure specific capacitance can be increased to 0.48 mF/cm−2. In terms of specific power, the planar structure produces 0.99 mW/cm−2, and the double-stacked structure produces 2.18 mW/cm−2. These results highlight the superiority of the double-stacked MEMS interdigital supercapacitor design compared with its planar counterpart in terms of charging capacity and electrical performance, thus making it favorable for powering heart pacemaker

Atmospheric pressure chemical vapour deposition growth of graphene for the synthesis of SiO2 based graphene ball

Graphene is a prominent carbon nanomaterial with fascinating characteristics such as high conductivity and very high charge carrier mobility at low temperatures. Numerous synthesis methods for graphene have been established. Chemical vapour deposition (CVD) is among the most successful methods to fabricate high-quality graphene. However, metal-catalyzed growth is used in virtually all of the CVD techniques mentioned. To remove these metal catalysts and relocate the graphene to the necessary dielectric substrate (SiO2/Si or quartz), complex and sophisticated post-growth methods must be used, which limits the usage of graphene in practical electronic components. In the present work, we conducted a preliminary study to determine the suitable methane(CH4) flowrate, which could be used to synthesise SiO2 based graphene ball. Few-layer graphene was grown on a large area of copper(Cu) surface using 20 sccm CH4 in atmospheric pressure CVD (APCVD). The influence of CH4 flowrate on graphene growth has been investigated. Graphene was deposited on a metal catalyst substrate at optimum temperatures of 1000 °C

Statistical optimization of zinc oxide nanorod synthesis for photocatalytic degradation of methylene blue

In this work, synthesis process parameters of Zinc Oxide nanorods (ZnO NRs) photocatalyst is optimized using Taguchi Method to obtain the highest degradation rate of Methylene Blue dye, MB. The Taguchi L27 (38) orthogonal array technique was used to determine the optimum conditions for the synthesis of the nanostructured photocatalyst. Eight important synthesis process parameters were chosen in the analysis while the effects of the parameters were studied using signal-to-noise (S/N) ratio analysis using minitab-16. The ZnO NRs photocatalyst was synthesized via solution process route based on the parameters obtained from the layout of the orthogonal arrays. The optimized synthesized nanorods was then characterized using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), photoluminescence (PL), ultraviolet-visible near-infrared (UV-VIS-NIR), and Raman spectroscopies while the photodegradation of MB was determined by UV-VIS spectrum analysis under ultraviolet light irradiation. The results show that ZnO NRs with hexagonal wurtzite structure and bandgap energy of 3.25 eV have been obtained. The Taguchi analysis based on simulated experimental runs predicted the highest MB degradation percentage of 17.12% that can be achieved under optimum process conditions. Meanwhile, experimental photocatalytic degradation of MB using ZnO NRs synthesized under the same optimum condition achieved a degradation percentage of 17.27%, which deviates only 0.88% from the predicted value. This analysis could give an approach to optimize the synthesis process to ensure the good performance of nano-photocatalyst for the photodegradation of organic contaminations in industrial wastewater in a short time and cost-effective process

Low-temperature nitrogen doping of nanocrystalline graphene films with tunable Pyridinic-N and Pyrrolic-N by cold-wall plasma-assisted chemical vapor deposition

We report a viable method to produce nanocrystalline graphene films on polycrystalline nickel (Ni) with enhanced N doping at low temperatures by a cold-wall plasma-assisted chemical vapor deposition (CVD) method. The growth of nanocrystalline graphene films was carried out in a benzene/ammonia/argon (C6H6/NH3/Ar) system, in which the temperature of the substrate heated by Joule heating can be further lowered to 100 °C to achieve a low sheet resistance of 3.3 k? sq-1 at a high optical transmittance of 97.2%. The morphological, structural, and electrical properties and the chemical compositions of the obtained N-doped nanocrystalline graphene films can be tailored by controlling the growth parameters. An increase in the concentration of atomic N from 1.42 to 11.28 atomic percent (at.%) is expected due to the synergetic effects of a high NH3/Ar ratio and plasma power. The possible growth mechanism of nanocrystalline graphene films is also discussed to understand the basic chemical reactions that occur at such low temperatures with the presence of plasma as well as the formation of pyridinic-N- and pyrrolic-N-dominated nanocrystalline graphene. The realization of nanocrystalline graphene films with enhanced N doping at 100 °C may open great potential in developing future transparent nanodevices