Recent progress on fabrication of zinc oxide nanorod-based field effect transistor biosensors

Zinc oxide is a unique n-type semiconducting material, owing to wide bandgap of ~3.37 eV, non-toxic, bio-safe and biocompatible with high isoelectric point of ~9.5, make it as promising biomaterial to be utilized as sensing matrix in biosensor applications. In addition, ZnO that possess high electron affinity provide a good conduction pathway for the electrons hence result in significant electrical signal change upon detection to target biomolecules. Moreover, high surface area of ZnO nanorod enhance immobilization of enzymes, hence, increase the device performance. Field effect transistor (FET)-based biosensor offer simplicity in handling and label-free, has also become research topic among researchers for novel biosensor development. This review aims to explore the preparation of ZnO nanorod using hydrothermal method and investigate the fabrication of ZnO nanorod-based FET biosensor. Thus, contribute to enhance understanding towards biosensor development for health monitoring, especially based on FETs structure devices

Multi-Frequency Energy Harvesting Using Thick-Film Piezoelectric Cantilever

Due to the fact that the ambient vibration sources are random and unpredictable, the design of energy harvesters responsing to multi-freuqncy is desirable. In this paper, an array lead zirconate titanate (PZT) thick-film cantilevers were designed and fabricated to demonstrate the possibility of harvesting vibration energy from different frequencies. Two configurations of multi-cantilever were fabricated in a form that elevated from the substrate as free-standing structures. One having six cantilevers of constant width but different lengths and another having five cantilevers of constant length but different widths. The experimental results show a magnitude of voltage at around 70 mV in a range of freqnecy between 220 Hz to 520 Hz which is in a good agreement with simulation results

Characterization of AlInN layer grown on GaN/Sapphire substrate by MOCVD

The AlInN layers have been grown with different growth parameters on GaN/sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The effects of growth parameters such as pressure and temperature on the Al incorporation during AlInN material growth have been investigated. The results showed that lower pressure provides a tendency for higher Al incorporating in the AlInN layer. Besides, as the temperature was increased from 700°C to 780°C, an estimation of 4% reduction on the indium composition has been observed for each 20°C increment. XRD analysis showed that the best crystal quality of AlInN occured at 80% Al composition because of the higher lattice matching with GaN. Based on the above criteria, an Al0.8In0.2N/GaN HEMT device with 2 μm gate length has also been fabricated. The DC characteristics showed a saturated current, Idss of 280 mA/mm and transconductance of 140 mS/mm

Characterization of co-synthesized titanium and ZnO nanostructures

Pure and ZnO-Ti mixed nanowires were synthesized on a p-type silicon wafer. ZnO powder and Ti were mixed and mechanically milled in a ball milling machine. ZnO-Ti mixed nanowires were grown from the milled powder by using thermal evaporation method. Pure and ZnO-Ti mixed nanowires were grown by vapor solid method, using a furnace at 1000degC on a p-type silicon wafer. Characterizations have been done by FE-SEM, EDX and XRD. FE-SEM micrograph shows that the ZnO-Ti mixed nanowires are utilizing ZnO nanowires as bases to start the growth. Ti nanostructure cannot grow directly on the substrate. The segregative growth of Ti and ZnO nanowires describe the difficulty of incorporating Ti into ZnO nanowires

Optical characterization of colloidal zinc selenide quantum dots prepared through hydrothermal method

Zinc selenide (ZnSe) quantum dots (QDs) have been synthesized through a hydrothermal method using ZnCl2 and Na2SeO3 powder as the precursor in the presence of oleylamine as capping agent. The hydrothermal route was conducted at a moderate temperature (150°C) for 8 h. Optical properties of ZnSe QDs were studied through ultraviolet-visible spectroscopy (UV-Vis) and photoluminescence (PL) while the structural properties of ZnSe QDs were characterized using transmission electron microscope (TEM). The photoluminescence (PL) characterization on ZnSe QDs showed that the QDs emit light in blue range region at around 440 nm with optical band gap energy at 3.68 eV. The TEM results showed that the average particle size is around 8.9 nm. It is a good candidates for optoelectronic devices such as light emitting diodes (LED)

Multi-frequency energy harvesting using thick-film piezoelectric cantilever

Due to the fact that the ambient vibration sources are random and unpredictable, the design of energy harvesters responding to multi-frequency is desirable. In this paper, an array lead zirconate titanate (PZT) thick-film cantilevers were designed and fabricated to demonstrate the possibility of harvesting vibration energy from different frequencies. Two configurations of multi-cantilever were fabricated in a form that elevated from the substrate as free-standing structures. One having six cantilevers of constant width but different lengths and another having five cantilevers of constant length but different widths. The experimental results show a magnitude of voltage at around 70 mV in a range of frequency between 220 Hz to 520 Hz which is in a good agreement with simulation results

Stress and deformation of optimally shaped silicon microneedles for transdermal drug delivery

In this study, we demonstrated the fabrication of the concave conic shape microneedle with the aid of COMSOL Multiphysics simulation. The stress and buckling of the microneedle structure were simulated by applying various loads ranging from 50 to 800 g perpendiculars to the tip in order to predict the occurrence of microneedles structure deformation. The simulation study indicated that the surface buckling deformation does not occur to the microneedle structure with the increment of the load. The microneedles with dimensions of height and diameter tip ranging from 60 to 100 μm and 1 to 4 μm, respectively had been fabricated via an etching process in a mixture of hydrofluoric acid, nitric acid, and acetic acid. Three optimized microneedles but different in the structures were fabricated via the acidic etching process. The reproducibility of three different microneedle structures was 15, 20, and 60%, respectively. Stress and buckling analyses of the fabricated microneedles were further carried out on the rat skin. The obtained experimental results show promising applications for the deep dermis, stratum corneum to epidermis layer penetration

Kaedah diagnostik semasa dan penggunaan ujian Titik Penjagaan Pantas (POC) bagi mendiagnos Hiperkolesterolemia Famili (FH)

Hiperkolesterolemia Famili (FH) ialah penyakit genetik yang diwarisi secara autosomal dominan dan dicirikan melalui peningkatan kepekatan plasma kolesterol lipoprotein berketumpatan rendah (LDL-C) di dalam darah. Pesakit FH yang tidak didiagnosis di peringkat awal dan tidak dirawat boleh meningkatkan risiko penyakit jantung koronari pramatang. Dengan kepesatan teknologi dalam bidang biologi molekul, terdapat pelbagai strategi telah diambil untuk membolehkan diagnosis awal FH dilakukan. Teknik-teknik ini dapat meningkatkan keberkesanan kos dan tempoh masa pengesanan adalah lebih cepat. Kaedah diagnostik semasa yang sedia ada untuk mendiagnosis FH yang melibatkan kriteria skor berasaskan algoritma dan pelbagai kaedah diagnosis molekul seperti kaedah penjujukan generasi kedua (NGS), penjujukan Sanger, multiplex ligation-dependent probe amplification (MLPA) dan mikroatur melalui hibridisasi DNA akan dibincangkan di dalam ulasan ini. Walau bagaimanapun, ujian genetik molekul ini tidak tersedia secara meluas atas sebab seperti prosedur yang memakan masa, kos yang tinggi dan keperluan kepada kakitangan terlatih. Oleh itu, ulasan ini memberi penekanan kepada penggunaan ujian titik penjagaan pantas (point of care, POC) sebagai pendekatan untuk mendiagnosis FH kerana ketiadaan ujian genetik bagi pemeriksaan rutin di negara yang kekurangan infrastruktur dan kepakaran. Ujian aliran lateral (LFA) telah mendapat perhatian sebagai kaedah diagnostik POC kerana ianya mudah, memerlukan kos yang rendah dan proses yang lebih cepat. Kelebihan ini menjadikan LFA sebagai teknik yang berpotensi dalam menangani beberapa cabaran bagi diagnosis FH khususnya bagi diagnosis awal terhadap keluarga pesakit

Different atmospheric moisture divergence responses to extreme and moderate El Niños

On seasonal and inter-annual time scales, vertically integrated moisture divergence provides a useful measure of the tropical atmospheric hydrological cycle. It reflects the combined dynamical and thermodynamical effects, and is not subject to the limitations that afflict observations of evaporation minus precipitation. An empirical orthogonal function (EOF) analysis of the tropical Pacific moisture divergence fields calculated from the ERA-Interim reanalysis reveals the dominant effects of the El Niño-Southern Oscillation (ENSO) on inter-annual time scales. Two EOFs are necessary to capture the ENSO signature, and regression relationships between their Principal Components and indices of equatorial Pacific sea surface temperature (SST) demonstrate that the transition from strong La Niña through to extreme El Niño events is not a linear one. The largest deviation from linearity is for the strongest El Niños, and we interpret that this arises at least partly because the EOF analysis cannot easily separate different patterns of responses that are not orthogonal to each other. To overcome the orthogonality constraints, a self-organizing map (SOM) analysis of the same moisture divergence fields was performed. The SOM analysis captures the range of responses to ENSO, including the distinction between the moderate and strong El Niños identified by the EOF analysis. The work demonstrates the potential for the application of SOM to large scale climatic analysis, by virtue of its easier interpretation, relaxation of orthogonality constraints and its versatility for serving as an alternative classification method. Both the EOF and SOM analyses suggest a classification of “moderate” and “extreme” El Niños by their differences in the magnitudes of the hydrological cycle responses, spatial patterns and evolutionary paths. Classification from the moisture divergence point of view shows consistency with results based on other physical variables such as SST