Fabrication of electrostatic MEMS microactuator based on X-ray lithography with Pb-based X-ray mask and dry-film-transfer-to-PCB process

Lithographie Galvanoformung Abformung (LIGA) is a promising approach for fabrication of high aspect ratio 3D microactuator for dual-stage slider in hard disk drive. However, this approach involves practically challenging X-ray lithography and structural transfer processes. In this work, electrostatic MEMS actuator is developed based on a LIGA approach with cost-effective X-ray lithography and dry-film-transfer-to-PCB process. X-ray lithography is performed with X-ray mask based on lift-off sputtered Pb film on mylar substrate and photoresist application using casting-polishing method. High quality and high aspect ratio SU8 microstructures with inverted microactuator pattern have been achieved with the interdigit spacing of ~5 μm, vertical sidewall and a high aspect ratio of 29 by X-ray lithography using the low-cost Pb based X-ray mask. A new dry-film-transfer-to-PCB is employed by using low-cost dry film photoresist to transfer electroplated nickel from surface-treated chromium-coated glass substrate to printed circuit board (PCB) substrate. The dry film is subsequently released everywhere except anchor contacts of the electrostatic actuator structure. The fabricated actuator exhibits good actuation performance with high displacement at moderate operating voltage and suitably high resonance frequency. Therefore, the proposed fabrication process is a promising alternative to realize low-cost MEMS microactuator for industrial applications.     

Electron beam evaporated carbon nanotube dispersed SnO2 thin film gas sensor

Carbon nanotube (CNT) is a useful material for gas-sensing applications because of its high surface to volume ratio structure. In this work, multi-wall CNTs are incorporated into tin oxide thin film by means of powder mixing and electron beam evaporation and the enhancement of gas-sensing properties is presented. The CNTs were combined with SnO₂powder with varying concentration in the range of 0.25–5% by weight and electron beam evaporated onto glass substrates. From AFM and TEM characterization, CNT inclusion in SnO₂thin film results in the production of circular cone protrusions of CNT clusters or single tube coated with SnO₂layer. Experimental results indicate that the sensitivity to ethanol of SnO₂thin film increases by the factors of 3 to 7, and the response time and recovery time were reduced by the factors of 2 or more with CNT inclusion. However, if the CNT concentration is too high, the sensitivity is decreased. Moreover, the CNT doped film can operate with good sensitivity and stability at a relatively low temperature of 250–300^∘C. The improved gas-sensing properties should be attributed to the increasing of surface adsorption area of metal oxide produced by CNT protrusion.     

A Business Model Guideline of Electricity Utility Systems Based on Blockchain Technology in Thailand: A Case Study of Consumers,Prosumers and SMEs

This paper presents a business model guideline of electricity utility systems based on blockchain technology in Thailand: a case study of consumers, prosumers and SMEs. Because the resource management of electricity utility systems in Thailand presently are based on enhanced single buyer or a centralized system. However, a free-trade energy market is likely to open or occur in the near future. Thus, a preparation of changing or adapting such a free-trade energy market using disruptive technology is an important point to study the aforementioned disruptive technology (i.e. blockchain technology). The future business of the free-trade energy market is related to the policy of the government (Thailand 4.0). It will support technology development and innovation to encourage the potential and readiness and to compete for foreign countries. In this scoping study, the business model guideline of electricity trading with peer to peer (P2P) is proposed to utilize the case study of consumers and prosumers/SMEs in Thailand based on a decentralized system. The P2P trading is directly the buying and selling of electricity between both consumers and prosumers. It is not a passed intermediary; otherwise, an intermediate process can be cut by this trading in order to save and reduce electricity costs. Preliminary expected impacts of cost structure analysis are summarized in terms of comparisons between the existing electricity trading and the blockchain technology. The results of such preliminary expected impacts show that costs to consumers, prosumers and SMEs obtained from the use of blockchain technology are possibly lower than those of EGAT, PEA, and MEA in the future. In addition, the business model guideline is completely discussed by theory in disruptive innovation.

     

Highly selective hydrogen sensing of Pt-loaded WO3 synthesized by hydrothermal/impregnation methods

Unloaded and 0.25–1.0 wt% Pt-loaded WO₃ nanoparticles were synthesized by hydrothermal method using sodium tungstate dihydrate and sodium chloride as precursors in an acidic condition and impregnated using platinum acetylacetonate. Pt-loaded WO₃ films on an Al₂O₃ substrate with interdigitated Au electrodes were prepared by spin-coating technique. The response of WO₃ sensors with different Pt-loading concentrations was tested towards 0.01–1.0 vol% of H₂ in air as a function of operating temperature (200–350 °C). The 1.0 wt% Pt-loaded WO₃ sensing film showed the highest response of ∼2.16 × 10⁴ to 1.0 vol% H₂ at 250 °C. Therefore, an operating temperature of 250 °C was optimal for H₂ detection. The responses of 1.0 wt% Pt-loaded WO₃ sensing film to other flammable gases, including C₂H₅OH, C₂H₄ and CO, were considerably less, demonstrating Pt-loaded WO₃ sensing film to be highly selective to H₂.     

The effect of carbon nanotube dispersion on CO gas sensing characteristics of polyaniline gas sensor

Polyaniline is one of the most promising conducting polymers for gas sensing applications due to its relatively high stability and n or p type doping capability. However, the conventionally doped polyaniline still exhibits relatively high resistivity, which causes difficulty in gas sensing measurement. In this work, the effect of carbon nanotube (CNT) dispersion on CO gas sensing characteristics of polyaniline gas sensor is studied. The carbon nanotube was synthesized by Chemical Vapor Deposition (CVD) using acetylene and argon gases at 600 degrees C. The Maleic acid doped Emeradine based polyaniline was synthesized by chemical polymerization of aniline. CNT was then added and dispersed in the solution by ultrasonication and deposited on to interdigitated AI electrode by solvent casting. The sensors were tested for CO sensing at room temperature with CO concentrations in the range of 100-1000 ppm. It was found that the gas sensing characteristics of polyaniline based gas sensor were considerably improved with the inclusion of CNT in polyaniline. The sensitivity was increased and response/recovery times were reduced by more than the factor of 2. The results, therefore, suggest that the inclusion of CNT in MA-doped polyaniline is a promising method for achieving a conductive polymer gas sensor with good sensitivity, fast response, low-concentration detection and room-operating-temperature capability.     

Electrolytic admicellar polymerization of pyrrole on natural rubber/clay nanocomposites

Organic–inorganic composites consisting of natural rubber (NR), polypyrrole (PPy), and sodium montmorillonite (Na‐MMT) were synthesized via electrolytic admicellar polymerization. A constant potential of 9 volts was chosen for the synthesis. The PPy concentration was fixed at 100 mM, and the clay contents were varied from 1 to 7 parts per hundred of rubber (phr). The synthesized nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM), together with thermal stability (TGA), mechanical properties, and electrical conductivity (σ_dc) studies. The FTIR spectra indicated the characteristic peaks of both PPy and MMT clay and also evidenced a slight interaction between the PPy chain and the clay layers, verifying the success of electrolytic admicellar polymerization. XRD and TEM results pointed out the good dispersion of clay platelets in the polymer matrix, suggesting an exfoliated structure. The morphology of the nanocomposites was greatly dependent on the amount of MMT clay, especially at a 7 phr loading. The initial modulus and tensile strength of the nanocomposites containing the 7 phr loading were about four and two times higher, compared with unfilled NR/PPy, respectively. Thermal stability studies revealed a slight improvement in the decomposition temperature for the PPy component by the clay layers, whereas the opposite trend was found for the NR component. More interestingly, the electrical conductivity of the admicelled rubber increased significantly (～ 19–32 times) with increasing clay contents from 1 to 7 phr, in comparison with unfilled NR/PPy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Identification of oxidizing agents in aqueous amine-CO2 systems using a mechanistic corrosion model

The purpose of this paper was to perform studies in order to obtain a better understanding of corrosion in an aqueous amine-CO₂ environment. A mechanistic corrosion model, built as a fortran-90 program, is established to identify the oxidizing agents responsible for corrosion reactions. The model incorporates the rigorous electrolyte nonrandom two-liquid (NRTL) equilibrium model and mixed potential theory in order to simulate the concentrations of chemical species and polarization behavior taking place at a metal-solution interface. The simulation results, based on monoethanolamine (MEA) system, indicates that bicarbonate ion (HCO₃⁻) and water (H₂O) are the primary oxidizing agents and hydrogen ion (H⁺) or hydronium ion (H₃O⁺) plays an insignificant role in the reduction reaction.     

Thermal analysis of micromirrors for high-energy applications

This paper presents the results of an investigation of the thermal mechanism between lasers and surface-micromachined micromirrors. Finite element models using ABAQUS are established and used to study the temperature distribution on the surface of micromirrors under high-power laser illumination. It is shown that heat conduction through the gas gap between the mirror surface and the substrate is the dominant thermal dissipation mechanism for high surrounding gas pressure, while heat conduction through the flexures is dominant for low surrounding gas pressure. Based on the simulation results, two novel methods are proposed in order to tolerate more power input under low surrounding gas pressure. The results of optical power testing validate these models, and indicate that these two approaches are efficient in improving micromirror performance for high-energy applications.