MEMs technologies

Yamazaki Y. 2004. Application of MEMS technology to micro fuel cells. Electrochim Acta 50 663 -666. 

Maboudian, R. (1998) Surface processes in MEMS technology Surface Science Reports, 30 (6-8), 207-269. 

The micro mixer was fabricated from two plates by standard MEMS technology, using deep reactive ion etching (DRIE) [48]. Anodic bonding is used for sealing the plates. 

Besser et al. [86] studied the reaction in a silicon reactor fabricated by applying MEMS technology, namely photolithography and DRIE by inductively coupled plasma. Each reactor incorporated dual gas inlets, a pre-mixer, a single reaction channel and an outlet zone where the product flow was cooled (see Figure 2.54). The single channel was 500 pm wide, 470 pm deep and 45 mm long. 

Preferential Carbon Monoxide Oxidation 2 [PrOx 2] Single-plate Reactor Based on MEMS Technology... 

Bednarova et al. [87] designed a single-plate PrOx reactor for a 1 W fuel cell based on MEMS technology, similar to [PrOx 1], The results of the simulation work described above were applied to optimize the reactor performance. The plate carried a pre-mixer and 29 channels each 12 mm long, 500 pm wide and 400 pm deep. Flow uniformity was verified by simulations. Full conversion of carbon monoxide was achieved at much lower temperature with [PrOx 1] and the selectivity towards carbon dioxide was 40%. 

Franz et al. [93] developed a palladium membrane micro reactor for hydrogen separation based on MEMS technology, which incorporated integrated devices for heating and temperature measurement. The reactor consisted of two channels separated by the membrane, which was composed of three layers. Two of them, which were made of silicon nitride introduced by low-pressure chemical vapor deposition (0.3 pm thick) and silicon oxide by temperature treatment (0.2 pm thick), served as perforated supports for the palladium membrane. Both layers were deposited on a silicon wafer and subsequently removed from one side completely... 

MEMS technology also allows embedding of actuators and sensors in single reactor channels. Despite problems with temperature robustness, a solution must be found to transport the signals from the micro channels to the central process control system. To avoid a confusing cable set-up ( spaghetti conditions ), it is desirable to process the sensor data on-site, for example in an A/D converter, and to feed the digital data in a common bus system [13]. 

MEMS (microelectromechanical systems) are systems with small device sizes of 1-100 pm. They are typically driven by electrical signals. To fabricate such systems materials like semiconductors, metals, and polymers are commonly used. MEMS technology fabrication is very cost-efficient. The structures are transferred by processes, which are applied to many systems on one substrate or even many of them simultaneously. The most important fabrication processes are physical vapor deposition (PVD), chemical vapor deposition (CVD), lithography, wet chemical etching, and dry etching. Typical examples for MEMS are pressure, acceleration, and gyro sensors [28,29], DLPs [30], ink jets [31], compasses [32], and also (bio)medical devices. 

The first spectra obtained with the mass spectrometer date back to 2007, where gas mixtures of Neon, Air and Argon were measured [23], This PIMMS-device was the first in which the separation principle relied on the new Synchronous Ion Shield (SIS) Separator, and the first proof-of-principle for the total integration of a mass spectrometer using batch processes of MEMS technology. Also a quantitative correlation could be stated from the peak heights for different gas concentrations. 

The transfer of this principle also benefits from the characteristic conditions that count for microfluidic systems. By using MEMS technologies the geometry of the steam nozzles can be reduced drastically without losing relative accuracy. Thus, the overall dimensions of the pump and also the amount of steam that is necessary for operation is reduced. Another advantage of a micro-diffusion pump is that the capillary forces overbalance gravity forces, which are decisive in the macroworld. Hence it is possible to construct a pump that can be operated orientation-independent. 

The development of MEMS technology during the 80s induced a strong research effort focused on fluid and heat flow studies in microchannels. Since then, various silicon-based systems such as microbiochips, MOEMS, etc... have contributed to reinforce this trend and a lot of experimental results were published. In parallel to these studies, very compact heat exchangers for air conditioning purposes were developed and have lead to research programs on minichannels. In the same manner, the possible use of such minichannels in other systems such as reformers, fuel cells,... has also produced considerable interest in this field. 

Membranes fabricated using the MEMS technology are finding an increasing number of applications in sensors, actuators, and other sophisticated electronic device. However, the new area of application of MEMS is creating new materials demands that traditional silicon cannot fulfill [43]. Polymeric materials, also in this case, are the optimal solution for many applications. Microfabrication of polymeric films with specific transport properties, or micromembranes, already exists, and much work is in progress [44-50]. 

Miniature batteries and fuel cells have been attracting many research groups. The prospective potential for miniaturization such as in MEMS technology requires development of microfuel cells. 

This chapter reviews selected topics related to p-DMFCs and MEMS technologies for portable power sources emphasis is on the results of recent studies carried out to clarify the factors affecting the performance of p-DMEC as a new power source. 

The use of MEMS technology in the health care arena leads to the developments of indispensable sophisticated intelligent devices. The miniaturization of these analytical devices is critical since it wiU enable the analysis of large number of drugs per sample and may be used directly with small biopsy s samples or small volumes of body fluids. This in turn leads to fast response time, sensitive and cost-effective analysis. 

Using MEM technology, the experimental high-strength and heat-resistant titanium alloys, which represent a plastic matrix, strengthened with intermetallics of different volume and shape, were produced. 

Titanium alloys of MEM technology with intermetallic strengthening possess high strength and heat resistance and preserve the necessary ductility. 

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