Microfabrication products

In addition to the term MEMS, categories like microoptoelectromechanical systems (MOEMS), radio-frequency MEMS (RF-MEMS), and MEMS for medical or biomedical application (BioMEMS) have been established. The market for microfabricated devices is still in its infancy and is growing with rates comparable to the first years of microelectronics. According to one market research report, the sales of microfabricated systems was 12 billion in 2004 and is expected to grow with a CAGR of 16% to 25 billion in 2009 [6]. Recent extensions of fields of application are consumer, entertainment, and homeland security. Upcoming new devices are MEMS microphones, microenergy sources, micropumps, chip coolers, and micromachined wafer probes, and this will definitely not be the end of new developments. 

In order to be protected against environmental interference, microelectronic or microfabricated chips must be enclosed into specific packages. For some micromechanical sensors, cap wafers with etched cavities are attached hermetically onto the device wafers using anodic, eutectic, or glass frit bonding. 

To form effective bonding between these wafers, very smooth surfaces are required, which are produced by means of CMP. After the wafer bonding and singulation of the dies, the fragile structures are protected, sometimes even under high-vacuum conditions, and can then be integrated into the system. 

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Microfabrication techniques used for the production of MEMS (micro electro-mechanical systems) have been successfully used to produce highly efficient micro fluidic systems. 

Of course, the benefits of microfabricated and stractured reactors are also applicable to even larger scale processes. For example, Evonik s development of a production-scale microstructured reactor for vinyl acetate manufacture (150000t per annum) claims depreciation and operating cost savings of 3 million per year [25]. 

Innovation - advocates and opponents origin from microtechnology list of microfabrication techniques selectivity and efficiency as main driver for industrial implementation special properties and general advantages of micro reactors process-development issues BASF investigations on liquid/liquid and gas-phase reactions micro reactors as ideal measuring tools production in micro reactors as exception, the rule will be transfer to mm-sized channels [111],... 

Today s use of microtechnical products microfabrication techniques general advantages of micro flow parallelization for screening steep transport gradients plant safety numbering-up industrial response outlook on market [222]. 

Schmidt, M.A., Microfabricated chemical systems for product screening and synthesis, in Hoyle, W. (Ed.), Automated Synthetic Methods for Specialty Chemicals, pp. 14-24, Royal Society of Chemistry, Cambridge (2000). 

Lu, H., Schmidt, M. A., Jensen, K. F., Photochemical reactions and online product detection in microfabricated reactors, in Matlosz, M., Ehrfeld, W., Baselt, j. P. (Eds.), Microreaction Technology - IMRET 5 Proc. 5th International Conference on Microreaction Technology, pp. 175-184, Springer-Verlag, Berlin (2001). 

M. A., Microfabricated chemical systems for product screening and synthesis, in... 

Microfabrication techniques with the features of integration, reproduction and precision are particularly suitable for the implementation of miniaturized designs and significant reduction in product costs. A miniaturized magnetic resonance probe for on-line/in-line flow studies can be microfabricated by combining an rf coil [45, 46] with microfabricated gradients [47] and electronics [48] around a small tube/capillary. 

Clearly this approach is not suitable for preparing large quantities of products, its main purpose being to permit the greatest amount of information to be obtained concerning the reactivity of a new material. If the coreactant is expensive and/or difficult to prepare then this procedure is invaluable. However, it is important to consider that the quantities of derivatized polymer obtained in this approach [ 10-6 mole based on -N=C repeat unit] might well represent sufficient material if such a process were to be used for the direct preparation of chemically modified electrodes (12), or incorporated into a planar microfabrication process, with which it would appear to be compatible. 

Recent developments in microsystems technology have led to the widespread application of microfabrication techniques for the production of sensor platforms. These techniques have had a major impact on the development of so-called Lab-on-a-Chip devices. The major application areas for theses devices are biomedical diagnostics, industrial process monitoring, environmental monitoring, drug discovery, and defence. In the context of biomedical diagnostic applications, for example, such devices are intended to provide quantitative chemical or biochemical information on samples such as blood, sweat and saliva while using minimal sample volume. 

All of the above trends make a planar platform configuration the ideal choice for the development of such sensors due to the compatibility of this geometry with a range of microfabrication technologies, the availability of low-cost materials for the production of such platforms and the robust nature of planar configurations when compared with alternatives based on optical fibres. 

It is important to note that the enhancements mentioned above are achievable using current planar microfabrication techniques and the resultant sensor chips are mass-producible, low-cost and disposable and also have the potential to be integrated into a variety of diagnostic microsystems. This work has significant implications for the production of low-cost, yet efficient measurement platforms for applications in modem society. 

Lu H, Schmidt MA, Jensen KF (2001) Photochemical Reactions and On-Line UV Detection in Microfabricated Reactors. Lab Chip 1 22-28 Manz A, Harrison DJ, Verpoorte EMJ, Fettinger JC, Ludi H, Widmer HM (1991) Miniaturization of Chemical-Analysis Systems - A Look into next Century Technology or just a Fashionable Craze. Chimia 45 103-105 McCreedy T (1999) Reducing the Risks of Synthesis. Chem Ind 15 588-590 McCreedy T (2000) Fabrication Techniques and Materials Commonly Used for the Production of Microreactors and Micro Total Analytical Systems. Trac Trends Anal Chem 19 396-401... 

Microchips fabrication with integrated tips can result in improved spray repeatability and efficiency since alignment and dead volume are not a critical issue anymore. However, production of fine and robust nanospray emitters as an integral part of a microdevice is not trivial, and highly specialized microfabrication procedures are required. Microfluidic devices with integrated ESI tips have been produced for infusion experiments, but to date, no microchips with such a design was fabricated for CE separation prior to MS detection. 

The development of microfabrication technologies for ceramic and metallic materials has significantly promoted, during the last decade, research in the field of microreactors, characterized by higher specific productivity, better control of operating conditions and a higher standard of intrinsic safety than large-scale reactors [33, 34]. 

In the early years of AFM operation, the cantilevers were cut from a metal foil, and the tips were made from crushed diamond particles, picked up by a piece of eyebrow hair, and painstakingly glued manually on the cantilevers. This situation has changed completely since the methods for mass production of cantilevers with integrated tips were developed. A review of various methods for making cantilevers using standard microfabrication techniques was published by Albrecht et al. (1990), and an improved method is described by Akamine et al. (1990). Those AFM cantilevers with integrated tips are now available commercially. 

Organic-silica hybrid materials have been used for multi-photon microfabrication. These include the acrylate-functionalized oligosiloxanes known as ORMOCERs, which have been polymerized by radical processes using conventional IP radical iniatitors, such as c.2 [221,234]. Commercial poly(dimethylsiloxane)-based resists containing vinyl and Si-H functionalities use two different 2PA-induced processes hydrosilylation catalyzed by the photodecomposition products of Cp PtMes (Cp = ti -methylcyclopentadienyl) and radical initiation by c.4 (Fig. 13) [235]. The former process was complicated by thermally-induced polymerization. 

Many of the devices that have thus far been envisioned as products of nanotechnology (e.g., nanoscale environmental sensors, information processors. and actuators) cannot be produced by the large-scale microfabrication techniques currently in use. The further development of nanotechnology hinges on the understanding and manipulation of physical laws and processes at the nanometer level, such as electronic, interatomic, and mter-molecular interactions that can be manipulated lu allow efficient assembly of nanostructures. 

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