Additive microfabrication technique

Zhang, Advani, and Prasad [51,52] also used microfabrication techniques in order to develop a thin, perforated copper foil and use it as a cathode DL in a PEMLC. In addition to the metal DL, an "enhancement" layer was used that consisted of a porous material locafed befween the perforated copper foil and fhe LF plate (CLP was used in fhis study). This layer improved the overall short-term performance and wafer managemenf of fhe cell. Flowever, the authors did not discuss any possible long-term issues related to contaminahon of the membrane due to the use of a copper DL. 

Background. The term microsensor denotes a transducer that, in some fashion, exploits advanced miniaturization technology, whether an adaptation of integrated circuit technology, or some other microfabrication technique. Within the past decade, a myriad of microsensors have been developed, with capabilities for measurement of temperature, pressure, flow, position, force, acceleration, chemical reactions, and the concentrations of chemical species. The latter measurements, of chemical species, are intrinsically more difficult than the measurement of mechanical variables because in addition to requirements of accuracy, stability, and sensitivity, there is a requirement for specificity. 

To build an efficient, high-quality microscale fuel cell, microfabrication techniques need to be combined with appropriate materials such as Nation based membrane electrode assemblies (MEAs). These techniques must be able to produce three-dimensional structures, allow reactant and product flow into and out of the device, process appropriate materials, and should be of low cost. Fortimately, traditional thin film techniques can be modified for microscale fuel cell fabrication, while maintaining their advantages of surface preparation, sensor integration, and finishing or packaging. In addition, other techniques are also available and are discussed in the following sections. 

In addition to specifically increasing the complexity of the pore architecture in the submicrometer range, such porous networks can also be structured three-dimensionally on much larger length scales than the pore size by microfabrication techniques in a top-down approach. This is of major importance for device fabrication and interfacing of the nanoscopic structures with the macroscopic world. 

In bulk micromachining, the master is created by etching the substrate wafer, typically silicon. Silicon is an excellent material for use as an embossing master [5]. It has a high modulus of elasticity and high thermal conductivity, properties that are desirable in a hot embossing tool. In addition, there is a large variety of mature silicon microfabrication techniques available. 

Nanochannel fabrication with microfabrication techniques takes advantage of the rapid development of semiconductor industry and provides the opportunities of fabricating nanochannels of various configurations. In addition, it is relatively... 

Microfabrication techniques can be classified as follows (1) property modification, (2) patterning, (3) subtractive processes and (4) additive processes and packaging [10],... 

Detection has been one of the main challenges for analytical microsystems, as very sensitive techniques are needed as a consequence of the ultrasmall sample volumes used in micron-sized environments. Electrochemical detection (ED) is a very suitable detection principle to be coupled in microchips because it presents the inherent ability for miniaturization without loss of performance and its high compatibility with microfabrication techniques. Similarly, it possesses high sensitivity, its responses are not dependent on the optical path length or sample turbidity, and it has low power supply requirements which are its additional advantages [5-9]. 

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