A Message From the Guest Editors
The rapid emergence of miniaturized products today is demanding the production of components and assemblies in the submillimeter to a few-millimeter (i.e., micro/meso-scale) range with manufactured features perhaps in the range of a few to a few hundred microns. These fields include optics, electronics, medicine, biotechnology, communications, and avionics, to name a few. (Specific applications include microscale fuel cells; fluidic microchemical reactors requiring microscale pumps, valves, and mixing devices; biomedical implants, microholes for fiber optics; micronozzles for high-temperature jets; micromolds; and many others.) However, a critical assessment of the present status reveals that the prevalent manufacturing methods are MEMS-based and limited in terms of usable materials, feature geometry, and accuracy, while the manufacture of high-accuracy and -precision mechanical components is still being done by ultraprecision CNC machine tools. It is also apparent that there is an absence of a continuum of manufacturing capabilities that spans the whole nano-to-macro range. Arguably, the largest gap exists at the micro/meso-scale.
In the United States, the dearth of development of high relative accuracy 3D micro/meso-scale fabrication and assembly methods and equipment may, in part, be a product of the evolutionary development of MEMS here. In the 1990s, the United States focused on exploiting silicon planar lithography as the core technology for microstructure fabrication, whereas, at the same time, Europe and Japan explored a wide variety of technologies. These technologies focused on both a wide range of fabrication methods and a wide range of materials, including extensions to more traditional manufacturing processes. In Europe and Japan, where MEMS was driven by mechatronics and mechanical engineering, there was more focus on the fabrication and assembly of discrete products, whereas MEMS in the US, being driven by the semiconductor industry, viewed such work as inconsistent with the paradigm of batch fabrication.
The push toward product miniaturization has brought into the forefront the need for the manufacture of micro/meso-scale high-precision components in large quantities at low cost from materials and with features that existing MEMS/NEMS processing methods cannot meet. Yet, the conventional methods applied for this purpose have also reached their technological limit mainly because of the lack of understanding of the properties of manufacturing methods at the micro/meso-scales and the lack of more efficient manufacturing equipment. This realization was the motivation for this Special Issue of the Journal. Our aim was to respond to the increased research activity related to the theoretical and pragmatic aspects of micro/meso-scale manufacturing technologies. In particular, emphasis was placed on those technologies that complement the ubiquitous MEMS-based methods.
The selection of papers for this Special Issue was made from the contributions directly submitted in response to the solicitation, as well as papers from the backlog that fit the general theme. We would wholeheartedly like to thank all the authors for their effort in submitting their work to this issue. We also would like to thank all the reviewers whom we asked for assistance in reviewing the papers, more often than not on very short notice.