Starting in 1980s, the NEMS/MEMS technology not only has huge impact on aeronautical and space technology, defense and economic social development, but also infuses a new vibrant energy into the development of mechanics. The intermolecular interactions and their induced surface/interface effects such as stiction, solid/liquid dynamics are the bottleneck problems for the NEMS/MEMS development, which, on the other hand, are also the frontier of the international researches of solid mechanics, physical mechanics and micro/nanomechanics. This project closely follows the national major demands for the NEMS/MEMS and the frontier of the international academia on mechanics. After the accumulation for more than a decade, our original researches, which are extensively acknowledged and highly commended by the peers around the world, provide important guidance on the mechanical design of NEMS/MEMS, lead and facilitate the development of surface mechanical behaviors and related fields of the NEMS/MEMS. This project achieves the following important scientific findings:
1. Proposing for the first time the concept of the electro-elasto- capillarity (EEC); the characteristics of precursor and the interactions between liquid drop and elastic film driven by an electric field are revealed in a multi-scale level by applying an experiment-molecular dynamics-molecular kinetic theory, which provides not only an answer to the Huh-Scriven paradox, but also a breakthrough of the MEMS driving mechanism. Prof. C.J. Kim, who is the top scholar on electrowetting, cited with emphasis and comment highly on the work; the French professor, J. Berthier, whose monograph Micro-Drops and Digital Microfluidics was published in 2013 by Elsevier, introduced our results of the electrowetting on a curved surface in his whole chapter 7; and in chapter 12, the chapter title is EEC and our results consist of a major part.
2. We are among the first in the world who established the lumped model for the pull-in dynamics of micro/nanoactuator under the influence of intermolecular interactions. We propose the original concept of “detachment length”, which is the critical size for the stiction failure and now is a new “basic design parameter in MEMS/NEMS.” We built the experimental platform for the study of adhesion dynamics under multi-field influence with our own intelligence property, through which the mechanism of capillary adhesion was revealed. The related results are cited with emphasis and long paragraphs by the top scholars around the world, such as J. Israelachvili (member of National Academy of Sciences (USA), fellow of the Royal Society (UK)), J.Th.M. de Hosson (member of Royal Netherlands Academy of Arts and Sciences), S. Kitipornchai (fellow of the Australian Academy of Technological Sciences and Engineering) and Wen Shizhu (member of the Chinese Academy of Sciences).
3. In conjunction with the fabrication of the micro biosensor, we proposed a new mechanism for the origin of surface stress; a mechanics model on the surface stress effect of a microcaltilever was called by the Australian scholars as the “Zhang et al. model”, which provides the modeling support of improving the sensor accuracy. Prof. J.F. Stoddart, member of National Academy of Sciences (USA) and fellow of the Royal Society (UK), cited the related results with emphasis.
4. In order to explain the size effect of the Young’s modulus, we proposed for the first time a “semi-continuum lattice model”, which explains the two trends of Young’s modulus increasing and decreasing with the thickness of a nanofilm by incorporating the effects of surface relaxation and surface stress. The above researches facilitate the studies of the surface effects of the related material mechanical behaviors for the micro/nanotechnology. Prof. N.F. Morozov, member of Russian Academy of Sciences, cited the related results with emphasis.
This is an interdisciplinary project and related results are published on the top journals of physics and chemistry such as Physical Review Letters and Journal of the American Chemical Society, and top MEMS and mechanics journals. In 2006, on the International Workshop on the Dispersive Forces of NEMS held in Netherlands, some of results were presented as a sixty-minute plenary lecture, which is the only one from Asia.
The related results have important impact on the surface effect research of MEMS/NEMS, which induces the follow-up works and facilitates a significant development in the area. A dozen domestic and overseas academicians cited scores of times with long paragraphs or further developed the related work.
