Progress through Mechanics:
The Era of Microelectromechanics
and Nanotechnology
Copyright ©2000, Robert M. and Mary Haythornthwaite Foundation
I. Chasiotis*
Graduate Student at the California Institute of Technology
Pasadena, CA
ichasiot@its.caltech.edu
Winner of the Robert M. and Mary Haythornthwaite Foundation
Founders Prize and Grant, 2000-2001
The advent of the advanced microelectronics age two decades ago marked the beginning of a new information and communications era. Multidisciplinary technologies are developing in order to meet increasingly complex requirements. In particular, experience in mechanics is being transferred, modified and further improved to address new challenges. Information technologies play a leading role today, and the necessary hardware remains significantly mechanical in nature. CD-ROM and DVD-ROM drives and hard drives integrate mechanical, electronic, magnetic and optical components that need to be ultra-small and light, as well as reliable and robust.
Because of the significance of these applications and the maturity level of microelectronics, research has been directed in the last decade to the "small world," namely to new micro- and nano-technologies. Parallel progress in mechanics and electronics has created a new technology, incorporating mechanics and electronics under the name of Micro Electro Mechanical Systems (MEMS) that is rapidly becoming a most promising technology, with seemingly unlimited potential to dominate future technological developments. The world market for MEMS is estimated to soar from 14 billion dollars this year to 38 billion dollars by the year 2002 (1). Mechanics will play a leading role in the development of new MEMS applications, including devices that perform either basic functions, such as airbag accelerometers and radio frequency micro-switches for wireless communications or advanced tasks, such as micro-gyroscopes, digital micro-mirror displays and pico-satellites.
These new systems with embedded micro-actuators, micro-sensors, and control devices developed for guidance, navigation, motion control and high resolution flow visualization can provide experimental evidence about small-scale phenomena and thus verify fundamental principles in the microcosm. Applications in micro-fluidics contribute to effective drug delivery while BIOMEMS are increasingly gaining the interest of the engineering and scientific community. Cost-effective methods will emerge with the mass production of MEMS that consume minimal energy and are fabricated with little chemical waste. New MEMS products will incorporate advanced piezoelectric, ferroelectric, or magnetostrictive smart materials with particular applications and functions. They will allow "intelligent" micro machines to function with unmatched performance. Whenever mechanics can replace electronics, it provides superior functionality and is not subject to undesirable electronic noise. For example, the classical electronic components of fiber-optic networks are now being replaced with optical MEMS switches that enable the creation of arrays of miniature high capacity switches that will play a critical role in the development of large-scale optical switches in future fiber-optic networks.
Although MEMS design and operation is a new field, newer technologies have emerged in the form of Micro Opto Electro Mechanical Systems (MOEMS) and BIOMEMS. Possible are future NEMS (Nano Electro Mechanical Systems) given that the electronics community operates at the nanoscale for reproducing features with dimensions on the order of 150nm. Photonics technologists are targeting 30nm for the next decade.
The mass production of MEMS with identical geometries guarantees consistent performance and faithful execution of the design standards. However, the reliability of these devices has to be meticulously assessed and this is a vital requirement for further improvements and more widespread adoption. The recently demonstrated 1 MHz micro-motors (2) suggest the extraordinary potential of MEMS, but short lifetimes indicate an immediate need for a better understanding of the actual mechanisms that lead to failure. Experimental techniques for measuring mechanical and material properties must be developed to address the critical and fundamental questions of constitutive and fracture behavior at realistic MEMS micro-scales. Materials testing and stress analyses are key parts of this development and existing experimental methods need to be refined or completely redesigned to match the new size challenges and requirements. Tools necessary for visualization of deformations on a small scale are already available. Scanning Electron Microscopes are instruments capable of high resolution, while the newly developed Atomic Force Microscope provides unprecedented resolving power and unparalleled flexibility to operate in virtually any environment to facilitate material tests under a variety of conditions. Computational mechanics and finite element methods have reached the level of maturity needed to develop new CAD and modeling capabilities for micro-devices and new and improved manufacturing techniques.
These new challenges need to be met by a methodical effort of the mechanics community concerned with MEMS. Device design, manufacturing, testing and reliability assessment should be addressed in a coordinated effort that weighs all the aforementioned aspects of MEMS development equally. To date, the manufacturing sector has demonstrated considerable activity in attracting the majority of financial support and the attention of the academic and industrial communities. Presently, the micromechanics field is application driven, and reliability has been addressed without an adequate understanding of mechanics. Only isolated cases have been studied without developing the appropriate general tools and methods to resolve the issue of mechanical integrity. Novel and important applications require a mechanics-based reliability assessment. Before the introduction and perfection of new micromachines can be accomplished, the mechanics community needs to demonstrate the requisite progress. Residual stresses, stress concentration effects at micro-notches and corners and failure by crack propagation are becoming increasingly significant, often causing a temporary halt to the research on new microstructures. The required experimental and analytical tools are, in principle, already available at a level of development that makes such investigations feasible. The mechanics research community must pay careful attention to the early stages of micro technology development and coordinate its efforts.
Today, many aspects of mechanics are being reinvented, although at varying scales. The rapidly developing field of MEMS parallels the progress in microelectronics thirty years ago that led to modern high-power microprocessors and ultra-fast computers. A coordinated interdisciplinary effort and continuous support of the mechanics community are essential to fully develop the new worlds of microelectromechanics and nanotechnology.
(1) Source: Nexus Task Force
(2) Sandia National Labs
* [Partially Edited by Adjudication Committee Members For Publication Purposes]
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