Aligning Optical Fibers by Means of Actuated MEMS Wedges

Microelectromechanical systems (MEMS) of a proposed type would be designed and fabricated to effect lateral and vertical alignment of optical fibers with respect to optical, electro-optical, optoelectronic, and/or photonic devices on integrated circuit chips and similar monolithic device structures. A MEMS device of this type would consist of a pair of oppositely sloped alignment wedges attached to linear actuators that would translate the wedges in the plane of a substrate, causing an optical fiber in contact with the sloping wedge surfaces to undergo various displacements parallel and perpendicular to the plane. In making it possible to accurately align optical fibers individually during the packaging stages of fabrication of the affected devices, this MEMS device would also make it possible to relax tolerances in other stages of fabrication, thereby potentially reducing costs and increasing yields. In a typical system according to the proposal (see Figure 1), one or more pair(s) of alignment wedges would be positioned to create a V groove in which an optical fiber would rest. The fiber would be clamped at a suitable distance from the wedges to create a cantilever with a slight bend to push the free end of the fiber gently to the bottom of the V groove. The wedges would be translated in the substrate plane by amounts Dx1 and Dx2, respectively, which would be chosen to move the fiber parallel to the plane by a desired amount Dx and perpendicular to the plane by a desired amount Dy. The actuators used to translate the wedges could be variants of electrostatic or thermal actuators that are common in MEMS

Resonant frequency of gold/polycarbonate hybrid nano resonators fabricated on plastics via nano-transfer printing

We report the fabrication of gold/polycarbonate (Au/PC) hybrid nano resonators on plastic substrates through a nano-transfer printing (nTP) technique, and the parametric studies of the resonant frequency of the resulting hybrid nano resonators. nTP is a nanofabrication technique that involves an assembly process by which a printable layer can be transferred from a transfer substrate to a device substrate. In this article, we applied nTP to fabricate Au/PC hybrid nano resonators on a PC substrate. When an AC voltage is applied, the nano resonator can be mechanically excited when the AC frequency reaches the resonant frequency of the nano resonator. We then performed systematic parametric studies to identify the parameters that govern the resonant frequency of the nano resonators, using finite element method. The quantitative results for a wide range of materials and geometries offer vital guidance to design hybrid nano resonators with a tunable resonant frequency in a range of more than three orders of magnitude (e.g., 10 KHz-100 MHz). Such nano resonators could find their potential applications in nano electromechanical devices. Fabricating hybrid nano resonators via nTP further demonstrates nTP as a potential fabrication technique to enable a low-cost and scalable roll-to-roll printing process of nanodevices

Development and Optimization of Integrative MEMS-Based Gray-Scale Technology In Silicon For Power MEMS Applications

As the field of micro-electro-mechanical systems (MEMS) has diversified, a growing number of applications are limited by the current planar technology available for fabrication. Gray-scale technology offers a method of fabricating 3-D structures in MEMS utilizing a single lithography step. Before gray-scale technology can be accepted as a universal/standard fabrication technique, methods for controlling the silicon profiles and integrating the necessary process steps must be developed. Here, an optical mask design method is outlined by which an arbitrary profile may be defined in a photoresist film, and a study is presented regarding the control of etch selectivity during deep reactive ion etching (DRIE). These results are then used to develop large controlled gradient silicon structures for the MIT micro-engine device that may be integrated into an existing process flow

Development of Ground-testable Phase Fresnel Lenses in Silicon

Diffractive/refractive optics, such as Phase Fresnel Lenses (PFL's), offer the potential to achieve excellent imaging performance in the x-ray and gamma-ray photon regimes. In principle, the angular resolution obtained with these devices can be diffraction limited. Furthermore, improvements in signal sensitivity can be achieved as virtually the entire flux incident on a lens can be concentrated onto a small detector area. In order to verify experimentally the imaging performance, we have fabricated PFL's in silicon using gray-scale lithography to produce the required Fresnel profile. These devices are to be evaluated in the recently constructed 600-meter x-ray interferometry testbed at NASA/GSFC. Profile measurements of the Fresnel structures in fabricated PFL's have been performed and have been used to obtain initial characterization of the expected PFL imaging efficiencies.Comment: Presented at GammaWave05: "Focusing Telescopes in Nuclear Astrophysics", Bonifacio, Corsica, September 2005, to be published in Experimental Astronomy, 8 pages, 3 figure

Characterization of Dynamic Friction in MEMS-Based Microball Bearings

Rolling element bearing is a well-known concept in macroscale machinery applications. They are prospective candidates for friction reduction in microelectromechanical system (MEMS), as well as for providing stable, robust support for moving micromechanisms. The characteristics of rolling element bearings need to be investigated to facilitate their applications in MEMS. It is well understood that the measured data on the macroscale cannot be directly applied to the microscale. This paper presents an in-situ noncontact experimental system to characterize the friction behavior of microball bearings on the microscale. The methodology presented in this paper provides a useful template to study the dynamical behavior of linear microball bearings with a variety of materials, geometries, and surface qualities. The system, actuated by a motor, affords wide ranges of motion for the determination of the coefficient of friction (COF) without any interference due to the measurement system. With careful optimization, the error in measurement has been reduced to 2%. Different designs of microball bearings demonstrated an average static COF of 0.01 and an average dynamic COF of 0.007 between stainless-steel and silicon-micromachined contacting surfaces at 27﯃ and 40% relative humidity

Hard Film Coatings for High-Speed Rotary MEMS Supported on Microball Bearings

Abstract: Titanium Nitride (TiN) and Silicon Carbide (SiC) coatings deposited on the surface of silicon raceways are evaluated in a microturbine. Nanoindentation is employed to study the properties of the hard-thinfilm/silicon raceway system and the tribological platform is evaluated through turbine operation curves. TiN films are shown to stay intact over the speeds and forces in the range relevant to future power and energy applications applications, (500-10,000rpm and 10-50mN, respectively), while SiC films wear almost instantaneously. Evaluation of the dynamic friction torque versus normal load relationship between the TiN and bare Si systems suggest the gradual generation of wear debris, comprised of either the raceway or microballs, is negating the benefits of enhanced mechanical properties in TiN

Substrate interconnect technologies for 3-DMEMS packaging

We report the development of 3-dimensional silicon substrate interconnect technologies, specifically for reducing the package size of a MOSFET relay. The ability to interconnect multiple chips at d on a single substrate can significantly improve device performance and size. We present the process development of through-hole interconnects fabricated using deep reactive ion etching (DRIE), with an emphasis on achieving positively tapered, smooth sidewalls to ease deposition of a seed layer for subsequent Cu electroplating. Gray-scale technology is integrated on the same substrate to provide smooth inclined surfaces between multiple vertical levels (>100 lm apart), enabling interconnection between the two levels via simple metal evaporation and lithography. The developments discussed for each technique may be used together or independently to address future packaging and integration needs

Vision-Based Microtribological Characterization of Linear Microball Bearings

Microball bearings can potentially provide robust and low friction support in micromachines such as micromotors and microgenerators. Their microtribological behavior needs to be investigated for design and control of such micromachines. In this paper a vision-based, non-intrusive measurement method is presented for characterization of friction in linear microball bearings. Infrared imaging is used to directly observe the dynamics of microballs and track the motion of bearing components. It is verified that microballs roll most of the time with occasional sliding or bumping resulting from fabrication nonuniformity. The friction-velocity curve demonstrates evident hysteresis. The dependence of frictional behavior on several factors is studied