This paper reports the impact on performance of flange‐bearing polysilicon micromotors for different self‐assembled monolayer coatings on the surface of released motors. Octadecyltrichlorosilane (OTS) and (3,3,3‐trifluoropropyl) trichlorosilane (TFP) are found to be promising as they significantly improve micromotor performance. Micromotors coated with OTS show a stable rotor speed and minimum operating voltage during a nine‐month testing period. The experiments on gear ratio as a function of wobble cycles indicate that wear in a bearing without OTS coating is significant and results in changes in the gear ratio from the start of micromotor operation by as much as 40%, while the change of gear ratio is within 4% for near 80 million wobble cycles over a nine‐month testing perod for motors with OTS coating. For motors coated with TFP, no stiction and no significant change of the gear ratio are observed for the testing duration. However, the study of gear ratio as a function of wobble cycles shows that the rotor speed fluctuates in the beginning and then stabilizes for wobble micromotors coated with TFP. OTS coating is found to decrease the flange frictional force/torque by a factor of about 1.5. This net reduction of the flange friction force/torque comes about from the combined action of increasing the frictional coefficient from 0.36 to 0.55 and decreasing the normal contact force associated with the rotor/flange contact friction from near 0.8 μN to near 0.3 μN.
Presents results from measurements of static coefficient of friction between materials of interest to microelectromechanical systems (MEMS). The materials studied include silicon, silicon dioxide, and silicon nitride. Two measurement techniques have been used to this study. In the first technique, static friction between two millimeter-sized flat components was measured in a 10-6 Torr vacuum chamber. In the second technique, static friction between a three-millimeter radius aluminum bullet coated with a material of interest and a flat substrate was measured in a approximately 5*10-10 Torr ultra-high vacuum (UHV) chamber. The results show that the coefficient of friction, mu , between silicon and silicon compound contacts in vacuum is in the range 0.2 to 0.7. The coefficients of friction between silicon dioxide/silicon dioxide and silicon dioxide/silicon contacts increase by 55% to 157% with increased exposure to humidity. Additionally, friction between similar materials behaves differently than that between dissimilar materials.
This paper presents results from step-transient measurements on salient-pole, side-drive, polysilicon micromotors operated in different viscosity silicone lubricating oils under different temperatures and excitation voltages. The step transient has been found to be overdamped, with the rise time decreasing with decreasing viscosity of the oil. The rise time, which is in the range of 1 to 20 msec, is around one to two orders of magnitude larger in oil than that in gaseous environments because of the larger viscous drag contribution. In oil, voltages as low as 12 V across 2.5 mu m rotor/stator gaps are sufficient to operate the micromotors. Micromotor speeds up to 12500 rpm are achieved with 110 V excitations across 1.5 mu m rotor/stator gaps. Based on the experimental findings, a model for micromotor dynamics in lubricating oils is examined in which the Coulomb frictional torque is neglected, since micromotor operation in oil is dominated by viscous drag.
Piezoelectric microactuators may be considered as multilayer laminated composites consisting of alternating layers of piezoelectric and non-piezoelectric materials. A generalized analytical formulation of mechanical deformations as a function of applied electric field is derived for an arbitrary lay-up of such laminates. Based on the generalized theory developed, specific formulae for the electromechanical performance of two cantilever microactuator lay-up geometries. including a single piezo/elastic laminate and a bimorph, are derived. In the modeling of the electromechanical performance of piezoelectric microactuators, the present model incorporates both d211 and d222. Furthermore, the elastic properties of both the piezoelectric and the elastic materials have been considered. The developed model is evaluated based on a comparison with results from experiment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.