We describe the design, fabrication, and operation of several micro-motors that have been produced using integrated-circuit processing [3). Both rotors and stators for these motors, which are driven by electrostatic forces, are formed from 1.0-1.5 µm-thick polycrystalline silicon. The diameters of the rotors in the motors we have tested are between 60 and 120 µm. Motors with several friction-reducing designs have been fabricated using phosphosilicate glass (PSG) as a sacrificial material [ 4,5) and either one, or three polysilicon depositions. INTRODt:CTION Recent publications have discussed possible designs for micro-motors [1,2) based on electrostatic-drive principles. Using technology derived from IC manufacturing processes, we have built and tested several electrostatically driven rotating motors and driven them both in stepwise fashion and through continuous revolutions. Included among the motors are structures with 4 and 8 rotor poles and 6, 12, and 24 stator poles. Typical gaps between the rotors and stators in this first realization of operating micromotors are 2 µm or greater. The technology for the motors, which have rotors that tum on stationary axles fixed to the silicon substrate, is based upon the processes described in [ 4, 5).
Ultrahigh resolution two and three-dimensional optical coherence tomography (OCT) imaging was performed using a miniaturized, two-axis scanning catheter based upon microelectromechanical systems (MEMS) mirror technology. The catheter incorporated a custom-designed and fabricated, 1-mm diameter MEMS mirror driven by angular vertical comb (AVC) actuators on both an inner mirror axis and an outer, orthogonal gimbal axis. Using a differential drive scheme, a linearized position response over +/- 6 degrees mechanical angle was achieved. The flexible, fiber-optic catheter device measured < 5 mm in outer diameter with a rigid length of ~ 2.5 cm at the distal end. In vivo and ex vivo images are presented with < 4 microm axial and ~ 12 microm transverse resolution in tissue.
Abstract-Movable pin joints, gears, springs, cranks, and slider structures with dimensions measured in micrometers have been fabricated using silicon microfabrication technology. These micromechanical structures, which have important transducer applications, are batch-fabricated in an IC-compatible process. The movable mechanical elements are built on layers that are later removed so that they are freed for translation and rotation. A new undercut-and-refill technique that makes use of the high surface mobility of silicon atoms undergoing chemical vapor deposition is used to refill undercut regions in order to form restraining Ranges. Typical element sizes and masses are measured in millionths of a meter and billionths of a gram. The process provides the tiny structures in an assembled form, avoiding the nearly impossible challenge of handling such small elements individually.
Piezoresistive atomic-force-microscope (AFM) cantilevers with lengths of 10 m, displacement sensitivities of (1R=R)=Å = 1.1 2 10 05 , displacement resolutions of 2 2 10 03Å = p Hz, mechanical response times of less than 90 ns, and stiffnesses of 2 N/m have been fabricated from a silicon-on-insulator (SOI) wafer using a novel frontside-only release process. To reduce mass, the cantilevers utilize novel inplane crystallographically defined silicon variable aspect-ratio (INCISIVE) tips with radius of curvature of 40Å. The cantilevers have been used in an experimental AFM data-storage system to read back data with an areal density of 10 Gb/cm 2 . Four-legged cantilevers with both imaging and thermomechanical surface modification capabilities have been used to write 2-Gb/cm 2 data at 50 kb/s on a spinning polycarbonate sample and to subsequently read the data. AFM imaging has been successfully demonstrated with the cantilevers. Some cantilever designs have sufficient displacement resolution to detect their own mechanical-thermal noise in air. The INCISIVE tips also have applications to other types of sensors. [271]
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