IC-processed micro-motors: design, technology, and testing

Micro-motors having rotors with diameters between 60 and 120 μm have been fabricated and driven electrostatically to continuous rotation. These motors were built using processes derived from IC (integrated circuit) microcircuit fabrication techniques. Initial tests on the motors show that friction plays a dominant role in their dynamic behavior. Observed rotational speeds have thus far been limited to several hundred r.p.m., which is a small fraction of what would be achievable if only natural frequency were to limit the response. Experimental starting voltages are at least an order of magnitude larger than had been expected (60 V at minimum and above 100 V for some structures). Observations of asynchronous as well as synchronous rotation between the driving fields and the rotors can be explained in terms of the torque/rotor-angle characteristics for the motors

Integrated movable micromechanical structures for sensors and actuators

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 with 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. An undercut-and-refill technique, which 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 flanges. Typical element sizes and masses are measured in micrometers and nanograms. The process provides the tiny structures in an assembled form avoiding the nearly impossible challenge of handling such small elements individually

Optical switch using frequency-based addressing in a microelectromechanical systems array

Embodiments of the present invention provide structures for microelectromechanical systems (MEMS) that can be sensed, activated, controlled or otherwise addressed or made to respond by the application of forcing functions. In particular, an optical shutter structure suitable for use in an optical switch arrangement is disclosed. In one embodiment, an optical shutter or switch can be scaled and/or arranged to form arbitrary switch, multiplexer and/or demultiplexer configurations. In another embodiment of the present invention, an optical switch can include: a shutter; and a flexure coupled to the shutter, whereupon a vibration transmitted to the flexure when in the presence of a resonant frequency causes the shutter to move across an opening for the passage of an optical signal

Optical properties of microlenses fabricated using hydrophobic effects and polymer-jet-printing technology

We describe high-precision microlenses with excellent optical characteristics. The lenses are formed precisely at desired locations on a wafer using a polymer-jet system in which hydrophobic effects define the lens diameter and surface tension creates a high-quality optical surface. To make the lenses, we defined hydrophilic circular regions at desired locations using photolithography to pattern a 0.2-pm thick Teflon (hydrophobic) layer on a quartz substrate, as shown in Figures 1 and 2. Then, using a polymer-microjet printing system (Figure 3), we dispense an exact amount of UV-curable polymer within hydrophilic circles to obtain microlenses having desired optical properties [ 13. Figure 4 shows that adjusting the volume of the UV-curable optical epoxy within a hydrophilic circle of a given diameter changes the curvature of the microlens. The step resolution of the microlens volume is determined by the average droplet size (~25pL) of the polymer-jet print head. This hybrid method enables us to define the locations and diameters of microlenses with a ±1 μm precision as well as to control the curvatures of the microlenses accurately

Integrated Ultrasonic Transducer

Ultrasonic transducers composed of integrated assemblies of double-diffused MOS transistors (DMOST) and thin-film piezoelectric transducing elements are described. The entire transducer is built on a single-crystal silicon wafer and offers a number of attractive features including: small size and correspondingly precise localization of the sensitive element, a response that can be predicted by relatively simple theory, a large bandwidth, and a possibility of producing arrays of sensors together with other signal-processing elements in a single processing sequence. The piezoelectric film (zinc oxide) is sputtered either in the gate region of a double-diffused H6S transistor (making the so-called PI-MOST ) or adjacent to the gate electrode of a double-diffused MOS transistor. The transducer~ be excited in various ways: (1) in a thickness mode from the bare silicon surface opposite the piezoelectric-coated region; (2) in a flexural mode caused by bending the silicon wafer; (3) end excitation by surface motions either normal or transverse to the edge of the wafer; (4) by surface waves. Various of these modes are characterized by high sensitivity to strain, low conversion loss, large bandwidth, and good response at very low or very high frequencies

Integrated Ultrasonic Transducer

The typical transducer considered consists of a piezoelectric film, and associated.electrodes, connected to one gate of a dual-gate field-effect transistor in the silicon wafer on which the piezoelectric film is situated. An individual transducer responds to various modes of excitation (flexural, surface, bulk) at frequencies which may range from far below one Hertz to hundreds of megahertz. The second gate of the field-effect transistor can be used for electrical amplitude control or for mixing purposes, Connection of a number of these small transducers together to form arrays permits realizing ultrasonic receiving devices having variable directivity, and progammable surface-wave signal processors

Microfabricated torsional actuator using self-aligned plastic deformation

We describe microfabricated torsional actuators that are made using self-aligned plastic deformation in a batch process. The microactuators are formed in single-crystal silicon and driven by vertical comb-drives. Structures have been built that resonate at frequencies between 1.90 and 5.33 kHz achieving scanning angles up to 19.2 degrees with driving voltages of 40 V_(dc) plus 13 V_(ac). After continuous testing of 5 billion cycles at the maximum scanning angle, there appears to be no observable degradation or fatigue of the plastically deformed silicon tors ion bars. We present measured results obtained with MEMS scanning mirrors; the actuators may be useful for many other MEMS applications