L. Paratte

Low-cost technology for multilayer electroplated parts using laminated dry film resist

Abstract An innovative technology for the realization of key elements of a microfabricated reduction unit is presented. In view of integrating the functions of gear, pinion and axle into one element, multilevel metal electroplating in a negative dry film resist mould (Riston) is used. Easier processing, inherent planarization for multilevel 3-D structures, vertical sidewalls and high thicknesses (20–50 μm/level) are shown to be the main key features of dry films. To demonstrate the process feasibility, a gear and pinion set with upper and lower axle posts has been realized with four levels of nickel.

A 1.5-V-supplied CMOS ASIC for the actuation of an electrostatic micromotor

The use of electrostatic forces in micromechanical systems is well known, but quite high voltages are needed to produce usable forces. In this perspective paper, a 1.5-V battery-supplied integrated circuit able to drive an electrostatic micromotor is presented. The application-specific integrated circuit (ASIC) can output signals up to 80 V, with low-voltage controlling signals. It is especially designed for portable (wristwatch-like) applications. High voltage can be produced by either switching or charge-pumping power supplies.

A rigid ring electrostatic harmonic wobble motor with axial field

The working principle of a novel wobble electrostatic micromotor and the fabrication of a prototype are presented. Surface micromachining of LPCVD (low-pressure chemical vapor deposited) polysilicon layers and sacrificial dioxide layer technology are used. For the prototype, a very high harmonic reduction of 1:20000 can be obtained through the vertical wobbling motion of a 200- mu m-diameter ring. Due to the planar technology aspect ratio, the electrostatic top drive of the wobbling ring used allows a much higher motor torque as in the case of direct drives or even harmonic side drives. Flexible elements permit the connection from the wobbling ring to a purely rotating hub.<<ETX>>

Design of an integrated electrostatic stepper motor with axial field

Abstract A variable capacitance, top-drive synchronous, electrostatic stepper motor model is presented. A surface micromachining technique is proposed for its fabrication. Simple theoretical modelling predicts that the Coulomb dry friction torque dominates the viscous and inertial torques over a large speed range. Dry friction coefficient values between thin-film-covered silicon chips have been measured by means of a pin-on-disc tribometer machine from CSEM S.A. Values between 0.3 and 0.4 have been found for LPCVD silicon nitride on LPCVD polysilicon, polysilicon on itself and silicon nitride on itself, in agreement with previous work. This result shows that a material pair with better friction behaviour still has to be found.

Electrodeposited electrostatic rigid-rotor wobble motors on silicon

Abstract A new design of a variable-capacitance (VC) vertically wobbling electrostatic micromotor fabricated on silicon is presented. The movement of the rotor is similar to that of a coin flipped on a table, as reported in our previous work on a first design, but here the rotor is completely rigid instead of being flexibly attached to a rotating ring. First, a theoretical model has been developed to describe the dynamics and relate the dimensions and driving voltage to the maximum mechanical output speed and power. Using this model, motors with rotors of 1–3 mm diameter have been designed to meet the typical power range of wristwatch motors (about 1 μW). They have been fabricated on silicon, utilizing in particular electroplating of nickel for the rotor parts, which where post-assembled. Successful operation of a motor having a rotor of 2 mm diameter has been achieved with driving voltages between 20 and 80 V. A maximum speed of 2.7 rpm has been measured.

A 1.5 V supplied, CMOS ASIC for the actuation of an electrostatic micromotor

The use of electrostatic forces in micromechanical systems is well known but needs quite high voltages to produce usable forces. In this perspective paper, we present an autonomous, nonresonant, open-loop, 1.5 V battery-supplied high voltage integrated circuit able to drive an electrostatic micromotor, for opening the way to future portable applications (wristwatch like).

Numerical simulations of planar electrostatic wobble motors

We present a numerical study of the electrostatic wobble motor. Both finite-element calculations and analytical approaches are used to calculate the torque exerted by the electrodes. Both methods give very similar results, validating an analytical approach. We also study the dynamic behaviour of this type of motor. We show how to optimize the torque by optimally adapting mechanical and electrical parameters.

A novel comb-drive electrostatic stepper motor,

A novel side-drive, electrostatic variable capacitance micromotor has been fabricated. A technique involving the surface micromachining of the three LPCVD (low-pressure chemical vapor deposited) polysilicon layers and the sacrificial silicon dioxide layers was used. Compared to other side-drive motors realized with a similar technique, the comb-structured rotor allows a multiplication of the working air gaps, thereby increasing the drive torque. The key element of this construction is the introduction of linkage arms used to attach the rotor comb teeth to the hub. These arms may also support an outer gear, allowing easy adjacent coupling to a driven mechanism. The design and fabrication of a 540 mu m diameter prototype are presented.<<ETX>>

A micromechanical detector for molecular beams

We demonstrate the detection of a molecular beam by means of a micromechanical momentum transfer detector operated in vibrational resonance. With a sensitive surface area of 0.5×0.3 mm2 the small paddle allows us to detect a beam with 6.5×107 He atoms hitting the surface per second. The detector response time equals the damping time of the paddle oscillation of about 1 s. The detector is sensitive enough to measure intensities in molecular beam scattering experiments. The novel detection scheme has the potential to allow the development of a position sensitive molecular beam detector.