We demonstrate the use of electrostatically driven micro-electromechanical systems (MEMS) devices to control and deliver synchrotron x-ray pulses at high repetition rates. Torsional MEMS micromirrors, rotating at duty cycles of 2 kHz and higher, were used to modulate grazing-incidence x rays, producing x-ray bunches shorter than 10 μs. We find that dynamic deformation of the oscillating micromirror is a limiting factor in the duration of the x-ray pulses produced, and we describe plans for reaching higher operating frequencies using mirrors designed for minimal deformation.
Several applications of optical micromirrors need synchronization of its mechanical oscillation with an external control
signal. Self-sustained oscillation of micromirrors is a prerequisite for achieving such synchronization. To suppress its
mechanical deformation these micromirrors are operated under atmospheric or controlled pressure environment.
Operation under this environment leads to increase in driving voltages to achieve required deflections. However,
significant parasitic crosstalk due to these high driving voltages presents a challenge for achieving their self-sustained
oscillations. In this paper, stable self-sustained oscillation of a 13.5kHz micromirror is achieved at atmospheric pressure
by actively suppressing its crosstalk. Frequency stability of 7.2ppm is obtained for this micromirror's self-sustained
oscillation at atmospheric pressure.
Micro-positioning stages fabricated using Micro Electro Mechanical Systems (MEMS) based processes have been
critical in enabling micro/nano manipulation and probing. These stages have been extensively used in micro-force
sensors, scanning probe microscopy and micro optical lens scanners. This paper presents the design, kinematic and
dynamic analysis, fabrication and characterization of a novel monolithic micro-positioning XY stage. The design of the
proposed micro-positioning stage is based on a Parallel Kinematic Mechanism (PKM). The PKM based design
decouples the motion in the XY direction. Additionally, it restricts the parasitic rotation of the end-effector (table) of the
micro-positioning stage while providing an increased motion range. The motion of the stage is linear in the operating
range thus simplifying its kinematics. The truss like parallel kinematic mechanism design of the stage structure reduces
its mass while keeping the stage stiffness high. This leads to a high natural frequency of the micro-positioning stage
(1250Hz) and a high Q-factor of 156. The stage mechanism is fabricated on a Silicon-On-Insulator (SOI) substrate and is
actuated by integrated electrostatic rotary comb drives. The fabrication process uses multi-layer patterning along with an
Inductively Coupled Plasma Deep Reactive Ion Etching (ICP-DRIE). The use of ICP-DRIE enables the high aspect ratio
etching that is required for the stage fabrication and its optimal actuation using the integrated electrostatic rotary comb
drives. The fabricated stages have a motion range of more than 30 microns of decoupled displacements along the X and
Y directions at a driving voltage of 200V.
We developed a novel piezo-driven parallel-kinematics single crystal silicon micropositioning XY stage. This monolithic design features parallelogram four-bar linkages, flexure hinges and piezoelectric stack actuators. The stage is made from single crystal silicon because it has excellent mechanical properties compared to metals, which result in high bandwidth, large work zone and compact size of the stage. Kinematics and dynamics analysis were performed for the design. We also developed microfabrication procedures to make the prototype of the stage. Experiment results show that the mechanical structure of the stage can deliver a 400μm by 400μm square work zone without failing any flexure hinges. With two piezoelectric stack actuators mounted, the stage is able to do open-loop contouring in a 32μm by 32μm work zone with 160V driving voltages applied. The resonation frequencies of the stage are between 1,300 and 1,400Hz.