Design and Fabrication of a Planar Three-DOFs MEMS-Based Manipulator

Abstract

Abstract-This paper presents the design, modeling, and fabrication of a planar three-degrees-of-freedom parallel kinematic manipulator, fabricated with a simple two-mask process in conventional highly doped single-crystalline silicon (SCS) wafers 100 . The manipulator's purpose is to provide accurate and stable positioning of a small sample (10 × 20 × 0.2 μm 3 ), e.g., within a transmission electron microscope. The manipulator design is based on the principles of exact constraint design, resulting in a high actuation-compliance combined with a relatively high suspension stiffness. A modal analysis shows that the fourth vibration mode frequency is at least a factor 11 higher than the first three actuation-related mode frequencies. The comb-drive actuators are modeled in combination with the shuttle suspensions gaining insight into the side and rotational pull-in stability conditions. The two-mask fabrication process enables high-aspect-ratio structures, combined with electrical trench insulation. Trench insulation allows structures in conventional wafers to be mechanically connected while being electrically insulated from each other. Device characterization shows high linearity of displacement wrt voltage squared over ±10 μm stroke in the x-and y-directions and ±2• rotation at a maximum of 50 V driving voltage. Out-of-plane displacement crosstalk due to in-plane actuation in resonance is measured to be less than 20 pm. The hysteresis in SCS, measured using white light interferometry, is shown to be extremely small.[ 2009-0254]Index Terms-Compliant mechanism, electrostatic actuators, exact constraint design, multidegrees of freedom, nanometer positioning, precision engineering, trench isolation.

Exact Constraint Design of a Two-Degree of Freedom Flexure-Based Mechanism1

“…The size of the complete mechanism is 540 Â 585 Â 87 mm and the workspace-area to footprint ratio is 1 32 . This is large compared to [13,[31][32][33][34][35]. The cross-flexure hinges were tuned and oriented to maximize the lowest unwanted natural frequency.…”

Development of a shape-memory-alloy micromanipulator based on integrated bimorph microactuators

“…Recently, the use of microelectromechanical system (MEMS) technology has enabled the manufacturing of a wide range of miniaturized micromanipulators using microfabrication techniques. These MEMSbased micromanipulators utilize several actuation mechanisms, including electrostatic [4] , electromagnetic [5] , and piezoelectric actuators [6] . Despite having small device structures, high accuracy and fast response times, these micromanipulators often suffer from a limited displacement range, a low actuation force, and difficulties related to the fabrication process [7] .…”

A large-stroke planar MEMS-based stage with integrated feedback

“…For example De Jong et al [28] and Mukhopadhyay et al [91] show very similar 3DOF stages for in-plane motion. A six-axis compliant mechanism is presented by Chen and Culpepper [17], which consists of three pairs of two-axis thermomechanical actuators.…”

“…For example De Jong et al [28] and Mukhopadhyay et al [91] show very similar parallel kinematic 3DOF stages with a stroke of 20 ñm and 27 ñm and a rotation of 70 mrad and 30 mrad, respectively. A six-axis compliant mechanism is presented by Chen and Culpepper [17].…”

“…Large manipulators, as shown in [25] and [94], can be avoided by using a MEMS-based stage. A MEMS-based sample manipulator is shown in [28], but this stage does not include feedback and is not characterized in vacuum.…”