An overview is given of research activities in the field of fluid components or systems built with microfabrication technologies. This review focuses on the fluidic behaviour of the various devices, such as valves, pumps and flow sensors as well as the possibilities and pitfalls related to the modelling of these devices using simple flow theory. Finally, a number of microfluidic systems are described and comments on future trends are given.

https://iopscience.iop.org/article/10.1088/0960-1317/3/4/002/pdf

Microfluidics-a review

'Artificial' actuator technologies under development include shape memory alloys, piezoelectric actuators, magnetostrictive actuators, contractile polymers and electrostatic actuators. The relevant properties of muscle are outlined and compared with a variety of artificial actuators. These and other actuators, such as regular and superconducting electromagnetic motors, internal combustion engines, hydraulic motors, pneumatic actuators, are reviewed and compared with muscle elsewhere (see Hunter, 1990; Hollerbach et al., 1991). >

A comparison of muscle with artificial actuators

This paper presents the design and performance of an electrostatic actuator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane. A theoretical description of the static behavior of the cantilever as it is pulled into contact with the rigid fixed-electrode structure is given. Two models are presented: a simplified semi-analytical model based on energy methods, and fully three-dimensional (3-D) coupled electromechanical numerical simulations using CoSolve-EM. The two models are in qualitative agreement with each other, and predict stable actuator behavior when the beam deflection becomes constrained by the curved electrode geometry before electrostatic pull-in can occur. The pull-in behavior depends on the shape of the curved electrode. Test devices have been fabricated by polysilicon surface micromachining techniques. Experimental results confirm the basic theoretical results. Stable behavior with relatively large displacements and forces can be generated by these curved electrode actuators. Depending on the design, or as a result of geometrical imperfections, regions of unstable (pull-in) deflection behavior are also observed.

/pdf/electrostatic-curved-electrode-actuators-509ltvu8xr.pdf

Electrostatic curved electrode actuators

A mesopump having a plurality of elementary cells and a method of pumping fluids using the mesopump. The cells each have a body forming a cavity having upper and lower electrodes with curved surfaces facing the other electrode. Electrical connections selectively energize the electrodes. A bistable diaphragm is mounted with its major portion located in the cavity between the electrodes so that the diaphragm deflects toward the upper or lower surfaces to conform thereto. A lateral conduit is located at at least one end of the body for fluid communication with the cavity. The lateral conduits are operably connected to a portion of the diaphragm mounted in the body and are opened and closed by movement of the diaphragm. A vertical conduit on at least one curved surface controls flow of fluid by movement of the diaphragm into and out of contact with the vertical conduit. The cells are interconnected to form the mesopump whereby activation of the electrodes causes movement of the diaphragm between the electrodes to move fluid into and out of the body. The preferred mesopump includes sets of three cell groups so that fluid enters a first cell from a source of fluid, is expelled to a second cell through a vertical conduit; expelled via a lateral conduit to a third cell, and expelled therefrom, whereby fluid passes from cell to cell upon activation of the electrodes.

Electrostatically actuated mesopump having a plurality of elementary cells

We present results of the design, fabrication, and testing of a microfabricated, membrane-type magnetic actuator. Magnetic pieces made of electroplated Permalloy (Ni80Fe20) are embedded in a thin flexible membrane made of silicone elastomer. When an external magnetic field is applied, a torque generated on the magnetic pieces produces membrane displacement. Permalloy pieces that are 100-mm-wide, 870mm-long, and 22-mm-thick are strategically positioned in a 2-mm-square, 40-mm-thick polydimethylsiloxane (PDMS) membrane (Sylgard 184). This design, produced through numerical simulations, is optimized to realize large membrane displacements. Tests performed on this membrane actuator showed displacements >80 mm in the presence of a 2:85 10 5 A/m external magnetic field. Larger displacements are possible with greater magnetization fields. This type of membrane actuator can be applied to the fabrication of tetherless micropumps for use in microfluidic systems. # 2001 Elsevier Science B.V. All rights reserved.

Micro magnetic silicone elastomer membrane actuator

The electrostatic actuator considered consists of a silicon membrane bonded to a glass plate by anodic bonding. On the glass plate a circular gold electrode is made and a thin oxide layer is grown on the silicon membrane before bonding. A pressure is applied to the cavity between the membrane and the glass plate causing the membrane to deflect away from the electrode. When a voltage is applied between the gold electrode and the membrane, high electrostatic forces acting along the membrane periphery will pull the membrane into contact with the glass plate. Experimental results are presented demonstrating a stroke length of 18 mu m working against a pressure of 2200 Pa using a voltage of 41 V. The actuator performance has in addition been investigated by means of mathematical analysis and numerical simulations, and a model relating the principal design parameters is presented. >

P. Gravesen

Papers

A new electrostatic actuator providing improved stroke length and force