5 - MEMS devices

Electrostatic linear transfer lines, arrays and conveyors consist of several MEMS actuator elements. Each element can generate motion in one specific direction, if it is activated by electrostatic field. Working in synchronic mode the actuator elements can move material particles.

In a standard comb drive, the capacitance between the fingers varies linearly with the displacement, resulting in an electrostatic driving force, which is independent of the position of the moving fingers (relative to the fixed ones). The animation shows the top view of a surface micromachined, electrostatic comb-drive device.

A voltage difference creates an electrostatic force that closes the valve. In "no charge"-state, the valve is opened. The maximum operating pressure can be varied by the applied charge conditions.

Electrostatic

ElectroHidroDynamic (EHD)

The operation of the electro-hydrodynamic pump (EHD) is based on the electrostatic force acting on ionized particles inside an electric field generated between two electrodes. The ions are accelerated and their scattering on neutral molecules accelerates the latter ones as well thus, the overall fluid starts to move. Polar molecules can also be accelerated by non-homogenous electrostatic fields.

In many micro chemical analysis or synthesis systems flow control is a crucial issue. Because of the sometimes extremely narrow channels that are included in such systems, conventional flow control by hydraulic pumping cannot always be applied because excessively high pressures are required to achieve a significant liquid flow rate. In narrow channels electro-osmotic flow pumping principles are very advantageous, and can be used to create extremely high pressures. Combined the electro-osmotic flow principles with local field effects liquid flow control similar to current control in electronic field effect transistors can be achieved.

Micro grippes are made as standard comb drive device, having a couple of elonged offshoots for gripping and holding micrometer sized particles, such as living cells, etc. The animation shows the top view of a surface micromachined, electrostatic micro gripper.

Both the stator and rotor parts of the micro-motors are fabricated by MEMS technology. The rotor turns due to electrostatic field generated by the alternating voltage difference between the electrodes.

The micro-positioning system is a part of HDD read-write heads. It consist of two arc-shaped electrostatic comb drive. The segmented stator controls the rotation of rotor part, which has a nozzle end holding the micromachined electomagnetic read-write head.