MEMS loud speaker

Miniaturized loud speakers for use in hearing aids, hearables and in-ear headphones.

more info

MEMS pump

Miniaturized pumps, valves and dosage systems for liquids and gases used in microfluidics.

MEMS actuation

Out-of-plane electrostatic bending actuators (NED).

Digital micro actuation

Binary coded electrostatic bending actuators.

Monolithically Integrated Actuator and Sensor Systems

Micromechanical systems as nanoscopic electrostatic drives

© Fraunhofer IPMS
MEMS based inchworm drive
© Fraunhofer IPMS

Micromechanical systems are the key to the miniaturization of components and devices without which no fast-growing technical sector can manage. Whether it is acoustic transducers for the audio sector, transducers for the ultrasonic sector, drives for microscopically small pumps or valves, micro mirrors and optics for beam guidance, as well as beam shaping of light of various wavelengths or miniaturized varactors for signal amplification and adaptation of electrical antenna networks.

The micromechanical systems make it possible to produce components that have a much smaller footprint than is currently known. At the same time, the requirements for the lowest possible energy consumption of such components have increased. In the future, these components will be integrated into web-enabled and ultra-mobile devices characterized by a long battery life. In this context, wireless interfaces and processors play a decisive role in determining the energy requirements of such systems. Since the amount of space available for energy supply in such devices is very limited, all components have to make do with a very small energy budget.

This also means that actuating principles are required for micro- and nanomechanical systems that require minimal space and energy. The business unit "Monolithically Integrated Actuator and Sensor Systems" (MAS) develops electrostatic bending actuators for this purpose, which operate according to the bimorph principle. The Nanoscopic Electrosatic Drives, NED for short, are implemented in MEMS technologies and are suitable for a wide range of applications.

How nanoscopic electrostatic drives (NED) works

NED is a novel MEMS actuator principle. A beam-shaped actuator consists of at least two spaced electrodes, which are electrically separated from each other by gaps as thin as a few 10 nm. By applying a control voltage, an electrostatic field is generated between these electrodes, resulting in large attraction forces between the electrodes. These forces are transformed into lateral forces by appropriate geometries and topographies of the beam-shaped electrodes. From a technological point of view, there are two basic types of NED actuators. Vertical NED (V-NED) actuators operate out of the chip plane and lateral NED (L-NED) actuators move within the chip plane. A unique feature of these actuators is that their displacement is significantly greater than the electrode gap. This makes it possible to achieve large deflections with low control voltages and thus an extremely low energy requirement.

Advantages of nanoscopic electrostatic drives (NED)

  • Low energy consumption → Low capacitance, small reactive currents and low control voltages allow the use of energy-efficient driver circuits and thus lead to low power consumption of the overall system
  • CMOS compatibility → Integration of the actuators with CMOS circuits and
  • RoHS compatibility → the NED bending actuators are an alternative to ceramics such as PZT, which are currently excluded from the RoHS directive
  • High number of degrees of freedom →
  • [1] Instead of a beam shape, the NED actuator can be designed as a rotationally symmetrical plate. This results in an actuator plate that bends spherically.
  • [2] The actuators can be deflected in a positive or negative direction by means of suitable electrode topographies or geometries. A combination of topographies or geometries or an arrangement of the actuator cells on both surfaces of the bending actuator allows movements in both directions (bidirectional).
  • [3] A tilting motion can be generated by two mechanically coupled NED actuators. If several NED actuator pairs are suitably connected, linear movements are possible.
  • [4] The NED actuators can be cascaded to further increase the deflection (Rainbow configuration) or force (Parallel configuration).