It is the future technology,introduction, Basic elements,structure,leverages,shortcomings,applications

1. MEMS – Micro Electro Mechanical Systems
by
Mrs.R.Chitra,
Assistant Professor(SS),
Department of ECE,
School of Engineering,
Avinashilingam Institute, Coimbatore.

2.  MEMS refers to technology that allows mechanical structures to be miniaturized and integrated with
electrical circuitry, resulting in a single physical device that is like a system, where “system” indicates that
mechanical components and electrical components are working together to implement the desired
functionality. Thus, it’s a micro (i.e., very small) electrical and mechanical system.
 It is the future technology that allows microscopic devices to replicate the functionality of current large-
scale systems, or even perform tasks previously unimaginable.
 MEMS is a process technology used to create tiny integrated devices or systems that combine mechanical
and electrical components.
 They are fabricated using integrated circuit (IC) batch processing techniques and can range in size from a
few micrometers to millimeters.
 These devices (or systems) have the ability to sense, control and actuate on the micro scale, and generate
effects on the macro scale.

3.  MEMS are made up of components between 1 and 100 micrometers in size (i.e., 0.001 to 0.1 mm).
 MEMS devices generally range in size from 20 micrometres to a millimetre (i.e., 0.02 to 1.0 mm).
 They usually consist of a central unit i.e. an integrated circuit chip such as microprocessor that
processes data and several components that interact with the surroundings such as micro sensors.
 MEMS have large surface area to volume ratio, forces produced by ambient electromagnetism (e.g.,
electrostatic charges and magnetic moments), and fluid dynamics (e.g., surface tension and
viscosity) are more important design considerations than with larger scale mechanical devices.
 MEMS technology is distinguished from molecular nanotechnology or molecular electronics in that
the latter must also consider surface chemistry.

4.  Let us try to understand the working of the MEMS with an example – Gyroscope
 GYROSCOPE:
 Gyroscopes, or gyros, are devices that measure or maintain rotational motion.
 MEMS (microelectromechanical system) gyros are small, inexpensive sensors that
measure angular velocity.
 The gyroscope sensor within the MEMS is tiny (between 1 to 100 micrometers, the
size of a human hair).
 When the gyro is rotated, a small resonating mass is shifted as the angular velocity
changes.
 This movement is converted into very low-current electrical signals that can be
amplified and read by a host microcontroller.

7.  The mechanical design of even simple systems, first requires an understanding of the
mechanical behavior of the various elements used.
 While the basic rules of mechanical dynamics are still followed in the miniaturized world,
many of the materials used in these structures are not well mechanically characterized.
For example, most MEMS systems use polysilicon to build mechanical structures.
 Most MEMS sensors mechanical systems are designed to realize a variable capacitor.
 Electronics are used to convert the variable capacitance to a variable voltage or current,
amplify, linearize, and in some cases, temperature compensate the signal. This is a
challenging task as the signals involved are very minute.

8.  Very small size, mass, volume
 Very low power consumption
 Low cost
 Easy to integrate into systems or modify
 Small thermal constant
 Can be highly resistant to vibration, shock and radiation
 Batch fabricated in large arrays
 Improved thermal expansion tolerance
 Parallelism

9.  The overall silicon area is generally larger.
 Multi chip modules require additional assembly steps.
 Yield is generally lower for multi chip modules.
 Larger signals from the sensor are required to overcome the stray capacitance of the
chip to chip interconnections, and stray fields necessitating a larger sensor structure.
 Larger packages are generally required to house the two-chip structure.

10.  Airbag Systems
 Headlight Leveling
 Rollover Detection
 Active Suspension
 Earthquake Detection and Gas Shutoff
 Accelerometers in consumer electronics devices such as game controllers, cell phones and a
number of Digital Cameras.
 In PCs to park the hard disk head when free-fall is detected, to prevent damage and data loss.
 Silicon pressure sensors e.g. car tire pressure sensors, and disposable blood pressure sensors.
 Optical switching technology, which is, used for switching technology and alignment for data
communications.
 Interferometric modulator display (IMOD) applications in consumer electronics (primarily displays
for mobile devices).