Government Polytechnic Mumbai

Instrumentation Department

Presented By : MOHIT SINGH RAJPUT

Micro Electronic Mechanical System

MEMS technology consist of micro electronic elements actuators, sensors and mechanical structures built onto a substrate which is usually “Silicon”. They are developed using microfabrication techniques : deposition, patterning, etching.

The most common forms of MEMS production are : Bulk micromachine, surface micromachine etc. The benefits of this small scale integrated device

brings the technology of nanometers to a vast no. of devices.

ABSTRACT

Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most general form can be defined as miniaturized mechanical and electro-mechanical elements that are made using the techniques of micro fabrication. The critical physical dimensions of MEMS devices can vary from well below one micron on the lower end of the dimensional spectrum, all the way to several millimeters. Likewise, the types of MEMS devices can vary from relatively simple structures having no moving elements, to extremely complex electromechanical systems with multiple moving elements under the control of integrated microelectronics. The one main criterion of MEMS is that there are at least some elements having some sort of mechanical functionality whether or not these elements can move. The term used to define MEMS varies in different parts of the world. In the United States they are predominantly called MEMS; while in some other parts of the world they are called “Microsystems Technology” or “micro machined devices”. microsensors and microactuator are appropriately categorized as “transducers”, which are defined as devices that convert energy from one form to another. In the case of microsensors, the device typically converts a measured mechanical signal into an electrical signal.

Micro-Electro-Mechanical System(MEMS)

What are MEMS ? Components of MEMS Fabrication of MEMS Applications of MEMS Benefits of MEMS

INTRODUCTION / OUTLINE

Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most general form can be defined as miniaturized mechanical and electro-mechanical elements that are made using the techniques of microfabrication.

The critical physical dimensions of MEMS devices can vary from well below one micron on the lower end of the dimensional spectrum, all the way to several millimeters. Likewise, the types of MEMS devices can vary from relatively simple structures having no moving elements, to extremely complex electromechanical systems with multiple moving elements under the control of integrated microelectronics.

The one main criterion of MEMS is that there are at least some elements having some sort of mechanical functionality whether or not these elements can move. The term used to define MEMS varies in different parts of the world.

What are MEMS ?

Micro Sensor

Micro Actuator

Micro Electronic

Micro Structure

MEMS

1. MicroElectronics The microelectronics of a MEMS are very

similar to chips as we think of them today. The microelectronics act as the "brain" of the system. It receives data, processes it, and makes decisions. The data received comes from the microsensors in the MEMS.

2. MicroSensors The microsensors act as the arms, eyes,

nose, etc. They constantly gather data from the surrounding environment and pass this information on to the microelectronics for processing. These sensors can monitor mechanical, thermal, biological, chemical, optical and magnetic readings from the surrounding environment.

3. MicroActuators A microactuator acts as a switch or a trigger to

activate an external device. As the microelectronics is processing the data received from the microsensors, it is making decisions on what to do based on this data. Sometimes the decision will involve activatin3g an external device. If this decision is reached, the micrelectronics will tell the microactuator to activate this device. 

4. MicroStructures Due to the increase in technology for

micromachining, extremely small structrures can be built onto the surface of a chip. These tiny structures are called micro structures and are actually built right into the silicon of the MEMS. Among other things, these microstructures can be used as valves to control the flow of a substance or as very small filters.

Deposition:• deposit thin film of material (mask) anywhere

between a few nm to 100 micrometers onto substrate• physical: material placed onto substrate,

techniques include sputtering and evaporation• chemical: stream of source gas reacts on substrate

to grow product, techniques include chemical vapor deposition and atomic layer deposition

• substrates: silicon, glass, quartz

• thin films:polysilicon, silicondioxide, silicon nitride, metals,

polymers

Fabrication of MEMS

There are three types of technologies for manufacturing "MEMS" which are as follows :

Bulk Micromachining Surface Micromachining High Aspect Ratio (HAR) Silicon

Micromachining

MEMS Manufacturing Technologies

Both bulk and surface silicon micromachining are used in the industrial production of sensors, ink-jet nozzles, and other devices. But in many cases the distinction between these two has diminished. A new etching technology, deep reactive-ion etching, has made it possible to combine good performance typical of bulk micromachining with comb structures and in-plane operation typical of surface micromachining . While it is common in surface micromachining to have structural layer thickness in the range of 2 µm, in HAR silicon micromachining the thickness can be from 10 to 100 µm. The materials commonly used in HAR silicon micromachining are thick polycrystalline silicon, known as epi-poly, and bonded silicon-on-insulator (SOI) wafers although processes for bulk silicon wafer also have been created (SCREAM). Bonding a second wafer by glass frit bonding, anodic bonding or alloy bonding is used to protect the MEMS structures. Integrated circuits are typically not combined with HAR silicon micromachining.

High Aspect Ratio (HAR) silicon micromachinig

MEMS technologies are widely used in almost every field such as physical , bio-medical and chemical fields.

Besides these "MEMS" are used in automobiles industry and are now becoming the face of Bio-medical engineering.

The following are discussed below :

Application Of MEMS

MEMS has changed the way of medical science by a rapid development in bio-medial industry . Some are mentioned below :

MEMS Pressure Sensor . MEMS Inertial Sensor . MEMS Machined Needles . MEMS Surgical Tools . Micro-fluids For Drug Delivery. Micro-fluid For Diagnostics .

Application Of MEMS In Bio-Medical Industry

Applications

Inertial Sensor

Surgical Tools

Micro Needles

Pressure Sensor

MEMS Inertial Sensors .

MEMS accelerometers are used in defibrillators and pacemakers. Some patients exhibit unusually fast or chaotic heart beats and thus are at a high risk of cardiac arrest or a heart attack. An implantable defibrillator restores a normal heart rhythm by providing electrical shocks to the heart during abnormal conditions. Some peoples’ hearts beat too slowly this may be related to the natural aging  condition . A pacemaker maintains a proper heart beat by transmitting electrical impulses to the heart. Conventional pacemakers were fixed rate. Modern pacemakers employ MEMS accelerometers and are capable of adjusting heart rate in accordance with the patient’s physical activity. Medtronic is a leading manufacturer of MEMS based defibrillators and pacemakers

Much smaller area Cheaper than alternatives

In medical market, that means disposable Can be integrated with electronics (system on one chip) Speed:

Lower thermal time constant Rapid response times(high frequency)

Power consumption: low actuation energy low heating power

Imperfect fabrication techniques Difficult to design on micro scales

Benefits of MEMS

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