Early airbags required the installation of several bulky accelerometers made of discrete components mounted in the front of the car, with separate electronics near the airbag (at a cost of over $50). Today, because of MEMS, the accelerometer and electronics are integrated on a single chip at a cost of under $10. The small size (about the dimensions of a sugar cube) provides a quicker response to rapid deceleration. And because of the very low cost, manufacturers are adding side impact airbags as well. The sensitivity of MEMS devices is also leading to improvements where size and weight of passengers will be calculated so the airbag response will be appropriate for each passenger.    MEMS devices are used to sense the presence of a passenger. MEMS sensors monitor tire, fuel, and oil pressures and send signals to the dashboard if levels fall below certain limits, making frequent car inspections a thing of the past. MEMS have also enabled advanced functions such as adaptive cruise control, collision-avoidance systems, and self-parallel parking capability—and a completely self-driving car may be in the not-too-distant future  

 Airbag deployment system:                                                                                                     One can find many MEMS applications in the automotive, biomedical, data storage, micro-optics, robotics and fluid control fields.    Figure 5: Schematic representation of the three-layer micro mechanical capacitive structure in an accelerometer system. But one of the most notable MEMS application is the accelerometer (a device used to measure acceleration) found in the airbag deployment system of many modern automobiles. These accelerometers are used as crash sensors in an airbag deployment system. A traditional airbag deployment system includes macro mechanical crash sensors which detect a crash pulse, a microprocessor which processes signals from the crash sensors, and an airbag deployment mechanism which physically deploys the airbag in an event of a collision. The traditional airbag deployment system uses a "ball-on-cone type" macro mechanical device as the crash sensor. When the deceleration of a vehicle exceeds a certain limit (signal of hard braking or collision), the decelerating forces would pull the ball to a position which signals the system to deploy the airbag . The inflated airbag will then act as a cushion between the occupants and the dashboard thus lessens the impact force imparted to the occupants by the crash. Airbags are designed to protect the occupants in automobile accidents against severe injuries. The airbag deployment system has been proven an effective supplemental restraint system (SRS) when used concurrently with safety seat belts. We will now discuss the advantages of using MEMS as crash sensors in the airbag deployment system rather than macro devices.  Advantages MEMS are used for crash sensing in newer airbag deployment systems because the traditional macro mechanical devices are not capable of meeting new standards set by the government and the auto industry. These new standards include the need of multi-directional crash sensing which cannot be achieved by the traditional crash sensors. In addition, traditional crash sensors are more expensive to make and less reliable compared to the MEMS crash sensors. Figure 6: Flowchart representation of the airbag deployment system analyzed by the microprocessor attached to the crash sensing unit. If the change is severe enough (meaning a real collision is in progress), the microprocessor will send a signal to deploy the airbag.  

Other applications of MEMS in AutoMobile Coutesy: http://www.solarfeeds.com/mems-everywhere/

MEMS chips used in Automobiles for Automatic Sensing purposes. Courtesy: http://www.sensorsmag.com/automotive/mems-sensors-are-driving-automotive-industry-1088