All around us are hardware that assists with our everyday living and overall lives, from the mobile smart devices we are constantly interacting with to safety the air bag deployment systems in our cars. So what exactly are they?
The term MEMS stands for Micro-electromechanical systems, they are miniature machines that use both electrical and mechanical components, these are very small devices that range from a few millimeters across down to less than a micrometer, abbreviated “micron” – a human hair about 75 microns across.*
A micron is a millionth of a meter (1,000,000 meters)
These tiny devices fall into two main categories that use mainly either a mechanical or optical operation to convert energy or light signals into electronic data:
These use outside environmental factors for their operation to perform tasks such as hearing aids with their tiny diaphragms that provide feedback from audio sounds to convert in real time for the wearers use by sending the signals to an amplifier through the ear to a speaker. Airbags also have MEMS devices usually placed in impact zone areas of vehicles, when an impact is detected the force is measured via an accelerometer, if it is over a certain level, the sensor then sends a signal to the airbag which deploys – a modern vehicle will have several sensors for each possible contact face so as only to deploy the needed airbags protecting those inside the vehicle.
These operate using timed actions such as with insulin pumps and drug delivery systems for accurate dosages, inject printers that provide very high-quality output using thousands of tiny pressurized valves and pumps, there are safety systems such as those of gas and chemical detection and calibration that use tiny chambers to capture particles then deciding on their composition to provide accurate output for data analysis or even to a feedback device – perhaps to sound an alarm or vent a chamber of dangerous air for safety reasons.
The component parts of MEMS devices, whether they may be microactuators, microprocessors, microsensors and units for data processing are manufactured in the same way as that of integrated circuits (ICs), unlike the conventional mechatronic devices, they are normally manufactured in batches and many commercial MEMS devices are packed together with ICs for electrical or optical functions, the per device costs are low but packaging these microscopic components can be a challenge as due to their size, they have to be constructed in special clean rooms having to be kept free from air and water contamination and still have the ability to interact with the surrounding environment with motion too.
MEMS devices that use the electrical then optical signalling for feedback have been integrated into cinema projectors with the use of tiny mirrors that reacted very quickly and accurately to signal to then project onto the big screens. Deformable Micro Devices (DMD) have several hundred thousand microscopic mirrors each about 16 microns across, they are arranged in a rectangular array and attached on a hinged axis and can rotate ±10-12° either to an on or off state, with the ‘on’ state the mirrors reflect from the projector bulb into the lens and onto the screens pixel location appearing brightly, with the ‘off’ state, the mirrors are reflected elsewhere – normally onto a heatsink until the next optical instruction, as the MEMS mirror devices can react very quickly and without wearing out of breaking down, not only and they reliable but also very robust as well as accurate due to their tiny size.
With the technology advancements, the next micro devices are NEMS, they are of the nanometer scale and will have many more uses in time as they will be able to interact at a molecular and atomic level.
Each human interacts with from around 50 MEMS devices a day, it makes you think of the machines within machines and what the future holds for us all
Images used with permission from National Institute of Standards and Technology.