Micro electro mechanical systems are miniature devices that are integrated in mechanical and electrical elements. These devices are used in diverse applications ranging from sensor systems to optical networks. They are attractive and suitable for many applications because they are small in size, weight and allow the systems to
MEMS are manufactured using a variety of fabrication methods. The methods are classified as: molding, bulk micromachining, and surface micromachining.
This is the oldest of micromachining technologies. It removes materials from the substrate and creates holes channels, cavities and other shapes. Anisotropic wet etching of glass, silicon and Isotropic have been used in bulk micromachining. Deep reactive is the other technique that is commonly used in bulk micromachining.
This is another common technology employed in manufacturing MEMS. It entails depositing films of substrates using photolithography so as to create a micromechanical devices. The film will alternate between sacrificial and structural layers. The parts of MEMS are made from structural layers while the sacrificial layers serve to support the components during fabrication. In this method, the sacrificial material is removed using wet chemical etching. This results in freestanding MEMS parts that can easily move relative to the fixed substrate.
MEMS parts are made by creating a mold. The mold is then filled to create the desired part. Polymers are used to make the molds. Materials such as deep-etched silicon wafers, metal parts and photoresist may be used to make molds. The molds are then filled with electroplating and the polymer created by pressing and pouring precursor into the mold. The molded part is then removed from the mold by etching it away. However in a case where the mold is to be used again, peeling the mold would suffice.
Advantages and Challenges of MEMS
MEMS are attractive and are used in many applications because of their size. Typically, MEMS could be 1 micrometer or less. The small size is what allows them to be deployed in a wide range of applications. They are used in micromechanical switches since they allow for signal switching and phase shifting.
Also, MEMS allow for on-chip integration of electromechanical systems. The circuitry used to control them allow for further miniaturization. Also MEMS fabrication techniques make it easier to fabricate thousands of systems by leveraging the integrated circuit ideas. It makes them reliable and reduces costs.
Just like any other technology, MEMS have their own challenges. Firstly, because they are small in size, they operate below what the typical mechanical devices can do. Also, they could be affected by friction and adhesion forces, which occasionally may lead to the failure of the devices. Consequently, the devices must be well fabricated and tested to reduce the effect. MEMS are small and so it is difficult to mechanically interact with other components. Also, packaging of MEMS components is a challenge since each device needs to be packaged in a way that keeps the components clean and free from contamination. Unfortunately, this allows for mechanical motion that causes interaction with the environment. This necessitate that MEMS pressure sensor should be packaged after considering the ambient pressure and its electronic circuitry should be protected from dust and particles.
Lastly, development of MEMS could be costly because it only produces few units at a time because of complex and expensive fabrication equipment that are used in the manufacturing process.
All said, it is vital to mention that MEMS components are critical and future mechanical and electrical innovations will largely depend on how they are used.