MEMS

Tiny machines can move.

They have parts that work like tiny motors. These machines are very small. They are smaller than a speck of dust.

These machines use electricity and moving parts. They can sense things around them. People make them using silicon. Silicon is a material used for computer chips. Some machines are made of metal or plastic. They can be used to test blood. These little tools help our world work.

MEMS are tiny machines. The name stands for micro-electromechanical systems. These devices have two main parts. They have electronic parts that handle data. They also have moving parts. These moving parts help them sense the world.

Most MEMS are very small. Some parts are only 1 micrometer wide. A micrometer is much smaller than a millimeter. These machines use many different materials. Most are made of silicon. Silicon is a material used for computer chips. It is very reliable. It can move billions of times without breaking.

Some MEMS use polymers. Polymers are materials like plastic. These are good for testing blood. Other machines use metals like gold or silver. Scientists use special ways to make them. One way is called lithography. This is a way to draw patterns onto a surface using light.

These tiny tools are very useful. They can be used in many new ways. They help us study small things in science.

MEMS are tiny machines that combine two different worlds. The name stands for micro-electromechanical systems. These devices have electronic parts and moving parts working together. One part is a central unit, like a tiny computer chip, that processes data. Other parts are microsensors that interact with the world around them.

Because these machines are so small, they feel forces differently than big machines. Things like surface tension and magnetism become very important for their design.

Making these machines requires a very careful, step-by-step process. First, scientists use deposition to add thin layers of material onto a surface. They can use physical deposition, like sputtering, or chemical deposition, like vapor deposition. Next, they use a method called patterning to create specific shapes. One common way is photolithography, which uses light to draw patterns onto a sensitive material. This allows them to build structures that are incredibly small.

People have thought about tiny machines for a long time. In 1959, Richard Feynman gave a famous lecture about the room available at the bottom of things. However, MEMS only became practical when we could make them using semiconductor technology. An early example was a device called a resonant-gate transistor. This was made by Robert A. Wickstrom for Harvey C. Nathanson in 1965. Later, a person named Raymond J. Wilfinger patented a device called a resonistor.

Many different materials are used to build these microscopic wonders. Silicon is the most common choice for making these devices. It is a great material because it is very reliable and cheap. Silicon can flex billions or even trillions of times without breaking.

Other scientists use polymers, which are like plastics, for tasks like blood testing. Metals such as gold, silver, and aluminum are also used for certain parts. Even ceramics are used because they have very useful properties for sensors.

You can find MEMS technology working in many things you might know. For example, digital micromirror devices use arrays of these tiny components. These arrays can be quite large, even more than 1000 square millimeters.

These machines are also getting even smaller. When they merge into the nanoscale, they are called nanoelectromechanical systems, or NEMS. This shows how science keeps finding new ways to build smaller and better tools.

Micro-electromechanical systems, or MEMS, are microscopic devices that combine electronic and moving parts. These systems function by integrating a central processing unit, such as an integrated circuit chip, with several components that interact with the surroundings. These interacting components are often microsensors. While a single MEMS device might range from 20 micrometres to 1 millimetre in size, they can be arranged in large arrays. For example, digital micromirror devices can cover areas larger than 1000 mm2.

Designing MEMS requires a different approach than designing large-scale mechanical machines. Because MEMS components are so small, they have a very large surface area relative to their volume. This means that forces like surface tension, viscosity, and ambient electromagnetism become critical design factors. Forces such as electrostatic charges and magnetic moments have a much greater impact at this scale. MEMS technology is distinct from molecular nanotechnology because it does not necessarily focus on surface chemistry.

Engineers build these devices using modified semiconductor fabrication technologies. The process begins with deposition, which adds thin films of material ranging from 1 to 100 micrometres thick. Physical vapor deposition (PVD) includes techniques like sputtering, where an ion beam liberates atoms from a target. Another method is evaporation, which uses heat or an electron beam in a vacuum. Chemical deposition, or CVD, involves a gas reacting on a substrate to grow material. After deposition, patterning transfers a specific design into the material.

Patterning often relies on lithography, which uses radiation to change a photosensitive material. In photolithography, light is used to create a mask on a substrate. For even smaller structures, scientists use electron beam lithography. This method scans a beam of electrons across a surface to create features in the nanometer range. While electron beam lithography can beat the diffraction limit of light, it is much slower than other methods. This slow speed can make the process vulnerable to beam drift or instability.

Many different materials are used to construct MEMS, with silicon being the most common. Silicon is used for most modern integrated circuits because it is inexpensive and high-quality. In its single crystal form, silicon is a Hookean material, meaning it shows almost no energy loss when flexed. This makes silicon incredibly reliable, allowing it to survive billions or even trillions of cycles without fatigue. Scientists also use silicon nanowires for advanced applications like nanowire batteries.

Other materials offer unique advantages for specific tasks. Polymers are excellent for microfluidic applications, such as disposable blood testing cartridges, because they can be produced in huge volumes. Metals like gold, aluminum, and titanium are also used through processes like electroplating or sputtering. Ceramics, such as silicon carbide or aluminum nitride, are used for their specialized properties. For instance, aluminum nitride shows piezoelectric properties, which allows it to act as a sensor for force. Titanium nitride is used because it is highly conductive and resists biocorrosion in biological environments.

There are two primary types of MEMS switch technology: capacitive and ohmic. A capacitive switch uses a moving plate or sensing element to change the capacitance of the system. An ohmic switch is controlled by cantilevers that are managed electrostatically. However, ohmic switches face certain risks, such as contact wear or metal fatigue. This happens because the cantilevers can deform over time.

The history of MEMS shows a long interest in miniature machines. In 1959, Richard Feynman gave a famous lecture titled "There's Plenty of Room at the Bottom." Early mechanical examples include the resonant-gate transistor, developed by Robert A. Wickstrom in 1965. Later, Raymond J. Wilfinger patented the resonistor between 1966 and 1971. The actual term "MEMS" was introduced in 1986 by S.C. Jacobsen and J.E. Wood in a proposal to DARPA. As these systems continue to shrink toward the nanoscale, they are referred to as nanoelectromechanical systems, or NEMS.