My IDEA and DESIGN about Micromirror

Micro-Electro-Mechanical Systems, or MEMS, are integrated micro devices or systems combining electrical and mechanical components. They are fabricated using integrated circuit (IC) batch processing techniques and can range in size from micrometers to millimeters. These systems can sense, control and actuate on the micro scale, and function individually or in arrays to generate effects on the macro scale. This design presents an overview of MEMS technology with emphasis on optical applications. Applications of MEMS devices vary in many fields from automotive transducers, biomedical technologies, communication systems, robotics, aerospace, micro-optics, industrial sensors and actuators.
The applications of MEMS in optics include display systems, optical switching, optical communication, optical data storage, optical processing and interconnection, and adaptive optics.

This design focuses on the state-of-the-art of technologies for the design, fabrication and applications of MEMS micro-mirrors. I will discuss the major design issues, considerations, calculations and restrictions of micro mirrors. The materials employed for the reflective surfaces are described along with their properties. The materials used for the static and dynamic MEMS micro structures as well as the different configurations are also presented and summarized. The two most widely used techniques for actuation, namely, Electrostatic and Magnetic are presented along with the formulas, tables and curves used to design the movable structures. The different options of fabrication processes are presented and discussed. Finally, the applications of micro mirrors are described.

Micro mirrors are the centerpieces of MEMS optical switches. They are tiny mirrors fabricated in silicon using MEMS technology. The switching function is performed by changing the position of a micro mirror to deflect an incoming light beam into the appropriate outgoing optical fiber. The three important properties of micro mirrors are reflectivity, light transmission, and surface roughness. Coating its surface with metal can increase the reflectivity of a micro mirror.

MIRRORS are an important component in an optical system. Mirrors are found in almost every system that makes use of light sources and lenses. Their ability to reflect light and change its direction of propagation has been used for several centuries. Mirrors in the macroscopic world are very well understood and present no major challenges in their design and calculation. However, when the size of the mirror is in the order of a few microns, several issues and challenges come into place. The advances of MEMS technology in the last decade have made possible to design and fabricate micro mirrors that are actually used in real industrial and commercial applications. MEMS micro-mirrors are used today in fiber optic communications as switching devices, in digital displays and projectors, in laser scanners, printers and barcode readers, and in bioengineering for laser surgery.

The area in which MEMS has seen one of its biggest commercial breakthroughs lately is micro machined mirrors for optical switching in both fiber optic communications and data storage applications. Optical switches are to optical communications what transistors are to electronic signaling. What makes Si single-crystal attractive in this case is the optical quality of the Si surface. The quality of the mirror surface is primordial to obtain very low insertion loss even after multiple reflections. Wet bulk micromachining has an advantage here over deep reactive ion etching (DRIE),as the latter leaves lossier Si mirror surfaces due to the inevitable ripples.

MEMS optical switch. The optical signals passing through the optical fibers at the input port are switched independently by the gimbal–mounted MEMS mirrors with two-axis tilt control and then focused onto the optical fibers at the output ports. In the switch, any connection between input and output fibers can be accomplished by controlling the tilt angle of each mirror. As a result, the switch can handle several channels of optical signals directly without costly optical-electrical or electrical-optical conversion.

The MEMS micro-mirrors can be used in the making of optical sensors and display both of which involves the controlling and directing of the light band. Today, information is being transferred to people from electronic devices through display technologies like the Cathode Ray Tubes (CRTs) and Liquid Crystal Display (LCD). In the future, MEMS-based Micro-Mirror array is a likely candidate to replace them as the dominant form of display technologies. This is due to the low-cost and high performance of the micro-mirrors. Furthermore, due to the similar processes and facilities used in the fabrication of the MEMS micro-mirrors, it is relatively easy to incorporate them with their controlling IC chip onto a single silicon substrate.

I have used the angle of the rigid mirror in order to control the location of a reflected beam
of light. This allows the mirror to act as an optical switch for optical fiber networks. The mirror is made of a material with sufficient stiffness to prevent bending. The mirror is attached to a thin beam that is anchored in place at the opposite end. The beam is free to twist and acts as a torsion spring. the mirror is attached to two beams, one on each side rather than a single beam. Thermo pneumatic, thermo elastic, electrostatic, magnetic, or piezoelectric forces may be used to make the mirror move. Here the use of electrostatic force is imagined.A pair of electrodes reside below the mirror. When a potential difference is applied between either of the electrodes and the mirror, a torque is exerted causing the desired rotation.

When electrostatic forces are used to actuate the system, the range of operation is limited by the pull-in instability. The device is actuated by applying a potential difference between the mirror and one of the ground electrodes. This causes a torque on the system, which is countered by the effect of a torsion spring. For this system, the pull-in instability occurs once rotation through a critical angle has taken place. That is, the range of angular motion is limited by the pull-in instability.

Micro-mirror arrays are currently being developed by a number of companies for optical switching. To bring these products to the market quickly, a rapid development cycle is needed, leaving little time for multiple fabrication runs. CAD tools for MEMS can reduce the number of fabrication iterations run by allowing prototyping to occur within the virtual environment. Here, many models can be tested quickly and the design can be optimized prior to initial fabrication.

Modeling of micro-mirrors requires unique simulation capabilities beyond those required for traditional MEMS devices. In many cases, the device alone has unique features which require that CAD tools offer additional capabilities beyond typical electro-mechanical analysis. Second, the entire array must be studied, both from a fabrication and optical perspective. The output of a MEMS software CAD tool is input into an optical ray-tracing program to provide optical system performance of the total MEMS micro-mirror and provide non-sequential ray-tracing of a micro-mirror array.

Nanotechnology Investements and Insurance

As a matter of fact that this is one of the emerging field, it requires a lot of investment and the investors are subjected to risk that their investments may fail to give some fruitful output. so there is a term known as nanotechnology investment and nanotechnology insurance. Investment is another thing and insurance is another thing. the main point is that the fund managers must keep in mind that the investors and not under any critical situation when there is a lot of chance that their investment may bankrupt then. so some of the investors are also insuring there fund as it will surely secure then up to some point, so that there losses if they happen may not prove to be critical to them. so insurance of this field is quite important and hence nanotechnology investment is as important as nanotechnology insurance.

MEMS and Nanotechnology Applications

There are numerous possible applications for MEMS and Nanotechnology. As a breakthrough technology, allowing unparalleled synergy between previously unrelated fields such as biology and microelectronics, many new MEMS and Nanotechnology applications will emerge, expanding beyond that which is currently identified or known. Here are a few applications of current interest:

Biotechnology

MEMS and Nanotechnology is enabling new discoveries in science and engineering such as the Polymerase Chain Reaction (PCR) microsystems for DNA amplification and identification, micromachined Scanning Tunneling Microscopes (STMs), biochips for detection of hazardous chemical and biological agents, and microsystems for high-throughput drug screening and selection.

Communications

High frequency circuits will benefit considerably from the advent of the RF-MEMS technology. Electrical components such as inductors and tunable capacitors can be improved significantly compared to their integrated counterparts if they are made using MEMS and Nanotechnology. With the integration of such components, the performance of communication circuits will improve, while the total circuit area, power consumption and cost will be reduced. In addition, the mechanical switch, as developed by several research groups, is a key component with huge potential in various microwave circuits. The demonstrated samples of mechanical switches have quality factors much higher than anything previously available.

Reliability and packaging of RF-MEMS components seem to be the two critical issues that need to be solved before they receive wider acceptance by the market.

Accelerometers

MEMS accelerometers are quickly replacing conventional accelerometers for crash air-bag deployment systems in automobiles. The conventional approach uses several bulky accelerometers made of discrete components mounted in the front of the car with separate electronics near the air-bag; this approach costs over $50 per automobile. MEMS and Nanotechnology has made it possible to integrate the accelerometer and electronics onto a single silicon chip at a cost between $5 to $10. These MEMS accelerometers are much smaller, more functional, lighter, more reliable, and are produced for a fraction of the cost of the conventional macroscale accelerometer elements.

Applications of nanotechnology-Energy

Energy

The majority of the world’s energy comes from fossil fuels – primarily coal, oil, and natural gas. All three were formed on Earth about 360 million years ago during the Carboniferous Period and long before the age of the dinosaurs.

We rely on fossil fuels for much more than gasoline to power our cars. For example, tremendous amounts of oil are required to produce all plastics, all computers and high tech devices. According to the American Chemical Society, it takes 3.5 pounds of fossil fuels to make a single 32 megabyte DRAM computer chip, and the construction of a single desktop computer consumes ten times its weight in fossil fuels. Our food is produced by high-tech, oil-powered industrial methods of agriculture, and in the US each piece of food travels about 1,500 miles before it reaches the grocery store. Pesticides are made from oil, and commercial fertilizers are made from ammonia, which is made from natural gas. Fossil fuels are needed to make many medical devices and supplies such as life-support systems, anesthesia bags, catheters, dishes, drains, gloves, heart valves, needles, syringes, and tubes.

There is a limited supply of fossil fuels and they are nonrenewable. Today, we are using fossil fuels faster than we are finding them. In fact, the Oil Depletion Analysis Center (ODAC) predicts that in the near future the demand for fossil fuels will far exceed the Earth’s supply.

Researchers are exploring ways in which nanotechnology could help us accomplish the following two goals:

(1) Access and use fossil fuels much more efficiently so that we can get more energy out of current reserves.

(2) Develop new ways to generate energy.

One example of processes being developed to use fossil fuels more efficiently is the current research to design zeolite catalysts at the nanoscale.

A natural zeolite collected in 2001.

A zeolite is an inorganic porous material which works as a kind of sieve - allowing some molecules to pass through while excluding or breaking down others. Zeolites can be either natural or synthetic, and new zeolites are still being discovered and invented. In 1960, Charles Plank and Edward Rosinski developed a process to use zeolites to speed up chemical reactions. Plank and Rosinski’s process used zeolites to break down petroleum into gasoline more quickly and efficiently. Today, researchers are working to design zeolite catalysts at the nanoscale. By adjusting the size of the zeolite pores on the nanoscale, they can control the size and shape of molecules that can enter. In the case of gasoline production, this technique could mean that we would get more and cleaner gasoline from every barrel of oil.

New Energy Producers

Solar Power

Researchers around the world are working on the development of new energy sources. What are the alternatives and what role could nanotechnology play? We already generate energy through hydropower (i.e., water). Damns have been built on most of the major waterways. Energy generated by wind turbines could help to lessen some of our dependence on fossil fuels. Although wind turbines are in use today, their energy output is far less than what is needed. Harnessing the sun’s rays to make solar power is another alternative, but with current technology, solar panels could only make a limited impact.

Of these three methods, solar energy holds the most promise. Right now you need silicon wafers to make solar panels, and silicon wafers, like computer chips, require a large amount of fossil fuels for production. However, researchers like Paul Alivisatos at the University of California, Berkeley hope to use nanotechnology to develop nano solar cells that would be energy-intensive and far less expensive to make. Researchers at the University of Toronto are using nanotechnology to develop solar panels capable of harnessing not only the visible light from the sun, but the infrared spectrum as well, thus doubling the energy output. What’s more, these new solar cells could be sprayed on surfaces like paint, making them highly portable. Researchers at Rice University want to take solar energy research even further. They hope to someday build a solar power station in space capable of catching the solar energy that bypasses the Earth every day and providing about nine times the efficiency of solar cells on Earth.

In these and other energy-producing advances, nanotechnology will play a critical role.

New Energy Producers II

Fuel Cells

Another area where nanotechnology is expected to play a major role is in the development of new fuel cells.

The first fuel cell (or "gas battery") was invented by William Robert Grove in 1839, only 39 years after Alessandro Volta invented the battery (the voltaic cell). Unfortunately, the materials that Grove used to make his fuel cell were unstable and the technology was unusable. One hundred and twenty years later, NASA revived fuel cell technology with new materials and used it on manned space flights. These new fuel cells were quiet, reliable, and clean, and produced water as a by-product. It was an ideal scenario. The fuel cells produced both power and drinking water for the astronauts.

Researchers around the world are using nanotechnology to make new fuel cell membranes that would substantially increase the energy output. Nanomaterials are being developed to take the place of the highly expensive platinum parts in current fuel cells, and nanotubes hold promise as hydrogen delivery systems.

All of this research could someday pave the way for better energy solutions.

Nanotech Instruments

Molecules with more than 10 atoms fall into the nanometer range. Scientists were not able to visualize individual molecules and nanoscale objects until the invention of some very powerful microscopes. These microscopes don’t use light to create an image of a nanoscale object.

Believe it or not, waves of light are too large – visible light has a wavelength between 400 and 750 nanometers. That’s much larger than many nanoscale objects and definitely larger than most molecules. Instead the specialized microscopes use very small probes or electrons.

With these microscopes, a very small, very sharp tip on the end of a lever is dragged across a nanoscale object. The movement of the lever is monitored with a computer, which creates an image. The method is much like a person moving their fingers over words written in Braille to read. This tip-scanning method is known as Scanning Probe Microscopy (SPM). Electron microscopes are similar to light microscopes except instead of directing light to a sample, they direct electrons to the sample.

What Is Nano?

Over the past decade a new term has entered our vocabulary and that word is “nano.” We hear the word in movies. It’s mentioned on television and in newspapers and magazines. Futurists say it will pave the way for unimaginable new possibilities. Pessimists are unsure.

There are many different opinions about where this new field will take us, but everyone agrees that this science and the new technologies that come from it have the possibility of significantly impacting our world.