Nanomotors - Seminar Paper

ABSTRACT

The world is going to be too fast and too small due to the modern technologies like nanotechnology. Have you ever thought that motors can be fabricated as small as that can be placed on a head of a pin? Have you ever imagined that radars and sensors flying in the air? Have you ever imagined that a motor will enter in to your body and it will detect and destroy cancer cells? Yes these things are possible with the miracle technology called Nanotechnology.

Our paper deals with the recent trend in nanotechnology i.e. the development of NANOMOTORS.  We have discussed about the construction, operation and future expected applications of the emerging Nanomotors. We have also discussed about the expected types of nanomotors such as solar powered nanomotors, military application Nanomotors.

A Nanomotor is a molecular device capable of converting energy into movement and forces on the order of the piconewtons. These motors are going to be widely used in the fields of military, medicine, research and also in the field of Nanorobots.

INTRODUCTION

Nanotechnology refers broadly to a field of applied science and technology whose unifying theme is the control of matter on the molecular level in scales smaller than 1 micrometer, normally 1 to 100 nanometers, and the fabrication of devices within that size range.

NEMS:

NEMS or nanoelectromechanical systems are similar to MEMS but smaller. They hold promise to improve abilities to measure small displacements and forces at a molecular scale, and are related to nanotechnology.

NANOMOTORS:

A Nanomotor is a nanotechnology-based device, operating at a molecular level, and which is capable of effecting forces of the order of piconewtons. Energy acquired by a nanomotor can thus be converted into motion at the molecular level

How it works?

The motor works by shuffling atoms between two molten metal droplets in a carbon nanotube. One droplet is even smaller than the other. When a small electric current is applied to the droplets, atoms slowly eek off the larger droplet and join the smaller one. The small droplet grows - but never gets as big as the other droplet - and eventually bumps into the large droplet. As they touch, the large droplet rapidly sops up the atoms it had previously sloughed off. This quick shift in energy produces a power stroke. 

The technique exploits the fact that surface tension -- the tendency of atoms or molecules to resist separating -- becomes more important at small scales. Surface tension is the same thing that allows some insects to walk on water.

Although the amount of energy produced is small -- 20 microwatts -- it is quite impressive in relation to the tiny scale of the motor.

The whole setup is less than 200 nanometers on a side, or hundreds of times smaller than the width of a human hair. If it could be scaled up to the size of an automobile engine, it would be 100 million times more powerful than a Toyota Camry's 225 horsepower V6 engine.

STRUCTURE OF NANOMOTOR:

The Nanomotor is a piezo driven linear motor consisting of a cylindrical housing and a slider with a free axial hole inside. It utilizes a piezo tube for fine positioning and a pulse wave produced by the same piezo tube for coarse movements. Every point of its stroke can be reached with a speed of up to 5 mm/s. 

In its free axial hole the Nanomotor can transport a tip, a hose, an electrode, a hypodermic needle, a glass fiber or even a microgripper.

Size Comparison of a Nanomotor

The Nanomotor is available in three different versions. The "Small" Nanomotor is half the size of a match stick. It can lift six times of its own mass. The dynamic force of this Nanomotor is so high, that even imprints in diamond surfaces can be produced.

Special versions of the Nanomotor can operate in Ultra High Vacuum, in liquid Helium, even under water or as non-magnetic drives. 

   The Nanomotor is most comfortably controlled by the NWC - Network Controller. Other electronics to drive the Nanomotor is also available, please ask for information.

OPERATION OF NANOMOTORS:

The thin vertical string seen in the middle is the nanotube to which the rotor is attached. When the outer tube is sheared, the rotor is able to spin freely on the nanotubes bearing. The lure is of miniature robots that could be powered by nanomotors, although this is still some way off. The motors were built using a atom-fine point of a nano-probe, inserting the circuits into place on a silicon chip. 

 The motors essential element is the tube of pure carbon

The motor sits in the middle of a silicon chip four millimeters square. The motor itself is much, much smaller - the shaft is a half a tenth of a thousandth of a millimeter thick. The axle element is about 20-40 nanometers in diameter, and that's really the part of the motor that enables it to spin. There is a rotor which is about 400 nanometers wide, and then on the outside there are stators, just like you would have on an electrical motor, which are about a micron apart. The stators are electrodes that give the drive to the motor, and drive it by static electricity. 

But the key element of the motor is a multiwall nanotube. A multiwall nanotube is graphite wrapped into a tube. Graphite is layers of carbon, like chicken wire. A nanotube is if you were to take those layers and wrap them into a cylinder, and a multiwall nanotube is like a leek, in that it's a cylinder within a cylinder. In effect, the nanotubes are shaped like drinking straws, but on a molecular scale. We're using the inner tube as a sort of axle, and the outer tube as the outside bearing. That really is what makes it possible to create this nanomotor. It was founded that the motor is so small that the researchers do not yet know exactly how it behaves. It's hard to image whether it's flipping or spinning, and scientists were still working on trying to resolve that, We know that it flips back and forth faster than 33 milliseconds because that's the frame rate that we're able to grab them at. But we still haven't conclusively shown what's going on at the nanoscale.

TYPES OF NANOMOTORS:

Nanotube Nanomotor:

Nanomotor- the motor is about 500nm across: 300 times smaller than the diameter of a human hair.

The scientists developed rotational bearings based upon multiwall carbon nanotubes. By attaching gold plate (with dimensions of order 100nm) to the outer shell of a suspended multiwall carbon nanotube (like nested carbon cylinders), they are able to electrostatically rotate the outer shell relative to the inner core. These bearings are very robust; devices have been oscillated thousands of times with no indication of wear. 

These nano electro mechanical systems (NEMS) are the next step in miniaturization that may find their way into commercial aspects in the future. 

The thin vertical string seen in the middle is the nanotube to which the rotor is attached. When the outer tube is sheared, the rotor is able to spin freely on the nanotube bearing.

Nanomotors with Laser Fuel

 Forget fancy fuel cells Laser Light may be the fuel of the future for nanotech robots and motorized tools so small they can manipulate individual cells and molecules. 

It was found that that light can spin nanotubes with ultra-high frequencies; Ultra fast frequencies tens of gigahertz are typical rotational frequencies in molecules and could be used to spin other molecules. Lasers transfer the angular, or sideways, momentum of infrared photons to carbon nanotubes. The tubes then rotate like whirring turbines. Scientists at the Department of Energy's Oak Ridge National Laboratory designed the first laser-driven nanomotor a cylindrical carbon tube surrounded by a carbon sleeve. In theory, applying an oscillating laser field would make the tube rotate enough to power a tiny motor,

When we started to consider nanotechnology, we thought that a method would be required to use some form of energy that could create mechanical motion. The simplest approach we could envision was that of rotation of nanotubes with lasers." 

Nanomotors with solar fuel:

Scientists have developed tiny four-stroke engines that run on sunlight. The nanomotor so small that 3.8 million of them lined up end-to-end would barely span the width of a penny--generate absolutely no waste. Each little motor is just 5 nanometers in length, macaroni-like in shape, and has a ringed structure at one end that moves back-and-forth like the pistons under your car's hood.

Energy, in the form of photons from sunlight, excites one end of the molecule, which sets off a four-step process. Electrons are transferred along the molecule until they reach the ring structure, causing it to slide 1.3 nanometers forward on the molecule.

As the electron continues its path, it reaches a section that recycles it back to the beginning. This causes the molecule to "reset," and the ring returns, piston-like, to its original position. The whole process takes about 100 microseconds. 

Each step is similar to the mechanical functions of the four-stroke engine that powers a car down the road--fuel injection and combustion, piston displacement, exhaust removal, and piston replacement.

Except in this case, the exhaust is an electron, not smog-producing pollutants. The molecule, called rotaxane, forms naturally. It's also autonomous, meaning that it will continue operating as long as energy is available. It can work with others, or function all by itself. It can be driven at high frequency, and in mild environmental conditions it is quite durable, staying stable for at least 1,000 cycles. While the nanomotor is less efficient than some fuel-powered engines--it has an efficiency of only 2 to 12 percent--the researchers point out that it doesn't need refueling and that sunlight is free.

The solar-powered four-stroke nanomotor. Energy from the sun drives the movement of the yellow ring structure like a piston.

Nanomotors with single DNA molecule:

They are still many years away, but molecular motors that could radically improve manufacturing and medicine just took a step closer to reality.

A University of Florida chemistry professor has made a "nanomotor" from a single DNA molecule. The motor, so small that hundreds of thousands could fit on the head of a pin, curls up and extends like an inchworm.

While it is not the first such DNA motor, nanomotor is the first to be built from a single molecule rather than several different DNA molecules. This makes it easier to use and edges such motors closer to real-life applications in the rapidly emerging field of bionanotechnology.

The first use of DNA motors is already beginning to emerge in the form of biosensors, these are instruments that researchers use to detect a very specific piece of DNA that may be related to disease. Such sensors "enable us to detect only a few DNA molecules that contain specific sequences and thus possibly diagnose patients as having such specific sequences related to a cancer gene or not, it is anticipated that nanomotors will play an active role in clinical treatment.

APPLICATIONS OF NANOMOTOR:

As the size of the motor decreases it has various applications in the field of military, medicine, and also in the field of research purposes. The various applications are as follows:

• Detection and destroying cancer cells:

These nanomotors could be injected along with drugs that kill cancer cells or tumors, when the drugs reach the disease site, the nanomotors would make the drug molecules attach and stick to the cancer cell membrane.

Perhaps more importantly, the motors precision would give them the ability to prevent the drugs from attaching to noncancerous molecules or healthy parts of the body eliminating the debilitating effects.

Proposed application in test tube manufacturing:

Some scientists believe that nanomotors could also be used in so-called "test-tube manufacturing." This approach turns traditional manufacturing on its head. Where traditional manufacturing creates structures from existing materials or parts, test-tube manufacturing involves building structures from the smallest molecular or atomic components. 

• Scanning Probe Microscopy:

They can move the sensor with Nanometer precision or move the sample. The Nanomotor is a perfect tool to solve the main two problems in Scanning Probe Microscopy:

Additionally the coarse step mode allows scanning heads with up to a centimeter of stroke. The sensor can be a structuring tool at the same time.

• As ingenious as today’s miniature devices are today, they still require bulky power supplies or fuel systems-negating some innovative work in various areas, such as unmanned vehicles. 

Scientists have developed a nanogenerator that converts motion into electrical current. The nanogenerator is an array of tiny filaments-zinc oxide nanowires-that produces continuous direct-current electricity from mechanical energy. Safe enough for use in biomedical applications, the nanoscale generator could generate energy from internal vibrations and even blood flow. 

“If you had a device like this in your shoes when you walked, you would be able to generate your own small current to power small electronics,” “Anything that makes the nanowires move within the generator can be used for generating power. Very little force is required to move them.”

The nanogenerator is expected to produce as much as four watts per cubic centimeter, sufficient power for nanometer-scale defense, environmental, and biomedical devices. Potential applications include powering nanomotors, biosensors implanted in the body, environmental monitors, and nanoscale robots. 

FEATURES OF NANOMOTOR:

• The size of the nanomotor is too small.
• Less requirement of space due to its small size.
• Used in human saving purpose (destroying cancer cells).
• Manufacturing cast is low when produced in bulk amount.
• Expected to be high efficiency.
• It’s a versatile device.

CONCLUSION:

Thus the Nanomotor which is going to be widely used in the future will bring a drastic change in the field of medicine and research. The usage of nanomotor will not be in a single field it will rule the world in future. If the nanomotors are developed widely then you could stuff hundreds of them into the period at the end of this sentence.