Levitation

Levitation (lat. levitas = lightness ) refers to the levitation of an object. For this purpose, using a force acting weight force is compensated and placed an object in space, where no direct contact with the ground or solid objects composed. Some methods need for power transmission, a gaseous medium ( eg air), which must be part of the object.

Compressed Air Levitation

A levitation of an object can be achieved, for example, by, as in the air hockey, air is blown against the object. When training for parachute jumping, it is used in the body flying. Alternatively, air can be pressed from the object down. In a hovercraft, this principle is used, which allows the vehicle to float on an air cushion.

Acoustic Levitation

In this small sample in the pressure node of a standing ultrasonic field are non-contact position. This method was first tested in 1933. It allows for space research under the influence of microgravity in space conducting experiments materialkundlicher because hereby small samples can be positioned without contact and accurately.

The acoustic levitation in the standing wave field based on the forces acting in the alternating pressure field of ultrasonic standing waves on the particular sample. They embark on axial and radial forces. Using acoustic levitation, for example, polystyrene beads or water droplets are levitated.

On the edge of the acoustic levitation, the ultrasound air bearing, which is caused by the near-field effect in the ultrasonic field counts. It is used primarily for transporting and gripping flat objects.

Magnetic Levitation

Electrical and magnetic forces enable real, without any mechanical contact that is auskommende, Levitation: body can repel each other depending on their charge or polarity, and so gravity can be compensated. However, with this method, once practical problems, because Earnshaw's theorem states that, so take with static fields, such as those of normal permanent magnets that produce no stable equilibrium positions. One can manage to leave a permanent magnet briefly hover over another, but even the smallest disturbances (wind, vibrations) to crash him so at best. However, there are several ways to produce still stable levitation.

Levitron

A magnetic gyro can levitate in a static field, as he so directs by its centrifugal movement at a fault straight again, that stability is maintained.

Active Field Control

When the location is to the levitating body sensors detected, control loops can customize the field so that disturbances are compensated. This method can be realized with different methods, it is been used as a single on a larger scale on toy scale addition, most famously in magnetic. Are commercially available magnetic suspension couplings for scales with which, for example, a sample contained in a vacuum vessel can be weighed from the outside by a steel wall.

Diamagnetism

Diamagnetic substances are repelled by magnetic poles - both north and south poles of. Characterized it provides for the potential field different from the Earnshaw 's theorem does not apply, and there is a stable equilibrium positions. How can hover over permanent magnets as graphite plates with sufficiently strong surrounding fields can even small permanent magnet between human fingers ( which are also diamagnetic ) be held in abeyance. Superconductors are perfectly diamagnetic; with them can be achieved particularly impressive levitation.

In a conductor, eddy currents are induced by the alternating magnetic field. Here, the magnetic field is directed opposite to that of the magnets obtained. Normal conductor such as copper or aluminum behave like diamagnetic substances. As a possible arrangement of conductors and magnets to each other, the following solutions are feasible:

• Fast rotating magnet (or manager)
• Fast moving relative to one another magnet and conductor ( this is to be used in the system Inductrack in maglev technology)
• A conductor in an alternating field of an electromagnet located ( high frequency is required)
• Crystal growth is possible with the Levitationstiegel - a variant of the Czochralski method, wherein the melt of the material from which the crystal is pulled, is held by the same alternating electromagnetic field which is heated in the air.

Optical Levitation

In the optical levitation mass particles are levitated by means of laser light. This is done through the momentum of photons of the radiation pressure, which counteract the gravitational force. What is required for a sufficiently high intensity of the laser beam. For a few microns large objects lasers are necessary in the order of 1 watt. The optical tweezers is an example of application of this methodology.