Diamagnetic Levitation

Magnetic Levitation is not new to the motion industry. Many articles have been published about its use in transportation, particularly in monorails, and in levitating displays. Magnetic bearings have been used in pumps, compressors, steam and gas turbines, motors, and centrifuges. However, these complex applications require electromagnets, sensors, and control systems. Moreover, these active levitation systems are costly and function only when energy is supplied. In these web pages, we discuss diamagnetism, a source of simple, straightforward levitation that requires no energy supply and can last virtually forever.

Diamagnetism is one of the three types of magnetic phenomena that can be used to levitate objects. Unlike the more common ferromagnetism and paramagenetism, diamagnetic levitation is intrinsically stable, and operates at room temperatures.

Levitating Graphite.

The phenomenon of diamagnetic levitation has long been a laboratory curiosity, used mainly for startling effects such as levitating living creatures.

Applications

• SRI's hybrid clean-room transport levitation system developed for a commercial client, holds the world's record for the largest diamagnetically levitated mass: 22 lbs (10.0 kgs).
• We have demonstrated the ability to stably levitate and control multiple millimeter-scale objects. This capability is embodied in our HERMES bead-chemistry system.
• Using our diamagnetic levitation technology, we have demonstrated a levitated flow meter with a turndown ratio of 1000:1, a frictionless micromotor operating at 21,000 rpm, and a seismic sensors sensitive down to a few hertz.

A key to many diamagnetic levitation applications are linear and rotary bearings. SRI has developed several novel configurations that exploit the passive stability of diamagnetism. One such rotary bearing is shown in this video of a floating graphite ring.

Floating Ring Rotary Bearing.

The possible applications for diamagnetic levitation are endless:

• Microdevices: “dry” compass, chemical sensors, semiconductor testing
• Microrobots: combinatorial chemistry, electronics automation, small assembly
• Others: games and toys, materials handling, microgravity environment simulations

Patents and Awards

SRI has actively studied this phenomenon and developed mechanisms to harness its power in many useful applications resulting in several inventions, patents, and awards. Some recent examples follow.

• SRI Receives Patent for Frictionless Transport Technology - On December 5th, 2002 SRI received a patent for frictionless transport technology based on diamagnetic levitation.
• SRI International received two "Best of Show" awards at the Sensors and Motion Control Exposition held in Anaheim, California (May 9-11, 2000) for its passive diamagnetic levitation system. SRI's entry won against dozens of other entries for top honors at the jointly held events, reaffirming our role as a leading technology innovator. (picture from expo)