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Is (ultra)sonic electromagnetic induction possible?

In order for electromagnetic induction to take place, a conductor must "cut" the lines of force of a magnet.

If some sort of surface (in my imagination, a silicon chip, but an sized surface would probably work)... were to have hundreds (or thousands, or millions) of thin, ultra-sensative, conductive "hairs" or "wires" wired to the surface; and if a permanent magnet and ultrasonic sound waves were introduced to the chip (or whatever), would the wire generate an electric current because of the millions (or hundreds, or thousands) of "hairs" vibrating slightly?

I would imagine that if it were possible (I should probably just expiriment with it myself), even thousands of the tiny conductive "hairs" would produce only a small current.

It's an outrageous idea, but I just have to know if anyone knows whether or not it's possible.

Please only hard, scientific answers... External links would be nice... I'll provide extra information if necessary.

Electromagnetic induction of ultrasonic waves is restricted to conducting materials - like eddy current testing - because it involves inducing eddy currents in the surface of the part by a near-by coil of wire. A magnetic field supplied by a near-by magnet interacts with this eddy current to produce a mechanical force on the surface to excite ultrasonic vibrations. The same configuration of coil and magnet also detects mechanical motion of the surface because the motion of a conductor in a magnetic field produces currents that are detected and measured by the near-by coil.

This transduction by induction has the following advantages for NDT: The "near-by" feature implies an air gap next to the part surface and, thus, no coupling liquid or grease layer is present to restrict the range of temperatures or inspection speeds available for testing. The fact that the transduction process takes place within a thin layer at the surface of the part allows the time-of-flight (or phase) of the ultrasonic wave to be measured with great accuracy so that dimensions and physical properties of materials can be used for quality assurance purposes. The shape of the coil and the direction of the magnetic field allow the type (shear or longitudinal) and direction of propagation of the wave to be controlled by the transducer design. Special wave types (e.g., shear horizontal, Lamb, Rayleigh) are readily available to satisfy unusual inspection problems. Coils that are large or contoured to fit odd shapes are inexpensive and extend the range of part geometries available for inspection.

The primary disadvantage of EMATs is their inefficiency. However, this drawback has been overcome with modern electronic design and digital signal processing techniques.

Introduction: The transducers usually used for ultrasonic testing are hand-held probes that must be coupled to the object being tested by a water bath or a thin layer of grease. This latter requirement is often messy and adds considerable mechanical complexity to the test as well as challenging the skill of the operator to get reproducible results. Eliminating this coupling chore and introducing transducers that can operate across an air gap has always been a "holy grail" quest. About 40 years ago, the quest began to be fulfilled with the introduction of high power lasers and air coupling techniques that are being described in the accompanying papers. This paper describes an electromagnetic technique that operates across a small air gap similar to the gap under eddy current sensors. Thus, it is only technically a non-contact sensor. However, it is able to takes full advantage of the absence of a liquid coupling layer. It generates and detects ultrasonic vibrations in a thin surface layer of metallic objects and, therefore, is immune to small surface undulations or layers such as dirt, paint, rust, grease, etc. that prevent piezoelectric transducers from giving reliable resultsin hostile environments. The physical principles are based on the same electromagnetic induction processes that govern electric motors and generators. That is, a wire carrying an alternating current and held close to a conductor will induce eddy-currents in the conductor. If a large magnetic field also floods the area of the eddy-current, forces are generated in the conducting surface by electric motor action and these launch acoustic waves into the conductor at the same frequency as the current that drives the wire. When used as a receiver, acoustic vibrations inside the conductor move the surface under the wire. In the presence of a magnetic field, this motion produces an eddy current in the conductor surface that produces a magnetic field that extends across the air gap to induce a current in the near-by wire connected to a preamplifier.

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