What do scientists do with ultrasound?

- Dec 21, 2019-

What is ultrasound

Ultrasound is a sound wave with a frequency above 20,000 Hertz, which is usually inaudible to the human ear.

Ultrasonic wave has good directivity, strong penetrating ability, easy to obtain more concentrated sound wave energy, and can travel far in water.

Because of these characteristics, ultrasonic applications in daily life is very wide, can be used for ranging, speed measurement, cleaning, welding, gravel, sterilization and so on.

Ultrasonic products must have been used by everyone, such as going to the hospital to clean teeth, go to the eyeglasses shop to wash glasses, when the physical examination to do B super.

Have you found that ultrasound is still very powerful?

Come to the lab and see the wonderful applications of ultrasound

At the ultrasonic technology center of the institute of acoustics of the Chinese academy of sciences, nearly 100 researchers delve into ultrasound-related issues every day.

The predecessor of ultrasonic technology center is a supersonic room founded by academician ying chongfu, a famous Chinese physicist and educator.

At present, there are five research directions in total, which are testing acoustics and nondestructive testing of Marine equipment, solid acoustics and deep drilling, microacoustics and microdevices, medical acoustics, computational acoustics and sound energy application.

1. Ultrasonic cleaning

Ultrasonic cleaning refers to the process of using ultrasonic wave to remove dirt on the surface of the sample in the liquid, such as removing oil stains or dust on the surface of the glasses.

Here, the main use of ultrasonic cavitation in the liquid to produce micro-jet, shock wave and other strong sound effect, peel off the surface of the sample dirt, to achieve the purpose of cleaning, just like the high-pressure gun cleaning the car.

At present, ultrasonic cleaning has been a mature technology, in the laboratory, hospital and other occasions have been applied.

Ultrasonic cleaning machine has also become one of the household electrical appliances, used to clean glasses, jewelry and other daily supplies.

2. Phacoemulsification

Phacoemulsification refers to the process in which two (or more) solutions (such as oil and water) are difficult to be mixed under the action of ultrasonic energy to form a dispersion system, in which a liquid is evenly distributed in another liquid to form an emulsion.

The emulsion formed by phacoemulsification is of good uniformity and stability. Therefore, the latex and other cosmetics often used by women, the dairy drugs in hospitals, and the dairy food can be prepared by phacoemulsification.

Didn't expect that?

3. Ultrasonic atomization

The weather in the north is dry and many families use humidifiers.

Once plugged in, the humidifier begins to emit smoke.

In fact, this "smoke" is not real smoke, but very small particles of fog droplets.

How does a humidifier turn a big drop of water into a small one?

Look at the GIF above, isn't it intuitive?

At the bottom of the humidifier is an ultrasonic transmitter that emits ultrasonic waves like a rocket blast, breaking the water into tiny droplets that shoot out of the water and become what we see as an atomizing effect.

It feels cool because it's not water heating and evaporating.

The atomizer in the hospital also USES ultrasound to atomize.

4. Dynamic photoelastic imaging

We know that sound waves are invisible.

But using dynamic photoelastic imaging, we can see the path of sound waves through a transparent solid very directly.

Ultrasonic waves in solids have the ability to change the polarization of light, a transient birefringence effect.

Some materials (such as glass, plastics, and epoxies) do not normally undergo birefringence, but do when they are subjected to internal stresses or electric fields.

In general, it is difficult for natural light to pass through two polarizing plates that are perpendicular to each other. When the transparent test block with ultrasound is placed between two polarizing plates that are perpendicular to each other, due to the temporary birefringence effect, part of the incident light can pass through and be captured by the imaging screen, thus showing the ultrasonic wave.

The trajectory of ultrasonic can be observed by adjusting the delay of incident light and ultrasonic emission by time-delay synchronous device.

Compared with analytical and numerical methods, the experimental results provided by dynamic photoelastic imaging are more accurate and close to the physical model.

5. "industrial b-ultrasound"

Using ultrasound's ability to generate reflection and diffraction when it encounters an uneven or discontinuous part of the transmission medium, researchers have developed a medical ultrasound (such as the first photograph of a fetus) and an "industrial ultrasound."

Medical ultrasound

Ultrasonic diagnostic equipment can be divided into A, B, C, F four categories, among which the most commonly used is B.

What say at ordinary times "B exceed exceed" send ultrasonic wave to human body namely, accept the reflection wave of viscera inside body at the same time, carry information to reflect on the screen.

Ultrasonic and common voice, can the directional transmission, part of the sound penetrating object, part of the sound is absorbed by the organization, part of the sound is reflected, ultrasound using the reflected signal is determined by detecting organization shape, its principle and the principle and dolphins echo-location in bats are similar, using the emission signal and the echo signal of time to determine the location of the organization.

Especially at the tissue interface, ultrasonic waves have strong reflections, which are used to characterize the appearance of reconstructed tissues and organs.

Because of the different penetration depths and wavelength lengths of different sound waves, the ultrasound used in specific body examinations is usually defined in the range of 2MHz to 15MHz.

In clinical imaging, the ultrasonic probe comes into direct contact with the skin surface, and the probe and skin are coated with coupling mucus to facilitate the transmission of ultrasonic signals between the probe and tissues and organs.

Ultrasonic nondestructive inspection

The simplest conventional ultrasonic nondestructive inspection equipment consists of three parts: ultrasonic transmitting and receiving module, ultrasonic transducer and oscilloscope.

First, the ultrasonic transmitting and receiving module generates electrical pulses that enter the ultrasonic transducer and become ultrasonic waves.

When the ultrasonic wave propagates inside the workpiece under test, it will be reflected and received by the transducer when it encounters defects, and finally abnormal signals will be displayed on the oscilloscope interface.

Therefore, by moving the transducer and observing the size and arrival time of the flaw echo, we can determine the location of the flaw, estimate the shape and size of the flaw, and thus complete the nondestructive testing of the workpiece.

For example, before a car leaves the factory, it must go through a process of ultrasonic inspection of the gears to check that the gears are in good condition before the "quality certificate" is affixed.