Five amazing ultrasound inventions set to change the world (and not a pregnancy scan in sight)

Ultrasound can do a whole lot more than create images of unborn babies. Since it first became a near-indispensable medical tool in the 1930s, technology that produces sound waves so high-pitched that humans can’t hear them has found use in almost every branch of industry. The vibrations it creates can kill bacteria, weld plastics and even help to mature brandies in a matter of days rather than years.

Today, ultrasound is finding its way into even more applications, powering inventions that have the potential to make huge changes in their fields. Here are just a few of them:

1. Truly hands-free phones

We are on the brink of a real contactless alternative to touch-screen technology. Devices like the Microsoft Kinect can detect where you hands are and use that information as instructions. But placing your hands in exactly the right place to give the instructions you want to is still tricky enough to prevent this kind of gesture-based control system from being used more widely.

One company is using ultrasound to effectively create invisible buttons in the air that you can feel. An array of ultrasound transmitters produces and shapes sound waves to create small areas of force sensations on the skin in a specific location. So instead of waving your hand around and hoping it’s in the right place, you know instantly when you’ve activated the gesture recognition.

This has the potential to make everyday devices such as smartphones completely waterproof, contactless and effectively aware of the surrounding environment. The technology can also be combined with virtual reality systems to enable you to feel your artificially generated surroundings, which would bring a new dimension to video games and entertainment.

There are rumours that the next generation of smartphones will use ultrasonic fingerprint recognition so you don’t even need to touch your phone to unlock it. These phones could even incorporate ultrasound for wireless charging, where ultrasound energy could be converted to electrical energy within the phone. This energy would be projected from a transmit unit stored, for example, on the wall in your house.

2. Acoustic holograms

Ultrasound has long been used to create two-dimensional images of the body for doctors to study. But a very recent development that is likely to feature prominently in healthcare in the future is the ultrasound acoustic hologram.

In this technique, ultrasound is used to move micro-particles in a particular medium to form a desired image. For example, projecting sound waves through a specially-designed patterned plate into water containing plastic particles forces them into a particular alignment. Researchers think this kind of acoustic holography could be used to improve medical imaging but also to better focus ultrasound treatments.

3. Glasses for blind people

Another potential medical application of ultrasound is to enable blind people to “see” in a similar way to how bats do using the principle of echolocation. Rather than detecting reflected light waves to see objects, bats send out ultrasound waves and use the reflected sound to work out where things are. These echoes can provide information about the size and location of that object.

Researchers in California have created an ultrasonic helmet that sends out similar ultrasound waves. It then converts the reflected signals into audible sounds that the human brain can learn to process into a detailed mental image of the environment. In time, this technology could become more practical and portable, perhaps even one day incorporated into specially designed glasses.

4. Tractor beams

Given enough power, it is possible to ultrasonically levitate objects just with sound waves, and move them in different directions, effectively like a science fiction tractor beam. Researchers from the University of Bristol have shown that by controlling and focusing sound waves from an array of ultrasound sources can create enough force to lift a bead-sized object off the ground.

Lifting larger objects, such as a human, would require very high power levels, and it is not fully understood how damaging the acoustic forces would be to a person. But the technology has the potential to revolutionise a range of medical applications. For example it could be used to move drugs around the body to get them to their target cells.

5. Martian scanners

Ultrasound technology is already being investigated as an exploration tool. At high power, ultrasonic vibrations can be used to efficiently compact material, like a kind of drill hammering its way through. This has been proposed for use in the search for underground oil and gas deposits. Ultrasonic echolocation can also be used as a type of sensor to help aerial drones avoid obstacles so they can be sent into dangerous and difficult-to-reach locations.

But exploration is not limited to Planet Earth. If humans are ever to visit Mars, we’ll need new ways of analysing the Martian environment. Because of the low gravity on Mars, conventional drills wouldn’t be able to press down with as much force, so researchers are looking at how ultrasonic devices could be used to collect samples instead.

Identification of the neuronal suppressor of cataplexy, sudden weakening of muscle tone

External stimulus causing excitement such as laughter by a joke augments the amygdala activity. In narcolepsy patient (left) lacking orexin neurons, activities of the amygdala become excessive, causing cataplexy. In healthy person (right), orexin neurons augment the activities of serotonin neurons in the dorsal raphe nucleus, which reduce activities of the amygdala due to increased release of serotonin in the amygdala, which in turn inhibits cataplexy.

Sleep is of absolute necessity for us humans, although if one falls asleep all of a sudden while being awoken, it would cause a big trouble. The brain is equipped with sleep mechanism and wakefulness mechanism, which are regulated to be on or off in an adequate manner. It is orexin*1 that is important in regulating this switch. If orexin neurons are lost, one suffers from narcolepsy*2, a sleep disorder, where sleep and wakefulness are inadequately switched on and off. The typical symptoms are excessive daytime sleepiness and cataplexy*3. Cataplexy takes place when one is very excited in terms of one's emotion and if severe, one may lose the muscle tone of the whole body and fall down. Sleep is categorized into two, REM sleep and non-REM sleep. Dreams are dreamt usually during REM sleep, where most of the muscles are controlled to be relaxed (called atonia) in order to prevent the dreamer to make real actions. Cataplexy attack is thought that atonia, a characteristics of REM sleep, takes place while one is awoken. The research team previously found two types of neurons preventing narcolepsy by receiving orexin from orexin neurons. The one is noradrenaline neurons in the locus coeruleus of the brain, suppressing strong sleepiness, and the other is serotonin*4 neurons in the dorsal raphe nucleus of the brain, inhibiting cataplexy.

[Results]

In this study, the international research team led by the researchers of Kanazawa University has discovered that serotonin neurons in the dorsal raphe nucleus inhibits catalepsy by reducing activities of the amygdala*5 that controls emotion.

Serotonin neurons in the dorsal raphe nucleus extend projections throughout the brain and send information. In this study, with an optogenetic*6 tool, the team has discovered that catalepsy was almost completely inhibited by artificial augmentation of serotonin release induced by selectively stimulating serotonin nerve terminals in the amygdala in the narcolepsy model mice*7. The same experimental operation in the other brain region that controls REM sleep did not inhibit cataplexy. In addition, the team found that serotonin release reduced the amygdala activity. When the amygdala activity was artificially reduced in a direct manner, cataplexy was inhibited, while artificially augmented, frequency of cataplexy attack increased. Furthermore, the effect of orexin neurons inhibiting cataplexy was found to be abolished when serotonin release was inhibited selectively in the amygdala.

[Significance]

Cataplexy takes place, triggered by a sudden emotional excitement of positive valence such as a big laughter. This study has revealed that serotonin neurons do not directly suppress muscle tone weakening but inhibit cataplexy by reducing and controlling activities of the amygdala, which is involved in communicating emotional excitement. In fact, it is known that the amygdala of narcolepsy patients without orexin neurons responds excessively when the patients see, for example, interesting photos. By identifying neuronal pathway, orexin neuron - serotonin neuron in the dorsal raphe nucleus - the amygdala, the team believes that the current study has made a big step forward to understanding of the whole picture of the narcolepsy mechanism. It is also highly expected that new therapy would be developed for cataplexy.

[Glossary]

*1 Orexin
Orexin A and orexin B are neuropeptides produced from a single gene in certain neurons of the hypothalamus. They consist of about 30 amino acid residues and function as neurotransmitters to convey information between neurons. Orexin producing neurons (orexin neurons) extend nerve projections throughout the brain. Orexin released from the orexin nerve terminal exerts different functions in various regions of the brain. It is known to prevent narcolepsy by stably maintaining wakefulness as well as to function for promotion of eating and metabolism and of response for reward.

*2 Narcolepsy
A sleep disorder characterized with excessive daytime sleepiness and with cataplexy. Caused by degeneration and loss of orexin neurons. Most patients experience their first narcolepsy symptoms in adolescence, and it is said that one patient is found out of 500 to 2000 persons.

*3 Cataplexy
Cataplexy is triggered by strong emotion and marked by sudden weakening of muscle tone of the whole body, the knee, the low back, the jaw, or the eyelid, but without consciousness impairment in many cases. One of the major characteristics of narcolepsy.

*4 Serotonin
Serotonin is one of the physiologically active amines and functions as a neurotransmitter to convey information between neurons in the brain. Serotonin producing neurons are found in specific regions of the brain and the dorsal raphe nucleus is one such region. Serotonin neurons extend projections throughout the brain. Serotonin released from the nerve terminals is involved in a wide variety of brain functions. Since the activities of serotonin neurons are high during wakefulness but low during sleep, serotonin is thought to be involved in regulating wakefulness and sleep. There is a hypothesis that low level of serotonin in the brain is one of the causes of depression.

*5 Amygdala
A brain region playing essential roles in processing emotional responses as well as in emotional memory. Emotion is defined as a temporal and big change of feelings induced rather in an acute manner, such as anger, terror, delight and sorrow. Emotion is accompanied with physical, physiological, and behavioral changes, and is distinguished from mood, that signifies weak feelings prevailing for a mid- and long-term in a mild manner.

*6 Optogenetics
Technique to manipulate the functions of cells by exogenously expressing light-activatable proteins and illuminating light.

*7 Narcolepsy model mouse
Genetically modified mouse, which lacks signal transduction by orexins, such as orexin-gene knockout mouse and orexin-receptor-gene knockout mouse. Narcolepsy model mouse exhibits symptoms similar to those of a narcolepsy patient. In this study, genetically modified mice with their orexin neurons being degenerated are used as narcolepsy model mice.