ultrasound

47 Articles

Levitation By Sound

August 2, 2021 by 12 Comments

Levitating things with magnets is no great feat these days. We don’t see as many projects with sonic levitation. However, Japanese engineers have a new method to lift objects using sound. The process isn’t totally reliable yet, but it may lead to better methods in the future. You can see a video about the work below.

Manipulating very small items via laser or acoustics isn’t new. However, there are significant limitations to current methods. This new approach uses an array of hemispherical ultrasound transducers. By controlling the amplitude and phase of each transducer, an acoustic trap forms and can pick up a 3 mm polystyrene ball without direct contact.

Manipulating objects without contact interests us for a few reasons, not the least of which is circuit assembly. Robust technology of this type could also add new dimensions to additive manufacturing. Of course, it is a long way from a 3 mm polystyrene ball to a surface mount component. However, you have to admit watching components just float through the air to their final resting places would be something to see.

Not that we haven’t seen sonic levitation before. Magnetic levitation tends to be easier, but also has some limitations.

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How To Monitor Blood Pressure Without Raising It

February 27, 2021 by 16 Comments

Does anyone actually enjoy the sensation of being squeezed by a blood pressure cuff? Well, as Mom used to say, it takes all kinds. For those who find the feeling nearly faint-inducing, take heart: researchers at UC San Diego have created a non-invasive medical wearable with a suite of sensors that can measure blood pressure and monitor multiple biochemicals at the same time.

The device is a small, flexible patch that adheres to the skin. So how does it manage to measure blood pressure without causing discomfort? The blood pressure sensor consists of eight customized piezoelectric transducers that bounce ultrasonic waves off the near and far walls of the artery. Then the sensor calculates the time of flight of the resulting echoes to gauge arterial dilation and contraction, which amounts to a blood pressure reading.

This patch also has a chemical sensor that uses a drug called pilocarpine to induce the skin to sweat, and then measures the levels of lactate, caffeine, and alcohol found within. To monitor glucose levels, a mild current stimulates the release of interstitial fluid — the stuff surrounding our cells that’s rife with glucose, salt, fatty acids, and a few minerals. This is how continuous glucose monitoring for diabetes patients works today. You can check out the team’s research paper for more details on the patch and its sensors.

In the future, the engineers are hoping to add even more sensors and develop a wireless version that doesn’t require external power. Either way, it looks much more comfortable and convenient than current methods.

Building An Ultrasonic Levitation Rig

February 2, 2021 by 12 Comments

Levitation may sound like magic, but there are a wide variety of physical phenomena that can be manipulated to generate the desired effect. In this case, [Mirko Pavleski] has built a rig capable of levitating small, lightweight particles through the use of ultrasound.

The rig uses a 60W ultrasonic transducer, operating at approximately 40 KHz, to generate a standing wave in combination with a reflector – essentially a rigid piece of material off which sound waves can be bounced. The interaction between the sound waves as they are emitted from the transducer and bounce off the reflector creates what is known as a standing wave, wherein there are areas of high and low amplitude that do not move in space. These areas correspond to the wavelength of the emission from the transducer, and allow lightweight pieces of styrofoam to be placed in to the low amplitude areas, where they are held in place by the wave.

It’s quite astounding the first time you see it in action, as the tiny particles appear to simply float in the air apropos of nothing. We’ve explored deeper applications of the technique before, too. Video after the break.

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Leaking Data By Ultrasound

December 6, 2020 by 19 Comments

Human ears are capable of perceiving frequencies from roughly 20 Hz up to 20 kHz, at least when new. Correspondingly, our audio hardware is designed more or less to target these frequencies. However, there’s often a little extra capability at the upper edges, which [Jacek] shows can be exploited to exfiltrate data.

The hack takes advantage of the fact that most computers can run their soundcards at a sample rate of up to 48 kHz, which thanks to the Nyquist theorem means they can output frequencies up to around 24 kHz — still outside the range of human hearing. Computers and laptops often use small speaker drivers too, which are able to readily generate sound at this frequency. Through the use of a simple Linux shell script, [Jacek] is able to have a laptop output Morse code over ultrasound, and pick it up with nothing more than a laptop’s internal microphone at up to 20 meters away.

[Jacek] enjoys exploring alternative data exfiltration methods; he’s previously experimented with Ethernet leaks on the Raspberry Pi. Of course, with any airgap attack, the real challenge is often getting the remote machine to run the exfiltration script when there’s no existing remote admin access to be had. Video after the break.

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Faux Radar Uses Ultrasound & Python

July 18, 2020 by 25 Comments

Radars are simply cool, and their portrayal in movies and TV has a lot to do with that. You get a sweet glowing screen that shows you where the bad guys are, and a visual representation of your missiles on their way to blow them up. Sadly, or perhaps thankfully, day to day life for most of us is a little less exhilarating. We can make do with a facsimile of the experience instead.

The project consists of an Arduino Uno outfitted with an ultrasound module that can do basic range measurements on the order of tens of centimeters. The module is then placed on a servo and scanned through a 180 degree rotation. This data is passed back to a computer running a Python application, which plots the results on a Plan Position Indicator, or PPI – the sweeping display we’re all so familiar with.

While it’s unlikely you’ll be using such a setup to engage bandits, it could prove as a useful module for robot navigation or similar applications. We’ve seen ultrasonic transducers used for exactly that. Video after the break.

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Contactless Doorbell Built To Avoid Coronavirus

June 4, 2020 by 15 Comments

It’s often said that necessity breeds creativity, and during a global pandemic such words have proved truer than ever. Realising the common doorbell could be a potential surface transmission point for coronavirus, [CasperHuang] whipped up a quick build.

The build eschews the typical pushbutton we’re all familiar with. Instead, it relies on an ultrasonic distance sensor to detect a hand (or foot) waved in front of the door. An Arduino Leonardo runs the show, sounding a buzzer when the ultrasonic sensor is triggered. In order to avoid modifying the apartment door, the build is housed in a pair of cardboard boxes, taped to the base of the door, with wires passing underneath.

It’s a tidy way to handle contactless deliveries. We imagine little touches like this may become far more common in future design, as the world learns lessons from the COVID-19 pandemic. Every little bit helps, after all. Video after the break.

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Fear Of Potato Chips: Samy Kamkar’s Side-Channel Attack Roundup

March 9, 2020 by 13 Comments

What do potato chips and lost car keys have in common? On the surface, it would seem not much, unless you somehow managed to lose your keys in a bag of chips, which would be embarrassing enough that you’d likely never speak of it. But there is a surprising link between the two, and Samy Kamkar makes the association in his newly published 2019 Superconference talk, which he called “FPGA Glitching and Side-Channel Attacks.”

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