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Hackaday Links: May 16, 2021

With the successful arrival of China’s first Mars lander and rover this week, and the relatively recent addition of NASA’s Perseverance rover and its little helicopter sidekick Ingenuity, Mars has collected a lot of new hardware lately. But while the new kids on the block are getting all the attention, spare a thought for the reliable old warhorse which has been plying Gale Crater for the better part of a decade now — Curiosity. NASA has been driving the compact-car-sized rover around Mars for a long time now, long enough to rack up some pretty severe damage to its six highly engineered wheels, thanks to the brutal Martian rocks. But if you think Curiosity will get sidelined as its wheels degrade, think again — the rover’s operators have a plan to continue surface operations that includes ripping off its own wheels if necessary. It’s a complex operation that would require positioning the wheel over a suitable rock and twisting with the steering motor to peel off the outer section of the wheel, leaving a rim to drive around on. JPL has already practiced it, but they predict it won’t be necessary until 2034 or so. Now that’s thinking ahead.

With all the upheaval caused by the ongoing and worsening semiconductor shortage, it might seem natural to expect that manufacturers are responding to market forces by building new fabs to ramp up production. And while there seems to be at least some movement in that direction, we stumbled across an article that seems to give the lie to the thought that we can build our way out of the crisis. It’s a sobering assessment, to say the least; the essence of the argument is that 20 years ago or so, foundries thought that everyone would switch to the new 300-mm wafers, leaving manufacturing based on 200-mm silicon wafers behind. But the opposite happened, and demand for chips coming from the older 200-mm wafers, including a lot of the chips used in cars and trucks, skyrocketed. So more fabs were built for the 200-mm wafers, leaving relatively fewer fabs capable of building the chips that the current generation of phones, IoT appliances, and 5G gear demand. Add to all that the fact that it takes a long time and a lot of money to build new fabs, and you’ve got the makings of a crisis that won’t be solved anytime soon.

From not enough components to too many: the Adafruit blog has a short item about XScomponent, an online marketplace for listing your excess inventory of electronic components for sale. If you perhaps ordered a reel of caps when you only needed a dozen, or if the project you thought was a done deal got canceled after all the parts were ordered, this might be just the thing for you. Most items offered appear to have a large minimum quantity requirement, so it’s probably not going to be a place to pick up a few odd parts to finish a build, but it’s still an interesting look at where the market is heading.

Speaking of learning from the marketplace, if you’re curious about what brands and models of hard drives hold up best in the long run, you could do worse than to look over real-world results from a known torturer of hard drives. Cloud storage concern Backblaze has published their analysis of the reliability of the over 175,000 drives they have installed in their data centers, and there’s a ton of data to pick through. The overall reliability of these drives, which are thrashing about almost endlessly, is pretty impressive: the annualized failure rate of the whole fleet is only 0.85%. They’ve also got an interesting comparison of HDDs and SSDs; Backblaze only uses solid-state disks for boot drives and for logging and such, so they don’t get quite the same level of thrash as drives containing customer data. But the annualized failure rate of boot SDDs is much lower than that of HDDs used in the same role. They slice and dice their data in a lot of fun and revealing ways, including by specific brand and model of drive, so check it out if you’re looking to buy soon.

And finally, you know that throbbing feeling you get in your head when you’re having one of those days? Well, it turns out that whether you can feel it or not, you’re having one of those days every day. Using a new technique called “3D Amplified Magnetic Resonance Imaging”, or 3D aMRI, researchers have made cool new videos that show the brain pulsating in time to the blood flowing through it. The motion is exaggerated by the imaging process, which is good because it sure looks like the brain swells enough with each pulse to crack your skull open, a feeling which every migraine sufferer can relate to. This reminds us a bit of those techniques that use special algorithms to detects a person’s heartbeat from a video by looking for the slight but periodic skin changes that occurs as blood rushes into the capillaries. It’s also interesting that when we spied this item, we were sitting with crossed legs, watching our upper leg bounce slightly in time with our pulse.

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Portable MRI Machine Comes To The Patient

To say that the process of installing a magnetic resonance imager in a hospital is a complex task is a serious understatement. Once the approval of regulators is obtained, a process that could take years, architects and engineers have to figure out where the massive machine can be installed. An MRI suite requires a sizable electrical service to be installed, reinforced floors to handle the massive weight of the magnet, and special shielding in the walls and ceiling. And once the millions have been spent and the whole thing is up and running, there are ongoing safety concerns when working around a gigantic magnet that can suck ferromagnetic objects into it at any time.

MRI studies can reveal details of diseases and injuries that no other imaging modality can match, which justifies the massive capital investments hospitals make to obtain them. But what if MRI scanners could be miniaturized? Is there something inherent in the technology that makes them so massive and so expensive that many institutions are priced out of the market? Or has technology advanced far enough that a truly portable MRI?

It turns out that yes, an inexpensive MRI scanner is not only possible, but can be made portable enough to wheel into a patient care room. It’s not without compromise, but such a device could make a huge impact on diagnostic medicine and extend MRI technologies into places far beyond the traditional hospital setting.

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Musical Mod Lets MRI Scanner Soothe The Frazzled Patient

Hackers love to make music with things that aren’t normally considered musical instruments. We’ve all seen floppy drive orchestras, and the musical abilities of a Tesla coil can be ear-shatteringly impressive. Those are all just for fun, though. It would be nice if there were practical applications for making music from normally non-musical devices.

Thanks to a group of engineers at Case Western Reserve University in Cleveland, there is now: a magnetic resonance imaging machine that plays soothing music. And we don’t mean music piped into the MRI suite to distract patients from the notoriously noisy exam. The music is actually being played through the gradient coils of the MRI scanner. We covered the inner working of MRI scanners before and discussed why they’re so darn noisy. The noise basically amounts to Lorenz forces mechanically vibrating the gradient coils in the audio frequency range as the machine shapes the powerful magnetic field around the patient’s body. To turn these ear-hammering noises into music, the researchers converted an MP3 of [Yo Yo Ma] playing [Bach]’s “Cello Suite No. 1” into encoding data for the gradient coils. A low-pass filter keeps anything past 4 kHz from getting to the gradient coils, but that works fine for the cello. The video below shows the remarkable fidelity that the coils are capable of reproducing, but the most amazing fact is that the musical modification actually produces diagnostically useful scans.

Our tastes don’t generally run to classical music, but having suffered through more than one head-banging scan, a half-hour of cello music would be a more than welcome change. Here’s hoping the technique gets further refined.

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[Ben Krasnow] Gasses MEMS Chips, For Science

Why in the world does helium kill iPhones and other members of the Apple ecosystem? Enquiring minds want to know, and [Ben Krasnow] has obliged with an investigation of the culprit: the MEMS oscillator. (YouTube, embedded below.)

When we first heard about this, courtesy in part via a Hackaday post on MRI-killed iPhones, we couldn’t imagine how poisoning a micro-electromechanical system (MEMS) part could kill a phone. We’d always associated MEMS with accelerometers and gyros, important sensors in the smartphone suite, but hardly essential. It turns out there’s another MEMS component in many Apple products: an SiT 1532 oscillator, a tiny replacement for quartz crystal oscillators.

[Ben] got a few from DigiKey and put them through some tests in a DIY gas chamber. He found that a partial pressure of helium as low as 2 kPa, or just 2% of atmospheric pressure, can kill the oscillator. To understand why, and because [Ben] has a scanning electron microscope, he lapped down some spare MEMS oscillators to expose their intricate innards. His SEM images are stunning but perplexing, raising questions about how such things could be made which he also addresses.

The bottom line: helium poisons MEMS oscillators in low enough concentrations that the original MRI story is plausible. As a bonus, we now understand MEMS devices a bit better, and have one more reason never to own an iPhone.

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Towards Open Biomedical Imaging

We live in a world where anyone can build a CT machine. Yes, anyone. It’s made of laser-cut plywood and it looks like a Stargate. Anyone can build an MRI machine. Of course, these machines aren’t really good enough for medical diagnosis, or good enough to image anything that’s alive for that matter. This project for the Hackaday Prize is something else, though. It’s biomedical imaging put into a package that is just good enough to image your lungs while they’re still in your body.

The idea behind Spectra is to attach two electrodes to the body (a chest cavity, your gut, or a simulator that’s basically a towel wrapped around the inside of a beaker). One of these electrodes emits an AC signal, and the second electrode measures the impedance and phase. Next, move the electrodes and measure again. Do this a few times, and you’ll be able to perform a tomographic reconstruction of the inside of a chest cavity (or beaker simulator).

Hardware-wise, Spectra uses more than two electrodes, thirty-two on the biggest version built so far. All of these electrodes are hooked up to a PCB that’s just under 2″ square, and everything is measured with 16-bit resolution at a 160 kSPS sample rate. To image something, each electrode sends out an AC current. Different tissues have different resistances, and the path taken through the body will have different outputs. After doing this through many electrodes, you can use the usual tomographic techniques to ‘see’ inside the body.

This is a remarkably inexpensive way to image the interior of the human body. No, it doesn’t have the same resolution as an MRI, but then again you don’t need superconducting electromagnets either. We’re really excited to see where this project will go, and we’re looking forward to the inevitable project updates.

An MRI-Safe 3D Printed Pneumatic Stepper Motor

You will no doubt have seen those videos where MRI machines suck up all sorts of metallic objects with hilariously disastrous results. The magnetic field in one of these machines can easily pull in metal objects from across the room, exerting a force of several hundred pounds on any ferrous object unlucky enough to wander too close. As you can probably imagine, designing mechanical devices that can operate in such an intense magnetic field is exceptionally difficult.

But this fully 3D printed pneumatic stepper motor designed by [Foad Sojoodi Farimani] might one day change that. The PneuAct, which he presented at the recent International Conference on Robotics and Automation (ICRA) in Brisbane, Australia, manages to run at up to 850 RPM with full position control using bursts of air rather than electronic pulses. Made entirely of plastic and without any electronic components, the PneuAct can not only operate in intense magnetic fields but also areas with flammable gases where sparks could potentially cause an explosion.

We often say that a design is “fully” 3D printable, even though it might require screws or other bits of hardware. But in the case of the PneuAct, it’s truly all printed. It has to be, or else the whole thing would be ripped apart when it got to close to the MRI machine. Each and every piece of the motor is printed in ABS, and can be used without any additional machining or cleanup. No lubrication is required, and [Foad] mentions that the whole thing is so cheap that it can be disposable. Which is a huge advantage in medical environments where contamination could be a concern.

Design-wise the PneuAct is essentially an expanded version of the 3D printed air motors we’ve seen previously, but it would be fair to say that none has ever been studied so closely before.

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Reverse-Engineering Brains, One Neuron At A Time

Most posts here are electrical or mechanical, with a few scattered hacks from other fields. Those who also keep up with advances in biomedical research may have noticed certain areas are starting to parallel the electronics we know. [Dr. Rajib Shubert] is in one such field, and picked up on the commonality as well. He thought it’d be interesting to bridge the two worlds by explaining his research using analogies familiar to the Hackaday audience. (Video also embedded below.)

He laid the foundation with a little background, establishing that we’ve been able to see individual static neurons for a while via microscope slides and such, and we’ve been able to see activity of the whole living brain via functional MRI. These methods gradually improved our understanding of neurons, and advances within the past few years have reached an intersection of those two points: [Dr. Shubert] and colleagues now have tools to peer inside a functional brain, teasing out how it works one neuron at a time.

[Dr. Shubert]’s talk makes analogies to electronics hardware, but we can also make a software analogy treating the brain as a highly optimized (and/or obfuscated) piece of code. Virus stamping a single cell under this analogy is like isolating a single function, seeing who calls it, and who it calls. This pairs well with optogenetics techniques, which can be seen as like modifying a function to see how it affects results in real time. It certainly puts a different meaning on the phrase “working with live code”!

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