3D Printing Bone

What do you print with your 3D printer? Key chains? More printer parts (our favorite)? Enclosures for PC boards? At Johns Hopkins, they want to print bones. Not Halloween skeletons, either. Actual bones for use in bodies.

According to Johns Hopkins, over 200,000 people a year need head or face bone replacements due to birth defects, trauma, or surgery. Traditionally, surgeons cut part of your leg bone that doesn’t bear much weight out and shape it to meet the patient’s need. However, this has a few problems. The cut in the leg isn’t pleasant. In addition, it is difficult to create subtle curved shapes for a face out of a relatively straight leg bone.

This is an obvious application for 3D printing if you could find a suitable material to produce faux bones. The FDA allows polycaprolactate (PCL) plastic for other clinical uses and it is attractive because it has a relatively low melting point. That’s important because mixing in biological additives is difficult to do at high temperatures.

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Running a Hackerspace is Hard: Egypt Edition

It’s no secret that it’s difficult to run a hackerspace. Different personalities, different material requirements, and often constrained spaces can require continual negotiation. But if you think that having the metalworking types getting their shavings on your electronics bench is a problem, try having your entire hackerspace demolished on short notice.

The situation in Cairo is far from normal at the moment. The building that Cairo Hackerspace had recently moved to was raided, closed for two months, and then re-opened under strict surveillance in February.

All was well until a part of the building unexpectedly collapsed. Then they got a demolition order, followed by postponement, followed by armed police entering anyway and breaking stuff, followed by a further declaration of the building as safe, and now a heritage site. And all of this over a week’s time. While some of the art studios in the Townhouse were saved, the Cairo Hackerspace’s space is gone.

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The good news? Nobody got hurt in all of this, and the Cairo Hackerspace crew were able to get their gear out after the initial demolition notice. They’ve been working on a mobile hackerspace-in-a-van approach lately, so hopefully they’ll be able to keep on hacking.

So when you’re bickering over who didn’t clean up the hackspace’s coffee machine, or the proper location of your favorite soldering iron, think kindly about the Cairo crew and get back to doing what you do best — projects.

How about you? What hackerspace tales do you have? Contact us through the tips line — we’d love to hear.

Single Photon Source for Quantum Computing and Experimentation

One challenge to building optical computing devices and some quantum computers is finding a source of single photons. There are a lot of different techniques, but many of them aren’t very practical, requiring lots of space and cryogenic cooling. Recently, researchers at the Hebrew University of Jerusalem developed a scalable photon source on a semiconductor die.

Using nanocrystals of semiconductor material, the new technique emits single photons, and in a predictable direction. The nanocrystals combine with circular nanoantennas made of metal and dielectric produced with conventional fabrication technology. The nanoantennas are concentric circles resembling a bullseye and is used to ensure that the photons travel the correct direction with little or no angular deviation.

A single IC could contain many photon sources and they operate at room temperature. We’ve talked about quantum tricks with photons before. Quantum mechanics is another popular topic.

Can you hear SamSat-218D?

Students of the Samara State Aerospace University are having trouble getting a signal from their satellite, SamSat-218D. They are now reaching out to the radio amateur community, inviting everybody with sufficiently sensitive UHF VHF band (144 MHz) equipment to help by listening to SamSat-218D. The satellite was entirely built by students and went into space on board of a Soyuz-2 rocket on April 26, 2016. This is their call (translated by Google):

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Infrared Detector Selects Over a Wide Range

You can classify infrared light into three broad ranges: short wave, medium wave, and long wave. Traditionally, sensors concentrate on one or two bands, and each band has its own purpose. Short wave IR, for example, produces images similar to visible light images. Long wave is good for thermal imaging.

Researchers have announced a new detector that, by adjusting a bias, can detect all three bands using a simple approach that stacks different absorption layers over a semiconductor substrate. The device only requires two terminals and is very efficient, although the efficiency varies based on the band.

We’ve covered infrared sensing before. We’ve even seen DSLRs hacked into IR sensors. This new research might be a bit much to duplicate in your garage. After all, it requires tellurium doped gallium antimonide substrates and sophisticated processing equipment. However, this research will probably lead to practical devices that will find their way into projects before too long.

I Am Satoshi Nakamoto

OK, you got me. I’m not. Neither is Dorian Nakamoto, pictured above, and neither is this [Craig White] guy. Or at least, his supposed proof that he is “Satoshi” doesn’t stand up to scrutiny. Indeed, you can re-create it yourself and pretend to be “Satoshi” too.

If you haven’t been following along, “Satoshi Nakamoto” is the person or group of people who invented Bitcoin, and who holds a decent fortune’s worth of the currency. He’s been exceedingly careful at keeping his identity secret. So much so, that upon hearing another “We Found Satoshi” story in the news, we actually laughed at our wife this morning. But then it was picked up by the BBC and is forthcoming in the Economist. Serious journalism.

Well, if you read the BBC piece, they note that “Security expert Dan Kaminsky said the procedure was almost ‘maliciously resistant’ to validation.” Hint: If Dan “DNSSEC” Kaminsky can’t verify a signature, there’s a good chance it’s not the real deal.

The really embarrassing part is that this [Craig White] character claimed to be Satoshi in December 2015. If he actually were Satoshi, who is probably a cryptographic genius, do you think it would take him five months to figure out a cryptographically sound way of proving his identity? Nope.

So here’s how he did it, according to [Patrick McKenzie]’s GitHub, linked above. There is a hashed secret out there that only “Satoshi” knows. Hashes are one-way functions; they produce a number that’s easy to calculate if you know the original data, but devilishly hard to work from the hash backwards to get the data out. This hashed value is public, and part of the blockchain, so we can be pretty sure that it hasn’t been altered.

[Craig] claimed to have some text from Sartre hashed with “Satoshi’s” key, and that this proves his identity. But instead of providing the hash of the Sartre text, [Craig] apparently substituted a hash from the blockchain. When this supposed Sartre hash is validated against the blockchain, of course, it works. In short, he swapped hashes, and people failed to notice.

So I’m not “Satoshi”, and neither is this guy. Who is? The mystery continues. And given how careful “Satoshi” has been so far, it’s likely to remain so for a long while. But one thing’s for sure, when “he” does choose to reveal himself, it won’t be difficult to verify. After all “Satoshi” knows “Satoshi’s” password.

Image via the BBC, of another guy who isn’t “Satoshi”.

(Late Edit: Here’s another really nice writeup, this one by [ErrataRob].)

Atmel Removes Full-Swing Crystal Oscillator

It is one of our favorite chips, and the brains behind the Arduino UNO and its clones, and it’s getting a tweak (PDF). The ATmega328 and other megaX8-series chips have undergone a subtle design change that probably won’t affect you, but will cause hours of debugging headaches if it does. So here’s your heads-up. The full-swing oscillator driver circuitry is being removed. As always, there’s good news and bad news.

The older ATmega chips had two different crystal drivers, a low-power one that worked for lower speeds, and higher-current version that would make even recalcitrant crystals with fat loading capacitors sing. This “full-swing” crystal driver was good for 16 MHz and up.

The good news about the change is that the low-power crystal driver has been improved to the point that it’ll drive 16 MHz crystals, so you probably don’t need the full-swing driver anymore unless you’re running the chip at 20 MHz (or higher, you naughty little overclocker).

This is tremendously important for Arduinos, for instance, which run a 16 MHz crystal. Can you imagine the public-relations disaster if future Arduinos just stopped working randomly? Unclear is if this is going to ruin building up a perfboard Arduino as shown in the banner image. The full-swing oscillator was so robust that people were getting away with a lot of hacky designs and sub-optimal loading capacitor choices. Will those continue to work? Time will tell.

The bad news is that if you were using the full-swing oscillator to overcome electrical noise in your environment, you’re going to need to resort to an external oscillator instead of a simple crystal. This will increase parts cost, but might be the right thing to do anyway.

Whenever anyone changes your favorite chip, there’s a predictable kerfuffle on the forums. An Atmel representative said they can get you chips with the full-swing driver with a special order code. We’re thinking that they’re not going to let us special order ten chips, though, so we’re going to have to learn to live with the change.

The ATmega328 has already gotten a makeover, and the new version has improved peripheral devices which are certainly welcome. They don’t have the full-swing oscillator onboard, so you can pick some up now and verify if this change is going to be a problem for you or not. We don’t have any of the new chips to test out just yet.

Thanks to [Ido Gendel] for tipping us off to the change in our comment section! If you have any first-hand experience with the new chips, let us know in the comments and send in a tip anytime you trip over something awesome during your Internet travels.