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Comment by bluetwo | Hacker News Reader

Cool idea but it can't possibly be safe to spin infected blood on a device such as this.

I don't know why it would be any more dangerous than a typical centrifuge. Samples are in a vial, and that vial is what is responsible for containing the sample while you spin the samples. Having been around conventional centrifuges that have been destroyed due to improper balance, I assure you that any way you can imagine infected blood being distributed by the paper model would be 10x worse with a normal centrifuge. At least with this method, the motor has a brain and will stop as soon as things start going south.

A lot of centrifuges are just controlled by a potentiometer. You couldn't pay me enough to to get close enough to turn one of those off while it is self-destructing. The amount of energy involved is enormous. Someone blew up a (rather inexpensive) medical centrifuge at my school when they balanced some non-water liquid with water. It was a huge mess. Centrifuges are basically designed to contain the most dangerous bits when they explode. They don't keep your error from spraying all over the room.

You are comparing when things go wrong with a centrifuge to every single use of this device. How would you contain the microscopic airborne particles?

>> Samples are in a vial

In re-reading my comment, I realized it isn't clear that normal centrifuges use vials to contain the sample as well.

Regardless, having spent thousands of hours in a lab, I think the traditional lab centrifuge is probably more dangerous.

I suspect for most diseases break the centrifuge (and vial) would not drastically raise the risk for the bystanders -- we have plenty of microscopic airborne particles with all sorts of bacteria around us already, especially in cities. And I think malaria would not be contagious at all this way.

It could be different for specifically engineered bio-weapon, but IMO the benefits of better detection far outweigh the risks, especially in the developing world.

Eh, both of you are right.

Yes, a full-blown centrifuge could be made safer (put a shield around it, yadda-yadda). But if the paper device is made safe enough, I don't see why it should not be used when there are no better options. And it appears that it could be made safe enough.

True story: The company I work for make some pretty hefty winches for offshore use. Think ROVs, subsea oil installation, salvage &c.

Years ago, one of our customers had ignored a number of increasingly strongly worded safety bulletins, the end result being that just as they were going to hoist their megabuck ROV back aboard, the winch motors stopped and - for an encore - it turned out they hadn't tested the brake in ages, either - so it was incapable of halting the winch.

Now, the ROV itself would very gently drift towards the bottom. Too bad the umbilical cord between it and the winch weighs several kilos per meter.

The initial yank as the ROV freefell to the sea surface and the inertia of the drum ensured enough cable was paid out for the weight of it to keep the winch going faster and faster. Basically you had a very large loop with the ROV at one end, the winch at another.

This drum was designed for some 30rpm or so at the maximum design speed. Based on a video from a surveillance camera, we found the drum did close to 200 rpm as a few tons of cable pulled at it.

At this point, thinking the brakes must have been stuck disengaged, some brave soul with poor judgment and an axe appears, chopping off the hydraulic hoses to the brake. Lucky for him, the brakes weren't able to stop the thing anyway - otherwise, he would have found out if the designers had made the frame sturdy enough to remain intact during the retardation which would have followed.

This brave soul then realises that the game will be up in a few moments' time anyway - when the drum runs out of cable, at which point being anywhere near the winch will be very bad for you.

He runs like mad, disappear from the frame and then, seconds later - kerrrr-whaaang as the umbilical is ripped from the drum, the drum is torn from the frame and it all disappears into the large, blue waste disposal.

That led to a quite interesting post mortem. They found assorted bits and pieces of the winch all over the deck.

Somewhat off topic, but disintegrating centrifuges got me started...

There are some videos on youtube of anchors dropping too fast:

https://www.youtube.com/watch?v=hvrgFPcPXfo

https://www.youtube.com/watch?v=RAcfaMDcY68

https://www.youtube.com/watch?v=b7pRfix_sNg

It's pretty scary.

(Someone else posted one of these links originally, I'll try to find it)

I work at a company that makes ROVs, and your story sounds very similar to a story I heard a few years back. I wonder if it was one of ours that got dropped.

Depends. If your employer happens to be named Schilling, we may need to get together for a beer. :)

That story makes exploding $100k centrifuges sound like a bargin.

Read the paper - it describes three safety features of the device which are explicitly designed to contain infected blood.

Why not? The videos show the devices being operated with one handle fixed against a wall/door. In that situation, nothing flying off the disc will go towards the operator. You could also enclosing it in a box or operate it inside a hole in the ground.

"nothing flying off the disk will go towards the operator". What about other people? As you say, you can enclose it in a box, but that means making a glovebox, which increases cost significantly.

> What about other people?

The device only requires a single person to be present.

> that means making a glovebox, which increases cost significantly.

You don't need a glovebox, you just need a way to pull on one of the strings from outside the box.

"Single person to be present"- so you can afford a dedicated room to spin samples? That increases cost.

You need a glovebox so you can load your samples... although technically I guess that outboarding the strings works too.

Or just a big cardboard box and a glove+sleeve.

The cost of the system goes up with the centripital force, which goes up with the RPMs.

At the low end and low RPMs all you need is some string and some paper. At moderate RPMs you could use (scavenge, even) off the shelf components to achieve your aims. For instance, how fast could you spin a bicycle wheel under human power before the system becomes dangerous?

From memory, an unbalanced bicycle wheel doesn't become noticeable to the rider (whose weight is holding the wheel down) until somewhere around 20 mph. A fair quality wheel doesn't get scary until about 25, but if you want to run down a valley or mountain road with your hands off the brakes (35+), you need the sort of quality that gives the lay person sticker shock.

Now, a wheel mounted to a block of wood doesn't have 150 lbs of anchoring it in place, but that's not the only device with bearings that can be located.

Hell, a washer with a broken water pump could work, if you knew how to rig it.

Plastic bag around the disc?

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