Harvard Professor Creates Paper Accelerometer

SuperSlacker64 writes "In an age where just about everything starts going digital, it's refreshing to see someone going back to our roots: paper. Well, sort of. Researchers at Harvard have created a cheap, dime-sized, paper-based accelerometer that they believe could be used in various ways, such as inexpensive medical testing. The device works because a carbon bridge stretches and changes resistivity as the device is accelerated." When they say "cheap," they mean it; the cost per device is estimated to be about four cents.

Comments

Accuracy?

[Ethereal.Visage]

'Twould be very interesting to see just how accurate these devices are. While they are undoubtably cheap and easy to manufacture, many applications require high-precision measurements, not just good approximations. Nevertheless, bravo.

Re:Accuracy?

[shaitand]

I hath sinned. I read the article. *hangs head in shame* The paper counterparts are far less sensitive. Silicon sensors give about 80 micronewtons while the paper give 120 un.

Re:Accuracy?

[BJ_Covert_Action]

On the other hand, if they can be mass produced and marketed, they could be great for hardware hackers and hobbyists.

Re:Accuracy?

[Nyeerrmm]

80 vs. 120 micronewtons isn't too bad. If by 'sensitivity' you mean the expected standard deviation for measurement noise, and assuming such noise is roughly gaussian, then you can almost achieve the precision of a silicon sensor by using two paper sensors and averaging the results (120/sqrt(2) = 84.9).

Throw together 25 of them (for a total cost of $1.00) and you can achieve 24 micronewton 1-sigma precision.

Re:Accuracy?

[MobileTatsu-NJG]

It says for use in medical testing equipment where I'm pretty sure one would want precision, no?

Not every test, especially when aiming for low-cost, needs to reach Starfleet standards.

Re:Accuracy?

[mangu]

many applications require high-precision measurements, not just good approximations

And your point is...?

For any application that needs high-precision measurements, there are many others where lower precision would do fine, if only it wouldn't cost so much.

Re:Accuracy?

[JonySuede]

not necessarily, for medical application you need accuracy, 120 un vs 80 un might be enough if the result are accurate. http://en.wikipedia.org/wiki/Accuracy_and_precision

My world is topsy-turvy

[BitHive]

I thought professors were people who couldn't hack it in the real world, but it turns out academia is behind most innovation in one way or another? Color me retarded.

Re:My world is topsy-turvy

[Anonymous Coward]

>Whoever started the "professors are people who can't hack it" thing was not only wrong but being really vicious against some very competent, creative, and inventive people.

Or maybe he was just looking at the dregs who inhabit most college humanities departments.

Re:My world is topsy-turvy

[dragonxtc]

A majority of academics are in the pursuit of knowledge and furthering their respective fields. When you are working for a company a majority of the time you are doing something that does not further the field of science and knowledge.

Re:My world is topsy-turvy

[Facegarden]

A majority of academics are in the pursuit of knowledge and furthering their respective fields. When you are working for a company a majority of the time you are doing something that does not further the field of science and knowledge.

Agreed. Even if you *were* doing useful research, you likely would not be allowed to share it, ever. You have patents and copyright terms and by the end of them its not like companies just open up their records. They'd stay hidden forever. Patents give some insight but not all.

-Taylor

Re:My world is topsy-turvy

[j00r0m4nc3r]

All that academic shit looks good on paper, but.... oh.

from the trees-aren't-off-the-hook-yet dept.

[RailGunner]

If only there were a way to take a seed from a tree, put it in the ground, and make more of them. You could even envision some people producing tree farms.

Of course!

[Thelasko]

Everything works on paper!

Re:cheap huh?What?

[LandDolphin]

The insurance company worked out a "bulk" deal with the hospital and does not have to pay "full price".

Missing parts...

[Moof123]

Most accelerometers are not just a sense element.

The Analog devices ones from a few years back included an onboard reference (to allow single supply operation), and an on board buffer amplifier with externally settable gain (i.e. integrated op-amp). The 4 cent sensor still requires precision op-amps, nulling trim pots, etc to get a usable sensor. Don't forget packaging to protect the element from kinks, moisture, etc.

BUT, the most important thing about the accelerometers from Analog I used was they were laser trimmed for 0G, and used a very cool sense mechanism. The sensor was a micro-machined silicon mass on springs with a capacitive force/sense system that detects a perturbation of position by using a 1 MHz AC pump signal with a capacitive bridge and synchronous demodulation feedback. The mass is forced to be stationary by applying a DC electrical voltage on the capacitive sense plates, imparting a force 100% proportional to the applied DC voltage (i.e. purely LINEAR voltage to force relationship).

So what? Their system keeps the mass centered, thus making micro-machined springs that hold the mass irrelevant to the output voltage. In other words the NON-LINEARITY of crap springs is servoed out, and the output voltage is not an open loop measurement with gain, but a true measure of the force being applied to the tiny little mass by the acceleration trying to be measured.

Paper as a spring is not going to be repeatable from batch to batch, is subject to moisture, subject to fatigue, hysteresis, etc. Mad props for new uses of paper, but practical as a replacement for the devices it mocks it is not.

Re:Missing parts...

[pclminion]

The terms AC and DC have two subtly different meanings. In one of them, AC is distinguished from DC because AC oscillates and DC does not. In the other sense, AC differs from DC by virtue of the direction of current flow -- the current only "alternates" if it actually comes to a stop and flows in the opposite direction. It's possible to have oscillation without the current changing direction, for instance a 1 MHz oscillation that ranges from 0 volt to 1 volt. The current always moves in one direction, though its amplitude varies.

So yes, indicating AC is not redundant. It means the voltage passes through 0.

Re:Missing parts...

[LanMan04]

BUT, the most important thing about the accelerometers from Analog I used was they were laser trimmed for 0G, and used a very cool sense mechanism. The sensor was a micro-machined silicon mass on springs with a capacitive force/sense system that detects a perturbation of position by using a 1 MHz AC pump signal with a capacitive bridge and synchronous demodulation feedback.

I assume you then reverse the polarity and feed it back through the deflector dish?

undo

[fahlesr1]

Commenting to undo unintentional mod.