Slashdot Mirror
Flying Robots Made From Cellophane?
Roland Piquepaille writes "Researchers have discovered that ordinary cellulose is a piezoelectric and smart material that can flap when exposed to an electric field. ScienceNOW reports that electricity can give life to cellophane. When you put a very thin layer of gold on each side of cellophane, and that you apply electric current to the gold layers, one positive, one negative, the cellophane curved toward the positive side. If you switch the voltage fast enough, the cellophane starts to act as a wing. So it should be possible to use it to build lightweight flying robots carrying cameras, microphones or sensors for surveillance missions. Read more for additional references and pictures about this electroactive paper (EAPap)."
So today on Slashdot we've got flying robots and cars that drive themselves, but nowhere do I see the flying car that Popular Mechanics has been telling us is only five years away for the last several decades.
Cellophane isn't piezoelectric. It is just very amenable to carrying a lot of static charge, which is what is being employed in this case.
I am becoming gerund, destroyer of verbs.
....our new paper thin flying overlords.
As per usual; the powersource ?
Religion is what happens when nature strikes and groupthink goes wrong.
Could this be used for speakers? Aren't there some speakers that use a membrane instead of the normal speaker cone?
Send email from the afterlife! Write your e-will at Dead Man's Switch.
And given that they have a casting cost of 0, we'll have a ton of them.
The first time I read that, I read it as "Flying Robots Made From Cell Phones". That would be seriously scary, getting attacked by a bunch of flying cell phones could ruin your whole day.
It's good to use your head, but not as a battering ram.
Wow, featherweight sub-gram flying things! I wonder if they can lift the the 23 kilo car battery needed to power it? Still, way cool.
I am going to wait for the one that can carry the HD camera though, is it worth investing in SD parts at this point in time?
-Charlie
Wouldn't the wingspans needed to support even a light payload with flapping wings be too large for the cellophane wing to even support it's own weight?
Ok. We have some gold-plated cellophane. How is that a "flying robot"? Not meaning to troll, but isn't that a bit of a leap? I understand how, possibly, that would be useful. But there are other things to a wing than just flapping. There's aerodynamics, and flapping, and such. Aren't there more efficent means of flight than cellophane wings, even if they were feasible? No, I havn't RTFA but I'd be willing to guess that nobody has actually built one of these wings.
What is the reason for one of these things? Are they more energy efficent?
The only thing I can think that these would actually hold up (if they could do anything) would be something smaller than a bumblebee. What can a fly-sized robot do? And, in 50 years when we have useful ones, won't we have another means of flight?
I have developed a truly marvelous proof of this comment, which this signature is too narrow to contain.
Are not piezoelectric and do not use cellophane.
They work by putting an electrostatic charge on a mylar sheet, which is close to what the GP poster said.
And what you call cellophane wrap is not made of cellophane (or cellulose). It's regular petrochemical plastic based.
Cellophane (both wrap and tape) hasn't been in households for a long time now, at least 30 years.
http://lkml.org/lkml/2005/8/20/95
...cause quite a flap.
Cloned foods give the statement "We had that last week!" a whole new meaning.
It's Roland the Plogger again, writing about something called EA-Pap. That's so Roland.
Piezoelectric films are not new. PVDF films like Kynar are peizoelectric, and they've been used for hydrophones, speakers, and pressure sensors for years.
Actually, the big recent advance in pizeoelectric actuators is subminiature rotary motors like this Squiggle device. Now, very tiny motors can be made for applications like camera lens autofocus. The initial application looks to be cramming autofocus machinery into cell phone cameras.
>An airplane wing does not produce lift because it is angled downwards,
/ q0015b.shtml
f t_and_drift.htm
>it generates lift almost purely because of its shape.
Actually, you are quite mistaken.
I am an aerospace engineer. I have a BS in Aerospace Engineering and 16 years experience conducting flight test on a dozen aircraft ranging from Cessna- to 707-sized. I have also published papers on the process.
A wing produces lift according to this basic equation:
Lift = 0.5 * Coefficient of Lift * Density of the Air * Wing Area * Airspeed squared
This includes a few approximations since I can't type various symbols in plain test. You can look at the properly written equation here: http://www.aerospaceweb.org/question/aerodynamics
Coefficient of lift, part of that equation, is itself a direct function of Angle of Attack - the angle at which the chord of the wing meets the air. ("Chord" is defined, roughly, as a line between the front and back edges of the wing.)
The wing curvature, or camber as you correctly call it, is a contributor, but far from the only one, to the equation of lift coefficient versus angle of attack. A flat, or non-cambered, wing will produce zero lift at zero angle of attack. Increase the camber, up to a point, and you increase the lift at zero angle of attack. Or you can increase the angle of attack at zero camber to increase the lift. For that matter, you can spin a cylinder in an airflow and generate lift - zero camber, zero angle of attack (it's a circular cross section, so there's no angle!). So there are MANY factors influencing lift - any combination of these is possible; you just need to select which ones are most beneficial to a given design requirement.
As a matter of fact, the first documented equation to describe lift included only angle of attack and speed. It wasn't until decades later that careful observation of bird wing structure revealed the importance of camber. There's an intriguing story here about the Wright brothers and their development of the theory of lifting bodies, and how they overturned decades of established wisdom: http://www.first-to-fly.com/Adventure/Workshop/li
In a very simple and small wing (like most insects, which obviously can fly), it's almost ALL angle of attack, and no camber. Consider a dragonfly. The wings are perfectly flat. And the creature must create not only lift but also forward thrust with those wings. Quick and repetitive motions (as mentioned in this article) are perfect for this requirement. Camber has nothing to do with it, and camber, in fact, would impede the dragonfly, because the wing must also be capable of generating lift while moving backwards - and any effective camber is usually detrimental while going backwards. Finally, in the case of insects, the qualities of air are different at small scales (the so-called Reynolds Number effects) and lift operates somewhat differently from in large airplanes.
Consider also a dime-store balsa wood glider. In its cheapest form, the wing is completely flat. Yet it flies just fine. Or consider the paper airplane. It flies just fine with a slab of paper for a wing.
In short, you can take this article at face value regarding simple wings and lift. There are other wishful comments, but the aerodynamic description is quite fine.
--Brandon / Split Infinity Music