Carbon Nanotube with Vanadium Pentoxide Actuators

Wild guess here,

But I presume that the structure is much the same as a Chrystal. The bonds are very strong and aligned in a perfect pattern. With electricity applied, it can travel in only one axis of the pattern and the result is physical vibrations, much the same as a how a Quartz Chrystal operates.

If I understand the voltage is not changed. Quarz only deforms under applied constant voltage does not vibrate. Am I wrong?

The crystal does vibrate under constant voltage

For reference look up piezoelectricity. It happens in crystals ,some ceramics, and polymers.

Piezo-effect is either the electric load generated by a mechanical deformation of the Cristal or the deformation (mechanical) of the Cristal by an electric load applied by a voltage. If the voltage is constant the load does not change and the deformation does not change. To obtain a vibration the load has to be variable. Or in an accelerometer the acceleration has to be modified in order to obtain a variable signal. This is by the way one of the problems with piezo-sensors they are excellent when the deformation is high frequency and poor at low frequencies or under static conditions because of the electric load decay.

Correct, We are talking about the "deformation (mechanical) of the Cristal by an electric load applied by a voltage"

" If the voltage is constant the load does not change and the deformation does not change." Any noise in a DC Power supply is enough to start vibrations - even the initial spike of applying power. Simply put, the chrystals want to vibrate at their resonant frequencies.

Hi,

any piezo material will vibrate only if driven by an alternating voltage and current.

Most often the piezo is used as a mechanical oscillator in resonance driven by an electronic circuit that is measuring its amplitude and generating a force that is maximum at maximum velocity or 90degreese to amplitude!

Oscillation by DC excitation? will require the amplifyer and feedback mechanism inside the oscillator.

This is existing in some microwave devices and can be realised with the distributed feedback in RF devices if the dimensions are sufficiently large (quarter wavelength or bigger) and it is necessary that some nonlinear device is existing: a switch, a saturating element or similar.

RHABE

Correct.

A point of note. All electrical ccts create noise. Any resistances create noise. Unshielded wires pick up noise. The resistance of the wire creates noise. The electrical ccts creating the dc power creates noise. Even the filters that reduce the noise create noise. The minute ripple left over after rectification and filtering is enough to excite a Chrystal, and yes, to make it useful we always amplify and feedback the induced oscillations.

It is a special situation since if you take a dc source as a bettery and connect the 2 conductors to a cristal it will only deform and not vibrate. It vibrates ONLY when a variable curent which ever is the source is applied. In fact you only confirmed what i wrote since you introduce "noise" as a source of variable voltage/curent.

I am not disagreeing with you.

I am only saying that even the resistance of the electrodes or any electrical noise picked up from the environment (cell phone, lights, fridge compressor) can cause oscillations in a crystal to start.

The symptoms of the changing polarity in the polymer of the original question looks allot like oscillations found in crystals, ceramics and polymers.

English is not my 1st language but as far as I can understand the original text it mentions that there is NO voltage/polarity change.

The Cristal works as capacitor so that after a time if it was connected to a source of dc with a constant voltage the load will reach a value which stays constant. If the circuit has losses due to not infinite isolation a leak current can appear but the system will come to a steady state situation, a dynamic equilibrium, an the Cristal will NOT vibrate any more. In a circuit noise arrows when a current flows, if no current flows any more there is no noise. In such a situation will the Cristal still vibrate?

To make a Cristal vibrate the applied LOAD ( in Coulomb) should change in time.

An electromagnetic field (cell phone, light) has usually an influence on a "coil', as far as i know not on a capacitor, but may be i am wrong. A fridge will generate mechanical vibrations and will change the load since a mechanical change will modify the electric load.

What we discussed about was only the piezo effect not that in the environment there are different sources which could lead to a Cristal vibration.

The problem with engineering is that there is a need for clear concepts and clear explanations and every word has its value and has to be used the right way.

"as far as i know not on a capacitor"

Electronic noise will be picked up by everything, even you

The problem is that most of these explanations are working in the "ideal" mode and not exact. There is no perfect DC source. All the noise generators mentioned are capable of keeping an oscillator going. A single piece of wire in "exact measurement" actuality has some inductance (if there is a bend), capacitance and resistance, and if not shielded will pick up tremendous amount of noise. A single fluorescent light can generate noise with an amplitude of 10 to 12 volts at the operating frequency (60 Hz) in an unshielded wire. In fact the way they used to stimulate a crystal was to have a 'noise generator in the cct'. This was simply a noisy resistor. In 30 years of working with electronics, only once have I ever come across a quartz crystal that did not keep vibrating with a dc source, and all it took to get it working again was to physically hit it.

When an oscillator is stimulated with a single noise spike it will resonate many times at its own frequency much the way a church bell will vibrate . The amplitude will slowly decrease (entropy) and stop unless stimulated again. With constant noise input, the oscillator never stops ringing.

Induced voltages are proportional -as far as i know- to the field intensity and to the LENGTH of the receiver and to the resistance of the receiver. Of course it is, no doubt, possible if the wire is long enough and placed quite near to the generator and open ended to obtain high voltages. I never said that Cristal will never oscillate if a VARAIABLE voltage is applied. The only thing I said and continue to affirm is that ( if you want under ideal conditions) piezoelectric phenomenon is : a voltage generates a deformation and a deformation generates an electric load. If the deformation is made by a constant load the generated electric load will reach a peak and decay slowly depending on the electrical isolation of the Cristal charged surfaces.

I did not work in electronics for 30 years but i used piezo - quartz pressure sensors for many years and i also could get some experience. According to your arguments you used quartz vibrators for frequency references so you were confronted with oscillating systems. And those are of course very sensitive to noise.

The amplitude will decrease due to losses either mechanical (but in a cristal they are not big) or or due to losses of charge. isolation being not perfect.

With respect to the influence on the "capacitor" i would like to make following comment. The voltage of a capacitor depends on the charge i.e. on the number of elementary charges present in it. The variations depend on the relative number of charges coming in or going out. Of course electrons will change the voltage but depending on how many they are and how big was the initial charge. Now a em field will move charges either + or -. To obtain an effect on a capacitor it should be connected to a "receiver". If the 2 sides of the cristal which form a capacitor are connected by a "receiver" then the field will generate a variable voltage depending on the length of the receiver and move charges from one side to the other generating an oscillation of the cristal. But what will happen if there no receiver? and no connection?

That the 'Induced voltages are proportional to the field intensity' is correct.

The LENGTH of the receiver affects only the FREQUNCEY it will pick up. Most receivers will pick up the high frequencies and the longer the receiver will be more likely to pick up lower frequencies. (a general rule is that the receiver has to be 1/4 wavelength to pick up a transmitted signal.)

"But what will happen if there no receiver? and no connection?"

Since we are not in a vacuum, there is always a connection, even if it is only the resistance of the air. If you charge a capacitor and leave it 'disconnected' it will eventually lose its charge.

I have also worked with a few sensors, and we do everything we can to reduce spurious noise so as to not give false readings. He is not working with a man made cct, but with raw materials in an open environment.

All this electronics aside, do you agree that the symptoms in the original post shows signs that the polymer may have some crystal like properties, that some polymers exhibit? If not, do you have any other suggestions?

In a crystal electricity works different then in say a normal wire. In a wire you would think as the electricity flowing in an electron cloud through the material (between and outside the atoms.) There is some combining with the material and releases causing heat light, etc. ,however, the majority of excess electron flow like a gas.

In a crystal, think about three dimensional network structure like Newtons cradle . The electron cloud cannot pass through the structure because the atomic bonds and shape are too strong and close together they always want to go back to their original shape. For electrons to pass through the material, an electron must join with the material and force an electron out. This will take a tremendous force. Small potential differences will not do this.

One electron added deforms the material. The combined atomic bonds of the whole structure forces the material back to its original shape and ejects an excess electron. (spring action). Where the electron is ejected does not depend on where it originated,(potential difference) but on the pattern of the structure. Usually there is one axis where the structure is weakest and electrons are passed easiest. This depends wholly on the chemical structure. If the bonds are strong enough, they may even spit the excess electron back to where it came from. Only when the force is overwhelming and stronger then the atomic structure will it allow electricity to pass. (much the same as the breakdown or tunnelling of a capacitor)

Here is a good comparison:

Think of the DC electricity like the constant flow of water from a hose, and the strong atomic structure of a crystal is like fighting gravity on a steep hill.

If you try to hose water up the hill, in small quantities gravity keeps pushing back. Even though the hose is at a constant pressure (DC) the path of the water keeps changing and gravity wins. The water and electrons flow in every direction, and comes back in waves, against the original flow. It takes a tremendous volume and pressure to overcome the effects of gravity.

The same comparison in a wire. In this case the atomic bonds are weak and the ground is almost completely flat. In this case most of the water will go where you want in a smooth constant direction and some resistance from the friction of the ground.