Capacitive Electrodes

Did you try GlobalSpec?

@SolarEagle - Thanks, but they didn't have anything. My application is a biomedical device that creates an electric field across the body.

Roger

Might start here...don't see anything in that high voltage...might be in here someplace

http://www.biomedelectrodes.com/

http://www.analog.com/static/imported-files/tech_docs/ECG-EEG-EMG_FINAL.pdf

more....

Thanks! I'll check these sites out.

Roger

The specification is incomplete. You have not mentioned physical dimensions, end application. All you state is - you need capacitive electrode. Hence difficult to suggest anything.

xyz, "around one inch in diameter and flexible, able to withstand 50V at 150KHz, with as high a dielectric constant as feasible". They are being used to create an electric field across the body, like an arm. They are placed on either side of the arm such that the electric field passes through the arm.

Roger

I think you will find what you are looking for at:http://www.greatbatchmedical.com/hittmanFeedthroughs.aspx?s=product

Thanks welderman, but I'm not trying to reduce EMI.

Roger

It sounds like a basic capacitor - two plates separated by air and a human body limb. Presumably, a voltage is applied to the plates, an electrostatic field develops between the plates.

Any flexible conductor covered by something that's flexible and can be cleaned, like plastic, should do the trick? I'm thinking coated aluminum foil. Vinyl coated aluminum siding?

What are the electrodes for? If your purpose in using the ultimate design were clearer, maybe we could help more with finding the design elements. You have done an exhaustive search and found nothing, which might mean that the conception is fundamentally absurd. What makes you think your approach would accomplish what you want better than what is presently known? Is there some advantage to using radio frequency (150 kHz) electrodes, and why 50 volts?

Are they for reading body changes (capacitively coupling energy out) or for therapy (capacitively coupling energy in)?

Evidently you are working on something new and you are reluctant to disclose the essential points of your invention, but if you had a provisional patent application on file frank discussions might be easier. http://www.uspto.gov/patents/resources/types/provapp.jsp

Maybe you could use a radio frequency electrostatic oscillator according to Tesla's 1894 patent for an RF pancake coil: http://www.freepatentsonline.com/0512340.pdf

What about something like this?

http://www.body-tone.com/ems4000.htm

To all who have responded:

The device I am building is an implementation of a device described in a patent held by NovoCure (US 7,890,183 B2) and is called a Tumor Treating Field Generator. The device has been licensed by the FDA for treatment of a certain kind of brain tumor (BGT, I think). I want to use it to treat throat cancer. NovoCure has declined to tell me who supplies their electrodes.

Please read through the patent if you are interested in how it works, but my device delivers 10-40V of 150KHz electric field across the throat by energizing sets of electrodes arrayed around the throat. There should be no current flow. The dielectric constant needs to be relatively high so that all the electric field passes into the neck. It would be nice if the electrodes were flexible, but not essential.

That's about all I can tell you. Thanks for your assistance.

Roger

I did download the entire patent document and read it. To make capacitors - anodised / coated polypropylene films are available in different dimensions. This has high dielectric strength. These can operate at 150 KHz and have breakdown voltages far in excess of your need- no problem.

Now I see what you are trying - just by reading a patent document - you want to make a product. Making a 150 KHz, 50 V generator for an electronic engineer is not difficult. Even if you do succeed with making the capacitive electrodes- you cannot commercialize - as the product is patented already. Just look around for polypropylene dielectric film with electrode coating. If you cannot get in a single sheet of large dimension, you can always buy smaller widths available and paralell them.

Thanks for the comment. I have already designed the field generator and it is being fabed now. All I need is the electrodes. I don't plan on productizing it.

Thanks for the clarification and the cite to the interesting NovoCure patent. Since they refuse to tell you where they got their electrodes, it may be that they have a concept but, like you, they lack the enabling electrodes. I commend you for pioneering in this important field.

The Tesla patent I mentioned would be useful in the case illustrated in Fig. 7, where the voltage between the windings of the Tesla pancake coil is due to the series-wound coil geometry, and the electric field of the coil oscillates at RF creating displacement currents parallel to the skin, for treating tumors near the skin. This might be easier and safer to try than something that involves the whole throat.

I understand you want to put planar electrodes opposed across the throat such that the healing electric field (50 - 500 kHz) is across the throat, not parallel to the skin. The purpose is, as disclosed in the NovoCure patent, to disrupt mitosis in tumors while leaving normal tissue unaffected by using a frequency between audio and microwave. Opposed Tesla pancake coils, each an electrostatic oscillator using the throat as the conductor across the dielectric, might be interesting to try for creating radial electric fields into the throat. Printed circuit board could be your electrodes for hammering at RF (microhammering).