Insulating Liquids for Antenna Measurement

[nvt088]

I am conducting some measurement for implanted antennas.
And I need some insulating liquids (to insulate antenna with environment) which have permittivity 10 and 18?
Can you suggest me some liquids like that?

Many thanks

 

[KlausST]

Hi,

i´m sorry i can´t help you with a liquid name.
But if you´re thinking of 2 component coating then be careful, because the permittivity varies with temperature.

Klaus

 

[E Kafeman]

Water relative dielectric constant is there around at 50GHz and 25*C.
Conductivity is also an important antenna factor.
If knowing frequency and temperature and what body parts that will be involved, dielectric and conductive proprieties can be found at this site: **broken link removed**
Other sources may give minor variations of these values, and some sources have separate tables for man, child and woman.
Making a solution with similar properties as body tissue is commonly done by adding salt(NaCl) in a sugar and water solution.
Some common mixtures can be found here, p38: **broken link removed**
FCC's dielectric values are given for whole body-parts, not a certain tissue.
Mix boiling water and sugar and let cool down to room temperature.
Check dielectric value. I use a VNA for that.
Adjust by adding water or another water/sugar mixture. Do never add pure sugar, it will take forever to melt and become stable.
Finally add small amount of almost saturated salt-water for correct conductivity. Do not add pure salt directly.
If need to adjust, it requires a lot of slow stirring. To fast stirring and air-bubbles are added, which gives a unstable solution.
Add something that stops fermentation, which else changes electrical properties.
Observe that electrical properties changes with temperature also for final solution.

 

[biff44]

looks like ammonia is pretty close:

https://www.engineeringtoolbox.com/liquid-dielectric-constants-d_1263.html

 

[nvt088]

what about using:
Silicon epsilon = 11 - 12.
BUTANOL Eps =17.8 (at 68 degree K)
ALCOHOL, INDUSTRIAL Eps = 16 -31;
AMYL ALCOHOL Eps =15.8 (at 68 degree K)
CASTOR OIL (HYDROGENATED) Eps =10.3 (at 80 degree K).

These liquids need to be almost perfect insulating. The test is conducted at 400 MHz, 20-25 degree C.
How can I know the electrical conductivity of organic substances? I have a table for dielectric constant of many substances.
Many thanks

 

[E Kafeman]

Why do you want insulating fluids? That is not how most body fluids behave.
Conductivity of body fluids and tissues was given in the table previously provided **broken link removed**

 

[nvt088]

Why do you want insulating fluids? That is not how most body fluids behave.
Conductivity of body fluids and tissues was given in the table previously provided **broken link removed**

Thank E Kafeman very much.

I my experiment, I need both 2/3 tissue-simulating fluid and insulating fluids.

I have recipe for making 2/3 tissue-simulating fluid as you showed me already.

I also need insulating fluids to insulate antenna from 2/3 tissue-simulating fluid. Insulating fluids work as insulators for implanted antenna. That's the way my antenna works.
How can I know the electrical conductivity of organic substances as I showed in my pdf file.

Thanks

 

[E Kafeman]

Deionized water have very low conductivity at 400 MHz. Mix it with sugar for a certain level of dielectric constant. Sugar have minimal effect of solution conductivity.