# Properties of human muscle and Saline solution

##### Newbie level 5
Hello Everyone.
I have found the following properties for human muscle tissue:
Electrical Conductivity (σ): 0.58 S/m
Relative permittivity (εr): 136
Loss tangent (tan(δ)): 6
But the problem is that the softwares such as COMSOL Multiphysics need relative permeability (μr) to model the material.
Is there a way or formula to calculate μr from the given εr, σ and tan(δ) ?
or does anybody know about a reference table for relative permeability (μr) of muscle or Saline?
Thanks a lot.

#### volker@muehlhaus

COMSOL Multiphysics need relative permeability (μr) to model the material.

That sounds weird, this is a lossy dielectric! I think your need to use μr=1 and set the correct εr, σ and tan(δ).

#### FvM

##### Super Moderator
Staff member
There's a strong frequency dependence of saline solution complex permittivity which can't be reflected by just two or three constant numbers. What's the frequency of interest?

##### Newbie level 5
There's a strong frequency dependence of saline solution complex permittivity which can't be reflected by just two or three constant numbers. What's the frequency of interest?
I have two frequencies: 6.78 MHz and 13.56 MHz that are important for me.

#### Azulykit

The frequencies you cite have very long wavelengths and thus your analysis of results in the context of "antenna" performance is suspect. Painting with a broad brush antenna sizes are typically a few wavelengths and objects being studied are many wavelengths apart. A rule of thumb is that wavelength in meters is equal to 300 divided by frequency in MHz. The root of this conversation is that frequency times wavelength is the speed of light.

My caution is that since the largest mass of human muscle is much smaller than the wavelengths of interest you should be cautious to make sure that your analysis does not take you out of the "range of validity" or your analysis model.