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Radiofrequency interaction with conductive colloids: Permittivity and electrical conductivity of single‐wall carbon nanotubes in saline
Author(s) -
Gach H. Michael,
Nair Tejas
Publication year - 2010
Publication title -
bioelectromagnetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 81
eISSN - 1521-186X
pISSN - 0197-8462
DOI - 10.1002/bem.20595
Subject(s) - permittivity , materials science , carbon nanotube , conductivity , colloid , electrical resistivity and conductivity , polarization (electrochemistry) , electrode , dielectric , electrical conductor , nanoparticle , absorption (acoustics) , analytical chemistry (journal) , composite material , chemical engineering , nanotechnology , chemistry , optoelectronics , chromatography , electrical engineering , engineering
Conductive nanoparticles may enhance tissue heating during radiofrequency (RF) irradiation. Specific absorption rate (SAR) is known to rise with the electrical conductivity of tissue. However, no studies to date have measured the relationship between complex permittivity and nanoparticle concentration in tissue‐like samples. The complex permittivities of colloids containing single‐wall carbon nanotubes (SWCNTs) in normal (0.9%) saline were measured from 20 MHz to 1 GHz. Carbon concentrations ranged from 0 to 93 mM (0.06% volume), based on SWCNT weight per volume. Measurements were made with 0.02% Pluronic F108 surfactant added to the colloids to prevent SWCNT flocculation. The data were fit to the Cole–Cole relaxation model with an added constant phase angle element to correct for electrode polarization effects at low RF frequencies. Electrode polarization effects increased with carbon concentration. The real parts of the permittivities of the colloids increased with carbon concentration. The static conductivity rose linearly with carbon concentration, doubling from 0 to 93 mM. The SAR of the colloids is expected to increase with RF frequency, based on the properties of the imaginary part of the permittivity. Bioelectromagnetics 31:582–588, 2010. © 2010 Wiley‐Liss, Inc.