snake venomlike synthetic tripeptide acting as an antago-
nist of the postsynaptic muscular nicotinic acetylcholine
membrane’s receptor (mnAChR), was applied to the test
area . The measurements of the reﬂection coefﬁcient
were repeated again after exercise. The same subjects were
then treated with a placebo creme, based on the same
matrix but not containing the synthetic tripeptide .
This was done in order to account for any hydrating ef-
fects of the creme itself. The results demonstrated a sig-
niﬁcantly lowered signal intensity when the active compo-
nent was used, indicating the importance of neurally
active/regulated sweat glands in the received signal. The
results are illustrated in Fig. 6.
In summary it is claimed that individual sweat ducts are
low-Qhelical antennas and that their presence in the skin
means that the skin can be regarded as a 2D antenna array
in the sub-terahertz region. The spectral response is sensi-
tive to the activity of the sweat system. These claims were
substantiated experimentally where it was shown that the
spectral response of the EM reﬂectance of the skin is
indeed correlated with the activity level of the perspiration
system and follows the same temporal behavior as other
physiological parameters, such as the pulse rate and the
systolic blood pressure. This phenomenon can be used as
the basis for a generic remote sensing technique for pro-
viding a spatial map of the sweat gland activity of the
examined subjects. As the mental state and sweat gland
activity are correlated [17–19] it has the potential to be-
come a method for providing by remote sensing informa-
tion regarding some physiological parameters and the
mental state of the patients.
We thank Professor B. Kapilevich at Ariel College for
helpful discussions, Professor D. Davydov, Dr. M.
Golosovski and Mr. F. Sakran of the Physics Department
of HUJI for their assistance, Mr. E. Polygalov for stimu-
lating discussions, Dr. A. Greenbaum, Miss O. Heller,
Mr. I. Davidovich, and other members of the Dielectric
Spectroscopy Laboratory of the Department of Applied
Physics HUJI for their comprehensive help in the VNA
measurements. This work was supported by grants from
the Israel Science Foundation Grant No. 1128/05 and the
Yeshaya Horowitz Association.
*Author to whom correspondence should be addressed.
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FIG. 6. The effect of temporally deactivated sweat glands on
the relative signal intensity is illustrated by the lowered ampli-
tude, using the synthetic tripeptide, applied to the skin surface
120 min before measurement. The amplitudes are averaged over
8 subjects and shown relative to the amplitude recorded when
using a placebo creme.
PRL 100, 128102 (2008) PHYSICAL REVIEW LETTERS week ending
28 MARCH 2008