TY  - JOUR
T1  - Features of dielectric properties of medical thermal indicators based on dispersions of cholesteric liquid crystals in the polymer matrix
AU  - O.V. Kovalchuk
AU  - V.Yo. Kotovskyi
AU  - V.E. Ovcharek
AU  - I.V. Oleinikova
AU  - T.M. Kovalchuk
JO  - Semiconductor Physics, Quantum Electronics & Optoelectronics
VL  - 23
IS  - 4
SP  - 372
EP  - 378
PY  - 2020
DO  - 10.15407/spqeo23.04.372
UR  - https://doi.org/10.15407/spqeo23.04.372
AB  - Within the frequency range 10…106 Hz, the frequency dependences of the real (ε') and imaginary (ε") components of the complex dielectric permittivity of medical thermal indicators based on polyvinyl acetate and mixtures of cholesteric liquid crystals have been studied. In them, the selective reflection of electromagnetic waves visible to the human eye occurs at normal (36.6 °C) and elevated (38.2 °C) human body temperatures. Being based on the comparison of the ε' frequency dependences for the studied in this work dispersions of nematic liquid crystals prepared using the same technology and with the same polymer, it has been shown that, already on the basis of analysis of frequency dependences for ε', it is possible to ascertain the difference in characteristics for two types of thermal indicators. From the comparison of frequency dependences for ε", the main reasons of a difference between dielectric properties of the investigated medical thermal indicators for various temperatures of a human body have been ascertained.
KW  - liquid crystal thermal indicator
KW  - selective light reflection
KW  - cholesteric liquid crystal
KW  - nematic liquid crystal
KW  - polymer matrix
KW  - dielectric spectroscopy.
ER  -