Cholesteric materials with photonic band gap sensitive to shear deformation and mechanical sensors

Shear deformation of highly viscous liquid crystals obtained as mixtures of high and low molar weight liquid crystals results in dramatic reversible changes of the selective reflection band and colour. The colour of the material changed instantaneously during the deformation; the time of its restoration increases with the viscosity of the polymer mixture. A qualitative model considering viscoelasticity of the liquid crystals is proposed to explain changes in the reflection spectra and microscopic observations of the texture.