Liquid crystal lens with doping of rutile titanium dioxide nanoparticles

A 4 mm-aperture hole-patterned liquid crystal (LC) lens has been fabricated using a LC mixture, which consisted of rutile titanium dioxide (TiO₂) nanoparticles (NPs) and nematic LC E7, for the first time. The TiO₂ NP dopant improves the addressing and operation voltages of the LC lens significantly because it strengthens the electric field surrounding the TiO₂ NP and increases the capacitance of lens cell. Unlike the doping of common colloidal NPs, that of rutile TiO₂ NPs increases the phase transition temperature and birefringence of the LC mixture, thereby helping enhance the lens power of LC lens. In comparison with a pure LC lens, the TiO₂ NP-doped one has approximately 50% lower operation voltage because of the strengthened electric field around the NPs and has roughly 2.8 times faster response time because of the decreased rotational viscosity of the LC mixture and the increased interaction between the LC molecules by the NP dopants. Notably, the doping of rutile TiO₂ NPs improves the operation voltage, tunable focusing capability, and response time of LC lens simultaneously. Meanwhile, this method does not degrade the focusing and lens qualities. The imaging performances of TiO₂ NP-doped LC lens at various voltages are demonstrated practically by tunable focusing on three objectives at different positions. These results introduce NP in the application of LC lenses.