Beam Steering And Particle Manipulation Based On Photosensitive Cholesteric Liquid Crystal

Liquid crystals(LCs)have attracted extensive attention in many fields for their excellent optical properties.Thanks to self-assembly characteristics and stimuli responsiveness,cholesteric liquid crystals(CLCs)are highly tunable,whose configuration can be adjusted via various methods.On-chip CLCs,functioning as a semi-open system,are expected to expand the application of CLCs in biosensors,optical diffraction and other fields.In this thesis,based on driving laws of On-chip CLCs,dynamic beam control and flexible particle manipulation are realized via a photopatterning technique.This exhibits a great possibility of potential applications in the field of space optical communication and directional transport.Details are summarized as follows:1.The photosensitive films are obtained by doping chiral agents.Dynamic beam control in the fingerprint texture is proposed,with the combination of CLC semi-open systems and photoalignment technique.Firstly,the light-driven behavior of the on-chip CLC fingerprint texture is verified.By adopting the photoalignment technology,the author investigates the regularity of grating period and the pitch of fingerprint texture at different stages when the system is stimulated by light at different wavelengths.And then,the theoretical model of the directional arrangement of fingerprints on the chip is constructed.Secondly,on-chip CLC fingerprint textures with different alignment patterns are prepared,and corresponding diffraction patterns under are obtained as well.After previous steps,its unique diffraction effect is adjusted under ultraviolet light irradiation and an adjustable diffraction angle about 8o is achieved.The relationship between the dynamic changes of the diffraction patterns and the rotation behavior of on-chip CLC fingerprint texture is explained.To conclude,this dynamic beam control method is featured by fast response speed,stable diffraction effect and multidimensional diffraction modes,and is expected to play an active role in the fields of relays and optical switches.2.Precise manipulation of particles in CLCs.The maximum distance that the particles can move smoothly in the horizontal direction can reach 689.4 ?m and the maximum speed is 41.68 ?m/min,which verifies that the fingerprint texture has the ability to manipulate particles.Therefore,a theoretical model for manipulating the movement is proposed.The defects of the system with the lowest potential energy will capture their surrounding particles.During the optical driving,the particles will follow the movement of the potential energy to change the position and generate a certain distance.The cyclic energy distribution of fingerprint texture and the driving force provided by external light are two essential factors.Especially for two aspects of speed and direction of particles,the omnidirectional control of particles is realized by changing the experimental conditions such as the light intensity and grating period.And then,the author has innovatively realized the diversified motion modes of particle convergence,divergence,looping,screening,and circumference.With continuous conversions of light stimuli,the researcher fulfills the goal of the continuous control of particle trajectory,and real-time particle position trajectory track.In summary,this investigation proposes a concept of "on-chip laboratory for particles manipulation" which is simple to prepare and highly integrated,which enriches the manipulation methods in the field of liquid crystals and is expected to be applied to fields such as biology and medicine.