Study Of The Liquid Crystalline Micro Flow Induced By The Magnetic Field

As an important component of Micro-Electro-Mechanical System(MEMS),micro actuator is the power source of MEMS.The micro actuators such as electrostatic,piezoelectric,electromagnetic,photothermal,memory alloys and so on have been developed.These types of drivers are simple in principle,easy to operate and have high degree of automation,and most of these drives have been applied to industrial production.But at present,the performance of these driving technologies is not very ideal in the aspects of mechanism intensity and response speed.Along with the developing of the micro-fluid driving technology,new driving modles and the liquid crystalline back-flowing driving is one of them.The micro flow of liquid crystal can be caused by the changing of liquid crystalline molecules under the magnetic field.So,in this paper,the driving power source of the micro actuators using the liquid crystal microactuation in the magnetic field was studied.The main contents of this article are as follows:(1)Numerical simulation part: The one-dimensional computation model which could connect the upper plate of the liquid crystalline cell and the liquid crystalline backflow was constructed,the equations of the backflow was deduced and reduced by MAPLE software.On the basis of given boundary conditions,the discretization process was done with the central difference method in space and the two order Runge-Kutta method in time direction.The computation was done by MATLAB software,and the algorithm optimization was also done based on the analyzing of the parallel algorithm,for cycle and the vector calculation methods.Through the numerical simulation,the influence of the factors to the liquid crystalline backflow such as the cell thickness,the voltage and the director was achieved.(2)The experimental preparation part: a strong magnetic field and a weak magnetic field experiment system for the liquid crystal micro flow research were set up respectively.First,a magnetic field generator for microscope was made.The output current of arbitrary waveform generator was input into the solenoid by OPA544 power amplifier to produce magnetic field.And the sliding rheostat was added to facilitate the stepless adjustment of various parameters of the magnetic field.And a variety of parameters were tested.The magnetic field generator output magnetic field up to 30 mT,frequency,duty ratio can be adjusted to meet the experimental requirements.Then the strong magnetic field generator was transformed and strong magnetic field experimental system was built.Secondly,liquid crystalline cell was made,including configuring and cleaning ITO glass,coating the alignment layer with the curing,abrasing the upper substrate surface,adding the liquid crystal material and other maters needing attention.(3)Experimental research part: the experimental study was divided into two parts: the weak magnetic field part and the strong magnetic field part.The upper substrate's motion under the magnetic field with various parameter can be observed and recorded by the microscope analysis system.The motion video was traced by MATLAB programming,and the velocity and displacement of the liquid crystal micro flow were calculated and compared with the theoretical value.In the weak magnetic field experiment platform,the magnetic of strength of 30 mT,different period and duty cycle of the magnetic field was applied to the liquid crystal,and no moving was obtained(the velocity ? 1nm/s).The results made in the weak magnetic field were consistent with the theoretical calculation.In the strong magnetic field experiment platform,the magnetic field with intensity of 400-900 mT,duty ratio of 20%-70%,period of 2s-16 s was applied to the liquid crystal cell.Liquid crystal's upper substrate maximum speed can reach to 8.7×10-6m/min.With the same periods and duty ratio,the moving speed increased with the increase of magnetic field intensity;With the same intensity and duty ratio,the moving speed decreased with the increase of the periods;the moving speed decreased with the increase of the duty ratio.And the experimental data and theoretical data coincide in the change trend,but were different in the specific number,at the end,the study gives the possible reasons for the numerical difference.