Microfluidics Driven Optical Wavefront Corrector Simulation

Due to the adjustable and low-cost of microfluidic optical structures, these microfluidic optical structures attract much attention of scientists in recent years. Some application structures based on microfluidic technology have been proposed, such as wavefront corrector, microlens, optical switch, and so on.In this paper, an optical wavefront corrector actuated by microfluidic elements is studied. The mirror deformation caused by the actuation is analyzed, and calculated with Zernike polynomial in order to evaluate the device performance.Microfluidic actuation theory is discussed firstly, and then the principle of an optical wavefront corrector actuated by microfluidic elements based on EWOD (electro-wetting on dielectric) is described. The microfluidic adjusting behavior relies on the surface chemical property of the silicon wafer that is defined into a hydrophobic or hydrophilic layout. When a liquid element is applied with different voltage on borderline, the microfluidic tension change results in the deformation of mirror surface.Multiphysics analysis software is used for the emulation. First, detailed analyses on the thickness of thin mirror film, changes of contact angle and the deformation of a single droplet is done. Some new phenomena are found: a liquid element may break off into two parts under certain condition; droplet may rise endless, and so on. The complicate change of the liquid profile makes it difficult to calculate its height. These results are helpful for guiding structure design. It indicates that it is not a simple task to lead to the realization of such a mirror. Then, a model with 37 droplets is analyzed. The results prove the principle feasible again. Mirror surface shape is continuous and smooth without high stress. But there has still a large cross-linking-value. It will result in influencing-function strongly, degrading the ability for wavefront correcting. So it is necessary to optimize the model further.For an optical wavefront corrector, to describe the mirror surface with Zernike polynomial is an effective conventional calculation method. The analysis shows that traditional linear superposition of influence function is not correct for a deformable mirror actuated by liquid, so the wavefront processing algorithms will be more complex. Emulation results also showed that the residual error of wavefront correction is still distinct. This may be caused by restrictions of the software in that selections for thickness and material of film are not exact accordant to the principle. It is very necessary to improve the emulation.Emulation and analysis lead to some primary conclusions. An optical wavefront corrector actuated by microfluidic is feasible, its surface shape is continuous and smooth, it could avoid high order aberration between solid driver and mirror surface. Furthermore, its simple IC structure indicates simple process. Large cross linking value and obvious residual error are problems that need further study.