The Research Of Femtosecond Laser-induced Polymerization Micromechanics

As a new technology of laser lithography in MEMS, femto-second laser two-photon photofabrication has its unique technological characteristics, including fabrication ability of true 3D microstructures, sub-micron resolution and so on. Recently, it has been gained extensive attention. The research on mechanical properties of materials at micro or nano scale is one of the most significant parts in MEMS. With the support of NSFC (No.50275140 and No.50335050), the mechanical properties of the voxels and single layer fabricated by femto-second laser two-photon photopolymerization are measured and analyzed. The main research results are listed as follows:Firstly, voxels are fabricated using two-photon photopolymerization method. The mechanical properties of voxels are investigated by atomic force microscopy equipped with calibrated tipless micro-cantilevers. To calculate the elastic modules of the voxels, different elastic models are utilized depending on whether the effects of adhesion are obvious or not. In order to eliminate the errors caused by geometrical approximations during analytical methods, the modulus of voxels is determined by applying Finite Element Method (FEM) models when adhesion is not obvious. It is found that the elastic modulus of the voxels is far below those of macro material.Secondly, to decrease the complexity of experiments, a series of mechanical models programmed by orthogonal method are constructed by FEM. These models are solved to obtain the training and testing samples for Support Vector Machine. Based on obtained training samples, the Support Vector Machine regression is performed. The relationship between the forces acting on the micro-cantilever and the deformation of voxels is acquired. Then we prove this relationship with testing samples. Such method improves the efficiency while the accuracy of the analysis can be remained.Finally, single layer suitable for mechanical tests is manufactured based on analyzing the influences of overlapping degree of voxels on micro-lines and layers. The specimen is scanned by nanoindenter equipped with Cono-Spherical tip to determine the measurement area. We measured the areas according to different loading-unloading procedures and obtain force-displacement curves, which contain the exact information of the elastic modulus and hardness of the tested material. We found that the mechanical properties of the micro-layers are in agreement with the macro ones.All these experimental results can do help to our projects and can boost the development of this research area. We also prospect the trend of this technology in the end.