Quality Analysis of Periodical Microstructures, Created By Using High Frequency Vibration Excitation

Novel type of sensor, whose purpose is to observe skin tissue regeneration, concentration of micro particles of human fluids and etc. by measuring changes of diffraction efficiencies, is being created. The main part of sensor is diffraction grating, produced by the method of hot imprint. Therefore paper is dedicated for analysis and comparison of the quality of microstructures, created with and without high frequency excitation. Three types of measurements are performed: measurement of diffraction efficiency, optical microscopy and atomic force microscopy, in order to analyze the quality of replica. New generation vibroactive pad, whose fundament is stack type piezoactuator, is used to generate high frequency longitudinal vibrations. Thus preheated until glass-liquid transition state polymer, is forced to flow and the quality of microstructure is being enhanced. Both microstructures (with and without vibration excitation) are created on the surface of polycarbonate, using the same temperature, pressure and time modes. During the experiment periodic lamellar microstructure, whose period is 4µm is being analyzed. Analysis of diffraction measurements was performed by using laser and photodiode BPW-34. The relative diffraction efficiency of first maxima of nickel mold is 10 %, of microstructure impressed, by using ultrasonic vibration diffraction efficiency is 9.27 % of microstructure, created without vibration excitation is equal to 4.2 %. Optical microscopy is employed in order to obtain images of magnified surface view, thus allowing detect defects like bubbles of residual gas and distortions, while atomic force microscopy is performed in order to find out surface parameters like period, depth, surface roughness and obtain profile view of created microstructure. This research was funded by a grant (No. MIP-026/2014) from the Research Council of Lithuania.