Thermal stress and shrinkage were investigated to analyze pattern defects during the cooling and demolding steps in hot embossing. Hot embossing is one of the most popular fabrication methods that replicate polymer microdevices in fields such as micro-fluidics and micro-optics. Numerical models were developed to study the effect of thermal stress and adhesion force on a molded microstructure during the cooling and demolding steps of micro hot embossing. The alignment microstructure, a hemisphere-tipped post, was located at four radial locations of 5, 10, 15, and 20 mm from the center of the polymer substrate to determine the effect of thermal stress and adhesion forces, relative to pattern location, leading to pattern deformation. Results showed that thermal stress increased as the microstructure was moved further away from the center of the polymer substrate due to an increase in shrinkage velocity. Process parameters could be designed to improve replication fidelity by analyzing the stress distribution of a molded microstructure during cooling and demolding.
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