In-situ investigation of macro/micro deformation behavior of glass into microchannels during hot embossing

Hot embossing has become a mature technology for manufacturing glass functional microstructures, which can be used in optical and biomedicine industries. However, the viscoelasticity and structure relaxation of glass are highly sensitive to the thermal history, and the interface characteristics between glass and mold during the hot embossing are quite complex. Therefore, it remains a challenge to accurately predict the shape of glass replica in hot embossing. This study integrated an in-situ observation system into the hot embossing machine and realized the understanding of the macro/micro deformation behavior of glass in an intuitive and real-time way. In the in-situ observation method, the real-time cross-section of glass and mold during the embossing step is recorded by the high depth-of-field optical microscopy. By video processing, the macro/micro-scale profiles are extracted based on the topological structural analysis. As a result, the information about the evolution of the thickness of glass substrates, and the filling ratio, central curvature of glass microstructures is obtained. The measured accuracy of the in-situ observation system was evaluated by the comparison with 3D profiler. Repeated hot embossing experiments were carried out for demonstrating the reproducibility of experimental data. After that, a series of glass hot embossing experiments were carried out under various embossing temperatures, embossing forces, embossing time, maintenance time and microchannel width. The evolution of the multiscale geometric features of glass replica in both the single-channel and the multi-channels were analyzed, so that the real-time macro/micro deformation behavior of glass during the hot embossing process could be evaluated in a straightforward and reliable way.