Green Evaluation on Material Deformation Energy of Mechanical-Compressed Shear Rheology in Micro Hot-Embossing

In micro fabrication, process energy consumption is derived from material deformation, but it is actually quantified by the power consumption of device, thus leading to the difficulty of green evaluation for micro machining behavior and method. In micro hot-embossing process, a mechanical-compressed shear rheology is proposed to describe material deformation in relation to the energy consumption. The objective is to compare the green technology with micro injection molding, micro additive manufacturing and so on. First, the rheological behavior and deformation energy was modeled on the base of the shear stress driven by mechanical compression. Accordingly, the forming efficiency of mechanical compression energy and shear rheology energy is analyzed to evaluate deformation energy ratio at different microscales and identify green fabrication zone. Finally, the deformation energy were investigated and related to microscales according to material properties, process variables, die core structure, etc. It is shown the microlens size and the corresponding energy consumption increase by the shear stress. The microprism decreases above the glass transition temperature as the mechanical compression energy increases due to elastic rebound. As a result, the most important factors affect heights and energy is core temperature and compression force, respectively. Mechanical compression energy can form more efficiently than shear rheology energy. By combining mechanical compression and shear rheology, the micro hot-embossing is efficiently and greenly performed with the deformation energy of 0.15 J/mm3 and the deformation time of 0.006 s/mm3. For comparison, while comparable efficiency, the energy consumption of injection molding and additive manufacturing which should heat the whole polymer to a molten state, is 8 times and 60 times that of hot-embossing, respectively. While comparable energy consumption, the time requirement of plasma etching which needs to remove material in the atomic scale, is trillion times that of hot-embossing.