Mondal wins best paper award at international manufacturing conference

Graduate student Partha Mondal has won Best Paper Award at the 6^th World Congress on Micro and Nano Manufacturing. The paper, “Numerical Modeling, Experimental Investigation and Optimization of a Micro Hot Embossing Process,” is based on research conducted in the labs of MechSE Professors Placid Ferreira and Shiv Kapoor, in collaboration with Intel Corporation.

The 6th World Congress on Micro and Nano Manufacturing is organized jointly by the International Institution for Micro Manufacturing (I2M2), the 4M Association, and the International Forum on Micro Manufacturing (IFMM). This year’s conference took place September 18-21 at Northwestern University.

The conference showcases the latest research in various domains, including additive and subtractive micro-scale production processes, micro-injection molding, and advancements in surface engineering – as well as on crucial aspects related to process monitoring, control, and simulation.

The paper describes the development of a finite element simulation model and a self-made low-cost experimental setup for the micro hot embossing process. The simulation model incorporates stress relaxation behavior through the utilization of the generalized Maxwell model. It also considers thermal expansion and contact friction effects, enabling accurate prediction of the deformed pattern of PMMA.

Simulations and experiments were performed for various pressure and temperature combinations, and the resulting pattern profile depths were found to be in good agreement, between the simulation and experimental results. In addition, the simulation model was used to generate response surfaces through face centered central composite design (CCD) to identify the ideal combination of process parameters of the micro hot embossing process for creating a patterned SMD (Surface Mount Device) LED chip panel.

Hot embossing process holds significant importance as a microscale pattern replication technique. Its precision in replicating intricate 3D patterns, coupled with cost-effectiveness, makes it indispensable for creating high-precision structures with practical implications across various manufacturing industries.

However, due to the intricate visco-elastic and highly non-linear multi-physics nature of the process, creating accurate numerical models has been challenging. Consequently, these models are often simplified to manage complexity or to concentrate only on polymer stress relaxation behavior and more importantly, most numerical studies suffer from a lack of validating experiments, which undermines their ability to predict post-embossing patterns accurately.

This research presents a comprehensive numerical model that overcomes these challenges. The developed finite element numerical model employs the generalized Maxwell model to capture stress relaxation, while accounting for thermal expansion and contact friction to accurately predict replicated patterns after hot embossing. Additionally, a low-cost micro hot embossing experimental setup was built at UIUC and was used to validate the numerical model. Further research utilizing the numerical model and the experimental setup showcased the identification of ideal combination of process parameters which was then used to accurately pattern a SMD (Surface Mount Device) LED chip panel.