Experimental study of polymer microlens fabrication using partial-filling hot embossing technique

• Efficacy of partial-cavity filling hot embossing technique for the fabrication of polymer microlenses
• Taguchi analysis to determine effects of variation in embossing parameters on lens curvature and focal depth
• Holding time has significant impact on the embossing process followed by embossing pressure and embossing temperature.

A method to fabricate microlens arrays in polymer substrates via hot embossing is presented in this paper. The partial-filling hot embossing technique of micro cavities on a mold insert through surface tension and capillary action is proven to be an effective means of limiting imperfections on the surface of microlens arrays. The effects of the investigated process parameters including temperature, embossing pressure, and holding time are analyzed via Taguchi method to identify effective processing conditions for microlens arrays of varying heights and diameters. Signal-to-noise (S/N) ratios are calculated for the focal length of the fabricated microlens arrays to identify key individual parameters and their interactions for a streamlined fabrication process. Experimental data indicates that the holding time in the embossing process has the most significant impact on lens focal length followed by embossing temperature and pressure. This study identifies a reliable means of microlens production and demonstrates the effects of varying process parameters in the partial-filling method of micro hot embossing for the production of lens arrays.

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