Manufacturing of 3D Microlens Array Mold on Bulk Metallic Glass by Self-Aligned Multi-Ball Hot Embossing

Bulk metallic glasses (amorphous alloys) exhibiting both high hardness and extraordinary thermoplastic forming ability, are perfect mold material for 3D optical microlens array. However, conventional 3D micro fabrication for metallic glass requires Si templates which are extremely costly and eco-unfriendly to machine and demold. In this study, we report a green and low-cost self-aligned multi-ball hot embossing process to create 3D micro dimple array on metallic glass by replicating spherical crowns of self-aligned precision balls. A 3D metallic glass micro dimple array with aperture of 867.2 mu m and surface roughness of 8.2 nm was fabricated in 30 s. Different from conventional hot embossing that material full-filled into mold, the new process enables micro dimple fabrication with different specifications by freely controlling the down displacement of balls. Therefore, the relationship between down displacement and depth of micro dimple was revealed through exploring the material flow behavior by a verified FE model. In addition, to test the feasibility of the fabricated metallic glass mold, a PMMA compound eye structure was embossed and its focusing and imaging performance were subsequently evaluated. This research demonstrates a new manufacturing process for rapid fabrication of 3D microlens arrays metallic glass mold in a neat and economic way.