Microlens array through induction-aided hot embossing: fabrication, optimization, and characterization
Swarup S. Deshmukh, Arjyajyoti Goswami
Abstract
In the present work, an induction-aided hot embossing (IHE) setup was developed in-house, to reduce the time required for embossing. Using the setup, a micro-lens array was successfully fabricated over PMMA substrate using laser engraved mold in less than half the time required compared to traditional hot embossing. The operating parameters were optimized through composite desirability (CD) method and teaching learning-based optimization (TLBO) to enhance the replication accuracy of the embossed microlens array. IHE experiments were designed as per rotatable central composite design (R-CCD). Embossing temperature (Te), embossing pressure, embossing time, de-embossing temperature were selected as control parameters, and deviation in diameter of the embossed microlens array was chosen as performance factor. A first-order linear model was employed for mathematical modeling. ANOVA result reveals that the developed model is adequate and Te has an impact of 44.63% on the replication accuracy. It was observed that the deviation in diameter decreases from 27.12 μm to 23.63 μm as Te increases from 120ᵒC to 130ᵒC. Final optimization result reveals that TLBO performs better than the CD. Deviation in diameter predicted by TLBO method at optimum condition is 15.83 μm which closely matches the experimental findings at optimum condition, that is, 16.57 μm.AbbreviationsHE: Hot embossing; PMMA: Polymethyl methacrylate; ROC: Radius of curvature; RSM: Response surface methodology; TLBO: Teaching learning-based optimization; CD: Composite desirability; ANOVA: Analysis of variance; To: room temperature; Tg: Glass transition temperature; Te: Embossing temperature; Pe: embossing pressure; te: embossing time; Tde: deembossing temperature; tc: Cycle time; μ: Micro; Ffrictional: Frictional force; RIE: Reactive ion etching; EDM: Electric discharge machining; hsag: sag height; IP: Input; OP: Output; IHE: Induction-aided hot embossing; CHE: Conventional hot embossing; WEDM: Wire electric discharge machining