A basic experimental study of ultrasonic assisted hot embossing process for rapid fabrication of microlens arrays

Abstract

This paper reports a highly effective technique for rapid fabrication of microlens arrays based on an ultrasonic assisted hot embossing process. In this method, a thin stainless steel mold with micro-holes array is fabricated by a photolithography and wet etching process. Then, the thin stainless steel mold with micro-holes array is placed on top of a plastic substrate (PMMA plate) and the stack is placed in an ultrasonic vibration embossing machine. During ultrasonic assisted hot embossing operation, the surface of the stainless steel mold with micro-holes array presses against the thermoplastic PMMA substrate. Under proper ultrasonic vibration time, embossing pressure and hold time, the softened polymer will just partially fill the circular holes and due to surface tension, form a convex lens surface. After the stainless steel mold is removed, the microlens array patterns on the surface of plastic substrate can be obtained. The total cycle time is less than 10 s. Finally, geometrical and optical properties of the fabricated plastic microlens arrays were measured and proved satisfactory. This technique shows great potential for fabricating microlens array on plastic substrates with high productivity and low cost.

Effect of Filler Synergy and Cast Film Extrusion Parameters on Extrudability and Direction-Dependent Conductivity of PVDF/Carbon Nanotube/Carbon Black Composites

“…The shaping of the materials can take place via various processes, such as compression molding, injection molding, shape extrusion (such as tubes), film extrusion (cast or blown), 3D printing, and various coating processes. Cast film extrusion is an industrial method offering the possibility of continuous production of self-standing films [ 13 , 14 , 15 ]. During the cast film extrusion, the polymer melt exiting a single-screw extruder through a slit die is stretched in air and cooled on a smooth metallic surface of a thermoregulated chill-roll.…”

“…As the main processing parameters, the roll temperature, the take-off velocity, and the cooling during taking-off influence the final microstructure already of unfilled polymers. There are only a few scientific publications [ 13 , 14 , 15 ] that deal with influencing factors during the melt-shaping of polymer films, e.g., for polycarbonate [ 13 ] and polypropylene [ 14 ]. For composites containing CNTs, the phenomenon of a strong alignment of CNTs in the extrusion direction was discussed on the example of blow-molded high-density polyethylene/multiwalled carbon nanotube films, which resulted in enhanced mechanical properties in this direction [ 16 ].…”

Manufacturing of Micro-Lens Array Using Contactless Micro-Embossing with an EDM-Mold

“…The micro-lens array (MLA), called a Fly-eye lens, is widely used in optical communication, lighting displays, optical sensors, and illumination because of its unique structures and function. There are many methods that can fabricate micro-lenses, including plasma etching [1], laser ablation [2], micro-milling [3], photolithography [4], micro-injection [5], glass reflow [6] and micro hot embossing [7][8][9][10][11][12]. Wherein, micro hot embossing is regarded as one of the most promising processes for mass production.…”

Application of graphene–polymer composite heaters in gas-assisted micro hot embossing

“…1 Reductions in cycle time were reported for ultrasonic hot embossing of microstructures. [2][3][4][5] High-frequency induction heating was demonstrated to be effective in productivity enhancement in hot embossing. 6 However, either signicant modications in tool materials are necessary to full the IR-transparent requirement, or special implementations must be made in the embossing facility for ultrasonic or induction heating embossing.…”