Generation of Aspherical Optical Lenses via Arrested Spreading and Pinching of a Cross-Linkable Liquid

Abstract

Aspherical optical lenses with spatially varying curvature are desired for capturing high quality, aberration free images in numerous optical applications. Conventionally such lenses are prepared by multistep top-down processes which are expensive, time-consuming, and prone to high failure rate. In this context, an alternate method is presented here based on arrested spreading of a sessile drop of a transparent, cross-linkable polymeric liquid on a solid substrate heated to an elevated temperature. Whereas surface tension driven flow tends to render it spherical, rapid cross-linking arrests such flow so that nonequilibrium aspherical shapes are attained. It is possible to tune also the initial state of the drop via delayed pinching of a liquid cylinder which precedes its release on the substrate. This method has led to the generation of a wide variety of optical lenses, ranging from spherical plano convex to superspherical solid immersion to exotic lenses not achieved via conventional methods.

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“…[22][23][24][25]27,32] Here, the PDMS lens fabrication was studied using the droplet method on a cylindrical pillar template, combined with the hydrophobic modification of the template and the precuring of liquid PDMS to improve the fabrication precision, magnification ratio range, and to produce different lens shapes. [22][23][24][25]27,32] Here, the PDMS lens fabrication was studied using the droplet method on a cylindrical pillar template, combined with the hydrophobic modification of the template and the precuring of liquid PDMS to improve the fabrication precision, magnification ratio range, and to produce different lens shapes.…”

“…PDMS Lens Fabrication and Characterization: There are several methods to fabricate PDMS lenses including using water mold, lithography and free shaping, dielectrophoresis, and droplet-based shaping. [22][23][24][25]27,32] Here, the PDMS lens fabrication was studied using the droplet method on a cylindrical pillar template, combined with the hydrophobic modification of the template and the precuring of liquid PDMS to improve the fabrication precision, magnification ratio range, and to produce different lens shapes. The overall PDMS lens fabrication method is shown in Figure 12 in the Supporting Information.…”

“…Currently, there are two popular ways to fabricate the lens with PDMS droplet on a substrate including the upright injection [26][27][28][29][30][31] and hanging method. [27,28] On the other hand, the hanging droplet method is performed by flipping the substrate that leads to the deformation of the liquid PDMS due to the gravitational force to form the lens shape. The extent of the magnification depends on the spreading of the liquid PDMS on the substrate, which is influenced by many parameters including the substrate material and temperature, polymer volume, viscosity, and surface tension.…”

“…These techniques rely on the deposition of liquid PDMS solution to a substrate and cure it to form the elastomeric lens. Currently, there are two popular ways to fabricate the lens with PDMS droplet on a substrate including the upright injection [26][27][28][29][30][31] and hanging method. [25,[32][33][34][35][36] In the injection method, the liquid PDMS is injected on top of a substrate and cured with a heating treatment.…”

“…[26] Furthermore, the modification of the needle pinching during the liquid PDMS injection is able to create an aspherical-shaped lens that produces less aberration. [27,28] On the other hand, the hanging droplet method is performed by flipping the substrate that leads to the deformation of the liquid PDMS due to the gravitational force to form the lens shape. However, this method is time consuming as it includes multiple drop-and-bake cycles.…”