Abstract
AbstractIn this communication, the fabrication of electrically tunable bifocal liquid crystal (LC) microlenses using drop‐on‐demand inkjet printing is demonstrated. By treating the glass substrate with a homeotropic alignment layer, the printed droplets are found to form plano‐convex lenses with focal lengths in the range of 220–463 µm, depending upon the number of droplets deposited at each location on the substrate. The precision of the process allows for the microlenses to be deposited in between in‐plane indium tin oxide electrodes. In the presence of a high amplitude electric field, the director within the LC droplets is observed to align with the direction of the applied field, but without any accompanying distortion in the droplet profile. However, these changes in the LC director alignment are found to result in a bifocal behavior rather than a continuous change in the focal length. It is also found that there exists a range of voltages for which two focal planes are observed.
Highlights
Tunability of the focal length adds function- as well as photographic images of plano-convex microlenses ality to the microlenses[13,14,15,16,17,18,19,20,21] and it has recently been reported printed between in-plane electrodes
For the glass substrates used in this study, we found that the homeotropic alignment layer was the dominant factor in terms of dictating the resultant droplet profile
The simple electrode arrangement on the substrate allowed us to demonstrate the electrical tunability of a printed LC microlens, which was found to exhibit a bifocal behavior due to the reorientation of the LC director in the droplet in the presence of an applied voltage
Summary
A series of microscope images showing the evolution in the director alignment of the 222 μm diameter microlens as the electric field amplitude is increased are presented in Figure S5 (Supporting Information), where it can be seen that the behavior resembles that observed for the 255 μm diameter lenses. We have demonstrated the fabrication of electrically tunable bifocal microlenses by using drop-on-demand inkjet printing to deposit nematic LCs precisely in the 500 μm gap between in-plane electrodes These printed droplets were found to form plano-convex lenses after impact with the substrate. The simple electrode arrangement on the substrate allowed us to demonstrate the electrical tunability of a printed LC microlens, which was found to exhibit a bifocal behavior due to the reorientation of the LC director in the droplet in the presence of an applied voltage. These findings could be of importance for 3d imaging www.advmatinterfaces.de applications where the two separate focal planes could be used to give the impression of depth perspective
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