Electrically Tunable Printed Bifocal Liquid Crystal Microlens Arrays

Abstract

In 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.

Design, Fabrication, and Applications of Liquid Crystal Microlenses

“…For example, in 2020, S. M. Morris et al reported LCMs by using a DoD inkjet printing system. [ 48 ] As shown in Figure 6b. I, the high‐precision needle controlled by pulse signal can extricate LC droplets with an accuracy of ±5 µm.…”

“…Reproduced with permission. [ 48 ] Copyright 2020, Wiley‐VCH. h) The polymer mold fabricated by TPP direct‐laser writing.…”

“…A large quantity of methods has been proposed to regulate the tilt angle of GRIN lens, including patterning electrodes (Figure 1d,e), [ 46 ] drop‐on‐demand (DoD) system (Figure 1f,g), [ 47 ] and polymer mold (Figure 1h). [ 48 ] The principles underlying these seminal works can be concluded as employing external stimuli to steer the tilt angle of the director orientations, create the GRIN accordingly, and finally obtain the desired GRIN microlens. The resulting microlenses usually have adjustable focal lengths.…”

“…Generally, polymer molding can be fabricated via direct light molding [ 98,99 ] or mechanic‐assisted molding. [ 48,100 ]…”

Spatially Patterned Polymer Dispersed Liquid Crystals for Image‐Integrated Smart Windows

“…For example, printing has already been employed with LC materials to develop monodisperse LC solutions, and optically-pumped thin-film lasers, as well as electrically and thermally tunable microlenses. [36][37][38][39] Due to its versatility, DoD inkjet printing offers a unique platform for the manufacture of PDLC films. By printing an LC and UV-curable polymer ink, PDLC films with spatially patterned emblems and logos can be successfully manufactured.…”