Abstract
In addition to displays, liquid crystals (LCs) have also found widespread applications in photonic devices, such as adaptive lens, adaptive optics, and sensors, because of their responses to electric field, temperature, and light. As the fabrication technique advances, more sophisticated devices can be designed and created. In this review, we report recent advances of two-photon polymerization-based direct-laser writing enabled LC devices. Firstly, we describe the basic working principle of two-photon polymerization. With this powerful fabrication technique, we can generate anchoring energy by surface morphology to align LC directors on different form factors. To prove this concept, we demonstrate LC alignment on planar, curvilinear surfaces as well as in three-dimensional volumes. Based on the results, we further propose a novel, ultra-broadband, twisted-nematic diffractive waveplate that can potentially be fulfilled by this technique. Next, we briefly discuss the current status of direct-laser writing on LC reactive mesogens and its potential applications. Finally, we present two design challenges: fabrication yield and polymer relaxation/deformation, remaining to be overcome.
Highlights
Liquid crystals (LCs) are self-assembled soft materials composed of certain anisotropic molecules with orientational orders
We have briefly reviewed the recent advances in two-photon polymerization (TPP) direct laser writing (DLW)-assisted LC devices
Taking the advantages of high-resolution 3D fabrication, TPP is able to generate LC alignment based on surface morphology
Summary
Liquid crystals (LCs) are self-assembled soft materials composed of certain anisotropic molecules with orientational orders They respond to external stimulus such as heat, electric field, magnetic field, and light [1,2,3,4,5,6]. An intriguing bottom-up three-dimensional (3D) micro- and nano-fabrication technique based on highintensity laser pulses is the two-photon polymerization (TPP) of photosensitive materials [45,46,47,48]. In a typical TPP process, high-intensity laser pulses inaugurate the crosslinking of photoresist via two-photon absorption within a localized focal volume, i.e. a voxel. This property differentiates TPP from the traditional photolithography and results in ultrafine 3D micro- and nano-structures.
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