Abstract
Polymer cholesteric liquid crystal (PCLC) flakes are gaining increasing interest for a wide variety of applications because of their unique optical properties and capabilities. Soft lithography is the most effective way to fabricate regularly shaped PCLC flakes. However, it is not easy to peel the flakes from the mold without breaking them. In order to peel the PCLC flakes from the patterned polydimethylsiloxane (PDMS) mold in a convenient way, in this paper, a method of coating a layer of polyvinyl alcohol (PVA) on a PDMS mold was proposed. The influence of the thickness of the PVA layer on the shape of the PCLC flakes and the release time from the PDMS mold were investigated. The results show that the presence of the PVA layer can speed up the release of the PCLC flakes and help maintain the shape effectively. Notably, the utilization of a PVA layer makes the PDMS mold recyclable. The influence of PCLC flake shape was also studied. This work will promote the development of switchable PCLC flake-based technologies.
Highlights
Polymer cholesteric liquid crystals (PCLCs) exhibit unique wavelength and polarization selective reflection owing to their molecular structure which is ordered in layers and rotates around an axis normal to the layers [1]
From the POM image of the flakes (Figure 4a), we can see that the PCLC flakes can copy the shape of the PDMS molds exactly
Flakes, we used a 3D profilometer to observe the topography of the PCLC flakes
Summary
Polymer cholesteric liquid crystals (PCLCs) exhibit unique wavelength and polarization selective reflection owing to their molecular structure which is ordered in layers and rotates around an axis normal to the layers [1]. Switchable PCLC flake and particle-based technologies are gaining increasing interest for a wide variety of applications because of their unique optical properties and capabilities. PCLC flake technology for reflective display uses flakes for reflection, which is similar to electrophoretic particles (EPD), but based on the unique reflective properties of PCLC flakes [1,2]. To develop commercially switchable technologies, of the key factors is the fabrication of PCLC flakes. In order to obtain well-defined and shaped PCLC flakes, a soft lithography consume additional energy. The result result shows shows that that the the PVA layer can speed up the release of PCLC flakes and effectively help to maintain the shape. (b)(b) flakes in Trajkovska-Petkoska’s paper [9], fabricated by by us uswithout withoutaapolyvinyl polyvinylalcohol alcohol(PVA)
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