Nano-Second Laser Interference Photoembossed Microstructures for Enhanced Cell Alignment

Droplet dynamics affecting the shape of patterns formed spontaneously by transforming UV-curable emulsions

Forming large pitch and depth patterns spontaneously based on a bottom-up approach is a challenging task but with great industrial value. It is possible to spontaneously form an uneven (concave-convex) patterns with submillimeter-to-millimeter-scale pitches and depths by the direct pattern exposure of a UV-curable oil-in-water (O/W) emulsion liquid film. UV irradiation generates a latent pattern of a cured particle aggregation in the liquid film, and an uneven structure is spontaneously formed during the subsequent drying process. This process does not require any printing and embossing plates or development process. In this report, we presented an example of unevenness formation with a maximum pattern depth of approximately 0.4 mm and a maximum pitch width of 5 mm. The patterns formed by this method have raised edges in the exposed areas and fogging in unexposed areas. The pattern shapes become conspicuous under overexposure conditions, but the formation mechanism has not yet been understood in detail and needs to be investigated. In this study, we focused on the exposure process and clarified the mechanism of pattern formation by analyzing the dynamics of emulsion droplets in the medium by an in situ microscopy observation method. As a result, we found that the fogging was mainly caused by light leakage from the exposed area, and the raised pattern edges were caused by droplets transported from the unexposed area to the exposed area. Furthermore, the convection caused by the heat generated from polymerization is a determining factor affecting all these phenomena. By controlling the pattern shape related to convection utilizing direct projection exposure, we showed an example of eliminating raised pattern edges with a height difference of approximately 0.1 mm. By devising and selecting exposure methods, we can expand the range of design applications such as interior decorative patterns.

A Brief Overview of Polymers Science and Technology, in Spain

This Special Issue State-of-the-Art on Polymer Science and Technology in Spain is comprised of a collection of 42 publications/contributions related to very different topics undertaken by the numerous research groups working in Spain in Polymer Science and Technology. This monograph collects the contributions of more than 200 different authors from 24 different national Institutions (>30 different centers/departments) from Universities and CSIC centers distributed throughout the whole of Spain. Two-thirds of the contributions to this Special Issue arise from Institutional collaborations, half of which are international collaborations with European research groups and the other half with other international research groups outside Europe including China, Australia or United States of America among others. This brief overview communication provides a general overview of the research lines in Polymer Science and Technology covered in Spain and show most of the representative polymer groups and their distribution throughout Spain. Most of Spanish polymer groups belong to the Grupo Especializado de Polímeros (GEP) being part of the European Polymer Federation (EPF). It also shows how Spanish science about polymers is positioned at European level.

Photo-Embossed Surface Relief Structures with Improved Aspect Ratios and Their Applications in Liquid Crystal Devices

Photo-embossing has been developed as a convenient and economical method for creating complex surface relief structures in polymer films. The pursuit for large aspect ratios of the photo-embossed structures has never stopped. Here, we demonstrate a simple strategy to obtain improved aspect ratios by adding a quick solvent developing step into the photo-embossing process. A good solvent for the monomer is used to remove unreacted monomers from the unexposed region, resulting in deepened valleys of the surface reliefs. In a polymer film as thin as 2.5 µm, the height of the surface reliefs can be increased by a factor of three to around 1.0 µm. This strategy is also shown to be compatible with other methods used to improve the aspect ratios of the photo-embossed structures. Lastly, we employ these surface relief structures in the fabrication of liquid crystal (LC) devices and investigate their performances for visible light regulation.