Nano-Second Laser Interference Photoembossed Microstructures for Enhanced Cell Alignment

Abstract

Photoembossing is a powerful photolithographic technique to prepare surface relief structures relying on polymerization-induced diffusion in a solventless development step. Conveniently, surface patterns are formed by two or more interfering laser beams without the need for a lithographic mask. The use of nanosecond pulsed light-based interference lithography strengthens the pattern resolution through the absence of vibrational line pattern distortions. Typically, a conventional photoembossing protocol consists of an exposure step at room temperature that is followed by a thermal development step at high temperature. In this work, we explore the possibility to perform the pulsed holographic exposure directly at the development temperature. The surface relief structures generated using this modified photoembossing protocol are compared with those generated using the conventional one. Importantly, the enhancement of surface relief height has been observed by exposing the samples directly at the development temperature, reaching approximately double relief heights when compared to samples obtained using the conventional protocol. Advantageously, the light dose needed to reach the optimum height and the amount of photoinitiator can be substantially reduced in this modified protocol, demonstrating it to be a more efficient process for surface relief generation in photopolymers. Kidney epithelial cell alignment studies on substrates with relief-height optimized structures generated using the two described protocols demonstrate improved cell alignment in samples generated with exposure directly at the development temperature, highlighting the relevance of the height enhancement reached by this method. Although cell alignment is well-known to be enhanced by increasing the relief height of the polymeric grating, our work demonstrates nano-second laser interference photoembossing as a powerful tool to easily prepare polymeric gratings with tunable topography in the range of interest for fundamental cell alignment studies.

A Brief Overview of Polymers Science and Technology, in Spain

“…Sebastián Muñoz-Guerra and Antxon Martínez de Ilarduya Enzymatic synthesis of poly(butylene succinate-co-caprolactone) copolyesters [45] Irene Cárdaba Irene Cárdaba, David Mecerreyes UV-photopolymerization to easily make polymer hydrogels with cleaning properties [46] Alba Martínez Carlos Sánchez-Somolinos Photolithographic technique to prepare surface relief polymer structures [47] Fundamental aspects of polymers science…”

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

“…On the other hand, photo-embossing has been extensively explored as an economical method to produce complex surface-relief structures [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. The photo-embossing method offers several benefits: it relies on the polymerization-induced diffusion mechanism which is flexible to adjustments; it works with a wide range of systems, including typical photo-polymerizable (meth)acrylates, supramolecular polymers, organic semiconductors, and fluoropolymers; and it can be applied to not only polymer thin films but also to polymer fibers.…”