Tuesday 25 December 2019 16:00 – 17:00 A. Payatakes Seminar Room
“Exploring the microcosmos with 3D Printing”
Dr. Areti Mourka Institute of Electronic Structure and Laser (IESL)
Abstract
Two-photon polymerization is a technique which allows the 3D printing of freeform structures with sub100nm resolution. It is a laser-based, 3D additive manufacturing technique which enables the ‘direct writing’ of computer-designed structures with resolution of a few tens of nanometers. It is based on two-photon absorption (2PA) by photopolymers; the focused beam of an ultra-fast laser ‘directly writes’ the 3D structure inside the volume of a transparent material, causing it to absorb two or more photons within the volume pixel (voxel) and polymerize locally. By removing the ‘unwritten’ area, one can obtain 3D copies of the computer design. The two-photon process has the advantages of reducing the volume within which photopolymerization occurs; increasing the resolution and also allowing the structures to be written within the volume of the photo-polymer. Two-photon polymerization enables 3D printing without the need for recoating, as required in classic 3D printing techniques. It is an appealing 3D printing technique for producing finely detailed microscale 3D structures due to its flexibility and it does not require extreme temperatures, harsh chemicals, or cleanroom facilities. In our studies, we demonstrate the tuning of the surface wetting performance via 3D microstructures. With two-photon polymerization, the role of the design of the 3D microstructures can be better understood, facilitating the applications, for which robust wetting control is required. Thus, we determine the intrinsic hydrophilicity of our homemade hybrid sol-gel polymer SZ2080 and subsequently micro-structured surfaces. Furthermore, the most commonly used photoresists in two-photon polymerization absorb in the ultraviolet (UV). These materials can therefore usually be excited with 2PA of visible or near-infrared (NIR) light. In our studies, we consider the characterization of general multi-photon absorption (MPA) correlating directly the properties of the features produced by MPA with the process parameters. Linewidth, power threshold, polymerization and damage thresholds, dynamic range and fabrication resolution have been object of investigation in our experiments. Moreover, this study complements the understanding of multi-photon polymerization (MPP) making use of machine learning for linking directly the various MPP printing parameters to the produced features.