A Focus on our PhD Students – Efrat Shukrun-Farrell

My love for chemistry started when I was 9 years old, when my parents enrolled me in an after-school chemistry curriculum. Ever since that time, I knew that I wanted to be a scientist, so no one was surprised when I enrolled in a broad-scoped Bachelor degree in biology and chemistry at the Hebrew University of Jerusalem, Israel. In the second year of my undergraduate studies, I started working as a research assistant in Professor Shlomo Magdassi’s applied chemistry laboratory. Professor Magdassi is a leading researcher in the fields of surface chemistry and materials science, and my research at that time was focused on mesh printing of transparent and conductive films for applications in solar cells and electronics. During my work in that laboratory, I was fascinated by the research work being undertaken, and I realized that I wanted to continue my graduate studies there.

This was the beginning of my Ph.D. studies as I continued to a direct Ph.D. track, specializing in materials chemistry and 3D printing. My main research focuses on developing formulations for 3D printing of ceramics and hybrid materials. 3D printing has received much attention during recent years with new materials and printing technologies under continuous development. There were (and still are) many challenges in this field, which are related to materials science and which require creative and impactful solutions. When we decided to address the materials challenges, Professor Magdassi offered me the opportunity to explore new approaches for enhancing the printed structures’ performances by making them hybrid or fully ceramic. Until then, most of the research in that field was focused on integrating ceramic particles within an organic matrix, which can be a drawback when printing by stereolithography (SLA) – the highest resolution 3D printing technique. To overcome that challenge we decided to use the sol-gel process in order to fabricate particle-free printing formulations for 3D printing of ceramic and hybrid objects. At that time, the sol-gel process, which would soon become my main expertise, was only a phrase that I had heard once or twice during my Bachelor degree.

The requirements imposed on sol-gel-based printing formulations are different and the printing compositions must be tailored to the specific 3D printing technology being used. Most of the 3D printing techniques are based on the sequential deposition of 2D patterns along the Z-axis, to create a 3D structure. By SLA, the 2D patterns are formed by selective light irradiation of photosensitive monomers, or oligomers in a liquid form, in the presence of dissolved photoinitiators (PIs). The PI is activated by the printer’s light source, which initiates the photopolymerization of the monomer/oligomer to form a cross-linked polymeric layer, and hence the printing formulation must contain organic UV-curable groups.

In my first project, I have developed 3D printable sol-gel-based printing compositions, which enabled the fabrication of 3D objects with unique properties. The liquid ink is composed of hybrid UV-curable metal-alkoxy oligomers that can undergo both a sol-gel process and radical polymerization. The synthesis of hybrid photopolymerizable oligomers was performed by a sol-gel process, and the curing (gelling) of the 2D layers of the 3D structures is done via photopolymerization during printing. After printing, during an aging process, a polycondensation reaction occurs, in which adjacent silanol groups forms a strong network. In a second project, a new approach for 3D printing of complex-geometry silica objects with ordered mesoporous structures was developed. The process uses photo-curable liquid compositions that contain a structuredirecting agent, silica precursors, and elastomer-forming monomers that, after printing and calcination, form porous silica monoliths. The objects have an extremely high surface area (1900 m2 /g), very low density, and are thermally and chemically stable. In my last project, we collaborated with Professor David Avnir to develop a process for the photochemical preparation of silica aerogels, and fabricating them in highly complex shapes at all scales, from the macro scale down to the microns scale by 3D printing.

Now I’ve reached the last days of my PhD, writing my thesis and saying goodbye to the wonderful professional and personal experiences that I had working in Professor Magdassi’s laboratory – and to the people who supported me. I’m looking forward to a research career that is as rich and fulfilling as my work to date!