Edvinas Skliutas

Bioresists from renewable resources as sustainable photoresins for 3D laser microlithography: material synthesis, cross-linking rate and characterization of the structures

Stereolithography (SLA) allows rapid and accurate materialization of computer aided design (CAD) models into real objects out of photoreactive resin. Nowadays this technology has evolved to a widespread simple and flexible personal tabletop devices - three dimensional (3D) optical printers. However, most 3D SLA printers use commercially available resins which are not cheap and of limited applicability, often of unknown chemical ingredients and fixed to certain mechanical properties. For advanced research, it is important to have bio-resin appropriate to 3D print microscaffolds for cell proliferation and tissue engineering. To fill these requirements would be to use sources from bio-based resins, which can be made of naturally derived oils. Chosen substances glycerol diglycidyl ether and epoxidized linseed oil can be obtained from renewable recourses, are biodegradable and can be synthesized as sustainable photosensitive materials.1 UV (ff=365 nm) lithography was employed to determine their photocross-linking rate and cured material properties. After exposing material to UV radiation through a micro-patterned amplitude mask selective photopolymerization was observed. Acetone was used as a solvent to dissolve UV unaffected area and leaving only exposed microstructures on the substrate. The resins were compared to FormLabs Form Clear and Autodesk Ember PR48 as standard stereolithography materials. Finally, 3D microporous woodpile scaffolds were printed out of commercial resins and cells adhesion in them were explored.

The effect of larger than cell diameter polylactic acid surface patterns on osteogenic differentiation of rat dental pulp stem cells: Effect of surface patterns on DPSC osteogenic differentiation

Topography of the scaffold is one of the most important factors defining the quality of artificial bone. However, the production of precise micro- and nano-structured scaffolds, which is known to enhance osteogenic differentiation, is expensive and time-consuming. Meanwhile, little is known about macro-patterns (larger than cell diameter) effect on cell fate, while this kind of structures would significantly facilitate the manufacturing of artificial skeleton. Therefore, this research is focused on polylactic acid scaffolds macro-pattern impact on rats dental pulp stem cells (DPSCs) morphology, proliferation, and osteogenic differentiation. For this study, two types of scaffolds were 3D printed: wavy and porous. Wavy scaffolds consisted of 188 μm wide joined threads, meaning that cells might have been curved on the filament as well as compressed in the groove. Porous scaffolds were designed to avoid groove formation and consisted of 500 μm threads, arranged in the woodpile manner, forming 300 μm diameter pores. We found that both macro-surfaces influenced DPSC morphology compared to control. As a consequence, enhanced DPSC proliferation and increased osteogenic differentiation potential was registered in cells grown on these scaffolds. Finally, our results showed that the construction of an artificial bone did not necessarily require the precise structuring of the scaffold, because both types of macro-topographic PLA scaffolds were sufficient enough to induce spontaneous DPSC osteogenic differentiation.

Renewable materials as 3D photostructurable resins employing 405 nm tabletop dynamic projection lithography (Conference Presentation)

Optical three-dimensional printing (O3DP) have become an advanced and widespread technology for the realization of 3D computer aided models (CAD) to free-form objects. It has evolved to desktop stereolithographic (SLA) devices allowing rapid, accurate and high spatial resolution prototyping out of photoreactive resins. Most of commercially available resins are not cheap and often of unknown chemical ingredients, which limits their wider applicability. Recent advances have shown that renewable raw materials can be applied for preparation of polymers. For example, glycerol, the by-product of biodiesel refining, is a promising candidate which can be used as monomer in the synthesis of bio-based resins as it is or after chemical modification [1]. The primary substance for the photosensitive material was chosen glycerol diglycidyl ether (GDGE) [2]. The following composition was: GDGE, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (30 mol %), radical (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) and cationic (diphenyliodonium hexafluorophosphate) photoinitiators and N-vinylcarbazole as an additive. Autodesk’s open source 3D optical printer Ember (AutoDesk) employing 405 nm light was implemented for dynamic projection lithography (DPL). It allowed selective photopolymerization on demand, later followed by characterization of various photosensitive materials. The bio-based resin was compared to standard materials: Formlabs Clear and Autodesk PR48. It turned out, that the resin had much longer curing time (>10 min for a single layer). Despite this fact, fine structural features were formed and their morphology was characterized using optical profilometer and scanning electron microscopy. It was assessed, that by increasing energy dose, higher structures were acquired and this dependency is linear, thus enabling tabletop graytone lithography out of renewable bioresins.