Bio-based materials obtained from renewable sources are emerging as they offer easy processing, fulfill technological, functional and durability requirements at the same time ensuring increased bio-compatibility, recycling, and eventually lower cost. Optical 3D printing (O3DP) is a rapid prototyping tool (and an additive manufacturing technique) being developed as a choice for efficient and low waste production method, yet currently associated with mainly petroleum-derived resins. We employ a single bio-based resin derived from soybean oil, suitable for O3DP in the scales from nano- to macro-dimensions, which can be processed even without the addition of photoinitiator. The approach is validated using both state-of-the art laser nanolithography setup as well as a widespread table-top 3D printers - sub-micrometer accuracy 3D objects are fabricated reproducibly using Asiga platform. Such concept is a breakthrough in rapid prototyping by switching the focus of O3DP to bio-based resins.
Recent advances in material engineering have shown that renewable raw materials, such as plant oils or glycerol, can be applied for synthesis of polymers due to ready availability, inherent biodegradability, limited toxicity, and existence of modifiable functional groups and eventually resulting to a potentially lower cost. After additional chemical modifications (epoxidation, acrylation, double bonds metathesis, etc.), they can be applied in such high-tech areas as stereolithography, which allows fabrication of three-dimensional (3-D) objects. “Autodesk’s” 3-D optical printer “Ember” using 405-nm light was implemented for dynamic projection lithography. It enabled straightforward spatio-selective photopolymerization on demand, which allows development of various photosensitive materials. The bio-based resins’ photosensitivity was compared to standard “Autodesk” “PR48” and “Formlabs” “Clear” materials. It turned out that the bioresins need a higher energy dose to be cured (a least 16 J · cm − 2 for a single layer varying from 100 to 130 μm). Despite this, submillimeter range 2.5-D structural features were formed, and their morphology was assessed by optical profilometer and scanning electron microscope. It was revealed that a higher exposition dose (up to 26 J · cm − 2) results in a linear increase in the formed structures height, proving controllability of the undergoing process. Overall, the provided results show that naturally derived resins are suitable candidates for tabletop gray-tone lithography.
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.
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.
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