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Article

Use of Biobased Resins Derived from Renewable Monomers for Sustainable 3D Fabrication Through Two-Photon Polymerization

by
Francisco Gontad
1,*,
Jaime Cuartero
1,
Sara Vidal
1,
Nerea Otero
1,
Natalia M. Schulz
2 and
Tobias Robert
2,*
1
AIMEN Laser Technology Centre, Polígono Industrial de Cataboi SUR-PPI-2 (Sector) 2, Parcela 3, ES-36418 O Porriño, Spain
2
Fraunhofer Institute for Wood Research—Wilhelm-Klauditz-Institut WKI, Riedenkamp 3, 38108 Braunschweig, Germany
*
Authors to whom correspondence should be addressed.
J. Manuf. Mater. Process. 2025, 9(3), 89; https://doi.org/10.3390/jmmp9030089
Submission received: 17 January 2025 / Revised: 6 March 2025 / Accepted: 7 March 2025 / Published: 10 March 2025
Browse Figures
Versions Notes

Abstract

:
This work demonstrates the fabrication of microstructures with formulations containing bio-based prepolymers derived from itaconic acid, commercial reactive diluents, photo initiators, and inhibitors, through two-photon polymerization. Lateral and vertical resolutions within the micron range can be achieved by the adjustment of laser scanning speed and pulse energy, and through the use of microscope objectives with high magnification and numerical aperture. The fabrication throughput can be slightly increased by simultaneously increasing the laser pulse energy and scanning speed, with special care to keep the resolution of the features that can be written via two-photon polymerization. Feasibility for the fabrication of 3D microstructures is demonstrated, through the fabrication of benchmark structures like woodpiles and pyramidal structures. Thus, this work proves that resins based on biobased formulations, originally designed for UV-curing 3D printing, can be adapted for two-photon polymerization, obtaining 3D microstructures with resolutions within the micron range.

1. Introduction

Three-dimensional printing has become one of the most wide-spread technologies for the fabrication of complex pieces of different materials, (ranging from metals for the fabrication of mechanical parts [1,2,3,4] to polymers), that can be used for a very wide range of applications, including microoptics [5,6,7], metasurfaces [8,9], or small 3D biomedical devices [10,11]. In the case of polymeric 3D printing, there are two main routes for fabrication: material extrusion [12] and photo curing [13]. While material extrusion mainly focuses on fabrication productivity, being able to produce large pieces in a relatively short time, photocuring focuses on the finishing of parts, producing 3D pieces with extremely high resolution that can be applied in biomedical [14] or optical applications [15].
There are several alternatives for photocuring 3D printing techniques, such as stereolithography (SLA) [16], direct light printing (DLP) [17], or two-photon polymerization (TPP) [18,19,20,21,22,23], with variable resolution and fabrication speeds, all of them involving the use of viscous resins. Amongst them, TPP is the 3D printing technique that provides a higher resolution, enabling the fabrication of functional micro/nanostructures for different purposes [18,24] as has already been demonstrated for demanding applications such as the fabrication of 3D scaffolds for tissue engineering [14] or optical surfaces [15].
Currently, many commercial resins used for TPP are wholly derived from petrochemical resources, like for example diazonaphthoquinone, polymethylmethacrylate, or polyimides, which present excellent mechanical, thermal, and dielectric properties [25]. However, despite the low waste generated with this technique, developing biobased alternative resins is of high importance for the establishment of a more sustainable and viable fabrication technique, due to the high resistance to biodegradation of petroleum-based resins and the fact that they come from a limited source of raw materials. Over recent years, UV-curing materials for additive manufacturing applications derived from biobased itaconic acid have evolved to be an alternative to the materials derived from petrochemical acrylic and methacrylic acid [26,27,28,29,30,31,32,33,34,35,36]. The resulting materials are compatible with standard UV-curing additive manufacturing processes and the manufactured parts exhibit properties that can compete with conventional (meth)acrylic acid-based materials. Therefore, it is of high interest to examine if itaconic acid-based materials are also suited for TPP-processes. In this work, biobased polymer resins derived from itaconic acid and other renewable monomers have been synthesized and formulated with reactive monomers and photoinitiators to obtain renewable resins that are suitable for the fabrication of 3D microstructures via TPP, with a resolution and mechanical properties in the range of commercial petrochemical resins.

2. Materials and Methods

2.1. Materials

Itaconic acid (IA, 99%), succinic acid (SA, 99%), isophthalic acid (IPA, 99%), sebacic acid (SebA, 99%), and 4-methoxyphenol (MeHQ, 99%) were purchased from Merck, Darmstadt, Germany. 1,2-Propanediol (1,2-PDO, >99%) was acquired from Carl Roth, neopentylglycol (NPG, 99%) from Thermo Scientific, and ethylene glycol (EG, >99%) from VWR. 1,3-Propanediol (1,3-PDO, 99.7%) was kindly provided by DuPont Tate & Lyle Bio Products, Loudon, NH. Acryloyl morpholine (ACMO, 99%) and isobornylacrylate (IBOA) were purchased from Rahn GmbH, Frankfurt, Germany. Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) was purchased from IGM Resins.

2.2. Polyester Synthesis

The polyesters were synthesized via azeotropic polycondensation reactions described previously [32,33,37].

2.3. Formulation Preparation

To prepare the formulations suitable for TPP, a mass ratio of polyester/reactive diluent/TPO:MeHQ of 50:48.95:1.0:0.05 was used. As an example, the preparation of 100 g of FORM-01 is described as follows: 50.0 g of PREPOL-03, 48.95 g of IBOA, 1.0 g of TPO, and 50 mg of MeHQ were introduced to a lid-closing metal can, to prohibit light exposure. The formulation was mixed on a laboratory shaker (IKA, KS 260 basic, Staufen, Germany) at 400 rpm for 24 h to ensure homogeneous mixture of the resin.

2.4. TPP Process

The first step of the TPP involved the absorption of two photons providing the cumulative energy to induce polymerization. There are two main ways of inducing photopolymerization: through radical generation or through cationic generation in a monomeric or oligomeric material [38]. In order to increase the reaction rate, photoinitiators are usually added to promote the polymerization with wavelengths within the visible and near infrared spectrum [39]. Two different TPP setups were used for the 3D microfabrication tests of the resins. A commercial TPP machine from Microlight 3D (Grenoble, France) (µFAB) was used for the realization of basic 3D microstructures, with the aim of analysing the fabrication capabilities of the resins with a commercial machine. Additionally, an experimental setup based on a set of linear motion axes from PI Micos was used, in combination with a femtosecond pulsed laser from Ekspla (Vilnius, Lithuania) working in the second harmonic (515 nm). A ZEISS N-Achroplan 63× microscope (Oberkochen, Germany) objective with a numerical aperture of 0.85 was used as the focusing lens during the trials performed with the µFAB, while an OLYMPUS LMPLFLN50× (Hamburg, Germany) was integrated as part of the assembled experimental setup. This second objective, with an NA of 0.5, offers a working distance above 10 mm enabling TPP across thick glass substrates.
The samples were prepared by drop casting the resins provided by Fraunhofer WKI on the surface of a glass microscope slide before the 3D printing experiments. After the laser printing process, the samples were washed to remove the non-cured resin with a 50:50 solution of acetone and isopropanol, and then air dried.
Two kinds of samples were fabricated with the two experimental apparatus described above: meshes of crossed lines to test the resolution that could be achieved with the technique, and 3D microstructures to test the viability of 3D microfabrication. All the samples were characterized using a confocal microscope (Sensofar, S Neox, Barcelona, Spain) to analyze the influence of the processing parameters on the morphology of the fabricated structures, without the need of additional postprocessing. In the case of the crossed lines, both 2D and 3D images of the photopolymerized samples were taken with the confocal microscope to analyze the lateral and vertical resolution of the fabricated lines. Three-dimensional profiles of the 3D microstructures were taken to confirm the feasibility of the resists for microfabrication. The measurements of the lateral sizes and height of the fabricated samples were carried out with the help of the SensoSCAN 5.3 software from Sensofar; several measurements were taken per line in order to obtain an average value of line width and height.

3. Results

Prepolymer Composition

As prepolymers for the resin formulations, itaconic acid-based polyesters were used. The resins were synthesized via polycondensation of itaconic acid, a second dicarboxylic acid, and two or three different diols (Scheme 1) as reported previously [32,33,37]. The exact composition and biobased content of the prepolymers are shown in Table 1. The prepolymers were obtained as yellowish viscous resins. Unlike most commercially available prepolymers, these polyesters are completely free of (meth)acrylic acid as the α,β-unsaturated double bond of the itaconic acid undergoes UV-induced radical crosslinking.
With these different prepolymers, a first set of resins were formulated (Table 2). Isobornylacrylate (IBOA) was used as partially biobased reactive diluent to adjust the viscosity of the resins. In one case (FORM-02) acryloylmorpholine (ACMO) was added to study the influence of the more reactive acrylamide on the performance of the TPP. Furthermore, TPO was added as a photoinitiator (1%), and MeHQ (0.05%) as a stabilizer. The biobased content of the formulation is also shown in Table 2, including the percentage of biobased material for the oligomer, the diluent, and the overall quantity, estimated as the percentage in weight of the components of biobased origin. The formulations were based on previous formulations for SLA and DLP printers [33,34,37]. The compatibility of these resins with TPP was subsequently studied through the fabrication of rectangular meshes, analysing the influence of laser pulse energy and scanning speed on the lateral and vertical resolution of the fabricated lines, as shown in Figure 1. The meshes were fabricated with the specialized system available at AIMEN and described in the Materials and Methods Section. Additionally, the same mesh was fabricated using a well-known commercial resin (Ormocomp©) as a benchmark.
As mentioned above, the main fabrication parameters that were considered for this work were the laser pulse energy and scanning speed, since they are the most relevant parameters in TPP; the outcome of the experiments for each of the provided formulations were analysed with the help of a confocal microscope. As an example for these experiments the results for FORM-02 are shown in Figure 1. The polymerization trend is similar for all the formulations within the parameter window used for this study (with the only difference being the polymerization threshold and efficiency, which depended on the particular formulation). The experiments for all the other formulations are shown in the supporting information. As can be observed in Figure 1, the thickness of the fabricated lines increases with the pulse energy and decreases with the scanning speed, as expected, since the laser dose received in a specific volume increases with the pulse energy and decreases with the scanning speed. It becomes apparent in the images in Figure 1 that the optimal processing window is quite tight, since small increases in pulse energy, or decreases on scanning speed, led to the appearance of much thicker lines and, even to crosslinking between adjacent lines. On the contrary, a combination of fast scanning speeds, above 500 µm/s, and lower pulse energies, below 20 nJ, led to the fabrication of very narrow but non-uniform lines and, in some cases, to the loss of the printed structures during cleaning due to a low adhesion to the substrate. The combination of parameters that led to a non-adequate polymerization (either by over or sub-polymerization) are highlighted with red contoured meshes in Figure 1. However, it is interesting to note that the lower radiation dose caused by the increase in scanning speed up to the mm/s range could be compensated by the increase in pulse energy, allowing the fabrication of continuous and uniform lines with a higher throughput. In fact, looking at the meshes corresponding to the diagonals of the figure, they have a similar appearance, demonstrating that faster fabrication throughputs can be achieved by the combined increase of both parameters: pulse energy and scanning speed. These tendences, are confirmed by looking in detail at the width of the written lines inside the meshed structures (Figure 2). As can be seen in the figure, the line width increases with the pulse energy and decreases with the scanning speed.
The height of the written lines follows a similar trend to their width, as can be seen in Figure 3. The line height increases with the pulse energy, while decreasing with the scanning speed. The consistency of this behaviour confirms not only the lateral but also the vertical resolution of the fabrication can be effectively controlled by adjusting the laser pulse energy and scanning speed. These results also demonstrate that the fabrication throughput can be increased via a simultaneous increment of both pulse energy and scanning speed. However, it should be noted that the maximum height of the written lines varied depending on the resin formulation. The resins that provided a better control of the vertical resolution were the formulations based on the PREPOL-01 prepolymer, with IBOA or a 1:1 mixture of ACMO and IBOA as diluent (see Figure 4). Those formulations allowed the fabrication of structures with a height up to 8 and 5 µm, respectively, by optimizing the pulse energy and fabrication speed. The formulation based on the PREPOL-02 prepolymer provided a good control of the height of the fabricated lines as well, even if not as accurate as the formulations based on the PREPOL-01 prepolymer. The other formulations did not allow the fabrication of lines with a height and uniformity good enough for 3D fabrication, which ruled them out for TPP (see supporting information for the printing results of the other formulations). This was an unfortunate outcome, since the other three formulations (FORM-01, FORM-04, and FORM-06) were the ones that presented a higher biobased content, as can be seen in Figure 4. Comparing the formulations, it can be seen that ACMO in FORM-02 does have a beneficial effect on the printing performance compared to FORM-03 where only IBOA is used. However, the resins also seem to have a considerable influence on the outcome of the TPP process. Although all formulations, with the exception of FORM-02, are based on IBOA only, the difference in performance is quite significant, which can then only be associated with the composition of the prepolymers. PREPOL-01 and PREPOL-002 were synthesized from different monomers. While PREPOL-01 is composed of very rigid building blocks, like the cyclic isophthalic acid and the branched NPG, PREPOL-01 consists mainly of more flexible chains, such as sebacic acid and the biobased polyether Velvetol 2000. Nonetheless, FORM-03 and FORM-05 show similar behavior in the vertical growth during the TPP process, while PREPOL-03–05 show inferior performance. The reasons behind this effect are not fully understood. However, one explanation could be a difference in the molar ratio of itaconic acid to the other monomers, which is lower for PREPOL-03–05.
A second batch of resins was formulated based on these results, with the aim of having good control of the polymerized height, while having the highest biobased content possible. These resins were based on a slight variation of the FORM-05 variant, since it was the resin that provided the best height control with a biobased material percentage over 70%. In this case, the aim of the study was the analysis of the influence of the concentration of ACMO and IBOA reactive diluents in the formulation for a given prepolymer, in this case the PREPOL-02, as one of the most promising base materials. The formulation of this second batch of resins can be seen in Table 3. The biobased content of these formulations was in a range between 37.3% for the sample with ACMO as diluent, and 72% for the sample with IBOA as diluent. Therefore, the difference in percentage of biobased material was mostly attributed to the concentration of biobased diluent, since the other components had the same properties for all formulations. An additional variation of the FORM-05 formulation was prepared with an increased content of PI, to check if this increment could lead to an increased height in the fabricated lines.
These new formulations were tested following the same procedure that was carried out with the first batch of resins, fabricating a matrix of meshed structures with increasing laser pulse energy and scanning speed. There was no significant difference in the lateral resolution of the lines written on the mesh with a 1.0% concentration of PI. However, the introduction of ACMO in the formulation lead to a slight increase in the polymerization threshold. While a pulse energy of 3.7 × 10−3 µJ was enough to start writing lines at a scanning speed of 0.10 mm/s on the samples containing only IBOA as a diluent, 1.0 × 10−2 µJ were required for the samples containing ACMO to maintain the fabricating speed. This trend seems to agree with the maximum height of the lines fabricated with these formulations, as can be seen in Figure 5. Amongst the formulations with a 1.0% PI concentration, the resin that only contained IBOA allowed better control of the line’s height and uniformity.
On the other side, the addition of an extra 1% concentration of PI led to a reduction in the lateral resolution of the fabricated features. The increase in PI promoted crosslinking between adjacent lines, particularly on the crossing sections, leading to the fabrication of thick lines with blurred intersections, even with laser powers slightly over the photopolymerization threshold. Therefore, it seems that the PI concentration should not exceed 1% for these formulations, while the most adequate diluent for TPP resins would be IBOA, or at least the diluent should contain IBOA in the mixture.
Following the results found for these two batches of resins, a final set of two resins was formulated (see Table 4) and tested for 3D printing fabrication. One of the selected prepolymers was PREPOL-1, which presented very good results, (as shown in Figure 4), which was mixed with IBOA to get the highest biobased content possible. A similar prepolymer with a higher biobased content was prepared by replacing the petrochemical HDO with 1,3-PDO (PREPOL-06), which is commercially available from renewable resources. This prepolymer was combined with a 50% mixture of ACMO and IBOA, shown in Table 4. The fabrication of the meshed structures was successful for both formulations, with a good control of the lateral and vertical resolutions, making them good candidates for 3D fabrication, which again could be related to the higher molar ratio of itaconic acid in the prepolymer. Due to these promising results, further TPP experiments were conducted via the fabrication of two different kinds of actual 3D microstructures: woodpile structures and micropyramids.
The first design that was selected for 3D fabrication was a woodpile structure, which is the usual benchmark for TPP due to its strong interest for photonics [40]. The woodpile structure was fabricated with a lateral size of 100 µm, a pulse energy of 1.5 µJ, and a scanning speed of 15 µm/s in a commercial TPP machine (µFAB). The design file of the structure was introduced to the software of the machine, and then sliced with an interlayer of 1 µm.
This kind of microstructure was fabricated with the last two formulations with different outcomes (Figure 6). The formulation FORM-07-B promoted the fabrication of the woodpile structure, with separated cylindrical features, but the achieved vertical resolution did not allow a good separation between consecutive cylindrical layers, resulting in a partial polymerization of the resin in the areas between cylinders when the distance between consecutive layers and adjacent cylinders was reduced, as can be clearly seen on the bottom image of Figure 6. The other formulation, FORM-07-A, favored the fabrication of very well-defined woodpile structure, visible on the top image and profile of the same Figure 6. In this latter case, there was no evidence of crosslinking between the adjacent cylinders, not even between consecutive layers, demonstrating not only a more than acceptable resolution for 3D printing via TPP but also a good repeatability between consecutive layers. It is worthy noticing, however, that the fabrication of separated structures required a larger interlayer and distance between cylinders in this latter case, indicating that targeting higher resolutions would require a fine tuning of the selected resins.
These results were confirmed through the fabrication of arrays of pyramidal structures with the FORM-07-A formulation (Figure 7), with the aim of analysing the robustness of the fabricated structures with a closed structure. In this case, a smaller slicing distance was used (1 µm) to check the vertical resolution for the fabrication of stepped 3D structures, like the case of the micropyramids.
As can be seen in Figure 7, pyramids with a lateral size in the range of 20 µm and a height around 10 µm were fabricated with a good repeatability, demonstrating that biobased resins could be suitable for 3D fabrication through TPP with resolutions within the micron range.

4. Conclusions

The presented findings demonstrate that formulations with biobased prepolymers from itaconic acid, commercial reactive diluents, photo initiators, and inhibitors can be used for two-photon polymerization (TPP). The fabrication of structures with sizes within the micron range and a controlled height within the range of a very few microns is possible by optimization of manufacturing parameters and changes in both the prepolymer and formulations. While an excess of the crosslinking effect can occur in the areas surrounding the fabrication lines, it can be controlled by tuning the formulation and incorporating an adequate concentration of photo initiator. Moreover, the pulse energy and scanning speed can be tuned to achieve the targeted resolution with a higher throughput, demonstrating the scalability of the process. The fabrication of 3D microstructures is feasible, as demonstrated by the fabrication of woodpiles and pyramidal structures.
In summary, the results of this work demonstrate that resins based on biobased formulations, originally designed for UV-curing 3D printing, can be adapted for 3D fabrication through TPP with resolutions over one order of magnitude higher.

Author Contributions

Conceptualization, F.G. and T.R.; validation, J.C. and S.V.; investigation, J.C., S.V. and N.M.S.; resources, N.M.S. and T.R.; writing—original draft preparation, F.G.; writing—review and editing, J.C., S.V., N.O. and T.R.; visualization, N.O.; supervision, F.G.; project administration, N.O. and T.R.; funding acquisition, N.O. and T.R. All authors have read and agreed to the published version of the manuscript.

Funding

This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 952941. BIOMAC is an Innovation Action (IA) started in January 2021 that will run until December 2024. The project’s EU contribution is € 14,807,314,50 on a total budget of € 16,596,702,50.Jmmp 09 00089 i001

Data Availability Statement

The original data presented in the study are openly available in ZENODO at https://doi.org/10.5281/zenodo.14651125.

Conflicts of Interest

The authors declare no conflicts of interest.

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Scheme 1. Overview over the synthesis of the itaconic acid-based polyesters and monomers used.
Scheme 1. Overview over the synthesis of the itaconic acid-based polyesters and monomers used.
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Figure 1. Meshes fabricated with formulation FORM-02 at different pulse energies (3.7–49.2 nJ) and scanning speeds (50–1000 µm/s).
Figure 1. Meshes fabricated with formulation FORM-02 at different pulse energies (3.7–49.2 nJ) and scanning speeds (50–1000 µm/s).
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Figure 2. Width of the written line as a function of the pulse energy and scanning speed.
Figure 2. Width of the written line as a function of the pulse energy and scanning speed.
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Figure 3. Height of the written line as a function of the pulse energy and scanning speed.
Figure 3. Height of the written line as a function of the pulse energy and scanning speed.
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Figure 4. Vertical growth with the biobased content.
Figure 4. Vertical growth with the biobased content.
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Figure 5. Maximum height of the new set of resins (formulations FORM-05- A to F) and overall biobased content.
Figure 5. Maximum height of the new set of resins (formulations FORM-05- A to F) and overall biobased content.
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Figure 6. Top image and profile of the woodpile structure fabricated with the FORM-07-A (top) and FORM-07-B (bottom) resins.
Figure 6. Top image and profile of the woodpile structure fabricated with the FORM-07-A (top) and FORM-07-B (bottom) resins.
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Figure 7. Pyramids fabricated with the FORM-07-A resin.
Figure 7. Pyramids fabricated with the FORM-07-A resin.
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Table 1. Composition and biobased content of the prepolymers used in this study.
Table 1. Composition and biobased content of the prepolymers used in this study.
PrepolymerItaconic Acid [eq]Acid 2
[eq]		Diol 1
[eq]		Diol 2
[eq]		Diol 3
[eq]		Biobased Content [%]
PREPOL-010.80.2 IPA1.0 HDO0.25 NPG-37
PREPOL -020.70.3 SebA1.22 HDO-0.14 Velv75
PREPOL -030.50.5 SA1.05
1.3-PDO		0.27 EDO0.027 Velv100
PREPOL -040.50.5 SA1.05
1.3-PDO		0.27
1.2-PDO		0.027 Velv100
PREPOL -050.50.5 SebA1.3-PDO-0.15 Velv100
PREPOL -060.80.2 IPA1.08 PDO0.27 NPG-89
IPA = isophthalic acid, Seb = sebacic acid, SA = succinic acid, HDO = 1,6-hexanediol, 1,2-PDO = 1,2-propanediol, 1,3-PDO = 1,3-propanediol, NPG = neopentylglycol, EDO = ethyleneglycol, Velv = Velvetol 2000.
Table 2. Formulation of the resins and related biobased content.
Table 2. Formulation of the resins and related biobased content.
FormulationPrepolymer
50%		Reactive Diluent
48.95%		Photoinitiator
(TPO)		Inhibitor
(MeHQ)		Biobased Content (%)
OligomerDiluentOverall
FORM-01PREPOL-03IBOA1.0%0.05%1007185
FORM-02PREPOL-01ACMO/IBOA 1:11.0%0.05%373636
FORM-03PREPOL-01IBOA1.0%0.05%377153
FORM-04PREPOL-04IBOA1.0%0.05%1007185
FORM-05PREPOL-02IBOA1.0%0.05%757172
FORM-06PREPOL-05IBOA1.0%0.05%1007185
Table 3. Formulation of the second set of resins and biobased content.
Table 3. Formulation of the second set of resins and biobased content.
NamePrepolymer
50%		Reactive Diluent
48.95%		Photoinitiator
(TPO)		Inhibitor
(MeHQ)		Biobased Content (%)
OligomerDiluentOverall
FORM-05-APREPOL-02IBOA1.0%0.05757172
FORM-05-BPREPOL-02ACMO1.0%0.0574.6037.3
FORM-05-CPREPOL-02ACMO/IBOA 1:11.0%0.0574.635.554.7
FORM-05-DPREPOL-02ACMO/IBOA 1:31.0%0.0574.653.263.4
FORM-05-EPREPOL-02ACMO/IBOA 1:31.0%0.0574.617.846.0
FORM-05-FPREPOL-02IBOA2.0%0.0574.67171.3
Table 4. Final set of resin formulations for 3D fabrication through TPP.
Table 4. Final set of resin formulations for 3D fabrication through TPP.
NamePrepolymer
50%		Reactive Diluent
48.95%		Photoinitiator
(TPO)		Biobased Content (%)
OligomerDiluentOverall
FORM-07-APREPOL-06ACMO/IBOA 1:11.0%753655
FORM-07-BPREPOL-01IBOA1.0%757172
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MDPI and ACS Style

Gontad, F.; Cuartero, J.; Vidal, S.; Otero, N.; Schulz, N.M.; Robert, T. Use of Biobased Resins Derived from Renewable Monomers for Sustainable 3D Fabrication Through Two-Photon Polymerization. J. Manuf. Mater. Process. 2025, 9, 89. https://doi.org/10.3390/jmmp9030089

AMA Style

Gontad F, Cuartero J, Vidal S, Otero N, Schulz NM, Robert T. Use of Biobased Resins Derived from Renewable Monomers for Sustainable 3D Fabrication Through Two-Photon Polymerization. Journal of Manufacturing and Materials Processing. 2025; 9(3):89. https://doi.org/10.3390/jmmp9030089

Chicago/Turabian Style

Gontad, Francisco, Jaime Cuartero, Sara Vidal, Nerea Otero, Natalia M. Schulz, and Tobias Robert. 2025. "Use of Biobased Resins Derived from Renewable Monomers for Sustainable 3D Fabrication Through Two-Photon Polymerization" Journal of Manufacturing and Materials Processing 9, no. 3: 89. https://doi.org/10.3390/jmmp9030089

APA Style

Gontad, F., Cuartero, J., Vidal, S., Otero, N., Schulz, N. M., & Robert, T. (2025). Use of Biobased Resins Derived from Renewable Monomers for Sustainable 3D Fabrication Through Two-Photon Polymerization. Journal of Manufacturing and Materials Processing, 9(3), 89. https://doi.org/10.3390/jmmp9030089

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