A
Optimization of the Photocatalytic Testing Setup Using FDM 3D Printing TechnologyAfrodytaDaskalakis1✉Emailafrodyta.daskalakis@pwr.edu.pl
PatrycjaSuchorska-Woźniak1Emailwozniak@pwr.edu.pl
RyszardKorbutowicz1Emailryszard.korbutowicz@pwr.edu.pl
OlgaRac-Rumijowska1Emailrumijowska@pwr.edu.pl
1Faculty of Electronics, Photonics and MicrosystemsWroclaw University of Science and TechnologyWybrzeże Wyspiańskiego 2750-370WroclawPoland
Afrodyta Daskalakis
1*, Patrycja Suchorska-Woźniak
1, Ryszard Korbutowicz
1, Olga Rac-Rumijowska
1
1 Faculty of Electronics, Photonics and Microsystems, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wroclaw, 50–370, Poland.
*Corresponding author(s). E-mail(s): afrodyta.daskalakis@pwr.edu.pl;
Contributing authors: patrycja.suchorska-wozniak@pwr.edu.pl;
ryszard.korbutowicz@pwr.edu.pl; olga.rac-rumijowska@pwr.edu.pl;
ORCID: AD 0009-0001-2003-8992; PSW 0000-0001-9246-0722; RK 0000-0002-4529-6533; ORR 0000-0002-8740-6817;
Abstract
This paper presents an evaluation of the suitability of various thermoplastic materials (ASA, PC/ABS, PETG/GF) for 3D printing (Fused Deposition Modelling method) of holders designed to secure thin silicon, and other substrates, with active materials for use in photocatalytic degradation of organic compounds in aqueous solutions. To minimize the impact of the holder on the photocatalysis process, the physicochemical and mechanical properties of the printed components were analysed. The results showed that the PETG/GF filament has minimal interaction with reactive media, strong chemical and UV resistance, and desirable mechanical properties. After analysing the test results, it was decided to use these materials to produce the holder. The FDM-designed and fabricated flower-shaped holder, constructed from PETG/GF, resulted in an over 20% increase in photocatalytic process efficiency. This improvement was attributed to both the increased active surface area of the photocatalyst and the optimized geometry, which enhanced light exposure and solution mixing.
Keywords:
Additive Manufacturing
Fused Deposition Modelling
Thin films
Ga2O3
Photocatalysis
Optimization
A
1 Introduction
3D printing, also known as Additive Manufacturing (AM), involves the production of objects through the incremental (additive) deposition of material layers. The term AM encompasses a wide range of manufacturing methods, and according to the classification by the American Society for Testing and Materials (ASTM), seven main groups of 3D printing technologies can be distinguished [1]. These are:
Fused Deposition Modeling (FDM) / Fused Filament Fabrication (FFF), which involves extruding molten thermoplastic filament layer by layer,
Stereolithography (SLA)/Digital Light Processing (DLP), which uses a laser or light [2–4] projector to photopolymerize liquid resin,
Selective Laser Sintering (SLS) / Selective Laser Melting (SLM), which sinters or fully melts metal or polymer powder with a laser beam,
Binder Jetting, which deposits a liquid binder onto a powder bed,
Material Jetting (MJ), which jets droplets of material onto a build platform,
Sheet Lamination (SL), which bonds thin sheets of material layer upon layer,
Directed Energy Deposition (DED), which feeds and concurrently melts material using a focused energy source.
Initially, 3D printing was primarily used for rapid prototyping; however, it is now applied across a wide range of industries, ranging from automotive and aerospace to construction, education, and even medicine (e.g. printing personalized implants or anatomical models). Due to the broad availability of various materials used in 3D printing and the relatively simple operation of 3D printers, these techniques are widely employed to produce functional components with diverse shapes and requirements. For instance, in mechanical engineering, printers are used to create tooling and spare parts, in robotics: components for housings and grippers, and in bioengineering: tissue scaffolds and organ models [1–4].
Analysis of the test results for prints made from PETG and glass-fiber reinforced PETG (Z-GLASS), conducted according to ISO 527-2, shows that the fiber reinforcement significantly increases the material’s stiffness and strength, directly demonstrating its suitability for printing components with complex geometries [5].
One of the key advantages of the most widely used 3D printing technology – FDM – is the extensive range of thermoplastic filaments available: from standard polymers (PLA, ABS, PETG) and engineering-grade materials (ASA, PC, PA) to high-performance and modified polymers (PEEK, PSU, etc.), as well as fiber-reinforced and functionally filled composites (e.g., PCABS, PETG/GA). Each material exhibits its own set of characteristics: mechanical strength, flexibility, thermal and chemical resistance, UV stability, and so on. Because printed parts are subjected to varying operating conditions and demand different levels of mechanical and physicochemical performance, material selection (e.g., choosing the right filament) should be guided by the print’s intended application [2–6]. For low-load prototyping, biodegradable PLA (Polylactic Acid) is often used. It prints easily, but parts made from this polymer have low heat resistance and begin to deform at around 50°C. In engineering applications, ABS (Acrylonitrile-Butadiene-Styrene) is chosen more often due to its higher mechanical strength and thermal stability. Unfortunately, ABS degrades under prolonged exposure to UV light. When exposed to sunlight, it rapidly loses impact resistance and also undergoes degradation and discoloration. ASA filament (Acrylonitrile-Styrene-Acrylate) offers mechanical properties similar to ABS but with far greater outdoor durability. According to Prusament ASA documentation[7] and tests by manufacturers such as Bambu Lab[8] and Zortrax [9], ASA retains its colour, mechanical strength, and structural integrity even after prolonged UV exposure. Polycarbonate (PC) filaments and their blends offer superior heat resistance, but printing with pure PC can be challenging due to its tendency to warp. For this reason, PC composites with dimensional-stabilizing additives, such as PC/ABS-are commonly used. The PC/ABS composite combines the benefits of both PC and ABS: it delivers the impact strength and thermal resistance of polycarbonate while retaining the processability of ABS [10–12]. Its UV resistance, however, depends primarily on the presence of stabilizers and antioxidants. Technical data from TitanX[12] and Zortrax[13] show that PC/ABS formulations incorporate a range of additives to improve UV resistance. Nevertheless, studies by Amza et al.[10, 14] have demonstrated that even short-term exposure to UV-C radiation (254 nm) causes microscopic structural changes. Another material offering good chemical resistance, high transparency and ease of printing is PETG (Polyethylene-terephthalate-glycol). It exhibits only moderate UV resistance [15]. Accelerated aging tests have shown that PETG’s tensile strength decreases by 36 % after 24 hours of UV-B exposure. Improed UV stability has been achieved by producing a glass-fiber-reinforced composite (PETG/GF). The French manufacturer Nanovia even markets its composite under the name “PETG GF UV,” explicitly stating its UV resistance [16], much like Z-GLASS from Zortrax [17]. In the technical datasheet it is emphasized that PETG-GF is “reinforced with glass fibers and UV stabilizers” [16, 17]. Analysis of tensile test results performed on printed samples of neat PETG and glass-fiber-reinforced PETG (Z-GLASS) according to ISO 527-2, shows that the addition of glass fibers substantially increases both stiffness and strength of the material, directly indicating its suitability for printing parts with complex geometries [15].
Manufacturing parts with 3D printing offers numerous advantages over traditional production methods. It allows the production of components with intricate geometries, tight tolerances, and precisely controlled internal structures (e.g., pore size and distribution) in a relatively fast and cost-effective way. The additive process delivers virtually unlimited design freedom, enables the integration of multiple materials within a single part, and cuts down on material waste by depositing only what’s needed where it’s needed. What’s more, AM makes it possible to fabricate components on demand and tailor them to specific applications [2–4].
There is a growing interest in 3D-printing techniques within chemical engineering and environmental protection. For example, 3D printing is now being used to design specialized chemical reactors and components for water treatment via photocatalysis. Typical photocatalysts in water-treatment processes, such as TiO₂ [18–22] or ZnO [23, 24] are usually employed in powder form because of their high specific surface area. However, handling powders requires separating them from the treated water afterwards, which adds both cost and time, and the recovery yield is never 100 %. One effectie way to overcome this is to immobilize the photocatalyst powder directly onto the surface of 3D-printed parts [25, 26].
In 2016, an FDM-printed microreactor with Au/TiO₂ photocatalyst microchannels was successfully used for hydrogen production [27]. Since then, research has focused on using additive technologies in photocatalysis, mainly involving the immobilization of TiO₂ powder on surfaces or within polymer parts [27]. For instance, Zhou et al.[28] used FDM to create a flow reactor with TiO₂-coated undulating channels, enhancing contaminant degradation and process reproducibility. Similarly, Son et al.[29] printed an ABS scaffold via FDM and hydrothermally grew ZnO nanostructures on it, improving reaction conditions and creating a durable photocatalyst. Additionally, bespoke holders have been designed to ensure stable substrate placement within reactors.
In our team, we are carrying out innovative research on the use of gallium-oxide layers deposited onto silicon substrates (thickness 500 µm) for the photocatalytic degradation of pollutants. Analyzing the phenomena at the surface of this material demands reproducible, tightly controlled process conditions. We study the kinetics of this process using both spectrophotometry and impedance spectroscopy. The latter technique enables us to follow the degradation kinetics of organic compounds by monitoring changes in the solution’s conductivity during photocatalysis. Consequently, it is vital to minimize any influence of the sample holder on the photocatalytic reaction. In previous work, quartz holders, which are costly and mechanically fragile, have been used. Moreover, achieving a stable mounting of silicon substrates and correctly orienting them to ensure efficient interaction between the electromagnetic radiation and the photocatalyst surface proved cumbersome. For this reason, we set out to evaluate the feasibility of using thermoplastic materials to fabricate a holder that would overcome these limitations. Drawing on literature data, we selected three FDM-compatible thermoplastics: ASA, PC/ABS, and glass-fiber-reinforced PETG (PETG/GF). Our analysis demonstrated that both the precise design of the holder’s geometry and the choice of an appropriate filament significantly enhance the efficiency and reproducibility of the photocatalytic process. Using optimally designed holders printed from PETG/GF doubled the dye degradation rate. This improvement cannot be attributed solely to a greater amount of photocatalyst but also to more effective interaction between the radiation and the active material, as well as improved mixing within the solution.
2 Materials and Methods
2.1 Chemicals and materials
The experiments were carried out using deionized water (Milli-Q Millipore, 18.2 MΩ·cm). Methylene blue (aniline, CAS:28983-56-4) (CHEMPUR) served as the model indicator dye. Between experiments, all laboratory glassware was cleaned by immersion in a chromic acid (H₂CrO₄) and sulfuric acid (H₂SO₄) solution, then thoroughly rinsed with ultrapure deionized water (18.2 MΩ·cm). Square samples (20 mm × 20 mm × 2 mm) were printed for physicochemical characterization, while dogbone-shaped samples were produced for mechanical testing following ISO 527, using a CS2-1100 force tester (Chatillon, AMETEK Group).
2.2 FDM materials
Based on an evaluation of FDM materials from various manufacturers, three commercial filaments were selected for this study: ASA (Acrylonitrile-styrene-acrylate), PETG/GF “GLASS” (Polyethylene-terephthalate-glycol reinforced with glass fiber), and PC/ABS (Polycarbonate-acrylonitrile-butadiene-styrene), all sourced from Zortrax® (Poland) (Table 1). These materials were chosen for their unique physicochemical properties, which can critically influence the performance and efficiency of photocatalytic degradation of organic compounds.
ASA (Acrylonitrile-styrene-acrylate) [7–9] – this material exhibits exceptional resistance to weathering, UV radiation, and chemical agents. Consequently, it is widely employed in environments with high solar exposure.
PC/ABS (Polycarbonate-acrylonitrile-butadiene-styrene)[10–13] – this material combines the high mechanical strength characteristic of polycarbonate with the excellent impact resistance and chemical stability of ABS. It is widely used in materials engineering, particularly in applications that demand both robust mechanical performance and long-term environmental durability.
PETG/GF – (Polyethylene terephthalate glycol with glass fiber) [15–17] – this glass-fiber-reinforced filament was engineered for prototyping “glass-like” parts with intricate geometries. It is low shrinkage, ensures defect-free prints, while the finished components exhibit excellent scratch resistance and long-term UV stability. PETG/GF prints have a semi-transparent appearance and retain their structural integrity even after exposure to most acids, alcohols, or mild bases.
Parameter | ASA | PETG/GF | PC/ABS |
|---|---|---|---|
Density [g/cm³] | 1.18 | 1.41 | 1.14 |
UV resistance | High | Medium | Medium |
Mechanical tensile strength [MPa] | 24.21 | 39.57 | 36.89 |
Guaranteed elongation at break | 2.76% | 5.94% | 8.56% |
Specific density [g/cm3] | 1.176 | 1.409 | 1.139 |
Chemical stability | Good | Very good | Average |
Color | Blue | Translucent | Ivory |
Melting point [°C] | 140–170 | No data available | No data available |
Glass transition temperature [°C] | 80.99 | 78.06 | 104.10 |
Remarks | UV resistant | resistant to salts, acids, and bases | resistant to salts, acids, bases, and solvents |
2.3 FDM printing processes
These filaments were used to make square fittings and “bones” (ISO 527) based on models designed in Inventor (Autodesk). The square prints were tested to determine:
UV resistance,
the rate at which plasticizers are washed out into water,
absorption and desorption of dye.
All geometries were designed in Autodesk Inventor and exported in STL format (Standard Tessellation Language). Samples were fabricated using a Zortrax M200 3D printer (Table 2) [30], renowned for its high precision and compatibility with a wide range of thermoplastic materials. Filaments with a 1.75 mm diameter were employed, ensuring stable extrusion and excellent surface finish. Printing parameters were optimized and configured in Z-SUITE 2.0, allowing precise control over infill density, layer thickness, and extrusion temperature.
Parameter | Information |
|---|---|
Printing technology | FDM |
Material | Filament |
Layer resolution | 90–390 µm |
Minimum wall thickness | 400 µm |
Working area | 200 x 200 x 180 mm |
Nozzle diameter | 0.4 mm |
Software | Z-SUITE |
Filament diameter | 1.75 mm |
Heated bed | Yes |
Cooling | Yes |
Maximum printing temperature | 290°C |
Maximum bed temperature | 105°C |
The dogbone samples for mechanical testing were fabricated by the PN-EN ISO 527 standard [5], which defines standard methods for assessing the mechanical properties of plastics, particularly their tensile strength. All other samples were printed as 20 mm × 20 mm squares with a 2 mm thickness. Two series of samples were prepared for each type of test.
To carry out a rigorous evaluation of their actual suitability as a construction material for photocatalytic-layer substrate holders, tests were performed using materials intended for the conventional Zortrax M200 printer [9, 13, 17, 30]. All components (including the final holder) were designed in Autodesk Inventor and printed with 20 % infill, a 0.9 mm layer height, a 0.4 mm nozzle diameter, and a print speed of 10 mm/s.
2.4 Test setup for photocatalytic degradation of organic compounds
The photocatalytic activity of the structures was assessed by monitoring the degradation of methylene blue (MB) under UV irradiation. The photoreactor setup (Fig. 1) was engineered to optimize the exposure of the dye solution to the catalyst. Six Philips UV lamps (model TL44/D25/09N, 15 W, HP3205 fixture) emitting at 280–360 nm (λmax ≈ 365 nm) served as the light source. Illumination was provided exclusively from above, and the chamber walls and floor were lined with aluminum foil to maximize reflectance. A water-jacketed reactor was used to stabilize the temperature throughout the degradation process. The distance between the UV lamps and the bottom of the beaker was maintained at 36 cm. The methylene blue solution was stirred with a magnetic stirrer to ensure uniform contact with the catalyst.
Fig. 1
Diagram of the setup used for photocatalytic degradation of pollutants in liquid form
2.5 Test procedures and experiment
Based on literature data and our own research, the criteria that the structural material for components used in the photocatalytic process must meet have been defined. This material should be, above all, resistant to prolonged exposure to ultraviolet radiation. Furthermore, it must not leach any chemical compounds that could affect the kinetics of the process under study or the conductivity of the solution. The material’s surface should not adsorb the dye, and any process residues should be easy to remove. As for mechanical properties, the fabricated elements must retain the necessary characteristics to ensure stable mounting of the substrates.
The UV resistance of the materials was tested by printing square shapes with sides measuring 20 mm and a thickness of 2 mm. These were exposed to UV-A radiation for 5 hours per day for 7 days. Prior to each exposure process, the elasticity of the prints was checked manually.
To assess dye adsorption and the retention of process residues on the specimen surfaces, the prints were submerged for 48 h in 50 mL of methylene blue solution at concentrations of 1 mg/dm³ and 100 mg/dm³. Samples were stored in the dark at room temperature.
After this time, they were visually assessed. At the same time, in order to check the adsorption of contaminants on the surface of the fittings, they were placed in separate beakers containing 50 ml of MB solution. The samples were kept in this solution for 3.5 hours – the duration corresponding to a typical photocatalytic reaction. Afterward, they were transferred into beakers containing 50 mL of pure deionized water and subjected to ultrasonic treatment for a predetermined time. Subsequently, absorbance (UV-Vis, 220–700 nm) and conductivity (impedance spectroscopy) measurements of the water were taken after 5, 15, and 30 minutes of ultrasonication. The effectiveness of the surface-cleaning process was then evaluated by transferring the samples, after 30 minutes of ultrasonication, into fresh deionized water and subjecting them to an additional 5-minute ultrasonic cycle. The purity of this rinse water was assessed by repeating the absorbance and conductivity measurements.
Tensile testing was conducted under a constant 10 N load. Dogbone samples, printed in accordance with PN-EN ISO 527, were used for these evaluations. Tests were performed on a CS2-1100 Force Tester (Chatillon, AMETEK Group), and the maximum stress (σₘₐₓ), strain (ε), and tensile strength (σₜ) were determined.
3 Results and discussion
3.1 Evaluation of material stability under UV exposure
The evaluation of material stability under UV-A exposure showed that the elasticity of none of the tested FDM prints (PC/ABS, ASA, PETG/GF) changed in any noticeable way. Likewise, no discoloration of the samples was detected after seven days of irradiation. These findings align with the materials’ datasheet specifications, confirming their suitability for producing wear parts in photocatalytic setups.
3.2 Contamination of the reaction medium
In the photocatalytic process, pollutants in the water are broken down, so it’s essential that structural components don’t introduce contaminants into the reaction medium. To assess this, we measured the electrical conductivity of DI water containing the printed samples after ultrasonication. The results (Fig. 2) show that the PC/ABS specimen caused the greatest contamination (Fig. 2a): conductivity rose sharply after just 5 min and remained high at 30 min, indicating leaching of ionic species. The ASA specimen (Fig. 2c) produced a moderate conductivity increase, whereas the PETG/GF specimen (Fig. 2b) showed no significant change in impedance even after 30 min. Thus, PETG/GF parts exhibit outstanding chemical stability.
Fig. 2
Bode plots of the impedance module of aqueous solutions following ultrasonic treatment at various time intervals: a) PC/ABS; b) PETG/GF; c) ASA; d) after 30 minutes
3.3 Evaluation of adsorption and surface cleaning of prints
Exposure of the FDM-printed samples to methylene blue (MB) solutions at 1 mg/dm³ and 100 mg/dm³ revealed marked differences in material behavior. Dye deposition occurred on all surfaces, and variations in stain persistence after rinsing were observed (Table 3). In every case, the higher MB concentration produced more pronounced surface discoloration, although the extent of this effect depended on the filament type. Prints made from more microporous filaments (PC/ABS and ASA) exhibited significant staining that persisted even after rinsing with deionized water, indicating durable adsorption or penetration of the dye into the material. In contrast, PETG/GF samples showed only a slight, uniform tint at the higher MB concentration, and after rinsing, only minor edge discoloration remained.
PC/ABS | ASA | PETG/GF | |
|---|---|---|---|
0 mg/dm3 |  |  |  |
1 mg/dm3 |  |  |  |
1 mg/dm3 after rinsing |  |  |  |
100 mg/dm3 |  |  |  |
100 mg/dm3 after rinsing |  |  |  |
The observations indicate that the susceptibility of the selected materials to surface dye adsorption depends on both their chemical composition and surface morphology. Prints with lower porosity and greater chemical stability, such as PETG/GF, are better suited for use in aqueous environments, especially where minimal contaminant sorption and easy surface cleaning are required.
Similar results were obtained when evaluating contaminant sorption and print cleaning by performing absorbance and impedance measurements (Fig. 4) on the solutions, following the procedure described above. The UV–Vis absorbance spectra of the methylene blue solutions in which the samples were immersed (Fig. 3a) show that all materials sequester part of the dye. The PETG/GF specimen exhibited the highest absorbance, whereas the ASA print showed the lowest, with an absorbance value nearly matching the reference (~ 0.075 a.u.), indicating minimal interaction with the dye.
Fig. 3
UV–Vis absorbance spectra of the pristine 1 mg/dm³ methyl blue solution and of solutions in which samples were immersed for 3.5 hours of: a) incubation materials; b) rinsing them in deionized water
Based on the absorbance values of the water after the additional rinse (Fig. 3b), it can be stated that PETG/GF demonstrates the best ability to remove contaminants from the print surface. The absorption spectrum of the solution following the two-step rinsing procedure (30 minutes rinse, followed by a water change and a further 5-minute rinse) almost perfectly overlaps with that of pure water across the entire wavelength range.
Analysis of the impedance magnitude (|Z|) versus frequency plots, recorded after a 3.5-hour exposure of the samples to methylene blue solution and subsequent rinsing in deionized water, revealed distinct differences in material performance (Fig. 4). The PC/ABS rinse solution (Fig. 4a) showed the lowest |Z| value, indicating substantial leaching of contaminants. In contrast, the PETG/GF specimen (Fig. 4b) was the least absorbent and cleaned most effectively in water. The ASA sample (Fig. 4c) displayed a cleaning profile similar to PETG/GF. Applying an additional ultrasonic rinse (30 min + 5 min) increased impedance values across all samples, with PETG/GF again exhibiting the highest |Z| post-rinse, demonstrating its superior resistance to contamination and ease of surface cleaning (Fig. 4e).
Fig. 4
Bode spectra of the impedance module of aqueous solutions after rinsing samples, previously immersed in a methyl blue solution (1 mg/dm³), at different time intervals: a) PC/ABS; b) PET-G/GF; c) ASA; d) after 30 minutes; e) after 30 + 5 minutes
The experimental results and subsequent analysis demonstrate that, of the materials tested, PETG/GF filament exerts the least interference with the photocatalytic process when used to manufacture the holder.
3.4 Assessment of mechanical properties
Tensile testing of the printed dogbone samples was carried out in accordance with PN-EN ISO 527 using a CS2-1100 Force Tester (Chatillon, AMETEK Group). The maximum stress (σₘₐₓ), strain (ε), and tensile strength (σₜ) were recorded.
The tensile tests revealed clear differences in strength and ductility among the materials (Fig. 5). The ASA specimen (Fig. 5b) exhibited a fibrous fracture surface, indicative of stable strength and moderate ductility. In contrast, the PETG/GF specimen (Fig. 5c) showed a relatively smooth break, suggesting higher deformability. The PC/ABS sample (Fig. 5d) fractured with a brittle break pattern, reflecting its limited plasticity.
Fig. 5
Photos of strength-test samples before and after breaking: a) printouts in accordance with ISO 527; b) ASA; c) PETG/GF d) PC/ABS
These findings align with the tensile test results (Fig. 5). The ASA samples exhibit high stiffness, while the PETG/GF and PC/ABS dogbone samples achieve greater strength under lower applied tensile loads.
Fig. 6
Stress-strain (σ-ε) tensile test curves
Based on the experimental results (Fig. 6), Young’s modulus (E) and the elongation at break (εb) were determined. Young’s modulus was calculated as the ratio of stress to strain within the elastic region:
1
where: σ- stress, ε- strain.
Elongation at break was determined based on the following relationship:
2
where:
ΔL– maximum deformation of the sample (mm),
L0– initial sample length (150 mm).
Material | Maximum stress σmax [N] | Tensile strength [MPa] | Maximum strain [mm] | Elongation at break [%] | Young’s modulus [MPa] |
|---|---|---|---|---|---|
ASA | 696.15 | 17.85 | 4.93 | 3.29 | 797.48 |
PETG/GF | 871.17 | 27.22 | 5.43 | 3.62 | 830.42 |
PC/ABS | 847.47 | 2173 | 4.7 | 3.13 | 945.35 |
Tensile test results (Table 4) showed that, of the three samples evaluated, the PETG/GF filament delivered the highest tensile strength, exceeding 870 N at failure, while also exhibiting the greatest elongation at break (3,62%). The PC/ABS sample displayed slightly lower strength and the least ductility, and the ASA specimen failed under the lowest breaking load. These findings demonstrate that PETG/GF prints offer the best compromise between strength and deformability, making them the most versatile material of those tested.
In summary, the experimental data show that PETG/GF prints combine the highest mechanical strength with the greatest elasticity. PC/ABS samples, while also strong, exhibited the most leaching of ionic species (as reflected in increased conductivity) and the highest methylene blue uptake. In contrast, PETG/GF parts demonstrated superior chemical stability, with minimal leaching and the easiest methylene blue removal. ASA prints displayed intermediate performance across all evaluated metrics.
Therefore, based on our material tests and the literature review [2–4, 8, 9, 11, 13, 15, 17, 30, 31]. We selected the Z-PETG/GF filament for FDM (Fused Deposition Modeling) printing of the holder. This filament offers outstanding chemical resistance, minimal dye uptake, and does not leach any contaminants into the reaction medium. Its composition comprises approximately 80 % glycol-modified polyethylene terehthalate (PETG), 8–12 % glass fiber, and up to 8 % additves and colorants.
4 Application
4.1 Holder design and construction
Designing the holder for the photocatalytic setup required careful consideration of several technical aspects:
compatibility of the design with the technological capabilities of the ZORTRAX M200 3D printer,
printing process parameters, including dimensional accuracy (layer thickness), nozzle diameter, printing speed, and, importantly, the adjustment of supports to the element,
the holder’s design must maximize the usable surface area of the reaction vessel while maintaining a geometry that ensures uniform illumination of the substrates and efficient circulation of the solution around the catalyst, thereby minimizing the formation of poorly mixed zones,
the holder must allow for easy placement of substrates while enabling unhindered insertion into and removal from the reactor without damaging the photocatalytic coating or the magnetic stir bar,
The holder was designed in Autodesk Inventor, considering the dimensional requirements and limitations of the Zortrax M200 3D printer. Its geometry optimizes the exposure angle for 2″ silicon wafers, cut in half with a β-Ga₂O₃ photocatalyst layer on one side. Precise substrate placement ensures uniform UV irradiance across the catalyst surface and effective circulation of the reaction solution under magnetic stirring. The design promotes homogeneous photocatalytic degradation over the entire Ga₂O₃ layer and within the quartz reaction vessel.
Several designs and prints of the holder were made, eliminating design/construction defects that appeared during the prototyping stage and adapting the designs to different process conditions. The difficulties encountered included, among others:
the print was not filled sufficiently, which resulted in the substrates rising during mixing of the solution,
no smooth mixing of the solution throughout the entire volume of the vessel.
These challenges were addressed during prototyping by increasing the print’s infill density. Instead of a flat platform, the holder was designed with a “flower” geometry: substrates are seated on the “petals,” whose raised edges prevent the substrates from slipping and ensure stable positioning (Fig. 7).
Fig. 7
Visualizations of the holders, supporting the substrate with a photocatalyst for illumination a) from above, b) from above and from the sides
Considering the option of lateral or top-down illumination, two holder variants were designed and fabricated (Fig. 7). Both holders provided:
secure and stable mounting of five half-inch 2″ silicon wafer substrates,
optimized UV-irradiation efficiency via inclined substrate positioning,
maximum catalyst–solution contact through strategically placed openings and channels allowing unrestricted fluid flow,
efficient mixing of the solution throughout the entire reactor volume,
unimpeded operation of the magnetic stir bar,
easy insertion and removal of the holder into and out of the reaction vessel.
4.2 Testing of the Modified Photocatalysis Setup
In earlier studies, a quartz holder was used that could secure only one half of a 2″ silicon wafer, providing a total active surface area of roughly 1000 mm². Under these conditions, methylene blue degradation reached just about 2% after 120 minutes, owing to the limited amount of active material (Fig. 8a).
Fig. 8
UV–Vis absorbance spectra of the degradation of a 2.5 mg/dm³ methyl blue solution using: a) quartz holders; b) PETG/GF filament holder
By using the custom-designed holder (Fig. 8b), we were able to mount five halves of 2″ silicon substrates simultaneously, providing a total active surface area of approximately 5 000 mm². This increased the catalyst’s specific surface area fivefold. Absorbance measurements were taken 15 to 150 minutes into the reaction. Over this period, the absorbance of the dye’s characteristic peak at ~ 600 nm decreased by roughly 25%.
Over time, a steady decline in absorbance was recorded, clearly indicating progressive degradation of the dye in solution. The observed decay of methylene blue confirms the effectiveness of the photocatalytic process. A critical analysis of the results demonstrated that using a holder fabricated from Z-PETG/GF filament improved overall process efficiency by more than 20%. This gain cannot be attributed solely to the increased amount of photocatalyst but also stems from enhanced UV-radiation coupling with the active material and more effective mixing of the reaction medium.
5 Conclusions
In studies of photocatalytic materials deposited on rigid substrates, ensuring proper substrate fixation is critically important. Investigating the surface phenomena of the active material demands reproducible, tightly controlled conditions. Consequently, any influence of the reactor’s structural components, including the substrate holder, on the photocatalytic process must be minimized. Although quartz holders have been used, they are costly, mechanically fragile, and make stable mounting and precise alignment of silicon substrates very difficult. Our evaluation of candidate thermoplastic materials (ASA, PC/ABS, PETG/GF) revealed that the following desirable properties:
the lowest contamination of the reaction environment,
the minimal sorption of contaminants onto their surfaces,
easy removal of contaminants from the surfaces,
are best provided by the samples fabricated from PETG/GF.
Aqueous solutions in contact with PETG/GF prints exhibited the highest impedance (i.e. the lowest ionic conductivity) and negligible residual MB dye absorbance. In contrast, PC/ABS prints caused the greatest water contamination, shown by the lowest impedance and highest dye absorbance, while ASA prints induced only moderate changes.
In tensile testing, PETG/GF exhibited the highest ultimate tensile strength and failed at the greatest elongation, underscoring its ability to absorb deformation under load. ASA showed a slightly lower breaking load, intermediate elongation at break, and the lowest Young’s modulus. PC/ABS fell between the two, with moderate tensile strength and the lowest elongation at fracture.
UV-A stability tests confirmed that all selected materials (ASA, PC/ABS, PETG/GF) remain stable under prolonged UV exposure, making them suitable for photocatalytic applications. In terms of chemical resistance, PETG/GF proved to be the most resistant – no visible discoloration or leaching of additives was observed after contact with water and dye. ASA and PC/ABS, by contrast, absorbed measurable amounts of dye and released soluble components into the water (particularly PC/ABS), indicating only moderate chemical stability. Taking into account all evaluation criteria (reaction-medium purity, mechanical performance, chemical resistance, and UV stability), the PETG/GF composite emerges as the optimal material for fabricating the photocatalytic holder.
A flower-shaped holder was designed and FDM-printed, and its impact on process efficiency was evaluated. Critical analysis of the data showed that overall efficiency increased by more than 20% when using the optimally designed holder made from Z-PETG/GF filament. Had this gain resulted solely from the increased photocatalyst loading, efficiency would have risen by only about 10%. Instead, the additional improvement clearly stems from the holder’s geometry, which enhances UV-radiation coupling with the active material and promotes more effective mixing of the solution.
A
A
A
Declarations•Funding: This work has been cofunded from statutory activities of Wroclaw University of Science and Technology; Faculty of Electronics, Photonics and Microsystems. The work was supported by the project Minigrants for doctoral students of the Wroclaw University of Science and Technology.
• Competing interests: The authors declare no competing interests.
• Ethics approval and consent to participate: Not applicable
• Consent for publication: All author’s confirmed that are aware of the content of the manuscript, take full responsibility for its integrity and agree to publication.
• Data availability: The sets of data developed and/or examined through the present research are available upon reasonable request from the corresponding author.
• Materials availability: Not applicable
• Code availability: Not applicable
• Author contribution: Afrodyta Daskalakis: Conceptualization, Methodology, Writing - Original Draft; Patrycja Suchorska-Woźniak: Conceptualization, Methodology, Writing - Review and Editing, Supervision; Ryszard Korbutowicz: Conceptualization, Methodology, Writing - Review and Editing, Supervision; Olga Rac-Rumijowska: Resources, Writing - Review and Editing
• Additional information: Thanks to Ms Aleksandra Lazarek for technical assistance.
Electronic Supplementary Material
Below is the link to the electronic supplementary material
References
1.
(2012) Standard Terminology for Additive Manufacturing Technologies. Advancing Standards Transforming Markets. https://store.astm.org/f2792-12a.html. accessed 25 August 2025
2.
Chen W, Zhang Y (2019) Development and application of 3D printing technology in various fields. J Phys: Conf Ser 1303(1):012032. https://doi.org/10.1088/1742-6596/1303/1/01203218
3.
Shahrubudin N, Lee TC, Ramlan R (2019) An overview on 3D printing technology: Technological, materials, and applications. Procedia Manuf 35:1286129. https://doi.org/10.1016/j.promfg.2019.06.089
4.
Dunham S, Mosadegh B, Romito EA et al (2018) Chap. 4 - applications of 3d printing. In: Al’Aref SJ, Mosadegh B, Dunham S et al (eds) 3D Printing Applications in Cardiovascular Medicine. Academic, Boston, pp 61–78
5.
(2021) BS EN ISO 527-5:2021 Plastics – Determination of tensile properties – Test conditions for unidirectional fibre-reinforced plastic composites,https://landingpage.bsigroup.com/LandingPage/Standard?UPI=000000000030409905. accessed 25 August 2025
6.
(2024) Heat-resistant 3D printing materials guide: Compare processes, materials, and applications. https://formlabs.com/eu/blog/heat-resistant-3d-printing/. accessed 25 August 2025
7.
(2024) Technical data sheet ASA Prusament. https://prusament.com/materials/prusament-asa/. accessed 25 August 2025
8.
(2023) Technical data sheet ASA Bambu. https://eu.store.bambulab.com/pl/products/asa-filament. accessed 25 August 2025
9.
(2021) Technical data sheet z-ASA Zortrax (in Polish). https://www.bing.com/search?q=z-asa%20material%20cataloge%20note. accessed 25 August 2025
10.
Amza CG, Zapciu A, Baciu F et al (2023) Effect of UV-C radiation on 3D printed ABS-PC polymers. Polymers 15:1966. https://doi.org/10.3390/polym15081966
11.
(2024) Technical data sheet PC-ABS SUNLU. https://www.sunlu.com/products/pc-abs-3d-printer-filament-high-performance-3d-filament-1kg. accessed 25 August 2025
12.
(2024) Technical data sheet – Formfutura Titanx PC-ABS. https://www.formfutura.com/shop/titanx-143. accessed 25 August 2025
13.
(2021) Technical data sheet z-PCABS Zortrax (in Polish). https://zortrax.com/pl/filaments/z-pcabs/. accessed 25 August 2025
14.
Amza CG, Zapciu A, Baciu F et al (2021) Aging of 3D printed polymers under sterilizing UV-C radiation. Polymers 13(24):4467. https://doi.org/10.3390/polym13244467
15.
Szykiedans K, Credo W, Osiński D (2017) Selected mechanical properties of PETG 3D prints. Procedia Eng 177:455–461. https://doi.org/10.1016/j.proeng.2017.02.24519
16.
(2024) Nanovia PETG-GF-UV technical data sheet. https://nanovia.tech/en/ref/nanovia-petg-gf-uv/. accessed 25 August 2025
17.
(2021) Technical data sheet z-glass Zortrax (in Polish). https://zortrax.com/pl/filaments/z-glass/. accessed 25 August 2025
18.
Ohno T, Sarukawa K, Tokieda K et al (2001) Morphology of a TiO2 photocatalyst (Degussa, P-25) consisting of anatase and rutile crystalline phases. J Catal 203(1):82–86. https://doi.org/10.1006/jcat.2001.3316
19.
Zielinńska B, Grzechulska J, Morawski AW (2003) Photocatalytic decomposition of textile dyes on TiO2-tytanpol A11 and TiO2-degussa p25. J Photochem Photobiol A: Chem 157:65–70. https://doi.org/10.1016/S1010-6030(03)00094-7
20.
Sevastaki M, Suchea MP, Kenanakis G (2020) 3D printed fully recycled TiO2-polystyrene nanocomposite photocatalysts for use against drug residues. Nanomaterials 10(11):2144. https://doi.org/10.3390/nano10112144
21.
Li L, Li J, Luo H et al (2022) Physicochemical and photocatalytic properties of 3D-printed TiO2/chitin/cellulose composite with ordered porous structures. Polymers 14(24):5435. https://doi.org/10.3390/polym14245435
22.
Kwon CH, Shin H, Kim JH et al (2004) Degradation of methylene blue via photocatalysis of titanium dioxide. Mater Chem Phys 86:78–82. https://doi.org/10.1016/j.matchemphys.2003.12.010
23.
Batra V, Kaur I, Pathania D et al (2022) Efficient dye degradation strategies using green synthesized ZnO-based nanoplatforms: A review. Appl Surf Sci Adv 11:100314. https://doi.org/10.1016/j.apsadv.2022.100314
24.
Muthirulan P, Meenakshisundararam M, Kannan N (2013) Beneficial role of ZnO photocatalyst supported with porous activated carbon for the mineralization of alizarin cyanin green dye in aqueous solution. J Adv Res 4:479–484. https://doi.org/10.1016/j.jare.2012.08.005
25.
Zhou R, Han R, Bingham M et al (2022) 3D printed, plastic photocatalytic flow reactors for water purification. Photochem Photobiol Sci 21:1585–1600. https://doi.org/10.1007/s43630-022-00242-y
26.
Yuan X, Sunyer-Pons N, Terrado A et al (2023) 3D-printed organic conjugated trimer for visible-light-driven photocatalytic applications. Chem Sus Chem. https://doi.org/10.1002/cssc.202202228
27.
Castedo A, Mendoza E, Angurell I et al (2016) Silicone microreactors for the photocatalytic generation of hydrogen. Catal Today 273:106–111. https://doi.org/10.1016/j.cattod.2016.02.05320
28.
Zhou W, Zhang P, Liu W (2012) Anatase TiO2 nanospindle/activated carbon (AC) composite photocatalysts with enhanced activity in removal of organic contaminant. Int J Photoenergy. https://doi.org/10.1155/2012/325902
29.
Son S, Jung P, Park J et al (2018) Customizable 3D-printed architecture with ZnO-based hierarchical structures for enhanced photocatalytic performance. Nanoscale 10:21696–21702. https://doi.org/10.1039/C8NR06788K
30.
(2021) Technical data sheet 3d printer Zortrax M200 (in Polish). https://support.zortrax.com/m-series-specification/. accessed 25 August 2025
31.
Abdullah FH, Abu Bakar NHH, Abu Bakar MA (2022) Current advancements on the fabrication, modification, and industrial application of zinc oxide as photocatalyst in the removal of organic and inorganic contaminants in aquatic systems. J Hazard Mater 424:127416. https://doi.org/10.1016/j.jhazmat.2021.127416
