Fabrication Of 3D Structures Research Articles

Periodic Arrays of Plasmonic Ag-Coated Multiscale 3D-Structures with SERS Activity: Fabrication, Modelling and Characterisation.

Surface enhanced Raman spectroscopy (SERS) is gaining importance as sensing tool. However, wide application of the SERS technique suffers mainly from limitations in terms of uniformity of the plasmonics structures and sensitivity for low concentrations of target analytes. In this work, we present SERS specimens based on periodic arrays of 3D-structures coated with silver, fabricated by silicon top-down micro and nanofabrication (10 mm × 10 mm footprint). Each 3D-structure is essentially an octahedron on top of a pyramid. The width of the top part-the octahedron-was varied from 0.7 µm to 5 µm. The smallest structures reached an analytical enhancement factor (AEF) of 3.9 × 107 with a relative standard deviation (RSD) below 20%. According to finite-difference time-domain (FDTD) simulations, the origin of this signal amplification lies in the strong localization of electromagnetic fields at the edges and surfaces of the octahedrons. Finally, the sensitivity of these SERS specimens was evaluated under close-to-reality conditions using a portable Raman spectrophotometer and monitoring of the three vibrational bands of 4-nitrobenzenethiol (4-NBT). Thus, this contribution deals with fabrication, characterization and simulation of multiscale 3D-structures with SERS activity.

Design and Fabrication of 3D‐Printed Lab‐On‐A‐Chip Devices for Fiber‐Based Optical Chromatography and Sorting

Microfluidic lab‐on‐a‐chip (LOC) devices have become essential tools for multitudes of applications in various research fields. 3D printing of microfluidic LOC devices offers many advantages over more traditional manufacturing processes, including rapid prototyping and single‐step fabrication of complex 3D structures. In this work, 3D‐printed microfluidic devices are designed and fabricated for optical chromatography and sorting. Optical chromatography is performed by inserting a single‐mode optical fiber into the device creating a counter‐propagating laser beam to the fluid flow. Particles are separated depending on refractive index and size. To demonstrate optical sorting, a cross‐type sorter 3D‐printed microfluidic device is fabricated that directs the laser beam perpendicular to the flow direction. Design features such as a sloping channel and a channel configuration for 3D hydrodynamic focusing (to aid in controlled sample flow and particle position) help to optimize sorting performance. Stable optofluidic trapping and sorting are successfully achieved using the fabricated microfluidic devices. These results highlight the tremendous potential of 3D printing of microfluidic LOC devices for applications aimed at the optofluidic manipulation of micron‐sized particles.

Nanoarchitectonics of Laser Induced MAX 3D‐Printed Electrode for Photo‐Electrocatalysis and Energy Storage Application with Long Cyclic Durability of 100 000 Cycles

Abstract3D printing, a rapidly expanding domain of additive manufacturing, enables the fabrication of intricate 3D structures with adjustable fabrication parameters and scalability. Nonetheless, post‐fabrication, 3D‐printed materials often require an activation step to eliminate non‐conductive polymers, a process traditionally achieved through chemical, thermal, or electrochemical methods. These conventional activation techniques, however, suffer from inefficiency and inconsistent results. In this study, a novel chemical‐free activation method employing laser treatment is introduced. This innovative technique effectively activates 3D‐printed electrodes, which are then evaluated for their photo and electrochemical performance against traditional solvent‐activated counterparts. The method not only precisely ablates surplus non‐conductive polymers but also exposes and activates the underlying electroactive materials. The 3D‐printed electrodes, processed with this single‐step laser approach, exhibit a notably low overpotential of ≈505 mV at a current density of −10 mA cm−2 under an illumination wavelength of 365 nm. These electrodes also demonstrate exceptional durability, maintaining stability through >100 000 cycles in energy storage applications. By amalgamating 3D printing with laser processing, the creation of electrodes with complex structures and customizable properties is enabled. This synergy paves the way for streamlined production of such devices in the field of energy conversion and storage.

Electrowriting of SU-8 Microfibers.

As microfiber-based additive manufacturing (AM) technologies, melt electrowriting (MEW) and solution electrowriting (SEW) have demonstrated efficacy with more biomedically relevant materials. By processing SU-8 resin using MEW and SEW techniques, a material with substantially different mechanical, thermal, and optical properties than that typically processed is introduced. SU-8 polymer is temperature sensitive and requires the devising of a specific heating protocol to be properly processed. Smooth-surfaced microfibers resulted from MEW of SU8 for a short period (from 30 to 90 min), which provides the greatest control and, thus, reproducibility of the printed microfibers. This investigation explores various parameters influencing the electrowriting process, printing conditions, and post-processing to optimize the fabrication of intricate 3D structures. This work demonstrates the controlled generation of straight filaments and complex multi-layered architectures, which were characterized by brightfield, darkfield, and scanning electron microscopy (SEM). This research opens new avenues for the design and development of 3D-printed photonic systems by leveraging the properties of SU-8 after both MEW and SEW processing.

3D Printing Chitosan-based Nanobiomaterials for Biomedicine and Drug Delivery: Recent Advances on the Promising Bioactive Agents and Technologies

Abstract: 3D bioprinting is a novel technology that has gained significant attention recently due to its potential applications in developing simultaneously controlled drug delivery systems (DDSs) for administering several active substances, such as growth factors, proteins, and drug molecules. This technology provides high reproducibility and precise control over the fabricated constructs in an automated way. Chitosan is a natural-derived polysaccharide from chitin, found in the exoskeletons of crustaceans such as shrimp and crabs. Chitosan-based implants can be prepared using 3D bioprinting technology by depositing successive layers of chitosan-based bioink containing living cells and other biomaterials. The resulting implants can be designed to release drugs at a controlled rate over an extended period. The use of chitosan-based implants for drug delivery has several advantages over conventional drug delivery systems. Chitosan is biodegradable and biocompatible, so it can be safely used in vivo without causing any adverse effects. It is also non-immunogenic, meaning it does not elicit an immune response when implanted in vivo. Chitosan-based implants are also cost-effective and can be prepared using simple techniques. 3D bioprinting is an emerging technology that has revolutionized the field of tissue engineering by enabling the fabrication of complex 3D structures with high precision and accuracy. It involves using computer-aided design (CAD) software to create a digital model of the desired structure, which is then translated into a physical object using a 3D printer. The printer deposits successive layers of bioink, which contains living cells and other biomaterials, to create a 3D structure that mimics the native tissue. One of the most promising applications of 3D bioprinting is developing drug delivery systems (DDSs) to administer several active substances, such as growth factors, proteins, and drug molecules. DDSs are designed to release drugs at a controlled rate over an extended period, which can improve therapeutic efficacy and reduce side effects. Chitosan-based implants have emerged as a promising candidate for DDSs due to their attractive properties, such as biodegradability, biocompatibility, low cost, and non-immunogenicity. 3D bioprinting technology has emerged as a powerful tool for developing simultaneously controlled DDSs for administering several active substances. The rationale behind integrating 3D printing technology with chitosan-based scaffolds for drug delivery lies in the ability to produce customized, biocompatible, and precisely designed systems that enable targeted and controlled drug release. This novel methodology shows potential for advancing individualized healthcare, regenerative treatments, and the creation of cutting-edge drug delivery systems. This review highlights the potential applications of 3D bioprinting technology for preparing chitosan-based implants for drug delivery.

Demonstration of MOCVD based in situ etching of β-Ga2O3 using TEGa

In this work, we demonstrate an in situ etch technique for β-Ga2O3 inside a metalorganic chemical vapor deposition (MOCVD) reactor using triethylgallium (TEGa) as the etching agent. At sufficiently high substrate temperatures (Tsub), TEGa is introduced into the MOCVD reactor which undergoes pyrolysis, resulting in the deposition of Ga on the β-Ga2O3 surface. These Ga adatoms react with Ga2O3 to form gallium suboxide (Ga2O), which desorbs from the β-Ga2O3 surface resulting in the etching of the epilayer. MOCVD chamber parameters such as TEGa molar flow rate, substrate temperature, and chamber pressure were shown to be key in controlling the etch rate and surface morphology. A wide range of etch rates from ∼0.3 to 8.5 μm/h is demonstrated by varying the etch parameters. In addition, smooth surface morphology on (010) and (001) β-Ga2O3 substrates is also demonstrated. This new etch technique could enable damage free fabrication of 3D structures like fins and trenches, which are key components in many β-Ga2O3 device structures.

UV-assisted robotic arm freeforming of SiOC ceramics from a preceramic polymer

Material extrusion is a very common and facile additive manufacturing technique for ceramic materials, allowing for rapid design and fabrication of 3D structures without expensive tools. However, fabricating sophisticated structures with large spanning parts and overhanging features using this technology is still a challenge. Here, UV-assisted additive manufacturing is enabled by performing material extrusion with the assistance of UV light using mixture of a preceramic polymer and a photopolymer. The rheological properties of the ink were investigated under UV light radiation to optimize the printing parameters to achieve excellent printability. Complex ceramic structures were fabricated with this method, such as spiral and truss structures, which would be very difficult to obtain using traditional material extrusion without sacrificial supports. These structures have potential application in lightweight ceramic components, such as sandwich structures.

A comprehensive study on the jet electrodeposition method for fabricating 3D structures with overhangs

Electrochemical additive manufacturing (ECAM) is gaining increasing attention in the fabrication of micro/nano-scale metal structures due to its advantages, such as high forming accuracy, low porosity, absence of thermal stress, etc. Among various ECAM techniques, interest is increasingly enhanced in jet electrochemical deposition (Jet ECD) approach due to its ultra-high deposition rate. Despite its inherent advantages as a high-efficiency ECAM process, Jet ECD still faces challenges for automated fabrication of complex 3D structures due to suitable control of the jetted flow. In the present study, a step-delay method based on Jet ECD is proposed. This approach allows for the automation of the fabrication process using commonly employed stepper motor translational stages, seamlessly integrating it into the current 3D printing framework. By adjusting the moving time of the stages and the delay time between two successive steps, agreement between the movement of the stages and the temporally nonlinear electrodeposition rate can be achieved. Consequently, complex 3D copper structures with overhangs, such as 3D helical structures, are successfully obtained. It is found the deposition rate can be as high as ∼25 µm/min, and the maximum overhanging angle that can be achieved by the automated step-delay method is ∼60°. The mechanical properties of the deposited copper using the proposed approach have been thoroughly characterized by various techniques. The average grain size of the deposited copper can be as small as 0.5 µm without preferred orientation. It also shows that highly dense structures with porosity of less than 0.1% can be obtained, and the elastic modulus of the deposited copper ranges from 3 - 20 GPa. In future studies, it is anticipated that larger overhanging angles can be achieved by incorporating image recognition techniques in the step-delay method.

Kirigami-based inverse design for 3D surfaces formed by mechanically guided method

The mechanically guided assembly method utilizes the compressive buckling behavior of thin-film structures to transform two-dimensional (2D) precursors into three-dimensional (3D) structures. Previous research has shown that by inverse designing thickness and width distributions in 2D precursors, various 3D surfaces with target geometries can be accurately assembled. However, the variation in thickness poses significant challenges for the fabrication of the 2D precursor, especially on a small scale. In this paper, we propose a Kirigami-based inverse design framework that utilizes pre-specified incision patterns as critical parameters to control the bending stiffness distribution of 2D precursors. This enables the fabrication of target 3D structures with constant thickness, which greatly simplifies the production of 2D precursors. By studying the deformation characteristics of beam models during pure bending, we have established an analytical relationship between incision patterns and bending stiffness distribution. To validate the effectiveness of our inverse design theory, we conducted a series of simulations and experiments on 3D structures, yielding favorable comparison results. Moreover, guided by this inverse design theory, we have developed a microneedle structure through conceptual design, demonstrating the capability of Kirigami patterns in the inverse design of complex 3D structures, and highlighting the potential application of our method in the biomedical field.

Processing of membranes and 3D scaffolds based on n-TiO2 colloidally dispersed on a thermoplastic matrix for photocatalytic pollutant removal

One of the most promising technologies for water treatment today is photocatalytic membrane reactors (PMRs). Manufacturing efficient membranes is still challenging as many factors are involved, like the porosity, specific surface area, nature and size of particles. In this work, a colloidal method to self-support commercial nanoparticles (n-TiO2) in a polymeric matrix of polylactic acid (PLA) is proposed allowing the fabrication of 2D and 3D structures with high inorganic content that can be adapted to the PMR configurations. Using a commercial filament of PLA loaded with up to 15 vol% of n-TiO2 as starting point, photocatalytic membranes have been manufactured by FFF. In addition, following a similar process, tapes with n-TiO2 particles up to 15 vol% have been processed by tape casting. Thermal characterisation (DTA) and dynamic rheometry evaluated the commercial filament for printing to determine the conditions used during the thermal extrusion and printing processes. FTIR and XRD technologies were used to determine the chemical interactions of PLA matrices with TiO2 nanoparticles. Porosity was measured by Archimedes's method for the filaments, by mercury intrusion for the membranes and by optical microscopy for the scaffolds. Finally, the microstructure of the 2D and 3D pieces was evaluated by scanning microscopy. 2D tape cast membranes were compared with individual filaments and 3D printed scaffolds in linear and gyroidal geometries. The catalytic activity results indicate that tape cast membranes show much higher kinetic constants than the individual filaments and the linear and gyroidal scaffolds. Regarding the two different printed scaffolds, in contrast to the kinetic values, gyroidal geometries achieve an average degradation time (t50) of 6.1 h, which is a lower value than those observed for linear scaffold geometries. Methyl orange degradation tests after 24 h exposure under UV light showed degradation rates of 98% for membranes, 90% for commercial filaments, 80% for gyroidal scaffolds and 60% for linear patterns. Therefore, these results are promising as a solution for fabricating easily extractable self-supported membranes for water treatment in PMRs.

Vat photopolymerization 3D printing of polymer-derived SiOC ceramics with high precision and high strength

Polymer-derived ceramic (PDC) combined with 3D printing technology allows for the fabrication of various complex 3D structures and components that cannot be achieved through conventional ceramic preparation methods. However, current 3D printing PDC technologies suffer from low accuracy, poor mechanical and low ceramic yield, which severely limit their application values. Here, we report a polysiloxane-based preceramic polymer (PCP) precursor capable of producing high-precision and high-strength SiOC ceramics with ceramic yield as high as 56.9% after pyrolysis at 1100℃ in vacuum. Adding butyl acrylate into the precursor significantly improves printing resolution. Through special material design and printing parameter optimization, we fabricate various complex structures with overall sizes ranging from submillimeters to centimeters and printing resolution as high as 5 μm via vat photopolymerization 3D printing. The compressive strength of SiOC ceramic with I-WP structure reaches up to 240MPa while its density is only 0.367g/cm3, corresponding to a specific strength as high as 6.54 × 105N·m/kg. The printing resolution, specific strength and ceramic yield are all at the top level compared with previously reported works. The proposed approach will greatly promote the industrial application of 3D printing PDC technology in engineering fields and extreme environments.

Hybrid Biofabrication of Heterogeneous 3D Constructs Using Low-Viscosity Bioinks.

The application of cytocompatible hydrogels supporting extensive cellular activities to three-dimensional (3D) bioprinting is crucial for recreating complex physiological environments with high biomimicry. However, the poor printability and tunability of such natural hydrogels diminish the versatility and resolution of bioprinters. In this study, we propose a novel approach for the hybrid biofabrication of complex and heterogeneous 3D constructs using low-viscosity bioinks. Poly(lactic acid) (PLA) filament is extruded by fused deposition modeling on a micromesh to create PLA-framed micromesh substrates onto which fibrinogen is printed by microextrusion bioprinting. The micromesh supports the printed hydrogel with a capillary pinning effect to enable high-resolution bioprinting. Accordingly, the micromesh-bioink layers are aligned and stacked to form volumetric constructs. This approach, called the 3D micromesh-bioink overlaid structure and interlocked culture (3D MOSAIC) platform, enables the fabrication of complicated and multimaterial 3D structures, including overhangs and voids. Endothelial cells cultured under vasculogenic conditions in the platform self-organize within the biologically functional hydrogel to form vascular networks, and cancer cell migration can be observed across the layers. The multidisciplinary 3D MOSAIC platform is an important step toward the biofabrication of complex constructs with high biological and structural significance and functionality.

Polycaprolactone with multiscale porosity and patterned surface topography prepared using sacrificial 3D printed moulds: Towards tailor-made scaffolds

Biocompatible three-dimensional porous scaffolds are widely used in multiple biomedical applications. However, the fabrication of tailor-made 3D structures with controlled and combined multiscale macroscopic-microscopic, surface and inner porosities in a straightforward manner is still a current challenge. Herein, we use multimaterial fused deposition modeling (FDM) to generate poly (vinyl alcohol) (PVA) sacrificial moulds filled with poly (Ɛ-caprolactone) (PCL) to generate well defined PCL 3D objects. Further on, the supercritical CO2 (SCCO2) technique, as well as the breath figures mechanism (BFs), were additionally employed to fabricate specific porous structures at the core and surfaces of the 3D PCL object, respectively. The biocompatibility of the resulting multiporous 3D structures was tested in vitro and in vivo, and the versatility of the approach was assessed by generating a vertebra model fully tunable at multiple pore size levels. In sum, the combinatorial strategy to generate porous scaffolds offers unique possibilities to fabricate intricate structures by combining the advantages of additive manufacturing (AM), which provides flexibility and versatility to generate large sized 3D structures, with advantages of the SCCO2 and BFs techniques, which allow to finely tune the macro and micro porosity at material surface and material core levels.

Printability of Poly(lactic acid) Ink by Embedded 3D Printing via Immersion Precipitation.

Immersion precipitation three-dimensional printing (ip3DP) and freeform polymer precipitation (FPP) are unique and versatile methods of 3D printing to fabricate 3D structures based on nonsolvent-induced phase separation via direct ink writing (DIW). Immersion precipitation involves complex dynamics among solvents, nonsolvents, and dissolved polymers, and the printability of 3D models in these methods requires further understanding. To this end, we characterized these two methods of 3D printing using polylactide (PLA) dissolved in dichloromethane (7.5-30% w/w) as model inks. We analyzed the rheological properties of the solutions and the effect of printing parameters on solvent-nonsolvent diffusion to achieve printability. The PLA inks exhibited shear-thinning properties, and their viscosities varied over three orders of magnitude (10-1∼102 Pa·s). A processing map was presented to understand the ideal ranges of the concentration of PLA in inks and the nozzle diameter to ensure printability, and the fabrication of complex 3D structures was fabricated with adequate applied pressure and nozzle speed. The processing map also highlighted the advantages of embedded 3D printing over solvent-cast 3D printing based on solvent evaporation. Lastly, we demonstrated that the porosity of the interface and inner structure of the printed objects was readily tailored by the concentration of the PLA and the porogen added to the ink. The methods presented here offer new perspectives to fabricate micro-to-centimeter objects of thermoplastics with nanometer-scale inner pores and provide guidelines for successful embedded 3D printing based on immersion precipitation.

Parallel two-photon lithography achieving uniform sub-200 nm features with thousands of individually controlled foci.

The limited throughput of nano-scale laser lithography has been the bottleneck for its industrial applications. Although using multiple laser foci to parallelize the lithography process is an effective and straightforward strategy to improve rate, most conventional multi-focus methods are plagued by non-uniform laser intensity distribution due to the lack of individual control for each focus, which greatly hinders the nano-scale precision. In this paper, we present a highly uniform parallel two-photon lithography method based on a digital mirror device (DMD) and microlens array (MLA), which allows the generation of thousands of femtosecond (fs) laser foci with individual on-off switching and intensity-tuning capability. In the experiments, we generated a 1,600-laser focus array for parallel fabrication. Notably, the intensity uniformity of the focus array reached 97.7%, where the intensity-tuning precision for each focus reached 0.83%. A uniform dot array structure was fabricated to demonstrate parallel fabrication of sub-diffraction limit features, i.e., below 1/4 λ or 200 nm. The multi-focus lithography method has the potential of realizing rapid fabrication of sub-diffraction, arbitrarily complex, and large-scale 3D structures with three orders of magnitude higher fabrication rate.

Fabrication of 3D structure with heterogeneous compositions using inkjet printing process

Inkjet based 3D printing technology discharges fine ink droplets from multiple printer heads to perform patterning and depositing in the target locations. The inkjet 3D printing can be differentiated from other 3D printing processes. It can print multiple materials simultaneously by using multiple printer heads, thus it is appropriate to create heterogeneous complex structure such as electronic devices. This study demonstrated the inkjet 3D printing to manufacture multi-layer composite structures using photocurable SiO2 ink and intense pulsed light (IPL) sinterable conductive Cu ink. The rheology and deposition behavior of each ink were investigated so that it could be applied for inkjet 3D printing. The various shape of 3D structures which are consist of insulative and conductive layers were fabricated to study the applicability of inkjet 3D printing in the electronics.

Additive manufacturing of fiber-reinforced polymer composites: A technical review and status of design methodologies

Additive manufacturing (AM) of fiber-reinforced composites is gaining traction as an important manufacturing technology to produce complex, highly customized structures. AM processes enable the fabrication of complex 3D structures with control over fiber position and orientation, offering tremendous design freedom. Although the use of AM to fabricate fiber-reinforced composites is promising, various design difficulties remain. These include consideration of structural performance subject to manufacturing constraints on fiber placement, orientation, bend radius, and other relevant limitations. Design engineers will have to consider these limitations to be able to reap the full benefits of AM to fabricate fiber-reinforced polymer composites. This paper aims to provide a survey on the advances in multi-scale topology optimization, fiber orientation parameterization, micromechanics of fiber-matrix interactions and process planning specific for the AM of complex fiber reinforced composites. The status of recent research is summarized, and future directions outlined.

Digital Light‐Processing (DLP) 3D Printing of Magnesium Phosphate Minerals and Cements

Digital light processing (DLP) enables the fabrication of complex 3D structures based on a photopolymerizable resin usually containing a photo initiator and an UV or photo absorber. The resin and thus the final properties of the printed structures can be adjusted by adding fillers like bioceramic powders relevant for bone‐regeneration applications. Herein, a water‐based and biocompatible poly(ethylene glycol diacrylate) (PEGDA) resin containing the photo initiator lithium‐phenyl‐2,4,6‐trimethylbenzoylphosphinate (LAP) enables the production of 3D structures via DLP. The addition of calcium magnesium phosphate cement (CMPC) powder, acting as photo absorber, leads to higher accuracy of the final structures. After curing the printed construct in a diammonium–hydrogen phosphate (DAHP) bath for hardening, the resulting mechanical properties can be adjusted without post‐process sintering. Solid loading of up to 40 wt% CMPC powder is possible, and the resins are investigated regarding their rheological behavior and printability. The resulting constructs are analyzed in respect to their surface morphology using scanning electron microscope (SEM), porosity, phase composition using X‐ray diffraction (XRD) methods, as well as mechanical properties influenced by the hardening process using DAHP for different durations.

A wrinkling-assisted strategy for controlled interface delamination in mechanically-guided 3D assembly

Mechanically-guided three-dimensional (3D) assembly is a recently established method for the fabrication of 3D structures and devices at micro/nanoscale. Such assembly methods typically involve a process of compressive buckling in a patterned high-modulus thin film integrated with a low-modulus elastomer substrate at selective regions. A successful assembly requires, simultaneously, a sufficiently strong interface in selective regions to stay undelaminated, and a sufficiently weak interface in remaining regions to be fully separated. However, such requirements are very challenging to meet for highly flexible 3D mesostructures or those with large-area suspended features. Here, we propose a wrinkling-assisted strategy to substantially facilitate the delamination at desired regions of the film/substrate system. An additional assisting layer is introduced such that a weaker film/assisting-layer interface replaces the original film/substrate interface, and the wrinkles formed in the assisting layer induce additional driving forces to separate the film/assisting-layer interface. An analytical model is developed to capture the delamination of the thin film from the wrinkled assisting layer, which is validated by both experiments and finite element analyses (FEA). The model shows that a combined material/geometry parameter governs the process of delamination in the bilayer film/substrate system, offering a useful design reference for the mechanically-guided 3D assembly. Furthermore, our experiments and FEA demonstrate that the wrinkling-assisted strategy can enable the assembly of highly flexible 3D mesostructures and those with large areas attached to the substrate in the initial configuration, which are particularly challenging to achieve by using previous strategies.

Synergistic, Orthogonal, and Antagonistic Photochemistry for Light‐Induced 3D Printing

Abstract3D printing techniques are often based on light‐induced chemical reactions, driven by the fascinating and powerful possibilities to control light in space and time. To date, these approaches are usually restricted to a single color of light, which does not do justice to light as an entire spectrum of distinct wavelengths. It is possible to further tap into the vast potential of light‐induced 3D printing by introducing a second color of light. While the complexity of photochemical interactions in two‐color systems is greatly increased, it concomitantly allows for enhanced control over manufacturing speed and resolution. In general, three types of two‐color interactions can be distinguished, i.e., synergistic, orthogonal, and antagonistic. In recent years, intriguing printing techniques with superior potential for the fabrication of 3D structures are emerging that require two colors of light. Their future development potential is vast yet needs to be critically underpinned by an advance in complex tunable photochemical reaction systems. The current perspective will thus explore the potential for using synergistic, orthogonal, and antagonistic photochemistries in 3D printing.