Laser 3D Printing Research Articles

Microstructure and material properties of 3D-printed bimetallic steels

Corroded steel components can be repaired by laser 3D printing technology. However, studies on the mechanical behaviour of repaired areas composed of a substrate and deposited material are still limited. In this study, 316L stainless steel powder was deposited on Q355B steel plates through 3D laser printing technology to form bimetallic steel plates. Uniaxial tensile tests were conducted on Q355B steel coupons, laser 3D-printed 316L stainless steel coupons, and bimetallic steel coupons. The test results revealed that ductile fracture occurred in the bimetallic steel coupons. The mechanical properties of bimetallic steel are considerably correlated with the properties of the cladding layer and substrate. During the loading process, the axial strain of the bimetallic steel coupons was uniformly distributed along the thickness direction, indicating that the substrate and cladding materials maintained excellent cooperative deformation. Bending tests and scanning electron microscopy observations indicate that a reliable and robust metallurgical bond is established at the interface between the substrate and the cladding layer. The interface area can be divided into the cladding layer, the carburising zone, the decarburised zone, and the Q355B substrate. The microhardness results indicate a considerable increase in the hardness of the carburised layer, which enhances the tensile strength of the bimetallic steel. On the basis of the experimental results, a three-stage model for predicting the stress‒strain curve of bimetallic steel was established.

Fiber-integrated hybrid achromatic microlenses by combined femtosecond laser 3D printing

Fiber-integrated hybrid achromatic microlenses by combined femtosecond laser 3D printing

Theoretical Analysis of Self-Shrinkage Spheroidization of Irregular Degradable Polymer Powder under Thermodynamic Nonequilibrium State

Laser three-dimensional (3D) printing offers significant advantages in integrating the shape and function of regenerative tissues through biomimetic manufacturing. However, its effectiveness is limited by the lack of specialized biopolymer powders—while solvent methods that use residual solvents produce powders with poor biocompatibility, mechanical methods result in irregularly shaped crystals. In this study, a biopolymer powder spheroidization and shaping technology, which utilizes the evolution of irregular powders into spheres with minimal surface free energy in the molten state, is proposed based on the thermodynamic principle of minimum energy. Initially, the motion trajectory and temperature field of the poly(L-lactic acid) (PLLA) powder during spheroidization were quantitatively assessed and optimized using Stokes’ law and Fourier's principle. Subsequently, the cohesive forces and aggregation kinetics of the polymer chains were calculated using molecular dynamics. Finally, based on these calculations, a phase-field model was constructed to simulate the evolution of the spheroidization rate and deduce the optimal parameters for the process. This precise approach enhances PLLA spheroidization control for laser 3D printing, improves part densification and surface quality, and offers a clean and efficient path for preparing high-quality PLLA spheroidized powder for laser 3D printing.

Site-Selective Biofunctionalization of 3D Microstructures Via Direct Ink Writing.

Two-photon lithography has revolutionized multi-photon 3D laser printing, enabling precise fabrication of micro- and nanoscale structures. Despite many advancements, challenges still persist, particularly in biofunctionalization of 3D microstructures. This study introduces a novel approach combining two-photon lithography with scanning probe lithography for post-functionalization of 3D microstructures overcoming limitations in achieving spatially controlled biomolecule distribution. The method utilizes a diverse range of biomolecule inks, including phospholipids, and two different proteins, introducing high spatial resolution and distinct functionalization on separate areas of the same microstructure. The surfaces of 3D microstructures are treated using bovine serum albumin and/or 3-(Glycidyloxypropyl)trimethoxysilane (GPTMS) to enhance ink retention. The study further demonstrates different strategies to create binding sites for cells by integrating different biomolecules, showcasing the potential for customized 3D cell microenvironments. Specific cell adhesion onto functionalized 3D microscaffolds is demonstrated, which paves the way for diverse applications in tissue engineering, biointerfacing with electronic devices and biomimetic modeling.

Stealthy and hyperuniform isotropic photonic band gap structure in 3D.

In photonic crystals, the propagation of light is governed by their photonic band structure, an ensemble of propagating states grouped into bands, separated by photonic band gaps. Due to discrete symmetries in spatially strictly periodic dielectric structures their photonic band structure is intrinsically anisotropic. However, for many applications, such as manufacturing artificial structural color materials or developing photonic computing devices, but also for the fundamental understanding of light-matter interactions, it is of major interest to seek materials with long range nonperiodic dielectric structures which allow the formation of isotropic photonic band gaps. Here, we report the first ever 3D isotropic photonic band gap for an optimized disordered stealthy hyperuniform structure for microwaves. The transmission spectra are directly compared to a diamond pattern and an amorphous structure with similar node density. The band structure is measured experimentally for all three microwave structures, manufactured by 3D laser printing for metamaterials with refractive index up to . Results agree well with finite-difference-time-domain numerical investigations and a priori calculations of the band gap for the hyperuniform structure: the diamond structure shows gaps but being anisotropic as expected, the stealthy hyperuniform pattern shows an isotropic gap of very similar magnitude, while the amorphous structure does not show a gap at all. Since they are more easily manufactured, prototyping centimeter scaled microwave structures may help optimizing structures in the technologically very interesting region of infrared.

Minimal-Invasive 3D Laser Printing of Microimplants in Organismo.

Multi-photon 3D laser printing has gathered much attention in recent years as a means of manufacturing biocompatible scaffolds that can modify and guide cellular behavior in vitro. However, in vivo tissue engineering efforts have been limited so far to the implantation of beforehand 3D printed biocompatible scaffolds and in vivo bioprinting of tissue constructs from bioinks containing cells, biomolecules, and printable hydrogel formulations. Thus, a comprehensive 3D laser printing platform for in vivo and in situ manufacturing of microimplants raised from synthetic polymer-based inks is currently missing. Here, a platform for minimal-invasive manufacturing of microimplants directly in the organism is presented by one-photon photopolymerization and multi-photon 3D laser printing. Employing a commercially available elastomeric ink giving rise to biocompatible synthetic polymer-based microimplants, first applicational examples of biological responses to in situ printed microimplants are demonstrated in the teleost fish Oryzias latipes and in embryos of the fruit fly Drosophila melanogaster. This provides a framework for future studies addressing the suitability of inks for in vivo 3D manufacturing. The platform bears great potential for the direct engineering of the intricate microarchitectures in a variety of tissues in model organisms and beyond.

Radiator production for Pylon Fission Surface Power System through lunar In-Situ Resource Utilization

Background Fission Surface Power (FSP) is currently being considered by NASA for future lunar exploration and Ultra-Safe Nuclear Corporation (USNC) is developing their Pylon FSP system. Methods This paper introduces the system focusing on the materials used for its main components. It also analyses the lunar availability of the elements required to produce these components and suggests that In-Situ Resource Utilization (ISRU) should be considered. Results As a result of the conducted analysis, it is concluded that since mass is the most important parameter when launching payload from Earth, the Pylon component with the largest mass should be considered further. The heaviest system component is the power system which, however, consists of many other components that are made from various materials. The second heaviest component is the radiator made of Titanium (Ti) metal heat pipes and Graphite Fiber Reinforced Composite (GFRC) face sheets with water as the working fluid. Since the production of Ti metal on the Moon is non-economical, Aluminum (Al) metal utilized for the International Space Station (ISS) is considered. Lunar infrastructure required to produce Al using ISRU is already available. Further analysis will be conducted in the future to look into laser 3D printing technologies. Lunar Resources Inc. is already developing techniques for Al extraction from regolith for the production of Al wires. Conclusions This research shows that all the required technologies already exist, and the next step will be to identify how the obtained Al can be manufactured into radiators. It will also be important to identify how much of the total radiator mass is Al metal to increase the fidelity of this analysis Future research will find the break-even point between the Pylon Ti radiators launched from Earth and the production of Al radiators on the Moon.

Toward Synthetic Physical Fingerprint Targets.

Biometric fingerprint identification hinges on the reliability of its sensors; however, calibrating and standardizing these sensors poses significant challenges, particularly in regards to repeatability and data diversity. To tackle these issues, we propose methodologies for fabricating synthetic 3D fingerprint targets, or phantoms, that closely emulate real human fingerprints. These phantoms enable the precise evaluation and validation of fingerprint sensors under controlled and repeatable conditions. Our research employs laser engraving, 3D printing, and CNC machining techniques, utilizing different materials. We assess the phantoms' fidelity to synthetic fingerprint patterns, intra-class variability, and interoperability across different manufacturing methods. The findings demonstrate that a combination of laser engraving or CNC machining with silicone casting produces finger-like phantoms with high accuracy and consistency for rolled fingerprint recordings. For slap recordings, direct laser engraving of flat silicone targets excels, and in the contactless fingerprint sensor setting, 3D printing and silicone filling provide the most favorable attributes. Our work enables a comprehensive, method-independent comparison of various fabrication methodologies, offering a unique perspective on the strengths and weaknesses of each approach. This facilitates a broader understanding of fingerprint recognition system validation and performance assessment.

Two-Orders-of-Magnitude Enhancement of Photoinitiation Activity via a Simple Surface Engineering of Metal Nanoclusters.

Development of high-performance photoinitiator is the key to enhance the printing speed, structure resolution and product quality in 3D laser printing. Here, to improve the printing efficiency of 3D laser nanoprinting, we investigate the underlying photochemistry of gold and silver nanocluster initiators under multiphoton laser excitation. Experimental results and DFT calculations reveal the high cleavage probability of the surface S-C bonds in gold and silver nanoclusters which generate multiple radicals. Based on this understanding, we design several alkyl-thiolated gold nanoclusters and achieve a more than two-orders-of-magnitude enhancement of photoinitiation activity, as well as a significant improvement in printing resolution and fabrication window. Overall, this work for the first time unveils the detailed radical formation pathways of gold and silver nanoclusters under multiphoton activation and substantially improves their photoinitiation sensitivity via surface engineering, which pushes the limit of the printing efficiency of 3D laser lithography.

Two‐Orders‐of‐Magnitude Enhancement of Photoinitiation Activity via a Simple Surface Engineering of Metal Nanoclusters

AbstractDevelopment of high‐performance photoinitiator is the key to enhance the printing speed, structure resolution and product quality in 3D laser printing. Here, to improve the printing efficiency of 3D laser nanoprinting, we investigate the underlying photochemistry of gold and silver nanocluster initiators under multiphoton laser excitation. Experimental results and DFT calculations reveal the high cleavage probability of the surface S−C bonds in gold and silver nanoclusters which generate multiple radicals. Based on this understanding, we design several alkyl‐thiolated gold nanoclusters and achieve a more than two‐orders‐of‐magnitude enhancement of photoinitiation activity, as well as a significant improvement in printing resolution and fabrication window. Overall, this work for the first time unveils the detailed radical formation pathways of gold and silver nanoclusters under multiphoton activation and substantially improves their photoinitiation sensitivity via surface engineering, which pushes the limit of the printing efficiency of 3D laser lithography.

Fabrication and characterization of particle-stacking microporous nickel using laser powder bed fusion

Nickel (Ni) and nickel-based materials with specific pore configurations, particularly interconnected micropores as channels, have significant potential in new energy technologies. Laser 3D printing is a simple, rapid, and effective method for one-step formation; however, challenges remain in the fabrication of micropores (< 50 μm). This study successfully designed a particle-to-particle stacking microporous nickel structure using laser energy to regulate the melting and fusion behaviors of nickel particles. While laser power had a minimal effect on the pore size, it significantly impacted the porosity. The formation of interconnected pores depended on a large hatch distance and high laser scanning speed, while the latter also contributed to the creation of uniform micropores characterized by narrow sintered bands. The particle-stacking microporous nickel exhibited a homogeneous pore distribution, with pore sizes ranging from approximately 10 to 50 μm in both mean pore size and median pore size (D50), along with a high percentage size distribution in 1 – 10 μm. Furthermore, it displayed controllable porosities between 18.44% and 52.94%, along with remarkable resistance to deformation and superior compressive performance, featuring a high yield strength exceeding 50 MPa compared to the conventionally-processed porous nickels.

Machining technologies and structural models of microfluidic devices

In the past decades, microfluidic chips have been one of the hottest research topics in the “lab-on-a-chip” field. However, it is still a challenge for design the perfect microchannels with high functional integration, complex geometry, and high production efficiency. This review paper provides a comprehensive overview of microfluidic structural models and designs, manufacturing techniques, and bonding methods. The effect of three types of microfluidic channel structure models and their configuration parameters on the fluid behaviors of microfluidics was investigated. Surface-to-volume ratio of the flow channel is a critical parameter for determining the mixing and diffusion capabilities of the microfluidic devices (MDs). Thereafter, the main manufacturing techniques for microstructures were discussed, including etching, photolithography, soft lithography, molding, mechanical micro-machining, laser beam micromachining, printing, and 3D printing. We performed a statistical analysis to discuss the relative advantages and disadvantages of these manufacturing methods. In addition, the current bonding methods for MDs were also summarized, including thermal bonding, solution adhesive bonding, dry adhesive bonding, plasma bonding, and anodic bonding. a comparison of different bonding methods was presented to provide a reference to select a suitable bonding method for the assembly of microfluidic device. Finally, the tendencies and challenges of microchannel manufacturing were discussed, and the prospects were also provided.

Research Progress of 3D Printing Technology for Pharmaceutical Preparation

Abstract: Pharmaceutical preparation is a kind of finished pharmaceutical product made by combining raw materials with various auxiliary materials in a certain form. At present, the field of pharmaceutical preparations can meet most drug needs, but there are some limitations. It is difficult to realize the production of personalized preparations. Because 3D printing technology has the ability of precise dose control and flexible shape customization, it can realize precise control of drug dosage, release behavior and local targeting in pharmaceutical preparations. Therefore, in medicine, 3D printing technology is increasingly used in the field of pharmaceutical preparations. 3D printing technology provides an important means for new drug printing and personalized drug customization of pharmaceutical preparations in the medical field. The 3D printing technology of drugs will inject fresh vitality into individualized drug delivery. Therefore, the development trend of 3D printing technology for pharmaceutical preparations has attracted more and more attention. In order to optimize the wide application of 3D printing technology in pharmaceutical preparation, 3D printing technology such as inkjet 3D printing technology, extrusion 3D printing technology and laser 3D printing technology were studied. In this paper, the selection, classification and introduction of 3D printing technology such as inkjet 3D printing technology, extrusion 3D printing technology and laser 3D printing technology in pharmaceutical preparations are reviewed. Through the investigation of various patents of 3D printing technology applied to pharmaceutical preparation in medicine, this paper summarizes and analyzes the main problems of 3D printing technology applied to pharmaceutical preparations, such as printing stability, production quality, etc. In addition, the development trend of 3D printing technology is also discussed. Optimization of various 3D printing technologies applied to pharmaceutical preparation in medicine is beneficial to improve printing stability and production quality in medicine. More related patents will be invented in the future.

Two- and three-photon processes during photopolymerization in 3D laser printing.

The performance of a photoinitiator is key to control efficiency and resolution in 3D laser nanoprinting. Upon light absorption, a cascade of competing photophysical processes leads to photochemical reactions toward radical formation that initiates free radical polymerization (FRP). Here, we investigate 7-diethylamino-3-thenoylcoumarin (DETC), belonging to an efficient and frequently used class of photoinitiators in 3D laser printing, and explain the molecular bases of FRP initiation upon DETC photoactivation. Depending on the presence of a co-initiator, DETC causes radical generation either upon two-photon- or three-photon excitation, but the mechanism for these processes is not well understood so far. Here, we show that the unique three-photon based radical formation by DETC, in the absence of a co-initiator, results from its excitation to highly excited triplet states. They allow a hydrogen-atom transfer reaction from the pentaerythritol triacrylate (PETA) monomer to DETC, enabling the formation of the reactive PETA alkyl radical, which initiates FRP. The formation of active DETC radicals is demonstrated to be less spontaneous. In contrast, photoinitiation in the presence of an onium salt co-initiator proceeds via intermolecular electron transfer after the photosensitization of the photoinitiator to the lowest triplet excited state. Our quantum mechanical calculations demonstrate photophysical processes upon the multiphoton activation of DETC and explain different reactions for the radical formation upon DETC photoactivation. This investigation for the first time describes possible pathways of FRP initiation in 3D laser nanoprinting and permits further rational design of efficient photoinitiators to increase the speed and sensitivity of 3D laser nanoprinting.

Recent Advances in Multi-Photon 3D Laser Printing: Active Materials and Applications.

Since the pioneering work of Kawata and colleagues in 1997, multi-photon 3D laser printing, also known as direct laser writing, has made significant advancements in a wide range of fields. Moreover, the development and commercialization of photocurable inks for this technique have expanded rapidly. One of the current trends is the transition from static to active printable materials, often referred to as 4D microprinting, which enables a new degree of control in the printed systems. This review focuses on four primary application areas: microrobotics, optics and photonics, microfluidics, and life sciences, highlighting recent progress and the crucial role of active materials, including liquid crystalline elastomers, hydrogels, shape memory polymers, and composites, among others. It also addresses ongoing challenges and provides insights into the future prospects in the different fields.

Form birefringent polymeric structures realized by 3D laser printing.

The 3D laser printing of form birefringent structures promises fast prototyping of polarization-sensitive photonic elements. However, achieving the quarter- and half-wave phase retardation levels needed in applications still remains a challenge, especially at visible wavelengths. Thickness of the birefringent region, usually consisting of simple 1D gratings, must be sufficiently large to ensure the required retardance, making the 3D laser-printed gratings prone to mechanical collapse. Here we demonstrate 3D laser-printed mechanically robust form birefringent 3D structures whose thickness and phase retardation can be increased without loss of mechanical stability, and report on the realization of compact self-supporting structures exhibiting quarter- and half-wave phase retardation at visible wavelengths.

Heat and mass transfer characteristics of a novel three-dimensional flow field metal bipolar plate for PEMFC by laser 3D printing

The flow field structure of the bipolar plates is a key factor in determining the heat and mass transfer performance of proton exchange membrane fuel cells (PEMFC). To improve its performance and obtain an optimized design and fabrication method, this paper proposes a novel baffled flow field bipolar plate and successfully realizes its preparation using 3D printing technology. A PEMFC computational fluid dynamics model was established for numerical simulation, and polarization tests were also performed to verify the simulation results. The results show that the incorporation of 30°, 60°, and 90° sub-baffles helped to increase the maximum power density of the PEMFC by 3.5%, 8.4%, and 14.7%, respectively, compared to no sub-baffles. The oxygen mass transfer efficiency of the flow field with a 90° sub-baffle increased by 9.4% and 22.1% compared to the 60° and 30° sub-baffles, respectively. However, the increase in inclination angle also causes more water and heat in the flow channel to enter the membrane electrode, which hinders the further improvement of PEMFC performance. This study will provide new ideas and solutions for the flow field structure design and preparation of bipolar plates.

Electron-microscopic study of phase transformations in 316L austenitic steel manufactured by laser 3D printing

We studied the structure and phases in porous samples of 316L austenitic steel manufactured by laser 3D printing. Transmission electron microscopy revealed the presence of residual δ-ferrite along with austenite in the sample. A high density of dislocations is also observed in the sample. EBSD analysis revealed a lack of texture.

Rapidly Direct Laser 3D Printing of High-Performance Protonic Ceramic Fuel Cells

Fuel cells with a dense ionic conducting electrolyte layer sandwiched between two porous electrode layers are one of the most efficient fuel-to-electricity energy conversion devices. Their reversible operation can also efficiently electrolyze water to hydrogen, reduce carbon dioxide to fuels, synthesize ammonia, upgrade fuels, and store energy on large scales. Compared with the popular low-temperature (~80 oC) proton exchange/polymer electrolyte membrane fuel cells and the high-temperature (700-1000 oC) oxygen ion-conducting solid oxide fuel cells (SOFCs), initially used in electric vehicles, auxiliary powers, power plants, and hydrogen electrolyzers, the rising star of protonic ceramic fuel cells (PCFCs) based on proton conducting oxide electrolytes offers excellent suitability for operating at 400-700 oC, the optimum temperature range for electrochemical energy devices, enabling extensive superiorities (high efficiency and performance, long thermal and chemical stabilities, flexible fuels, and cost-effective compatible materials) compared to their counterparts. In recent ten years, many high-performance PCFCs have been reported. However, most performances were achieved using small-area button cells (<0.5cm2) fabricated using spin coating, drop coating, manual brushing, and screen printing of electrolytes on the dry-pressed anode supports, followed by co-firing. There are challenges to transferring the excellent microstructures and materials chemistries/properties obtained from small-area cells to large-area cells and stacks. Furthermore, the decrease in cell component layer thickness for high volumetric cell performance and the requirement for more efficient, faster, and more cost-effective manufacturing motivated the advanced manufacturing of PCFCs.This work will focus on the direct laser 3D printing (DL3DP) of PCFCs performed at Clemson University. The DL3DP integrated 3D printing (microextrusion and ultrasonic spraying) and laser processing (drying, sintering, and machining), allowing for manufacturing PCFC components, single cells, and stacks with the desired microstructures and geometries irrelevant to the area. The DL3DP could rapidly and cost-effectively manufacture PCFCs without conventional long-term furnace processing. The processing speed could be 2 orders of magnitude faster than the conventional tape-casting and furnace co-firing method. The achieved cells and stacks showed excellent fuel cell performance and less dependence on the effective area. The cells showed peak power densities 1.6-2.6 times that of the conventionally processed samples. The stacks demonstrated a peak power of 7 W and constant power outputs of 0.5-3.1 W for 110-260 hours. This DL3DP can be expanded to manufacturing other heterogeneous ceramics for energy conversion and storage devices. Figure 1

Observation of Chirality‐Induced Roton‐Like Dispersion in a 3D Micropolar Elastic Metamaterial

AbstractA theoretical paper based on chiral micropolar effective‐medium theory suggested the possibility of unusual roton‐like acoustical‐phonon dispersion relations in 3D elastic materials. Here, as a first novelty, the corresponding inverse problem is solved, that is, a specific 3D chiral elastic metamaterial structure is designed, the behavior of which follows this effective‐medium description. The metamaterial structure is based on a simple‐cubic lattice of cubes, each of which not only has three translational but also three rotational degrees of freedom. The additional rotational degrees of freedom are crucial within micropolar elasticity. The cubes and their degrees of freedom are coupled by a chiral network of slender rods. As a second novelty, this complex metamaterial is manufactured in polymer form by 3D laser printing and its behavior is characterized experimentally by phonon‐band‐structure measurements. The results of these measurements, microstructure finite‐element calculations, and solutions of micropolar effective‐medium theory are in good agreement. The roton‐like dispersion behavior of the lowest phonon branch results from two aspects. First, chirality splits the transverse acoustical branches as well as the transverse optical branches. Second, chirality leads to an ultrastrong coupling and hybridization of chiral acoustical and optical phonons at finite wavevectors.