Selective Laser Sintering 3D Printing Research Articles

Navigating the frontier: Additive Manufacturing’s role in synthesizing piezoelectric materials for flexible electronics

Additive manufacturing (AM) has significantly transformed the fabrication of functional materials, particularly in electronics and biomedical engineering. This study reviews stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), direct ink writing (DIW), and inkjet printing for flexible electronic applications. The review highlights SLA-based 3D printing’s better ability to optimize material compositions, printing procedures, and post-processing methods to improve material characteristics. Photosensitive materials and shrinkage-induced internal tensions seems to be its major constraint. Additionally, SLS 3D printing has improved composite materials' electrical, mechanical, and thermal properties. It has drawbacks including permeable structures and internal tensions. In FDM 3D printing, mechanical and electrical qualities are improved for piezoelectric sensor manufacture. Warping and nozzle blockage require additional study. DIW’s versatility in constructing complicated structures with increased features for energy harvesting and sensor development is also mentioned. We identify ink development and printer nozzle clogging issues. The review concludes that inkjet printing can provide a variety of materials for flexible electronics. Since it integrates the latest discoveries with technological developments, this study may help guide future research and promote innovation in the sector. Overall, additive manufacturing methods provide a new era of sensor technology by offering unrivalled flexibility and versatility.

Friction and wear performance of 3D-printed graphite/SiC composites with different graphite layer deflection angles

This study explores the combination of selective laser sintering 3D printing of graphite with the melt infiltration of silicon to produce graphite/SiC self-lubricating composites featuring graphite layers with varying deflection angles. The findings suggest that the deflection angle of graphite layers plays a crucial role in influencing the friction and wear characteristics of the composite materials. Specifically, graphite layers with deflection angles below 45° result in surface crushing and the stacking of lubricating films, leading to a noticeable ploughing effect. Conversely, deflection angles exceeding 60° cause, the graphite layers to break easily within the substrate, making it challenging to consistently provide lubrication over an extended period, consequently resulting in severe abrasive wear. In the range of 45° to 60° deflection angles, the graphite layers exhibit a tendency towards sliding dispersion, facilitating the dynamic filling of surface pits and scratches. This behavior contributes to the demonstration of low friction coefficients (ranging from 0.11 to 0.14) and exceptional wear resistance (measured at 3.23 to 3.79 ×10−6 mm3/Nm).

3D printed dispersible efavirenz tablets: A strategy for nasogastric administration in children

Enteral feeding tubes (EFTs) can be placed in children diagnosed with HIV which need nutritional support due to malnutrition. EFTs are the main route for medication administration in these patients, bringing up concerns about off label use of medicines, dose inaccuracy and tube clogging. Here we report for the first time the use of selective laser sintering (SLS) 3D printing to develop efavirenz (EFZ) dispersible printlets for patients with HIV that require EFT administration. Water soluble polymers Parteck® MXP and Kollidon® VA64 were used to obtain both 500 mg (P500 and K500) and 1000 mg printlets (P1000 and K1000) containing 200 mg of EFZ each. The use of SLS 3D printing obtained porous dosage forms with high drug content (20 % and 40 % w/w) and drug amorphization using both polymers. P500, K500 and K1000 printlets reached disintegration in under 230 s in 20 mL of water (25 ± 1 °C), whilst P1000 only partially disintegrated, possibly due to saturation of the polymer in the medium. As a result, the development of dispersible EFZ printlets using hydrophilic polymers can be explored as a potential strategy for drug delivery through EFTs in paediatrics with HIV, paving the way towards the exploration of more rapidly disintegrating polymers and excipients for SLS 3D printing.

A Novel 3D-Printed Gravity-Independent Air-Eliminating Filter for Rapid Intravenous Infusions.

INTRODUCTION: The absence of a consistent downward G vector can make separation of gases from liquids challenging, such as in field medicine without stable upright equipment or during spaceflight. This limits the use of medical equipment and procedures like administration of intravenous (IV) fluids in microgravity and can make field medicine hazardous. Administering IV fluids and medications in microgravity requires a technique to separate air from the liquid phase. Current commercial filters for separation of gases are incompatible with high flow and blood. We present a novel filter designed to provide adequate air clearance without a consistent downward G vector.METHODS: Inline air-eliminating filters were designed for use with IV fluid tubing in microgravity using computer-aided design software and printed using nylon 12 on an EOS Selective Laser Sintering 3D printer. A 0.2-μm membrane filter was adhered around a central, hollow pillar with external spiral baffles allowing separation and venting of air from the fluid. Results were compared against commercially available inline air-eliminating filters.RESULTS: The 3D-printed filters outperformed the commercial filters in both percentage of air removed and flow rates. The centrifugal, baffled filter had flow rates that far exceeded the commercial filters during rapid transfusion.DISCUSSION: IV fluid administration is an often underappreciated and a necessary basic requirement for medical treatment. An air-eliminating filter compatible with blood and rapid transfusion was developed and validated with crystalloid solutions to allow the successful administration of IV fluid and medication without a consistent downward G vector.Formanek A, Townsend J, Ottensmeyer MP, Kamine TH. A novel 3D-printed gravity-independent air-eliminating filter for rapid intravenous infusions. Aerosp Med Hum Perform. 2024; 95(6):327-332.

A Preclinical Trial Protocol Using an Ovine Model to Assess Scaffold Implant Biomaterials for Repair of Critical-Sized Mandibular Defects.

The present work describes a preclinical trial (in silico, in vivo and in vitro) protocol to assess the biomechanical performance and osteogenic capability of 3D-printed polymeric scaffolds implants used to repair partial defects in a sheep mandible. The protocol spans multiple steps of the medical device development pipeline, including initial concept design of the scaffold implant, digital twin in silico finite element modeling, manufacturing of the device prototype, in vivo device implantation, and in vitro laboratory mechanical testing. First, a patient-specific one-body scaffold implant used for reconstructing a critical-sized defect along the lower border of the sheep mandible ramus was designed using on computed-tomographic (CT) imagery and computer-aided design software. Next, the biomechanical performance of the implant was predicted numerically by simulating physiological load conditions in a digital twin in silico finite element model of the sheep mandible. This allowed for possible redesigning of the implant prior to commencing in vivo experimentation. Then, two types of polymeric biomaterials were used to manufacture the mandibular scaffold implants: poly ether ether ketone (PEEK) and poly ether ketone (PEK) printed with fused deposition modeling (FDM) and selective laser sintering (SLS), respectively. Then, after being implanted for 13 weeks in vivo, the implant and surrounding bone tissue was harvested and microCT scanned to visualize and quantify neo-tissue formation in the porous space of the scaffold. Finally, the implant and local bone tissue was assessed by in vitro laboratory mechanical testing to quantify the osteointegration. The protocol consists of six component procedures: (i) scaffold design and finite element analysis to predict its biomechanical response, (ii) scaffold fabrication with FDM and SLS 3D printing, (iii) surface treatment of the scaffold with plasma immersion ion implantation (PIII) techniques, (iv) ovine mandibular implantation, (v) postoperative sheep recovery, euthanasia, and harvesting of the scaffold and surrounding host bone, microCT scanning, and (vi) in vitro laboratory mechanical tests of the harvested scaffolds. The results of microCT imagery and 3-point mechanical bend testing demonstrate that PIII-SLS-PEK is a promising biomaterial for the manufacturing of scaffold implants to enhance the bone-scaffold contact and bone ingrowth in porous scaffold implants. MicroCT images of the harvested implant and surrounding bone tissue showed encouraging new bone growth at the scaffold-bone interface and inside the porous network of the lattice structure of the SLS-PEK scaffolds.

Small-strain folding of semi-rigid elastomer derives high-performance 3D-printable soft origami actuators

Elastomers with hyperelastic deformation bring prosperity to soft robotics, especially in constituting fluidic actuators, largely due to the merit of large deformation and airtightness. However, the large (typically 0.5–1.5 strain) in-plane stretching of such materials concurrent to motion generation inevitably causes energy loss, hinders force output and accuracy. Particularly, the high nonlinearity of the low-durometer (typically 10A to 30A Shore) hyperelastic elastomers makes the modeling and control of actuators a well-known challenge. In this work, we proposed an alternative approach of using semi-rigid elastomer of significantly larger durometer (70 A–100 A) to create the typical fluidic soft actuator with axial translation, by utilizing small-strain folding to generate motion. Deformation constraints and property programming are combined into a single-piece body, enabling easy fabrication by Selective Laser Sintering 3D-printing and post-treatment for origami patterned structure. Systematic analyses on the principles, modeling and design are presented. The long lifespan (over 1 million cycles), superior output linearity, high energy efficiency (more than 60% increase), and drastically improved force output (more than 98% increase) were validated experimentally, showing high potentials in enabling high-performance soft actuators that are easy to design, fabricate and drive, strong to use, and accurate to control, towards even wider applications.

Friction and wear performance of aluminum-based self-lubricating materials derived from the 3D printed graphite skeletons with different morphologies and orientations

Using selective laser sintering 3D printing, this study shapes graphite in sphere, flake, and fiber morphologies into skeletons with various orientations. These skeletons are then used to create graphite/aluminum alloy composite self-lubricating materials. The results show that graphite morphology and orientation greatly affect the friction and wear properties of these composites. Graphite fiber exhibits the worst friction and wear performance. Perpendicular flake graphite forms a uniform, continuous lubricating film with high thermal conductivity for heat dissipation, preventing severe wear. Spherical graphite modifies the friction surface, achieving the lowest friction coefficient (0.2 ± 0.02) and wear rate (6.64 ×10−4 mm3/Nm) due to protective film, filling, and ball bearing effects.

In Vitro and In Vivo testing of 3D-Printed Amorphous Lopinavir Printlets by SelectiveLaser Sinitering: Improved Bioavailability of a Poorly Soluble Drug.

The aim of this paper was to investigate the effects of formulation parameters on the physicochemical and pharmacokinetic (PK) behavior of amorphous printlets of lopinavir (LPV) manufactured by selective laser sintering 3D printing method (SLS). The formulation variables investigated were disintegrants (magnesium aluminum silicate at 5-10%, microcrystalline cellulose at 10-20%) and the polymer (Kollicoat® IR at 42-57%), while keeping printing parameters constant. Differential scanning calorimetry, X-ray powder diffraction, and Fourier-transform infrared analysis confirmed the transformation of the crystalline drug into an amorphous form. A direct correlation was found between the disintegrant concentration and dissolution. The dissolved drug ranged from 71.1 ± 5.7% to 99.3 ± 2.7% within 120min. A comparative PK study in rabbits showed significant differences in the rate and extent of absorption between printlets and compressed tablets. The values for Tmax, Cmax, and AUC were 4 times faster, and 2.5 and 1.7 times higher in the printlets compared to the compressed tablets, respectively. In conclusion, the SLS printing method can be used to create an amorphous delivery system through a single continuous process.

Sketching feasibility of additively manufactured different size gradient conventional hollow capsular shells (HCSs) by selective laser sintering (SLS): From design to applications

Additive manufacturing (AM) is widely used to fabricate 3D printed objects from Computer-aided Design (CAD) prepared using the SolidWorks CAD modelling software. Different printing techniques are used to fabricate desired 3D objects; among all these techniques, it is widely accepted that SLS is one of the most effective methods of 3D printing for fabricating drug-loaded solid oral dosage forms (SODFs) in bulk quantities using the single-step process. Different SODFs, such as pills, miniprintlets, dual miniprintlets, and tablets, were fabricated with different sizes and shapes. In this study, for the first time, we introduce SLS-mediated hollow capsular shells (HCSs) with the help of the SLS 3D printing technique. This work aimed to explore the sinterability and feasibility of sketching HCSs using the SLS-mediated sintering technique with different marketed sizes of capsules ranging from 000 to 5. Here, we have utilized Kolliphor P 188 (KP 188) and Kollidon SR (KSR) in a 1:1 ratio as a matrix-forming agent and 1% charcoal as a laser absorption-enhancing material. In accordance with the CAD models, we have fabricated the gradient conventional different sizes of HCSs ranging from 000 to 5 using the constant printing parameters and composition. Fabricated all biobased HCSs were subjected to the assessment of mechanistic and physicochemical parameters using varied analytical tools. In the current study, tartrazine dye is used to assess the release pattern from HCSs, which resulted in the modified release pattern. The adapted approach will be the futuristic approach to replace animal-based gelatin capsules with pharmaceutical-grade polymer-based HCSs with a modified release with optimum mechanical strength.

SLS 3D Printing To Fabricate Poly(vinyl alcohol)/Hydroxyapatite Bioactive Composite Porous Scaffolds and Their Bone Defect Repair Property.

Poly(vinyl alcohol) (PVA) exhibits a wide range of potential applications in the biomedical field due to its favorable mechanical properties and biocompatibility. However, few studies have been carried out on selective laser sintering (SLS) of PVA due to its poor thermal processability. In this study, in order to impart PVA powder the excellent thermal processability, the molecular complexation technology was performed to destroy the strong hydrogen bonds in PVA and thus significantly reduced the PVA melting point and crystallinity to 190.9 °C and 27.9%, respectively. The modified PVA (MPVA) was then compounded with hydroxyapatite (HA) to prepare PVA/HA composite powders suitable for SLS 3D printing. The final SLS 3D-printed MPVA/HA composite porous scaffolds show high precision and interconnected pores with a porosity as high as 68.3%. The in vitro cell culture experiments revealed that the sintered composite scaffolds could significantly promote the adhesion and proliferation of osteoblasts and facilitate bone regeneration, and the quantitative real-time polymerase chain reaction results further demonstrate that the printed MPVA/20HA scaffold could significantly enhance the expression levels of both early osteogenic-specific marker of alkaline phosphatase stain and runt-related transcription factor 2. Meanwhile, in in vivo experiments, it is encouragingly found that the resultant MPVA/20HA SLS 3D-printed part has an obvious effect on promoting the growth of new bone tissue as well as a better bone regeneration capability. This work could provide a promising strategy for fabrication of PVA scaffolds through SLS 3D printing, exhibiting a great potential for clinical applications in bone tissue engineering.

Abrasion‐Resistant and Enhanced Super‐Slippery Flush Toilets Fabricated by a Selective Laser Sintering 3D Printing Technology

Flush toilets waste a significant amount of water every day due to the unavoidable adhesions between human waste and the toilet surfaces. Super‐slippery surfaces can repel complex fluids and various viscoelastic solids, however, are easily broken by mechanical abrasions. Herein, the fabrication of an abrasion‐resistant super‐slippery flush toilet (ARSFT) is reported using a selective laser sintering 3D printing technology. Unlike traditional super‐slippery surfaces with limited thicknesses which can be easily worn away, the powder‐sintered strategy endows the ARSFT not only with a self‐supporting 3D complex shape but also with a porous structure that can accommodate considerable lubricants for an abrasion‐resistant super‐slippery property. As a result, the as‐prepared ARSFT remains clean after contacting with various liquids such as milk, yogurt, highly sticky honey, and starch gel mixed congee, demonstrating excellent repellence to complex fluids. Besides liquids, the ARSFT exhibits a high resistance to sticky synthetic feces. Notably, even after being abraded to 1,000 cycles of abrasion using sandpaper, the ARSFT maintains its record‐breaking super‐slippery capability. The concept of the 3D‐printed object with a superior abrasion‐resistant slippery ability will improve the development of super‐slippery materials and further save water consumption in the human society.

A general method for fabricating polymer-based intrinsic superhydrophobic objects by a selective laser sintering 3D printing strategy

Intrinsic superhydrophobic materials exhibit anti-wetting and abrasion-resistant capabilities simultaneously. However, the existing methods are highly restricted to specific synthetic material species. Here, we report a universal method for diverse polymeric materials to one-step prepare intrinsic superhydrophobic objects via a selective laser sintering (SLS) 3D printing technology. Through layer-by-layer sintering accumulation of polymeric powders and polytetrafluoroethylene (PTFE) grains, the intrinsic superhydrophobic 3D objects can be fabricated according to the programmed digital models. The as-printed samples remained anti-wetting capability even after 600 m sandpaper abrasion under 12.5 kPa, illustrating a record-breaking wear-resistant ability. Furthermore, we printed a chemical reaction platform and an underwater wear-resistant water-air transmedia vehicle, indicating the practical applications in harsh environments. Finally, we demonstrate the universality of this method for other eight kinds of polymers-PTFE composite systems. This work will greatly improve the practical application of superhydrophobic materials and promote the development of 3D printing functional materials.

Moisture‐Thermal Stable, Superhydrophilic Alumina‐Based Ceramics Fabricated by a Selective Laser Sintering 3D Printing Strategy for Solar Steam Generation

AbstractThe solar‐driven interface evaporation is one of the most promising technologies for desalination and wastewater purification. However, in the ebb and flow of the tide, water absorbed in the hydrophilic evaporator bottom would significantly change, leading to the shape deformation of the system and further failure of solar steam generation. Here it is reported that the moisture‐thermal stable and superhydrophilic alumina‐based ceramics can be fabricated by a selective laser sintering (SLS) 3D printing strategy. The printed alumina‐based ceramics possess superhydrophilicity. Along the side surface of the printed sample, a 5 µL water droplet can be fast absorbed in 14 ms. Most importantly, they can maintain stable and high evaporation efficiency even after being dried out for ten times, demonstrating the excellent physical resistance to continuous moisture‐thermal transition. Finally, the “I‐shaped” evaporators are printed with salt‐resistant ability, which can maintain a steady high evaporation efficiency in seawater and 20 wt% brine for long‐term steam generation process. The moisture‐thermal stable alumina‐based ceramics prepared in this work will provide inspiration for stable solar steam generation materials, and expand the development of 3D printing functional materials.

Powders of rGO-coated polyamide with special electrical properties for SLS 3D printing

Developing new polymer composites with special properties for 3D printing is one of the most attractive tasks. In our study, we have developed new polymer powders based on rGO-coated polyamide suitable for Selective Laser Sintering (SLS) printing. The obtained materials were characterized using optical microscopy, UV-Vis spectroscopy, scanning electron microscopy and dielectric spectroscopy. The size distribution of the powder particles, the angle of rest after an avalanche, the compactibility (Hausner ratio), the optical properties (absorption and transmission) of the powder monolayer, and the electrical conductivity of the obtained materials have been studied. It has been shown that the developed powders are suitable for the use in the framework of the SLS method, and can be applied to remove static electricity, as well as in reflective screens for electromagnetic radiation.

Abrasion-resistant superhydrophilic objects with anisotropic water transport capacities prepared by a selective laser sintering 3D printing strategy

Liquid directional manipulation has been widely used in the fields of microfluidic, microreactor, liquid separation and collection, sewage treatment. Most studies based on the construction of gradient structures on the substrate surface realized liquid directional transportation, but their fragile surfaces are vulnerable to external forces and can only transport thin water film according to the array thickness. Here, we report that abrasion-resistant superhydrophilic objects with anisotropic water transport capacities can be one-step constructed by selective laser sintering (SLS) the composites of hydrophilic glass beads (GBs) and thermoplastic phenol–formaldehyde resin (PF) grains. The long interlayer micro-slits between the adjacent printing layers cooperated with the inserted hydrophilic GBs formed long capillary channels, resulting in anisotropic water transport abilities on different printing surfaces. In addition, the abrasion-resistant ability endowed superhydrophilic mechanical stability. Furthermore, water could climb about ∼26 cm along the horizontal printed sample, showing excellent anti-gravity water transport ability. Finally, we demonstrated that the printed evaporators with diverse salt-resistant structures not only maintain long-term salt resistance, but also possess high evaporation efficiency. The superhydrophilic materials proposed in this study will lead the design and preparation of liquid directional transport materials and provide advanced inspiration for 3D printing functional materials.

Novel 3D printable bio-based and biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) microspheres for selective laser sintering applications

Selective laser sintering (SLS) has become the most popular additive manufacturing process due to its high accuracy, productive efficiency, and surface quality. However, currently there are still very few commercially available polymeric materials suitable for this technique. This research work focused on the fabrication and characterization of bio-based and biodegradable microspheres obtained by oil-in-water emulsion solvent evaporation, starting from a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) biopolymer matrix. First, the fabrication parameters were optimized to improve the morphological, thermal, and flowability properties of the synthetized microspheres. Once the best production conditions were established, the PHBH microspheres were further used to study their effective 3D printability on an SLS 3D printer using geometries varying from simple shapes to architectures with more complex internal patterns. The results of this research revealed that PHBH has promising applicability for the SLS technique. This study undertook the first step toward broadening the range of polymeric materials for this additive manufacturing technology. These findings will contribute to a greater and wider dissemination of the SLS technique in the future, as well as they will bring this manufacturing process closer to applications, such as the biomedical sector, where the use of biodegradable and biocompatible materials can add value to the final application.

Three-Dimensional Printing of Poly-L-Lactic Acid Composite Scaffolds with Enhanced Bioactivity and Controllable Zn Ion Release Capability by Coupling with Carbon-ZnO

Poly-L-lactic acid (PLLA) has gained great popularity with researchers in regenerative medicine owing to its superior biocompatibility and biodegradability, although its inadequate bioactivity inhibits the further use of PLLA in the field of bone regeneration. Zinc oxide (ZnO) has been utilized to improve the biological performance of biopolymers because of its renowned osteogenic activity. However, ZnO nanoparticles tend to agglomerate in the polymer matrix due to high surface energy, which would lead to the burst release of the Zn ion and, thus, cytotoxicity. In this study, to address this problem, carbon-ZnO (C-ZnO) was first synthesized through the carbonization of ZIF-8. Then, C-ZnO was introduced to PLLA powder before it was manufactured as scaffolds (PLLA/C-ZnO) by a selective laser sintering 3D printing technique. The results showed that the PLLA/C-ZnO scaffold was able to continuously release Zn ions in a reasonable range, which can be attributed to the interaction of Zn-N bonding and the shielding action of the PLLA scaffold. The controlled release of Zn ions from the scaffold further facilitated cell adhesion and proliferation and improved the osteogenic differentiation ability at the same time. In addition, C-ZnO endowed the scaffold with favorable photodynamic antibacterial ability, which was manifested by an efficient antibacterial rate of over 95%.

Selective laser sintering additive manufacturing of dosage forms: Effect of powder formulation and process parameters on the physical properties of printed tablets

Large batches of placebo and drug-loaded solid dosage forms were successfully fabricated using selective laser sintering (SLS) 3D printing in this study. The tablet batches were prepared using either copovidone (N-vinyl-2-pyrrolidone and vinyl acetate, PVP/VA) or polyvinyl alcohol (PVA) and activated carbon (AC) as radiation absorbent, which was added to improve the sintering of the polymer. The physical properties of the dosage forms were evaluated at different pigment concentrations (i.e., 0.5 and 1.0 wt%) and at different laser energy inputs. The mass, hardness, and friability of the tablets were found to be tunable and structures with greater mass and mechanical strength were obtained with increasing carbon concentration and energy input. Amorphization of the active pharmaceutical ingredient in the drug-loaded batches, containing 10 wt% naproxen and 1 wt% AC, was achieved in-situ during printing. Thus, amorphous solid dispersions were prepared in a single-step process and produced tablets with mass losses below 1 wt%. These findings show how the properties of dosage forms can be tuned by careful selection of the process parameters and the powder formulation. SLS 3D printing can therefore be considered to be an interesting and promising technique for the fabrication of personalized medicines.

Large-Scale, Abrasion-Resistant, and Solvent-Free Superhydrophobic Objects Fabricated by a Selective Laser Sintering 3D Printing Strategy.

Manufacturing abrasion-resistant superhydrophobic matters is challenging due to the fragile feature of the introduced micro-/nanoscale surface roughness. Besides the long-term durability, large scale at meter level, and 3D complex structures are of great importance for the superhydrophobic objects used across diverse industries. Here it is shown that abrasion-resistant, half-a-meter scaled superhydrophobic objects can be one-step realized by the selective laser sintering (SLS) 3D printing technology using hydrophobic-fumed-silica (HFS)/polymer composite grains. The HFS grains serve as the hydrophobic guests while the sintered polymeric network provides the mechanical strength, leading to low-adhesion, intrinsic superhydrophobic objects with desired 3D structures. It is found that as-printed structures remained anti-wetting capabilities even after undergoing different abrasion tests, including knife cutting test, rude file grinding test, 1000 cycles of sandpaper friction test, tape test and quicksand impacting test, illustrating their abrasion-resistant superhydrophobic stability. This strategy is applied to manufacture a shell of the unmanned aerial vehicle and an abrasion-resistant superhydrophobic shoe, showing the industrial customization of large-scale superhydrophobic objects. The findings thus provide insight for designing intrinsic superhydrophobic objects via the SLS 3D printing strategy that might find use in drag-reduce, anti-fouling, or other industrial fields in harsh operating environments.

Releasing fast and slow: Non-destructive prediction of density and drug release from SLS 3D printed tablets using NIR spectroscopy

Selective laser sintering (SLS) 3D printing is a revolutionary 3D printing technology that has been found capable of creating drug products with varied release profiles by changing the laser scanning speed. Here, SLS 3D printed formulations (printlets) loaded with a narrow therapeutic index drug (theophylline) were produced using SLS 3D printing at varying laser scanning speeds (100–180 mm/s). The use of reflectance Fourier Transform – Near Infrared (FT-NIR) spectroscopy was evaluated as a non-destructive approach to predicting 3D printed tablet density and drug release at 2 h and 4 h. The printed drug products formulated with a higher laser speed exhibited an accelerated drug release and reduced density compared with the slower laser scanning speeds. Univariate calibration models were developed based on a baseline shift in the spectra in the third overtone region upon changing physical properties. For density prediction, the developed univariate model had high linearity (R2 value = 0.9335) and accuracy (error < 0.029 mg/mm3). For drug release prediction at 2 h and 4 h, the developed univariate models demonstrated a linear correlation (R2 values of 0.9383 and 0.9167, respectively) and accuracy (error < 4.4%). The predicted vs. actual dissolution profiles were found to be statistically similar (f2 > 50) for all of the test printlets. Overall, this article demonstrates the feasibility of SLS 3D printing to produce drug products containing a narrow therapeutic index drug across a range of drug release profiles, as well as the potential for FT-NIR spectroscopy to predict the physical characteristics of SLS 3D printed drug products (drug release and density) as a non-destructive quality control method at the point-of-care.