Micro injection molding of individualised implants using 3D printed molds manufactured via digital light processing

Abstract Here, we demonstrate a manufacturing process for individualised, small-sized implant prototypes. Our process is promising for the manufacturing of drug-releasing (micro)implants to be implanted in the round window niche (RWN-I, solid body, free-form-shaped design, 1.1 x 2.7 x 3.1 mm) and for frontal neo-ostium implants (FO-I, tube-like design, length ~ 7 mm, Ø ~ 2-6 mm) for frontal sinus drainage. Implant prototypes are manufactured using micro injection molding (μIM). We use digital light processing (DLP) as a 3D printing technique for rapid tooling of accurate molds for the μIM process. A common acrylate-based photopolymer for stiff and high-detailed modelling but with low head deflection temperature of HDT = 60.5 °C is used for DLP 3D printing of the molds. The molds were 3D printed with a layer height of 50 μm in about 20 min (RWN-I) and 60 min (FO-I). For μIM investigations, we use liquid silicone rubber (LSR) as a biocompatible and medically relevant material. Micro injection molding of LSR was investigated using mold temperatures between Tmold = 110 °C (long tcuring ~ 2 h) up to Tmold = 160 °C (short tcuring ~ 5 min). As a result, small-sized, complex-shaped implant prototypes of LSR can be successfully manufactured via μIM using high Tmold = 160 °C and short curing time. DLP 3D printing material with relative low HDT = 60.5 °C was suitable for μIM. There is no significant wear of the molds, when used for a low number of μIM cycles (n ~ 8). Design of metal mold housing has to be suitable (perfect fit of mold, no cavities facing the molds surface for prevention of thermal expansion of mold into cavities).

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Cost-Effectively 3D-Printed Rigid and Versatile Interpenetrating Polymer Networks

Materials ◽

10.3390/ma14164544 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4544

Author(s):

Osman Konuray ◽

Arnau Sola ◽

Jordi Bonada ◽

Agnieszka Tercjak ◽

Albert Fabregat-Sanjuan ◽

...

Keyword(s):

3D Printing ◽

Polymer Networks ◽

Complex Form ◽

Interpenetrating Polymer Networks ◽

Dual Processing ◽

Digital Light Processing ◽

Superior Mechanical Properties ◽

3D Printed ◽

Acrylate Resin ◽

Printed Materials

Versatile acrylate–epoxy hybrid formulations are becoming widespread in photo/thermal dual-processing scenarios, especially in 3D printing applications. Usually, parts are printed in a stereolithography or digital light processing (DLP) 3D printer, after which a thermal treatment would bestow the final material with superior mechanical properties. We report the successful formulation of such a hybrid system, consisting of a commercial 3D printing acrylate resin modified by an epoxy–anhydride mixture. In the final polymeric network, we observed segregation of an epoxy-rich phase as nano-domains, similar to what was observed in a previous work. However, in the current work, we show the effectiveness of a coupling agent added to the formulation to mitigate this segregation for when such phase separation is undesired. The hybrid materials showed significant improvement of Young’s modulus over the neat acrylate. Once the flexible, partially-cured material was printed with a minimal number of layers, it could be molded into a complex form and thermally cured. Temporary shapes were readily programmable on this final material, with easy shape recovery under mild temperatures. Inspired by repairable 3D printed materials described recently, we manufactured a large object by printing its two halves, and then joined them covalently at the thermal cure stage with an apparently seamless union.

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3D Printing of Thermo-Sensitive Drugs

Pharmaceutics ◽

10.3390/pharmaceutics13091524 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1524

Author(s):

Sadikalmahdi Abdella ◽

Souha H. Youssef ◽

Franklin Afinjuomo ◽

Yunmei Song ◽

Paris Fouladian ◽

...

Keyword(s):

3D Printing ◽

Three Dimensional ◽

Fused Deposition Modelling ◽

Future Directions ◽

Digital Light Processing ◽

Fused Deposition ◽

Printing Technique ◽

3D Printed ◽

Semi Solid ◽

Selection Of

Three-dimensional (3D) printing is among the rapidly evolving technologies with applications in many sectors. The pharmaceutical industry is no exception, and the approval of the first 3D-printed tablet (Spiratam®) marked a revolution in the field. Several studies reported the fabrication of different dosage forms using a range of 3D printing techniques. Thermosensitive drugs compose a considerable segment of available medications in the market requiring strict temperature control during processing to ensure their efficacy and safety. Heating involved in some of the 3D printing technologies raises concerns regarding the feasibility of the techniques for printing thermolabile drugs. Studies reported that semi-solid extrusion (SSE) is the commonly used printing technique to fabricate thermosensitive drugs. Digital light processing (DLP), binder jetting (BJ), and stereolithography (SLA) can also be used for the fabrication of thermosensitive drugs as they do not involve heating elements. Nonetheless, degradation of some drugs by light source used in the techniques was reported. Interestingly, fused deposition modelling (FDM) coupled with filling techniques offered protection against thermal degradation. Concepts such as selection of low melting point polymers, adjustment of printing parameters, and coupling of more than one printing technique were exploited in printing thermosensitive drugs. This systematic review presents challenges, 3DP procedures, and future directions of 3D printing of thermo-sensitive formulations.

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DLP 3D Printing Meets Lignocellulosic Biopolymers: Carboxymethyl Cellulose Inks for 3D Biocompatible Hydrogels

Polymers ◽

10.3390/polym12081655 ◽

2020 ◽

Vol 12 (8) ◽

pp. 1655 ◽

Cited By ~ 4

Author(s):

Giuseppe Melilli ◽

Irene Carmagnola ◽

Chiara Tonda-Turo ◽

Fabrizio Pirri ◽

Gianluca Ciardelli ◽

...

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

3D Printing ◽

Carboxymethyl Cellulose ◽

Biomedical Applications ◽

Digital Light Processing ◽

Chemically Modified ◽

Significant Step ◽

3D Printed ◽

Biomedical Field

The development of new bio-based inks is a stringent request for the expansion of additive manufacturing towards the development of 3D-printed biocompatible hydrogels. Herein, methacrylated carboxymethyl cellulose (M-CMC) is investigated as a bio-based photocurable ink for digital light processing (DLP) 3D printing. CMC is chemically modified using methacrylic anhydride. Successful methacrylation is confirmed by 1H NMR and FTIR spectroscopy. Aqueous formulations based on M-CMC/lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator and M-CMC/Dulbecco’s Modified Eagle Medium (DMEM)/LAP show high photoreactivity upon UV irradiation as confirmed by photorheology and FTIR. The same formulations can be easily 3D-printed through a DLP apparatus to produce 3D shaped hydrogels with excellent swelling ability and mechanical properties. Envisaging the application of the hydrogels in the biomedical field, cytotoxicity is also evaluated. The light-induced printing of cellulose-based hydrogels represents a significant step forward in the production of new DLP inks suitable for biomedical applications.

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Characterization of Stereolithography Printed Soft Tooling for Micro Injection Molding

Micromachines ◽

10.3390/mi11090819 ◽

2020 ◽

Vol 11 (9) ◽

pp. 819 ◽

Cited By ~ 1

Author(s):

Daniel Dempsey ◽

Sean McDonald ◽

Davide Masato ◽

Carol Barry

Keyword(s):

Aspect Ratio ◽

Injection Molding ◽

Raw Materials ◽

Tool Material ◽

Mold Temperature ◽

Micro Injection Molding ◽

Digital Light Processing ◽

Electron Microscopies ◽

Aspect Ratios ◽

The Impact

The use of microfeature-enabled devices, such as microfluidic platforms and anti-fouling surfaces, has grown in both potential and application in recent years. Injection molding is an attractive method of manufacturing these devices due to its excellent process throughput and commodity-priced raw materials. Still, the manufacture of micro-structured tooling remains a slow and expensive endeavor. This work investigated the feasibility of utilizing additive manufacturing, specifically a Digital Light Processing (DLP)-based inverted stereolithography process, to produce thermoset polymer-based tooling for micro injection molding. Inserts were created with an array of 100-μm wide micro-features, having different heights and thus aspect ratios. These inserts were molded with high flow polypropylene to investigate print process resolution capabilities, channel replication abilities, and insert wear and longevity. Samples were characterized using contact profilometry as well as optical and scanning electron microscopies. Overall, the inserts exhibited a maximum lifetime of 78 molding cycles and failed by cracking of the entire insert. Damage was observed for the higher aspect ratio features but not the lower aspect ratio features. The effect of the tool material on mold temperature distribution was modeled to analyze the impact of processing and mold design.

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Multi-Material 3D Printing of a Customized Sports Mouth Guard: Proof-of-Concept Clinical Case

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph182312762 ◽

2021 ◽

Vol 18 (23) ◽

pp. 12762

Author(s):

Alexey Unkovskiy ◽

Fabian Huettig ◽

Pablo Kraemer-Fernandez ◽

Sebastian Spintzyk

Keyword(s):

3D Printing ◽

Free Form ◽

Proof Of Concept ◽

Virtual Design ◽

Digital Workflow ◽

Protective Function ◽

Drop On Demand ◽

3D Printed ◽

Mouth Guards ◽

Protective Performance

A multilayer mouth guard is known to have the best protective performance. However, its manufacturing in a digital workflow may be challenging with regards to virtual design and materialization. The present case demonstrates a pathway to fabricate a multilayer individualized mouth guard in a fully digital workflow, which starts with intraoral scanning. A free-form CAD software was used for the virtual design. Two various CAM techniques were used, including Polyjet 3D printing of rubber-like soft material and silicone printing using Drop-on-Demand technique. For both methods the outer layer was manufactured from more rigid materials to facilitate its protective function; the inner layer was printed from a softer material to aid a better adaptation to mucosa and teeth. Both 3D printed multilayer mouth guards showed a clinically acceptable fit and were met with patient appraisal. Their protective capacities must be evaluated in further clinical studies.

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Light-based 3D printing of functional polydimethylsiloxane- based microfluidic chips

Biomedical Science and Engineering ◽

10.4081/bse.2021.171 ◽

2021 ◽

Vol 4 (s1) ◽

Author(s):

Gustavo A. Gonzalez ◽

Annalisa Chiappone ◽

Kurt Dietliker ◽

Pirri C. Fabrizio ◽

Ignazio Roppolo

Keyword(s):

3D Printing ◽

Microfluidic Chips ◽

Digital Light Processing ◽

3D Printed

The objective of the work is to fabricate and functionalize 3D printed PDMS-based microfluidic chips through digital light processing DLP-3D printing.

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Effects of Cellulose Nanocrystal and Inorganic Nanofillers on the Morphological and Mechanical Properties of Digital Light Processing (DLP) 3D-Printed Photopolymer Composites

Applied Sciences ◽

10.3390/app11156835 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6835

Author(s):

Sang-U Bae ◽

Birm-June Kim

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Mechanical Strength ◽

Stress Transfer ◽

Cellulose Nanocrystal ◽

Morphological Properties ◽

Precipitated Calcium Carbonate ◽

Digital Light Processing ◽

3D Printed ◽

Cellulose Nanomaterials

Photopolymer composites filled with cellulose nanocrystal (CNC) and/or inorganic nanofillers were fabricated by using digital light processing (DLP) 3D printing. To investigate the effects of different CNC lyophilization concentrations and behaviors of CNC particles in the photopolymer composites, morphological and mechanical properties were analyzed. CNC loading levels affected the morphological and mechanical properties of the filled composites. Better CNC dispersion was seen at a lower lyophilization concentration, and the highest mechanical strength was observed in the 0.25 wt% CNC-filled composite. Furthermore, nano-precipitated calcium carbonate (nano-PCC) and nanoclay were added to photocurable resins, and then the effect of inorganic nanofillers on the morphological and mechanical properties of the composites were evaluated. By analyzing the morphological properties, the stress transfer mechanism of nano-PCC and nanoclay in the photopolymer composites was identified and related models were presented. These supported the improved mechanical strength of the composites filled with CNC, nano-PCC, and nanoclay. This study suggested a new approach using wood-derived cellulose nanomaterials and inorganic nanofillers as effective fillers for DLP 3D printing.

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Cytocompatibility of 3D printed dental materials for temporary restorations on fibroblasts

10.21203/rs.2.21028/v1 ◽

2020 ◽

Author(s):

Jung-Hyun Park ◽

Hyun Lee ◽

Jong-Woo Kim ◽

Ji-Hwan Kim

Keyword(s):

3D Printing ◽

Laser Scanning ◽

Dental Materials ◽

Three Dimensional ◽

Confocal Laser Scanning Microscope ◽

Confocal Laser ◽

Control Group ◽

Digital Light Processing ◽

3D Printed ◽

Materials Used

Abstract Background Three-dimensional (3D) printing is widely used in the fabrication of dental prostheses; however, the influence of dental materials used for 3D printing on temporary restoration of fibroblasts in tissues is unclear. Thus, the influence of different dental materials on fibroblasts were investigated. Methods Digital light processing (DLP) type 3D printing was used. Specimens in the control group were fabricated by mixing liquid and powder self-curing resin restoration materials. The temporary resin materials used were Model, Castable, Clear-SG, Tray, and Temporary, and the self-curing resin materials used were Lang dental, Alike, Milky blue, TOKVSO CUREFAST, and UniFast III. Fibroblast cells were cultured on each specimen and subsequently post-treated for analysis. Morphology of the adhered cells were observed using a confocal laser scanning microscope (CLSM) and a scanning electron microscope (SEM). Results CLSM and SEM cell imaging revealed that the 3D printed material group presented better cell adhesion with well-distributed filopodia compared to that in the conventional resin material group. Cell proliferation was significantly higher in the 3D printing materials. Conclusion This indicates that using resins fabricated by 3D printing technology rather than the ones fabricated by self-curing technology is recommended for the fabrication of dental temporary restorations.

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Consumer vs. High-End 3D Printers for Guided Implant Surgery—An In Vitro Accuracy Assessment Study of Different 3D Printing Technologies

Journal of Clinical Medicine ◽

10.3390/jcm10214894 ◽

2021 ◽

Vol 10 (21) ◽

pp. 4894

Author(s):

Lukas Wegmüller ◽

Florian Halbeisen ◽

Neha Sharma ◽

Sebastian Kühl ◽

Florian M. Thieringer

Keyword(s):

3D Printing ◽

Accuracy Assessment ◽

Subjective Assessment ◽

Fused Filament Fabrication ◽

Digital Light Processing ◽

Implant Surgery ◽

Surgical Guides ◽

3D Printers ◽

3D Printed

This study evaluates the accuracy of drill guides fabricated in medical-grade, biocompatible materials for static, computer-aided implant surgery (sCAIS). The virtually planned drill guides of ten completed patient cases were printed (n = 40) using professional (Material Jetting (MJ)) and consumer-level three-dimensional (3D) printing technologies, namely, Stereolithography (SLA), Fused Filament Fabrication (FFF), and Digital Light Processing (DLP). After printing and post-processing, the drill guides were digitized using an optical scanner. Subsequently, the drill guide’s original (reference) data and the surface scans of the digitized 3D-printed drill guide were superimposed to evaluate their incongruencies. The accuracy of the 3D-printed drill guides was calculated by determining the root mean square (RMS) values. Additionally, cast models of the planned cases were used to check that the drill guides fitted manually. The RMS (mean ± SD) values for the accuracy of 3D-printed drill guides were—MJ (0.09 ± 0.01 mm), SLA (0.12 ± 0.02 mm), FFF (0.18 ± 0.04 mm), and DLP (0.25 ± 0.05 mm). Upon a subjective assessment, all drill guides could be mounted on the cast models without hindrance. The results revealed statistically significant differences (p < 0.01) in all except the MJ- and SLA-printed drill guides. Although the measured differences in accuracy were statistically significant, the deviations were negligible from a clinical point of view. Within the limits of this study, we conclude that consumer-level 3D printers can produce surgical guides with a similar accuracy to a high-end, professional 3D printer with reduced costs.

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3D printing of metasurface-based dual-linear polarization converter

Flexible and Printed Electronics ◽

10.1088/2058-8585/ac3dff ◽

2021 ◽

Author(s):

Gyeongyeong Lee ◽

Yeong-Hoon Noh ◽

In-Gon Lee ◽

Ic-Pyo Hong ◽

Jong-Gwan Yook ◽

...

Keyword(s):

3D Printing ◽

Linear Polarization ◽

Orthogonal Polarization ◽

Polarization Conversion ◽

Polarization Converter ◽

Digital Light Processing ◽

Conductive Materials ◽

Complex Shapes ◽

3D Printed ◽

Materials Used

Abstract 3D printing using digital light processing (DLP) technology has been studied in various fields because of its ability to create complex shapes through a simple process. In this study, DLP 3D printing was employed in the implementation of the metasurface-based dual-linear polarization converter (DLPC). The unit cell of the metasurface-based DLPC for linear polarization conversion was designed consisting of the upper and lower dipole-pair antennas connected through vias and a shielding layer that electrically shields the antennas from each other, and its fabrication was based on the characterization results of the dielectric properties of the photocurable substrate materials and electrical properties of the conductive materials used for synthesizing the metasurface. The printability evaluation of dipole pairs, vias, and a shielding layer was carried out to implement the detailed structures of the DLPC in 3D printing. The electromagnetic wave transmission characteristics of the 3D-printed 8×8 array DLPC demonstrated an orthogonal polarization conversion, as predicted by the simulation results. This study confirmed that the DLP-based 3D printing technology can go beyond the existing functions of manufacturing objects and can be applied to the implementation of various electronics based on different meta-structures.

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