Stereolithographic Printing Research Articles

Development of Antifreezing, Printable, Adhesive, Tough, Biocompatible, High-Water Content Hydrogel for Versatile Applications.

Hydrogels with different functionalities such as printability, antifreezing properties, adhesion, biocompatibility, and toughness are being continually developed. However, it has been extremely challenging to design adhesive, antifreezing, tough, and biocompatible multifunctional hydrogels with complex shapes simultaneously and prepare them in a short period. In this paper, novel composite hydrogels, which consist of poly(vinyl alcohol) grafted with styrylpyridinium group (PVA-SbQ) and TEMPO-oxidized cellulose nanofibrils (CNF), were successfully synthesized via UV photo-cross-linking. In addition to UV photo-cross-linking, the PVA-SbQ/CNF hydrogels with different shapes could be rapidly printed by facile visible light-based stereolithography printing and laser direct-writing without any photoinitiators in 3 min and 30 s, respectively. The results show that PVA-SbQ/CNF hydrogels are biocompatible because there are no photoinitiators and cross-linkers required during the printing process under visible light. Moreover, the adhesive, antifreezing, mechanical properties, and water-binding capacity of PVA-SbQ/CNF with high-water contents improved significantly as the CNF contents increased. Such hydrogels, which combine multiple advantages, present great potential for application in wound dressings and portable devices with specific requirements for shapes, adhesion, toughness, and tolerance in extreme environments such as dry environments and low temperatures.

Biomimetic tissue phantoms for neurosurgical near-infrared fluorescence imaging.

Neurosurgical fluorescence imaging is a well-established clinical approach with a growing range of indications for use. However, this technology lacks effective phantom-based tools for development, performance testing, and clinician training. Our primary aim was to develop and evaluate 3D-printed phantoms capable of optically and morphologically simulating neurovasculature under fluorescence angiography. Volumetric digital maps of the circle of Willis with basilar and posterior communicator artery aneurysms, along with surrounding cerebral tissue, were generated. Phantoms were fabricated with a stereolithography printer using custom photopolymer composites, then visualized under white light and near-infrared fluorescence imaging. Feature sizes of printed components were found to be within 13% of digital models. Phantoms exhibited realistic optical properties and convincingly recapitulated fluorescence angiography scenes. Methods identified in this study can facilitate the development of realistic phantoms as powerful new tools for fluorescence imaging.

Investigation of LCD 3D Printing of Carbon Fiber Composites by Utilising Central Composite Design

The technology of additive manufacturing (AM) has transformed the fields of machinery, aerospace, and electronics. Adopting cost-effective, precise, and rapid procedures in AM is one of the major concerns of today’s industry. Stereolithography is a promising AM technique that is thought to meet these requirements. However, the fact that materials printed with stereolithography do not have good mechanical properties limits their application, such as in biomedicine and aerospace. Previous studies have shown the shortcomings of stereolithography printers. This research focuses on enhancing the mechanical characteristics of the polymer resin used in stereolithography (SLA)-like liquid crystal display (LCD) 3D printers by fabricating a new AM composite material with carbon fibers. For this reason, chopped carbon fibers (0.1 mm size) at amounts of 0.25 wt% and 0.5 wt% have been used with Acrylonitrile butadiene styrene (ABS)-like photopolymer transparent resin during the printing process, and three different print layer thicknesses were tested. For the design of the experiment (DoE), Q-DAS software was used to analyze the resulting data. A tensile-testing machine was utilized to determine the ultimate strength using the ASTM D638 standard. The results show an increase in the ultimate strength by adding carbon fiber to some extent, but after a certain percentage of carbon fiber added, the strength drops off.

Accuracy of tooth positioning in 3D-printing aided manufactured complete dentures: An in vitro study

PurposeIn this study, we propose a 3D printing-aided method for manufacturing complete dentures and evaluate its accuracy of artificial tooth positioning. MethodsComplete dentures were designed and 3D printed and put on a plaster cast; and pack and press technique was used to fabricate the final denture during which artificial teeth were inserted in the teeth holes formed by the printed denture. In this study, fused deposition moulding (FDM) and stereolithography (SLA) techniques were used to fabricate complete dentures (10 pairs of maxillary and mandibular dentures each). After 3D scanning the final dentures, 3D comparison between the scanned teeth on the denture and its computer-aided design (CAD) data was made and single-tooth deflection angles were measured to evaluate the tooth position. Values were compared using independent-sample t-tests or the Mann–Whitney U test. ResultsIn the result of 3D comparison, the root mean square values of artificial teeth were 0.107 ± 0.018 mm (SLA group) and 0.136 ± 0.023 mm (FDM group; P < 0.05). In the result of single-tooth deflection angles, the mandibular anterior teeth demonstrated the maximum deflection angle, followed by the molars, premolars, and maxillary anterior teeth. ConclusionsIt is feasible to fabricate complete dentures using 3D-printed complete dentures as prototypes and combine conventional methods. The accuracy of the final denture fabricated using SLA printing was better than that of dentures produced using the FDM method. Clinical significanceThe 3D printing-aided manufacturing for complete dentures refers to using the 3D-printed dentures as a prototype along with the traditional process to fabricate final dentures and is an effective alternative when the dentures cannot be directly processed using computer-aided manufacturing (CAM).

Radio-Frequency Energy Harvesting Using Rapid 3D Plastronics Protoyping Approach: A Case Study

Harvesting of ambient radio-frequency energy is largely covered in the literature. The RF energy harvester is considered most of the time as a standalone board. There is an interest to add the RF harvesting function on an already-designed object. Polymer objects are considered here, manufactured through an additive process and the paper focuses on the rapid prototyping of the harvester using a plastronic approach. An array of four antennas is considered for circular polarization with high self-isolation. The RF circuit is obtained using an electroless copper metallization of the surface of a 3D substrate fabricated using stereolithography printing. The RF properties of the polymer resin are not optimal; thus, the interest of this work is to investigate the potential capabilities of such an implementation, particularly in terms of freedom of 3D design and ease of fabrication. The electromagnetic properties of the substrate are characterized over a band of 0.5–2.5 GHz applying the two-transmission-line method. A circular polarization antenna is experimented as a rapid prototyping vehicle and yields a gain of 1.26 dB. A lab-scale prototype of the rectifier and power management unit are experimented with discrete components. The cold start-up circuit accepts a minimum voltage of 180 mV. The main DC/DC converter operates under 1.4 V but is able to compensate losses for an input DC voltage as low as 100 mV (10 μW). The rectifier alone is capable of 3.5% efficiency at −30 dBm input RF power. The global system of circularly polarized antenna, rectifier, and voltage conversion features a global experimental efficiency of 14.7% at an input power of −13.5 dBm. The possible application of such results is discussed.

Vat Photopolymerization Additive Manufacturing of Tough, Fully Recyclable Thermosets.

To advance the capabilities of additive manufacturing, novel resin formulations are needed that produce high-fidelity parts with desired mechanical properties that are also amenable to recycling. In this work, a thiol-ene-based system incorporating semicrystallinity and dynamic thioester bonds within polymer networks is presented. It is shown that these materials have ultimate toughness values >16 MJ cm-3, comparable to high-performance literature precedents. Significantly, the treatment of these networks with excess thiols facilitates thiol-thioester exchange that degrades polymerized networks into functional oligomers. These oligomers are shown to be amenable to repolymerization into constructs with varying thermomechanical properties, including elastomeric networks that recover their shape fully from >100% strain. Using a commercial stereolithographic printer, these resin formulations are printed into functional objects including both stiff (E ∼ 10-100 MPa) and soft (E ∼ 1-10 MPa) lattice structures. Finally, it is shown that the incorporation of both dynamic chemistry and crystallinity further enables advancement in the properties and characteristics of printed parts, including attributes such as self-healing and shape-memory.

Diarylethene Photoswitches and 3D Printing to Fabricate Rewearable Colorimetric UV Sensors for Sun Protection

AbstractDespite education campaigns linking sun overexposure and skin cancer, it remains one of the leading preventable cancer diagnoses. Skin cancer risk is correlated with overexposure to UV light in sunlight and can be prevented by avoiding exposure. While sun protection can be achieved using sunscreen and clothing, people must be made aware of their risk to facilitate behavior change. Herein, new rewearable UV sensors which overcome the single‐use limitations of other products are presented. These sensors utilize diarylethene photoswitches, which develop a colored appearance upon exposure to UV and are reset to colorless by green light (&lt;10 min). These photoswitches are incorporated into a range of materials, enabling the use of advanced manufacturing to develop highly desirable consumer products. 3D stereolithographic printing is used to prototype sensors, with complex geometries and appealing aesthetics, that can be worn by users. The UV sensitivity of these devices is tuned by incorporating chromophores, meeting the needs of diverse skin types. The colorimetric response allows for direct visual feedback to the user, or quantification using photography, allowing for dosimetry of UV exposure. These new reusable devices aim to reduce people's exposure to UV, while reducing the waste generated by single‐use devices.

Influence of print orientation and wet-dry storage time on the intaglio accuracy of additively manufactured occlusal devices

Statement of problemDifferent factors can affect the manufacturing accuracy of additively manufactured dental devices; however, the influence of print orientation and wet-dry storage time on their intaglio accuracy remains uncertain. PurposeThe purpose of this in vitro study was to assess the effect of print orientation (0, 45, 70, and 90 degrees) and wet-dry storage time (0, 30, 60, and 90 days) on the intaglio accuracy of additively manufactured occlusal devices. Material and methodsAn occlusal device design was obtained in a standard tessellation language (STL) file format (control file) which was used to fabricate all the specimens by using a stereolithography printer (Form 3+) and a biocompatible resin material (Dental LT Clear Resin, V2). Four groups were created based on the print orientation used to manufacture the specimens: 0, 45, 70, and 90 degrees. Each group was divided into 4 subgroups depending on the time elapsed between manufacturing and accuracy evaluation: 0, 30, 60, and 90 days. For the subgroup 0, a desktop scanner (T710) was used to digitize all the specimens. The 30-day subgroup specimens were stored for 30 days with the following daily storage protocol: 16 hours inside a dry lightproof container, followed by 8 hours in artificial saliva (1700-0305 Artificial Saliva) inside the same lightproof container. The specimens were then digitized by following the same procedures used for subgroup 0. For the subgroups 60 and 90, the identical procedures described for subgroup 30 were completed but after 60 and 90 days of storage, respectively. The reference STL file was used to measure the intaglio discrepancy with the experimental scans obtained among the different subgroups by using the root mean square error calculation. Two-way ANOVA and post hoc Tukey pairwise comparison tests were used to analyze the data (α=.05). ResultsPrint orientation (P<.001) and usage time (P<.001) were significant predictors of the trueness value obtained. Additionally, the 0-degree print orientation at day 0 group demonstrated the best trueness value among all the groups tested (P<.05). No significant trueness discrepancies were found among the 45-, 70-, and 90-degree print orientation, or among the 30, 60, and 90 days of storage. A significant precision difference was found in the variance between print orientation groups across usage time subgroups. ConclusionsThe print orientation and wet-dry storage times tested influenced the trueness and precision of the intaglio surfaces of the occlusal devices manufactured with the 3D printer and material selected.

Error analysis of stages involved in CBCT-guided implant placement with surgical guides when different printing technologies are used

Statement of problemDigital light processing (DLP), continuous liquid interface printing (CLIP), and stereolithography (SLA) technologies enable 3-dimensional (3D) printing of surgical guides. However, how their accuracy compares and how accuracy may affect subsequent steps in guided surgery is unclear. PurposeThe purpose of this in vitro study was to investigate the fabrication and seating accuracy of surgical guides printed by using DLP, SLA, and CLIP technologies and evaluate the positional deviation of the osteotomy site and placed implant compared with the digital implant plan. Material and methodsTwenty-one polyurethane models were divided into 3 groups and used to plan implants and design surgical guides. The guides were fabricated by using DLP, SLA, or CLIP 3D printers (n=7) and scanned, and the scan file was compared with the digital design file to analyze the fabrication accuracy at the intaglio and overall external surfaces using root mean square (RMS) values. The triple scan protocol was used to evaluate the seating accuracy of the guides on their respective models. Osteotomies were prepared on models by using the guides followed by a microcomputed tomography image of each osteotomy. The implants were placed through the guides, the scan bodies were tightened to implants, and the models were scanned to obtain the images of placed implant position. Osteotomy and placed implant images were used to calculate the entry point, apex, and long axis deviations from the planned implant position with a software program. A 2-way repeated-measures ANOVA of the RMS data was used to analyze printing and seating trueness, and homogeneity of variance analyses were used at each surface for precision. A 3-way repeated-measures ANOVA was used to analyze distance deviations over the stages (osteotomy and final implant) and locations studied, and a 2-way repeated-measures ANOVA was used for angular deviations. Homogeneity of variance analyses were performed for precision (α=.05). ResultsThe 3D printer type significantly affected the trueness of the guide at the intaglio surface (P<.001). SLA guides had the lowest mean RMS (59.04 μm) for intaglio surface, while CLIP had the highest mean RMS (117.14 μm). Guides from all 3D printers had low variability among measured deviations and therefore were similarly precise. The seating accuracy of SLA and DLP guides was not significantly different, but both had lower mean RMS values than CLIP (P=.003 for SLA, P=.014 for DLP). There were no significant interactions between the stage of surgery, the printer type, or the location of implant deviation (P=.734). Only the location of deviation (cervical versus apical) had a significant effect on distance deviations (P<.001). The printer type, stage of surgery, and their interaction did not significantly affect angular deviations (P=.41). ConclusionsThe 3D printing technology affected printing trueness. The intaglio surface trueness was higher with SLA and overall trueness was higher with the CLIP printer. The precision of all guides was similarly high. Guides from SLA and DLP printers had more accurate seating than those from CLIP. Higher deviations were observed at the apex; however, osteotomy and final implant position did not significantly differ from the digitally planned position.

Indirect Applications of Additive Manufacturing for Antennas

We report the fabrication methodology of stereolithography (SLA) printed molds for metal and resin cast antennas. In the first method, a conical horn created using metal cast molds printed from a glass-filled resin utilizes a casting technique allowing for low-cost 3D printing to fabricate metal antennas, reducing the losses incurred by metallized plastics, while still producing complex geometries quickly. This metal cast conical horn is compared to a horn constructed using a more traditional 3D printing method. The second casting method demonstrates the interchangeability between creating parts via SLA printing with a glass-filled resin and using the same resin cast into a reusable Polydimethylsiloxane (PDMS) mold. We demonstrate this method by casting an interchangeable slug for a capacitively coupled, mechanically reconfigurable disk loaded monopole. Simulated and experimental data are presented for S11, and Gain. Simulated BW, directivity, gain and efficiency as a function of frequency are presented. The results indicate that the 3D printed metal casting process produces antennas with a higher gain and lower return loss than metallized resin antennas. The method is suitable for difficult geometries requiring resolution of at least 50 lm. The capacitively coupled disk loaded monopole demonstrates the versatility of 3D printing in antenna fabrication.

A 3-D Printed Ku-Band Waveguide Filter Based on Novel Rotary Coupling Structure

A Ku-band (12–18 GHz) waveguide bandpass filter has been designed, fabricated using stereolithography (SLA) printing, measured, and presented. The filter is composed of five coupled TE101 resonators, where the external/internal couplings are implemented through the rotation of resonators. This novel filter structure is superior to conventional filters based on irises, in terms of reduced sensitivity to fabrication inaccuracies (i.e., allowing larger tolerance in the fabrication process), as the coupling strength depends on the mutual rotation angle between resonators and input/output waveguides. This simple inline filter structure also allows the generation of transmission zero (TZ), by altering the rotation angles of resonators. A Ku-band prototype filter, with a center frequency of 14 GHz, a bandwidth of 0.8 GHz, a return loss of 20 dB, and a TZ at 14.8 GHz, has been successfully demonstrated, and this verifies the proposed concept.

Stereolithography Assisted Controllable Random Lasing Device for Tunable Threshold, Linewidth, and Wavelength

Additive manufacturing provides flexibility in making structures according to specific geometry requirements. Advances in this technology, including sophisticated laser‐based stereolithography (SLA) technique, have paved the way to fabricate structures with layer resolutions up to 25 μm. Although the feasibility of random lasing is shown in 3D‐printed structures, a study on varying lasing properties using SLA printing technique with continuous wave laser pumping is not studied yet in depth. Herein, SLA is used to fabricate structures conducive for random lasing. Randomly distributed vertical cylindrical microchannels are fabricated on a 1 cm × 1 cm photoresin chip of thickness 2 mm. The geometry of structures makes it viable for liquid optical gain media to be injected into the cylindrical channels. The random lasing characteristics are demonstrated including threshold and linewidths. Tunability in peak lasing wavelength, required threshold, and minimum achievable linewidth are demonstrated by changing the diameter of the microchannels. Further, it is shown that by changing the hole diameter from 260 to 470 μm, a wavelength tunability of approximately 22 nm is achieved. This structure expects to significantly contribute for its use as an on‐chip photonic sensor, wherein liquid analytes achieved can be injected and sensed using optical parameters, and for on‐chip spectroscopy applications.

Low-loss three-dimensional printed ridge waveguides using stereolithography

Ridge waveguides were three-dimensional printed using a stereolithography printer and hydrogel resin formulation. The ridge waveguides were 13, 20, and 30 μm wide, 3 to 6 μm high, and 4.4 mm long. The loss of the waveguides was measured using the cutback method and ranged between 0.28 and 1.2 cm − 1 (or 1.2 and 5.2 dB / cm) with transmittances up to 0.94 (0.27 dB coupling loss) using 635 nm light. Our work demonstrates a quick and inexpensive method to fabricate integrated photonic chips with the promise to fabricate more complex photonic devices and systems.

EVALUATING THE IMPACT OF SOLID MICRONEEDLES ON THE TRANSDERMAL DRUG DELIVERY SYSTEM FOR Ɣ-ORYZANOL

Objective: This study's goals were to develop a minimally invasive array of biocompatible polymeric solid microneedles and formulate a transdermal patch of drug Ɣ-Oryzanol as per poke and patch technology. Methods: Scanning electron microscopy was used to analyse the morphology of the solid microneedle arrays, which were created using a stereolithography (SLA) printer with high-resolution capabilities (25 and 140 microns for the z and x axes, respectively). Transdermal Patches of Ɣ-Oryzanol were formulated and evaluated for various characterization parameters. Further, the produced microneedle-transdermal drug delivery system of Ɣ-Oryzanol was examined for microneedle insertion skin and permeation of the drug across the porcine skin. Results: Solid microneedle arrays were manufactured using biocompatible Class I Dental SG resin having dimensions of 600 µm height and 300 µm width with tip diameters of 30 µm and 1.85 mm interspacing (Distance from tip to tip) and they were strong enough to penetrate porcine skin to a depth of 381.356 µm crossing the stratum corneum layer without causing any structural changes. Transdermal patches containing Ɣ-Oryzanol were formulated using different ratios of HPMC: Eudragit E-100. Good, consistent, and transparent films were formulated when the thickness of the film ranges between 0.516±0.25-0.628±0.21 mm, average weights ranged from 168.23±2.61to171.22±1.25(10/cm2), folding endurance ranged in between 10 folds to 12 folds for all the formulations with tensile strength lie between the 0.365 kg/mm2 to 0.465 kg/mm2. All the formulations showed good drug content between 99.3±0.06%-90.4±1.64% with 100% flat surfaces. Moisture content was found in the range of 2.012±0.013 to 4.213±0.031. Drug permeation studies reveal that compound Ɣ-Oryzanol transdermal patches didn’t show significant permeation across porcine skin (4.802.25 g/cm2) without piercing with microneedles while after poking skin using microneedles (74.502.35 g/cm2) drug showed good penetration properties. It was found that the amount of drug delivered increased to 44.251.57 g/cm2 at 2 min, which was 14.502.35 g/cm2 at 1 min to 4 min 74.502.35 g/cm2. Conclusion: Successful preparation of the Microneedle-Transdermal drug delivery system of Ɣ-Oryzanol and their evaluation indicated that the quality and consistency of the formulated preparation were excellent. With advantages in terms of lowered dose frequency, better patient compliance, and bioavailability, this may find use in the therapeutic field.

Effect of cross-head speed on mechanical properties of photosensitive resins used in three-dimensional printing of a stereolithographic elastomer

Abstract It is known that the strain rate affects significantly the mechanical properties of the engineering materials. The aim of this study is to investigate the effect of the cross-head speed on the mechanical properties of acrylate and methacrylate-based oligomer/monomer materials of the specimens produced by Stereolithography (SLA) printer. The characteristic mechanical properties of materials, such as modulus of elasticity, Poisson’s ratio, and the ultimate strength depending on low strain rate levels were explored. The fractured surfaces of the tensile test specimens were examined by Scanning Electron Microscopy (SEM). Based on the experimental results, it is concluded the mechanical properties of the photosensitive resins are quite sensitive to the tensile test speeds.

3D-Printable Cellular Composites for the Production of Recombinant Proteins.

The incorporation of living cells into materials promises both significant challenges and new possibilities. Although recent years have seen important advances in this field, there is still much to be learned about engineering interfaces between cells and materials. Here, we present a new class of 3D-printable materials, based on poly(N-hydroxymethylacrylamide) (PNHMAA), in which the spore-forming bacterium Bacillus subtilis is effectively cross-linked into the surrounding polymeric scaffold. After dehydration and subsequent re-swelling in nutrient-rich media, embedded cells and spores become metabolically active and are capable of heterologous protein production and secretion. Strikingly, the leak-free scaffold allows protein production while preventing escape of embedded cells. The successful construction of complex three-dimensional structures by stereolithographic printing of living PNHMAA composite materials suggests utility in a broad range of applications.

Functional aerogel coatings on tetrakaidecahedron lattice

This paper reports a new method of functional metamaterial structure fabrication based on ultra-porous aerogel skins introduced on the surfaces of solid tetrakaidecahedron lattices obtained via 3D-printing tools. The solid tetrakaidecahedron lattice shapes are first fabricated from acrylate resin systems using a stereolithography printer. The lattice is then coated with a skin of polyimide gel via sol–gel reaction process, post-curing, and solvent-aging. The aerogel skin is recovered from the gel using supercritical drying. The lattice is found uniformly coated with polyimide aerogel skin as confirmed from examination of surface morphology via scanning electron microscopy and X-ray tomography imaging. The concept is extended to coatings by silica and Kevlar aerogel systems. The mechanical and thermal properties of the resultant materials and a set of applications are discussed.

Impact of oleuropein on LCD-based stereolithography-assisted fabrication of 3D printed PEGDMA hydrogels

Nowadays, personalized nutrition/medicine has become one of the hot topics to modify target agent dosage and allow personalized treatment by changing geometries of printed gels. Light-induced 3D printing technologies enable fabrication of solid forms by mixing photocurable monomer with drug/active agents. However, the use of synthetic polymers and toxic photoinitiators (PIs) makes a concern for SLA printing. In this study, it was firstly aimed to use natural PI, riboflavin in precursor resin. Then, poly (ethylene glycol) dimethacrylate (PEGDMA) based hydrogels embedded with oleuropein (OLE) were printed through UV-induced polymerization at varying shapes (radiator, hexagonal, square, ring, and round). Olive leaf extract including OLE as main antioxidant source is a valuable waste product for sustainability and additive/nutraceutical use in the food and pharmaceutical industry. This work investigated fabricated 3D gels in terms of their printability, physical properties, physicochemical features, and drug-release profiles. More importantly, encapsulated OLE within 3D printed gel was examined to see the effect of light-induced printing on its antioxidant acitivity. 3D OLE added gels showed very high printability ratios which were close to 1 whereas control gel without OLE was not printed successfully. Moreover, the results confirmed the existence of antioxidant activity (up to 87%) of 3D gels even after UV-induced printing. Based on surface area/volume (SA/V) ratio, radiator and square gels gave the highest release as they had high SA/V proportions. Structural changes in the compounds after UV curing process was also confirmed by FT-IR spectrum. The drug release profiles followed the Peppas model having n value in the range of 0.44–0.54, demonstrating that the release was mostly affected by diffusion. This study shows potential contribution to pharmaceutical and food industries in terms of designing personalized OLE dosages using the Stereolithography (SLA) printing with controlled release by manipulating geometry alone.

Photoinitiated Olefin Metathesis and Stereolithographic Printing of Polydicyclopentadiene

Recent progress in photoinitiated ring-opening metathesis polymerization (photoROMP) has enabled the lithographic production of patterned films from olefinic resins. Recently, we reported the use of a latent ruthenium catalyst (HeatMet) in combination with a photosensitizer (2-isopropylthioxanthone) to rapidly photopolymerize dicyclopentadiene (DCPD) formulations upon irradiation with UV light. While this prior work was limited in terms of catalyst and photosensitizer scope, a variety of alternative catalysts and photosensitizers are commercially available that could allow for tuning of thermomechanical properties, potlifes, activation rates, and irradiation wavelengths. Herein, 14 catalysts and 8 photosensitizers are surveyed for the photoROMP of DCPD and the structure–activity relationships of the catalysts examined. Properties relevant to stereolithography additive manufacturing (SLA AM)─potlife, irradiation dose required to gel, conversion─are characterized to develop catalyst and photosensitizer libraries to inform development of SLA AM resin systems. Two optimized catalyst/photosensitizer systems are demonstrated in the rapid SLA printing of complex, multidimensional pDCPD structures with microscale features under ambient conditions.

Durable scalable 3D SLA-printed cuff electrodes with high performance carbon + PEDOT:PSS-based contacts.

The stimulation and recording performance of implanted neural interfaces are functions of the physical and electrical characteristics of the neural interface, its electrode material and structure. Therefore, rapid optimization of such characteristics is becoming critical in most clinical and research studies. This paper describes the development of an upgraded 3D printed cuff electrode shell design containing a novel intrinsically conductive polymer (ICP) for stimulation and recording of peripheral nerve fibers. A 3D stereolithography (SLA) printer was used to print a scalable, custom designed, C-cuff electrode and I-beam closure for accurate, rapid implementation. A novel contact consisting of a percolated carbon graphite base electrodeposited with an intrinsically conductive polymer (ICP), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) produced a PEDOT:PSS + carbon black (CB) matrix that was used to form the electrochemical interface on the structure. Prototype device performance was tested both in-vitro and in-vivo for electrical chemical capacity, electrochemical interfacial impedance, surgical handling, and implantability. The in-vivo work was performed on the sciatic nerve of 25 anesthetized Sprague Dawley rats to demonstrate recording and stimulating ability. Prototypes of different spatial geometries and number of contacts (bipolar, tripolar, and tetrapolar) were designed. The design was successfully printed with inner diameters down to 500 μm. Standard bipolar and tripolar cuffs, with a 1.3 mm inner diameter (ID), 0.5 mm contact width, 1.0 mm pitch, and a 1.5 mm end distance were used for the functional tests. This geometry was appropriate for placement on the rat sciatic nerve and enabled in-vivo testing in anesthetized rats. The contacts on the standard bipolar electrode had an area of 2.1 × 10-2 cm2 . Cyclic voltammetry on ICP coated and uncoated graphite contacts showed that the ICP increased the average charge storage capacity (CSC) by a factor of 30. The corresponding impedance at 1Hz was slightly above 1 kΩ, a 99.99% decrease from 100 kΩ in the uncoated state. The statistical comparison of the pre- versus post-stimulation impedance measurements were not significantly different (p-value > 0.05). The new cuff electrode enables rapid development of cost-effective functional stimulation devices targeting nerve bundles less than 1.0 mm in diameter. This allows for recording and modulation of a low-frequency current targeted within the peripheral nervous system.