On the intrinsic sterility of 3D printing

Open science and 3D printing are making it easier than ever for researchers to embrace do-it-yourself lab tools. Open science and 3D printing are making it easier than ever for researchers to embrace do-it-yourself lab tools.

Objectives: Three-dimensional (3D) printing has gained significance for human health-care applications in recent years. Some of these applications include obtaining models which mimic anatomical parts. One other parallel development in the biological research area is the development of 3D cell cultures. Such cultures are now becoming the material of choice for in vitro experiments, fast replacing the traditional adherent/monolayer 2D culture approaches. We present here, a method to obtain 3D prints of 3D aggregates of three human cancer cell lines. Such 3D prints can be useful models to understand solid tumor morphologies and also as effective teaching models. Materials and Methods: Photomicrographs of the 3D aggregates of the human cancer cell lines SiHa, MCF-7, and A549 (human cervical cancer, breast cancer, and non-small cell lung cancer cell lines, respectively) were obtained using inverted phase contrast microscopy. Conversion of normal jpeg images into 3D files was performed using the lithophane method and CAD files obtained. The CAD files thus generated were used to print the objects using the Stratasys Polyjet J750 3D Printer. Results: We could obtain 3D prints of SiHa, MCF-7, and A549 (human cervical cancer, breast cancer, and non-small cell lung cancer cell lines, respectively) 3D aggregates/spheroids. Conclusion: It is hoped that this approach will be useful for studying solid tumor morphologies in finer details. Furthermore, other benefits of such 3D prints would be in them being excellent models for teaching purposes.

3-Dimensional (3D) printing has become a common tool to aid implant molding for cranioplastic surgery of large skull defects. Until now, 3D printing of cranial implants itself has not been used, mainly because of medicolegal concerns. With a 3D printer developed for printing medical applications and with implant-grade polyetheretherketone (PEEK) filament available, we established a workflow (in compliance with medical device regulations) to 3D print cranial implants for cranioplastic surgery directly at the point of care (POC). Here, we describe the implementation of 3D printing these PEEK implants for cranioplastic surgery at our academic hospital. A thorough design and 3D printing process, in accordance with local medical device regulations, was developed. Implants are digitally designed based upon pre- and post-craniectomy cranial computed tomography scans by trained 3D printing experts from the department of medical engineering at our institution. Implants are then produced on a medical 3D printer with implant-grade PEEK filament using the fused filament fabrication process. After postprocessing and steam sterilization, implantation for reconstruction of the skull can be performed. Cranioplastic surgery with a 3D-printed PEEK implant was performed at our institution in a patient with a large frontotemporoparietal skull defect after traumatic brain injury with consecutive decompressive craniectomy. No intra- or post-operative complications occurred. Postoperative cranial computed tomography scans showed perfect reconstruction of precraniectomy skull shape. The aesthetic result was promising and satisfactory to the patient. This novel 3D printing workflow enables the production of patient-specific cranial implants from PEEK, to reconstruct large skull defects directly at the POC in accordance with the European Medical Device Regulation. This marks an unprecedented technological and legal advancement, enabling the hospital infrastructure not only to deliver the cranioplastic surgery itself, but also additive manufacturing of the implant directly at the POC.

Background: The interim fixed prostheses are also a vital part and parcel of the prosthodontic treatment and give continuity to the prosthesis, esthetic reinforcement, and psychological confidence between the definitive restoration placement after the intermediate period. There has been a growing application in the digital fabrication methods especially CAD/CAM milling and three-dimensional (3D) printing that have led to the emergence of new polymer essentially designed to enhance the mechanical and clinical performance of interim restorations. Graphene reinforcement has recently been suggested as an attractive solution in order to improve the performance of polymeric dental materials in terms of strength and durability, yet there has been scarce evidence between its performance when subjected to various digital manufacturing methods. Objective: To evaluate the psychosocial effects and mechanical performance of the CAD/CAM-milled and 3D-printed interim fixed prostheses reinforced with graphene to compare the two groups of the proposed study using an integrated clinical and in-vitro study design. Methods: A mixed-method comparative study was undertaken and it comprised of a clinical study of interim fixed prostheses and an in-vitro study of mechanical and optical properties. Interim restorations made with graphene reinforced materials were tested clinically based on patient-based outcome measures and clinician-based assessment criteria. Simultaneously, the laboratory testing was conducted to determine the fracture resistance, flexural strength, marginal adaptation, failure mode, color stability, translucency, opalescence and roughness on the surface according to applicable standards of the ISO guidelines. The statistical analysis was conducted on the bases of descriptive statistics and inferential testing, to compare the results between the groups. Results: Interim prostheses reinforced with graphene prepared with CAD/CAM milling exhibited better mechanical performance parameters whereas 3D-printed restorations were similar in respect to clinical acceptability and patient satisfaction. The results had considerable differences in the chosen mechanical and optical properties between processes of fabrication. Conclusion: Graphene-reinforced interim prostheses that have been milled by CAD/CAM and 3D-printed showed acceptable clinical and laboratory performance. Evidence of mechanical behavior and chosen esthetic parameters differences imply possible impact of fabrication method on material performance, which supports the necessity to use evidence-based material choice when working with interim prosthodontics.

In the last decade, an emerging three-dimensional (3D) printing technique named freeform 3D printing has revolutionized the biomedical engineering field by allowing soft matters with or without cells to be printed and solidified with high precision regardless of their poor self-supportability. The key to this freeform 3D printing technology is the supporting matrices that hold the printed soft ink materials during omnidirectional writing and solidification. This approach not only overcomes structural design restrictions of conventional layer-by-layer printing but also helps to realize 3D printing of low-viscosity or slow-curing materials. This article focuses on the recent developments in freeform 3D printing of soft matters such as hydrogels, cells, and silicone elastomers, for biomedical engineering. Herein, we classify the reported freeform 3D printing systems into positive, negative, and functional based on the fabrication process, and discuss the rheological requirements of the supporting matrix in accordance with the rheological behavior of counterpart inks, aiming to guide development and evaluation of new freeform printing systems. We also provide a brief overview of various material systems used as supporting matrices for freeform 3D printing systems and explore the potential applications of freeform 3D printing systems in different areas of biomedical engineering.

Robotic actuators such as geared MR actuators must improve their torque capacities and reduce their size to increase system integration density. MR clutches are at the heart of geared MR actuators and conventional machining is a major hurdle to downsizing because it requires having close tolerance for machining and assembling a large number of small parts. This paper studies the potential of nested 3D printed MR clutches to improve the torque density of geared MR actuators at small scales. Nested 3D printed MR clutches are multi-disk MR clutches where the rotor and stator are fabricated simultaneously on a single 3D print. A prototype is designed, built, tested and compared to similar conventionally made MR clutches. The prototype weighs 84 g and can transmit a maximum torque of 0.88 N.m. The fabrication process is fast and simple, and the performance levels well surpass those of comparable machined MR clutches. The manufactured prototype doubles the torque density and multiply respectively by 4 and by 10 the torque-to-inertia and torque-to-viscosity ratios compared to equivalent machined MR clutches. Results show that nested 3D printing of MR clutches is an effective manufacturing process and opens the door to a new generation of high-performance mechanical transducer.

A 3D printed horn antenna at ka-band is presented in this paper. The horn antenna is well known for high gain performance. The performance of the horn antenna manufactured using 3D printed technology is investigated in this work. The horn is designed based on WR-28 waveguide standard. The proposed horn is simulated by computer simulation technology (CST) software and fabricated using 3D printing direct metal laser melting technique. The 3D printing technique gives the antenna an advantage of being not just rapid manufactured but also low-cost and lightweight. However, several works reported on 3D printed devices highlight the effects of surface roughness and dimensional tolerance on the performances. Therefore, the printed horn is profiled to correlate the surface roughness and dimension tolerance towards the performance. The printed horn is measured using standard VNA. The results showed that the measured performance agreed fairly with the simulation with directive radiation pattern at 15 dBi gain. The printed horn has a weight of less than 130g and considerably working at Ka band regardless of the surface roughness resulted from the fabrication process.

The increasing demand for novel fiber design has brought major challenges with the current fabrication methods. Additive manufacturing is an innovative fabrication process that has been attracting attention to the optical fiber community. 3D printed porous bodies from commercial silica powder were produced based on selective laser sintering (SLS). Complex structures such as antiresonant fiber (ARF), photonic crystal fiber (PCF) and multicore fiber (MCF) preforms were produced by this method. Additionally, a multi-material fiber with a silica cladding and a GeO2-SiO2 core was fabricated from a 3D printed preform. The optical and physical properties of the fabricated 3D printed structures were reported. This Dataset support paper delivered at the International Society for optics and Photonics.SPIE Photonic West 1-6 Feb. 2020. San Francisco.

3D printing is an emergent manufacturing technology recently being applied in the medical field for the development of custom bone prostheses and scaffolds. However, successful industry transformation to this new design and manufacturing approach requires technology integration, concurrent multi-disciplinary collaboration, and a robust quality management framework. This latter change enabler is the focus of this study. While a number of comprehensive quality frameworks have been developed in recent decades to ensure that the manufacturing of medical devices produces reliable products, they are centred on the traditional context of standardised manufacturing techniques. The advent of 3D printing technologies and the prospects for mass customisation provides significant market opportunities, but also presents a serious challenge to regulatory bodies tasked with managing and assuring product quality and safety. Before 3D printing bone prostheses and scaffolds can gain traction, industry stakeholders, such as regulators, clients, medical practitioners, insurers, lawyers, and manufacturers, would all require a high degree of confidence that customised manufacturing can achieve the same quality outcomes as standardised manufacturing. A Quality by Design (QbD) approach to custom 3D printed prostheses can help to ensure that products are designed and manufactured correctly from the beginning without errors. This paper reports on the adaptation of the QbD approach for the development process of 3D printed custom bone prosthesis and scaffolds. This was achieved through the identification of the Critical Quality Attributes of such products, and an extensive review of different design and fabrication methods for 3D printed bone prostheses. Research outcomes include the development of a comprehensive design and fabrication process flow diagram, and categorised risks associated with the design and fabrication processes of such products. An extensive systematic literature review and post-hoc evaluation survey with experts was completed to evaluate the likely effectiveness of the herein suggested QbD framework.

In this study, strontium substituted hydroxyapatite (Sr-HAP) was synthesized using collagen type I and citrate as bi-templates and the obtained nanoparticles with high similarity to natural bone minerals were made into composite scaffolds with interconnected porous structure using a three-dimensional (3D) printing technique. A calcium deficient structure of HAP phase was caused by doping Sr which was verified by Fourier transform infrared, x-ray diffractometer, scanning electron microscopy and transmission electron microscopy. The Sr/(Sr + Ca) molar ratio in Sr-HAP nanoparticles was 5.8% estimated by EDX. Furthermore, both 3D printed scaffolds made of Sr-HAP and HAP had uniform porous structure and porosity of about 60%. Cell culturing indicated that MC3T3-E1 cells could adhere on the surface of the scaffolds and the strontium substitution could enhance cell adhesion, proliferation and alkaline phosphatase activity. The printed composite scaffolds were used to repair critical-sized rabbit calvarial defects with a diameter of 15 mm. The results showed that the Sr-HAP scaffolds had better osteogenic capability and stimulated more new bone formation within 12 weeks. It was suggested that these printed Sr-HAP composite scaffolds possessed high potential as candidates in the application of bone augmentation and regeneration.

Compound fabrication: A multi-functional robotic platform for digital design and fabrication

Electromagnetic metamaterial absorbers (MMAs), with pivotal roles in applications such as stealth and communication, have revolutionised the field of absorbing materials by offering unique characteristics unattainable by natural materials through artificially designed unit cell structures. Although many MMAs have been successfully prepared through traditional micro/nano fabrication processes, inherent limitations persist. 3D printing, or additive manufacturing, offers unprecedented design freedom and streamlined production processes for MMAs. This review provides a comprehensive examination of 3D-printed MMAs. It first introduces the fundamental concepts and history of MMAs with a brief description of traditional techniques for MMA fabrication. Subsequently, it elucidates mechanisms governing the loss and absorption of electromagnetic MMAs and traditional absorbing materials, shedding light on the design principles. Next, this review centres on 3D printing modalities employed to fabricate MMAs by categorising the processes into one-step and two-step manufacturing that leverage the unique advantages of 3D printing. Moreover, it also delves into innovative 4D-printed MMAs, showcasing the potential of dynamically adjustable MMAs. In the end, potential future research directions are discussed by taking into consideration of current concerns. This review underscores the transformative impact of 3D-printed MMAs, paving a new avenue for future innovations in electromagnetic engineering.

In nature sensors possess complex interlocking 3D structures and extremely localized material properties that allow processing of incredibly complex information in a small space. Acoustic sensor design is limited by fabrication processes, often MEMS based, where there is limited scope for fully 3D creations due to planer fabrication methods. Here we investigate the application of 3D printing via digital light processing (DLP) to integrate piezoelectric, conductive and structural polymer layers to create a complete electro-mechanical device. We demonstrate a working piezoelectric acoustic sensor, capable of sending electric signals that can be picked up by pre-amp circuitry fabricated using a commercially available 3D printer. We show that the 3D printing of mechanically sensitive membranes with thicknesses down to 35 μm and tunable resonant frequencies is possible and further show it is possible to create a fully working electro-acoustic device by embedding 3D printed piezoelectric and conductive parts. Realizing this design opens up the possibility of generating truly 3D structured functional prints that may be used in bio-inspired design.

This study presents the design and fabrication results of an electrothermal micro-electro-mechanical system (MEMS) actuator. Unlike traditional one-directional U-shaped actuators, this bi-directional electrothermal (BET) micro-actuator can produce displacements in two directions as a single device. The BET micro-actuator was fabricated using two-photon polymerization (2PP) and digital light processing (DLP) methods, which are 3D printing techniques. These methods have been compared to see the success of BET micro-actuator fabrication. The compound of these methods and the essential coefficients through the 3D printing operation were applied. Evaluation experiments have demonstrated that in both methods, the 3D printer can print materials smaller than 95.7 μm size features. Though the same design was used for the 2PP and DLP methods, the supporting structures were not produced with the 2PP. The BET micro-actuator was manufactured by removing the supports from the original design in the 2PP. The number of supports, the diameter, and height on the arms of the micro-actuator is 18, 4 μm, and 6 μm, respectively. Although 4 μm diameter supports could be produced with the DLP, it was not possible to produce them with 3D printing device based on 2PP. Besides, the DLP was found to be better than the 2PP for the manufacturing of asymmetrical support structures. The fabrication process has been carried out successfully by two methods. When the fabrication success is compared, the surface quality and fabrication speed of the micro-actuator fabricated with DLP is better than the 2PP. Presented results show the efficiency of the 3D printing technology and the simplicity of fabrication of the micro-actuator via 2PP and DLP. An experimental study was carried out to characterize the relationship between displacement and input voltage for the micro-actuator. Experimental results show that the displacement range of the micro-actuator is 8 μm with DLP, while 6 μm with 2PP.

PurposeTwo-dimensional (2D) cell culture is a valuable method for cell-based research but can provide unpredictable, misleading data about in vivo responses. In this study, we created a three-dimensional (3D) cell culture environment to mimic tumor characteristics and cell-cell interactions to better characterize the tumor formation response to chemotherapy.Materials and methodsWe fabricated the 3D cell culture samples using a 3D cell bio printer and the bladder cancer cell line 5637. T24 cells were used for 2D cell culture. Then, rapamycin and Bacillus Calmette-Guérin (BCG) were used to examine their cancer inhibition effects using the two bladder cancer cell lines. Cell-cell interaction was measured by measuring e-cadherin and n-cadherin secreted via the epithelial-mesenchymal transition (EMT).ResultsWe constructed a 3D cell scaffold using gelatin methacryloyl (GelMA) and compared cell survival in 3D and 2D cell cultures. 3D cell cultures showed higher cancer cell proliferation rates than 2D cell cultures, and the 3D cell culture environment showed higher cell-to-cell interactions through the secretion of E-cadherin and N-cadherin. Assessment of the effects of drugs for bladder cancer such as rapamycin and BCG showed that the effect in the 2D cell culture environment was more exaggerated than that in the 3D cell culture environment.ConclusionsWe fabricated 3D scaffolds with bladder cancer cells using a 3D bio printer, and the 3D scaffolds were similar to bladder cancer tissue. This technique can be used to create a cancer cell-like environment for a drug screening platform.