An Evaluation of Wound Healing When Using 3D Printed Suture vs Commercial Suture in a Mouse Model

The capability to produce suture material using three-dimensional (3D) printing technology may have applications in remote health facilities where rapid restocking of supplies is not an option. This is a feasibility study evaluating the usability of 3D-printed sutures in the repair of a laceration wound when compared with standard suture material. The 3D-printed suture material was manufactured using a fused deposition modelling 3D printer and nylon 3D printing filament. Study participants were tasked with performing laceration repairs on the pigs' feet, first with 3-0 WeGo nylon suture material, followed by the 3D-printed nylon suture material. Twenty-six participants were enrolled in the study. Survey data demonstrated statistical significance with how well the 3D suture material performed with knot tying, 8.9 versus 7.5 (p = 0.0018). Statistical significance was observed in the 3D-printed suture's ultimate tensile strength when compared to the 3-0 Novafil suture (274.8 vs. 199.8 MPa, p = 0.0096). The 3D-printed suture also demonstrated statistical significance in ultimate extension when compared to commercial 3-0 WeGo nylon suture (49% vs. 37%, p = 0.0215). This study was successful in using 3D printing technology to manufacture suture material and provided insight into its usability when compared to standard suture material.

Chapter 18 - 3D printing technology in drug delivery

The widespread use of digital imaging can now be combined with additive three-dimensional (3D) printing, changing traditional clinical dentistry, especially in challenging cases. Visualizing the bone and soft tissue anatomy using computed tomography (CT) and intraoral scanning generated digital files that can be further processed for 3D printing. Among the popular 3D printing approaches, fused filament fabrication (FFF) and stereolithography (SLA) are broadly used due to their rapid production, precision, and ease of use. The current case series outlines three challenging clinical scenarios where a combination of CT and intraoral scans were utilized for digital planning. FFF multicolor anatomical models and SLA surgical guides were produced using 3D printing technology. The first case outlines the utility of this approach to place the optimal surgical window at the lateral sinus lift with anticipated difficult access. In the second case, distinct sites for autogenous bone harvesting were identified while preserving critical adjacent structures with surgical simulation. Finally, the third case outlines this strategy for optimal surgical access to expose an impacted second premolar. Both clinicians and patients benefited from the educational use of FFF‒SLA 3D-printed models, and all cases were successfully treated without complications. These cases demonstrate the significant utility of these digital technologies and rapid prototyping for improved pre-surgical planning, patient motivation, and didactic training that contribute to improved quality of clinical care. To the authors' knowledge, this is the first case reports employing both fused filament fabrication (FFF) and stereolithography (SLA) printing techniques in dental surgery. This innovative approach addresses a range of clinically challenging scenarios presented in this report. Computed tomography (CT) and intraoral scanning are essential for three-dimensional (3D) reconstruction. Specialized software is required to design the guide with precise specifications, and FFF and SLA printers are necessary for fabricating the 3D model. Three-dimensional reconstruction can be time-intensive, particularly when manual segmentation is necessary. Acquiring proficiency in the software may require additional time, and multicolor 3D printing also demands extended printing durations. This study explores how digital imaging and three-dimensional (3D) printing can improve complex dental surgeries. Using tools such as computed tomography scans and intraoral scans, dentists can create detailed 3D models of a patient's bone and soft tissues. Two popular 3D printing methods-fused-filament fabrication (FFF) and stereolithography (SLA)-were used to make these models, which help with surgical planning. The study includes three cases where 3D-printed models were used to prepare for difficult dental procedures. In the first case, the 3D model helped plan the best way to access a difficult area for sinus surgery. The second case used the model to identify the best sites for bone harvesting. The third case used the model to plan how to safely expose an impacted tooth. These helped both the dentist and the patient understand the procedure better. All surgeries were successful, demonstrating how FFF and SLA 3D printing enhance planning, making advanced dental surgeries safer and more efficient.

Personalized medicines are becoming more popular as they enable the use of patient's genomics and hence help in better drug design with fewer side effects. In fact, several doses can be combined into one dosage form which suits the patient's demography. 3 Dimensional (3D) printing technology for personalized medicine is a modern day treatment method based on genomics of patient. 3D printing technology uses digitally controlled devices for formulating API and excipients in a layer by layer pattern for developing a suitable personalized drug delivery system as per the need of patient. It includes various techniques like inkjet printing, fused deposition modelling which can further be classified into continuous inkjet system and drop on demand. In order to formulate such dosage forms, scientists have used various polymers to enhance their acceptance as well as therapeutic efficacy. Polymers like polyvinyl alcohol, poly (lactic acid) (PLA), poly (caprolactone) (PCL) etc can be used during manufacturing. Varying number of dosage forms can be produced using 3D printing technology including immediate release tablets, pulsatile release tablets, and transdermal dosage forms etc. The 3D printing technology can be explored successfully to develop personalized medicines which could play a vital role in the treatment of lifethreatening diseases. Particularly, for patients taking multiple medicines, 3D printing method could be explored to design a single dosage in which various drugs can be incorporated. Further 3D printing based personalized drug delivery system could also be investigated in chemotherapy of cancer patients with the added advantage of the reduction in adverse effects. In this article, we have reviewed 3D printing technology and its uses in personalized medicine. Further, we also discussed the different techniques and materials used in drug delivery based on 3D printing along with various applications of the technology.

Purpose – An increasing amount of attention is being paid to three-dimensional (3D) printing technology. The technology itself is based on diverse technologies such as laser beams and materials. Hence, 3D printing technology is a converging technology that produces 3D objects using a 3D printer. To become technologically competitive, many companies and nations are developing technologies for 3D printing. So to know its technological evolution is meaningful for developing 3D printing in the future. The paper aims to discuss these issues. Design/methodology/approach – To get technological competitiveness of 3D printing, the authors should know the most important and essential technology for 3D printing. An understanding of the technological evolution of 3D printing is needed to forecast its future technologies and build the R & D planning needed for 3D printing. In this paper, the authors propose a methodology to analyze the technological evolution of 3D printing. The authors analyze entire patent documents related to 3D printing to construct a technological evolution model. The authors use the statistical methods such as time series regression, association analysis based on graph theory, and principal component analysis for patent analysis of 3D printing technology. Findings – Using the proposed methodology, the authors show the technological analysis results of 3D printing and predict its future aspects. Though many and diverse technologies are developed and involved in 3D printing, the authors know only a few technologies take lead the technological evolution of 3D printing. In this paper, the authors find this evolution of technology management for 3D printing. Practical implications – If not all, most people would agree that 3D printing technology is one of the leading technologies to improve the quality of life. So, many companies have developed a number of technologies if they were related to 3D printing. But, most of them have not been considered practical. These were not effective research and development for 3D printing technology. In the study, the authors serve a methodology to select the specific technologies for practical used of 3D printing. Originality/value – Diverse predictions for 3D printing technology have been introduced in many academic and industrial fields. Most of them were made by subjective approaches depended on the knowledge and experience of the experts concerning 3D printing technology. So, they could be fluctuated according to the congregated expert groups, and be unstable for efficient R & D planning. To solve this problem, the authors study on more objective approach to predict the future state of 3D printing by analyzing the patent data of the developed results so far achieved. The contribution of this research is to take a new departure for understanding 3D printing technology using objective and quantitative methods.

Three-dimensional (3D) printing technologies are advanced manufacturing technologies based on computer-aided design digital models to create personalized 3D objects automatically. They have been widely used in the industry, design, engineering, and manufacturing fields for nearly 30 years. Three-dimensional printing has many advantages in process engineering, with applications in dentistry ranging from the field of prosthodontics, oral and maxillofacial surgery, and oral implantology to orthodontics, endodontics, and periodontology. This review provides a practical and scientific overview of 3D printing technologies. First, it introduces current 3D printing technologies, including powder bed fusion, photopolymerization molding, and fused deposition modeling. Additionally, it introduces various factors affecting 3D printing metrics, such as mechanical properties and accuracy. The final section presents a summary of the clinical applications of 3D printing in dentistry, including manufacturing working models and main applications in the fields of prosthodontics, oral and maxillofacial surgery, and oral implantology. The 3D printing technologies have the advantages of high material utilization and the ability to manufacture a single complex geometry; nevertheless, they have the disadvantages of high cost and time-consuming postprocessing. The development of new materials and technologies will be the future trend of 3D printing in dentistry, and there is no denying that 3D printing will have a bright future.

Objective To explore the feasibility and effect of 3D modeling and printing technology in constructing bone fracture models and assisting clinical teaching at the department of traumatic orthopedics. Methods CT scan images of bone fractures were reconstructed by Mimics software. The digital 3D bone fracture models were constructed and the interactive multimedia teaching videos were output. Moreover, all bone fracture models were printed by using fusion deposition modeling (FDM). At the end of the teaching course, a questionnaire survey was conducted to evaluate the teaching effect. Results The digital models of common bone fractures at the department of traumatic orthopedics were established, and the interactive multimedia teaching videos were output. A traumatic orthopedic teaching model with a 1∶1 scale was printed out. The questionnaire survey indicated that the application of 3D modeling and printing technology to build bone fracture model with PPT teaching can obviously improve students' understanding and mastery of relevant theoretical knowledge. They helped students better remember the type of bone fractures and how to choose the correct internal fixation methods. The teaching effect was satisfactory. Conclusions 3D modeling and printing technology was applied to build bone fracture models to assist clinical teaching at the department of traumatic orthopedics. It was found that the printed 3D bone fracture models can stimulate students' enthusiasm for learning and improve their learning effect. This method has good application value. Key words: Medical students; 3D printing technology; Teaching model; Traumatic orthopedics

Owing to COVID-19, the world has advanced faster in the era of the Fourth Industrial Revolution, along with the 3D printing technology that has achieved innovation in personalized manufacturing. Three-dimensional printing technology has been utilized across various fields such as environmental fields, medical systems, and military materials. Recently, the 3D food printer global market has shown a high annual growth rate and is a huge industry of approximately one billion dollars. Three-dimensional food printing technology can be applied to various food ranges based on the advantages of designing existing food to suit one’s taste and purpose. Currently, many countries worldwide produce various 3D food printers, developing special foods such as combat food, space food, restaurants, floating food, and elderly food. Many people are unaware of the utilization of the 3D food printing technology industry as it is in its early stages. There are various cases using 3D food printing technology in various parts of the world. Three-dimensional food printing technology is expected to become a new trend in the new normal era after COVID-19. Compared to other 3D printing industries, food 3D printing technology has a relatively small overall 3D printing utilization and industry size because of problems such as insufficient institutionalization and limitation of standardized food materials for 3D food printing. In this review, the current industrial status of 3D food printing technology was investigated with suggestions for the improvement of the food 3D printing market in the new normal era.

As the importance of visual aids increases, textbooks are including more figures and images to help with students' understanding. These visual aids enable students to learn concepts more effectively by hearing and seeing them simultaneously. However, for students who are visually impaired (that is, blind or have low vision), reading and understanding a textbook poses challenges. Teachers of students who are visually impaired have difficulty teaching with textbooks because they are compelled to explain and describe the complex figures and content verbally. Even after being explained, the image or concept might still remain nebulous for the student. Therefore, to help both students and their teachers, instructional materials should be prepared with easy, cheap, and customizable methods such as three-dimensional (3D) printing. Instead of seeing and hearing, students can use their sense of touch to recognize the 3D tactile aids, which might improve their learning and memory processes. Recently, 3D printing technology has emerged as an exciting technological tool for creating sophisticated and custom-made objects with relatively low-cost materials (Melchels, Feijen, & Grijpma, 2010; Peltola, Melchels, Grijpma, & Kellomaki, 2008; Pham & Gault, 1998). 3D printing is the process of fabricating 3D objects by building up materials layer by layer with a specific layer thickness in the range of 100 to 400 micrometers (^m). The most important advantage of 3D printing is its ability to build new objects in a customized way. Thus, 3D printing can be a powerful tool to make tactile patterns or objects related to textbooks. Stangl et al. tried to make 3D-printed picture books for visually impaired children (Stangl, Kim, & Yeh, 2014). They transcribed the images of the classic book Goodnight Moon, by Margaret Wise Brown, by printing features with different plastic layers. However, this study presented only plane-based shapes and not complete 3D objects. In this research, we investigate how 3D printing technology could be utilized for instructional materials that allow visually impaired students to have full access to high-quality instruction in history class. Researchers from the 3D Printing Group of the Korea Institute of Science and Technology (KIST) provided the Seoul National School for the Blind with tactile instructional materials and resizable braille made by 3D printers as shown in Figure 1. The teacher provided side-by-side hands-on instruction to guide students in understanding the characteristics of the shapes and their meanings. Students also used their hands to independently explore the 3D materials, allowing them to appropriately feel the historical pictures, maps, or relics. This procedure reinforced delivery of the lecture immensely since it clarified potential misunderstanding of text descriptions. The resulting implication was that the 3D instructional materials were beneficial and more suitable to help visually impaired students successfully comprehend content taught in the classroom. METHODS Three different types of 3D printing methods were utilized: (1) fused deposition modeling (FDM); (2) three-dimensional printing (3DP); and (3) digital light processing (DLP). The 3D printing process involves multiple stages, as shown in Figure 2. All 3D printing techniques are based on the use of computer-aided design (CAD) information that describes the geometry and size of the objects to be printed. The CAD data is converted to an STL (STereoLithography) file format which has extensive triangular coordination of 3D surface geometry (Chen, Ng, & Wang, 1999). Once the file is in a printable format, the 3D model is sliced into a series of digital crosssectional layers of specific thickness. Then the designed structure is built through a layerby-layer fabrication process with each layer thickness being 100 |m. When the printing is completed, the last step involves post-treatment operations to the object to improve its softness, durability, and safety. …

3D printing is not a new concept. The recent advances in printing speed, technology, and material selection are promoting its significant impacts in several industries, including health care. For our medical physics field, researchers are also finding its applications in various clinical aspects. However, the interests still remain in a few academic centers who have the luxuries of owning such an unconventional device in the radiation oncology department, or collaborating with a local 3D printing lab. As the 3D printing technology is becoming an unstoppable driving force in manufacturing revolution, are we also envisioning a future that 3D printing will become as common as a block-cutting machine in a radiation oncology department? In this debate, we invited two researchers who are experienced in studying the clinical use of 3D printing in medical physics field. Dr. Eric Ehler is arguing for the proposition that "3D printing technology will eventually eliminate the need of purchasing commercial phantoms for clinical medical physics QA procedures" and Dr. Daniel Craft is arguing against. Dr. Eric Ehler is an Assistant Professor in the Department of Radiation Oncology at the University of Minnesota. He is the medical physics residency program director at the University of Minnesota Medical Center. His education and research interests are 3D printing, pediatric radiotherapy, radiation dosimetry, and machine learning. Dr. Daniel Craft is currently a medical physics resident at The Mayo Clinic in Phoenix, AZ. Prior to the beginning of his residency, Dr. Craft was a graduate research assistant and PhD student at the University of Texas MD Anderson Cancer Center in Houston Texas, where he studied techniques to deliver postmastectomy radiation therapy using 3D printed patient-specific tissue compensators. He completed his Ph.D. in Medical Physics in May, 2018, and also holds an undergraduate degree in Physics from Brigham Young University. Phantoms provide medical physicists a means to assess the performance of medical devices in imaging, nuclear medicine, and radiation therapy.1 Historically, phantoms were designed and constructed by clinical staff and/or hospital engineers using materials and formulations available to them at the time.2 Currently, many vendors in the medical physics market provide a wide array of phantoms for clinical use. The reason for this shift could reasonably be attributed to convenience and in the interest of standardization of quality check (QC) procedures and quality assurance (QA) programs. 3D printing has been around since 1980s.3, 4 The expiration of patents related to 3D printing has lowered the cost of 3D printers. 3D printing technology has been described as the democratization of manufacturing; 3D printing is shifting the means of manufacture from a centralized system to a distributed network. The impact of increased access to manufacturing capability will reduce the convenience factor of commercial phantoms as clinicians can custom design and print phantoms as needed. The argument "3D printing technology will eventually eliminate the need of purchasing commercial phantoms for clinical medical physics QA procedures" is already becoming reality. In most clinics, the Linac morning QA is performed with a commercial image guidance radiotherapy (IGRT) phantom, which is a cubic phantom with marks on the faces for laser alignment and embedded features for x-ray imaging. An IGRT phantom with submillimeter accuracy was fabricated and reported by Woods et al.5 using computer-aided design freeware and a relatively low cost 3D printer (commercially available for $3150 USD). In our clinic, rather than purchasing multiple identical IGRT phantoms, our team designed our own phantom in a similar manner as Woods et al. The phantom was 3D printed with PET-G plastic for a cost of $10, using a 3D printer in a cost range of $900. The 3D printed phantom did not have the full capabilities of our commercial IGRT phantom but it fits our clinical needs as we did not fully use the features of the commercial phantom during morning QA. Additionally, when compared to a commercial small animal PET/CT imaging phantom, the 3D printed phantom was described as "functionally equivalent to commercially available phantoms".6 3D printed phantoms have also been described for MRI7 and PET/MRI6 systems. A feature of these phantoms is that they can be customized and produced by the end users at a low cost. 3D printed phantoms have been explored as patient specific phantoms for use in intensity modulated radiotherapy (IMRT) QA,8, 9 vascular imaging,10 and molecular imaging.11 For IMRT QA, 3D printing a patient specific phantom for every patient treated with IMRT is not currently clinically feasible, mostly due to time constraints. However, for commissioning new procedures or for a periodic QA schedule, using a 3D printed phantom is warranted. The use of patient specific phantoms allows for a true end-to-end test on a per-patient basis at reduced cost of commercial, nonpatient specific, anthropomorphic phantoms. Beyond phantoms, 3D printing has been investigated for radiation therapy immobilization devices,12 bolus,13-16 electron blocks,17 and other treatment aids. In fact, the strongest argument for clinical acquisition of 3D printing technology is for the fabrication of treatment devices due to the unique nature of patient anatomy and the high frequency of use of treatment devices. If clinics possess 3D printers for the purpose of treatment device fabrication, the convenience of 3D printing phantoms will increase greatly. A word of caution: 3D printing materials are not tightly controlled by all 3D printing material suppliers. For example, slight differences in formulation of 3D printing materials may affect the radiographic or other physical properties of the material. This variation could arise between one material supplier and another or even from batch to batch of the same supplier. Also, 3D printers can have defects in the printed object such as small unintended air voids or warping during printing. Air voids can occur from imperfect material deposition during the printing. Warping is an issue for fused deposition modeling (FDM) where a plastic filament is melted, extruded out of a nozzle, deposited, and then cools. Cooling can cause contraction, which may cause the FDM 3D printed object to warp. For charged particle radiation beams especially, this can negatively impact the performance of the 3D printed device or phantom.18 Therefore, QC of the manufacturing process will need to be performed by 3D printing staff or clinicians whereas for commercial phantoms, QC is performed by the vendor and verified by the clinicians. For example commercial water equivalent plastic blocks are usually supplied with a certificate stating the physical dimensional accuracy of the plastic, uniformity of the plastic, and the attenuation properties of the plastic. If the blocks are 3D printed by clinic staff, these tests will need to be performed in-house. In summary, I believe there is already a market advantage for the clinical use of 3D printed phantoms. As 3D printers gain use in routine clinical device fabrication, their utilization in other clinical areas, such as phantom fabrication, will expand. In the long term, as 3D printing capabilities increase and 3D printing materials are designed specifically for medical physics use, 3D printed phantoms will increasingly replace commercial phantoms for clinical QA procedures. 3D printing is a transformative technology that allows users to physically manufacture anything that they can model with a computer. Over the last several years there has been enthusiastic and rapid adoption of 3D printing technology in medical physics to create a wide spectrum of custom, patient-specific devices. 3D printers are well-suited to manufacture a number of devices that are currently much more expensive, or much more inconvenient to procure from commercial vendors. These include customized, patient-specific bolus and customized phantoms that may only be used once, or for a single patient. However, despite the interesting applications and enormous potential of 3D printing technology for some radiotherapy applications, presently, there are several limitations that will prevent it from being uniformly adopted as the preferred phantom fabrication technique in hospitals across the country. The first major limitation of 3D printing is the material properties of 3D printed parts. 3D printable materials must have some specific properties; they have to either be a thermoplastic with a glass transition temperature near 200°C, or a photopolymerizing resin. This effectively limits the number of potential materials to thermoplastics and things that can be mixed with them. If a material cannot be melted and turned into a filament, it generally cannot be 3D printed. There are some creative materials that mix in other substances — like wood shavings or copper powder — with thermoplastic bases to create materials with slightly different densities and HU values, but these material differences are mostly cosmetic and intended for hobbyist 3D printing. Importantly, there currently are no commercially available materials that can replicate either bone or lung tissues. Most current 3D printed phantoms either ignore bone entirely8, 19 or use custom in-house mixed materials to mimic bone that requires custom filament creating equipment.20 The first solution reduces the usefulness of the phantom, and the second solution dramatically reduces the convenience that 3D printing was supposed to provide in the first place. Similarly, the lungs are usually left open, or printed with "low infill" that matches lung density but is highly variable depending on the direction of an incident radiation beam.21, 22 Contrast this 3D printed phantom with a common commercial anthropomorphic phantom which comes with several different tissue types, including bone, cartilage, brain, soft tissue, and lung (Computerized Imaging Reference Systems, Inc. A Castleray company, Norfolk, VA). Additionally, these phantoms' low density material properties do not depend on the direction of incident radiation like low density 3D printed phantoms. Even if a full range of perfectly matched 3D printable materials were to be found, there are still large variations between identical 3D printed parts. We have previously shown that identically printed blocks of material can vary in density from each other up to 7%,23 and that is using the same printer, the same model, and the same roll of filament. There are currently dozens of different kinds of 3D printers in use in clinics around the country using many different materials and printer settings. If 3D printing QA devices becomes commonplace, it will be difficult to make meaningful comparisons of measurements across institutions that are using different 3D printers to produce phantoms based on their own specific materials and printing protocols. Another problem with wide adoption of 3D printing is increased cost and complexity. To be clear, the actual material costs to 3D print a simple phantom are almost certainly less than the cost to purchase a similar commercial phantom. The cost of 3D printers, however, can range anywhere from several hundred dollars to several hundred thousand dollars, with a commensurately huge range in printer complexity, print quality, available features, material compatibility, and reliability. For example, the cheapest 3D printers available on Amazon.com cost less than $200, but can only print using PLA filament, have minimum layer resolutions of approximately 200 microns, and have a build volume of only a few centimeters in any direction. On the other end of the spectrum, the HP Jet Fusion 3D 3200 uses multi-jet fusion technology to dynamically blend plastics to create parts up to 30 cm in each dimension with multiple colors and material properties, and has a minimum layer resolution of 70 microns. However, its cost starts at $155,000. It is important to remember that in-house phantom production will require in-house 3D printing expertise, so will it be the medical physicist's responsibility to be proficient in 3D design as well as the mechanical operation and maintenance of a 3D printer? Whose responsibility will it be if the 3D printer jams during a print and patient QA cannot be performed? 3D printers mostly operate in the background, but they do require operators to plan and start models printing, as well as change out materials and occasionally replace parts. Especially with less expensive printers the user must be able to troubleshoot and fix errors. This may be feasible in larger academic centers, but I do not think it is a reasonable expectation that the many small or nonacademic clinics that make up the majority of cancer care will embrace this unnecessary increased workload. In conclusion, 3D printing is currently not a mature enough technology to become the primary technique for fabricating important QA devices in radiotherapy clinics. Conventionally fabricated commercial phantoms are more uniform, reliable, and simple than 3D printed ones. It is definitely true that 3D printing has a place in radiation oncology — and an exciting one at that! The question that 3D printing must address is: what additional value does it provide over conventional phantom fabrication that outweighs the previously mentioned limitations. In my opinion, that value is in creating highly customized or unique phantoms for research and development in major academic centers, not in creating routine QA phantoms that every clinic needs. I am confident that 3D printing will eventually replace some commercial phantoms for clinical medical physics QA procedures at some clinics, but definitely not for all, or even most of them. I agree with Dr. Craft that currently there are many difficulties to overcome. However, in the long-term view I maintain the argument that all QA phantoms will be fabricated with 3D printing. It is true that currently available 3D printing materials are not equivalent to human tissues. Attributable to the complexity in designing a material that is compatible with 3D printing and is tissue or water equivalent, materials science developments are needed. In the meantime, there is an alternative to fully 3D printing a phantom if it is desired to be tissue or water equivalent. That is to use 3D printing to create a mold to fill with an equivalent material(s); this strategy can be used for phantoms9 as well as radiotherapy bolus.15 This can reduce 3D printing times and bypass deficiencies in the radiologic properties of current 3D printing materials such as those demonstrated by Dr. Craft.23 Regarding 3D printer QA and additional workload, monitoring printers for jams or other print failures can be performed with a software packages such as OctoPrint. The software can be used to monitor printing progress via webcam and, if necessary, the print job can be aborted remotely. Updates on the printing progress can even be sent to mobile devices. To lend perspective on the frequency of print failures, one of our printers (Lulzbot Taz 6) has over 200 print hours with only one failed part in that time while a previously used printer failed quite regularly; thus the choice in the 3D printer is important. In addition, it is true that QA will be required for 3D printed phantoms or devices. However as physicists, we are responsible for the materials and devices used clinically. Regardless of whether a phantom is fabricated in-house or purchased from an established vendor, validation of the phantom and implementation into clinical use is required. There may be additional considerations in the QA of 3D printed phantoms or devices, but the advantages offset the additional workload. Finally, I contest the statement that 3D printing may be feasible for large academic centers but not for smaller clinics. In fact, I believe that the greatest benefit will be to smaller clinics. At a large academic center, there are likely engineers within the hospital and engineering machine shops nearby to fabricate phantoms and devices. Smaller clinics likely lack these resources and 3D printing can fill that gap at a reasonable cost. There are several points upon which Dr. Ehler and I agree. First, and most importantly, we share a concern for some of the variable material properties that 3D printed objects can have. As he notes, different material suppliers are not held to strict material standards, which can lead to various imperfections and inconsistencies in 3D printed parts. Objects printed from different suppliers using an equivalently labeled material could have different densities and radiological properties.23, 24 This is, however, not the only potential source of uncertainty. I would add that the quality of a printed object will depend equally as largely on the 3D printer used, and the model that has been designed. There are many 3D printers with slightly different properties that could affect print quality, such as how stable it can maintain the nozzle and bed temperature, how fast the extruder moves, and many more. Additionally, unless 3D models of useful phantoms are shared across all institutions there will be additional variation between clinics in the actual characteristics of phantoms used for QA. This leads to the second point on which we have common ground: if phantoms are printed in house, calibration and standardization tests into dimensional accuracy, material uniformity, and material attenuation properties will also have to be performed in house. As Dr. Ehler notes, these certifications currently come with phantoms from commercial suppliers. While larger research institutions may have additional resources and time to make this in house testing feasible, having to perform these tests for every printed object is an unnecessary workload for most smaller clinics. This increased workload for physicists in designing objects to be printed, maintaining a 3D printer, and validating 3D printed objects is in my opinion a major limiting factor in the widespread adoption of clinical 3D printing. As Dr. Ehler has mentioned, another use for 3D printing aside from creating clinical phantoms is the creation of patient-specific treatment devices. This is a very interesting application of 3D printing, because many of these devices are currently difficult, time-consuming, or expensive to acquire through conventional fabrication. With 3D printing, however, patient specific bolus13, 15, 25 can be rapidly and inexpensively produced that reduces air gaps and improves dosimetric plan characteristics relative to less conformal bolus. In fact, I agree with Dr. Ehler that "the strongest argument for clinical acquisition of 3D printing technology is for the fabrication of treatment devices." I disagree, however, with his assertion that this technology can be applied equally to creating phantoms for every clinical need. Although 3D printed bolus is in many ways more convenient than and superior to conventional bolus, 3D printed phantoms are generally harder to manufacture and have inferior material properties relative to conventional phantoms. Ultimately, the debate around 3D printing taking over conventional commercial phantoms is an argument of magnitude. It is clear that 3D printing is currently being used in clinics around the country for a variety of interesting purposes including phantom development,9, 11 treatment device fabrication,13, 16 and more.7, 26, 27 As the technology matures and continues to develop I am sure that it will improve and more use cases will be found. However, it is my opinion that 3D printing will remain a supplemental technology to fabricate a few special things, and will not ever completely replace conventionally fabricated commercial phantoms.

Recent advances in 3D printing technologies for wearable (bio)sensors

The field of three-dimensional (3D) printing has witnessed significant advancements in recent years, and its potential for revolutionizing medical applications is rapidly emerging. This review aims to provide an overview of the current state and scope of 3D printing in the medical field. The review begins by highlighting the various 3D printing technologies currently employed in healthcare settings, including stereolithography, selective laser sintering, fused deposition modeling, and inkjet printing. Each technology's advantages and limitations are discussed, shedding light on their suitability for different medical applications. Next, the review delves into the diverse range of medical applications where 3D printing has shown promise. These applications include the fabrication of patient-specific anatomical models for preoperative planning, surgical guides and tools, customized implants and prosthetics, tissue engineering scaffolds, and drug delivery systems. The potential benefits of using 3D printing in these areas, such as enhanced surgical accuracy, improved patient outcomes, reduced surgery time, and personalized medicine, are explored. Furthermore, the review addresses the challenges and limitations associated with implementing 3D printing in medical settings. These challenges include regulatory concerns, standardization of processes, material biocompatibility, cost-effectiveness, and scalability. The ongoing efforts to overcome these barriers and the future directions of 3D printing in medicine are also discussed. In conclusion, 3D printing holds immense potential for transforming various aspects of medical practice. While considerable progress has been made, there are still challenges to be addressed before widespread adoption can be achieved. With continued research and development, coupled with regulatory support and collaboration between academia, industry, and healthcare professionals, 3D printing is poised to International Journal of Scientific Research in Engineering and Management (IJSREM) Volume: 07 Issue: 07 | July - 2023 SJIF Rating: 8.176 ISSN: 2582-3930 © 2023, IJSREM | www.ijsrem.com DOI: 10.55041/IJSREM24845 | Page 2 make a substantial impact in the field of medicine, improving patient care and treatment outcomes. Key words: Additive manufacturing (AM); Bio-medical; Fused Deposition Modelling (FDM); Selective Laser Sintering (SLS); Stereolithography (SLA); Digital Light Processing (DLP); Binder Jetting; Material Jetting; Direct Energy Deposition (DED).

Recent developments in three-dimensional (3D) printing technology offer immense potential in fabricating scaffolds and implants for various biomedical applications, especially for bone repair and regeneration. As the availability of autologous bone sources and commercial products is limited and surgical methods do not help in complete regeneration, it is necessary to develop alternative approaches for repairing large segmental bone defects. The 3D printing technology can effectively integrate different types of living cells within a 3D construct made up of conventional micro- or nanoscale biomaterials to create an artificial bone graft capable of regenerating the damaged tissues. This article reviews the developments and applications of 3D printing in bone tissue engineering and highlights the numerous conventional biomaterials and nanomaterials that have been used in the production of 3D-printed scaffolds. A comprehensive overview of the 3D printing methods such as stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), and ink-jet 3D printing, and their technical and clinical applications in bone repair and regeneration has been provided. The review is expected to be useful for readers to gain an insight into the state-of-the-art of 3D printing of bone substitutes and their translational perspectives.

ABSTRACT: Stereolithography (SLA) 3D printing technology is increasingly applied in geomechanics, petroleum engineering, geothermal, and CO2 storage research, particularly in fracture flow and mechanics. To understand the mechanical characteristics of 3D printed materials, we conducted laboratory experiments examining the effect of printing orientation on the properties of three specimens. These specimens were printed using a FormLabs (3B+) 3D printer at layering angles of 0°, 45°, and 90°, with a resolution of 100μm, and sized 1-inch in diameter and 2-inches in length. We performed triaxial compressive tests, ultrasonic elastic wave velocity measurements, and unconfined compressive strength (UCS) tests using an Autolab 1500 test frame. Incremental confining pressures from 1 MPa to 20 MPa were applied to explore static and dynamic mechanical properties. The UCS tests showed that all samples exhibited ductile behavior with similar stiffness and yield strength across different layering angles, demonstrating a stiffness of approximately 4 GPa and compressional wave velocities between 2555-2580 m/s at zero confining pressure. The findings confirm the mechanical and acoustic consistency of the samples, supporting their suitability for advanced geomechanical applications. 1. INTRODUCTION Three-dimensional (3D) printing technology, also known as advanced manufacturing (AM), is a rapidly developing field that has revolutionized manufacturing processes across various industries including aerospace (Richter & Lipson, 2011), automotive (Rahim & Maidin, 2014), healthcare (Logan & Duddy, 1998), petroleum engineering (Li et al., 2021), and geomechanics (Phillips et al., 2021). This technology uses computer-aided design (CAD) to create three-dimensional objects by adding material layer by layer using almost any type of material such as polymers, and ceramics. Thermoplastic urethane and metals can also be employed as raw material (Gopinathan & Noh, 2018). There are several techniques involved in 3D printing, including Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLS), Digital Light Processing (DLP), Binder Jetting, and Material Jetting. Each technique has its advantages and disadvantages (Jandyal et al., 2022), and the choice of technique depends on the type of object being printed, the desired resolution, and the available materials. With the increasing popularity and availability of 3D printing technology, it is now relatively easy to create custom objects, prototypes, and even entire structures using 3D printing. Among the available techniques, SLA is known for producing high-resolution objects with smooth surfaces. SLA was first developed in the early 1980s by Kodama, 1981 and called Rapid Prototyping (RP).

Graphene is an important nanocarbon nanofiller for polymeric matrices. The polymer–graphene nanocomposites, obtained through facile fabrication methods, possess significant electrical–thermal–mechanical and physical properties for technical purposes. To overcome challenges of polymer–graphene nanocomposite processing and high performance, advanced fabrication strategies have been applied to design the next-generation materials–devices. This revolutionary review basically offers a fundamental sketch of graphene, polymer–graphene nanocomposite and three-dimensional (3D) and four-dimensional (4D) printing techniques. The main focus of the article is to portray the impact of 3D and 4D printing techniques in the field of polymer–graphene nanocomposites. Polymeric matrices, such as polyamide, polycaprolactone, polyethylene, poly(lactic acid), etc. with graphene, have been processed using 3D or 4D printing technologies. The 3D and 4D printing employ various cutting-edge processes and offer engineering opportunities to meet the manufacturing demands of the nanomaterials. The 3D printing methods used for graphene nanocomposites include direct ink writing, selective laser sintering, stereolithography, fused deposition modeling and other approaches. Thermally stable poly(lactic acid)–graphene oxide nanocomposites have been processed using a direct ink printing technique. The 3D-printed poly(methyl methacrylate)–graphene have been printed using stereolithography and additive manufacturing techniques. The printed poly(methyl methacrylate)–graphene nanocomposites revealed enhanced morphological, mechanical and biological properties. The polyethylene–graphene nanocomposites processed by fused diffusion modeling have superior thermal conductivity, strength, modulus and radiation- shielding features. The poly(lactic acid)–graphene nanocomposites have been processed using a number of 3D printing approaches, including fused deposition modeling, stereolithography, etc., resulting in unique honeycomb morphology, high surface temperature, surface resistivity, glass transition temperature and linear thermal coefficient. The 4D printing has been applied on acrylonitrile-butadiene-styrene, poly(lactic acid) and thermosetting matrices with graphene nanofiller. Stereolithography-based 4D-printed polymer–graphene nanomaterials have revealed complex shape-changing nanostructures having high resolution. These materials have high temperature stability and high performance for technical applications. Consequently, the 3D- or 4D-printed polymer–graphene nanocomposites revealed technical applications in high temperature relevance, photovoltaics, sensing, energy storage and other technical fields. In short, this paper has reviewed the background of 3D and 4D printing, graphene-based nanocomposite fabrication using 3D–4D printing, development in printing technologies and applications of 3D–4D printing.