(3D) Printers in Libraries - ACS Publications - American Chemical

May 18, 2017 - ABSTRACT: As an emerging technology, three-dimensional (3D) printing has gained much attention as a rapid prototyping and small- scale ...
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Three-Dimensional (3D) Printers in Libraries: Perspective and Preliminary Safety Analysis Neelam Bharti*,† and Shailendra Singh‡ †

Marston Science Library, George A. Smathers Libraries, University of Florida, Gainesville, Florida 32611, United States Division of Environmental Health and Safety, University of Delaware, Newark, Delaware 19716, United States

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ABSTRACT: As an emerging technology, three-dimensional (3D) printing has gained much attention as a rapid prototyping and smallscale manufacturing technology around the world. In the changing scenario of library inclusion, Makerspaces are becoming a part of most public and academic libraries, and 3D printing is one of the technologies included in Makerspaces. Owing to the ease of availability and cost effectiveness, most libraries use fused-deposition-modeling-based 3D printers compatible with plastic printing materials, such as polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). During the printing, PLA and ABS emit ultrafine particles (UFPs) and volatile organic compounds (VOCs) that may deteriorate the indoor air quality. In this article, first, we have discussed the background of 3D printing, the most common technologies used for 3D printing and printing materials, its applications in chemical education and sciences, as well as 3D printing health and safety concerns. Second, we measured and analyzed the number of UFPs (0.02−1.0 μm) in the 3D printing lab in a library and found that the number of particles/cubic centimeter significantly increased during the printing procedure (36−60 times) and does not return to baseline even 24 h after shutting down the printers. We also provide some recommendations that should be considered when hosting a 3D printing lab in libraries. KEYWORDS: Interdisciplinary/Multidisciplinary, Safety/Hazards, Laboratory Equipment/Apparatus, Toxicology, Undergraduate Research, Graduate Education/Research

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UFPs released from desktop printers during the operation. We were not able to measure the number of nanoparticles and volatile organic compounds (VOCs) due to the limitations of our instrument. These results will provide some guidance to safety measures needed as well as shed light on the potential health concerns for the library 3D printer users.

hree-dimensional (3D) printing is a process for the fabrication of 3D objects from data in a digital file. 3D printing has been around since the early 1980s and recently gained much popularity in industry and academia.1 It has transformed every field of learning and has been called “the third industrial revolution”.2 In this process, the virtual design of an object is assimilated as a digital file using the computeraided design (CAD) software. This software slices the digital file of the object into hundreds or thousands of layers. The printer follows the sliced model and prints the object by adding successive layers of printing material on top of others until the model is completed. As 3D applications and uses increase in popularity among all facets of science, engineering, biomedical education, and research, more and more libraries are adding 3D printing capabilities. According to a 2015 American Library Association (ALA) report, over 425 public library branches have made 3D printing facilities available.3 Here, we present all the aspects of 3D printing including the background, printing methods/materials, technologies, academic applications, and health and safety concerns. This study was also designed to measure the emission of ultrafine particles (UFPs) inside the 3D printing room in Marston Science Library at the University of Florida and determine the indoor air quality. This preliminary study measured the emission of © XXXX American Chemical Society and Division of Chemical Education, Inc.

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HISTORY AND BACKGROUND 3D printing was initially developed by Charles Hull as the Rapid Prototyping or Solid Freeform (SFF) Technology in the early 1980s and has been around for more than three decades.4 The modern 3D technique was established in 1986 by converting a model design into a .stl (STereoLithography or Standard Tessellation Language) file format using CAD software. The .stl files were used to print a 3D object using the printer, leading to the start of “3D Systems”, a 3D technology company.5 The first 3D printer was named “Stereolithography Apparatus (SLA)”. Later on, the first commercial 3D printer, SLA 250, was made available to the public in 1988. In 1990, Scott Crump invented Fused Deposition Modeling (FDM) technology and founded another Received: October 5, 2016 Revised: April 18, 2017

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3D company, Stratasys.6 Apart from the commercial efforts, MIT professor Michael Cima in 1993 named a printer “3D printer” that could use plastic, metal, or ceramics to print a 3D object. In recent years, tremendous progress has been made in 3D printing revolution, and different printers are available with material options.7,8 Low-cost desktop versions have made 3D printing technology widely available for day-to-day work in both home and office settings.

3D Printing Applications in Chemistry and Related Sciences

3D printing provides a new creative and innovative platform for almost every discipline in education and research. Particularly, engineering disciplines use 3D printing to make models of new machines, robots, and other prototypes by various software.10,11 It has also been used in automotive and aerospace engineering to prepare prototypes of cars and airplanes and in architecture for printing structural models.11 In biomedical and health sciences, 3D printing is used for bone grafting, dental implants, and building prosthetics. For bone grafting and dental implants, scientists use different compositions of calcium mineral as the printing material, which is comparable to the mineral component of the bone.12,13 Bioprinting is another recent development in 3D printing; biotissues are used as 3D printing materials for the modeling of living tissues for studies. Roche Pharmaceuticals tested 3D printed liver cells for drug toxicity.14 The 3D printing of heart tissues and invention of bionic ears are recent innovations in the medical field.15−17 3D printing has a substantial impact on the field of chemical education (Figure 2).18−27 3D printed interactive models of the Bohr model of the atom, bond polarity, and hybridization are great learning tools for students to explore the atomic theory.18,19 3D models also have been used to teach orbital theory as well as VSEPR theory in the classroom and laboratory.20,21 Rossi and co-workers developed a simple protocol to convert chemical models into real life objects, and 3D printed molecular models are effectively used in studying the 3D structure of a chemical molecule.22−24 Use of 3D printed models in teaching symmetry and point group theory proved to be very helpful to understand these chemical concepts.25,26

3D Printer Technologies and Printing Material

Various types of 3D printing technologies are available.8,9 Three major types are (1) FDM or Fused Filament Fabrication (FFF), (2) Stereolithography (STL), and (3) Selective Laser Sintering (SLS) (Figure 1).

Figure 1. Major technologies and common printing materials available for 3D printing.

The printing material depends upon the printer technology and model to be printed. Currently, many materials such as metals, ceramics, paper, biomaterials, food materials, and others are used for 3D printing, whereas plastic is the most common and widely used material. Plastic has different forms such as nylon or polyamide powder, filament, and resin. The most commonly used printers in libraries use plastics, acrylonitrile butadiene styrene (ABS), and polylactic acid (PLA), as the printing material. The main differences between ABS and PLA are shown in Table 1.

3D Printing in the Libraries and the Safety Concern

Libraries have been a place for idea generation and knowledge sharing for centuries. In the recent technological revolutions, libraries have embraced the change and shifting need for technology involvement in supporting knowledge production. This shifting paradigm inspired libraries to become involved with Makerspace or collaborative learning centers. One of the

Table 1. Comparison of ABS and PLA

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(b) Risk assessment of 3D printing services in libraries: Review of potential chemical and environmental hazards; emission of UFPs, nanoparticles, and aerosol. (c) Study of the safety data sheets (SDSs) of the materials used and review of the toxicological study-related literature information. Emission of UFPs

During 3D printing, the thermoplastic melts and extrudes through the nozzle at a high temperature. During this process, plastic nanoparticles and UFPs are generated as the byproduct.28,29 Nanoparticles are UFPs of size in nanometers (10−9 m). Nanoparticles emitted from 3D printers are a big concern because of their small size and larger surface area that can potentially interact with the human body.30−33 A team of scientists from the Illinois Institute of Technology and National Institute of Applied Sciences, France, reported that commonly available 3D printers emit a large amount of UFPs in the air. When inhaled, these UFPs can end up in the lungs and brain and may cause inflammation in the respiratory system and lungs with a possibility to reach the bloodstream.32 Once these particles interact with the blood cells, they may be deposited in different organs such as the bone marrow, lymph nodes, spleen, or heart and may lead to central nervous system disorders.34 Several other studies showed that elevated UFP concentrations are linked to adverse health effects including cardiorespiratory mortality, hospital admissions for stroke, and asthma symptoms.32,33 Different printing materials are used for 3D printing, supporting printer design and requirements. Until now, it was assumed that PLA is safer than ABS, but recently a study by Patrick Steinle showed that PLA emits a higher number of ultrafine aerosol particles than ABS (2.1 × 109 vs 2.4 × 108) while printing an object in an office setting. After occasional use of the printer for seven months, the ultrafine aerosol emission was 2 times higher from PLA and 4 times higher from ABS. The produced aerosol mainly consisted of volatile droplets of size 100−300 nm in diameter.35,34 Although there is no confirmed evidence, a higher emission of ultrafine aerosol particles after the long use of a printer indicates the age factor of the printer. More studies are needed to correlate the higher emission of ultrafine aerosol particles with the printer run time. Printing with PLA using a 3D printer released 20 billion particles per minute (p/min), whereas printing with ABS released 200 billion p/min. The 10-fold increase in the number of particles was attributed to the high melting temperature of ABS and requirement of a heated bed. ABS produces a distinctive smell when heated, causing headaches and respiratory and eye irritation in sensitive people. Some studies showed that ABS fumes are toxic to rats and mice: “There is a good chance that ABS-fed 3D printers may be more harmful than PLA-fed printers due to both higher emissions and likely higher toxicity.”29,35,34

Figure 2. 3D printed models in chemical education. (A) The Bohr model of the atom, bond polarity, and hybridization. Reproduced with permission from ref 18. Copyright 2016 American Chemical Society. (B) A 3D printed model of the chemical structure of L-proline. Reprinted with permission from ref 22. Copyright 2015 American Chemical Society. (C) A 3D printed model of molecular orbitals of ethane and 1,3-butadiene. Reprinted with permission from ref 20. Copyright 2015 American Chemical Society.

common technologies widely accepted in these places is 3D printing. This is a great way to engage users in the libraries and help the community with creating knowledge and learning emerging technologies. Because of space and budget concerns, a majority of the libraries select the FFF or FDM technology. The advantages of FFF 3D printers are their cost and the availability of a range of printers. FFF printers cost approximately $500 and are available in single or dual extruder options. The easy availability and cost of different color filaments also make FFF an attractive option for libraries from a sustainability perspective. The availability of a 3D printer in libraries is exciting but raises some safety concerns at the same time. Normally, libraries are not equipped with exhaust ventilation or fume hoods. Having a machine generating UFPs in the library setting can be harmful to the health of library staff and users depending upon the extent of service and number of printers in service at a given time. A number of studies have shown that 3D printers produce volatile organic compounds (VOCs) and ultrafine particles (UFPs) by thermal decomposition when a 3D printer heats and melts a plastic filament.28,29 VOCs are classified as toxic air pollutants by the Environmental Protection Administration (EPA), and exposure to certain VOCs (e.g., methylene chloride) can lead to cancer. On the other hand, UFPs can pass through the lungs and travel to other organs, and therefore, UFPs have been linked to asthma and cardiovascular issues. Before a comprehensive health and safety guideline is developed for any 3D printer service, it would be wise to conduct a complete study from the environmental health and safety (EH&S) perspective by considering the following points: (a) Occupational hazards associated with the 3D printing process and materials used (burn, fire, moving parts, electric voltage, tools, scraper, spatula, blade, and printed object).

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MATERIALS AND METHODS

3D Printers and Filaments

Commercially available desktop printers, available from two manufacturers, were used during this study (two MakerBot Replicator 2 and three Fusion 3). A maximum of five printers were operated at a time during the study in the 3D printing room at Marston Science Library (Figure 3). All the printers were compatible with ABS and PLA, but the studies were C

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Figure 3. 3D printing room.

conducted using PLA only. ABS was not used as the printing material for the study because of its intense smell. The printers were typical desktop printers and placed in a room (∼225 sq ft) in the library; the printers were not enclosed. Default settings were used as provided by the manufacturer, and the nozzle temperature was maintained at 210−215 °C.

Figure 4. Average number of UFPs with standard deviation (SD) at different locations in the library. (Four printers were in operation.)

measured for an extended time (for 10 min) at each location, and the data were recorded as the average per minute for a 10point study (Figure 4 and Table 2). During the second study,

Emission Test

Table 2. Number of UFP Emissions (pt/cc) During the Multipoint Study

The emission test was conducted in the 3D printing room (Figure 3). The UFP emission was measured using a TSI PTrak model 8525 as particles per cubic centimeter of air (pt/cc) in the particle size range 0.02−1 μm. The instrument only measured the amount of UFPs, not the nanoparticles smaller than 20 nm, and aerosol or VOCs. The temperature inside the room varied within the range 72−73 °F with a relative humidity 44−47%. The particle counter was charged with isopropyl alcohol according to the manufacturer’s guidelines prior to the sampling. The measurements were a direct reading from the instrument, and cumulative sampling was performed. Control (blank) measurements were carried out at different locations in the library such as the service desk, adjacent study room of the same size (room Xenon), and a faculty office. All the tests were performed within 2 weeks. The UFP emission was tested with different numbers of printers running at a given time. In each measurement, the particle counter was run for at least 10 min, and the data were recorded as an average of every 1 min. The UFP measurement study was performed in a glass study room ventilated by the building HVAC system. When the 3D room door was opened during the study, the number of UFPs decreased, but almost did not affect the final average. The printers were placed on a wooden table, and the measurements were carried out 12−24 in. away from the printers.

3D Room Average Max Min SD

52,760 54,530 50,348 465.93

Office 209b 894 1021 840 18.38

Service Desk 822 853 778 7.75

Room Xenon 1356 1449 1286 18.06

four printers were in operation to analyze if the number of UFPs increases because of the extra printer. The number of UFPs in the 3D printing room was almost 60 times higher than that in the control location and 38 times higher than that in the room Xenon. Although the number of particles was different during both the studies, the trend was similar. The analysis clearly indicates that the number of UFPs in the 3D printing room was much higher when four printers were operational compared to when only three printers were working. In both the experiments, the number of UFPs was higher in the room Xenon than those in the control locations as well; the high number of UFPs in the room Xenon can be attributed to its proximity to the 3D printing room. The average was also obtained during the multipoint study (Table 2). During the 10 min study, the number of UFPs varied from 50,348 to 54,530, with an average of 52,760 pt/cc. During a 20-point study, when all five printers were in operation, the trend of UFPs was measured (Figure 5). The graph represents the average number of the UFPs at different time points. During the study, the number of UFPs ranged from min 56,200 to max 98,200 with an average of 86,995 pt/ cc. We saw some ups and downs in the UFP emission data due to some error resources, but all are within the range. The most common error could be from the fluctuation in temperature or humidity, number of times the door of the lab opened and closed, or filaments used from different commercial sources. Even the color of the filament could affect the number of UFPs. We also analyze the number of printers in operation and its effect on UPF emission. The analysis clearly indicates that the average number of UFPs in the 3D printing room was much higher when five printers were operational compared to when only three or four printers were working (Figure 6).

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RESULTS AND DISCUSSION The preliminary data were collected at different locations throughout the library during the study. The service desk and faculty office were used as the control for the baseline. 3D printing and the adjacent room (room Xenon) were selected for collecting data. The data statistics grouped by location are summarized in Figures 4−6. The temperature and humidity throughout the library and control locations were consistent during the sampling and within the normal range of indoor environments. The UFP emission studies were conducted in two sets. During the first set, three printers were running and the UFP emission data were collected as a one-point study, where the number of particles was measured for 1 min at each location and the average was recorded. During the one-point study, the number of UFPs was observed to be much higher, almost 26− 36 times those of the control locations and 17 times that of the room Xenon. In the second study, the UFP emission was D

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consider whether it should set a standard for ultrafine particles, for the first time. Some 3D printing laboratories have detailed standard operating procedures (SOPs) for the 3D printing facility, e.g., the Harvard fabrication lab; it should be a standard practice for every lab or library or classroom supporting 3D printing. Because of its low emission and low toxicity, PLA seems to be the material of choice for most FFF printers in libraries, but the fumes of color or dye used in the color filament might have their own hazardous elements.29 Besides the printing material hazards, other potential risks are also involved (Figure 7). The use of ABS requires a hot plate (160−180 °C), which has the potential to cause a severe burn. Therefore, PLA is a safer choice in this scenario. Like any other electrical gadget with a heating component, there is some risk of fire. A case was reported where the 3D printer caught fire.36 Just to be safe, keep the flammable materials as well as papers away from the 3D printer.

Figure 5. Trend of UFPs in the 3D room over 20 min (five printers were in operation), average number of particles with SD.

Figure 6. Effect of number of printers in operation on UFPs emission.

Figure 7. Hazard and warning signs associated with 3D printers.

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EH&S PERSPECTIVE AND RISK ASSESSMENT The 3D printer manufacturer manuals and supporting materials generally do not provide any clear information on health and safety guidelines for the user or operators on the methods or materials used, or what the acceptable limit of exposure is, and for how long. The 3D printing services in libraries are a concern because of the close environment and number of people in the surrounding area. Dr. Stephen published one the first few reviews about the safety and health concerns of 3D printing and outlined some guidelines for a 3D printing laboratory.28 Because of the hightemperature requirement and use of potentially flammable and hazardous chemical materials in everyday printing, 3D printing should be carried out in a regulated/controlled environment and should follow the standard OSHA lab regulations. Every individual working in a laboratory or confined space is obligated to comply with the OSHA lab standards, including the information on the workplace chemical and occupational hazards and allowable exposure limit. Most open desktop 3D printers do not have exhaust ventilation accessories; therefore, the selection of the printing material is very critical. It is recommended that the printer should only be used in a well-ventilated area, and a standard chemistry lab-grade fume hood should be used when printing with ABS. A fume hood or exhaust ventilation should be made mandatory when using a desktop printer in an office, library, or classroom-like setting. The EPA has a standard for particulate matter (PM) as a part of the Clean Air Act but does not have a clear standard for “ultrafine particles”. One of the recent comments by EPA officials suggests that the agency will

Recommendations

Because of the continuous increase in 3D printer use by faculty, staff, and students in academic institutions, proper policies should be established for the safe use of 3D printing. As discussed above and as various research studies indicate, 3D printers are capable of generating potentially harmful UFPs and chemical vapors during printing and subsequent processing. Owing to a large amount of UFPs and aerosol, desktop 3D printers should not be operated for a long time in a small room without proper ventilation. The following recommendations should be followed when using 3D printers in libraries or in any other areas: 1. A proper hazard risk assessment should be performed before buying any new printer. EH&S should also be involved in the plans and purchases of different types of printers and materials, locations of the printers for a proper hazard risk assessment, and evaluation of a proper exhaust ventilation. 2. The manufacturer guidelines should be followed while operating any 3D printer, and only the recommended materials should be used for printing. SOPs should be established and used for the operation of 3D printers. Safety data sheets (SDSs) should be available and readily accessible for all the printing materials and for any other chemical products used in the printing process. The most useful sections of the SDS are section 7, handling and storage, and section 8, exposure control/personal protection. E

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3. All the users should be trained for the proper and safe operation of 3D printers, including general workplace safety (laboratory safety and hazardous waste) and hazard information relevant to the material and other chemical products used in printing. 3D users should also be made aware of the occupational and health hazards associated with the printers and printing procedures. 4. Because of the presence of a large amount of UFPs and aerosols, desktop 3D printers should not be operated for a long time (over 2−3 h) in a small room without proper ventilation. Proper air ventilation systems should be used in the 3D printing room, and the air volumes should be replaced at least four times per hour. Use 3D printers either with a built-in enclosure or in well-ventilated areas. 5. Food and drinks should not be allowed in the 3D printing area and in the area where the model and support materials are stored. Once a printing job has been started, users should not disturb, move, or touch the moving parts of the printer. 6. The number of 3D printers in one location should be limited by the size of the space (one printer per standard office with ventilation). More than one printer should not be used for a standard office area. Whenever possible, printers using ABS media should be used within a fume hood. 7. For special materials such as thermoplastics, photopolymers, nylon, high-impact polystyrene, powders, metals, and biological agents, specific precautions should be taken on the basis of the hazards associated with the printing process. 8. Proper personal protective equipment (PPE) found in SDS should be used to handle the hazardous materials, hot surfaces, or specific printer material. Eye protection is required during any activity where airborne projectiles may be present or the material can splash. 9. For specific print processes using an alkaline bath to dissolve support materials, an emergency eyewash station is required in the immediate vicinity of the work. To avoid the destruction of skin or tissue upon exposure, alkaline materials should be rinsed immediately if splashed on the body or eyes. 10. To handle an alkaline bath, proper lab attire, a laboratory coat, corrosive resistant rubber gloves, and splash goggles should be used. A rubber apron and face shield offer additional protection when working with large amounts of corrosive materials. 11. A proper spill kit (chemical adsorbent pads and powder, plastic scoop, polyethylene bags for waste collection, chemical resistant gloves, splash googles, chemical waste labels, and chemical spill cleanup procedures) capable of neutralizing the caustic components of the alkaline bath should be available in the close vicinity and ready for use (Figure 8). 12. When the alkaline bath is emptied, it must be disposed of as hazardous waste and cannot be poured down the drain because some of the components of the dissolved material are harmful to aquatic life.

Figure 8. Spill kit to work with an alkaline bath.

classrooms and libraries has raised concern because of a large number of hazards associated with the process, including UFP emission during the printing process. Because of easy access, most libraries use FFF technology-based printers that use plastic materials to print 3D models, and the amount of UFP emission depends on the type of printer and printing material. Although both PLA and ABS have their pros and cons, from a safety perspective, after a study of their SDS and consideration of other hazards, PLA is a better choice than ABS. We studied and analyzed the emission of UFPs in our library 3D printing lab and other locations in the library; preliminary studies indicated that the number of UFPs was 36−60 times higher than those in the control locations. This certainly affects the indoor air quality. We provided a recommendation from an EH&S perspective; the recommendations should be followed for hosting a 3D printing lab in libraries. UFPs generated during the printing process cannot be controlled, but the safety concerns can be reduced by operating the printer in a wellventilated room or fume hood or using ventilated enclosure, following the EH&S recommendations, and educating the operating staff and users.

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UPDATE After our initial study, our original setup was dismantled, the room was thoroughly cleaned on the ground and the walls, and the carpet was replaced with tile flooring in the 3D room. We bought commercially available enclosures equipped with the filtration system. Further study will include a detailed study of UFP emission and effect of enclosures on indoor air quality in the 3D printing room.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: neelambh@ufl.edu. ORCID

Neelam Bharti: 0000-0002-0551-5949 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We acknowledge Environment Health and Safety, University of Florida, for providing the instrument; Marston Science Library 3D services staff; and Michael Gladle, University of Delaware, for helpful suggestions.

CONCLUSION 3D printing has revolutionized education, teaching, and research with tremendous applications and has gained popularity as a desktop industry. The inclusion of 3D printers in F

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DOI: 10.1021/acs.jchemed.6b00745 J. Chem. Educ. XXXX, XXX, XXX−XXX