A review of 3D printing processes and materials for soft robotics

Purpose Soft robotics is currently a rapidly growing new field of robotics whereby the robots are fundamentally soft and elastically deformable. Fabrication of soft robots is currently challenging and highly time- and labor-intensive. Recent advancements in three-dimensional (3D) printing of soft materials and multi-materials have become the key to enable direct manufacturing of soft robots with sophisticated designs and functions. Hence, this paper aims to review the current 3D printing processes and materials for soft robotics applications, as well as the potentials of 3D printing technologies on 3D printed soft robotics. Design/methodology/approach The paper reviews the polymer 3D printing techniques and materials that have been used for the development of soft robotics. Current challenges to adopting 3D printing for soft robotics are also discussed. Next, the potentials of 3D printing technologies and the future outlooks of 3D printed soft robotics are presented. Findings This paper reviews five different 3D printing techniques and commonly used materials. The advantages and disadvantages of each technique for the soft robotic application are evaluated. The typical designs and geometries used by each technique are also summarized. There is an increasing trend of printing shape memory polymers, as well as multiple materials simultaneously using direct ink writing and material jetting techniques to produce robotics with varying stiffness values that range from intrinsically soft and highly compliant to rigid polymers. Although the recent work is done is still limited to experimentation and prototyping of 3D printed soft robotics, additive manufacturing could ultimately be used for the end-use and production of soft robotics. Originality/value The paper provides the current trend of how 3D printing techniques and materials are used particularly in the soft robotics application. The potentials of 3D printing technology on the soft robotic applications and the future outlooks of 3D printed soft robotics are also presented.

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3D printing of biofiber-reinforced composites and their mechanical properties: a review

Rapid Prototyping Journal ◽

10.1108/rpj-08-2019-0214 ◽

2020 ◽

Vol 26 (6) ◽

pp. 1113-1129

Author(s):

Lai Jiang ◽

Xiaobo Peng ◽

Daniel Walczyk

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Reinforced Composites ◽

Research Directions ◽

Content Type ◽

Reinforced Composite ◽

3D Printed ◽

Materials Used ◽

Printing Processes ◽

Pure Resin

Purpose This paper aims to summarize the up-to-date research performed on combinations of various biofibers and resin systems used in different three-dimensional (3D) printing technologies, including powder-based, material extrusion, solid-sheet and liquid-based systems. Detailed information about each process, including materials used and process design, are described, with the resultant products’ mechanical properties compared with those of 3D-printed parts produced from pure resin or different material combinations. In most processes introduced in this paper, biofibers are beneficial in improving the mechanical properties of 3D-printed parts and the biodegradability of the parts made using these green materials is also greatly improved. However, research on 3D printing of biofiber-reinforced composites is still far from complete, and there are still many further studies and research areas that could be explored in the future. Design/methodology/approach The paper starts with an overview of the current scenario of the composite manufacturing industry and then the problems of advanced composite materials are pointed out, followed by an introduction of biocomposites. The main body of the paper covers literature reviews of recently emerged 3D printing technologies that were applied to biofiber-reinforced composite materials. This part is classified into subsections based on the form of the starting materials used in the 3D printing process. A comprehensive conclusion is drawn at the end of the paper summarizing the findings by the authors. Findings Most of the biofiber-reinforced 3D-printed products exhibited improved mechanical properties than products printed using pure resin, indicating that biofibers are good replacements for synthetic ones. However, synthetic fibers are far from being completely replaced by biofibers due to several of their disadvantages including higher moisture absorbance, lower thermal stability and mechanical properties. Many studies are being performed to solve these problems, yet there are still some 3D printing technologies in which research concerning biofiber-reinforced composite parts is quite limited. This paper unveils potential research directions that would further develop 3D printing in a sustainable manner. Originality/value This paper is a summary of attempts to use biofibers as reinforcements together with different resin systems as the starting material for 3D printing processes, and most of the currently available 3D printing techniques are included herein. All of these attempts are solutions to some principal problems with current 3D printing processes such as the limit in the variety of materials and the poor mechanical performance of 3D printed parts. Various types of biofibers are involved in these studies. This paper unveils potential research directions that would further widen the use of biofibers in 3D printing in a sustainable manner.

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Optical elements from 3D printed polymers

e-Polymers ◽

10.1515/epoly-2021-0061 ◽

2021 ◽

Vol 21 (1) ◽

pp. 549-565

Author(s):

Tomasz Blachowicz ◽

Guido Ehrmann ◽

Andrea Ehrmann

Keyword(s):

3D Printing ◽

Layered Structure ◽

Emerging Technologies ◽

Optical Elements ◽

Rapid Production ◽

Freeform Optics ◽

3D Printed ◽

Printing Processes ◽

Printing Techniques ◽

Individual Objects

Abstract 3D printing belongs to the emerging technologies of our time. Describing diverse specific techniques, 3D printing enables rapid production of individual objects and creating shapes that would not be produced with other techniques. One of the drawbacks of typical 3D printing processes, however, is the layered structure of the created parts. This is especially problematic in the production of optical elements, which in most cases necessitate highly even surfaces. To meet this challenge, advanced 3D printing techniques as well as other sophisticated solutions can be applied. Here, we give an overview of 3D printed optical elements, such as lenses, mirrors, and waveguides, with a focus on freeform optics and other elements for which 3D printing is especially well suited.

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A review on the role of 3D printing in the fight against COVID-19: safety and challenges

Rapid Prototyping Journal ◽

10.1108/rpj-08-2020-0198 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Sapam Ningthemba Singh ◽

Vavilada Satya Swamy Venkatesh ◽

Ashish Bhalchandra Deoghare

Keyword(s):

Supply Chain ◽

3D Printing ◽

Three Dimensional ◽

Content Type ◽

Medical Supplies ◽

Future Challenges ◽

Safety And Reliability ◽

3D Printed ◽

Comprehensive Study

Purpose During the COVID-19 pandemic, the three-dimensional (3D) printing community is actively participating to address the supply chain gap of essential medical supplies such as face masks, face shields, door adapters, test swabs and ventilator valves. This paper aims to present a comprehensive study on the role of 3D printing during the coronavirus (COVID-19) pandemic, its safety and its challenges. Design/methodology/approach This review paper focuses on the applications of 3D printing in the fight against COVID-19 along with the safety and challenges associated with 3D printing to fight COVID-19. The literature presented in this paper is collected from the journal indexing engines including Scopus, Google Scholar, ResearchGate, PubMed, Web of Science, etc. The main keywords used for searches were 3D printing COVID-19, Safety of 3D printed parts, Sustainability of 3D printing, etc. Further possible iterations of the keywords were used to collect the literature. Findings The applications of 3D printing in the fight against COVID-19 are 3D printed face masks, shields, ventilator valves, test swabs, drug deliveries and hands-free door adapters. As most of these measures are implemented hastily, the safety and reliability of these parts often lacked approval. The safety concerns include the safety of the printed parts, operators and secondary personnel such as the workers in material preparation and transportation. The future challenges include sustainability of the process, long term supply chain, intellectual property and royalty-free models, etc. Originality/value This paper presents a comprehensive study on the applications of 3D printing in the fight against COVID-19 with emphasis on the safety and challenges in it.

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Off-Axis Diffractive Optics for Compact Terahertz Detection Setup

Applied Sciences ◽

10.3390/app10238594 ◽

2020 ◽

Vol 10 (23) ◽

pp. 8594

Author(s):

Paweł Komorowski ◽

Mateusz Surma ◽

Michał Walczakowski ◽

Przemysław Zagrajek ◽

Agnieszka Siemion

Keyword(s):

3D Printing ◽

Small Volume ◽

Optical Element ◽

Structure Design ◽

Thz Radiation ◽

Direct Printing ◽

Terahertz Detection ◽

3D Printed ◽

Printing Techniques ◽

Optical Structure

Medical and many other applications require small-volume setups enabling terahertz imaging. Therefore, we aim to develop a device for the in-reflection examination of the samples. Thus, in this article, we focus on the diffractive elements for efficient redirection and focusing of the THz radiation. A terahertz diffractive optical structure has been designed, optimized, manufactured (using extrusion-based 3D printing) and tested. Two manufacturing methods have been used—direct printing of the structures from PA12, and casting of the paraffin structures out of 3D-printed molds. Also, the limitations of the off-axis focusing have been discussed. To increase the efficiency, an iterative algorithm has been proposed that optimizes off-axis structures to focus the radiation into small focal spots located far from the optical axis, at an angle of more than 30 degrees. Moreover, the application of higher-order kinoform structure design allowed the maintaining of the smallest details of the manufactured optical element, using 3D printing techniques.

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Effect of temperature on the mechanical properties of 3D-printed PLA tensile specimens

Rapid Prototyping Journal ◽

10.1108/rpj-04-2017-0055 ◽

2018 ◽

Vol 24 (8) ◽

pp. 1337-1346 ◽

Cited By ~ 12

Author(s):

Marzio Grasso ◽

Lyes Azzouz ◽

Paula Ruiz-Hincapie ◽

Mauro Zarrelli ◽

Guogang Ren

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Mechanical Test ◽

Optical Microscope ◽

Middle Part ◽

Gauge Length ◽

Effect Of Temperature ◽

Content Type ◽

Relevant Effect ◽

3D Printed

Purpose Recent advancements of 3D printing technology have brought forward the interest for this technique in many engineering fields. This study aims to focus on mechanical properties of the polylactic acid (PLA) feeding material under different thermal conditions for a typical fusion deposition of 3D printer system. Design/methodology/approach Specimens were tested under static loading within the range 20ºC to 60ºC considering different infill orientations. The combined effect of temperature and filament orientation is investigated in terms of constitutive material parameters and final failure mechanisms. The difference between feeding system before and post-3D printing was also assessed by mechanical test on feeding filament to verify the thermal profile during the deposition phase. Findings The results in terms of Young’s modulus, ultimate tensile strength (UTS), strain at failure (εf) and stress at failure (σf) are presented and discussed to study the influence of process settings over the final deposited material. Fracture surfaces have been investigated using an optical microscope to link the phenomenological interpretation of the failure with the micro-mechanical behaviour. Experimental results show a strong correlation between stiffness and strength with the infill orientation and the temperature values. Moreover, a relevant effect is related to deformed geometry of the filament approaching glass transition region of the polymer according to the deposition orientation. Research limitations/implications The developed method can be applied to optimise the stiffness and strength of any 3D-printed composite according to the infill orientation. Practical implications To avoid the failure of specimens outside the gauge length, a previously proposed modification to the geometry was adopted. The geometry has a parabolic profile with a curvature of 1,000 mm tangent to the middle part of the specimen. Originality/value Several authors have reported the stiffness and strength of 3D-printed parts under static and ambient temperature for different build parameters. However, there is a lack of literature on the combination of the latter with the temperature effects on the mechanical properties which this paper covers.

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O Futuro de Soft Robotics: Uma Revisão Bibliográfica

10.5753/eri-mt.2019.8617 ◽

2019 ◽

Author(s):

Paulo Dos Santos ◽

Guilherme Da Silva ◽

Juliana Silva

Keyword(s):

Soft Robotics ◽

Review Of The Literature ◽

Soft Robots ◽

Medical Area ◽

The Future

This study seeks to explain a new theme that has a potential of great impact in the future. Soft robots are robots that, because they are soft and not limited by their axes, can go beyond how rigid robots work. The objective of this study is to present a review of the literature on soft robots. The literature shows little research on these robots, presenting difficulties mainly in the research of sensors and materials to be used in their construction. Despite the difficulties, the increase of research with this approach will have great impacts, mainly in the medical area.

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Approaches of combining a 3D-printed elastic structure and a hydrogel to create models for plant-inspired actuators

MRS Advances ◽

10.1557/s43580-021-00081-6 ◽

2021 ◽

Author(s):

Nadia Rodriguez ◽

Anil K. Bastola ◽

Marc Behl ◽

Patricia Soffiatti ◽

Nick P. Rowe ◽

...

Keyword(s):

3D Printing ◽

Functional Traits ◽

Active Component ◽

Preliminary Investigation ◽

Polymeric Materials ◽

Southeastern Brazil ◽

Passive Component ◽

Material System ◽

3D Printed ◽

Printing Techniques

Abstract Inspired by the interesting functional traits of a climbing cactus, Selenicereus setaceus, found in the forest formations of Southeastern Brazil, we formulated a hypothesis that we can directly learn from the plants to develop multi-functional artificial systems by means of a multi-disciplinary approach. In this context, our approach is to take advantage of 3D-printing techniques and shape-memory hydrogels synergistically to mimic the functional traits of the cactus. This work reports on the preliminary investigation of cactus-inspired artificial systems. First, we 3D-printed soft polymeric materials and characterized them, which defines the structure and is a passive component of a multi-material system. Second, different hydrogels were synthesized and characterized, which is an active component of a multi-material system. Finally, we investigated how the hydrogel can be integrated into the 3D-printed constructs to develop artificial functional systems. Graphic abstract

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A physical investigation of dimensional and mechanical characteristics of 3D printed nut and bolt for industrial applications

Rapid Prototyping Journal ◽

10.1108/rpj-09-2021-0250 ◽

2022 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Ramesh Chand ◽

Vishal S. Sharma ◽

Rajeev Trehan ◽

Munish Kumar Gupta

Keyword(s):

Mechanical Properties ◽

Shear Strength ◽

3D Printing ◽

Surface Properties ◽

3D Printer ◽

Content Type ◽

Safety Issues ◽

Machine Failure ◽

Sharp Edges ◽

3D Printed

Purpose A nut bolt joint is a primary device that connects mechanical components. The vibrations cause bolted joints to self-loosen. Created by motors and engines, leading to machine failure, and there may be severe safety issues. All the safety issues and self-loosen are directly and indirectly the functions of the accuracy and precision of the fabricated nut and bolt. Recent advancements in three-dimensional (3D) printing technologies now allow for the production of intricate components. These may be used technologies such as 3D printed bolts to create fasteners. This paper aims to investigate dimensional precision, surface properties, mechanical properties and scanning electron microscope (SEM) of the component fabricated using a multi-jet 3D printer. Design/methodology/approach Multi-jet-based 3D printed nut-bolt is evaluated in this paper. More specifically, liquid polymer-based nut-bolt is fabricated in sections 1, 2 and 3 of the base plate. Five nuts and bolts are fabricated in these three sections. Findings Dimensional inquiry (bolt dimension, general dimensions’ density and surface roughness) and mechanical testing (shear strength of nut and bolt) were carried out throughout the study. According to the ISO 2768 requirements for the General Tolerances Grade, the nut and bolt’s dimensional examination (variation in bolt dimension, general dimensions) is within the tolerance grades. As a result, the multi-jet 3D printing (MJP)-based 3D printer described above may be used for commercial production. In terms of mechanical qualities, when the component placement moves from Sections 1 to 3, the density of the manufactured part decreases by 0.292% (percent) and the shear strength of the nut and bolt decreases by 30%. According to the SEM examination, the density of the River markings, sharp edges, holes and sharp edges increased from Sections 1 to 3, which supports the findings mentioned above. Originality/value Hence, this work enlightens the aspects causing time lag during the 3D printing in MJP. It causes variation in the dimensional deviation, surface properties and mechanical properties of the fabricated part, which needs to be explored.

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Use of polymer concrete for large-scale 3D printing

Rapid Prototyping Journal ◽

10.1108/rpj-12-2019-0316 ◽

2021 ◽

Vol 27 (3) ◽

pp. 465-474

Author(s):

Martin Krčma ◽

David Škaroupka ◽

Petr Vosynek ◽

Tomáš Zikmund ◽

Jozef Kaiser ◽

...

Keyword(s):

3D Printing ◽

Large Scale ◽

Mechanical Performance ◽

Construction Material ◽

Polymer Concrete ◽

Fused Deposition Modelling ◽

Cast State ◽

Content Type ◽

Fused Deposition ◽

3D Printed

Purpose This paper aims to focus on the evaluation of a polymer concrete as a three-dimensional (3D) printing material. An associated company has developed plastic concrete made from reused unrecyclable plastic waste. Its intended use is as a construction material. Design/methodology/approach The concrete mix, called PolyBet, composed of polypropylene and glass sand, is printed by the fused deposition modelling process. The process of material and parameter selection is described. The mechanical properties of the filled material were compared to its cast state. Samples were made from castings and two different orientations of 3D-printed parts. Three-point flex tests were carried out, and the area of the break was examined. Computed tomography of the samples was carried out. Findings The influence of the 3D printing process on the material was evaluated. The mechanical performance of the longitudinal samples was close to the cast state. There was a difference in the failure mode between the states, with cast parts exhibiting a tougher behaviour, with fractures propagating in a stair-like manner. The 3D-printed samples exhibited high degrees of porosity. Originality/value The results suggest that the novel material is a good fit for 3D printing, with little to no degradation caused by the process. Layer adhesion was shown to be excellent, with negligible effect on the finished part for the longitudinal orientation. That means, if large-scale testing of buildability is successful, the material is a good fit for additive manufacturing of building components and other large-scale structures.

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Effects of post-curing conditions on mechanical properties of 3D printed clear dental aligners

Rapid Prototyping Journal ◽

10.1108/rpj-04-2019-0118 ◽

2020 ◽

Vol 26 (8) ◽

pp. 1337-1344 ◽

Cited By ~ 1

Author(s):

Prashant Jindal ◽

Mamta Juneja ◽

Divya Bajaj ◽

Francesco Luke Siena ◽

Philip Breedon

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Mechanical Strength ◽

Financial Burden ◽

Experimental Studies ◽

Cost Savings ◽

Time Duration ◽

Content Type ◽

Curing Conditions ◽

3D Printed

Purpose 3D printing techniques have been widely used for manufacturing complex parts for various dental applications. For achieving suitable mechanical strength, post-cure processing is necessary, where the relative time duration and temperature specification also needs to be defined. The purpose of this study/paper is to assess the effects of post curing conditions and mechanical properties of 3D printed clear dental aligners Design/methodology/approach Dental long-term clear resin material has been used for 3D printing of dental aligners using a Formlabs 3D printer for direct usage on patients. Post-curing conditions have been varied, all of which have been subjected to mechanical compression loading of 1,000 N to evaluate the curing effects on the mechanical strength of the aligners. Findings The experimental studies provide significant insight into both temperatures and time durations that could provide sufficient compressive mechanical strength to the 3D printed clear dental aligners. It was observed that uncured aligners deformed plastically with large deformations under the loading conditions, whereas aligners cured between 400°C–800°C for 15–20 min deformed elastically before fragmenting into pieces after safely sustaining higher compressive loads between 495 N and 666 N. The compressive modulus ratio for cured aligners ranged between 4.46 and 5.90 as compared to uncured aligners. For shorter cure time durations and lower temperature conditions, an appropriate elevated compressive strength was also achieved. Originality/value Based on initial assessments by dental surgeons, suitable customised clear aligners can be designed, printed and cured to the desired levels based on patient’s requirements. This could result in time, energy and unit production cost savings, which ultimately would help to alleviate the financial burden placed on both the health service and their patients.

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