A Review of 3D Printing Technologies for Soft Polymer Materials

Zhou, Luyu; Fu, Jianzhong; He, Yong

doi:10.1002/adfm.202000187

Cited by 459 publications

(353 citation statements)

References 327 publications

(694 reference statements)

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“…Accordingly, extensive efforts have been made to identify and target specific soft, elastic acrylate formulations. [ 5–9 ] Introducing alternative crosslinking chemistries to the VAM realm, as well as AM more broadly, is highly desirable as an alternative method to gain access to a wider range of mechanical, thermal, and optical performance. [ 10–14 ] Thiol‐ene‐based polymers are one class of materials that have drawn significant attention owing to their controllable, tunable mechanical properties.…”

Section: Figurementioning

confidence: 99%

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

et al. 2020

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Volumetric additive manufacturing (VAM) is an emerging approach to photo polymerbased 3D printing that produces complex 3D structures in a single step, rather than from layer-by-layer assembly. [1] This paradigm holds promise because it overcomes many of the drawbacks of layerbased fabrication, such as long build times and rough surfaces. VAM also augurs a broadening of the materials available for photopolymer 3D printing, having fewer constraints on viscosity and reactivity compared to layerwise printing. Indeed, though VAM has been demonstrated with extremely soft hydrogels, [2,3] it has relied until now almost exclusively on acrylate-based chemistry. [4] This is natural, because the oxygen inhibition of acrylate polymerization provides the threshold behavior required for VAM. However, acrylate chemistry is in general limiting due to the brittle and glassy properties of the resulting materials. Accordingly, extensive efforts have been made to identify and target specific soft, elastic acrylate formulations. [5-9] Introducing alternative crosslinking chemistries to the VAM realm, as well as AM more broadly, is highly desirable as an alternative method to gain access to a wider range of mechanical, thermal, and optical performance. [10-14] Thiol-ene-based polymers are one class of materials that have drawn significant attention owing to their controllable, tunable mechanical properties. [15-17] This is generally attributed to more uniform molecular networks in thiol-ene materials, resulting from the step-growth mechanism of the polymerization reaction. [18,19] Thiol-ene materials have already shown promise for applications including use in adhesives, electronics, and as biomaterials. [20,21] This work expands the versatility of volumetric AM by introducing a new class of VAM-compatible thiol-ene resins. We demonstrate the formulation of thiol-ene resins with the nonlinear threshold-type kinetics required for VAM and show bulk-equivalent performance in the resulting 3D printed parts, confirming the advantage of the layerless whole-part process. In our volumetric AM system, a 3D distribution of light energy is delivered to the resin vat by superimposing exposures from multiple angles, a method termed computed axial litho graphy (CAL) (Figure 1a). [2] The exposures are a sequence of projections calculated from 3D CAD models using algorithms from computed Volumetric additive manufacturing (VAM) forms complete 3D objects in a single photocuring operation without layering defects, enabling 3D printed polymer parts with mechanical properties similar to their bulk material counterparts. This study presents the first report of VAM-printed thiol-ene resins. With well-ordered molecular networks, thiol-ene chemistry accesses polymer materials with a wide range of mechanical properties, moving VAM beyond the limitations of commonly used acrylate formulations. Since free-radical thiol-ene polymerization is not inhibited by oxygen, the nonlinear threshold response required in VAM is introduced by incorporating 2,2,6,6-tetrameth...

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Section: Figurementioning

confidence: 99%

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

et al. 2020

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“…Up to now, a collection of fabrication techniques are put forward to develop the flexible strain sensors, including photolithography, [ 13,14 ] laser direct writing, [ 15–19 ] stencil printing, [ 20 ] screen printing, [ 21 ] inkjet printing, [ 22 ] and 3D printing. [ 3,23–27 ] Among these fabrication techniques, 3D printing or additive manufacturing is brought into focus for its simple process, less labor, capability to fabricate customized complex 3D patterns and structures in maskless manners. The technologies of 3D printing for flexible electronic devices mainly include fused deposition modeling (FDM), [ 28 ] extrusion printing, [ 29–31 ] stereolithography (SLA), [ 32 ] and digital light processing (DLP).…”

Section: Introductionmentioning

confidence: 99%

3D Printing of Flexible Strain Sensor Array Based on UV‐Curable Multiwalled Carbon Nanotube/Elastomer Composite

Xiao

Cheng

Yin

et al. 2020

Adv Materials Technologies

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Internet of things (IoT) is expected to significantly improve every aspect of society, especially in soft robotics, structural health monitoring, and human motion detection. Flexible strain sensors with high‐performance characteristics as well as highly efficient and cost‐effective maskless fabrication methods are the key components of IoT for these applications. Herein, a 3D printing technology using digital light processing is developed to fabricate high‐performance flexible strain sensors based on UV‐curable multiwalled carbon nanotubes/elastomer (MWCNT/EA) composite. The MWCNT/EA‐based device with 2 wt% MWCNTs delivers a sensitivity of 8.939 with a linearity up to 45% strain. Additionally, the sensor has a detectable strain range from 0.01% to 60%, a high mechanical durability (10 000 cycles), and linear responses to humidity and temperature. Numerical simulation and impedance study indicate that the sensor works on the deformation‐induced reduction of MWCNT conductive pathway. The developed device can be used to detect various external deformation, when combined with a near‐field communication circuit. Moreover, a 4 × 4 strain sensor array is developed for sensing external stimuli distribution, further demonstrating the high performance of the 3D printed device.

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“…[ 41 ] Several methods for 3D printing of silicone have also been recently developed including SLA techniques (vat polymerization), material jetting, and material extrusion, with crosslinking occurring via addition polymerization or UV curing. [ 175 ]…”

Section: Polymers In Prostheticsmentioning

confidence: 99%

Past, Present, and Future of Soft‐Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing

et al. 2020

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past 30 years, [12,13] it is only the last decade that has seen its rapid development as part of the fourth industrial revolution. [14] This change in practice is evidenced by the significant fraction of recent literature describing advances in 3D printed prostheses, including technological advances [4,15-18] and clinical reports. [19,20] Further innovations involving collaborations between clinicians, academics, and industry, promise even greater capabilities. The future will see 3D printers that can mix materials as desired during fabrication [21] and those that can 3D print organic semiconductors and piezoelectric polymers for sensing and bionics [22-24] (Figure 1). This report is focused on polymers for soft tissue, external, personalized, prosthetics with clinical applications for the ear, [25] nose, [26] eye, [27] face, [28] breast, [29] and hand. [30] The characteristics of both traditional and 3D printable polymeric materials, as well as current advanced manufacturing technologies and those in development, are also reviewed. The earliest evidence of prosthetics dates back to ≈2300 BC, where Egyptian mummies have been discovered with eye, nose, and genital reconstructions fashioned from plaster packed with mud, sand, linen, butter, or soda (Figure 1). [31] Wood, cloth, natural waxes, resins, and metals were later used as the material of choice for rudimentary prostheses. [32] Prostheses remained relatively unchanged for thousands of years until the 16th century, where prosthetic noses and eyes were made from parchment, wax, wood, hard rubber, gold, silver, and copper. [33] Metals continued as a fundamental material throughout the 19th century, largely due to their ability to be shaped and molded as needed. [34,35] One of the first polymers to be used in prosthetics, poly(methyl methacrylate) (PMMA), was developed in response to the glass shortages in the World Wars of the 20th Century. [36] This polymer went on to become the most common prosthetic material of the time, and still finds use today in artificial eyes [33] and prosthetic substructures. [37] Further innovations in the 20th century produced many new polymers, such as vinyls, copolymers, plastisols, and one of the most significant materials in prosthetics, silicone. [38] Discovered in the early 1900s by Fredrick Kipping, silicone was first used in prosthetics by George W Barnhart in 1960. [39] This versatile polymer remains a primary prosthetic material today due to its soft tissue-like properties, ease of manipulation, chemical inertness, durability, and excellent biocompatibility. [40,41] The search for alternative materials Millions of people worldwide experience disfigurement due to cancers, congenital defects, or trauma, leading to significant psychological, social, and economic disadvantage. Prosthetics aim to reduce their suffering by restoring aesthetics and function using synthetic materials that mimic the characteristics of native tissue. In the 1900s, natural materials used for thousands of years in prosthetics were replaced by syntheti...

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A Review of 3D Printing Technologies for Soft Polymer Materials

Cited by 459 publications

References 327 publications

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

Highly Tunable Thiol‐Ene Photoresins for Volumetric Additive Manufacturing

3D Printing of Flexible Strain Sensor Array Based on UV‐Curable Multiwalled Carbon Nanotube/Elastomer Composite

Past, Present, and Future of Soft‐Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing

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