3D Printed Shape Memory Polymers Produced via Direct Pellet Extrusion

Shape memory polymers (SMPs) are materials capable of changing their structural configuration from a fixed shape to a temporary shape, and vice versa when subjected to a thermal stimulus. The present work has investigated the 3D printing process of a shape memory polymer (SMP)-based polyurethane using a material extrusion technology. Here, SMP pellets were fed into a printing unit, and actuating coupons were manufactured. In contrast to the conventional film-casting manufacturing processes of SMPs, the use of 3D printing allows the production of complex parts for smart electronics and morphing structures. In the present work, the memory performance of the actuating structure was investigated, and their fundamental recovery and mechanical properties were characterized. The preliminary results show that the assembled structures were able to recover their original conformation following a thermal input. The printed parts were also stamped with a QR code on the surface to include an unclonable pattern for addressing counterfeit features. The stamped coupons were subjected to a deformation-recovery shape process, and it was observed that the QR code was recognized after the parts returned to their original shape. The combination of shape memory effect with authentication features allows for a new dimension of counterfeit thwarting. The 3D-printed SMP parts in this work were also combined with shape memory alloys to create a smart actuator to act as a two-way switch to control data collection of a microcontroller.

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Vitrimer-Like Shape Memory Polymers: Characterization and Applications in Reshaping and Manufacturing

Polymers ◽

10.3390/polym12102330 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2330

Author(s):

Tao Xi Wang ◽

Hong Mei Chen ◽

Abhijit Vijay Salvekar ◽

Junyi Lim ◽

Yahui Chen ◽

...

Keyword(s):

Solid State ◽

3D Printing ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Memory Performance ◽

Shape Memory Polymers ◽

Cross Linking ◽

Potential Applications ◽

Actual Shape

The shape memory effect (SME) refers to the ability of a material to recover its original shape, but only in the presence of a right stimulus. Most polymers, either thermo-plastic or thermoset, can have the SME, although the actual shape memory performance varies according to the exact material and how the material is processed. Vitrimer, which is between thermoset and thermo-plastic, is featured by the reversible cross-linking. Vitrimer-like shape memory polymers (SMPs) combine the vitrimer-like behavior (associated with dissociative covalent adaptable networks) and SME, and can be utilized to achieve many novel functions that are difficult to be realized by conventional polymers. In the first part of this paper, a commercial polymer is used to demonstrate how to characterize the vitrimer-like behavior based on the heating-responsive SME. In the second part, a series of cases are presented to reveal the potential applications of vitrimer-like SMPs and their composites. It is concluded that the vitrimer-like feature not only enables many new ways in reshaping polymers, but also can bring forward new approaches in manufacturing, such as, rapid 3D printing in solid state on space/air/sea missions.

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Frontally polymerizable shape memory polymer for 3D printing of free-standing structures

Smart Materials and Structures ◽

10.1088/1361-665x/ac41ea ◽

2021 ◽

Author(s):

Yongsan An ◽

Joon Hyeok Jang ◽

Ji Ho Youk ◽

Woong-Ryeol Yu

Keyword(s):

Shape Memory ◽

Memory Performance ◽

Shape Memory Polymer ◽

Three Dimensional ◽

Frontal Polymerization ◽

4D Printing ◽

Free Standing ◽

Time Shape ◽

Standing Structure ◽

3D Printed

Abstract Four-dimensional (4D) printing is used to describe three-dimensional (3D)-printed objects with properties that change over time. Shape memory polymers (SMPs) are representative materials for 4D printing technologies. The ability to print geometrically complex, free-standing forms with SMPs is crucial for successful 4D printing. In this study, an SMP capable of frontal polymerization featuring exothermic self-propagation was synthesized by adding cyclooctene to a poly(dicyclopentadiene) network, resulting in switching segments. The rheological properties of this SMP were controlled by adjusting incubation time. A nozzle system was designed such that the SMP could be printed with simultaneous polymerization to yield a free-standing structure. The printing speed was set to 3 cm/min according to the frontal polymerization speed. A free-standing, hexagonal spiral was successfully printed and printed spiral structure showed excellent shape memory performance with a fixity ratio of about 98% and a recovery ratio of 100%, thereby demonstrating the 3D printability and shape memory performance of frontally polymerizable SMPs.

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Influence of Radialization Dosage on Shape Memory Effect of Polystyrene Copolymer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.47-50.690 ◽

2008 ◽

Vol 47-50 ◽

pp. 690-693 ◽

Cited By ~ 2

Author(s):

Da Wei Zhang ◽

Jin Song Leng ◽

Yan Ju Liu

Keyword(s):

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Smart Materials ◽

Shape Recovery ◽

Memory Performance ◽

Shape Memory Polymer ◽

Shape Memory Polymers ◽

Mechanical Analysis ◽

Styrene Copolymer

This paper is concerned about the synthesis of shape memory styrene copolymer and the investigation of the influence of radialization dosage on its shape memory effect. As one of novel actuators in smart materials, shape memory polymers (SMPs) have been investigated intensively. Styrene copolymer with proper cross-linking degree can exhibit shape memory effect (SME). In this paper, the influence of radialization on shape memory effect of styrene copolymer was investigated through altering the dosage of radialization. The radialization dosage of styrene copolymer was determined by changed radicalization time. The glass transition temperature (Tg) of styrene copolymerwas measured by Dynamic Mechanical Analysis (DMA). The shape memory performance of styrene copolymer with different radiated dosage was also evaluated. Results indicated that the shape memory polymer (SMP) was synthesized successfully. The Tg increased from 60°C to 65°C followed by increasing the radialization dosage. Moreover, the SMP experienced good SME and the largest reversible strain of the SMP reached as high as 150%. When heating above Tg+30°C (different copolymers performed different Tg), the shape recovery speed of the copolymers increased with increasing the radialization dosage. However, the recovery speed decreased with increasing the radialization dosage at the same temperature of 95°C.

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Multiscale Study on Effect of Humidity on Shape Memory Polymers Used in 3D Printing

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4050550 ◽

2021 ◽

pp. 1-25

Author(s):

Frank Livolsli ◽

Thomas May ◽

Dylan Caputo ◽

Kamran Fouladi ◽

Babak Eslami

Keyword(s):

3D Printing ◽

Shape Memory ◽

Fluid Dynamic ◽

Shape Memory Polymers ◽

3 Dimensional ◽

Force Microscopy ◽

Atomic Force ◽

Macro Scale ◽

3D Printed ◽

Scale Characterization

Abstract Shape memory polymers (SMP) are used in the 3D printing field for different applications such as soft robotics or medical devices. Although this technology has expanded the capabilities of additive manufacturing, there still exists fundamental questions regarding the optimum condition for manufacturing these 3D printed parts. Various factors play a crucial role in the final quality of printed parts, such as deposition orientation, percentage infill, or environmental conditions. In this paper, we study the effect of humidity on commercially available SMPs (NinjaFlex©) at both micro- and macro-scale. By performing a 3-dimensional computational fluid dynamic model for the printing environment, it is found there are significant temperature and humidity fluctuations around the hot-end and printing bed. Macro-scale characterization through ASTM D638 tensile testing shows that for humidity levels higher than 60% there is 5-10% reduction in the strength of material (ultimate strength and tangent modulus). This study is verified by micro-scale characterization performed with atomic force microscopy on thin-films. It is shown that in addition to the effect of humidity on the stiffness of materials, there is an effect on the loss moduli of the matter as well. As humidity increases, these polymers become more viscoelastic. Simultaneously, it is shown higher humidity levels cause increased micro-level surface roughness, which can be the cause for the strength reduction for higher humidities.

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Pressure Orientation-Dependent Recovery of 3D-Printed PLA Objects with Varying Infill Degree

Polymers ◽

10.3390/polym13081275 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1275 ◽

Cited By ~ 1

Author(s):

Guido Ehrmann ◽

Andrea Ehrmann

Keyword(s):

Shape Memory ◽

Fused Deposition Modeling ◽

Static Load ◽

Shape Memory Polymer ◽

Applied Pressure ◽

Poly Lactic Acid ◽

Fused Deposition ◽

Deposition Modeling ◽

Load Tests ◽

3D Printed

Poly(lactic acid) is not only one of the most often used materials for 3D printing via fused deposition modeling (FDM), but also a shape-memory polymer. This means that objects printed from PLA can, to a certain extent, be deformed and regenerate their original shape automatically when they are heated to a moderate temperature of about 60–100 °C. It is important to note that pure PLA cannot restore broken bonds, so that it is necessary to find structures which can take up large forces by deformation without full breaks. Here we report on the continuation of previous tests on 3D-printed cubes with different infill patterns and degrees, now investigating the influence of the orientation of the applied pressure on the recovery properties. We find that for the applied gyroid pattern, indentation on the front parallel to the layers gives the worst recovery due to nearly full layer separation, while indentation on the front perpendicular to the layers or diagonal gives significantly better results. Pressing from the top, either diagonal or parallel to an edge, interestingly leads to a different residual strain than pressing from front, with indentation on top always firstly leading to an expansion towards the indenter after the first few quasi-static load tests. To quantitatively evaluate these results, new measures are suggested which could be adopted by other groups working on shape-memory polymers.

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Harnessing reversible dry adhesion using shape memory polymer microparticles

RSC Advances ◽

10.1039/d1ra01473k ◽

2021 ◽

Vol 11 (32) ◽

pp. 19616-19622

Author(s):

Wenbing Li ◽

Junhao Liu ◽

Wanting Wei ◽

Kun Qian

Keyword(s):

Shape Memory ◽

Shape Memory Polymer ◽

Shape Memory Polymers ◽

Memory Effects ◽

Reversible Adhesion ◽

Dry Adhesion ◽

Bonding Property ◽

Shape Memory Effects ◽

Polymer Microparticles

Shape memory polymers can provide excellent bonding property because of their shape memory effects. This paper proposes an adhesive unit that is capable of repeatable smart adhesion and exhibits reversible adhesion under heating.

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Structural multi-colour invisible inks with submicron 4D printing of shape memory polymers

Nature Communications ◽

10.1038/s41467-020-20300-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Wang Zhang ◽

Hao Wang ◽

Hongtao Wang ◽

John You En Chan ◽

Hailong Liu ◽

...

Keyword(s):

Shape Memory ◽

Information Hiding ◽

Shape Memory Polymer ◽

Shape Memory Polymers ◽

Photonic Devices ◽

Temperature Sensitive ◽

4D Printing ◽

Two Photon ◽

Shape Memory Effects ◽

Nanoscale Structure

AbstractFour-dimensional (4D) printing of shape memory polymer (SMP) imparts time responsive properties to 3D structures. Here, we explore 4D printing of a SMP in the submicron length scale, extending its applications to nanophononics. We report a new SMP photoresist based on Vero Clear achieving print features at a resolution of ~300 nm half pitch using two-photon polymerization lithography (TPL). Prints consisting of grids with size-tunable multi-colours enabled the study of shape memory effects to achieve large visual shifts through nanoscale structure deformation. As the nanostructures are flattened, the colours and printed information become invisible. Remarkably, the shape memory effect recovers the original surface morphology of the nanostructures along with its structural colour within seconds of heating above its glass transition temperature. The high-resolution printing and excellent reversibility in both microtopography and optical properties promises a platform for temperature-sensitive labels, information hiding for anti-counterfeiting, and tunable photonic devices.

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