Shape memory polymers (SMPs) represent a highly interesting class of materials. As one representative of the intelligent polymeric systems, these materials gained significant interest in recent ...years. Consequently, the variety of materials investigated virtually exploded and several promising shape memory effects have been developed. The present review will provide a short overview on the history of SMPs as well as the current developments and concepts for shape memory polymers. Additionally, future developments in this field will be discussed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Shaping tissue with shape memory materials Huang, W.M.; Song, C.L.; Fu, Y.Q. ...
Advanced drug delivery reviews,
April 2013, 2013-Apr, 2013-04-00, 20130401, Volume:
65, Issue:
4
Journal Article
Peer reviewed
After being severely and quasi-plastically deformed, shape memory materials are able to return to their original shape at the presence of the right stimulus. After a brief presentation about the ...fundamentals, including various shape memory effects, working mechanisms, and typical shape memory materials for biomedical applications, we summarize some major applications in shaping tissue with shape memory materials. The focus is on some most recent development. Outlook is also discussed at the end of this paper.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Shape memory polymers (SMPs) are capable of changing their shapes in a pre-defined manner under a stimulus, and have gained considerable interest in the past decades. Although a number of ...stimulus-responsive SMPs have been developed, thermally-induced SMPs are still the most common. This review presents the concepts, the programming procedures, the molecular mechanism, classification, design strategies and the recent progress of thermally-induced SMPs, including dual, triple, multiple SMPs and two-way reversible SMPs (2W-SMPs) activated by direct and indirect heating method. Examples of the applications of these types of SMPs are also presented and discussed.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Research summary: U- and inverted U-shaped relationships are increasingly explored in strategy research, with 11 percent of all articles published in Strategic Management Journal (SMJ) in 2008-2012 ...investigating such quadratic relationships. Moreover, a movement towards introducing moderation to quadratic relationships has emerged. By reviewing 110 articles published in SMJ from 1980 to 2012, we identify several critical issues in theorizing and testing of these relationships for which current practice falls short. These include insufficient causal argumentation, incorrect testing, mixing up two different types of moderation, and not realizing that the curve can flip completely. For these and other issues, a guideline is provided which, when followed, may bring clarity to theoretical motivation and rigor to empirical testing. Managerial summary: Too much can be as bad as too little. Many relationships in strategic management follow an inverted U-shaped pattern, where moderate levels of a strategy lead to optimal performance. To gain deeper insights into the conventional wisdom that too much of a good thing can be harmful to performance, we discuss how such relationships can be better theorized and tested based on a review of articles exploring U-shaped relationships in Strategic Management Journal during 1980-2012. We identify several critical issues that require close attention and provide a guideline to further develop and validate this important managerial intuition.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
•An 4D printed SMC actuator was fabricated using SMA and SMP with a FDM 3D printer.•A volume fraction of SMA:SMP of 1:5 showed the largest length change of 8 mm, and the most rapid response time of 4 ...s.•The reversible actuator mechanism explains the SMC actuation via each shape memory effect.•SMC showed potential application for stents and valve controllers via 3D printing technology to achieve customized designs.
A fused deposition modeling (FDM) tool was used to fabricate a shape memory composite (SMC) that combined a shape memory alloy (SMA) with a shape memory polymer (SMP). The SMA caused a shape memory effect due to a phase change between martensite and austenite phases, in turn due to a temperature change. Also, the SMP had a shape memory effect caused by changes in the proportions of hard and soft segments near the glass transition temperature (Tg). Usually, common SMAs and SMPs are not reversible, so these materials do not go back to their original shapes once they are deformed. In this study, we fabricated 4D printing actuator via reversible SMC actuations using 3D printing technology. Nylon 12 was used as the 3D printing material in filament form. Moreover, the volume fraction of SMA to SMP was varied to find the optimum ratio for good operation cycles. A volume fraction of SMA:SMP of 1:5 showed the largest length change, of 8 mm, and the most rapid response time, of 4 s in overall dimension of 140mm×10mm×1mm (length×width×thickness).Thus, the SMC showed promising results for the application of stents and valve controllers that could be manufactured by 3D printing technology.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Display omitted
•Various advancements in shape memory polymers tuning and composites in 4D printing are presented.•The leading 4D printing techniques in 4D printing are discussed and compared based ...on their abilities and limitations.•The fundamental shape programming of prints that is observed in the literature is described and illustrated.•Recent advancements in applications and the fields benefiting the most from 4D printing are presented.
Four-dimensional (4D) printing is gaining interest in the past few years. The prototyping freedom of 3D printing coupled with the abilities of smart materials and their properties gave rise to a new field of active structures. 4D printed structures are responsive to outside stimuli, thus allowing them to change some of their characteristics. This behaviour presents a base for revolutionary advancements in the field of robotics, biomedicine, and industry. This review presents an overview of all steps involved in the 4D printing of shape memory polymers rooted in recent applications. Furthermore, this paper aims to provide researchers with a basis for design when choosing materials and printing methods that suit their application needs. The shape memory effect of 4D-printed designs, along with 4D printing techniques, and shape programming of the materials are discussed. Recent advances in 4D printing of shape memory polymers with their applications are the focus of this review, whether single or multi material, with the programming of such materials for specific actuation. In addition, this paper discusses multiple methods that can be used to control the shape memory effect of 4D-printed designs, which range from the designs of the structure, the materials used, the methods and orientations of printing, activation criteria, and others. Moreover, this paper explores the range of complexity in 4D printing, which allows for control of the actuation in terms of time, force, speed, and stages, opening a wide range of applications that could benefit from this technology.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Prestressed iron-based shape memory alloy system for retrofitting steel plates.•Development of a mechanical anchorage system for SMA-to-steel joints.•Activation of Fe-SMA strips by electrical ...heating up to 260 °C.•Recovery stress generation under different elastic restraint conditions.
This paper presents the development of an iron-based shape memory alloy (Fe-SMA) system for the strengthening of steel plates. The shape memory effect (SME), which is the tendency of a deformed SMA to return to its original shape upon heating and subsequent cooling, was used in this study for prestressing steel plates. Five steel specimens were strengthened with different configurations (single-side, double-side, activated, and non-activated) of the Fe-SMA strips. A mechanical anchorage system was developed to anchor the prestressed Fe-SMA strips to the steel substrate. The SME in the Fe-SMA strips was then activated (i.e., the strips were prestressed) by heating to a temperature of approximately 260 °C using an electrical resistive heating technique. The test results showed that the achieved recovery stress of the Fe-SMA strips (i.e., the prestressing level after activation) was approximately in the range of 350–400 MPa, which led to a maximum compressive stress of −74 MPa in the steel plate. This compressive stress can be very beneficial and significantly increase the yield and fatigue strength of the steel plates. Finally, the strengthened specimens were subjected to static loading under a displacement-controlled condition up to failure. It was shown that the proposed strengthening technique eliminates the difficulties associated with conventional prestressing (e.g., by hydraulic jacks) and also offers a fast installation procedure as it does not require any surface preparation or curing for bond application.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
We introduce 3DShape2VecSet, a novel shape representation for neural fields designed for generative diffusion models. Our shape representation can encode 3D shapes given as surface models or point ...clouds, and represents them as neural fields. The concept of neural fields has previously been combined with a global latent vector, a regular grid of latent vectors, or an irregular grid of latent vectors. Our new representation encodes neural fields on top of a set of vectors. We draw from multiple concepts, such as the radial basis function representation, and the cross attention and self-attention function, to design a learnable representation that is especially suitable for processing with transformers. Our results show improved performance in 3D shape encoding and 3D shape generative modeling tasks. We demonstrate a wide variety of generative applications: unconditioned generation, category-conditioned generation, text-conditioned generation, point-cloud completion, and image-conditioned generation. Code: https://1zb.github.io/3DShape2VecSet/.
This paper is concerned with a fundamental problem in geometric deep learning that arises in the construction of convolutional neural networks on surfaces. Due to curvature, the transport of filter ...kernels on surfaces results in a rotational ambiguity, which prevents a uniform alignment of these kernels on the surface. We propose a network architecture for surfaces that consists of vector-valued, rotation-equivariant features. The equivariance property makes it possible to locally align features, which were computed in arbitrary coordinate systems, when aggregating features in a convolution layer. The resulting network is agnostic to the choices of coordinate systems for the tangent spaces on the surface. We implement our approach for triangle meshes. Based on circular harmonic functions, we introduce convolution filters for meshes that are rotation-equivariant at the discrete level. We evaluate the resulting networks on shape correspondence and shape classifications tasks and compare their performance to other approaches.
PDF
