Shape Memory Technology Research Articles

SMST 2024: Shape Memory and Superelastic Technologies Conference and Exposition

SMST 2024: Shape Memory and Superelastic Technologies Conference and Exposition

NIR-induced photothermal-responsive shape memory polyurethane for versatile smart material applications.

Stimuli responsiveness has been an attractive feature of smart material design, allowing the chemical and physical properties of the materials to change in response to small environmental variations. The versatile shape memory polyurethane (SMPU) has been advanced into thermally-responsive SMPU, enabling its use in neurovascular stents, smart fibers for compression garments, and thermal-responsive components for aircraft and aerospace structures. While thermally-induced SMPU materials exhibit excellent shape recovery and fixity, they encounter limitations such as long response times, energy-intensive heating processes, and potential damage to heat-sensitive components, hindering their wide application. Thus, SMPU has further advanced into a photothermal-responsive material by incorporating photothermal agents into the polymer matrix, offering faster response times, compatibility with heat-sensitive materials, and enhanced mechanical properties, expanding the versatility and applicability of shape memory technology. This review focuses on the classes of NIR-induced photothermal agent used in SMPU systems, their synthesis methods, and photothermal-responsive mechanism under NIR-light, which offers a dual responsiveness to the host SMPU. The advantages and limitations of NIR-induced photothermal SMPU are reviewed, and challenges in their development are discussed.

Advances in Graphene‐Reinforced Polyurethane Nanocomposites: An Advanced Shape Memory Material

AbstractThe expansion of nanofiller‐based polymers has been rapidly increasing in contemporary society due to their wide range of applications owing to their diverse physicochemical characteristics. This review focuses on a polymer nanocomposite in which graphene is incorporated as a nanofiller and polyurethane is used as a polymer. As polyurethane is well known for its shape memory behaviour and the reinforcement of graphene‐based nanomaterial sparks the physicochemical properties of the fabricated nanocomposites which makes it more adaptable and useful for a wide array of applications. The review provides insights into the recent synthesis approaches to the fabrication of graphene‐based polyurethane nanocomposites. Further, efforts were also made to cover the recent studies done on the use of these nanocomposites as an advanced shape memory material. Rather than merely serving as descriptive content, this article is intended to serve as a comprehensive guide for researchers seeking to harness the potential of graphene‐based nanomaterial reinforcement in polyurethane for high‐performance applications. By providing a detailed overview of the latest research in this domain, the review aims to propel the development of novel and sophisticated materials, unlocking new horizons in smart shape memory technologies.

Thermal Stability of Cu-Al-Ni Shape Memory Alloy Thin Films Obtained by Nanometer Multilayer Deposition.

Cu-Al-Ni is a high-temperature shape memory alloy (HTSMA) with exceptional thermomechanical properties, making it an ideal active material for engineering new technologies able to operate at temperatures up to 200 °C. Recent studies revealed that these alloys exhibit a robust superelastic behavior at the nanometer scale, making them excellent candidates for developing a new generation of micro-/nano-electromechanical systems (MEMS/NEMS). The very large-scale integration (VLSI) technologies used in microelectronics are based on thin films. In the present work, 1 μm thickness thin films of 84.1Cu-12.4 Al-3.5Ni (wt.%) were obtained by solid-state diffusion from a multilayer system deposited on SiNx (200 nm)/Si substrates by e-beam evaporation. With the aim of evaluating the thermal stability of such HTSMA thin films, heating experiments were performed in situ inside the transmission electron microscope to identify the temperature at which the material was decomposed by precipitation. Their microstructure, compositional analysis, and phase identification were characterized by scanning and transmission electron microscopy equipped with energy dispersive X-ray spectrometers. The nucleation and growth of two stable phases, Cu-Al-rich alpha phase and Ni-Al-rich intermetallic, were identified during in situ heating TEM experiments between 280 and 450 °C. These findings show that the used production method produces an HTSMA with high thermal stability and paves the road for developing high-temperature MEMS/NEMS using shape memory and superelastic technologies.

Selected Articles from SMST 2022: The International Conference on Shape Memory and Superelastic Technologies (SMST)

Selected Articles from SMST 2022: The International Conference on Shape Memory and Superelastic Technologies (SMST)

Preface

It is highly delighted to introduce the proceedings dedicated to the 2020 International Conference on Applied Mechanics and Mechanical Engineering (ICAMME 2020), which was successfully held on Sep. 25-27, 2020 in Hulun Buir, China, and hosted by AEIC Academic Exchange Information Centre. ICAMME 2020 is to bring together innovative academics and industrial experts in the field of applied mechanics, mechanical engineering, electrical and automation engineering to a common forum. The goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working all around the world. An ideal platform for seeking global partners had been established.About 60 participants from academic, high-education institutes and other organizations took part in the Conference. The conference model was divided into two sessions, including oral presentations and keynote speeches. In the first part, some scholars, whose submissions were selected as the excellent papers, were given 15 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches.We were very honored to have Prof. Simon X. Yang from University of Guelph, Canada and Prof. Wei Min Huang from Nanyang Technological University, Singapore as our Chairman. In the keynote presentation part, we invited three professors as our keynote speakers. The first keynote speaker, Prof. Simon X. Yang, our beloved Chairman, shared a speech: Bioinspired Intelligent Approaches to Various Mechatronic Systems. In this talk, he started with a very brief introduction to biologically inspired computation and learning, and some bio-inspired computational techniques. After that, he presented several practical applications in engineering systems. The second keynote speaker, Prof. Wei Min Huang from Nanyang Technological University, Singapore. He delivered a speech: Morphing Via Shape Memory Materials and Technology. In this talk, he presented a brief introduction of various shape memory phenomena firstly. After that, he showed a range of morphing applications in aero/space missions, biomedical devices etc. utilizing shape memory alloy and shape memory polymer. Our finale keynote speaker, Prof. Junxi Bi, from Inner Mongolia University of Technology, China shared a speech on Reliability Analysis and Optimization of Key Parts of Low Pressure Cantilever Casting Machine. The proceedings present a selection of high-quality papers submitted to the conference by researchers from universities, research institutes, and industry. All papers were subjected to peer-review by conference committee members and international reviewers. The papers were selected based on their quality and their relevance to the conference. The proceedings present recent advances in the fields of Applied Mechanics and Engineering Mechanics, Mechanical Engineering, Materials Science, Electrical and Automation Engineering and Other related research.I would like to express special gratitude to members of the conference committee and organizers of the conference. I would also like to thank the reviewers for their valuable time and advice which helped in improving the quality of the papers selected for presentation at the conference and for publication in the proceedings. Finally, I want to thank the authors, the members of the organizing committee, the reviewers, the chairpersons, sponsors, and all other conference participants for their support of ICAMME 2020.The Organizing Committee of ICAMME 2020List of Committee member is available in this pdf.

On the Importance of Structural and Functional Fatigue in Shape Memory Technology

The present work provides a brief overview on structural and functional fatigue in shape memory alloys (SMAs). Both degenerative processes are of utmost technological importance because they limit service lives of shape memory components. While our fundamental understanding of these two phenomena has improved during the last two decades, there are still fields which require scientific attention. NiTi SMAs are prone to the formation of small cracks, which nucleate and grow in the early stages of structural fatigue. It is important to find out how these micro-cracks evolve into engineering macro-cracks, which can be accounted for by conventional crack growth laws. The present work provides examples for the complexity of short crack growth in pseudoelastic SMAs. The importance of functional fatigue has also been highlighted. Functional fatigue is related to the degeneration of specific functional characteristics, such as actuator stroke, recoverable strain, plateau stresses, hysteresis width, or transformation temperatures. It is caused by the accumulation of transformation-induced defects in the microstructure. The functional stability of SMAs can be improved by (1) making phase transformations processes smoother and (2) by improving the material’s resistance to irreversible processes like dislocation plasticity. Areas in need of further research are discussed.

Preface

The 2019 2nd International Conference on Mechanical, Electrical and Material Application (MEMA 2019), was successfully held on October 25-27, 2019 in Xi’an, China. With the purpose of promoting research and developmental activities in Mechanical, Electrical and Material Application, MEMA 2019 brought together innovative academics and industrial experts in this field to share and discuss the cutting-edge scientific acknowledge and development.It’s a great honor to invite A. Prof. Yung-Yao Chen from National Taipei University of Technology, Taiwan, China, A. Prof. Ricky Lee from National Taiwan University of Science and Technology, Taiwan, China, Prof. Shi-Chang Tsen from National Yunlin University of Science and Technology, Taiwan, China, and A. Prof. Mochamad Chalid from University of Indonesia, Indonesia as our Conference Chairman, and our committee is composed of over 40 professors and scholars representing different advanced universities and institutions from home and abroad. We have five distinguished keynote speakers from Malaysia, Indonesia, Singapore, and China, who have given marvelous speeches on Wireless Communication, Polymer Technology, Shape memory technology, Electrical engineering, and Microwave Dielectric Materials in the conference.We are pleased to introduce the Proceedings of MEMA 2019 which contain a selection of papers from contributed presentation in the conference. The Proceedings features recent result and contemporary research in Mechanical Engineering, Electrical Engineering, Material Application, and other related topics. All the papers have been through rigorous review and process to meet the requirements of International publication standard.On behalf of the committee, we would like to express our gratitude to the distinguished speakers who have come to share their valuable findings and knowledge, to the chairman and all participants, who contributed a lot and made this conference a great success. We would also like to thank the contributors for submitting their papers and patiently revised them according to the suggestions of the designated reviewers.Finally, we hope that all the articles in this conference can provide valuable summary and reference for researchers in this field.The Organizing Committee of MEMA 2019List of Committee member is available in this pdf.

Selected Articles from SMST 2019: The International Conference on Shape Memory and Superelastic Technologies (SMST)

Selected Articles from SMST 2019: The International Conference on Shape Memory and Superelastic Technologies (SMST)

Shape memory behaviour of gelatin – alginate interpenetrating network hydrogel

Gelatin – alginate interpenetrating network hydrogel was prepared. Glutaraldehyde was used to crosslink gelatin to form permanent netpoints for fixing the original shape of the hydrogel. Calcium ion was used to create coordination interaction with sodium alginate molecular chains to form temporary cross-links. EDTA solution was used as a response solution. After 120 min of observation, the shape recovery rate of the hydrogel reached 84.4%. It showed a good ion-responsive shape memory behaviour. This study provides an experimental basis for enrichment of shape memory technology at room temperature.

Deformation twinning in martensite affecting functional behavior of NiTi shape memory alloys

Functional stress-strain–temperature responses of superelastic NiTi wire in purposely designed thermomechanical tests in tension were evaluated and lattice defects created by the tensile deformation were analyzed by transmission electron microscopy in this work with the aim to investigate potential involvement of deformation twinning in oriented martensite in thermomechanical loads and its consequences for NiTi superelastic and shape memory technologies. It was found that: i) the deformation twinning in oriented martensite taking place upon tensile loading beyond the yield point gives rise to large and stable two way shape memory effect, ii) its activity during the reverse transformation under high stress enables shape setting of superelastic NiTi wires and iii) its activity during tensile superelastic cycling brings about unrecoverable strains and causes functional fatigue.

Engineering design tools for shape memory alloy actuators: CASMART collaborative best practices and case studies

One of the primary goals of the Consortium for the Advancement of Shape Memory Alloy Research and Technology is to enable the design of revolutionary applications based on shape memory alloy technology. To advance this goal and reduce the development time and required experience for the fabrication of shape memory alloy actuation systems, several modeling tools were developed for common actuator types and are discussed along with case studies, which highlight their capabilities and limitations. Shape memory alloys have many potential applications as reliable, lightweight, solid-state actuators given their ability to sustain high stresses and recover large deformations. In this article, modeling frameworks are developed for three common actuator designs: wires, lightweight, low-profile, and easily implemented; coiled springs, offering actuation strokes upward of 200% at reduced mechanical loads; and torque tubes, which can provide large actuation torques in small volumes and repeatable low-load actuation. Although the design and integration of a shape memory alloy–based actuation system requires application- and environment-specific engineering considerations, common modeling tools can significantly reduce the investment required for actuation system development and provide valuable engineering insight. This analysis presents a collection of Consortium for the Advancement of Shape Memory Alloy Research and Technology collaborative best practices to allow readers to utilize the available design tools and understand their modeling principles.

SMST 2019: Shape Memory and Superelastic Technology Conference and Exposition

SMST 2019: Shape Memory and Superelastic Technology Conference and Exposition

Photo-cross-linking of Anthracene as a Versatile Strategy to Design Shape Memory Polymers

Shape memory polymers (SMPs) are an important class of smart materials in polymer science, and have been attracting academic and industrial interests for many years. In the past decades, the fundamental aspects of SMPs have been comprehensively studied, and with the increasing demands for practical applications, researches on SMPs have been focused on molecular structure design, advanced design and manufacturing, where the photo-cross-linking of anthracene can benefit a lot. From the view of molecular structure design, the photo-cross-links of anthracene can versatilely work as either netpoint or molecular switch, depending on the specific circumstance of a SMP. In the aspect of manufacturing chemically cross-linked SMPs, the photo-cross-linking of anthracene shows great potential in photo-assisted 3D/4D printing via an approach of “Pre-Shaping and Post-curing”. Besides, the unique fluorescent property of anthracene enables photo-imaging based on localized photo-cross-linking, and this benefits information storage. This paper mainly presents our recent research process in using photo-cross-linking of anthracene to design various SMPs, including chemically triple SMPs, two-way SMPs, light-induced SMPs and multi-stimuli-responsive SMPs from the molecular structure level, and new application as a high-security information storage medium enabled by the combination of photo-imaging and shape memory technology (SMT).

Recovery, Recrystallization, and Grain-Growth

This is a brief review of the important phenomena of recovery, recrystallization as well as grain-growth. The three mentioned phenomena are the mechanisms by which metals and alloys fix the structural damage introduced by the mechanical deformation and, as a consequence, in the physical and mechanical properties. These rehabilitation mechanisms are thermally activated. For this process, the materials have to be heated and any such heat-treatment is meant to reduce deformation-induced break is termed annealing. Other or different heat-treatments lead to recovery and recrystallization. It is rather strange that, though these phenomena are extremely important in metallurgical science and engineering, not so much work has been done as that in corrosion and shape memory technologies. An attempt has been made here to summarize all important aspects of these phenomena for the benefits of students of metallurgy, chemistry and solid state physics.

Integrating shape-memory technology and photo-imaging on a polymer platform for a high-security information storage medium

The high-security of an information storage medium is enabled by the integration of shape-memory technology and photo-imaging on an anthracene-containing polymer platform.

Polymer–Polymer Modification when Obtaining Epoxy/Allyl Polymers with a Shape-Memory Effect

Specific features of polymer–polymer modification of epoxy and allyl homopolymers carried out to obtain compounds combining the advantages of each of these polymers were analyzed. Studies performed using IR spectroscopy, differential-scanning calorimetry, and NMR spectroscopy allowed it to be determined that a range of structures (from systems without a pronounced interpenetrating network to limited reciprocal ones) is formed due to the simultaneous and continuous occurrence of two reactions of oligomer hardening that take place in independent directions. The performed physical-mechanical tests allowed one to determine the optimal composite of polymer composites characterized by a level of deformation behavior needed for their realization via shape-memory effect technology.

Sustainability of civil infrastructure using shape memory technology

The last few decades have clearly demonstrated the vulnerability of our civil infrastructure systems to problems like aging, natural, and man-made hazards including earthquakes, hurricanes, blasts, etc. The conventional materials such as steel and concrete have proven to be limited in terms of their ability to withstand the extreme demands imposed on them by modern societies. The limitations in currently used construction materials combined with the consistently growing population worldwide present new challenges and demands for researchers in the field of structural engineering. Hence, there is an urgent need for new materials that are capable of extending the service life of structures with minimal or no need for maintenance or repairs against natural and man-made hazards. Shape memory alloy (SMA) is a class of “Smart Materials” that have recently emerged as potential construction material with unique thermomechanical properties, namely shape memory effect and superelasticity. Two applications of SMAs in civil structures are discussed in this paper. The first application involves the use of SMA in performing seismic rehabilitation of RC bridge columns that lack flexural ductility. In this application, SMA is used in the form of thermally prestressed spirals that can apply large active confinement pressure to the columns at their plastic hinge regions to improve their flexural ductility. The experimental results of large scale shake table tests performed on two RC columns, one of which is retrofitted with SMA are discussed. The results demonstrate the great ability of SMA spirals in mitigating the damage even under strong levels of ground shaking. The second application focuses on utilizing superelastic SMA fibers as reinforcement for polymeric composite bars. The newly developed composite material is named SMA–Fiber Reinforced Polymer (SMA–FRP), and is studied as seismic reinforcing bars for moment resisting concrete frames. The results of nonlinear time history analysis prove that using SMA–FRP bars at the plastic hinge regions of the frames helps significantly in limiting the residual drifts and enhancing the energy dissipation of the frames.

Influence of clinical use on physical-structural surface properties and electrochemical potential of NiTi endodontic instruments.

To investigate the surface morphology and electrochemical potential of superelastic (SE), M-Wire (MW) and shape memory technology (SMT) NiTi instruments before and after single clinical use invivo. A total of 60 ProTaper Universal F2 (PTU-SE), ProTaper Next X2 (PTN-MW), Typhoon (TYP), Hyflex (HF) and Vortex Blue (VB), the last three SMT, and size 25, .06 taper (n=6 of each type) files were examined. Scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS) and electrochemical potential analysis were employed before and after clinical use. Statistical analysis was performed with one-way analysis of variance and Bonferroni's post hoc test. Significance was determined at the 95% confidence level for both tests. SEM observations of new instruments indicated the presence of marks left by the machining process during manufacturing and EDS revealed the existence of an oxide coating on shape memory instruments. After clinical use, the five types were associated with propagation of transverse cracks 3mm from the tip. The surface oxide layer of TYP, HF and VB instruments had microcracks in multiple directions, whilst TYP and HF had fragmentation in chip form of the oxide layer. EDS analysis demonstrated a significant reduction of the oxide layer in shape memory instruments, except for VB. Electrochemical potentials were higher for shape memory instruments than for M-Wire and superelastic NiTi instruments, respectively (P<0.05). It appears that shape memory technology NiTi instruments have a dysfunctional oxide layer after clinical use. Additionally, they featured higher electrochemical potential relative to NiTi instruments manufactured from M-Wire, and conventional superelastic NiTi alloy.

Design and Characterization of a Continuous Rotary Minimotor Based on Shape-Memory Wires and Overrunning Clutches1

An attractive but little explored field of application of the shape-memory technology is the area of rotary actuators, in particular for generating endless motion. This paper presents a miniature rotary motor based on shape-memory alloy (SMA) wires and overrunning clutches, which produces high output torque and unlimited rotation. The concept features an SMA wire tightly wound around a low-friction cylindrical drum to convert wire strains into large rotations within a compact package. The seesaw motion of the drum ensuing from repeated contraction–elongation cycles of the wire is converted into unidirectional motion of the output shaft by an overrunning clutch fitted between drum and shaft. Following a design process developed in a former paper, a six-stage prototype with size envelope of 48 × 22 × 30 mm is built and tested. Diverse supply strategies are implemented to optimize either the output torque or the speed regularity of the motor with the following results: maximum torque = 20 Nmm; specific torque = 6.31 × 10−4 Nmm/mm3; rotation per module = 15 deg/cycle; and free continuous speed = 4.4 rpm.