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The purpose of this paper is to examine the underlying mechanism and physico‐chemical requirements of chemo‐responsive shape change/memory polymers and to explore the future trend of development and potential applications.

Working mechanism in chemo‐responsive shape change/memory polymers is firstly identified. And then the physico‐chemical requirements for the representative polymers are characterized.

The different working mechanisms, fundamentals, physico‐chemical requirements and theoretical origins have been discussed. Current research and development on the fabrication strategies of chemo‐responsive shape change/memory polymers have been summarised. The future trend and potential applications have been explored and estimated.

This review examines physico‐chemical requirements and theoretical origins necessary to achieve chemo‐responsiveness, and then discusses recent developments and future trends.

Shape change/memory polymers can be used in the broad field of bio‐ and/or medicine.

Breakthroughs and rapid development of chemo‐responsive shape change/memory polymers will significantly improve the research and development of smart materials, structures and systems.

The purpose of this paper is to provide a review of recent systematic and comprehensive advancement in electrospun polymer fiber and their composites with shape memory property.

The nanofiber manufacture technique is initially reviewed. Then, the influence of electrospinning parameters and actuation method has been discussed. Finally, the study concludes with a brief review of recent development in potential applications.

Shape memory polymer (SMP) nanofibers are a type of smart materials which can change shape under external stimuli (e.g. temperature, electricity, magnetism, solvent). In general, such SMP nanofibers could be easily fabricated by mature electrospinning technique. The nanofiber morphology is mainly affected by the electrospinning parameters, including applied voltage, tip-to-collector distance, viscosity of solution, humidity and molecular weight. For actuation method, most SMP nanofibers and their composites can change their shapes in response to heat, magnetic field or solvent, while few can be driven by electricity. Compared with the block SMPs, electrospun SMP nanofibers’ mat with porosity and low mechanical property have a wide potential application field including tissue engineering, drug delivery, filtration, catalysis.

This paper provides a detailed review of shape memory nanofibers: fabrication, actuation and potential application, in the near future.

This paper aims to provide a review of four-dimensional (4D) printing using fused-deposition modeling (FDM). 4D printing is an emerging innovation in (three-dimensional) 3D printing that encompasses active materials in the printing process to create not only a 3D object but also a 3D object that can perform an active function. FDM is the most accessible form of 3D printing. By providing a review of 4D printing with FDM, this paper has the potential in educating the many FDM 3D printers in an additional capability with 4D printing.

This is a review paper. The approach was to search for and review peer-reviewed papers and works concerning 4D printing using FDM. With this discussion of the shape memory effect, shape memory polymers and FDM were also made.

4D printing has become a burgeoning area in addivitive manufacturing research with many papers being produced within the past 3-5 years. This is especially true for 4D printing using FDM. The key findings from this review show the materials and material composites used for 4D printing with FDM and the limitations with 4D printing with FDM.

Limitations to this paper are with the availability of papers for review. 4D printing is an emerging area of additive manufacturing research. While FDM is a predominant method of 3D printing, it is not a predominant method for 4D printing. This is because of the limitations of FDM, which can only print with thermoplastics. With the popularity of FDM and the emergence of 4D printing, however, this review paper will provide key resources for reference for users that may be interested in 4D printing and have access to a FDM printer.

Practically, FDM is the most popular method for 3D printing. Review of 4D printing using FDM will provide a necessary resource for FDM 3D printing users and researchers with a potential avenue for design, printing, training and actuation of active parts and mechanisms.

Continuing with the popularity of FDM among 3D printing methods, a review paper like this can provide an initial and simple step into 4D printing for researchers. From continued research, the potential to engage general audiences becomes more likely, especially a general audience that has FDM printers. An increase in 4D printing could potentially lead to more designs and applications of 4D printed devices in impactful fields, such as biomedical, aerospace and sustainable engineering. Overall, the change and inclusion of technology from 4D printing could have a potential social impact that encourages the design and manufacture of such devices and the treatment of said devices to the public.

There are other 4D printing review papers available, but this paper is the only one that focuses specifically on FDM. Other review papers provide brief commentary on the different processes of 4D printing including FDM. With the specialization of 4D printing using FDM, a more in-depth commentary results in this paper. This will provide many FDM 3D printing users with additional knowledge that can spur more creative research in 4D printing. Further, this paper can provide the impetus for the practical use of 4D printing in more general and educational settings.

This paper aims to create and to study multifunctional shape memory polymer (SMP) composites having temperature-sensing and actuating capabilities by embedding thermochromic particles within the polymer matrix.

The multifunctional materials were fabricated following a process consisting of blending (of the thermochromic particles and the SMP at various ratios), mixing, degasing, moulding and thermal curing, prepared by incorporating thermochromic particles within the polymer. The effect of the thermochromic particles on the thermomechanical properties and thermally responsive shape memory effect of the resulting multifunction SMP composites were characterised and interpreted.

It was found that exposure of the composites to temperatures above 70°C led to a pronounced change of their colour that was recorded by the thermal and electrical actuation approaches and was reproducibly reversible. It was also found that the colour of the composites was independent of the mechanical state of the SMP. Such effects enabled monitoring of the onset of the set/release temperature of the SMP matrix. Furthermore, the combination of thermochromic additive and the SMP resulted in significantly improved thermomechanical strength, absorption of infrared radiation and the temperature distribution of the SMP composites.

The temperature-sensing and actuating capabilities of the polymeric shape memory composites developed through this study will help to extend the field of potential applications of such composites to fields including sensors, actuators, security labels and information dissemination, where colour indication is an advantageous feature.

The SMP composites capable of temperature sensing and actuating are novel.

This article aims to present a systematic and up-to-date account of carbon-based reinforcements, including carbon nanotube (CNT), carbon nanofibre (CNF), carbon black (CB), carbon fibre (CF) and grapheme, in shape-memory polymer (SMP) for electrical actuation.

Studies exploring carbon-based reinforcement in SMP composites for electrically conductive performance and Joule heating triggered shape recovery have been included, especially for the principle design, characterisation and shape recovery behaviour, making the article a comprehensive account of the systemic progress in SMP composite incorporating conductive carbon reinforcement.

SMPs are fascinating materials and have attracted great academic and industrial attention owing to their significant macroscopic shape deformation in the presence of an appropriate stimulus. The working mechanisms, the physico requirements and the theoretical origins of the different types of carbon-based reinforcement SMP composites have been discussed. Current research and development on the fabrication strategies of carbon-based reinforcement SMP composites have been summarised.

A systematic review is to evaluate carbon-based reinforcements in SMPs for electrical actuation and discuss recent developments and future applications.

Carbon-based reinforcements in SMPs can be used as smart deployable space structure in the broad field of aerospace technologies.

To reveal the research and development of utilising CNT, CNF, CB, CF and grapheme to achieve shape recovery of SMP composites through electrically resistive heating, which will significantly benefit the research and development of smart materials and systems.

This study aims to present that the chemo-responsive shape recovery of thermoplastic polyurethane (TPU) is tunable by solvents with different solubility parameters, and it is generic for chemo-responsive shape-memory polymer and its composites.

Two kinds of commercial TPU samples with different thicknesses were prepared by panel vulcanizer and injection molding (an industrial manner) to investigate their chemo-responsive shape memory properties in acetic ether and acetone.

Results showed that all of TPU films with different thicknesses can fully recover their original shapes weather they recover in acetic ether or acetone. But the recovery time of TPU films in acetone is greatly reduced, especially for the twisting samples. The residual strains of recovery TPU samples after extension reduce obviously.

The great decrement of recovery time is related to two factors. One is due to the bigger solubility parameter of acetone with higher dipole moment compared with those of acetic ether, and the other is the remained internal stress of TPU films after preparation. The internal stress is identified to have an effect on the shape-memory properties by comparing the recovery process of samples with/without annealing. The reduced residual strains of recovery TPU samples after extension is due to the increasing mobility of polymer segments after molecules of acetic ether penetrates into the polymeric chains.

This is a universal strategy to control the recovery process of shape-memory materials or composites. The underlying mechanism is generic and should be applicable to chemo-responsive shape-memory polymers or their composites.

The purpose of this paper is a study aimed at overcoming the interface issue between nanopaper and polymer matrix in shape-memory polymer (SMP) composite laminates caused by their large dissimilarity in electrical/thermal conductive properties. The study attempted to develop an effective approach to fabricate free-standing carbon nanofibre (CNF) assembly in octagon shape formation. The structure design and thermal conductive performance of the resulting octagon-shaped CNF assembly were optimised and simulated.

The CNF nanopaper was prepared based on a filtration method. The SMP nanocomposites were fabricated by incorporating these CNF assemblies with epoxy-based SMP resin by a resin-transfer modelling technique. Thermal conductivity of the octagon-shaped CNF assembly was simulated using the ANSYS FLUENT software for structure design and optimisation. The effect of the octagon-shaped CNF on the thermomechanical properties and thermally responsive shape-memory effect of the resulting SMP nanocomposites were characterised and interpreted.

The CNF template incorporated with SMP to achieve Joule heating triggered shape recovery at a low electric voltage of 3-10 V, due to which the electrical resistivity of SMP nanocomposites was significantly improved and lowered to 0.20 O·cm by the CNF template. It was found that the octagon CNF template with 2 mm width of skeleton presented a highest thermally conductive performance to transfer resistive heat to the SMP matrix.

A simple way for fabricating electro-activated SMP nanocomposites has been developed by using an octagon CNF template. Low electrical voltage actuation in SMP has been achieved.

The fabricated CNF template, the structure design and analysis of dynamic thermomechanical properties of SMP are novel.

Epoxy (EP) and polye-caprolactone (PCL) are typical dual-shape memory polymer (DSMP). To get excellent triple-shape memory effect (TSME) polymer composites which are made from EP and PCL. Miscible PCL/EP blend composites have been investigated and compared to the TSMEs with electrospun PCL microfiber membranes/EP composites. Clay montmorillonite (MMT)-modified electrospun PCL microfiber membranes were prepared to improve the shape memory fixities of electrospun PCL microfiber membranes/EP composites.

The morphologies of electrospun PCL microfiber membranes and the cross section of PCL/EP composites were studied using a field emission scanning electron microscope (FE-SEM), and the existence of MMT was confirmed by a transmission electron microscope. Thermal mechanical properties were observed by a differential scanning calorimeter (DSC) and a dynamic thermomechanical analysis machine, and the TSMEs were also determined through dynamic mechanical analysis.

Results indicate that the TSMEs of electrospun PCL microfiber membranes/EP composites were excellent, whereas the TSMEs of PCL/EP blend composites were poor. The TSMEs of PCL electrospun microfiber membranes/EP composites significantly improved with the addition of the PCL electrospun microfiber modified with moderate MMT.

Adding a moderate content of MMT into the electrospun PCL fibers, could improve the TSME of the PCL fiber membranes/EP composites. This study was to create a simple and effective method that can be applied to improve the performance of other SMP.

A novel triple-shape memory composite were made from dual-shape memory EP and electrospun PCL fiber membranes.

This paper aims to study the synergistic effect of self-assembled carboxylic acid-functionalised carbon nanotube (CNT) and nafion/silica nanofibre nanopaper on the electro-activated shape memory effect (SME) and shape recovery behaviour of shape memory polymer (SMP) nanocomposite.

Carboxylic acid-functionalised CNT and nafion/silica nanofibre are first self-assembled onto carbon fibre by means of deposition and electrospinning approaches, respectively, to form functionally graded nanopaper. The combination of carbon fibre and CNT is introduced to enable the actuation of the SME in SMP by means of Joule heating at a low electric voltage of 3.0-5.0 V.

Nafion/silica nanofibre is used to improve the shape recovery behaviour and performance of the SMP for enhanced heat transfer and electrical actuation effectiveness. Low electrical voltage actuation and high electrical actuation effectiveness of 32.5 per cent in SMP has been achieved.

A simple way for fabricating electro-activated SMP nanocomposites has been developed by using functionally graded CNT and nafion/silica nanofibre nanopaper.

The outcome of this study will help to fabricate the SMP composite with high electrical actuation effectiveness under low electrical voltage actuation.

This paper aims to provide an insight into recent developments in adhesive technology.

Following a brief introduction, this paper discusses recent developments in biomimetic adhesives, the use of nanomaterials and “smart” adhesive technology.

Biomimetic dry adhesive technology has advanced very rapidly in recent years and techniques to mass‐produce these materials are now under development. The use of nanomaterials is being investigated widely and recent research suggests that adhesives with enhanced mechanical, thermal and electrical properties will emerge. Smart adhesives, such as switchable types which can be triggered to bond and de‐bond in response to physical or chemical stimuli are under development and some are already available commercially. These will contribute to product disassembly and recycling.

This paper provides a review of recent R&D into three fields of adhesive technology that are presently attracting strong interest.