Switching Segments Research Articles

M3D‐DPWM strategy for three‐phase four‐leg inverter with higher harmonic suppression capability

AbstractThree‐phase four‐leg inverters are widely used in power systems due to their inherent ability to handle unbalanced loads. However, with conventional 3D space vector pulse width modulation (3D‐SVPWM), high harmonics of large amplitude exist in the output voltage around the switching frequency and its integer multiples leading to noise in the load motor and limiting the application range of the inverter system. The passband amplification of conventional sinusoidal filters and their cutoff frequency vary with the load, so it is particularly important to investigate the regulation strategy with harmonic suppression. In this study, an improved 3D discontinuous pulse width modulation (M3D‐DPWM) strategy is proposed based on 3D‐SVPWM. By reducing the conventional 3D‐SVPWM switching segments and changing the vector synthesis sequence of the last half switching cycle, the output phase voltage period is reduced to half of the original one, which achieves the purpose of suppressing the output voltage at the switching frequency and its odd multiple high harmonics without changing the fundamental characteristics and adding additional circuits. In contrast, the conventional 3D‐SVPWM switching frequency is increased to 20 kHz to achieve similar performance. Finally, the effectiveness of the proposed strategy is verified by simulation and experiment.

Dynamic reversible mechanism of phenol-carbamate bonds and their potential for the development of thermo-healing, recyclable and high-performance epoxy thermosets

In this paper, a series of small monomers were synthesized to explore the dynamic reversible properties of phenol-carbamate bonds (PCBs), and the bimolecular exchange mechanism of PCBs was verified. Based on this mechanism, a novel thermo-healing recyclable epoxy resin with high mechanical performance and shape memory function was successfully developed. Meanwhile, the number of reversible phenol-carbamate bonds in this system was increased by molecular structure design, which increased the chance of reversible cleavage and recombination of the dynamic covalent bonds. Compared with our previous work, the thermo-healing efficiency of the epoxy thermosets was greatly increased, and the target polymer achieved an excellent balance between high thermo-healing efficiency and good mechanical performance. Further post-treatment experiments show that the cured epoxy resin can also be well recycled by solvent degradation or hot-pressing process. What's more, a novel carbon fiber (CF) reinforced polymer composite material was synthesized by taking that prepared epoxy thermoset as a matrix, which greatly improve the mechanical properties of epoxy resin, and the CF cloths can be recycled when the epoxy resin is removed by chemical degradation. In addition, due to the existence of reversible crystallizable switching segments in the epoxy resin system, when the temperature is above its Tg, it can be triggered by thermal energy, so that the film can rapidly recover from the temporary shape to the permanent shape. This study also provides a new direction for the development of novel multifunctional intelligent polymers.

Evaluation of the Shape Memory Effect of Random and Aligned Electrospun Polyurethane Mats with Different Fibers Diameter.

Fibrous shape memory scaffolds composed of thermoplastic polyurethane based on a mixture of polycaprolactone diols were fabricated. The effect of the fiber diameter and arrangement- random (rPU) or aligned (aPU), on crystallinity, mechanical properties, and shape memory was analyzed. The diameters of the fibers were controlled by changing the concentration of polyurethane (PU) solutions in the range of 5% to 16% and fibers alignment by utilization of different collectors. The chemical structure was confirmed by Fourier Transformed Infrared spectroscopy (FTIR), crystallinity was evaluated based on differential scanning calorimetry (DSC,) and mechanical properties were measured by the tensile test. Additionally, shape memory programming was performed using a dynamic mechanical analyzer (DMA), and shape recovery was evaluated in the air and in the water environment. DSC results showed that the electrospinning process did not change the crystallinity or melting temperature of synthesized thermoplastic polyurethanes. The melting temperature of the crystalline switching segments was around 26-27 °C, and the crystalline phase of hard segments was around 130 °C. Shape memory properties were analyzed in the contest of the fiber diameter and alignment of the fibers, while changes in the fibers' diameters from 360 nm to 1760 nm did not result in significant changes in shape recovery coefficient (Rr) especially evaluated in the air. The longitudinal fiber alignment enhanced mechanical and shape recovery to up to 96% for aPU, with the highest fiber diameter when evaluated in water.

4D Printing of Single-Network Shape Memory Polyurethanes with Two-Way Actuation Properties

Two-way shape memory polymers (SMPs) have received much attention due to their ability to enable stimuli-responsive reversible structures without requiring repeated human intervention, which may be useful for application in many fields where multiple actuation cycles are desired. However, many layered or composite SMP systems are not integrated structures and suffer from several disadvantages, such as poor interlayer adhesion with limited actuation repeatability. In addition, two-way SMPs are limited by their manufacturing method to producing user-defined, complex, high-precision devices and parts. In this work, we developed a 3D-printable resin comprising two polyurethane-based oligomers with distinctly different transition temperatures─polypentadecalactone diacrylate (PPDLDA) and polycaprolactone diacrylate (PCLDA)─together with other monomers to fabricate single-network two-way shape memory smart materials by digital light projection 3D printing. The chemical, mechanical, and thermal properties of printed products can be easily tuned by facile manipulation of monomer and oligomer compositions. The PCLDA and PPDLDA switching segments were found to exhibit high mean shape fixity ratios (Rf) of >97% and high shape recovery ratios (Rr) of >89%. The strategy for achieving 3D-printable single-network two-way SMPs presented herein holds promise for applications in soft robotics, medicine, and so forth.

Shape‐Memory Semicrystalline Polymeric Materials Based on Various Rubbers

AbstractA simple strategy is presented for the fabrication of shape‐memory materials containing commercial rubbers including natural rubber, cis‐polybutadiene, and styrene‐butadiene rubber. Dissolution of the rubbers in n‐octadecyl acrylate (C18A) monomer followed by UV polymerization at 30 °C leads to the formation of interconnected interpenetrating polymer networks (c‐IPNs) possessing crystalline domains. They exhibit melting (Tm) and crystallization temperatures (Tcry) between 45–50 and 35–40 °C, respectively, that can be tuned by the amount and the type of the rubbers. All c‐IPNs exhibit a significant temperature sensitivity in their viscoelastic and mechanical properties when the temperature is changed between below and above Tm and Tcry. The morphology of c‐IPNs consists of amorphous nanoparticles of around 64 nm diameter composed of interconnected noncrystalline poly(C18A) (PC18A) and rubber networks, surrounded by crystalline PC18A segments. c‐IPNs exhibit tunable mechanical properties, for example, their Young's modulus and toughness can be varied between 8.3–73 MPa, and 1.9–23 MJ·m−3, respectively, by changing the amount and type of the rubber. Because of the coexistence of chemical cross‐links and crystalline domains acting as the netpoints and switching segments, respectively, c‐IPNs exhibit an efficient shape‐memory function as demonstrated by their potential application as a robotic gripper.

Blood Pressure Estimation From Korotkoff Sound Signals Using an End-to-End Deep-Learning-Based Algorithm

While measurement of blood pressure (BP) is now widely carried out by automated non-invasive BP (NIBP) monitoring devices, as they do not require skilled clinicians and do not carry risk of complications, their accuracy is in doubt. A novel end-to-end deep learning-based algorithm was developed in this study that estimates NIBP directly from sequences of Korotkoff sounds (KSs) rather than oscillometric waveforms. First, sequences of segments of KSs were formed using different signal segmentation techniques, i.e., segmentation using sliding window with or without overlap and segmentation using the cardiac period estimation. Each segment within each sequence was then labeled as (i) after-systolic and before-diastolic (AB), or (ii) before-systolic or after-diastolic (BA) such that a binary sequence-to-sequence classification problem was achieved. To deal with the resultant sequence-to-sequence classification problem, an algorithm was developed by combining one-dimensional (1D) convolutional neural networks (CNNs) and recurrent neural networks (RNNs). The segments associated with systolic and diastolic blood pressure (SBP and DBP) are then identified as the segments at which the output target sequence switches from class BA to class AB and later from class AB to class BA. Lastly, the values of SBP and DBP are obtained by mapping the center point of the switching segments to the deflation curve. To evaluate the performance of the proposed NIBP estimation method, we used a database of 350 NIBP samples collected from 155 participants (87 male, age: 23-97 years, arm circumference: 10-35 cm, SBP: 81-104 mmHg, and DBP: 37-104 mmHg), and the achieved estimation errors for SBP and DBP, relative to the reference values, using a 5-fold cross validation approach, were 1.6±3.9 mmHg (mean absolute error ± standard deviation of error) and 2.5±4.0 mmHg, respectively. We finally conclude that the proposed end-to-end deep learning-based NIBP estimation algorithm from sequences of KSs is a novel technique that requires modest preprocessing steps and can measure BP accurately.

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

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−1 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.

Renewable tannic acid based self-healing polyurethane with dynamic phenol-carbamate network: Simultaneously showing robust mechanical properties, reprocessing ability and shape memory

Using green and renewable bio-based resources to realize multifunctional polymers is highly desirable for developing the next generation of smart materials. Herein, a facile method was proposed to prepare the thermally induced dynamic phenol-carbamate cross-linked thermoset polyurethane with robust mechanical properties, self-healing, reprocessing, and shape memory. Owing to the introduction of tannic acid (TA) that could form phenol-carbamate networks with isocyanate groups, the prepared TA based polyurethane (TA-PU) showed enhanced thermal stability and improved mechanical properties. Meanwhile, high self-healing efficiency could also be obtained by adjusting and controlling the content of dynamic phenol-carbamate bonds incorporated in polyurethane main chains, which indicated a good balance between robust mechanical properties and high self-healing efficiency in our target polymer. Further reprocessing tests demonstrated that the networked TA-PU polymer could also be well recycled by hot-pressing and solution casting. In addition, benefiting from the reversible crystallizable switching segments, that capable of being triggered by heat energy (when temperature is higher than the melting temperature of the soft segment), and cross-linked net points, the prepared TA-PU film could quickly recover from temporary shape to permanent shape. This elaborate design provides a heuristic perspective for developing multifunctional smart polymers from bio-based resources.

Separate crystallization and melting of polymer blocks and hydrogen bonding units in double-crystalline supramolecular polymers

End functionalization of oligomers by the multiple H-bonding units is a feasible way to prepare the supramolecular polymers (SMPs). The crystallization of oligomer blocks and H-bonding units can lead to form the complicated double crystalline structure in SMPs; such double crystalline behavior and its correlation with the physical properties are of fundamental importance for the processing and applications of SMPs. Herein, we choose the oligomeric polycaprolactone (PCL) end-functionalized by the self-complementary quadruple H-bonding 2-ureido-4-pyrimidinone (UPy) units (named as U-PCL) as the model double crystalline SMPs and investigate their crystalline structure, crystallization kinetics, thermally induced structural evolution, and structure-property relationships. The U-PCLs display the similar composition-dependent crystallization and melting behavior as the double crystalline block copolymers. The U-PCLs with short, medium-length, and long PCL blocks crystallize in the UPy crystals, UPy/PCL mixed crystals, and PCL crystals, respectively. Melting temperature of UPy crystals decreases and their melting peak disappears as the UPy content of U-PCLs decreases. UPy units and PCL blocks are microphase-separated in the U-PCLs, despite the absence of long-range ordered phase structure. Dual shape memory effects capable of switching at the body temperature were realized based on the double crystalline nature of U-PCLs by using UPy crystals as the physical crosslinkers and PCL blocks as the switching segments.

Tuning the Properties of Shape‐Memory Polyurethanes via the Nature of the Polyester Switching Segment

AbstractShape‐memory polymers that contain semicrystalline domains with a melting temperature (Tm) above and a crystallization temperature (Tc) below physiological temperature as fixing elements are useful to create medical devices or implants that can be custom‐shaped inside or around the body. With the goal to expand the palette of materials that exhibit such properties, a series of segmented polyurethanes (PUs) containing different crystallizable polyester segments is investigated. The nature of the polyester, its molecular weight, and the ratio of hard to soft segments are systematically varied and the effect on the mechanical, thermal, and shape‐memory properties of the various PUs is studied. Poly(1,12‐dodecylene dodecanoate), poly(1,6‐hexylene dodecanoate), and poly(ethylene sebacate) (PES) are selected as crystallizable polyester segments. The PES‐based PUs display Tc values of 25–35 °C and a Tm of 60–63 °C, and allow good shape fixing at 37 °C.

Preparation of body-temperature-triggered shape-memory polyurethane with biocompatibility using isosorbide and castor oil

Shape memory polyurethanes (SMPUs) have attracted much attention in the biomedical field because they can easily control the transition temperature (Ttrans) to shape memory and are biocompatible. In this study, a shape memory polyurethane with both biocompatibility and a Ttrans close to the body temperature was synthesized by using natural derivatives of isosorbide and castor oil in place of petroleum-based materials. Isosorbide and castor oil were used to form net points, and polycaprolactone diol (PCL diol) acted as the switching segment. The synthesized four polyurethane (PCL diol/isosorbide/castor oil, PICU-1, 2, 3, 4) with different isosorbide contents exhibited desired thermal and mechanical properties. In the thermo-cyclic shape memory testing experiment, the PICU series demonstrated good shape memory property, with more than 95% shape recovery ratio (Rr) and more than 90% shape fixity ratio (Rf), and PICU-3 recovered its shape within 20 s in a 37 °C water bath. In addition, the PICU series proved to be safe materials with excellent biocompatibility, as indicated by the observed C2C12 cells viability and proliferation. The stent made with the PICU-3 film showed near complete magnetization at 37 °C within 18 s and proved to be a suitable self-expanding stent.

Self-reinforced triple-shape memory silicone rubber composites with precise designable second temporary shapes by one step fixation

Silicone rubber (SR) plays an irreplaceable role in biomedicine and aerospace applications due to its biocompatibility, flexibility and excellent stability in extreme harsh conditions. However, only a few studies focus on SR based shape memory materials, and the increasing intelligent applications of SR materials are limited by the insufficient strength and poor designable recovery behavior. Herein, we report a simple method via monomers/prepolymers blend and in-situ polymerization/cross-linking to prepare thermal responsive shape memory silicone rubber composites (SRCs) with three transition temperatures. In the SRCs, poly (methyl methacrylate) (PMMA) and poly (ethyl methacrylate) (PEMA) are used as switching segments and reinforced phase, polydimethylsiloxane (PDMS) networks provide a third transition and dominate the permanent shape. In a thermal stimulus recovery of SRCs with PMMA and PEMA switching segments are used, second temporary shapes can be precisely designed by just tuning the proportions of PMMA and PEMA, and a practical linear relationship between recovered scale and PEMA content is built. The shape memory and mechanical properties of SRCs are both enhanced by micro-nano particles (800 nm) of PMMA and PEMA. The SRCs present excellent thermal stability, hydrophobicity and hygroscopicity. The triple-shape memory SRC materials have potential applications in smart materials and actuators.

Development of Thermo-Responsive Polycaprolactone-Polydimethylsiloxane Shrinkable Nanofibre Mesh.

A thermally activated shape memory polymer based on the mixture of polycaprolactone (PCL) and polydimethylsiloxane (PDMS) was fabricated into the nanofibre mesh using the electrospinning process. The added percentages of the PDMS segment in the PCL-based polymer influenced the mechanical properties. Polycaprolactone serves as a switching segment to adjust the melting temperature of the shape memory electro-spun PCL–PDMS scaffolds to our body temperature at around 37 °C. Three electro-spun PCL–PDMS copolymer nanofibre samples, including PCL6–PDMS4, PCL7–PDMS3 and PCL8–PDMS2, were characterised to study the thermal and mechanical properties along with the shape memory responses. The results from the experiment showed that the PCL switching segment ratio determines the crystallinity of the copolymer nanofibres, where a higher PCL ratio results in a higher degree of crystallinity. In contrast, the results showed that the mechanical properties of the copolymer samples decreased with the PCL composition ratio. After five thermomechanical cycles, the fabricated copolymer nanofibres exhibited excellent shape memory properties with 98% shape fixity and above 100% recovery ratio. Moreover, biological experiments were applied to evaluate the biocompatibility of the fabricated PCL–PDMS nanofibre mesh. Owing to the thermally activated shape memory performance, the electro-spun PCL–PDMS fibrous mesh has a high potential for biomedical applications such as medical shrinkable tubing and wire.

Ultralarge Contraction Directed by Light‐Driven Unlocking of Prestored Strain Energy in Linear Liquid Crystal Polymer Fibers

AbstractAnisotropic 1D contraction motion of polymeric actuating materials has drawn growing interests in fields ranging from soft robotics to biomimetic muscles. Although light‐driven liquid crystal polymers (LCPs) represent promising candidates to realize contraction (<20%) triggered remotely and spatially, there remain multitudes of challenges to develop an LCP system possessing ultralarge contraction rate. Here, a novel strategy combining shape memory effect and photochemical phase transition is presented to realize light‐driven contraction as large as 81% in a newly designed linear liquid crystal copolymer, where the eutectic mesogens of azobenzene and phenyl benzoate self‐organize into the smectic B phase. Importantly, this highly ordered structure as the switching segment firmly locks the stress‐induced strain energy, which is rapidly released by reversible trans–cis photoisomerization that destroys the lamellar liquid crystal phase, therefore leading to such ultralarge contraction. Fibers serve as light‐driven building blocks to achieve precise origami, to mimic the recovery of a “broken” spider web and to screen objects in different sizes, laying new ground for advanced applications of light‐driven LCPs from biomimetic robots to human assists.

4D printing of shape memory aliphatic copolyester via UV-assisted FDM strategy for medical protective devices

4D printing, as a booming additive manufacturing technology of smart material, provides a new opportunity for the development of shape memory polymers (SMPs). Meanwhile, the diversity of SMPs structure calls for flexible and well-adapted printing technology. Fused deposition modelling (FDM) is one of the most versatile and cost-effective methods owing to the simplicity of the technique and broad compatibility with a wide variety of materials, but it fails to deal with the fabrication of shape memory networks that possess excellent structural stability as well as shape memory effect (SME). Aiming to personalized or patient-adaptable treatment devices, in this work, we demonstrate a UV-assisted FDM 4D printing strategy to fabricate elbow protector models based on shape memory copolyester networks. First, the linear unsaturated copolyesters were synthesized, amongst, poly(lactic acid) was chosen as hard segment providing the material a good mechanical performance and printability, the poly(ε-caprolactone) with strong crystallizability was employed as switching segment, and a functional coupling agent contained double bonds was used to join the two segments and as the same time. This copolyester can be easily processed into filament, and the in-situ formation of photo-crosslinking network during the UV-assisted FDM printing not only enhances the bonding strength of each layer, but also may guarantee the obtained objects a good shape memory property. Three models with distinctly Chinese characteristics were printed to demonstrate excellent SME. Then, the elbow protectors both in personalized and patient-adaptable treatment strategies were developed, which indicates a great potential in robust applications.

Hydrogen‐bonded poly(vinyl alcohol)‐boehmite composites exhibiting excellent shape memory properties

AbstractPoly(vinyl alcohol) (PVA) networks cross‐linked by inorganic nanofillers‐boehmite (AlOOH) nanowires via strong hydrogen bonding was prepared by a facile strategy. These PVA‐AlOOH composites displayed significantly enhanced mechanical and thermal properties due to the excellent mechanical property and high heat resistant of AlOOH nanowires, as well as the strong hydrogen bonding formed between PVA and AlOOH. Interestingly, it was worth mentioning that the PVA‐AlOOH composites exhibited excellent shape memory behavior. The strong hydrogen bonding between PVA matrix and AlOOH nanowires acted as the hard segments to maintain the permanent shape, while the weak one between PVA chains served as switching segments to fix the temporary shape and recover to the permanent shape. This physical cross‐linked system provided a simple and efficient strategy to obtain smart shape memory materials.

Preparation and shape memory properties of rigid-flexible integrated epoxy resins via tunable micro-phase separation structures

In this work, two types of rigid-flexible integrated epoxy resins, diglycidyl ether of eugenol-2-mercaptoethanol (DGEEM) and diglycidyl ether of vanillic alcohol (DGEVA), which possess similar rigid methoxy-substituted aromatic structures and different soft aliphatic chains in length, were prepared. Micro-morphology structures were tested by AFM, AFM nanomechanical mapping, and AFM-IR. Macro-properties were respectively characterized by tensile test and shape memory test. Results showed that a series of tunable micro-morphology structures including hard-phase-rich sea-island structure, bi-continuous structure, and soft-phase-rich sea-island structure were explored after cured with 4,4-methylenedianiline. Moreover, the shape memory mechanism for these SMEPs was concluded: phase separation structures are the base of these SMEPs, and soft phase acts as switching segments, which contributes to shape memory strain of the SMEPs. The optimal designed SMEPs with bi-continuous phase structure was prepared from this mechanism, which exhibit good mechanical properties and excellent shape memory performance.

Investigating the Roles of Crystallizable and Glassy Switching Segments within Multiblock Copolymer Shape-Memory Materials

ABSTRACTThe variation of the molecular architecture of multiblock copolymers has enabled the introduction of functional behaviour and the control of key mechanical properties. In the current study, we explore the synergistic relationship of two structural components in a shape-memory material formed of a multiblock copolymer with crystallizable poly(ε-caprolactone) and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments (PCL-PIBMD). The thermal and structural properties of PCL-PIBMD films were compared with PCL-PU and PIBMD-PU, investigated by means of DSC, SAXS and WAXS measurements. The shape-memory properties were quantified by cyclic, thermomechanical tensile tests, where deformation strains up to 900% were applied for programming PCL-PIBMD films at 50 °C. Toluene vapor treatment experiments demonstrated that the temporary shape was fixed mainly by glassy PIBMD domains at strains lower than 600%, with the PCL contribution to fixation increasing to 42±2% at programming strains of 900%. This study into the shape-memory mechanism of PCL-PIBMD provides insight into the structure-function relation in multiblock copolymers with both crystallizable and glassy switching segments.

Toughness improvement and anisotropy in semicrystalline physical hydrogels

A major challenge in the gel science is to create mechanically strong hydrogels with anisotropic properties as observed in many biological tissues. Here, we report a simple one-step method of producing high-strength physical hydrogels exhibiting microstructural and mechanical anisotropy. As the precursor material, we use semicrystalline shape-memory hydrogels consisting of poly(N, N-dimethylacrylamide) chains interconnected by n-octadecyl acrylate (C18A) segments forming crystalline domains and hydrophobic associations acting as switching segments and netpoints, respectively. To generate anisotropic microstructure, we impose a prestretching on the isotropic hydrogel sample above the melting temperature Tm of its crystalline domains followed by cooling below Tm under strain to fix the elongated shape of the gel sample. A significant microstructural and mechanical anisotropy was achieved that could be tuned by the magnitude of the prestretch ratio λo. Directional brittle-to-ductile and ductile-to-brittle transitions could be induced by adjusting the prestretch ratio λo. Small- and wide-angle X-ray scattering measurements and mechanical tests highlight a critical prestretch ratio λo at which the hydrogel exhibits the highest microstructural and mechanical anisotropy due to the finite extensibility of the network chains. At λo = 1.8, the hydrogel exhibits Young's moduli of 161 ± 14 and 76 ± 7 MPa, and toughness of 16 ± 1 and 1.3 ± 0.1 MJ m−3 along and perpendicular to the prestretching direction, respectively.

Thermal Annealing to Modulate the Shape Memory Behavior of a Biobased and Biocompatible Triblock Copolymer Scaffold in the Human Body Temperature Range.

A biodegradable and biocompatible electrospun scaffold with shape memory behavior in the physiological temperature range is here presented. It was obtained starting from a specifically designed, biobased PLLA-based triblock copolymer, where the central block is poly(propylene azelate-co-propylene sebacate) (P(PAz60PSeb40)) random copolymer. Shape memory properties are determined by the contemporary presence of the low melting crystals of the P(PAz60PSeb40) block, acting as switching segment, and of the high melting crystal phase of PLLA blocks, acting as physical network. It is demonstrated that a straightforward annealing process applied to the crystal phase of the switching element gives the possibility to tune the shape recovery temperature from about 25 to 50 °C, without the need of varying the copolymer's chemical structure. The thermal annealing approach here presented can be thus considered a powerful strategy for "ad hoc" programming the same material for applications requiring different recovery temperatures. Fibroblast culture experiments demonstrated scaffold biocompatibility.