Recent advances and perspectives of shape memory polymer fibers

Shape memory composite membrane with widely programmable electromagnetic shielding effectiveness

The application of shape memory smart materials in the field of electromagnetic interference (EMI) shielding can compensate for their poor adaptability and promote the development of electromagnetic shielding composite materials towards multi-functionality and intelligence. Herein, an intelligent poly(ethylene-co-vinyl acetate)/polydopamine/MXene (EVA/PDA/MXene) composite membrane with tunable electromagnetic shielding capability over a wide range was prepared using electrospinning and dip-coating techniques. Firstly, electrospinning technology was used to prepare highly cross-linked EVA fiber membranes. Secondly, the surface of these membranes was modified with dopamine. And finally, dip-deposition technology was employed to tightly attach MXene nanosheets to the surface of the modified membranes. The electromagnetic shielding effectiveness of the EVA/PDA/MXene-30-6 composite membrane in the X-band (8.2-12.4 GHz) is up to 74.7 dB, and both the shape fixation rate (Rf) and shape recovery rate (Rr) are above 90%. Most importantly, it achieves a reversible tuning of shielding effectiveness from 26.2 dB to 74.7 dB under a tensile strain of 0-30%. Furthermore, the electromagnetic shielding effectiveness of the composite membrane remains virtually unchanged after undergoing continuous bending and folding, and its surface temperature can reach 93.2 °C when subjected to a voltage of 2.5 V, thereby demonstrating exceptional electro-thermal conversion capability. This multifunctional composite membrane, characterized by its adaptability, provides a direction for the development of electromagnetic shielding composites.

Nature-Inspired Intelligent Cotton Fabrics with Excellent Shape Memory and Superhydrophobic Properties

Driven by technological advancements and rising living standards, the demand for high-performance cotton textiles continues to grow. Drawing inspiration from the stimuli-responsive behavior of Mimosa pudica and the inherent superhydrophobicity of lotus leaf surfaces, this study presents the development of a new class of smart cotton fabrics integrating superhydrophobicity, shape memory functionality, and wear resistance. The engineered smart cotton fabrics incorporate Eucommia ulmoides gum (EUG) and surface-tailored sepiolite particles as core functional elements. Central to this work is an innovative surface modulation strategy leveraging shape memory effects to dynamically control material hydrophobicity through thermoresponsive structural reconfiguration. Fabricated via a scalable dip-coating technique, these composites achieve tunable wettability without fluorine-based chemicals, marking a departure from conventional approaches. The innovation of this manuscript also lies in the cotton fabric's fluorine-free composition and its eco-friendly preparation process. These characteristics enable cotton fabrics to adjust their surface wettability based on different usage environments and needs, offering vast possibilities for creating and designing intelligent products.

4D Printing Self-Sensing and Load-Carrying Smart Components

In the past decade, 4D printing has received attention in the aerospace, automotive, robotics, and biomedical fields due to its lightweight structure and high productivity. Combining stimulus-responsive materials with 3D printing technology, which enables controllable changes in shape and mechanical properties, is a new technology for building smart bearing structures. A multilayer smart truss structural component with self-sensing function is designed, and an internal stress calibration strategy is established to better adapt to asymmetric loads. A material system consisting of continuous carbon fibers and polylactic acid was constructed, and an isosceles trapezoidal structure was chosen as the basic configuration of the smart component. The self-inductive properties are described by analyzing the relationship between the pressure applied to the specimen and the change in the specimen's own resistance. Load-carrying capacity is realized by electrically heating the continuous carbon fibers in the component. Thermal deformation calibrates internal stress and enhances the load-carrying ability of the component over 50%. The experimental results demonstrate that the truss structure designed in this paper has strong self-induction, self-driving ability, and asymmetric load adaptation ability at the same time. This verifies that the 4D-printed smart component can be used as a load-carrying element, which broadens the application scope of smart components.

Scalability of API-Loaded Multifilament Yarn Production by Hot-Melt Extrusion and Evaluation of Fiber-Based Dosage Forms

Fiber-based technologies are widely used in various industries, but their use in pharmaceuticals remains limited. While melt extrusion is a standard method for producing medical fibers such as sutures, it is rarely used for pharmaceutical fiber-based dosage forms. The EsoCap system is a notable exception, using a melt-extruded water-soluble filament as the drug release trigger mechanism. The challenge of producing drug-loaded fibers, particularly due to the use of spinning oils, and the processing of the fibers are addressed in this work using other approaches. The aim of this study was to develop processes for the production and processing of pharmaceutical fibers for targeted drug delivery. Fibers loaded with polyvinyl alcohol and fluorescein sodium as a model drug were successfully prepared by a continuous melt extrusion process and directly spun. These fibers exhibited uniform surface smoothness and consistent tensile strength. In addition, the fibers were further processed into tubular dosage forms using a modified knitting machine and demonstrated rapid drug release in a flow cell.

Untethered soft actuators for soft standalone robotics

Soft actuators produce the mechanical force needed for the functional movements of soft robots, but they suffer from critical drawbacks since previously reported soft actuators often rely on electrical wires or pneumatic tubes for the power supply, which would limit the potential usage of soft robots in various practical applications. In this article, we review the new types of untethered soft actuators that represent breakthroughs and discuss the future perspective of soft actuators. We discuss the functional materials and innovative strategies that gave rise to untethered soft actuators and deliver our perspective on challenges and opportunities for future-generation soft actuators.

Self-Healing of Poly(vinyl Alcohol)/Poly(acrylic Acid)-Polytetrahydrofuran-Poly(acrylic Acid) Blend Boosted via Shape Memory

The self-healable polymers that can repair physical damage autonomously to extend their lifetime and reduce maintenance costs are promising intelligent materials. However, utilizing shape memory to facilitate self-repair is unusual at present. In this work, a series of poly(acrylic acid)-polytetrahydrofuran-poly(acrylic acid) polymers (PAA-PTMG-PAA, diPAA-PTMG) are synthesized as a switching phase and healing accelerator to blend into poly(vinyl alcohol) (PVA). The water swelling rate of the blend is up to 400.0% at 1/1 molecular weight ratio of PTMG/PAA and 20.0 wt % blend ratio of diPAA-PTMG to PVA, and its crystallization is changed significantly under wet conditions. The blend membrane exhibits not only a good hydrothermal-response shape memory effect but also a favorable self-healing behavior. The tensile strength and elongation at break are 12.4 MPa and 320.0% after healing at 25 °C, respectively. In particular, the wound membrane can achieve a better self-healing effect with the assistance of shape memory at 37 °C, and the elongation at the break increased to 515.9% after healing. The membrane is not cytotoxic, so it will be a promising biomedical material.

Material Extrusion of Helical Shape Memory Polymer Artificial Muscles for Human Space Exploration Apparatus

Astronauts suffer skeletal muscle atrophy in microgravity and/or zero-gravity environments. Artificial muscle-actuated exoskeletons can aid astronauts in physically strenuous situations to mitigate risk during spaceflight missions. Current artificial muscle fabrication methods are technically challenging to be performed during spaceflight. The objective of this research is to unveil the effects of critical operating conditions on artificial muscle formation and geometry in a newly developed helical fiber extrusion method. It is found that the fiber outer diameter decreases and pitch increases when the printhead temperature increases, inlet pressure increases, or cooling fan speed decreases. Similarly, fiber thickness increases when the cooling fan speed decreases or printhead temperature increases. Extrusion conditions also affect surface morphology and mechanical properties. Particularly, extrusion conditions leading to an increased polymer temperature during extrusion can result in lower surface roughness and increased tensile strength and elastic modulus. The shape memory properties of an extruded fiber are demonstrated in this study to validate the ability of the fiber from shape memory polymer to act as an artificial muscle. The effects of the operating conditions are summarized into a phase diagram for selecting suitable parameters for fabricating helical artificial muscles with controllable geometries and excellent performance in the future.