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As a kind of smart material, shape memory polymer (SMP) shows great application potential in the biomedical field. Compared with traditional metal-based medical devices, SMP-based devices have the following characteristics: 1) The adaptive ability allows the biomedical device to better match the surrounding tissue after being implanted into the body by minimally invasive implantation; 2) it has better biocompatibility and adjustable biodegradability; 3) mechanical properties can be regulated in a large range to better match with the surrounding tissue. 4D printing technology is a comprehensive technology based on smart materials and 3D printing, which has great application value in the biomedical field. 4D printing technology breaks through the technical bottleneck of personalized customization and provides a new opportunity for the further development of the biomedical field. This paper summarizes the application of SMP and 4D printing technology in the field of bone tissue scaffolds, tracheal scaffolds, and drug release, etc. Moreover, this paper analyzes the existing problems and prospects, hoping to provide a preliminary discussion and useful reference for the application of SMP in biomedical engineering.

Shape‐memory polymers have attracted attention as smart implant materials in recent years because they are lightweight, low‐cost, easily processable, and because they undergo large deformation. Here, cellulose nanofibers (CNFs) were used as a reinforcement for polyhydroxybutyrate (PHB)/polycaprolactone (PCL) composites to improve mechanical properties. The composites were investigated by rheological tests, differential scanning calorimetry, dynamic mechanical analysis, mechanical property tests, and shape‐memory tests. The printability of PHB/PCL/CNFs composites was demonstrated by using them to print interconnected porous structures with a gyroid surface. The results showed that the PHB/PCL (80:20) composites with 1 wt% CNF displayed the best comprehensive mechanical and shape‐memory properties. As a functional verification, a model of the self‐opening hand was fabricated by 3D printing, and its deformation and recovery capabilities were evaluated.

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Conductive hydrogel (CH) strain sensors have made signi cant progress in wearable electronic products in recent years. However, the use of aqueous solvents as the dispersion medium in CHs largely limits the scope of applications of CHs and impedes the combination of the mechanical properties and ionic conductivity, which is urgently desired to be addressed. Herein, a simple one-pot preparation of antifreezing, anti-drying ionic CHs with high stretchability (up to 869%), toughness (6.60 MJ/m 3 ), and Young's modulus (0.56 MPa) was proposed. These CHs consist of polyvinyl alcohol, tannic acid, and sodium chloride dispersed in a solvent consisting of glycerol and cellulose nano ber suspension. The thus-synthesized CHs exhibit good ionic conductivity (~ 0.86 S/m) and strain sensitivity (gauge factor of 8.54). The organohydrogel possesses a sensitive strain sensing capability and a wide-working temperature range (-50°C to 60°C), and good stability (30 d in room-temperature) to detect human movement, such as large (joint movement) and subtle movements (voice in the throat). These advantages allow organohydrogel sensors to show great potential for electronic skin, personal healthcare, and exible wearable devices.