This paper reports an approach for the fabrication of shape-changing bilayered scaffolds, which allow the growth of aligned skeletal muscle cells, using a combination of 3D printing of hyaluronic acid hydrogel, melt electrowriting of thermoplastic polycaprolactone-polyurethane elastomer, and shape transformation. The combination of the selected materials and fabrication methods allows a number of important advantages such as biocompatibility, biodegradability, and suitable mechanical properties (elasticity and softness of the fibers) similar to those of important components of extracellular matrix (ECM), which allow proper cell alignment and shape transformation. Myoblasts demonstrate excellent viability on the surface of the shapechanging bilayer, where they occupy space between fibers and align along them, allowing efficient cell patterning inside folded structures. The bilayer scaffold is able to undergo a controlled shape transformation and form multilayer scroll-like structures with cells encapsulated inside. Overall, the importance of this approach is the fabrication of tubular constructs with a patterned interior that can support the proliferation and alignment of muscle cells for muscle tissue regeneration.

This paper reports an approach for the fabrication of highly aligned soft elastic fibrous scaffolds using touch spinning of thermoplastic polycaprolactone− polyurethane elastomers and demonstrates their potential for the engineering of muscle tissue. A family of polyester−polyurethane soft copolymers based on polycaprolactone with different molecular weights and three different chain extenders such as 1,4-butanediol and polyethylene glycols with different molecular weight was synthesized. By varying the molar ratio and molecular weights between the segments of the copolymer, different physicochemical and mechanical properties were obtained. The polymers possess elastic modulus in the range of a few megapascals and good reversibility of deformation after stretching. The combination of the selected materials and fabrication methods allows several essential advantages such as biocompatibility, biodegradability, suitable mechanical properties (elasticity and softness of the fibers), high recovery ratio, and high resilience mimicking properties of the extracellular matrix of muscle tissue. Myoblasts demonstrate high viability in contact with aligned fibrous scaffolds, where they align along the fibers, allowing efficient cell patterning on top of the structures. Altogether, the importance of this approach is the fabrication of highly oriented fiber constructs that can support the proliferation and alignment of muscle cells for muscle tissue engineering applications.

In this paper, we report detailed investigation of structural changes occurring in two-way shape memory polymers (2W-SMP) upon thermal cycling at constant strain conditions. We demonstrate that cooling of stretched chemically cross-linked polycaprolactone results first in a slow decrease of stress, the stress drops rapidly upon further cooling, and further cooling results in sharp increase of stress. In this paper, we investigated structural changes occurring in each of these three phases using in situ force measurements and XRD analysis (SAXS and WAXS). In the first phase, the stress decreases due to decrease of entropic factor in the elastic state. In the second phase, polymer chains start to crystallize in the stretched state as a result of the number of active springs producing stress decreasing. This results in the decrease of the stretching degree of other polymer chains, and finally, unstretched polymer chains crystallize that result in an increase of stressthe polymer simply tends to shrink.

Development of fiber‐spinning technologies and materials with proper mechanical properties is highly important for the manufacturing of aligned fibrous scaffolds mimicking structure of the muscle tissues. Here, the authors report touch spinning of a thermoplastic poly(1,4‐butylene adipate)‐based polyurethane elastomer, obtained via solvent‐free polymerization. This polymer possesses a combination of important advantages such as 1) low elastic modulus in the range of a few MPa, 2) good recovery ratio and 3) resilience, 4) processability, 5) nontoxicity, 6) biocompatibility, and 7) biodegradability that makes it suitable for fabrication of structures mimicking extracellular matrix of muscle tissue. Touch spinning allows fast and precise deposition of highly aligned micro‐ and nano‐fibers without use of high voltage. C2C12 myoblasts readily align along soft polymer fibers and demonstrate high viability as well as proliferation that make proposed combination of polymer and fabrication method highly suitable for engineering skeletal muscles.