The study, led by Dr. Cheng-Hui Li from the School of Chemistry and Chemical Engineering, Nanjing University, and Dr. Pengfei Zheng from the Children's Hospital of Nanjing Medical University, successfully developed an artificial muscle with mechanical properties similar to natural muscle tissue. The team utilized molecular design to synthesize the artificial muscle through block copolymerization of biocompatible perfluoropolyether (PFPE) and polycaprolactone diol (PCL). By precisely tuning the intra- and intermolecular interactions of PFPE and PCL (e.g., dipole-dipole interactions) under controlled conditions, they achieved self-assembly and microphase separation, suppressing the crystallization of PCL moeity.
The material exhibits an amorphous state at room temperature and without external force, maintaining a low elastic modulus and high elasticity. Under tensile stress, the amorphous polymer chains unfold, align, and reorient along the loading direction, significantly enhancing the material's tensile strength and toughness. The material also demonstrates remarkable tear and puncture resistance. During cyclic tensile deformation at large strains, PCL chains escape the amorphous regions to form chain-aligned microcrystalline structures, imparting muscle-like training enhancement properties to the material.
Additionally, the artificial muscle showcases exceptional shape memory and actuation performance, with actuation strains up to 600% and energy densities of 1450 J/kg. Under thermal stimulation, the material can lift objects weighing more than 5000 times its own weight and reliably perform reversible contraction and extension motions over multiple heating and cooling cycles. "This artificial muscle combines low modulus and high toughness while successfully replicating the training enhancement and actuation functions of natural muscle, showing great potential in prosthetic actuators," said Dr. Li.
The material demonstrates excellent biocompatibility, showing no cytotoxicity and significantly promoting myoblast growth and differentiation, forming myotubes aligned along the stretching direction of the material. Histological evaluations after implantation revealed that the material facilitated muscle tissue growth along the scaffold. After four weeks, regenerated muscle exhibited well-organized structure and morphology, with muscle contractile force comparable to that of normal rats. Furthermore, vascular regeneration, evaluated through CD31 and α-SMA staining, indicating enhanced angiogenesis, crucial for muscle regeneration. "The exceptional elasticity, toughness, and softness of this artificial muscle allow it to flexibly interact with residual muscles," Dr. Zheng noted. "This enables rats to maintain daily activities after scaffold implantation without muscle atrophy or joint dysfunction caused by traditional surgical suturing or immobilization, significantly shortening the recovery period."
This innovative artificial muscle material opens new avenues for biomedical applications, particularly in prosthetics, tissue engineering, and regenerative medicine.
