A novel radiofrequency-induced phase-transition strategy for shape and stiffness switching in poly(glycerol dodecanoate) polymers

Abstract

Polyglycerol ester-based polymers (PGEs), characterized by unique properties such as thermo-responsive shape memory, mechanical properties matching those of soft tissues, and controllable biodegradability, are well-suited for minimally invasive smart implants targeting soft tissue applications. However, the phase-transition mechanism of the polymer relies on environmental temperature changes, introducing uncontrollable factors during implantation. In this study, nanoscale carbon black (CB) was used to modify the electrical conductivity of poly(glycerol dodecanoate) (PGD), one of the PGEs, enabling active radiofrequency (RF)-induced phase-transition behavior. Unlike the passive method triggered by body temperature, active phase transitions can enhance the operability of the implant during surgery. The relationship between polymer conductivity and electric field intensity on the phase-transition performances of PGD was investigated using a self-developed RF antenna. Through this approach, a PGD + 7wt%CB polymer was selected, achieving 30-second shape/stiffness switching effects at an RF intensity of 2200 V m⁻¹ while maintaining mild thermal tissue damage (CEM43 = 14.33) during this period. This achievement provides a novel method for controlling the phase transition of PGEs, which can be further applied to the design and fabrication of the minimally invasive smart implants, such as intervertebral disc scaffolds, neural probes, and artificial muscles.