Smart Energy Releasing Filaments in Fabrication of Selftightening Surgical Wound Sutures

Shape-memory polymers (SMPs) have found their specific applications in the medical products. One of the main aspects of SMPs is their abilities to return to their original shape and, thus, a level of force or energy released. The latter hypothesizes the development of specific sutures in which upon activation, they could return to its original shorter length and therefore additional tightening of a wound if already loosely stitched. This work aims at fabrication and characterization of self-tightening filaments exhibiting shape-memory effects. Thermoplastic polyurethane (TPU) and polylactic acid (PLA) were used to fabricate melt mixed bulk and filament blended specimens. Tensile, flexural and impact performance were examined to optimize the polymer fractions. Blocked-force load cell was utilized to measure the energy release and recovery force as a function of the wires diameter. It was demonstrated that with the addition of TPU content the tensile and flexural properties decrease whilst the impact resistance increases. The results based on optimized TPU content showed successful fabrication of blended filaments sensitive to temperature. The findings visually and quantitatively expressed wires becoming shorter upon exposure to warm water of 50-60 °C confirming their response to be used as a self-tightening suture. Blocked-force outputs showed a 130% increase in energy release when the filament diameter is three folded.