Study of silver nanoparticle-loaded auxetic polyurethane foams for medical cushioning applications

Abstract

Patients who are bed-ridden and users of wheelchairs are prone to development of pressure sores at the cushion–skin interface due to stress concentrations, moisture and bacterial infections. The purpose of this work is to develop antibacterial auxetic polyurethane (PU) foams for use in seat cushions and hospital beds. Silver nanoparticles (SNPs) were used in the synthesis of PU foams to induce antibacterial properties. These foams were then converted to negative Poisson’s ratio or auxetic polyurethane (APU) foams to improve the mechanical properties. Two different APU foams were made using compression factors of 2.07 and 2.97. Chemical composition, microstructure, thermal, mechanical and antibacterial properties of SNP-based PU foams before and after conversion to APUs were studied. The study showed that APU foams fabricated using higher compression factor greatly enhanced the antibacterial properties against gram positive (Staphylococcus aureus and Staphylococcus epidermidis) and gram negative (Pseudomonas aeruginosa and Escherichia coli) bacteria. APU foams made using higher compression ratio also exhibited increase in the compression strength at higher strains (after 20% strain). This study shows that the antibacterial APU foams developed in this work can possibly cause less infection and ensure better stress distribution at the cushion–skin interface.