Green preparation of antibacterial shape memory foam based on bamboo cellulose nanofibril and waterborne polyurethane for adaptive relief of plantar pressure

Abstract

This study developed an aqueous solution blending and freeze-drying method to prepare an antibacterial shape memory foam (WPPU/CNF) based on waterborne PHMG-polyurethane and cellulose nanofibers derived from bamboo in response to the increasing demand for environmentally friendly, energy conserving, and multifunctional foams. The obtained WPPU/CNF composite foam has a highly porous network structure with well-dispersed CNFs forming hydrogen bonds with the WPPU matrix, which results in a stable and rigid cell skeleton with enhanced mechanical properties (80 KPa) and anti-abrasion ability. The presence of guanidine in the polyurethane chain endowed the WPPU/CNF composite foam with an instinctive and sustained antibacterial ability against Escherichia coli and Staphylococcus aureus. The WPPU/CNF composite foam exhibited a water-sensitive shape memory function in a cyclic shape memory program because of the chemomechanical adaptability of the hydrogen-bonded network of CNFs in the elastomer matrix. The shape-fixation ratio for local compression reached 95 %, and the shape-recovery rate reached 100 %. This allows the WPPU/CNF pad prototype to reversibly adjust the undulation height to adapt to plantar ulcers, which can reduce the local plantar pressure by 60 %. This study provides an environmentally friendly strategy for cellulose-based composite fabrication and enriches the design and application of intelligent foam devices.