Ultra-Lightweight and Ultra-Flexible PDMS/MWCNT Open-Cell Foam Nanocomposite BioSensors for Pressure Mapping

Biomedical pressure-detecting sensors have attracted great interest in a wide spectrum of healthcare monitoring applications including injury prevention and motion analysis. However, current technologies in the market possess some drawbacks including low working pressure ranges, high hysteresis effects, and low recoverability in conditions where limited air ventilation exists such as shoe insoles, which adversely affect the performance of these sensors. To overcome these challenges, in this study a novel ultralightweight piezoresistive open-cell foam nanocomposite sensor which operates based on resistivity change in the material while an external force is applied to it, is designed and fabricated. Polydimethylsiloxane (PDMS)/multi-walled carbon nanotube (MWCNT) foam nanocomposite with two governing factors of porosity and conductive filler content was fabricated by a manufacturing approach that integrated solution casting and particulate leaching method. Mechanical properties of PDMS/MWCNT open-cell foam nanocomposite were characterized by the compression tests and its elastic and plastic behaviour were investigated. Experimental results indicated that samples with 60% porosity had higher energy absorption and mechanical strength than the samples with 70% and 80% porosities. Moreover, foam nanocomposites at the same porosities showed larger energy absorption and mechanical strength when they contained higher MWCNTs in their structure. PDMS/MWCNT foam nanocomposite demonstrated high flexibility, high compressibility up to 90%, and high recoverability in addition to limited mechanical hysteresis (less than 3%) without experiencing noticeable macroscopic damage which provides a great advantage over the similar piezoresistive sensors in the literature.