This study presents a new wearable insole pressure sensor (IPS), composed of fabric coated in a carbon nanotube-based composite thin film, and validates its use for quantifying ground reaction forces (GRFs) during human walking. Healthy young adults (n = 7) walked on a treadmill at three different speeds while data were recorded simultaneously from the IPS and a force plate (FP). The IPS was compared against the FP by evaluating differences between the two instruments under two different assessments: (1) comparing the two peak forces at weight acceptance and push-off (2PK) and (2) comparing the absolute maximum (MAX) of each gait cycle. Agreement between the two systems was evaluated using the Bland–Altman method. For the 2PK assessment, the group mean of differences (MoD) was −1.3 ± 4.3% body weight (BW) and the distance between the MoD and the limits of agreement (2S) was 25.4 ± 11.1% BW. For the MAX assessment, the average MoD across subjects was 1.9 ± 3.0% BW, and 2S was 15.8 ± 9.3% BW. The results of this study show that this sensor technology can be used to obtain accurate measurements of peak walking forces with a basic calibration and consequently open new opportunities to monitor GRF outside of the laboratory.

Two approaches have been employed in the preparation of hierarchical compositelaminates with a carbon nanotube (CNT) phase. Glass fibers were coated with CNTsusing electrophoretic deposition (EPD) prior to infusion with epoxy resin. TheCNTs were functionalized using an ultrasonicated-ozone process followed byreaction with polyethyleneimine (PEI) to enhance CNT to fiber and matrixadhesion. Chemical vapor deposition (CVD) was also used to grow CNTs onto quartzfibers, prior to infusion with an epoxy resin modified with a thermoplasticnanophase. The mechanical performance of the two CNT laminates types weresimilar, however, the fracture surfaces indicated distinct differences. The EPDlaminates showed fracture in the CNT-rich interphase region, whereas, the CVDlaminates showed that strength was limited by adhesion failure at the CNT-fiberinterface. The electrical conductivity of CVD laminates was 100 times higherthan EPD laminates. For the EPD laminates the PEI functionalization increasesthe CNT-CNT distance resulting in reduced conductivity, while the high CNTpacking density and residual iron catalyst on the fiber surface in the CVDlaminates creates conducting pathways resulting in higher conductivities.