Preparation and laser sintering of a thermoplastic polyurethane carbon nanotube composite-based pressure sensor

Selective laser sintering (SLS) is a desirable method for fabricating human motion detecting sensors as it can produce a complex shape with different materials that are machinable to specific applications. The bottleneck in the SLS processing of sensors is the preparation of a material that is both flexible and conductive. In this study, carbon nanotubes (CNTs) were selected as a conductive nanofiller and dispersed into a flexible thermoplastic polyurethane (TPU) polymer matrix to prepare TPU/CNT composites for SLS processing pressure sensors. CNTs were first oxidized to prevent them from aggregating in the TPU matrix. TPU/CNT composites were preparedviasolution blending and ball milling methods, and the dispersion of the CNTs in the composites was observed by scanning electron microscopy. The thermal properties of TPU/CNT composites with different CNT content were measured, and processing parameters used in the SLS were determined based on differential scanning calorimetry measurements. SLS-processed TPU/CNT composites were prepared with different conductivity and piezoresistive properties. Percolation theory and piezoresistive performance results proved that a 0.25 wt% CNT-containing TPU/CNT composite showed the best pressure sensing ability, and it was successfully used as a sensor to detect plantar pressure distribution in a human foot.