Electrically conductive textiles for health applications by carbon nanotube coatings on cotton

Recently, the demand for wearable conductive materials-featuring comfort, flexibility, lightweight, and stretchability-has prompted the growth of the electronic textile field. A research segment aimed at creating wearable electronics for various applications (e.g., sensors, energy harvesting, electromagnetic shielding, and energy storage) is focused on using carbon nanotubes (CNTs). However, applying CNT coatings uniformly to textiles poses challenges due to the nanotubes’ agglomeration. The sol-gel technique, which produces ceramic-based carbon composites with high electrical conductivity, has proven effective in overcoming this issue. In this study, non-functionalized CNTs with different aspect ratios were used to prepare two stable, homogeneous solutions for textile applications. CNTs were mixed with an amino-functionalized sol-gel precursor and a thermo-degradable surfactant that facilitated the dispersion and distribution of CNTs by acting on the π-π stacking interactions and maintaining their structure and conductive properties. The use of a polyurethane thickener led to CNT-based pastes, which were applied to cotton fabrics using the knifeover- roll method, producing electrically conductive textiles. Different chemical-physical techniques were employed to confirm the process’s success and assess the morphology and chemical composition of coatings. Electrical properties were evaluated by surface resistance measurements, demonstrating that a shorter CNT aspect ratio leads to higher conductivity at the percolation threshold. The electrically conductive CNT-based cotton fabrics, integrated with an optoelectronic system, acted as elements of signal transmission of biomedical data by reliably monitoring heart rates through photoplethysmography. This work highlights the successful combination of CNTs, the sol-gel process, and cotton fabrics, resulting in efficient and unobtrusive smart textiles suitable for various applications, including healthcare and sports.