The road to a unique textile material: nanofibres with a pH-sensitive function

Colour changing textiles have recently gained much interest from the academic world. Although previously categorized as unwanted, colour changing textiles can be used in a broad field of applications since a colour change is a non-disturbing but clear signal which can perform a first warning function. This research focuses on halochromism or pH-sensitivity due to the importance of pH. These kind of materials can be applied in wound dressings, geotextiles, protective clothing etc. A halochromic wound dressing would for example be able to indicate the healing process of a wound since the pH-value varies during healing. Thanks to their extremely fine fibres, nanofibrous structures show interesting characteristics such as small pore size, high porosity and high specific surface area, which turn them suitable for a whole range of applications. Incorporating pH-sensitive dyes into nanofibrous structures would lead to unique materials that combine the intrinsic properties of nanofibres with an extra sensor functionality. As a start point, the feasibility of incorporating pH-indicator dyes in conventional textiles using standard dyeing processes was investigated. Next, the dyes were incorporated into a polyamide 6.6 nanofibrous structure by adding the dyes to the polymer solution before the start of the electrospinning process. The influence of this incorporation on the electrospinning process and the halochromic properties of the obtained structures were investigated. Our results proved that it is possible to develop a pH-sensor using conventional textiles dyed by a standard dyeing process. Also the incorporation of the pH-indicator dyes into a nanofibrous structure was possible. Moreover, the process parameters and fibre diameters were not influenced by this addition and reproducibility could be obtained. Furthermore, the majority of the obtained textile structures showed a clear colour change with a change in acidity. This halochromic behaviour was however different from the behaviour of the dyes in solution due to dye-fibre interactions