## 3 Results and Discussion
### Electrical Parameter Testing and Drug Detection
Structures with CO demonstrated higher values of electrical resistance in comparison with the analogous PET-based microfluidic chips. This is a result of larger amounts of deposited PANI/TiO\({}_{2}\) nanocomposite on the PET fabrics, as could be seen in Figure 2. However, the influence of the fabric structure should not be neglected. CO fabric has denser structure when compared to PET fabric, which can be noticed in Figure 4a,b. In spite of the hydrophobicity of PANI, the more open construction of impregnated PET fabrics enabled better fluid adsorption into the textile, which was proved by a simple drop test. A drop of distilled water immediately wetted the surface of impregnated PET fabrics, while impregnated CO fabrics took some time to get wetted. Taking into account that most of the microfluidic applications of textiles are based on the wicking phenomenon, which is strongly affected by pore geometry, number of fibers in the yarn, yarn linear density, and weaving pattern [44], combined with the fact that wickability and wettability are tightly related, it is very likely that the less-dense structure of PET fabrics positively influenced the transport of fluid through the impregnated PET fabrics and hence contributed to better conductivity mechanisms. Coating of both CO and PET fabrics with smaller amounts of conductive PANI/TiO\({}_{2}\) nanocomposite resulted in higher electrical resistance, whereas larger amounts of PANI/TiO\({}_{2}\) as a coating contributed to increased conductivity and, consequently, lower electrical resistance. This is due to the increased number of polarons and bipolarons in the structure and, consequently, improved conductivity. PANI/TiO\({}_{2}\) nanocomposite coating creates an efficient network for charge transport in the PANI matrix and, accordingly, a better conduction mechanism can be achieved. The decrease in resistance with an increase in the concentration of CPA was more prominent in the samples impregnated with smaller amounts of PANI/TiO\({}_{2}\) nanocomposite (CO-PANI/TiO\({}_{2}\)-1 and PET-PANI/TiO\({}_{2}\)-1). The same trend was reported in reference [22]. The artificial sweat solution consisted of several ions: Na\({}^{+}\), K\({}^{+}\), Cl\({}^{-}\), and lactate ions. It is very likely that an increase of CPA concentration in artificial sweat solutions led to an increase of the concentration of Cl\({}^{-}\) ions originating from CPA [45], contributing to better conductivity and consequently resulting in a decrease of electrical resistance on the terminals of the proposed component. However, their influence seems to be weaker in the case of samples that were impregnated with larger amounts of PANI/TiO\({}_{2}\) nanocomposite. In order to quantitatively determine the sensing performance of the studied samples, two metrics were taken into account--sensitivity and linearity, which are both important for the applicability of the proposed platform. In our case, the sensitivity is defined as \(|S|=\Delta\,R/\Delta\,C\), where \(\Delta\)\(R\) is variation of resistance and \(\Delta\,C\) is change in CPA concentration from 0 to 6 \(w/v\%\). As a measure of goodness of linear fit, R\({}^{2}\) (coefficient of determination) was used. These two parameters are presented in Table 1 for the four analyzed textile-based structures. Figure 5: (**a**) Resistance as a function of frequency for PET-PANI/TiO\({}_{2}\)-1 and for different fluids soaking the fabric; (**b**) Resistance as a function of cyclophosphamide (CPA) concentration for different fabrics. It can be concluded from Table 1 that sample CO-PANI/TiO\({}_{2}\)-1 demonstrated the highest sensitivity but the lowest linearity. From a practical applications point of view, some kind of compromise should be achieved between these two performance indicators by tuning of the PANI/TiO\({}_{2}\) nanocomposite amount on the fiber surface. For example, the sample PET-PANI/TiO\({}_{2}\)-1 demonstrated the highest linearity and acceptable sensitivity.