# Conductive Textiles for Signal Sensing and Technical Applications
## 2 Materials Used to Impart Conductivity on Textiles
### Deposition Method
#### 3.1.1 Vapor Deposition  
Highly pure and high-performing solid materials, such as metal, nanotubes, and ICP, are deposited as thin films of one or several layers [138]. The deposition of thin perovskites is a thin film based on organo-inorganic materials, such as CH\({}_{3}\)NH\({}_{3}\)PbX\({}_{3}\) (X = I\(-\), Br\(-\), Cl\(-\)), which has fascinating optical and electronic properties [139]. A film of solid and liquid through vapor deposition without solvent has been investigated. In vapor deposition, vapor can be condensed by two processes: (a) physical condensation or (b) chemical reaction; furthermore, depending on these two processes, vapor deposition is classified by: (i) physical vapor deposition (PVD) and (ii) chemical vapor deposition (CVD) [140].  
1. Physical Vapor Deposition (PVD)  
PVD was developed to address the capacity to create a layer with continuous electrical conductivity and the ability to create an element with a specific geometry and dimensions, which is not possible in conventional layering technology such as printing, dipping, etc. [141]. PVD is a process of applying a fine coating of conductive materials on the textile substrate by the vaporization process. PVD comprises four steps: (a) production of vapor phase by evaporation of target materials, (b) transportation of the vapor to the substrate, (c) reaction between the metal atoms and the appropriate reactive gas, and (d) condensing vapor on the surface of the substrate [51; 142; 143]. PVD can be deposited in almost all materials, such as pure metal, metal, and organic material mixtures such as glasses, alloys, compounds, and layer systems [144]. [PERSON] et al. studied the PVD of aluminium on bare Kapton and when it was coated with PVC/PU [145]. The PVC-coated substrate was the best among the samples for making flexible electronics. Depending on the deposition technique, PVD can be classified by evaporation techniques (vacuum thermal evaporation, electron beam evaporation, laser beam evaporation, pulsed electron deposition, arc evaporation, molecular beam epitaxy, ion plating evaporation) [146] and the sputtering technique [147; 148; 149]. A silver coating was deposited on cotton fabric using PVD (vacuum thermal evaporation) with a Flexicoat 850 coating apparatus to impart conductivity [150]. The same process was used to deposit a nano-coating of Al and Zn on cotton fabric, with Zn coating having a greater EMI shielding performance than Al-coated cotton fabric [151].  
Sputtering is a non-thermal physical vapor deposition technique where molecules move from the surface of the material through the knocking of high energy particles. Molecules that emerge from the target material by the shell firing of high energy particles on the material are condensed on the surface of the substrate to deposit a thin film of the target material [152]. [PERSON] et al. investigated DC magnetron sputtering of an Ni-Fe/Cu multi-layer (500 nm Ni-Fe/500 nm Cu) thin film to impart conductivity and led to an EMI shielding effect in the range of 0.7 GHz-6 GHz, which is a better EMI shielding effect than a pure Ni-Fe and Cu layer [153]. Sputtering deposition of Cu metal is used to make ECG electrodes for biomonitoring smart wear [154]. [PERSON] et al. reported the very first PVD of amorphous carbon-coated 3D NiCo\({}_{2}\)O\({}_{4}\) on carbon cloth to make a binder-free flexible electrode with high dimensional and cyclic stability (535.47 mAhm\({}^{-1}\) at 500 mA g\({}^{-1}\) for 100 cycles) capacity and electrochemical performances [155]. A better electrochemical performance was found for NiCo\({}_{2}\)O\({}_{4}\)/NiO/C composites on carbon cloth obtained by magnetron sputtering PVD of NiCo\({}_{2}\)O\({}_{4}\) nanowires/NiO nanoflakes with cyclic stability (1051 mAh g\({}^{-1}\) for 100 cycles at 100 mA g\({}^{-1}\)) [156].