# Fiber-Based Sensors and Energy Systems for Wearable Electronics
## 3 Fiber-Based Sensors  
In this chapter, we introduce fiber-based tactile sensors, chemical sensors, photosensors, and temperature sensors. These sensors can detect changes in physiological and external environmental factors in real-time. The fabrication methods, materials, and sensing and mechanical properties of these fiber sensors are summarized in Table 2.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Methods** & **Categories** & **Advantages** & **Disadvantages** & **Ref.** \\ \hline Coating & Dip-coating & Simple, fast & Low sensitivity, poor mechanical stability, large solution consumption & [12, 30, 31, 32, 33] \\ \hline \multirow{4}{*}{Spinning} & Wet-spinning & Good mechanical stability & Complex, long manufacturing time, solvent dissolvable & [34, 35, 36, 37, 38] \\ \cline{2-5}  & Dry-spinning & No need to purification, high productivity & Toxic volatile solvent, low mechanical stability & [39] \\ \cline{2-5}  & Melt-spinning & Simple, low cost, does not require solvents & Low concentration of active materials, high temperature & [40, 41, 42] \\ \cline{2-5}  & Electrospinning & High mechanical stability & High voltage, small area & [43, 44, 45, 46] \\ \hline \multirow{4}{*}{Deposition} & Chemical Vapor & High sensitivity, strong substrate bonding & Uncontrollable thickness, particulate contamination & [47, 48] \\ \cline{2-5}  & Electrodeposition & High conductivity, low cost & Poor mechanical stability, long manufacturing time & [49] \\ \hline \multirow{2}{*}{Drawing} & Thermal Drawing & High sensitivity, simple, fast, high productivity & Limited materials & [25, 50, 51, 52, 53] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of common fabrication methods for fiber-based electronics.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Application** & **Target** & **Materials** & **Fabrication Methods** & **Sensing Properties** & **Mechanical Properties** & **Ref.** \\ \hline \multirow{3}{*}{Tactile sensing fiber} & Strain & Cotton fabric-SWCNT & Dp-coating & GF = 578 Up to 100\% strain & 8 washing cycles with 35\% & [9] \\  & & & & & resistance increase & [9] \\ \cline{2-6}  & Strain & Slave-coated nylon filter Cotton Fiber & Core-spinning & GF = 0.695 Up to 14\% strain & Stable CF after 10,000 cycles of 15\% strain & [54] \\ \cline{2-6}  & Pressure & PVDF-BaTiO\({}_{3}\) & Electrospining & 17 mV/A/Pa Up to 40 kHz pressure & Stable current output after 1790 cycles & [43] \\ \hline \multirow{3}{*}{Cherical screening fiber} & Hydrogen peroxide & See\({}_{3}\) & TDP & Sensitivity: 0.176 \(\pm\) 0.005 mV ppm\({}^{-1}\) & - & [53] \\  & & & & Limit of detection (LOD): 10 ppb & - & [53] \\ \cline{2-6}  & NO\({}_{2}\) & Metal-organic frameworks coupled with MWCNTs & CVD & LOD: 100 ppb & Bonding angle \(<\) 120\({}^{\circ}\) & [47] \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & Glucose & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & & \\ \cline{2-6}  & & & & & & & \\ \cline{2-6}  & & & & & & & \\ \cline{2-6}  & & & & & & & \\ \cline{2-6}  & & & & & & & \\ \cline{2-6}  & & & & & & & \\ \cline{2-6}  & & & & & & & \\ \hline \multirow{3}{*}{P Photosensing fiber} & Lenses imaging & & & & & & \\ \cline{2-6}  & and scanning & & & & & & \\ \cline{2-6}  & UV monitoring & p-Cu/Zn/Fe/n-TiO\({}_{3}\) with CNTs & Deposition & Sensitivity: 460 A W\({}^{-1}\) & 200 bending cycles under 60\({}^{\circ}\) & [58] \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \hline \multirow{3}{*}{Temperature sensing fiber} & Temperature & ROO & Wet-spinning & Response time - 7s & Resource time - 20 s & \\ \cline{2-6}  & & & & Range: 30-80\({}^{\circ}\) & 10,000 bending cycles & [58] \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \cline{2-6}  & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Summary of fiber-based sensors.