## 3 Results and Discussion
### Electrochemical Studies
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Electrode** & **Morphology** & **Synthesis** & **Specific** & **Cyclic Stability (\%)** & **Ref.** \\
**Material** & **Morphology** & **Method** & **Capacitance** & **(No. of Cycles)** & **Ref.** \\ \hline
**In\({}_{2}\)S\({}_{3}\)** & 2D Layered & Solvothermal & 897 F\(\cdot\)g\({}^{-1}\) & 90.81 (10,000) & [11] \\ \hline
**Indium Oxide** & Mesoporous & Hydrothermal & 320 F\(\cdot\)g\({}^{-1}\) & 86 (3500) & [43] \\ \hline
**In\({}_{2}\)O\({}_{3}\)** & Nanowires & Chemical Vapor & 16.6 mF\(\cdot\)cm\({}^{-2}\) & 66.8 (1000) & [61] \\ \hline
**In\({}_{2}\)O\({}_{3}\)** & Thin Layer & Atomic Layer & Deposition & 1.36 mF\(\cdot\)cm\({}^{-2}\) & 47.8 (2000) & [62] \\ \hline
**Indium Tin Oxide** & Nanowires & Magnetron & 956 F\(\cdot\)g\({}^{-1}\) & - & [63] \\ \hline
**In\({}_{2}\)O\({}_{3}\)/carbon** & Aggregated & Sol-Gel Approach & 287 F\(\cdot\)g\({}^{-1}\) & 86 (5000) & [64] \\ \hline
**In\({}_{2}\)O\({}_{3}\)/rGO** & Aggregated & Chemical Reaction & 178.8 F\(\cdot\)g\({}^{-1}\) & 93.7 (5000) & [65] \\ \hline
**In\({}_{2}\)O\({}_{3}\)** & Nano discs & Hydrothermal & 622 F\(\cdot\)g\({}^{-1}\) & 97 (10,000) & [66] \\ \hline
**In\({}_{3}\)** & Layered & Liquid Phase & 27.2 F\(\cdot\)cm\({}^{3}\) & 88.7 (10,000) & [67] \\ \hline
**M-In\({}_{2}\)O\({}_{3}\)** & Nanoflake & Cation substitution & 404 F\(\cdot\)g\({}^{-1}\) & 96 (5000) & [68] \\ \hline
**InVO\({}_{4}\)** & Microspheres & Hydrothermal & 1710 F\(\cdot\)g\({}^{-1}\) & 94 (4000) & [69] \\ \hline
**graphene/ In\({}_{2}\)S\({}_{3}\)** & Nanosheet & CVD+ & 530.7 F\(\cdot\)g\({}^{-1}\) & 84 (20,000) & [70] \\ \hline
**INS1** & 2D Layered/ & & & & \\
**In\({}_{2}\)S\({}_{3}\) + SWNT** & Cocoon Shape & Solvothermal & 1268 F\(\cdot\)g\({}^{-1}\) & 92.1 (10,000) & This Work \\ \hline
**INS5** & 2D Layered/ & & & & \\
**In\({}_{2}\)S\({}_{3}\) + SWNT** & Cocoon Shape & Solvothermal & 970 F\(\cdot\)g\({}^{-1}\) & 97.8 (10,000) & This Work \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of electrochemical characteristics of previously reported indium-based electrode materials and current work. The wireless powered BLE/PPG module includes four different parts, (1) a power receiving antenna, (2) a power controller for voltage regulation, (3) a micro control unit (MCU) for Bluetooth communication, and (4) an oximeter for measuring the biosignal (Figure 7b). After connecting the SSCs to the wireless powered BLE/PPG module, the device was placed on the NFC-based wireless power transmitter (nRF52-DK with Radio Frequency Dev Kit, Nordic Semiconductor and STMicroelectronics, respectively) to supply wireless power, as shown in Figure 7c. An integrated system was the most effective option when the wireless devices required momentary higher power than the supplied power for sending data to other wireless devices. Figure 7d shows the current flow of the wireless powered BLE/PPG module with (and without) a supercapacitor. Without a supercapacitor, the system operation failed when sending data due to low supplied power. On the other side, the system shows stable operation without fail with a supercapacitor. A supercapacitor can store the energy with extra power while measuring biosignals. Moreover, the supercapacitor provides momentary high power while sending data via Bluetooth as temporary energy storage. Figure 7d shows a circuit diagram regarding the connection between the wireless powered module and SSC. A 5 V output pin from the power controller was connected to two input pins, (1) an anode pin of SSC for charging when the consumption power of the BLE/PPG module was less than the supplied power, and (2) the input of a 3.3 V voltage regulator for discharging to supplement the insufficient power while sending data via Bluetooth. The current consumption property of the wireless powered BLE/PPG module with (and without) a supercapacitor is shown in Figure 7f. The device without SSC failed in operation as it failed to initialize due to the lack of high power required during the initialization.