# Applications of Nanomaterials in RFID Wireless Sensor Components
## 5 Applications
### Healthcare  
Measuring physiological signals and automatically diagnosing them, mobile healthcare that provides medical services freely without being constrained by time, space, or location is currently attracting significant attention. Wireless sensors collect the patient's bio and environmental information, allowing real-time and organic feedback to the overall healthcare system [147]. [PERSON] et al. proposed a wireless sensor tag capable of analyzing gases, ions, bacteria, and more [112]. As shown in Figure 11a, when the concentration of the analyzed substance exceeds the threshold marked by the red line, the smartphone recognizes it and can read the corresponding value. By varying the resistance of the rheostat within a single tag, various threshold values can be set without the need for multiple tags. Graphene-coated carbonic interdigitated electrodes grown by chemical vapor deposition (CVD) were used for ethanol detection. The graphene exposed to the target gas undergoes a change in impedance by physically adsorbing gas molecules. Potassium chloride ions and _Staphylococcus aureus_ bacteria were detected through gold and platinum electrodes, respectively. The sensor demonstrated low limits of detection (LOD) of 1 ppm for ethanol, 0.009 M for KCl, and 105 CFU/mL for bacteria, showing excellent linearity and sensitivity, effectively detecting various biochemical substances. Glucose monitoring is recognized as a powerful tool for early diagnosis of diabetes. [PERSON] et al. proposed a biosensor for non-contact detection of glucose concentration based on a RFID system [148]. The sensor tag is fabricated by integrating a capacitor produced by Cu plating and a PDMS microchannel providing excellent biological characteristics and compatibility onto a glass substrate. The tag exhibits variations in permittivity based on the presence and concentration of glucose, altering the effective capacitance of the Cu-based squared spiral capacitor. Glucose, with its relatively higher molecular weight compared  
Figure 9: (**a**) A hydrogen smart sensor system based on Pt/graphene fixed RFID tag [65]. (**b**) Passive chipless CO\({}_{2}\) sensor using ZnO/CuO/rGO nanocomposites at room temperature [116]. (**c**) Organic conductive nanocomposite paste-based high-sensitivity wireless NO\({}_{2}\) gas sensor composed of multi-dimensional Fe\({}_{2}\)O\({}_{3}\) hollow nanoparticles [117]. to water molecules, induces a viscous effect that interferes with the rotation of the AC field, resulting in changes in permittivity. Based on this mechanism, the reader induces reflection parameters, generating deviations in resonance frequency, thereby achieving glucose detection. The glucose sensor demonstrates larger shifts in resonance frequency with increasing glucose concentrations within the range of 25 mg/dL to 600 mg/dL, proving excellent linearity. The RFID-based bio-sensor tag, composed of a PDMS channel and a copper-based spiral capacitor, has successfully achieved non-contact glucose detection. Ongoing research is actively exploring further advancements in glucose detection. [PERSON] et al. developed a wearable sweat pH monitoring sensor that can maintain contact even with human movements (Figure 11b) [119]. Since sweat contains valuable information such as glucose, lactate, and cortisol, reflecting the intensity of physical activity and dehydration levels, its analysis is highly beneficial for health assessment. The researchers manufactured pH-sensitive electrodes at low temperatures, selecting a graphite-polyurethane composite for flexibility and rapid responsiveness to analyze sweat. This led to effective pH monitoring with a high sensitivity of 11.13 \(\pm\) 5.8 mV/pH on a wearable substrate. [PERSON] et al. implemented a sensor with LEDs attached to the resonator of an NFC sensor circuit, enabling intuitive understanding of the user's state (Figure 11c) [127]. They structured hydrogel as an interlayer, advancing RF resonators to wearable applications without rigid materials.