# Advancements in Glucose Monitoring: From Traditional Methods to Wearable Sensors
## 6 Conclusions  
Glucose monitoring is crucial for individuals with diabetes as it helps in maintaining optimal blood sugar levels, preventing hyperglycemia or hypoglycemia, and minimizing the risk of long-term complications such as cardiovascular disease, nerve damage, and kidney failure [123]. With the advancements in latest technologies, several different glucose-sensing techniques has been developed such as optical [100], colorimetric [52], near-infrared [104], photoacoustic [107], and so on. Some of these technologies even enable painless sample collection from alternative biofluids, such as tears [130], saliva [30], and sweat [89], offering non-invasive solutions for continuous monitoring. Emerging innovations, including smart contact lenses [67], wearable sensors [82], and epidermal patches [82], aim to provide real-time glucose readings with high accuracy. Due to simpler approach and predictive accuracy, electrochemical glucose sensors became widely popular [38]. Despite their widespread use, electrochemical glucose sensors face issues \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Technologies** & **Advantages** & **Disadvantages** & **Measuring Site** & **Sensitivity** & **Cost** & **Ref.** \\ \hline Polymer & & & & & & \\ functionalized & Excellent reusability, & & & & & \\ graphene field-effect & maintaining its & & & & & \\ transistor & performance over 20 cycles & & & & & \\ (P-GFET) & & & & & & \\ \hline \end{tabular}
\begin{tabular}{c c c c c c c} \hline \multicolumn{1}{c}{\multirow{3}{*}{Fluorescence methods}} & \multicolumn{4}{c}{Photobleaching,} \\  & & autofluorescence, and & & & & & \\ signal fluctuations due & & & & & & \\  & & & & & & \\  & Non-invasive & & & & & \\  & measurement and & & & & & \\  & real-time monitoring & & & & & \\  & & & & & & \\  & & & & & \\  & & & & & & \\  & & & & & \\ \hline \multirow{3}{*}{Raman spectroscopy} & Non-invasive & & & & & & \\  & measurements, & & & & & \\  & sharp spectral features, and & & & & & \\  & signal multiplexing options & & & & & \\ \hline \multirow{3}{*}{Reverse iontophoresis} & Real-time monitoring and & & & & & \\  & low risk of infection & & & & & \\  & & & & & & \\  & & & & & & \\ \hline \multirow{3}{*}{Optical coherence tomography (OCT)} & Real-time monitoring, & & & & & \\  & high resolution, & & & & & \\  & and high penetration depth & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\ \hline Infrared absorption & Skin penetration up to & & & & & \\  & spectroscopy & 100 mm & & & & \\  & & & & & \\ \hline \multirow{3}{*}{Photoacoustic spectroscopy} & Faster response and & & & & & \\  & contactless & & & & \\  & & & & & \\  & & & & & \\  & & & & \\ \hline \multirow{3}{*}{Microwave} & Non-invasive, real-time & & & & & \\  & monitoring and & & & & \\  & flexible substrate & & & & \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._related to stability, interference, material biocompatibility, and so on [5]. Techniques like Ion-Selective Field-Effect Transistor (ISFET) [120] and extended gate electrode field-effect transistor (EGFET) [29] offer fast reproducibility but suffer from low sensitivity and electrical noise interference. Aiming to minimize the shortcomings of invasiveness, researchers started exploring various optical methods like fluorescence [8], Raman spectroscopy [72], optical coherence tomography [126], photoacoustic spectroscopy [129], and so on. The new age fluorescence method even offered visibility with affordable light sources such as ultraviolet (UV) or visible LEDs [50; 51; 52]. Raman spectroscopy offers sharp spectral features [12; 13; 14], and it can be further enhanced by incorporating SERS sensors with a high plasmonic response [9; 71; 81]. Reverse iontophoresis enables real-time monitoring with a low risk of infection, though it struggles with low glucose concentration in the interstitial fluid and interference from sweat or skin conditions [85].