Sweat sensing in wearable sensor: A review of the future non-invasive technology for real-time health monitoring system

Wearable sensors are devices used in the diagnostic process for real-time health monitoring systems. Types of sensors are generally based on physical sensors and chemical sensors. However, the types of wearable sensors that are largely commercialized are limited to physical sensors. Some diagnostic processes generally use the blood collecting method to determine a patient’s condition. However, this method can cause adverse effects such as infection, pain, and bruising for some patients. Chemical-based wearable sensors are capable of detecting metabolic conditions in the body and can be an alternative to the existing method. Based on an approach using alternative analytes, sweat is the most frequently used because it is highly accessible and proceeds good parameters compared to the blood. Several studies related to wearable sensors using sweat have been done to increase convenience during the sampling process. Electrochemical, biosensor, and hybrid with several sampling methods, including microfluidic system, absorbent material, superhydrophobic-super hydrophilic surface, and iontophoresis, can be used for wearable sensor analysis method. Over the past decade, the characteristics of wearable sensors (i.e., selectivity, sensitivity, stability, and response time), textile materials, and biofuel cell technology for self-powered sensor development have also increased. From these classifications, it can be concluded that the method which is highly feasible to be developed is electrochemical wearable sensors that combine microfluidic and iontophoresis systems. The system is also expected to have stretchable material and is equipped with an integrated biofuel cell system that has the potential to be developed in our upcoming research topic.