## 2 LIG-Based Wearable Systems for Multifunctional and Intelligent Health Care
### Multifunctional Sensing System with an Anti-Interference Design  
Multifunctional sensing systems are of great significance in health monitoring. In order to accurately measure multiple physiological signals, it is crucial to eliminate any interference between them.  
[PERSON] et al. invented a double-sided wearable system that both enables multi-modal sensing and avoids the interference between various signals [20]. Figure 7 shows the structure diagram of the system. The system allows for multi-modal sensing of the electrophysiological signals (ECG, EMG, etc.), mechanical stimuli/movements (strain, pressure, proximity), concentrations of sodium ions (Na\({}^{+}\)), hydrogen ions (H\({}^{+}\)), acetone gas, and nitrogen dioxide (NO\({}_{2}\)), and has an energy collection and storage unit. The structure of the double-sided system enables the placement of skin-interacting sensors such as body temperature, electrophysiological, and ion sensors on the inside, while motion, room temperature, distance, and gas sensors, which interact with limbs and the external environment, are placed on the outside.  
To enhance the system's anti-interference capabilities, several measures were taken. First, the locations of the sensors and power units followed the anatomy of the muscles and joints of the human hand. For example, the EMG sensors were located on the thenar area where muscles are relatively active, and the ion sensors were located on the palm where it is easy to collect a large amount of sweat. Second, serpentine interconnection was used between each module to alleviate the noise caused by the movement of the wearer while minimizing the impact on the wearer's comfort. Third, through the design of the LIG processing technique, different LIG-based sensors adopted customized process parameters to satisfy the requirements of sensing performance while alleviating the interference on sensors caused by external strain. Fourth, because many sensors are sensitive to temperature, to eliminate the influences of temperature, an important step is to test the temperature response of different sensors. After that, the temperature sensor contained in the system was used to record the temperature change in real-time, and the temperature compensation was used to eliminate the temperature drift from the test results to obtain reliable physiological signals. Finally, to eliminate the interferences of proximity, moisture, static electricity, and normal pressure on the sensing performances, the use of encapsulation is an effective approach. Gas sensors and physiological electrodes were designed to be resistant  
Figure 7: The multifunctional sensing system with an anti-interference design. Reproduced with permission from [20]. Copyright 2022 American Chemical Society.  
to proximity and pressure, while other sensors were packaged using Ecoflex to protect them from moisture and chemicals. Furthermore, in chemical sensors, their packages should have small windows so that the sensors can interact with the test objects.  
With the help of the above measures, the LIG-based wearable system realized in this work had a rich multi-mode signal monitoring ability and strong anti-interference ability compared to the previous work. Most significantly, its anti-interference ability, self-powered ability, and multi-mode signal monitoring ability enabled it to have great functional expansion space and wide application prospects. To further construct an information closed-loop wearable system to realize a complete information collection-transmission-processing-feedback function, we introduce a method to realize information feedback to wearers in the next section.