## 3 LIG-Based Wearable Systems for Multifunctional and Intelligent HCI
### Soft and Stretchable Gesture HCI System  
To realize a closed-loop HCI function, the wearable HCI system not only needs sensitive and multi-mode sensing ability, but also execution ability. A device that can act as both a multi-mode motion sensor and a motion actuator is highly valuable for achieving a low-cost, multi-functional, and highly efficient motion HCI system.  
[PERSON] et al. proposed LIG-based soft and stretchable electronics with a PI/PDMS substrate for multi-mode sensing and human-machine interaction [30]. Even though the system has three main applications (voice and motion sensors, gesture recognition gloves, and remotely controlled soft robots), as illustrated in Figure 16, all of the core components of the system were fabricated using the following method. This involved incorporating PI particles with a specific concentration into a PDMS solution, curing the mixture, and exposing the PI/PDMS substrate to an infrared laser to produce the porous LIG layer, which then resulted in the creation of the LIG-based multifunctional device. Moreover, the electromechanical properties of the device could be adjusted flexibly by adjusting the laser flux. Based on the softness and stretchability of the PI/PDMS substrate, the LIG-based wearable system could sustain a mechanical tension of over 15%, which was more suitable for wearable motion monitoring than the system with the PI substrate.  
Due to its high sensitivity, good tensile properties, and good electrical performance, this sensor can effectively monitor various physiological signals such as pulse, voice, motion, etc. For motion interaction and remote-control applications, a soft glove was made by placing the PI/PDMS mixture into a glove mold, and a LIG-based sensor was fabricated by laser direct writing on each finger knuckle (including the metacarpophalangeal point, the proximal interphalangeal point, and the distal interphalangeal point). The glove could  
Figure 16: The LIG-based soft and stretchable electronics for gesture HCI system. Reproduced with permission from [30]. Copyright 2022 Springer Nature.  
realize the accurate detection of gestures and hand movements, which is suitable for gesture HCI. Furthermore, by combining the LIG-based soft robot (which is based on the LIG-based motion actuator) with the glove, the realized motion HCI system could realize a closed-loop gesture interaction. The soft robot was driven by LIG and controlled by electric heating. Since PDMS and PI have different thermal expansion coefficients, the device can be deformed at different angles thanks to the heat generated by the LIG. The HCI system can feel the changes in human gestures through the LIG-based glove, and transmits the control signals to the thermal actuator based on LIG. The processing unit then processes the signals, enabling the deformation control of the soft robot and accomplishing remote motion control.  
This study holds significant importance for the realization of robot remote control systems. The proposed multifunctional HCI system has good potential for function expansion and is expected to achieve a wide range of applications in the field of multi-purpose intelligent motion HCI.