1 INTRODUCTION  
1.1 Background  
1.2 Related Surveys  
1.3 Paper Aims and Contribution  

2 TAXONOMY  
2.1 Active and Passive Sensing Mode  
2.2 Load, Transmit and Shunt Operating Mode  
2.3 Frequency, Current and Time Sensing Sources  

3 ELECTRIC FIELD SENSING WITH DIFFERENT INVOLVED BODY FORM  

4 APPLIED HARDWARE AND DATA PROCESSING PIPELINE  
4.1 Applied Hardware Sensing Front End  
4.2 Applied Data Processing Method  

5 CHALLENGES  
5.1 Robustness  
5.2 Generalization  

6 OUTLOOKS  
6.1 Integrated Capacitive Chips  
6.2 Active Shielding  
6.3 Sensor Fusion  
6.4 Subject-dependent Continuous Learning  

7 CONCLUSION