Body-Area Capacitive or Electric Field Sensing for Human Activity Recognition and Human-Computer Interaction: A Comprehensive Survey

TL;DR

This survey addresses the gap in comprehensive guidance for body-area capacitive and electric-field sensing used in human activity recognition and human-computer interaction. It introduces a three-way taxonomy (body-part, whole-body, body-to-body), surveys hardware front ends and data-processing pipelines, and discusses robustness and generalization challenges. The work highlights practical sensing modalities, including active vs. passive operation, and signals from frequency, current, and time domains, while outlining future directions such as integrated capacitive chips, active shielding, sensor fusion, and subject-dependent continuous learning. The findings underscore the modality’s potential for low-power, low-cost, unobtrusive sensing with real-world impact in wearables, smart environments, and collaborative interfaces.

Abstract

Due to the fact that roughly sixty percent of the human body is essentially composed of water, the human body is inherently a conductive object, being able to, firstly, form an inherent electric field from the body to the surroundings and secondly, deform the distribution of an existing electric field near the body. Body-area capacitive sensing, also called body-area electric field sensing, is becoming a promising alternative for wearable devices to accomplish certain tasks in human activity recognition and human-computer interaction. Over the last decade, researchers have explored plentiful novel sensing systems backed by the body-area electric field. On the other hand, despite the pervasive exploration of the body-area electric field, a comprehensive survey does not exist for an enlightening guideline. Moreover, the various hardware implementations, applied algorithms, and targeted applications result in a challenging task to achieve a systematic overview of the subject. This paper aims to fill in the gap by comprehensively summarizing the existing works on body-area capacitive sensing so that researchers can have a better view of the current exploration status. To this end, we first sorted the explorations into three domains according to the involved body forms: body-part electric field, whole-body electric field, and body-to-body electric field, and enumerated the state-of-art works in the domains with a detailed survey of the backed sensing tricks and targeted applications. We then summarized the three types of sensing frontends in circuit design, which is the most critical part in body-area capacitive sensing, and analyzed the data processing pipeline categorized into three kinds of approaches. Finally, we described the challenges and outlooks of body-area electric sensing.

Figures (15)

• Figure 1: Three groups of work on the body-area electric field: sensing the body-part electric field (e.g. for gesture recognition) which mostly leverages the deformation of the existing instrumented electric field caused by the intrusion of that body-part; sensing the whole-body (or body-to-ground/environment) electric field (e.g. for motion detection) where a passive electric field varies during body-ground/environment action; sensing the body-to-body electric field for group interaction and cooperation recognition
• Figure 2: Active and passive body-area electric field sensing
• Figure 3: Lumped circuit model of body-area electric field sensing
• Figure 4: Sensing sources of body-area electric field sensing: frequency, Current and Time
• Figure 5: Applications leveraging the electric field existing/generated near the various body tissues