  Haptic feedback is critical in a broad range of
human-machine/computer-interaction applications. However, the high cost and low
portability/wearability of haptic devices remain unresolved issues, severely
limiting the adoption of this otherwise promising technology. Electrotactile
interfaces have the advantage of being more portable and wearable due to their
reduced actuators' size, as well as their lower power consumption and
manufacturing cost. The applications of electrotactile feedback have been
explored in human-computer interaction and human-machine-interaction for
facilitating hand-based interactions in applications such as prosthetics,
virtual reality, robotic teleoperation, surface haptics, portable devices, and
rehabilitation. This paper presents a technological overview of electrotactile
feedback, as well a systematic review and meta-analysis of its applications for
hand-based interactions. We discuss the different electrotactile systems
according to the type of application. We also discuss over a quantitative
congregation of the findings, to offer a high-level overview into the
state-of-art and suggest future directions. Electrotactile feedback systems
showed increased portability/wearability, and they were successful in rendering
and/or augmenting most tactile sensations, eliciting perceptual processes, and
improving performance in many scenarios. However, knowledge gaps (e.g.,
embodiment), technical (e.g., recurrent calibration, electrodes' durability)
and methodological (e.g., sample size) drawbacks were detected, which should be
addressed in future studies.
