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Xi et al. Soft Sci 2023;3:26 https://dx.doi.org/10.20517/ss.2023.13 Page 25 of 34

chemical corrosion. For many reasons, the sensor may not be reused, such as health and safety, avoiding
cross infection, or the chemical reaction of the sensor is irreversible and cannot be reused. In the future,
solutions such as using more durable materials, improved sensor packaging, and better sensor packaging
may help improve the durability and reliability of self-powered wearable sensors. In addition, the
development of more sustainable and environmentally friendly materials and manufacturing processes can
also help reduce the impact of sensors on the environment.

The accuracy and calibration of the self-powered wearable sensor is the key factor in determining the
reliability and usefulness of the collected data. In most application scenarios, we need to pay attention to the
accuracy and calibration of sensors, which are prone to many problems. Due to changes in the environment
or inherent sensor characteristics, self-powered wearable sensors may have calibration drift over time.
Manufacturing variations and environmental factors may cause performance differences among multiple
sensors, leading to inconsistent data collected by different sensors. Additionally, self-powered wearable
sensors may be subject to interference from other sources, such as electromagnetic radiation, or
environmental factors, such as humidity or temperature. At present, there is still a lack of standardization in
self-powered wearable sensors. Although this is partly because sensors in the high-tech field need time and
experience to develop standards, it may still lead to inconsistent data collected between different sensors or
different studies. These problems may lead to inaccurate measurement results, reduce the application range
of the sensor, or require professionals to adjust before each use. In the future, calibration, validation, and
data analysis using standardized protocols may become a solution. Developing more accurate and reliable
sensor technology will also help improve the accuracy and reliability of self-powered wearable sensors. In
addition, employing reasonable data analysis technology can help solve some problems related to calibration
drift, inter-sensor variation, and interference.

CONCLUSIONS
This review summarizes the research progress in the application status, material function, working mode,
technical means, and application fields of self-powered wearable IoT sensors in the human-machine
interface. Mainly but not limited to using multiple electronic databases such as Web of Science and Scopus
to conduct a comprehensive literature search. Through combing and analyzing the literature, this study
found that self-powered wearable IoT sensors, as an important technical means of human-machine
interfaces, have been widely used in medical monitoring, virtual reality, smart home, and other fields and
have great application potential and commercial value. The role of materials in self-powered sensors mainly
includes converting external energy into electrical energy, improving energy utilization efficiency, extending
service life, and other related aspects. Their working modes include various forms, such as physical sensing,
chemical sensing, and hybrid sensing. At the same time, the technical means of self-powered sensors are
constantly being innovated and applied, including TENGs, PENGs, thermoelectric nanogenerators, biofuel
cells, solar cells, and machine learning. Finally, this study summarizes the application prospects and
limitations of self-powered wearable IoT sensors as a human-machine interface, which provides an
important reference for further research and application. The limitations of this review mainly include the
following parts. Firstly, the data reviewed in this paper mainly come from published academic literature and
patents, which may introduce deviations or overlook certain studies. Moreover, most of the included studies
are based on experiments conducted under controlled room conditions. Additionally, while this article
briefly mentions some relevant technical details and future research directions, it lacks an in-depth
discussion on these aspects. These limitations will affect the comprehensiveness and depth of this review
and need to be improved and perfected in future research. To sum up, despite the aforementioned
limitations, this paper provides a relatively comprehensive and systematic review and analysis of the
application of self-powered wearable IoT sensors as human-machine interfaces, which serves as a valuable
reference for a certain basis for research and application in related fields. Overall, the self-powered wearable
sensor, serving as the human-machine interface in the IoT domain, holds great potential and represents a