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Page 2 of 11 Li et al. Soft Sci. 2025, 5, 13 https://dx.doi.org/10.20517/ss.2024.60

Here, we propose a fibrous temperature sensor based on an optimized scalable ionic liquid immersion process. The
proposed sensor exhibited excellent temperature response characteristics, good linearity, a high sensitivity of
2.61%/°C, and can resist disturbances caused by pressing, bending, and twisting deformation. Moreover, it can
work normally in acidic and alkaline environments with good reliability and stability. To demonstrate its application
potential, we successfully integrated the sensor into firefighter suits, sports wristbands, and infant suits for real-
time temperature monitoring and early warning.

Keywords: Wearable electronics, functional fiber, temperature sensors, real-time monitoring, health care

INTRODUCTION
With the rapid development of flexible electronic technology, wearable sensors that can monitor real-time
human physiological information such as heart rate, pulse, respiration, and posture have emerged [1-10] .
Among various physiological parameters, human body temperature is a significant physiological indicator
widely used for assessing various diseases [11-13] ; for instance, it can promptly reflect the state of a patient’s
[14]
physical body during infection or inflammation . For individuals working in high-temperature
environments or in hot outdoor conditions, such as firefighters and athletes, monitoring body temperature
can help avoid skin burns, heatstroke, and a series of physiological issues caused by excessive body
temperature, such as dehydration, increased cardiac load, and damage to the liver and kidney [15,16] .
Therefore, real-time and long-term monitoring of body temperature is significant.

Various wearable temperature sensors have been developed to detect the temperature changes of the human
body or real-time temperature monitoring of specific parts [17-23] . Among them, fibrous temperature sensors
have attracted widespread attention due to their intrinsic characteristics, including ease of integration into
textiles and improved comfort and biocompatibility [24-32] . However, in human body temperature monitoring
scenarios, fibrous temperature sensors are subject to stress, bending, twisting, pH, humidity, and human
motion, all of which affect their detection sensitivity. Therefore, achieving fibrous temperature sensors with
high stability and resistance to external disturbances remains a challenge. Even though previous research
has reported that inserting the fabric in a coiled or S-shaped pattern could enhance the resistance of fibrous
temperature sensors to stress and strain [33,34] , this insensitivity is not an inherent characteristic of the device,
and its electrical performance may still change under external impact. Moreover, even slight temperature
fluctuations near physiological levels could cause severe body trauma, making high sensitivity a basic
requirement for real-time body temperature monitoring.

Herein, a fibrous temperature sensor with high sensitivity, excellent reliability and stability has been
developed. Continuous mass production of the sensor was realized through a scalable ionic liquid
immersion process. The fibrous temperature sensor is resistant to external stress and strain, barely disturbed
with bending and twisting deformation, and can operate normally in both acidic and alkaline environments,
effectively meeting the demands for human body temperature monitoring in various environments. For
applications in diverse scenarios, we integrated the sensor into the firefighting suits and designed a
multilayer temperature sensing system to monitor both firefighters’ body and ambient temperatures. This
system provides timely warnings of overheating in high-temperature and high-humidity environments.
Furthermore, we incorporated the fibrous temperature sensors into sports wristbands and infant suits,
enabling real-time monitoring of body temperature changes during human movement, as well as real-time
monitoring and early warning of infant fever.