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Huang et al. Soft Sci 2024;4:40 https://dx.doi.org/10.20517/ss.2024.37 Page 19 of 35

different types of eye movement [183] . Reprinted with permission. Copyright 2019, IOP Science. PEDOT:PSS: Poly(3,4-
ethylenedioxythiophene)-poly(styrenesulfonate); ECG: electrocardiograms; EMG: electromyography; EEG: electroencephalographic;
EOG: electrooculogram.

connected to a battery and an OpenBCI board to record EEG waveforms. The EEG signals are then
displayed on a laptop using the OpenBCI GUI software via a Bluetooth module. Notably, these textile
electrodes enable skin contact without the requirement for conductive gels and exhibit robust stability in
EEG signal acquisition, even following multiple wash cycles and bending.

Electrooculogram (EOG) records the electrical activity linked to eye movements, serving as a valuable
diagnostic tool for investigating the visual system and analyzing sleep patterns. As shown in Figure 7G, a
smart headband using graphene is used for EOG signal monitoring. The graphene textile electrodes are
secured in an elastic headband with adhesive foams by a metallic snap fastener. The EOG-based human-
computer interaction interface is obtained by a front-end readout circuit and a smart headband for signal
acquisition, a microcontroller unit for processing signals, and a laptop computer for display. Furthermore,
an automated algorithm has been developed to detect and classify ocular movements [Figure 7H]. The
integration of the algorithm with the bright headband has expanded its applications in human-computer
interaction and human-machine interfaces, achieving impressive recognition accuracies ranging from 85%
to 100%.

Additionally, variations in human body temperature are indicative of metabolic activity and can reflect
pathophysiological information [226,232] . Zhang et al. fabricated a thermosensitive micro/nanoporous fiber with
an unprecedented high thermal sensitivity (β = 4,994.55 K, α = -5.58%/K at 26 °C) and the fastest response/
recovery times (97/239 ms) recorded for textile-based temperature sensors . The fiber was achieved by
[233]
growing Fe (MoO ) nanostructures on graphene using a wet spinning method. Compared to the
4 3
2
conventional direct mixing of Fe (MoO ) and graphene, the fibers produced by this method exhibit
2
4 3
enhanced thermal sensing performance. The core thermoresistive micro/nanoporous fiber strand acts as
both the temperature sensor and the working electrode of the textile TENG. The output signals are
displayed on a mobile phone screen through a wireless system that includes an analog-to-digital conversion
module, Bluetooth, and an accompanying app. Ultimately, real-time wireless monitoring of body
temperature and pulse is achieved through textile electronics.

Respiratory rate, a vital sign, varies with age, health status, and activity levels. Anomalies in respiratory rate
could be symptomatic of various conditions, including cardiac, pulmonary, metabolic disorders, or
infections . In respiratory rate monitoring systems, the humidity sensors and pressure sensors are
[234]
[235]
[227]
fundamental and critical components. For instance, Lin et al. developed a pressure sensor based on ultrasoft
helical functional fibers, demonstrating high sensitivity (1.726 V/N) and rapid response time (20 ms) .
[236]
They have successfully developed a real-time respiratory monitoring system, which includes a pressure
sensor, an analog-to-digital conversion module, and a signal processing unit, and utilizes LabView software
for further data processing. The system can continuously record vital parameters such as respiratory
intensity, frequency, and intervals.

Biochemical monitoring
Sweat, as a biological fluid, provides a wealth of health-related biomarkers [237-239] . The rapid production and
[240]
renewal rate of sweat implies that it can provide nearly real-time information on physiological status .
Therefore, long-term continuous monitoring of sweat can help track the trend of individual health status
changes and detect abnormalities in time.