Page 35 - Read Online

Wang et al. Soft Sci 2024;4:41 https://dx.doi.org/10.20517/ss.2024.53 Page 17 of 43

Table 5. Requirements for micro-cylindrical/fibric electronics in different applications
Mechanical
Application Biocompatibility Environmental adaptation Monitoring function Ref.
toughness
Wearable fibric Flexible; High biocompatibility Temperature/humidity change ECG; temperature; humidity; [108,
electronics stretchable resistance; vibration stability; pressure; strain 109]
mechanical deformations
Environmental Rigid; flexible; Medium High/low temperature resistance; Temperature; humidity; pressure; [110,
monitoring stretchable biocompatibility temperature/hu-midity change gas concentration; pH 111]
resistance; chemical corrosion
resistance
Micro-cylindrical Rigid High biocompatibility Temperature change resistance; Temperature; pressure; strain [112-
sensors for surgical vibration stability 114]
robots
Implantable probe Flexible Extremely high Chemical corrosion resistance; SEEG; temperature; strain; [34,
bioelectronics biocompatibility vibration stability glucose; neurotransmitter; oxygen 115]
partial pressure; cation
composition; pH
Interventional MRI Flexible High biocompatibility Strong magnetic field adaptability; 3D imaging [116,
resonant markers temperature change resistance 117]

ECG: Electrocardiogram; SEEG: stereo electroencephalogram; MRI: magnetic resonance imaging.

(e-skin), and human-computer interaction [108,118] . Desirable wearable sensors must exhibit excellent flexibility
and stretchability to accommodate the complex body structures and mechanical deformations encountered
during daily activities [119,120] . Conventional thin-film-based flexible e-skins predominantly utilize planar or
thin-film structures, and numerous studies have advanced their flexibility, conformity, and
multifunctionality [121-123] . For example, e-skins fabricated from ultrathin materials adhere closely to the skin,
enabling precise acquisition of biomechanical and bioelectrical signals . Additionally, research has
[124]
developed stretchable e-skins capable of capturing multiple physiological signals in dynamic
conditions [125-127] . Thin-film wearable sensors excel in signal acquisition accuracy, multimodal sensing, and
material ductility [128,129] . In contrast, fibers, characterized by their robustness, ease of handling, and
deformability, offer an ideal platform for integrating sensor devices [109,130] . Furthermore, fiber sensors can be
woven into flexible, deformable, and breathable textiles, further broadening their application scope. This
section will focus on wearable fibric mechanical sensors, as well as wearable fibric thermal sensors,
exploring their sensing principles, common structures, and typical applications in accordance with current
demand scenarios and major research trends.

Fibric mechanical sensors
Fibric strain sensors are capable of swiftly detecting physical responses and converting mechanical
deformations into electrical signals. These sensors exhibit fast response times, broad sensing ranges,
excellent compliance, and can be seamlessly integrated into textiles, making them highly suitable for
applications in human health monitoring and motion state detection. Fiber-based strain sensors can be
categorized by their sensing mechanisms into resistive , capacitive , piezoelectric , triboelectric ,
[132]
[133]
[134]
[131]
and optical types .
[135]
Resistive fibric strain sensors measure the magnitude of strain by detecting changes in resistance under
mechanical stretching. These sensors are widely used due to their simple structure and ease of
fabrication [58,108] . Huang et al. developed a highly flexible and sensitive strain sensor based on a composite
yarn for real-time effective recognition of sign languages. The performance of fiber sensors can be
[41]
enhanced through material processing and unique microstructural designs . For example, optimizing the
[136]
volume fraction of conductive nanofillers can improve sensitivity, while employing structural methods, such
as wrinkled or helical configurations, can expand the strain sensing range [120,137] . However, the viscoelastic