Page 7 - Read Online

Huang et al. Soft Sci 2024;4:40 https://dx.doi.org/10.20517/ss.2024.37 Page 5 of 35

Carbon materials, such as carbon black, carbon nanotubes (CNTs), graphene, and reduced graphene oxide
(rGO), are known for their inherent electrical conductivity, excellent thermal conductivity, and low weight
[Figure 2C] [73-76] . However, they may present challenges related to dispersibility and compatibility with other
materials [77,78] . Moreover, as depicted in Figure 2D, zinc oxide (ZnO) [79,80] , organic/inorganic perovskites [81,82] ,
and transition metal dichalcogenides (TMDs) [83,84] have shown considerable potential for applications in
sensing and display modules of health monitoring systems.

Mechanical polymers
In textile electronics, mechanically flexible/stretchable polymers play an important role, especially as flexible
substrates, conductive fibers and encapsulation layers. The three-dimensional network structure of
polymeric matrixes can be used to carry, support and protect other materials, such as the previously
mentioned functional materials. In textile electronics, mechanical polymers should be selected based on
requirements for flexibility, stretchability, biocompatibility, and compatibility with functional materials.

For fabricating flexible substrates, there are some examples provided for consideration, such as using
[85]
polyimide (PI) as a substrate directly , coating polyvinyl chloride (PVC)/polyurethane (PU) on textiles to
[86]
be suitable for lithographic processes , and using polyethylene terephthalate (PET) fiber as a substrate for
coaxial configuration [87,88] . Besides, the polymers are employed for fabricating conductive fibers, such as Au
[89]
nanowires@styrene-ethylene/butylene-styrene (SEBS) , Ag nanoparticles@poly(styrene-block-
butadienstyrene) (SBS) , GO@PU , etc. Moreover, the polymers are employed for encapsulation layers
[91]
[90]
[93]
[94]
[92]
such as ecoffex , polydimethylsiloxane (PDMS) , PI , etc.
In addition to the functional materials and mechanical polymers, other materials are also employed to
enrich the functionality of textile electronics. For instance, pharmaceuticals are being embedded into fibers
to enable long-term therapeutic applications . Furthermore, efforts are underway to integrate antibacterial
[95]
materials into textiles to suppress or eliminate bacteria and provide additional protection for users ,
[96]
especially in scenarios where strict hygiene standards are crucial.

FABRICATION TECHNIQUES
Textiles are complex hierarchical materials requiring specialized knowledge of manufacturing processes. As
the fundamental units of textiles, fibers can be processed into yarns through twisting or texturing [97,98] . These
yarns can be crafted into fabrics using various techniques, including weaving, knitting, or bonding . Given
[99]
the importance of electrical performance in textile electronics, it is crucial to innovate and enhance the
fabrication techniques of textile electronics according to the framework of traditional textile production
processes. This section introduces fabrication techniques for functional fibers and fabrics, highlighting their
significance in developing textile electronics.

Fabrication of functional fibers
Surface treatment for commercial fibers
Conductive fibers are typically obtained through wire drawing, which involves elongating metal wires into
fiber forms. Metals such as stainless steel, copper, and aluminum are commonly used in this method. Fibers
with diameters ranging from a few to tens of microns can be fabricated by drawing the metal wires through
a series of precision dies [100,101] . However, most commercial fibers are primarily insulators [102-106] , so their
conductivity can be achieved by applying conductive materials via dip-coating [90,107] . Lee et al. employed this
technique for the fabrication of conductive fibers . In their method, theSBS polymer was immersed in a
[90]
silver-containing solution (AgCF COO). This immersion allowed for the infiltration of Ag into the SBS,
3
enhancing electrical conductivity of SBS. Thereafter, the silver nanowire (Ag NW)-coated fiber was coated