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Page 10 of 35 Nam et al. Soft Sci 2023;3:28 https://dx.doi.org/10.20517/ss.2023.19

Figure 3. Soft conductive composites based on conducting polymers. (A) Schematic illustration of the topological supramolecular
network with a polyrotaxane (PR)-structure supramolecular additive and PEDOT:PSS (left). The conductivity of the polymer film with
increasing PR content (right). Reproduced with permission from ref [87] . Copyright 2022, The American Association for the
Advancement of Science; (B) Schematic illustration of the fabrication and interactions of the SACP (left) and an image depicting the
adhesion of the SACP film on the skin of the arm (right). Reproduced with permission from ref [83] . Copyright 2022, The Author(s); (C)
Schematic illustration of the solvent exchange strategy to produce the ultrafine PANI fiber in a modified wet spinning protocol (left).
Ashby plot comparing the mechanical strength of the ultrafine PANI fiber to previously reported conducting polymer fibers. Reproduced
with permission from ref [84] . Copyright 2022, The Author(s); (D) SEM image of the nanostructured PPy-CuPcTs hydrogel (left).
Electrochemical impedance plot of PPy-CuPcTs hydrogel compared with pristine PPy (right) and zoom in of the plot (right inset).
[90]
Reproduced with permission from ref . Copyright 2015, American Chemical Society. CuPcTs: copper
phthalocyanine-3,4′,4′′,4′′′-tetrasulfonic acid tetrasodium salt; DMF: dimethyl formamide; PANI: polyaniline; PEDOT:PSS:
poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate); PEG: polyethylene glycol; PPy: polypyrrole; SACP: self-adhesive conductive
polymer.

surface modifications, and comprehensive biocompatibility testing while adhering to regulatory standards
to ensure the safe integration of conductive polymers into soft wearable electronics.

The structural diversity and synthetic tunability of CPs enable molecular engineering, such as doping and
forming supramolecular networks. Therefore, CP-based composites are able to exhibit higher conductivities
than carbon-based nanocomposites and present new functionalities, such as micropatternability, self-
adhesion, and solution processibility. They also satisfy material requirements for bioelectronics, such as
superior electrochemical properties and biocompatibility. However, conductivities are still much lower than
those of metal-based nanocomposites. Further studies for material development are required to achieve
advanced devices using CP-based composites.

Soft conductive nanocomposites based on metal nanofillers
Metal nanofillers are one of the most studied types of fillers, as they exhibit high intrinsic conductivity (up
to 6 × 10 S·cm ) . Moreover, since metal nanofillers can be fabricated into desirable sizes, structures, and
-1 [93]
5
dimensions, they provide versatile features to the nanocomposites [94-96] . In this section, soft and conductive
nanocomposites based on various metal nanofillers are described, with details on how each form of
nanofiller affects the overall performance of the nanocomposites.

Among the different dimensions of metal nanomaterials, 0D nanoparticles are the most basic form that can
be rather easily synthesized with various metal elements . Numerous studies have been conducted on
[97]
fabricating nanocomposites with nanoparticles, especially with silver nanoparticles (AgNPs) that can be
readily synthesized and exhibit high intrinsic conductivity (6.3 × 10 S·cm ). For instance, Hyun et al.
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[98]
fabricated a nanocomposite of AgNPs and PEG in an ordered zigzag morphology [Figure 4A, left] . The