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Keum et al. Soft Sci 2024;4:34 https://dx.doi.org/10.20517/ss.2024.26 Page 5 of 32

Table 1. Comparison of stretchability, electrical conductivity (or sheet resistance), conductive materials, and the applications of
stretchable electrodes and interconnects
Sheet
Year Type Stretchability Materials Applications Ref.
resistance/Conductivity
4 -1
2019 Conductive 100% 7 × 10 S·m PEDOT:PSS Solar cell, OLED, [39]
Polymers 75 Ω·sq -1 electrochemical sensor
2018 Carbon-based 60% N/A Porous GHC/PDMS Stretchable LED [40]
-1
Nanomaterials 72 S·m
2023 Organic/inorganic 50% N/A PSS-attached eutectic Stretchable LED, pressure [42]
6 -1
hybrid type 2.2 × 10 S·m gallium-indium sensing systems for artificial
finger
-1
2022 1D/2D hybrid type 40% 24 Ω·sq AgNW/graphene Stretchable optoelectronics [44]
N/A
2022 Organic/inorganic 30% N/A PVP-treated AgNW Strain and temperature [41]
hybrid mesh and Au film sensing electrodes, antennas
2023 Liquid metal 24% N/A EGaIn Stretchable 4 × 4 micro-LED [37]
6 -1
3 × 10 S·m pixel array
2021 Liquid metal 1,000% N/A BGaIn Multilayer LED display, [35]
6 -1
2.06 × 10 S·m amplifier circuit, signal
conditioning board
-1
2022 1D metal nanofibers 100% 6.9 Ω·sq CuNWs ACEL display [27]
N/A
-1
2022 1D metal nanowires 30% 1.4 Ω·sq Ag/Au core-shell Breathable nanomesh devices [25]
N/A nanowires
2023 Metal particles 30% N/A Metallic particle Stretchable wireless pressure [31]
5 -1
5.94 × 10 S·m fillers/PDMS sensors, passive matrix LED
array
6 -1
2023 Metal particles 200% 1.54 × 10 S·m AgNPs Powering LED in flexible [29]
-1
0.65 Ω·sq electronic systems
PEDOT:PSS: Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate; PSS: polystyrene sulfonate; OLED: organic light-emitting diode; N/A: not
available; GHC: graphene honeycomb; PDMS: polydimethylsiloxane; AgNW: silver nanowires; EGaIn: eutectic gallium-indium; PVP:
polyvinylpyrrolidone; BGaIn: biphasic gallium-indium; CuNWs: copper nanowires; ACEL: alternative current electroluminescence; AgNPs: silver
nano-particles.
-1
6
crystalline solid mixture. The BGaIn electrode exhibited a high electrical conductivity of 2.06 × 10 S·m ,
stretchability of over 1,000%, and mechanical durability of up to 1,500 cycles. By utilizing a transfer-printing
process, it was possible to realize various stretchable circuits, including a multilayer structured LED device,
an amplifier circuit, and a signal monitoring board which can be applied to wearable sensing applications.
Furthermore, alternative LMs besides the EGaIn are also actively developed to improve the printing
[36]
characteristics and enhance bonding properties with substrates .
Metallic micro- and nano-particles
Additionally, stretchable conductive composites can be fabricated with conducting fillers such as metal
flakes, micro- and nano-particles, and LM particles (LMPs) embedded in stretchable elastomer materials.
One of the distinguished characteristics of these stretchable conductive composites is their function of
maintaining electrical conductivity under extreme stretching conditions, mainly due to the percolation
[31]
networks formed by the conducting fillers . Song et al. have developed photothermal lithography-
[31]
patterned stretchable conductors using Ag flake-based nanocomposites . The fabricated nanocomposite
conductor exhibited a high electrical conductivity of 5,940 S·cm and negligible resistance change
-1
(R/R = 40) under a 5,000 stretching cyclic test (30% strain). For the direct patterning, they used infrared
0
(IR) nanosecond pulsed lasers and stacked them into a multilayered circuit [Figure 4C(i)]. It is explained
that because of the different transmittance between Ag flakes and PDMS under IR irradiation, it was
possible to induce photothermal conduction curing of Ag flakes in selective areas of the nanocomposite. By
utilizing the stretchable nanocomposite as electrodes, a stretchable passive-matrix LED array was