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Ma et al. Soft Sci 2024;4:26 https://dx.doi.org/10.20517/ss.2024.20 Page 3 of 34

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Figure 1. Schematic illustrating LIGS E for intelligent healthcare. Porous LIG is employed in three leading roles (S, sensing element; E,
electrode; C, conductor) to develop various flexible skin-integrated electronics (biophysical sensors, biochemical sensors, bio-
[3]
actuators, and power supply) for intelligent healthcare. Copyright 2023, Cell Press . Copyright 2023, Springer Nature [26] . Copyright
2020, American Chemical Society [34] . Copyright 2020, WILEY-VCH [35] . Copyright 2018, WILEY-VCH [36] . Copyright 2018, WILEY-
VCH [37] . Copyright 2020, Elsevier B.V [38] . Copyright 2022, Springer Nature [39] . Copyright 2021, Elsevier B.V [40] . Copyright 2017,
American Chemical Society [40,41] . Copyright 2022, Springer Nature [41,42] . Copyright 2020, Cell Press [43] . Copyright 2019, Wiley-VCH
GmbH [44] . Copyright 2020, American Chemical Society [45] . Copyright 2023, Springer Nature [46] . Copyright 2022, AIP Publishing [47] .
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Copyright 2019, Elsevier B.V. [48] . Copyright 2019, Springer [49] . Copyright 2017, Wiley-VCH GmbH [50] . LIGS E: LIG-based soft skin
electronics; LIG: laser-induced-graphene.

exhibits porous structures [Figure 2B], which probably enhances the sensing performance of LIG-based soft
sensors. Different from pure PI films, the Raman spectra of LIG showcase three prominent peaks at
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1,312 cm (D-band), 1,598 cm (G-band), and 2,612 cm (2D-band) [Figure 2B]. The 2D peak occurs due
to defects and damaged sp C–C bonds, and the G peak is related to graphite-derived structures. The sharp
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2D peak dominates in monolayer graphene, which is probably raised from graphene structures resulting
from laser processing. The introduction of graphene flakes endows LIG-based devices with specific
electronic conductivity. Besides IR laser, other laser sources, including visible and ultraviolet (UV), facilitate
LIG. It is worth mentioning that the LIG developed by the UV laser exhibits better uniformity and higher
resolution than that prepared by the IR laser. In addition to traditional PI sheets, other aromatic polymers,
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[51]
including polyetherimide (PEI) , poly(ether sulfone) (PES) , poly (ether ether ketone) (PEEK) , and
[52]