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Jeon et al. Soft Sci. 2025, 5, 1 https://dx.doi.org/10.20517/ss.2024.35 Page 27 of 39

Table 7. The summarization of MO TFTs employing device structures for mechanical flexibility

Channel Buffer T Bending μ FE SS On/off Gate
Structure Substrate max radius 2 -1 -1 Refs. Year
materials layer (°C) (cm ·V ·s ) (V/decade) ratio dielectric
(mm)
8
Island IGZO TPU Al O 200 1.5 10.9 0.33 10 Al O [102] 2021
2 3 2 3
7
IGZO PI SiN /SiO 450 1 14 - 10 SiO 2 [193] 2016
x
2
IGZO PI Al O 150 0.125 6.06 - - Al O [33] 2020
2 3 2 3
ITZO PI Polymer 300 - 30 - 10 8 SiO 2 [199] 2022
7
IGZO PDMS - 200 - 6.1 - 10 P(VDF- [124] 2015
TrFE):PMMA
5
Junctionless ITO Paper - 70 - 2.3 0.11 10 Chitosan [66] 2021
6
ITO Paper - - - - 0.21 10 SiO solid [64] 2012
2
electrolyte
7
ITO Paper - - - 12.8 - 10 Chitosan [194] 2019
IZO PET - - 20 60 0.13 10 6 SiO solid [65] 2013
2
electrolyte
ITO PI - 200 0.125 12.74 0.881 10 7 Al O 3 [198] 2024
2
Electrode and IGZO PI SiO /SiN x 450 0.32 14.3 0.39 - SiO /SiN [61] 2017
2 2 x
channel
architecture IGZO PI SiO /SiN x 450 1 76.8 0.077 SiO /SiN [67] 2017
2 2 x
IGZO PI - 300 5 5 0.8 10 7 - [62] 2020
MO: Metal oxide; TFTs: thin-film transistors; SS: subthreshold swing; IGZO: indium gallium zinc oxide; TPU: thermoplastic polyurethane; PI:
polyimide; ITZO: indium tin zinc oxide; PDMS: polydimethylsiloxane; ITO: indium-tin-oxide; IZO: indium zinc oxide; PET: polyethylene
terephthalate.
do not significantly degrade the electrical properties of the TFTs. The stress distribution simulations showed
that without holes, the stress is uniformly distributed across the film, leading to random crack formation
under bending. With holes, stress is localized around the hole edges, which can be controlled to prevent
random propagation. This strategy enhances the durability of metal electrodes under mechanical strain,
making it suitable for various flexible electronic applications. The a-IGZO TFTs with hole arrays not only
exhibit improved mechanical stability but also maintain comparable electrical performance to standard
TFTs, demonstrating the feasibility of micro-hole structures in practical devices [Figure 9C] .
[62]

Both the micro-hole array and mesh structure approaches offer significant improvements in the mechanical
robustness of flexible TFTs. The micro-hole arrays focus on localizing stress and controlling crack
propagation, which is particularly effective for metal electrodes and oxide TFTs. On the other hand, the
mesh structures provide an even distribution of stress across the device, enhancing overall mechanical
stability. These strategies can be combined or further optimized to develop even more resilient flexible
electronic devices. Lastly, we summarized properties of MO TFTs with device structures designed for
mechanical flexibility in Table 7.

Future research could explore the integration of these designs with advanced materials and fabrication
techniques to further enhance the performance and durability of flexible electronics. Additionally, the
impact of different hole shapes, sizes, and patterns on the mechanical and electrical properties of the devices
can be investigated to fine-tune the design for specific applications. The goal is to develop flexible
electronics that can withstand the rigors of real-world use while maintaining high performance.