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Page 6 of 10 Zou et al. Soft Sci 2024;4:19 https://dx.doi.org/10.20517/ss.2024.13

a 2.7-inch 42-PPI stretchable Micro-LED display based on an island-bridge structure in combination with
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buckling [Figure 2B]. The obtained device panel can be normally operated under biaxial stretching,
free-form twisting and poking, revealing its excellent capability for tolerating large deformation.

Academic research, on the other hand, has led to the development of some unusual deformable displays
with expanded functionalities that common ones cannot provide. Jang et al. demonstrated using Micro-
LEDs fabricated on a 2D kirigami electrical circuit board to realize an auxetic distortion-free meta-display
with a stretchability of 24.5% and Poisson’s ratio of -1 under uniaxial stretching [Figure 2C]. The concept
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constitutes a remarkable improvement over the common stretchable displays, which can lead to the
deterioration of the reduced resolution per unit area and the blurred display image quality when subject to
large mechanical stretch. Kim et al. demonstrated a hexahedral LED array with general row and column
control lines by laminating Micro-LED devices to an acrylonitrile butadiene styrene (ABS) film, followed by
selective plasticization and transformation, forming nondisruptive tucking-based origami at the electronics
level [Figure 2D]. The novel origami structure and fabrication process, combined with laminated Micro-
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LEDs, pave the way toward developing 3D foldable displays.

Wearable devices for healthcare
Apart from displays, deformable Micro-LEDs attachable to skins or implantable to human/animal bodies
can be used as wearable light sources for healthcare purposes. For instance, Lee et al. demonstrated a
wirelessly powered smart contact lens based on infrared Micro-LEDs [Figure 2E] . The contact lens with
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integrated Micro-LEDs can be conformally attached to the eyeball, effectively treating diabetic retinopathy
that can cause vision loss and blindness in people with diabetes. Li et al. developed an implantable, wireless-
powered dual-color Micro-LED probe for bidirectional optogenetic modulations [Figure 2F]. The
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lightweight device has good biocompatibility, reduced dimensions and good portability, constituting
remarkable improvements over conventional implantable LEDs driven by external wires and batteries,
which restrict the natural motion and social interactions of animals. Self-powered, battery-free flexible
Micro-LED-based Optogenetic Systems have also been reported to further reduce the system weight [20,65] .
Zhang et al. demonstrated a wirelessly powered Micro-LED patch for local tissue oximetry, which allows
effective monitoring of the regional tissue oxygenation in animal models . Such a Micro-LED-based tissue
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oximeter can create many opportunities for studying various O -mediated processes in naturally behaving
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subjects, with implications in biomedical research and clinical practice. Phan et al. reported a flexible and
wireless Micro-LED patch with an internet of things (IoT) healthcare platform for wound healing
applications, which opens tremendous opportunities for remote healthcare with cost-effectiveness in the
future .
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CONCLUSIONS AND REMARKS
Technological advancements in substrate removal, transfer printing and mechanical designs have enabled
the fabrication of deformable Micro-LEDs in flexible/stretchable formats. These devices not only reserve
their excellent optoelectronic performance but also exhibit substantially improved flexibility and better
reliability than rigid counterparts, making them suited for potential application in areas such as unusual
deformable displays and wearable devices for healthcare. It is envisioned that deformable Micro-LEDs will
lead to a technological revolution in the future display industry.

However, before practical applications of deformable Micro-LEDs, several issues need to be addressed. First,
further improving the mechanical properties of Micro-LEDs is urgently required. While some novel
mechanical designs, such as island-bridge and buckling structures, can be adopted to enhance the system
stretchability, these concepts lead to reduced pixel resolution and compromised filling factors. Innovations