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Page 14 of 30 Kim et al. Soft Sci 2023;3:16 https://dx.doi.org/10.20517/ss.2023.07

design, and high-performance sensors that exceed human senses such as sight, hearing, and touch can also
be realized [198,199] . In addition, a multifunctional sensor capable of simultaneously recording pressure, shear
force, and bending, along with sensing targets such as temperature, current, and humidity, based on the
deformability of 3D structures, has been proposed [200,201] . Recently, sensing devices with bioinspired sensing
capabilities, such as temperature and deep-versus-fine touch contact sensing, have been reported by
combining actuators to form complex sensor network systems through 3D printing [202,203] . Along with these
developments of functionalities, the 3D arrangement of sensors enables spatiotemporal mapping of
responses, improves the integrated density, and can also provide 3D vector field detection. In this chapter,
we introduce a high-performance sensor based on 3D structures that can detect various external stimuli
[Figure 7].

Kim et al. fabricated macro-, meso- and microscale 3D fliers inspired by wind-dispersed seeds using the
mechanically guided assembly of 3D mesostructures [Figure 7A] . The 3D fliers were designed to be
[201]
integrated with active electronics and colorimetric sensors to fly without power and gather information
across natural environments or city settings. They exhibited significant potential for various applications,
including atmospheric monitoring, complementing the conventional gravimetric and optical
particle-counting methods. Peng et al. fabricated a porous flexible strain sensor that can monitor human
motion by casting polyurethane/carbon nanotube composites into a 3D printed sacrificial mold
[204]
[Figure 7B] . The strain sensor exhibited high stretchability and excellent recoverability. The potential of
user-specific stretchable wearable sensors was demonstrated using the advantage of 3D printing of
unlimited geometry designs. Won et al. demonstrated a 3D microelectromechanical sensor that can
simultaneously measure temperature, normal force, shear force, and bending using monocrystalline silicon
nanomembranes as piezoelectric elements [Figure 7C] . A table-like 3D structure was implemented
[205]
through mechanically induced geometric transformation (buckling), and scalable production of
interconnected array devices with a spatiotemporal mapping function was demonstrated. Becker et al.
reported a high-density integrated active matrix magnetic sensor with a 3D magnetic vector field-sensing
capability that enables remote recognition of moving objects [Figure 7D] . A 3D magnetic sensor array
[206]
was fabricated through a micro-origami process of a self-folding polymer platform with embedded sensors.
The applicability to real-time multidirectional tactile perception was demonstrated through the integration
with an electronic skin embedded with magnetic hair. Liu et al. proposed a self-healing kirigami assembly
strategy that allows planar sheets to completely wrap a 3D curved surface for conformal electronics
[207]
[Figure 7E] . The function of the device is guaranteed by maintaining electrical conductivity using a
conductive self-healing material. By applying the proposed technique to a spherical surface, a
multifunctional wind-sensing system was fabricated to detect the pressure caused by wind blowing from
various angles. Katiyar et al. mimicked the biological eyes by combining the mechanical superiority of
ultra-thin silicon and deformable optoelectronics with hemispherical geometry via pneumatic pressure-
[208]
induced expansion [Figure 7F] . In addition, the strain derived from pneumatic pressure causes shrinkage
in the bandgap of Si, providing photo-sensing capability beyond its fundamental absorption limit in Si
nanomembrane photodetectors. Cheng et al. fabricated a 3D ribbon-shaped flexible resistance-type
vibration sensor that can measure low-frequency vibration with long-term stability [Figure 7G] . They
[209]
demonstrated that the fatigue life of 3D ribbon-like flexible electronics can be significantly extended by
adopting an anti-fatigue strategy that converts metal-dominated failures into desired polymer-dominated
failures. This anti-fatigue design shows the possibility of long-term health monitoring or human-like
robotic acceptance. Wang et al. fabricated complicated 3D interconnected networks of horseshoe-shaped
active components, as demonstrated with a stretchable capacitive pressure sensor array [Figure 7H] .
[210]
Using 3D printing techniques, they constructed complex structures with a high spatial resolution that can
induce the photopolymerization of the local area triggered by UV projection. According to the finite
element analyses, the precisely controlled 3D microstructures exhibited exceptional stretchability,