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Kulkarni et al. Soft Sci. 2025, 5, 12 https://dx.doi.org/10.20517/ss.2023.51 Page 13 of 35

Figure 5. Underwater travel speed comparison of various soft robots. (0.42 cm/s) Soft robotic manta ray composed of IPMC that can
move underwater [65] . (1.158 cm/s) Soft robotic origami jellyfish that allows for fluidic jet propulsion [173] . (2.5-2.8 cm/s) Soft robotic
jellyfish composed of SMAs to allow for motion in underwater environments [177] . (3.72 cm/s) Soft robotic fish composed of dielectric
elastomers that can move forward when actuated [180] . (All images are licensed under CC BY 4.0. http://creativecommons.org/licenses/
by/4.0/.) IPMC: Ionic polymer metal composites; SMAs: shape memory alloys.

Figure 6. Soft sensors for underwater soft robot applications. (A) Liquid metal-based sensor composed of elastomeric fluidic channels
with filled conductive liquid metal eGaIn to measure strain and provide feedback to control the soft robotic fish [184] ; (B) IPMC material
which can be used as a sensor under bending deformation. IPMC sensors can detect changes in deformation, pressure, velocity, and
[185]
humidity . [All images (A and B) are licensed under CC BY 4.0. http://creativecommons.org/licenses/by/4.0/.] IPMC: Ionic polymer
metal composites.

underwater vehicle to measure the amplitude and frequency of waves . IPMC devices have also been used
[186]
[187]
for bioinspired sensing , for example, to develop an artificial fish lateral line for the detection of source
localization in underwater environments . Thus, the development of IPMC sensors allows for efficient
[188]
sensing in underwater environments for soft robotic devices.

SOFT ROBOTS FOR SPACE EXPLORATION
The environmental conditions of extraterrestrial settings present distinct challenges for robot operations.
Microgravity can incur mechanical effects that alter the behavior of robots compared to earth-bound
operations . Space environments have extreme temperature fluxes due to the absence of a medium for heat
[22]