Page 100 - Read Online

Page 2 of 24 Yu et al. Soft Sci. 2026, 6, 19

across diverse underwater organisms, with reliable, rapid, and damage-free manipulation. This research establishes
a novel technological pathway for soft robotic grasping in underwater applications, offering both engineering value
and scientific significance.

INTRODUCTION
Since the beginning of the twenty-first century, Clarke has argued that deep-sea robotic platforms have
become a cornerstone technology for exploring the planet’s “final frontier”, enabling long-duration,
long-range, and high-risk deep-sea observations . Advances in autonomous underwater vehicles (AUVs)
[1,2]
have markedly improved the capability for long-term monitoring of ecological and physical processes in
deep waters , while hybrid robotic systems have demonstrated adaptability and multi-functionality for
[3]
multidisciplinary exploration of the ocean’s twilight zone . Bioinspired legged designs have also been
[4]
proposed to conduct low-disturbance surveys of seabed sediments and benthic habitats . Collectively, these
[5]
developments point toward an era of “precision operations in the deep sea”, in which intelligent and
compliant end-effectors are key enabling technologies. Mechanical grippers remain a principal enabler for
resource acquisition in underwater robotics, but the marine environment is highly complex and uncertain,
and many targets of interest are fragile (e.g., jellyfish), slippery (e.g., sea cucumbers) or irregular (e.g.,
[6]
mineral nodules) . Conventional subsea manipulators are typically high-stiffness devices that exhibit low
[7]
tolerance to contact uncertainties; as a result they can easily damage delicate specimens and are prone to
failure in harsh underwater conditions .
[8]
Soft robots have gained increasing relevance in marine science and deep-sea exploration owing to their
adaptability and low environmental disturbance. Gruber and Wood reviewed the advantages of soft robotics
for biological sampling and environmental monitoring, and Laschi and Calisti demonstrated the potential of
soft materials and control strategies for reaching extreme depths [9,10] . Bioinspired soft systems reported by Li
et al. show excellent adaptability and fine manipulation capabilities suitable for deep-sea tasks . Other
[11]
groups have advanced shape-memory-alloy (SMA) actuated soft devices, highly reconfigurable modular soft
robots, and small-scale deformable systems that adapt shape and locomotion modes to diverse underwater
environments [12-14] . For instance, a jellyfish-inspired soft platform developed by Wang et al. exhibits efficient
propulsion and precise control advantageous for fine manipulation tasks in cluttered underwater settings .
[15]
Consequently, the development of bioinspired, compliant end-effectors for safe, nondestructive underwater
handling has become an urgent research priority.

Soft grippers attract substantial attention in the manipulation community due to their intrinsic compliance,
superior shape conformance, and gentle interaction with fragile targets . From precision electronics
[16]
assembly to nondestructive agricultural harvesting, soft grippers have demonstrated broad application
potential . A variety of actuation modalities have been adapted for underwater soft grippers, with
[17]
pneumatic and hydraulic schemes being the most widespread [18,19] . Notable examples are dexterous
underwater soft manipulators combining multiple bending/extension segments and compliant grippers to
perform multi degree of freedom (DOF), gentle manipulation of fragile and irregular biological targets [20-22] ,
hydraulic soft grippers for delicate coral sampling at depths up to 800 m , and force-sensing soft
[23]
end-effectors for tactile feedback . Particle-based and variable-stiffness soft grippers have also been
[24]
proposed to generate grasping forces via jamming mechanisms . However, pneumatic systems require
[25]
compressors and tubing, rendering them bulky and susceptible to pressure-induced performance loss at
depth; hydraulic systems, while depth-insensitive and capable of larger forces , demand fluid lines and pose
[26]
leakage-related contamination risks and increased system mass. Alternative actuators such as shape-memory
alloys suffer from slow thermal response and limited cycle life . In short, existing actuation paradigms entail
[27]
trade-offs among response speed, system integration, and environmental compatibility, limiting their
suitability for efficient, nondestructive subsea operations.