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Yu et al. Soft Sci. 2026, 6, 19 Page 11 of 24

actuation has been shown to provide stable and controllable grasping forces at both micro and
macro-scales [50,51] ; SMA actuation can generate large grasping force. Lee et al. reported a device capable of
lifting on the order of 2,000 g . By contrast, MSGs are typically targeted at millimeter-to-centimeter scale,
[52]
low-mass objects [38] , and their maximum available gripping force is lower than that of the three
aforementioned actuation types. For fragile or delicate deep-sea specimens, however, excessive force may
cause sample damage, so MSGs possess an intrinsic advantage in achieving effective capture while
minimizing injury risk; (2) Response speed. Pneumatic and hydraulic systems typically switch states on the
order of 1-3 s [48-51] . SMA actuation completes the heating phase in air within approximately 1 s, but the
cooling/recovery phase is substantially longer (from a few seconds up to tens of seconds); in low-temperature
environments, cooling times are further prolonged, which limits operational frequency . In contrast,
[52]
magnetic actuation exhibits very fast mechanical response and can achieve rapid motion underwater as well,
giving MSGs a temporal advantage when capturing fast-moving or evasive marine organisms; (3) Energy
consumption. Quantified single-grasp energy for a pneumatic system has been reported at ≈1.8485 J
(≈0.0207 J/g) ; hydraulic systems generally consume more energy due to the need for pumps and more
[49]
complex power-transmission mechanisms. SMA requires continuous energy input to maintain the austenite
phase (i.e., sustained heating), resulting in a high long-duration energy burden . Magnetic actuation can
[52]
provide instantaneous high response forces via short power pulses, so its energy consumption is lower than
that of the other three approaches and avoids the continuous heating costs of SMA as well as the pump losses
of pneumatic/hydraulic systems; (4) Target damage. Pneumatic and hydraulic soft grippers have been
demonstrated in multiple studies to perform non-destructive manipulation of fragile targets (e.g., pneumatic
grippers handling balloons, hydraulic grippers manipulating insects) [49-51] . Although SMA can deliver large
forces, the heat generated during actuation may cause thermal injury to sensitive organisms, increasing the
risk of specimen damage . By comparison, MSGs typically exert lower grasping forces and use low-stiffness
[52]
compliant contact interfaces, making them more favorable for reducing both mechanical and thermal
damage to deep-sea organisms; (5) Environmental adaptability. Pneumatic systems face constraints in
deep-sea deployment due to wired gas supply requirements, pump volume, and issues related to fluid
compressibility, which limit their suitability under high hydrostatic pressure . SMA performance is highly
[49]
sensitive to ambient temperature; strong convective cooling underwater alters heating/cooling cycles and
thus affects reliability in variable or low-temperature environments . Conversely, MSGs do not rely on
[52]
compressible working media or sustained heating and can retain functionality under high pressure and low
temperature, conferring a notable advantage in environmental adaptability for deep-sea biological sampling
and related operations.

The magnetic approach offers: (1) fast response, since magnetic control does not require mechanical
transmissions and can reach millisecond-scale actuation , outperforming typical pneumatic/hydraulic
[34]
response times of 0.1-1 s ; (2) low energy consumption, because the coils need only be energized transiently
[53]
during approach and capture-unlike SMA actuators, which incur high energy costs due to repeated
heating/cooling cycles ; (3) reduced target damage, as the combination of a compliant silicone body and
[54]
surface microneedles enables damage-free handling of soft organisms compared with rigid or high pressure
systems ; and (4) improved environmental compatibility, since the silicone based gripper avoids
[17]
hydraulic/oil leakage risks associated with fluidic systems . Furthermore, the MSG’s modular architecture
[26]
facilitates replacement and reconfiguration and obviates tethering with cables, making it particularly suitable
for underwater and confined applications. Collectively, these attributes position magnetic soft grippers as
attractive solutions for underwater sensing, biological sampling and robotic intervention.

Because the MSG’s grasping force is generated primarily by magnetic attraction from the actuation system,
its absolute force is typically lower than that of pneumatic or hydraulic grippers. To enhance practical
gripping performance beyond simply increasing coil current or field strength, we incorporate biomimetic