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Page 4 of 24 Yu et al. Soft Sci. 2026, 6, 19

This manuscript details the gripper’s biomimetic design, materials processing and characterization, actuation
principles, performance comparisons, numerical simulations, experimental protocols, and fabrication
methods, and concludes with a discussion of the work and directions for future research. It offers systematic
methodologies and experimental/numerical validation in material-ratio quantification, surface-friction
enhancement, and deep-sea adaptability assessment, thereby providing actionable research pathways and
reference benchmarks for the further development and optimization of MSGs for deep-sea sample collection
and related marine engineering applications.

EXPERIMENTAL
The core contributions of this work are as follows: (1) design and fabrication of a modular, bioinspired
multi-finger MSG, whose fingers are assembled from customized Ecoflex0020/NdFeB composite modules to
achieve both strong magnetic responsiveness and mechanical compliance; (2) integration of biomimetic
microneedle arrays on the gripping surfaces to increase interfacial friction underwater, thereby overcoming
surface water films and mucous coatings that otherwise reduce grip stability; and (3) comprehensive
validation through material characterization, magneto-fluid coupling simulations, and underwater grasping
experiments. Fabrication of the MSG: the MSG consists of several modular components, and its fabrication
involves three main steps.

Preparation of the magnetic matrix: Two parts of Ecoflex0020 silicone (parts A and B) were mixed at a mass
ratio of 1:1, followed by the addition of NdFeB microparticles (400 mesh, 35-45 μm) at a filler fraction of
60 wt%. The slurry was homogenized using high-speed mechanical stirring (100 rpm, 5 min), and then
degassed in a vacuum chamber (-0.1 MPa, 5 min) until bubble-free. The degassed slurry was subsequently
poured into a polylactic acid (PLA) mold fabricated by 3D printing and cured in a constant-temperature
oven at 50 °C for 5 h (heating rate: 5 °C/min). After complete curing, the mold was removed, yielding
individual soft gripper modules.

Fabrication of the microneedle surface: The same silicone slurry formulation, after degassing, was cast into a
customized microneedle mold to fully fill the cavities. The pre-cured gripper modules were gently pressed
against the mold, ensuring tight contact between their surfaces and the microneedle slurry. The assembly was
then cured together at 50 °C for 5 h. After curing, the excess material was trimmed, resulting in soft gripper
modules with integrated microneedle structures.

Magnetization and module assembly: Each module was subjected to pulsed magnetization using a
magnetizer, where a 2.5 T pulse magnetic field was applied to magnetize the embedded NdFeB particles to
saturation, with the magnetization direction oriented toward the microneedle tips. Finally, the magnetized
modules were assembled and fixed together via an internal skeleton and interlocking bolts, completing the
fabrication of the MSG.

Sources of experimental reagents and instruments. Reagents: Ecoflex0020, purchased online, manufactured
by Smooth-On Inc. (USA); NdFeB powder (400 mesh), purchased online, manufactured by Hebei Chaoyue
Metal Alloy Materials Co., Ltd. Instruments: Vacuum drying oven, purchased online, manufactured by
Jiecheng Experimental Instruments Co., Ltd.; Data acquisition (DAQ) card, custom-ordered online,
manufactured by Art Technology Co., Ltd.; power amplifier, custom-ordered online, manufactured by
Harbin Zhinaxin Technology Co., Ltd.; robotic arm, purchased online, manufactured by Realman Intelligent
Technology Co., Ltd.; 3D printer, purchased online, manufactured by Bambu Lab; DC power supply and