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Yu et al. Soft Sci. 2026, 6, 19 Page 13 of 24

simulations and sensitivity analyses within a broader parameter space to further verify and refine the
applicability of non-destructive gripping. Moreover, treating these thresholds as constraints during
experimental design can further reduce the risk of non-target injury. Given that the gripper is made of
Ecoflex0020/NdFeB composite material, it is necessary to evaluate the impact of its material properties
evolving over time on the driving performance. To this end, Young’s modulus and surface remanence were
compared between an old sample stored for ten months and a newly prepared sample from the same period
(results are shown in Supplementary Figure 3). The results show that within each range of magnetic powder
mass fraction, the relative differences in Young’s modulus and surface remanence between the old and new
samples are less than 5% [Supplementary Table 1]. This preliminary comparative experiment verifies the
conclusion that the mechanical and magnetic properties of MSG do not significantly degrade over ten
months timescale. To further investigate the impact of material property evolution on the driving
performance, a continuous contraction-expansion durability experiment was conducted: the gripper was
subjected to approximately 3,600 cycles of closing/opening movements over 2 h under constant driving
conditions (test process is shown in Supplementary Movie 1), and the gripper’s response speed to the driving
magnetic field was monitored during the video experiment, as shown in Supplementary Figure 4. The
gripper consistently responded stably to the driving magnetic field during the experiment, without any
significant degradation in driving performance. Based on this shrink-unfold durability test, we will continue
to use grippers with cyclic shrink-unfold treatment to perform continuous gripping tests, and simultaneously
verify the long-term durability of the microneedle surface and the stability of the drive system.

Because the microneedles are small, they may be subject to wear or failure during repeated contact cycles;
Therefore, systematic durability testing is necessary. To this end, we designed and conducted a microneedle
durability verification based on grasping cycles: MSGs performed continuous pick-and-release cycles on an
underwater mineral model at a fixed position, as shown in Supplementary Figure 5. Each experiment
comprised 50 pick-and-release actions and the protocol was repeated five times (totaling 250 cycles). The
number of failed grasps was recorded during the tests to quantify microneedle reliability under repeated
loading as shown in Supplementary Movie 2. Experimental observations showed that, in all five independent
trials, MSGs reliably completed every grasping action with no failures recorded. These results indicate that,
under the applied cyclic conditions and load levels, microneedles maintained sufficient mechanical integrity
and contact performance to support sustained underwater grasping tasks. Moreover, for the MSG,
continuous contraction-extension durability tests and prolonged grasping experiments provide preliminary
experimental evidence that the gripper materials retain stable performance over the short to medium-term
service life. However, the above experiments constitute only a preliminary assessment of the time-varying
behavior of MSG and the durability of microneedles, and have certain limitations. Future validation should
involve multi-dimensional quantitative analysis of the time-varying behavior of MSG, as well as life testing
under various conditions (e.g., different contact forces and high-pressure/low-temperature combinations) to
more accurately quantify the changes of MSG over time and the durability of microneedles, providing more
accurate data for engineering applications.

Although current experimental tests show that the MSG does not exhibit decreased driving performance or
time-varying behavior over time, the performance issues that may arise with increased usage still need to be
fully considered. This study used open-loop magnetic field actuation to verify the design and material
performance. However, we recognize that open-loop control poses several potential risks under long-term
cyclic use and complex marine environments. Therefore, closed-loop magnetic field actuation control of the
gripper’s motion is a key area for future research. Future development could involve adding mechanical
sensors to the gripper’s finger surfaces, allowing the pressure exerted on the finger surfaces during grasping
to be transmitted back to the system in real time, thereby adjusting the driving magnetic field strength and
saving energy. Furthermore, proportiional-integral-dderivative (PID) control programs could be integrated,