<p>This paper presents the design and testing of a bioinspired compliant suction cup with tunable stiffness using shape memory alloy (SMA). In practice, a manmade suction cup easily loses adsorption as the cup body is prone to deform and the lips are thus curled up, which is disadvantageous for maintaining the adsorption state. In the nature, many animals are born with suction cups for stable adsorption on different surfaces. To maintain enough adsorption forces for a long time, some animals can control the suction cup's stiffness to keep the pressure difference between inside and outside of the cup body via muscular tuning. Inspired by this mechanism, we embedded SMA wires&nbsp;into a compliant suction cup for stiffness tuning. When the voltage is input, it increases the stiffness of the suction cup body and helps prevent deformation. Further, a bending moment is applied to the suction cup lip in contact with the surface, which reduces the probability of gas leakage as well as the risk of adsorption failure. In the experiment, suction cups with and without embedded SMA are tested respectively. The maximum pull-off forces and adsorption time are measured via an MTS tester, and the pressure values induced by SMA's tuning effect&nbsp;on the cup lip&nbsp;are recorded by membrane sensors. Results show that under the same preloading forces, the adsorption force is almost identical, while the adsorption maintaining time of the suction cup with embedded SMA increases&nbsp;by 365% at the maximum compared with that without SMA. The force generated by the bending moment applied to the lip increases by 360% at the maximum when the SMA is activated. The strain of the sample embedded with SMA is 186% less than that of the sample made of pure soft material at 20kPa stress. These results indicate that the embedded SMA can help increase the stiffness, reduce the deformation of the suction cup body, and enhance adsorption maintenance ability.</p>

A Suction Cup With Tunable Stiffness Based on Shape Memory Alloy

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2021/volume/85499

ASME 2021 Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2021)

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