To meet the practical application requirements of cardiac fixation during off-pump coronary artery bypass surgery, a soft cardiac fixator with a flexible arm was previously designed. To enable the soft cardiac fixator to adapt to uncertain external forces, this study evaluates the variable-stiffness performance of the flexible arm. First, the flexible arm was simplified as a soft silicone manipulator measuring 60 mm 90 mm 120 mm, which can actuate, soften, or stiffen independently along the length of the arm by combining granular jamming with input pressure. Then, the soft manipulator was modelled as a cantilever beam to analyse its variable-stiffness performance with granular jamming. Next, based on theoretical analysis and calculations, many experiments were conducted to evaluate the variable-stiffness performance of the soft manipulator. The experimental results demonstrated that the variable-stiffness performance is influenced by the flexible arm length, the size of the granules, and the input pressure.
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