Soft robotic grippers often incorporate pneumatically-driven actuators that can elastically\ndeform to grasp delicate, curved organic objects with minimal surface damage. The complexity of\nthe actuator geometry and the nonlinear stressâ??strain behavior of the stretchable material during\ninflation make it difficult to predict actuator performance prior to prototype fabrication. In this work,\na scalable modular elastic air-driven actuator made from polydimethylsiloxane (PDMS) is developed\nfor a mechanically compliant robotic gripper that grasps individual horticultural plants and fungi\nduring automated harvesting. The key geometric design parameters include the expandable surface\narea and wall thickness of the deformable structure used to make contact with the target object.\nThe impact of these parameters on actuator displacement is initially explored through simulation\nusing the Mooneyâ??Rivlin model of hyperelastic materials. In addition, several actuator prototypes\nwith varying expandable wall thicknesses are fabricated using a multistep soft-lithography molding\nprocess and are inserted in a closed ring assembly for experimental testing. The gripper performance\nis evaluated in terms of contact force, contact area with the target, and maximum payload before\nslippage. The viability of the gripper with PDMS actuators for horticultural harvesting applications\nis illustrated by gently grasping a variety of mushroom caps.
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