A Soft Gripper with Rigidity Tunable Elastomer Strips as Ligaments

Amir Mohammadi Nasab, Amin Sabzehzar, Milad Tatari, Carmel Majidi, Wanliang Shan

Research output: Contribution to journalArticlepeer-review

72 Scopus citations


Like their natural counterparts, soft bioinspired robots capable of actively tuning their mechanical rigidity can rapidly transition between a broad range of motor tasks-from lifting heavy loads to dexterous manipulation of delicate objects. Reversible rigidity tuning also enables soft robot actuators to reroute their internal loading and alter their mode of deformation in response to intrinsic activation. In this study, we demonstrate this principle with a three-fingered pneumatic gripper that contains "programmable" ligaments that change stiffness when activated with electrical current. The ligaments are composed of a conductive, thermoplastic elastomer composite that reversibly softens under resistive heating. Depending on which ligaments are activated, the gripper will bend inward to pick up an object, bend laterally to twist it, and bend outward to release it. All of the gripper motions are generated with a single pneumatic source of pressure. An activation-deactivation cycle can be completed within 15 s. The ability to incorporate electrically programmable ligaments in a pneumatic or hydraulic actuator has the potential to enhance versatility and reduce dependency on tubing and valves.

Original languageEnglish (US)
Pages (from-to)411-420
Number of pages10
JournalSoft Robotics
Issue number4
StatePublished - Dec 2017
Externally publishedYes


  • grasping and twisting
  • rigidity tunable elastomer
  • soft gripper

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Biophysics
  • Artificial Intelligence


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