In　this　article,　by　utilizing　the　dielectric　elastomer　composite　actuators　(DECAs),　we　design　and　fabricate　a　stiffness-tunable　robotic　gripper.　Firstly,　the　voltage-induced　electromechanical　deformation　of　the　DECA　is　investigated　by　applying　a　ramping　voltage.　Subsequently,　effects　of　different　factors,　including　the　jamming　pressure,　the　roughening　process　of　fibers,　the　ratio　of　overlapping　area　of　fibers,　and　the　strain-stiffening　of　DEs,　on　the　output　force　performance　of　the　DECA　are　considered,　respectively.　Afterwards,　the　grasping　and　gripping　performance　is　explored　by　exhibiting　a　comparison　of　the　gripper　with　and　without　stiffness-tunable　effect.　Finally,　the　output　gripping　force　of　the　stiffness-tunable　gripper　under　different　jamming　pressures　and　object　sizes　is　investigated.　The　maximum　size　limitation　of　the　gripped　object　and　the　output　force　of　the　robotic　gripper　(induced　by　stiffness　tunability)　are　found　to　be　12　cm　and　5　N,　respectively.　©　2020　IOP　Publishing　Ltd