Two-Way Shape Memory Polymer Composite Gripper for Adaptive Robotic Applications

Abstract

Shape memory polymers (SMPs) have attracted significant research interest in robotic applications due to their tunable thermomechanical properties and ability to change shape and recover their original form upon exposure to external stimuli, primarily temperature. One-way SMPs require reprogramming for each cycle, whereas two-way SMPs (2W-SMP) intrinsically exhibit shape memory behavior without additional programming. This study develops a cross-linked polycaprolactone/dicumyl peroxide (PCL/DCP) based 2W-SMP composite. The thermomechanical and thermal properties are characterized using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). To create a freestanding 2W-SMP capable of shape change and recovery solely through temperature variations, without relying on external loads for actuation, the SMP is embedded in a low-stiffness elastomeric matrix. The resulting composite material exhibits an intrinsic two-way shape memory effect, enabling reversible shape transformations during heating and cooling cycles. The one-way and two-way shape memory behaviors are systematically investigated using DMA. The one-way shape memory effect demonstrated exceptional shape fixity and strain recovery values of 96% and 96.8%, respectively, confirming the material's ability to fix a temporary shape and recover its permanent form upon external stimulus. The practical potential of the 2W-SMP is demonstrated by testing it as a gripper device, which exhibited repeatable opening and closing responses during heating and cooling cycles, illustrating its reversible shape transformations and durability over multiple actuation cycles.