Sub-zero self-healable and fatigue-resistant conductive ionoelastomers for sensorized soft pneumatic robots

Abstract

Soft robotics has gained increasing interest recently, but challenges persist, including operating at low temperatures, susceptibility to damage, fatigue-induced deterioration, and the need for proprioceptive sensing for autonomous operation and recovery. Addressing these challenges, this paper introduces a novel conductive ionoelastomer with a dendritic microstructure engineered to resist crack propagation and self-repair even at sub-zero temperature, offering opportunities to construct more adaptable soft robotic grippers which can work in complex environments. Silk ionoelastomers, serving as the matrix material, are complemented by dendritic sodium polyacrylate crystalline fibers. This integration significantly enhances strength and Young's modulus, while maintaining low hysteresis (below 24%), high fracture toughness (35.2 kJ m⁻²), and a fatigue threshold of 754 J m⁻². Furthermore, it exhibits exceptional self-healing capabilities at both room temperature and −20 °C, enabling its use in flexible sensors with elongation capabilities of up to 500%. Utilizing folding techniques and inherent self-healing properties, this material can be tailored into pneumatic fingers with sensing and damage-detecting functionalities, facilitating the grasping of various objects. Even when exposed to various types of external damage, its pneumatic functionality is fully restored through the self-healing process at room temperature or low temperature, underscoring its resilience and adaptability in practical applications.