Soft Tactile Sensing Skins for Robotics

Soft electronic skins (E-skins) capable of tactile pressure sensing have the potential to endow robotic systems with many of the same somatosensory properties of natural human skin. In this progress report, we review recent progress in creating soft tactile pressure sensing skins to give robots a sense of touch that resembles human skin sensing. For soft tactile pressure sensing skins, researchers have focused on five main sensing principles: (1) resistive; (2) capacitive; (3) magnetic; (4) barometric; and (5) optical. The combination of these traditional sensing techniques, along with the use of soft materials such as liquid metal and magnetic elastomers, has improved the perception capabilities and mechanical characteristics of artificial skin. In addition, the implementation of artificial intelligence and machine learning algorithms for data processing give robotic systems with these soft sensing skins an enhanced sense of touch. E-skins for tactile sensing have a central role in a range of robotic applications, from haptics and teleoperation to bio-inspired soft robots. For many of these applications, E-skins must be soft, thin, flexible, stretchable, and lightweight so that they can be mounted on a robot, incorporated into clothing, or placed on human skin without interfering with mobility or contact mechanics. Significant research has been conducted on sensing techniques that can allow a robot to achieve a sense of human touch, with important progress being made in force feedback sensing, texture recognition, and spatial acuity. We begin by covering principles of tactile sensing in humans, robotics, and human-machine interaction. This is followed by an overview of soft material transducers capable of pressure and force sensing. This includes resistive, capacitive, magnetic, barometric, and optical sensing techniques. We close with a summary of emerging trends in sensor design and implementations for applications in robotics.