Morphing adhesive interface for space robotic applications

Over the last years there has been a growing interest in the development of robotic technologies for attaching to, grasping and manipulating a wide range of objects, regardless of their shape, material and the presence of specific features on their surface. This issue has become of particular interest in the space field as regards the execution of ‘on-orbit servicing’ operations and the active removal of space debris, where the presence of non-cooperative objects requests the employment of grasping systems that are effective when the properties of the target object are unknown. In this framework, the paper deals with the study of an interface to be employed in a gripping device where morphing and adhesive capabilities are combined in a single smart system. On one hand, the morphing behaviour is provided by a foam support that could be easily deformed at ambient temperature, enhancing a good compliance with the target surface, even when macroscopic irregularities that obstacle the contact over the entire surface, like screws, nuts or reinforcements, are present. On the other hand, the adhesion is provided by means of electrostatic forces (electro-adhesion) generated when a high voltage, on the order of 1 – 5kV, is applied to a pair of electrodes embedded inside an insulating material. Two different solutions are considered to make an electro-adhesive layer with flexible electrodes: one consists of using a conductive fabric, from which the electrodes are cut with the desired geometry; the second one consist of fabricating a conductive silicone by mixing 20% conductive particles (carbon black particles) in a 10:1 PDMS silicone matrix. In both cases, the electrodes are embedded inside an insulating layer of TC-5005. The electro-adhesive layer obtained is then bonded with the foam support. Two sets of tests are performed as regards the adhesion capabilities and the morphing behaviour, aiming to evaluate (1) the force level reached with the two different types of electrodes and (2) the morphing capabilities of the entire substrate, i.e. its ability to conform to objects of different shapes or with macroscopic irregularities on the surface, and to determine how the compliance aids the adhesion behaviour.