Gecko-inspired adhesion enhanced by electroadhesive forces

Soft robotic manipulators have been increasingly adopted over the last decade due to their passive conformation to the shapes of objects, which can reduce control complexity. The performance of these grippers can be improved using flexible adhesive skins that increase tactile gripping forces, which is particularly important when grasping delicate objects and flexible substrates that are otherwise difficult to manipulate. In this work, we investigate how passive gecko-inspired fibrillar adhesion can be augmented by actively controlled electroadhesion (EA). The passive gecko-inspired skin (GS) enables adhesion with no power consumption while EA is controlled with an applied voltage. We have shown how the microstructures in a gecko-inspired adhesive skin affect EA by using numerical simulation to quantify how they influence the localized EA field strength. The results show that the microstructures cause a highly non-uniform distribution of electric field strength generate and hence the EA force distribution is inhomogeneous. Overall, it was found that the dielectric properties of the gecko-inspired skin reduce the magnitude of field intensity on the adhesive contact surface by only 2.1% at 3 kV. It is experimentally determined that when compared with GS alone, EA with gecko-inspired skin increases the shear force by 66.8% and the normal force by 53.7% with an applied voltage of 4 kV. It is shown that the gecko skin's adhesion force is enhanced by increased engagement of the fibrillar microstructure to object surfaces due to EA. The increased contact engagement is experimentally demonstrated using frustrated total internal reflection imaging. This work shows that electroadhesive-enhanced gecko-inspired skin generates a greater adhesive force than the sum of forces from the separate gecko-inspired skin and EA. In this way, electrically controllable and passive adhesion mechanisms can be combined to improve the handling of flexible and delicate objects with smooth or rough surfaces.