## 3 Results and Discussion
As can be seen in Figure 5a, as the dielectric constant of the object increased, the release time became longer. Cellulose-based materials had the lowest dielectric constants and the fastest release speed among all objects, while plastic materials had the highest dielectric constants and demonstrated the slowest release behaviors (as listed in Supplementary Table S1). The strong correlation between the dielectric constant of the object and its release time demonstrated in Figure 5a can be explained by the increasing electroadhesion force on the object as the dielectric constant increased, which lead to a slower de-adhesion. 2. _The effect of the mass-specific density of the object_. The release time and the density of the objects are compared in Figure 5b. The general trend indicates a longer release time as the mass-specific density of the object increased. This could be explained by the fact that for low density materials such as wood, only the cellulose part was polarized, while the voids in between caused a negligible EA force, which resulted in a reduced total adhesion force compared to denser materials such as PVC. Also note that the molar polarizability was inversely proportional to the mass-specific density (Equation (3)). As the density of the object increased, the molar polarizability, \(P\), reduced, which lead to a longer dielectric relaxation time and a slower release time. 3. _The effect of the compliance of the object_. Although silicone film demonstrated a dielectric constant close to plastics, its release period was significantly shorter than plastics, which might be partially due to its softness. Peeling was observed during the release of silicone object, which indicates that for an extremely compliant material, a peeling effect could also speed up the release period. Figure 5: Detailed studies on the release time. (**a**) Effects of the object’s dielectric constant on the release time. Silicone base is used. (**b**) Effects of the object’s density on the release time. Silicone base is used. (**c**) Effects of base material’s dielectric constant on the release time of polyvinyl chloride (PVC) and silicone objects. (**d**) Effects of the charging time on the release time. Silicone base and Mylar material object are adopted in this comparison. _The effect of the molecular weight of the object_. It can be noted from Equation (3) that the molar polarizability was proportional to the molecular weight, which suggests that the material with a larger molecular weight could have a reduced dielectric relaxation time and a faster release time. This could explain why Mylar had a much worse de-electroadhesion behavior than PVC, despite the close dielectric constant (Mylar molecular weight: 20,326 [17]; PVC molecular weight: 47,040 [18]). * _The effect of surface roughness of the object_. Charge carriers are stored in the object and subsequently transferred to the gripper dielectric after switching off. A smooth surface profile allows better dielectric to dielectric contact, thus the plastics with a smooth surface showed much higher release periods than the others in this study. During the actuation of an EA pad, polarization not only happens on the object, but also on the base material, causing residual EA force on the base when the electric field is removed. Note that the RC time constant (the product of the resistance and the capacitance) of the EA pad was negligible compared to the residual EA force in this design. The measured RC constant of this EA pad (via a high-precision LCR meter (E4980 AL, Keysight)) was in the range of 0.1-1 us and hence could be safely neglected. The results demonstrate that the de-electroadhesion behaviors of the six EA pads were clearly dependent on the base material. In Figure 5c, the effects of the dielectric constant of the base material on the release time of PVC and silicone objects are compared.