## 3 Results and Discussion
It can be noted that for both PVC and silicone objects (representing slow (10 s) and fast release (0.1-1 s) objects), the release times showed a gradual decrease as the dielectric constant of the base increased. The general negative relationship between the dielectric constant and release time could be explained by the relationship between the molar polarization and dielectric constant in Equation (3). The increasing dielectric constant caused an increase in the molar polarization, and thus a faster release speed. However, it is worth noting that despite this general negative relationship, a global minimum in release time for PVC was found at \(\varepsilon_{r}\) = 2.8 (silicone base material), which suggests that a more comprehensive comparison between the base materials is needed. To systemically characterize the effects of the base materials, the performance of each EA pad was evaluated based on the release time of the eight objects. For each object, the EA pad's release time, from the shortest to the longest, was assigned 6 to 1 points according to the ranking, and these points were summed for each EA pad. As shown in Figure 4c, the EA pad with silicone as the base material had the highest score, while the Styrofoam had the lowest points among all. It can also be noted that despite the highest score, the silicone EA pad had the lowest points (i.e., longest release time) in grasping silicone and tissue substrates. This suggests that for general grasping and release applications, silicone material is arguably the best material for fast de-electroadhesion of EA pads with exposed electrodes, however, for certain objects used in this work, such as the silicone film and paper tissue, acrylic could be a better option for the base material. Until now, the characterization of de-electroadhesion speed against different material types was based on a fixed charging period of 10 s. Here, the base substrate and object material types were fixed (silicone material for base due to the highest score and Mylar material for the target object) and the charging period was varied from 3 to 30 s. Figure 5d compares the measured release period of the object as a function of the charging period, and raw data can be found in Supplementary Material Table S3. It can be noted that as the charging period increased, the release period increased dramatically. For example, the average release period was 3.1 s when the charging period was 3 s, while the release period rose to 140.6 s when the charging period became 30 s, which could be due to a greater amount of charge building in the object and base substrate during the longer charging period. The positive correlation between the charging and release period suggests that a faster de-electroadhesion speed can be achieved by reducing the charging period. However, note that an extremely short charging period could reduce the success rate of lifting up an object. An alternative approach developed by the authors to achieve fast de-electroadhesion is to use a dielectric elastomer actuator (DEA), which is integrated into a flat EA gripper, to generate out-of-plane oscillation and thus force the object to release. For the detailed design of this EA-DEA gripper please refer to [19].