## 1 Introduction  
Controllable and robust robotic gripping and manipulation technologies play a significant role in manufacturing automation applications [1]. These technologies are usually classified into four categories: (1) impactive methods, including jaws and clamps; (2) ingressive methods, including pins and hackles; (3) astrictive methods, including suction, magnetoadhesion, and electroadhesion (EA); and (4) contigutive methods, including chemical and thermal adhesion [2]. Due to the fact that EA technologies can form adhesion or gripping systems with enhanced adaptability, reduced complexity, low energy consumption, and gentle material handling characteristic, EA has been extensively used in many robotics applications for over half a century [2], including electrostatic chucking of materials in semiconductor industries [3], gripping of delicate objects [4] and fibrous materials [5], and robotic locomotion [6; 7; 8]. A typical EA system includes an EA pad (consisting of conductive electrodes supported by the base substrate and covered by dielectric material), a high voltage power supply, and a target object [9; 10; 11], as shown in Figure 1. EA is the electrically controlled adhesion between the EA pad and the target object [12]. The EA force is generated by high electric-field induced polarization or electrostatic induction depending on the object material type [10]. Despite its simple adhesion principle, electrodhesion is in fact a very dynamic and complex electrostatic attractive effect [11]. A period of seconds or even hours is required to complete the EA adhesion and de-adhesion cycle depending on the material dielectric and polarization properties [11]. The EA adhesion process starts by applying a high voltage to the EA pad. A dynamic polarization, mainly the orientational polarization and interfacial polarization [10], results in induced charges generated in the dielectrics covering the electrodes, the interface between the EA pad, and the object. The number of induced charges and their alignments will then be saturated, leading to the maximum adhesive force between the EA pad and the object. Note that the steady value of the EA force is usually much larger than the initial value. The EA de-adhesion process begins with turning off the voltage to the EA pad. Residual charges will remain in the EA system and gradually disappear due to the de-polarization of the dielectrics. The EA de-adhesion process ends when the weight of the object overcomes the residual EA force between the pad and the object. The dielectric materials covering electrodes are usually organic polymers to prevent dielectric breakdown when grasping conductive and semi-conductive materials. However, these organic polymer materials usually have slow dielectric relaxation properties which could result in trapped charges and thus residual EA forces during the release stage. It can be noted that when a flexible EA pad coated with a dielectric polymer is in contact with a smooth object surface and a high voltage is applied, the induced astrtictive EA force will bring the pad closer to the object. This process might remove the air between the contacting object and the EA pad, and, as the EA pad forms a circular seal around the object (due to the circular pattern of the EA), thus generate a negative pressure adhesion force. However, EA has been demonstrated to function in a vacuum [2], which suggests that this suction force is not the main adhesion force, but could delay the release of the object in air. Apart from the negative pressure, due to the intimate contact, cohesive forces such as Van Der Waals forces are involved, which may delay the release process further, as illustrated in Figure 1a. Various quick-release methods have been proposed, including mechanical and electrical methods. Mechanical solutions include the use of vibrations [2], pegs [5], and air jets [5]. Electrical solutions include voltage control methods such as exponentially decaying sine wave voltage output methods [13].