Flexible gripping device operating by electroadhesion

Abstract

The invention relates to a flexible gripping device operating by means of electrical adhesion, comprising a flexible sheet (110) extending along a transverse plane (XY) and having an outer edge (111), and comprising a gripping element (120) extending along a longitudinal direction (Z) perpendicular to said transverse plane (XY). The gripping element may be manual or part of another machine. To create the electrical adhesion, the flexible sheet (110) comprises a plurality of electrodes (130) configured and arranged to create an electrical adhesion force when the sheet approaches the surface of the object over its lateral extension. The electrode (130) may be connected to a power supply device, which may also be embedded in the gripping element (120). In order to avoid separation of the sheet in use, the gripping element (120) is secured to the flexible sheet (110), in one or more inner regions (125) positioned spaced apart from the outer edge (111), preferably such that when the gripping element is pulled at the edge of the one or more inner regions in a direction (Z) perpendicular to the transverse plane (XY), the gripping element (120) is moved away from the outer edge (111). The attachment angle between the sheet and the surface is less than 30 DEG, and a vacuum volume 200 is formed below the inner region 125.

Description

Technical Field

[0001] This invention relates to a flexible gripping device that operates through electroadhesion.

[0002] Its structure is similar to a vacuum suction cup, but it does not require a vacuum pump. In fact, the gripping is achieved through the combined action of the electrostatic force between the device and the object, the passive vacuum force caused by electroadhesion, and the force that separates the object. Background Technology

[0003] Electroadhesion-based gripping devices can use the adhesive force generated by the edge electric field to lift objects[1],[2].

[0004] Typically, flexible electroadhesive grippers can generate a large holding force when gripping objects from the side, ideally allowing fingers or claws to wrap around the object [3], [4].

[0005] Conversely, when gripping an object from the top surface, the gripping force tends to be lower, similar to a vacuum suction cup gripper. The reason for the lower electroadhesion when gripping an object from the top surface is the peeling separation between the gripper and the object surface [5].

[0006] This is Figure 1 The effect of posture on the gripping force of the flexible electroadhesive gripper is shown in the figure [3]; the force involved in gripping from the top surface (the rightmost case) is very low (on the order of mN), thus hindering any practical application.

[0007] Reference

[10] uses electroadhesion in a vacuum chuck device, which has a dedicated channel (76 in Figure 9) for air suction (active vacuum generating device). Electroadhesion is only used to improve the airtightness of conventional vacuum chucks.

[0008] Reference

[11] used an electroadhesive film fully supported by thicker and more rigid elements, so the resulting gripping device could not adhere to various surfaces or utilize the electroadhesive zipper effect [6]. This is an inefficient and unusable electroadhesive device.

[0009] Reference

[12] describes an electroadhesive gripping system with a vacuum-generating gripper. The gripper may include an electroadhesive surface associated with one or more electrodes and a support structure coupled to the electroadhesive surface. The support is coupled to the back side of the electroadhesive surface to at least partially define the shape of the electroadhesive surface. The support is configured to bend into a shape between a bent shape and a non-bent shape. An extension arm is configured to apply force to the support to bend the support from a non-bent shape to a bent shape. When placed near a substrate, the extension movement of the support can vacuum seal the electroadhesive surface to the substrate. However, this solution is not sufficiently effective because it includes a support layer behind the electroadhesive sheet and includes an active folding device. In particular, the presence of the "unfolding arm" (422 in FIG8B) and the structure that straightens the membrane from a bent shape to a flat shape effectively prevents the formation of a seal between the membrane and the object unless the unfolding arm is completely flat and the object surface is also completely flat, which is practically impossible in industrial applications. Even a misalignment of only a few µm (10⁻⁵) between the gripper structure and the object surface can create a channel through which air can flow, preventing the formation of a passive vacuum. Furthermore, as shown in Figure 9A, elements 538a and 538b transfer the lifting force to the edge of the membrane. This causes peeling from the edge, resulting in a very high peel angle and a very low peel force, similar to that in a two-finger electroadhesive gripper.

[0010] Reference

[13] describes an electroadhesive gripper comprising: a base; a pair of gripping arms hinged to and connected to two end portions of the base and facing each other; an adhesive suction cup made of an electroadhesive film, the film comprising an insulator, electrodes disposed on the insulator, and wires disposed on the insulator and electrically connected to the electrodes, the adhesive suction cup being supported by each gripping arm; and a power supply device electrically connected to the electrodes of the adhesive suction cup for power supply. Thus, the electroadhesive gripper, by means of the adhesive suction cup made of an electroadhesive film and the two gripping arms supporting the two ends of the adhesive suction cup, can have excellent gripping force and can grip objects of various shapes. Attaching the arms to the ends of the electroadhesive suction cup makes the device complex and expensive, and not always effective, only suitable for a few objects with a defined curvature. Figure 1Element 53 is attached to the electroadhesive film to its edge, hardening it and preventing the film from forming close contact with the object surface unless element 53 and the object surface have a perfectly matched shape with a tolerance of less than 10-50 µm. This is impractical for gripping industrial objects because the shape of industrial objects cannot perfectly match the shape of the gripper with such low tolerances. This creates air channels, thus preventing the formation of a passive vacuum. Furthermore, the extension of element 53 to the edge transmits the lifting force to the edge of the film, causing peeling from that edge and thus separation at a high peel angle and consequently low force. Moreover, the shape of element 53 and its extension to the edge prevent the formation of a vacuum volume during film lifting, as the film cannot deform freely due to the presence of element 53, and peeling from the edge also allows the entire central portion of the film to communicate with the outside air.

[0011] There is still a need for a simple, economical, and effective electroadhesive gripper that can be used on irregular surfaces. Summary of the Invention

[0012] The purpose of this invention is to provide a flexible gripping device to solve the problems of the prior art and overcome its shortcomings.

[0013] The present invention relates to a flexible gripping device according to the appended claims.

[0014] Detailed Description of Embodiments of the Invention Attached Figure Description The invention will now be described by way of non-limiting example and with particular reference to the accompanying drawings, in which: Figure 1 The effect of posture on the gripping force of the flexible electroadhesive gripper is shown [3]; the force involved in gripping from the top surface (rightmost case) is very low (on the order of mN), thus hindering any practical application [8]; Figure 2 A schematic diagram of an electro-adhesive vacuum chuck attached to the top surface of an object according to an embodiment of the present invention is shown. Figure 3 It shows the use of according to Figure 2 Examples of the sequence of using flexible gripping devices to grasp and move objects; and Figure 4 An example of interdigitated electrodes in a device according to an embodiment of the present invention is shown.

[0015] It is indicated herein that elements of different embodiments may be combined to provide other embodiments without any limitation, provided that they conform to the technical concept of the invention, as will be readily understood by those skilled in the art from the description.

[0016] This specification also refers to prior art for implementing detailed features not described in this invention, such as, for example, minor elements commonly used in similar solutions in the prior art.

[0017] When referring to an element, it should always be understood as either "at least one" or "one or more".

[0018] When a list of elements or features is given in this specification, it should be understood that the solution according to the invention "comprises" or "is composed of" these elements.

[0019] When features are listed in the same sentence or list, one or more individual features of the invention may be included without being associated with other features in the list. Detailed Implementation

[0020] refer to Figure 2 The present invention relates to a flexible or “soft” gripping device 100 that can grip an object 10 on a surface (flat, curved, or irregular surface, typically the upper surface; the adaptability and effectiveness of the device are increased if the surface is curved) in a manner similar to a vacuum suction cup. However, there is no device for actively generating a vacuum, and therefore no device using pumps or the like is present.

[0021] The device comprises a gripping surface 110 (a flexible sheet-like element) having a horizontal extension with an edge 111 in the XY plane when placed. This gripping surface may also be curved when placed; however, it has an extension in the XY plane except in the lateral direction. In practice, the gripping surface is a flexible or stretchable sheet-like element with embedded electrodes (e.g., interdigitated electrodes) connected to a gripping element or "handle" 120, which is connected to the central region of the sheet-like element. This gripping element has a first end and one or more second ends extending between the first and second ends along a longitudinal direction Z extending from the lateral plane XY. The second ends are directly attached to the flexible sheet-like element 110 (in a fixed manner), i.e., no other material is involved except for a fixing device. This fixing occurs in corresponding one or more internal regions 125 of the flexible sheet-like element 110, which are positioned spaced apart from the edge 111.

[0022] Specifically, one or more corresponding inner regions 125 are positioned spaced apart from the outer edge 111 by a first minimum distance, such that in use, when the gripping element 120 is pulled along the longitudinal direction Z, at least one corresponding closed empty volume 200 is formed between the sheet and the surface of the object 10. For example, depending on the specific circumstances and the shape and composition parameters of the object 10 and the flexible sheet 110, the attachment angle α between the flexible sheet 110 and the surface is in the range of 0 < α ≤ 50°. If the inner regions are very close, the at least one closed empty volume can be a single closed empty volume; otherwise, separate and isolated closed empty volumes are generated.

[0023] According to one aspect of the invention, apart from the gripping element 120 and the portion connected to the gripping element, there is no means for bending or supporting the sheet-like member, as is the case in the prior art.

[0024] According to an embodiment of the invention, the flexible sheet 110 is pre-bent from the one or more inner regions 125 toward the edge in a concave manner relative to the second end, such as Figure 3 As shown in (a). In particular, the flexible sheet may include (or consist of) a layer of elastomer polymerized at a temperature above room temperature, preferably a layer of elastomer polymerized at a temperature between 60°C and 150°C. This layer may be a support layer located behind the layer in contact with the object—where electrodes are disposed.

[0025] Pre-bending can be important in some practical applications because in these cases, if the contact surfaces are brought close together from the edges, the entire sheet may not adhere completely to the object.

[0026] Regarding polymerization, the inventors observed in some experimental tests that if carried out at room temperature, the sheet does not pre-bend at the end of the process. Conversely, when polymerization is carried out at temperatures above room temperature (between 60 and 150 degrees Celsius in our process), the degree of pre-bending is proportional to the temperature at which polymerization takes place. This is because during the polymerization process, the volume shrinks as the elastomer changes from a solid to a liquid state. Residual stress is transferred to the underlying substrate, causing the sheet 110 to pre-bend in the desired direction. The change in volume depends on the polymerization rate, which in turn depends on the polymerization temperature. Therefore, the degree of pre-bending can be controlled by controlling the polymerization temperature.

[0027] Pre-bending is a key aspect of our electro-adhesive vacuum chuck design because it allows us to create a vacuum beneath the gripping element 120, thus preventing the formation of air bubbles or open channels communicating with the external environment at atmospheric pressure. During the pull-locking process (applying high voltage to bond the sheet to the object), the formation of air bubbles or open channels would prevent us from creating a chamber isolated from the external environment at atmospheric pressure, thus hindering the creation of a vacuum beneath the gripping element 120.

[0028] According to another aspect of the invention, the respective one or more internal regions 125 are positioned to be spaced apart from each other by a distance greater than or equal to a second minimum distance, so as to form one or more respective enclosed empty volumes 200 having the attachment angle α defined above.

[0029] According to one aspect of the invention, the first minimum distance is determined to be at least equal to the distance between the outer edge 111 and one of the corresponding inner regions 125.

[0030] According to another aspect of the invention, the second minimum distance is determined for each of the corresponding one or more inner regions 125, and is at least equal to the radius of the circumference tangent to each of the corresponding one or more inner regions.

[0031] According to a particular embodiment of the invention, one or more corresponding inner regions 125 are centered relative to the outer edge 111.

[0032] According to one aspect of the invention, one or more second ends are specifically second ends having a circular cross-section that coincides with the corresponding inner region.

[0033] According to another aspect of the invention, the gripping element 120 is provided with a valve (not shown) that connects one or more respective enclosed empty volumes 200 to the external environment. The valve can be operated manually or by electrical command to accelerate the release of the object by eliminating pressure drop.

[0034] Obviously, the gripping surface does not necessarily need to be flat when placed, as it is indeed flexible, but the gripping surface has an extension in the XY plane and can also extend in the longitudinal direction Z perpendicular to (or at least obliquely extending from) the transverse plane XY. Importantly, the flexibility of the sheet allows it to rest on the surface of the object to be gripped, whether the surface is flat, wavy, or even has a varied profile. However, a sufficiently flat surface of the object maximizes the effectiveness of the invention, but the invention is not limited to this.

[0035] In the implementation, flexibility can be determined as follows. When considering bending stiffness (or plate bending stiffness), the plate bending theory formula can be used:

[0036] Where E is Young's modulus, h is the thickness of the sheet, and ν is Poisson's ratio. According to the embodiment, the bending stiffness value D... p ≤10 - ² Pa·m³, preferably D p ≤10 - ³ Pa·m³.

[0037] If the beam bending stiffness is instead considered in an equivalent manner, D b ≤10 -4 Pa·m 4 Preferably D b ≤10 -5 Pa·m 4 It depends on the thickness of the plate.

[0038] The smaller the value in both cases, the higher the efficiency of the sheet-like component in adapting to the surface of the object, and therefore the better the gripping effect of the device according to the invention.

[0039] The lateral dimension of the mechanical support 120 is smaller than that of the sheet 110; that is, the mechanical support is fixed to a region 125 of the sheet 110, which is positioned spaced apart from the outer edge 111 of the sheet. This allows the sheet 110 freedom to adapt to the shape of the object and ensures that the peeling force generated by lifting the object through the gripping elements does not rapidly reach the edge 111 of the sheet, thereby separating the sheet from the object before the object displacement operation is completed. Therefore, the peeling force should not be concentrated at the edge of the sheet from the initial step.

[0040] Preferably, there is a large minimum distance between the outer edge 111 and the area 125 for securing the gripping element 120 to the sheet 110, so as to better resist peeling forces and allow the sheet to better adapt to the object 10.

[0041] When a voltage is applied, an electrostatic closing force is generated between the electrodes 130 integrated on or in the flexible sheet, causing the flexible sheet to deform until it conforms to the shape of the object to be grasped [6], thereby producing the so-called electroadhesive zipper effect.

[0042] Also refer to Figure 3When a pulling force is applied to lift an object via the gripping element 120 (manually, or automatically, or via a robotic arm), this force causes a partial peeling separation between the central portion of the sheet and the object. This peeling creates a volume 200 between the area used to secure the gripping element 120 to the sheet 110 and the object 10 itself (on which the sheet has been placed). Because electroadhesive forces create a seal between the sheet 110 and the object 10, this volume 200 remains isolated from the atmosphere, thereby generating a low-pressure atmosphere or even a vacuum within this volume during lifting operations, without the need for actively generating a vacuum or low pressure, such as a suction device. This vacuum atmosphere produces a suction effect, which keeps the flexible sheet 110 connected to the object 10, allowing the object to be lifted via the gripping element 120.

[0043] The suction effect can be macroscopic or microscopic, preventing the gripping device 100 from separating from the surface of the object 10.

[0044] Even if the vacuum cannot be generated, or if the vacuum level is lower than that in the case of non-porous materials, this gripping device 100 is still suitable for porous materials. The construction of the gripping element attached to the central region of the sheet—no matter how far from the edge—creates a long peel perimeter and maintains a low peel angle, thereby generating a high adhesive force [7].

[0045] This peel angle is the attachment angle α between the sheet and the object at the edge of the separation volume 200. This attachment angle α depends on the tensile force—i.e., the weight of the object—as well as the electro-adhesive force and the mechanical properties of the sheet; all other things being equal, harder materials typically have a smaller angle. Therefore, it should be determined specifically for each application. However, for some applications of the invention, the angle is 0 to 50°, preferably 0 to 50° in sexagesimal, more preferably 5 to 25° in sexagesimal, in order to more effectively form the vacuum volume 200 below the inner region 125.

[0046] It should be noted here that the value of the peel angle is not determined by the design, but depends on the characteristics of the object and the sheet, and changes during the various steps of gripping and lifting the object.

[0047] The adhesion force to the object can be further increased by modifying the geometry of the gripping element 120, thereby increasing the separation area of ​​the sheet-like parts, generating a vacuum, and increasing the length of the peel-off separation perimeter.

[0048] These different geometries are particularly useful when a vacuum cannot be generated because the object is porous or the surface is too rough. Examples of such geometries are hollow cylinders, cross shapes, and regions that divide the area for securing the gripping element to the flexible sheet into a series of smaller support pillars distributed on the surface of the sheet. Typically, there will be one or more internal regions 125 for securing the gripping element to the sheet. There may also be multiple gripping elements, all of which are included under the term "gripping element".

[0049] The sheet can be made of flexible plastics, such as, but not limited to, polyamide, polyester, Mylar, PVDF, and polypropylene; or of elastic elastomers, such as, but not limited to, silicone, TPU, nitrile rubber, SEBS, butyl rubber, acrylic elastomers, Vyton, latex, or elastic hydrogels.

[0050] Sheet-like components can also be made from a combination of different materials. For example, a sheet-like component can be a multilayer sheet-like component made from a combination of the following materials: plastic and elastomer, or plastic and hydrogel, or elastomer and hydrogel.

[0051] The surface of the flexible sheet 110 can be continuous, or it can have cuts and creases introduced to guide deformation to the desired shape (similar to origami and paper cutting structures). Reinforcing elements in the form of fibers, granules, rings, etc., can be added to strengthen the structure and guide its deformation to the desired shape.

[0052] The surface of the flexible sheet 110 that contacts the object may be coated with additional materials and / or patterned according to a specific geometry to modulate the dry adhesion forces generated with the object surface due to van der Waals forces or capillary forces. Examples of coating materials include, but are not limited to, one or more of the following: perfluoropolymers (Cytop), polytetrafluoroethylene (Teflon), talc, barium titanate—in bare form or mixed with a polymeric adhesive, hydrogels, and any additional additives that can reduce surface tension.

[0053] Electrode 130 can have different geometries. Electrodes can be coplanar and interdigitated (see reference). Figure 4 Alternatively, they can be located on different planes, one flat and the other interdigitated, or they can be located on different planes and arranged in a grid.

[0054] The electrode material can be made of different electrical or ionic conductors, such as, but not limited to: metals such as gold, iron, steel, copper, titanium, tungsten, chromium, silver, platinum, nickel, and molybdenum, used alone or in combination with polymer binders in solid or powder or fiber form; conductive polymers such as poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT-PSS); and conductive hydrogels.

[0055] To apply torque to a larger object, a series—two, three, or more—of individual gripping devices according to the invention can be used, or an electroadhesive gripping device can be combined with a mechanical pin that resists rotation of the object. This involves forming additional support members parallel to the gripping element 120, on which the sheet-like part attached to the object rests, thereby constraining its rotation along the x and y axes. These support members are not glued to the sheet-like part to avoid reducing its flexibility. Thus, these support members act as unilateral constraints.

[0056] The gripping element 120 can be rigid, flexible, or stretchable. The gripping element can be made of metal, polymer, hydrogel, ceramic, or wood. Its lateral dimension in the XY plane is typically smaller than the size of the flexible sheet with embedded electroadhesive electrodes.

[0057] The electrical connection between the electroadhesive electrode and an external battery or power source can be achieved via a flexible connector or cable, which can be external or included within the support. The power source can be embedded in the gripping element 120.

[0058] According to one aspect of the invention, the electrical connector for connecting the electrodes on the electroadhesive film to a generator or power source can also be made in the center (in the connection area 125), below or near the handle portion. This is because the cable establishing the electrical connection may also cause the film to harden, thus preventing the film from uniformly deforming on the surface of the object to eliminate the entire area and form good contact.

[0059] Reference Figure 3 An example of the gripping sequence using the device 100 according to the present invention is as follows: Bring the gripping device 100 close to the object 10 until a portion of the surface of the flexible sheet 110 approaches or contacts the surface of the object 10 to be gripped. Activate the voltage on the electroadhesion electrode 130; Electroadhesive forces cause the flexible sheet to deform so that it conforms to the shape of the surface of the object 10, including at the macroscopic and microscopic levels. The gripping element is pulled upward (here, the direction Z is the direction of gravity, but the invention is not limited to this; the object can also be lifted or moved at an angle, or even moved horizontally in the XY plane), and optionally rotated to pick up the object; The combination of electroadhesion and induced vacuum ensures that object 10 remains attached to gripping device 100; Object 10 was repositioned to its resting position; The voltage is removed from the electroadhesion electrode; the electroadhesion force and the induced vacuum both disappear, and the object 10 can be separated from the sheet 110, thereby separating from the gripping device 100.

[0060] The same device and similar operating procedures can also be used for applications other than object handling, such as holding two objects together, anchoring a drone to a wall or ceiling, or holding an object on a wall, table, or ceiling. In this regard, the gripping element 120 can have any shape suitable for this purpose.

[0061] It is emphasized here that the gripping device according to the invention also acts on objects with curved or irregular surfaces. The following are important features of the invention: the shape of the sheet is initially different from the shape of the surface, and the sheet deforms under the electro-adhesive zipper effect.

[0062] The above two or more parts (components, devices, systems) can be freely combined and regarded as part of the kit or system according to the present invention.

[0063] References [1]J. Shintake, S. Rosset, B. Schubert, D. Floreano, and H. Shea, "Versatile Soft Grippers with Intrinsic Electroadhesion Based onMultifunctional Polymer Actuators," Advanced Materials, vol. 28, no. 2, pp.231–238, 2016, doi: 10.1002 / adma.201504264. [2]J. SHINTAKE, S. Rosset, B. Schubert, D. Floreano, and H. Shea, "Electroadhesive device, system and method for gripping," US20190047157A1, Feb. 14, 2019 Accessed: Jun. 09, 2020. [Online]. Available: https: / / patents.google.com / patent / US20190047157A1 / en [3]V. Cacucciolo, J. Shintake, and H. Shea, "Delicate yet strong:Characterizing the electro-adhesion lifting force with a soft gripper" in2019 2nd IEEE International Conference on Soft Robotics (RoboSoft), Apr.2019, pp. 108–113. doi: 10.1109 / ROBOSOFT.2019.8722706. [4]M. Mastrangelo and V. Cacucciolo, "High-force soft gripper withelectroadhesion on curved objects," presented at the IEEE 5th InternationalConference on Soft Robotics (RoboSoft), Edinburgh, 2022. [5]V. Cacucciolo, H. Shea, and G. Carbone, "Peeling inelectroadhesion soft grippers," Extreme Mechanics Letters, vol. 50, p.101529, Jan. 2022, doi: 10.1016 / j.eml.2021.101529. [6]M. Mastrangelo, F. Caruso, G. Carbone, and V. Cacucciolo, "Electroadhesion zipping with soft grippers on curved objects," ExtremeMechanics Letters, vol. 61, p. 101999, Jun. 2023, doi: 10.1016 / j.eml.2023.101999. [7]L. Afferrante, G. Carbone, G. Demelio, and N. Pugno, "Adhesion ofElastic Thin Films: Double Peeling of Tapes Versus Axisymmetric Peeling ofMembranes," Tribol Lett, vol. 52, no. 3, pp. 439–447, Dec. 2013, doi:10.1007 / s11249-013-0227-6. [8]Cacucciolo, V., Shea, H., Carbone, G., 2022. Peeling in electro-adhesion soft grippers. Extreme Mechanics Letters 50, 101529. https: / / doi.org / 10.1016 / j.eml.2021.101529.

[10] US9308650 B2.

[11] US10780589 B2;

[12] WO 2014 / 059325 A1;

[13] KR 2022 0121091 A1. Preferred embodiments have been described above and variations of the invention have been proposed. However, it should be understood that those skilled in the art can make modifications and alterations without departing from the relevant scope of protection defined by the appended claims.

Claims

1. A flexible gripping device operating by electro-adhesion, the flexible gripping device comprising: - a flexible sheet (110) extending along a transversal plane (XY) and having an outer edge (111), wherein the flexible sheet (110) comprises: - a plurality of electrodes (130) located on or in the flexible sheet, the plurality of electrodes being configured and arranged to generate an electro-adhesive force on a surface of an object (10), the electrodes (130) being connectable to a power supply; - a gripping element (120) having a first end and one or more second ends, the gripping element extending along a longitudinal direction (Z) emerging from the transversal plane (XY) between the first end and the one or more second ends; wherein there are no means for actively generating a vacuum or a low pressure; the device being characterized in that: - the one or more second ends of the gripping element (120) are directly fixed to the flexible sheet (110) in a respective one or more inner regions (125), - the respective one or more inner regions (125) are positioned spaced apart from the outer edge (111); wherein the respective one or more inner regions (125) are positioned spaced apart from the outer edge (111) by a distance greater than or equal to a first minimum distance, so that, in use, at least one closed empty volume (200) is formed between the flexible sheet and the surface of the object (10) when the gripping element (120) is pulled along the longitudinal direction (Z).

2. The apparatus of claim 1, wherein, the first minimum distance being determined to be at least equal to a distance between the outer edge (111) and one of the respective one or more inner regions (125).

3. The apparatus of claim 1 or 2, wherein, the respective one or more inner regions (125) are positioned spaced apart from each other by a distance greater than or equal to a second minimum distance, so as to form one or more respective closed empty volumes (200).

4. The apparatus of claim 3, wherein, the second minimum distance being determined for each of the respective one or more inner regions (125), and being at least equal to a radius of a circumference inscribed within said each of the respective one or more inner regions.

5. The apparatus of any one of claims 1 to 4, wherein, the respective one or more inner regions (125) are centered with respect to the outer edge (111).

6. The device according to one of claims 1 to 5, wherein, in the at least one closed empty volume, an angle of attachment a of the flexible sheet (110) with the surface is in the range 0 < a < 50°, according to shape and composition parameters of the object (10) and of the flexible sheet (110).

7. The apparatus of claim 6, wherein, the angle of attachment a is 0 < a < 30°.

8. The device according to one of claims 1 to 7, wherein, the plurality of electrodes (130) are interdigital electrodes.

9. The device according to one of claims 1 to 8, wherein, the flexible sheet (110) is made of one or more materials selected from: flexible plastic, polyamide, polyester, Mylar, PVDF, polypropylene, or elastomer.

10. The apparatus of claim 9, wherein, The elastomer of which said elastic body is selected from: silicone, TPU, nitrile rubber, SEBS, butyl rubber, acrylic elastomer, Vyton, latex, or elastic hydrogel.

11. The device according to one of claims 1 to 10, wherein, Said power supply device is embedded in said gripping element (120).

12. The device according to one of claims 1 to 11, wherein, Said longitudinal direction (Z) is the direction of gravity.

13. The device according to one of claims 1 to 12, wherein, The bending stiffness D of the flexible sheet (110) p ≤ 10 - Pa.m3.

14. The apparatus of claim 13, wherein, The bending stiffness D of the flexible sheet (110) p ≤ 10 - ³ Pa·m³.

15. The device according to one of claims 1 to 13, wherein, Said one or more second end portions is a second end portion.

16. The apparatus of claim 15, wherein, Said second end portion has a circular cross section coinciding with said respective inner area.

17. The device according to one of claims 1 to 16, wherein, In said gripping element (120) there is provided a valve which communicates said one or more respective closed empty volumes (200) with the external environment, said valve being able to be opened by manual or electric command to accelerate the release of said object.

18. The device according to one of claims 1 to 17, wherein, There are no means for bending or supporting said sheet, except for said gripping element (120) and the part connected to it.

19. The apparatus of claim 18, wherein, Said flexible sheet (110) is pre-bent in a concave manner with respect to said second end portion starting from said one or more inner areas (125) towards said edge.

20. The apparatus of claim 21, wherein, Said flexible sheet comprises a layer made of an elastomer polymerized at a temperature state above room temperature, preferably said flexible sheet comprises a layer made of an elastomer polymerized at a temperature state from 60°C to 150°C.

21. The device according to one of claims 1 to 20, wherein, Between said electrodes (130) and said power supply device there is provided an electrical connection formed at one or more of said second end portions.

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