A flexible gripping device working by electroadhesion

Abstract

The present invention relates to a flexible gripping device working by electroadhesion, comprising a flexible foil (110) extending along a transverse plane (XY) and with an outer edge (111) and a gripping element (120) extending along a longitudinal direction (Z) perpendicular to said transverse plane (XY). The gripping element can be manual or part of another machine. In order to create electroadhesion, the flexible foil (110) comprises a plurality of electrodes (130) configured and arranged to generate an electroadhesion force when the foil is brought close, in the transverse extension thereof, to a surface of an object. The electrodes (130) are connectable to electrical power supply means which can also be embedded into the gripping element (120). In order to avoid a detachment of the foil in use, the gripping element (120) is fixed to the flexible foil (110) in one or more inner regions (125) which are located at a distance from said outer edge (111), preferably so that, upon pulling the gripping element, perpendicularly (Z) to the transverse plane (XY), at the edge of said one or more inner regions, the angle of attachment of the foil to the surface is less than 30° and a vacuum volume 200 is created below the inner regions 125.

Description

[0001] A flexible gripping device working by electroadhesion

[0002] The present invention relates to a flexible gripping device working by electroadhesion.

[0003] The architecture is that of a vacuum pad but there is no connection to a vacuum pump. In fact, the grip occurs as a combination of electrostatic forces between the device and the object and the force of the passive vacuum caused by electroadhesion and the forces themselves of object detachment.

[0004] Background art

[0005] Gripping devices based on electroadhesion can lift objects using the adhesion force generated by edge electric fields [1], [2].

[0006] Generally, soft electroadhesion grippers can generate large holding forces when grasping objects from the sides, ideally wrapping the fingers or jaws about the object [3], [4].

[0007] Conversely, gripping forces tend to be low when grasping objects from the top surface, similarly to a vacuum pad gripper. The reason for the low electroadhesion forces when grasping an object from the top surface is the peeling detachment between the gripper and the object surface [5].

[0008] This is shown in Figure 1, where the effect of the posture on the gripping force of a soft electroadhesion gripper is shown [3]; the grip from the top surface (rightmost case) involves highly low forces (order of mN), thus preventing any practical application.

[0009] Document

[0010] uses electroadhesion forces but in a vacuum pad device, where a dedicated channel is present (76 in Figure 9) for air suction (active vacuum creation means). Electroadhesion is only used to increase the air tightness of a conventional vacuum pad.

[0010] Document

[0011] uses an electroadhesive membrane fully supported by a thicker and more rigid element, thus the resulting gripping device cannot conform to every surface and take advantage of the electroadhesive zipping [6]. This is a low efficiency and low usability electroadhesive device.

[0011] Document

[0012] describes an electroadhesive gripping system with a vacuum creation gripper. The gripper can comprise an electroadhesive surface associated with one or more electrodes and a supporting carrier structure coupled to the electroadhesive surface. The support couples to the back side of the electroadhesive surface so as to define at least partially a shape of the electroadhesive surface. The support is configured to bend between a curved shape and a non-curved shape. An expansion arm is configured to apply force to the support so as to bend the support from the non-curved shape to the curved shape. When positioned next to a substrate, the stretching motion of the support can cause the electroadhesive surface to be vacuum sealed to the substrate. However, this solution is not sufficiently effective since it comprises a support layer behind the electroadhesive sheet and active folding means. In particular, the presence of "spreading arms" (422 in Figure 8B) and structures that create the uncurling of the membrane from curved to flat stiffen the structure and thus effectively prevent the creation of a seal between the membrane and the object unless the spreading arms are perfectly flat and the object surface is also perfectly flat, which in fact is not achievable in industrial applications. A misalignment of just a few pm (10-50) between the gripper structure and the object surface creates in fact channels in which air can circulate, making the formation of a passive vacuum impossible. Moreover, as it can be seen from Figure 9A, the elements 538a and 538b transfer the lifting forces to the edges of the membrane. This causes peeling from the edges, thus resulting in very high peeling angles, leading to very low peeling forces, such as in two-finger electroadhesive grippers.

[0012] Document

[0013] describes an electroadhesive gripper comprising: a base; a pair of gripping arms hinged and coupled to both end parts of the base and facing each other; an adhesive pad structured with electroadhesive film consisting of an insulating body, an electrode arranged on the insulating body, and a conductive line arranged on the insulating body and electrically connected to the electrode to be supported by each gripping arm; and power supply means electrically connected to the electrode of the adhesive pad to apply power. Therefore, the electroadhesive gripper can have an excellent gripping force and can grip objects of various shapes by means of the adhesive pad structured with electroadhesive film and the two gripping arms supporting both ends of the adhesive pad. Having arms connected to the ends of the electroadhesive pad makes the device complex and expensive and not always effective, being capable of adapting only to a few objects with a well-defined curvature. The element 53 in Figure 1, being connected to the electroadhesive membrane up to the edges, stiffens it and does not allow the creation of a close contact between the membrane and the object surface, unless the element 53 and the object surface are made with perfectly matching shapes with tolerances less than 10-50 pm, having no practical application in the gripping of industrial objects, in which the shapes cannot perfectly match the shape of the gripper with such low tolerances. This results in the formation of channels containing air which do not allow the formation of a passive vacuum. Moreover, the extension of the element 53 up to the edge transfers the lifting forces to the edge of the membrane, thus creating the formation of peeling from this edge and thus the detachment with high peeling angles and consequent low forces. Moreover, the shape of the element 53 and the extension thereof up to the edge does not allow the creation of a vacuum volume when lifting the membrane since this is not free to deform precisely because of the element 53 and the peeling from the edges also connects the entire central part of the membrane to the external air.

[0013] The need remains for an electroadhesive gripper which can also be used on irregular surfaces, and is simple, affordable and effective.

[0014] Purpose and object of the invention

[0015] It is the object of the present invention to provide a flexible gripping device which solves the problems and overcomes the drawbacks of the prior art.

[0016] The present invention relates to a flexible gripping device according to the appended claims.

[0017] Detailed description of embodiments of the invention

[0018] List of Figures

[0019] The invention will now be described by way of nonlimiting illustration, with particular reference to the figures in the accompanying drawings, in which:

[0020] - Figure 1 shows the effect of the posture on the gripping force of a soft electroadhesion gripper [3]; the grip from the top surface (rightmost case) involves highly low forces (order of mN), thus preventing any practical application [8];

[0021] - Figure 2 shows a diagram of an electroadhesion vacuum pad attached to an upper surface of an object, according to an embodiment of the invention;

[0022] - Figure 3 shows an example of a sequence of gripping and moving an object with a flexible gripping device according to Figure 2; and

[0023] - Figure 4 shows an example of interdigitated electrodes in a device according to an embodiment of the invention.

[0024] It is here specified that elements of different embodiments can be combined to provide further embodiments, without restrictions, while respecting the technical concept of the invention, as those skilled in the art will effortlessly understand from the description .

[0025] The present description also refers to the prior art for the implementation thereof in relation to the detail features not described, such as elements of minor importance usually used in the prior art in solutions of the same type, for example.

[0026] When an element is introduced, it is always understood that there can be "at least one" or "one or more".

[0027] When a list of elements or features is given in this description, it is understood that the finding according to the invention "comprises" or alternatively "consists of" such elements.

[0028] When listing features within the same sentence or bullet list, one or more of the single features can be included in the invention without connection with the other features on the list.

[0029] Embodiments

[0030] With reference to Figure 2, the present invention relates to a flexible or "soft" gripping device 100 which can grip objects 10 on a surface thereof (a flat or curved or irregular surface, usually an upper side, if it is curved the adaptation and thus the effectiveness of the device are increased) in a manner similar to a vacuum pad. However, there are no means for actively creating a vacuum, therefore there are no means which use a pump or the like.

[0031] The device consists of a gripping surface 110 (flexible foil) which has a horizontal extension in the plane XY, with an edge 111, at rest. Such a gripping surface can also be curved at rest, in any case it has an extension in the plane XY in addition to one in the transverse direction). In practice, it is a flexible or extensible foil with embedded electrodes (e.g., interdigitated electrodes) connected to a gripping element or "handle" 120 connected in the central area thereof of the sheet. Such a gripping element has a first end and one or more second ends between which it extends, along a longitudinal direction Z emerging from the transverse plane XY. The second ends are connected (fixed) directly to the flexible foil 110, i.e., without the interposition of other materials apart from the fixing means. Fixing occurs in respective one or more inner regions 125 of the flexible foil 110, located at a distance from the edge 111.

[0032] In particular, the respective one or more inner regions 125 are located at a first minimum distance from said outer edge 111 such as to create in use, upon pulling said gripping element 120 along the longitudinal direction Z, at least one respective closed empty volume 200 between said foil and said surface of the object 10, for example, from time to time, with an angle of attachment a of the flexible foil 110 to said surface within the range 0 < a 50° as a function of shape and composition parameters of object 10 and flexible foil 110. The at least one closed empty volume can be a single closed empty volume if the inner regions are very close, otherwise individual and separate closed empty volumes are generated.

[0033] According to an aspect of the invention, there are no means for bending or supporting said foil other than and connected to said gripping element 120, such as those of the prior art.

[0034] According to an embodiment of the invention, the flexible foil 110 is pre-bent starting from said one or more inner regions 125 towards the edge in a concave manner with respect to said second end, as shown in Figure 3(a). In particular, the flexible foil can comprise (or consist of) a layer of an elastomer polymerized at a temperature above room temperature, preferably between 60 and 150°C. The layer can be a support layer behind a layer in contact with the object, in which the electrodes are provided.

[0035] The pre-bending can be important in some cases of practical use because, in such cases, bringing the contact surface close to each other starting from the edges cannot allow the complete adhesion of the entire foil to the object.

[0036] As for the polymerization, it has been observed in some experimental tests by the Inventors that, if it is carried out at room temperature ,the membrane is not pre-bent at the end of the process. Instead, by carrying out the polymerization at temperatures above the room temperature (in our process, in a range between 60 and 150 degrees), the pre-bending scales with the temperature at which the polymerization is carried out. This is because during the polymerization process, when the state of the elastomer switches from solid to liquid, the volume shrinks. The transmission of the residual stresses to the lower substrate results in the foil 110 being pre-bent in the desired direction. The volume variation depends on the polymerization speed which, in turn, depends on the polymerization temperature. For this reason, it is possible to control the pre-bending degree by controlling the polymerization temperature.

[0037] Pre-bending is a crucial aspect in the design of our electroadhesive vacuum pad, since it allows us to obtain the formation of the vacuum below the gripping element 120 thus avoiding the formation of air bubbles or open channels communicating with the external environment at atmospheric pressure. During the zipping process (the membrane conforming to the object following the activation of the high voltage), the formation of bubbles or open channels would not allow us to obtain a chamber isolated from the external environment at atmospheric pressure and thus to obtain the vacuum below the gripping element 120.

[0038] According to a different further aspect of the invention, said respective one or more inner regions 125 are mutually located at a distance greater than or equal to a second minimum distance such as to create one or more respective closed empty volumes 200 with an angle of attachmenta as defined above. According to an aspect of the invention, the first minimum distance is 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.

[0039] According to a further aspect of the invention, the second minimum distance is determined for each of the respective one or more inner regions 125 and is at least equal to a radius of a circumference inscribed in said each of the respective one or more inner regions.

[0040] According to a particular embodiment of the invention, the respective one or more inner regions 125 are central with respect to said outer edge 111.

[0041] According to an aspect of the invention, the one or more second end are a second end particularly having a circular cross-section coinciding with said respective inner region.

[0042] According to a different aspect of the invention, said gripping element 120 is provided with a valve (not shown) which connects said one or more respective closed empty volumes 200 to the external environment, the valve being openable by manual or electric command, so as to speed up the release of the object by eliminating depressurization .

[0043] It is apparent that the gripping surface does not necessarily need to be flat at rest, since it is flexible indeed, but it has an extension in the plane XY and at the same time it can also extend in a longitudinal direction Z perpendicular to (or at least also obliquely emerging from) the transverse plane XY. Importantly, the flexibility of the foil allows it to rest on the surface of the object to be gripped, whether it is flat or wavy or even with a variegated profile. However, a sufficiently flat surface of the object maximizes the effect of the present invention, which however is not limited to such a case.

[0044] In an embodiment, the flexibility can be determined as follows. When considering the flexural stiffness (or plate flexural rigidity), it is possible to use the formula of the plate bending theory:

[0045] DP= E*h3 / (12(l-v)) where E is the Young's modulus, h is the thickness of the foil and v is the material Poisson's ratio. The flexural stiffness values Dp are according to an embodiment < 10-2Pa-m3, preferably < 10-3Pa-m3.

[0046] If instead the beam bending stiffness is considered in an equivalent manner, Db 10-4Pa-m4, preferably Db 10-5Pa-m4depending on the thickness of the plate.

[0047] The narrower values in both cases indicate a greater efficiency of adaptation of the foil to the object surface and therefore a better grip of the device according to the invention.

[0048] The transverse dimension of the mechanical support 120 is smaller than the size of the foil 110, i.e., the mechanical support is fixed to the foil 110 in a region 125 which is at a distance from the outer edge 111 of the foil. A margin of freedom is thus left to the foil 110 when adapting to the shape of the object and it is ensured that the peeling forces generated by lifting the object by means of the gripping element do not quickly reach the edge of the foil 111, thus causing the foil to detach from the object before the object displacement operation has been carried out. Therefore, the peeling forces should not be localized on the edge of the foil from the initial steps.

[0049] It is preferable that there is a large minimum distance between the outer edge 111 and the region 125 for fixing the gripping element 120 to the foil 110, so as to better protect against peeling forces and allow a better adaptation of the foil to the object 10.

[0050] When an electrical voltage is applied, electrostatic closing forces are generated between the electrodes 130 integrated on or in the flexible foil, deforming the flexible foil until it conforms to the shape of the object to be gripped [6] thus generating the so-called electroadhesive zipping.

[0051] Also referring to Figure 3, when a pulling force is applied, through the gripping element 120 (manual or equivalently automatic or by means of a robotic arm), to lift the object, such a force creates a local peeling detachment of the central part of the foil from the object. Such a peeling creates a volume 200 between the region for fixing the gripping element 120 to the foil 110 and the object 10 itself (the surface thereof on which the foil has been placed). By virtue of the electroadhesion forces which create a seal between the foil 110 and the object 10, such a volume 200 remains disconnected from the atmosphere, generating therein, during the lifting operation, a low pressure atmosphere or even a vacuum, without the presence of means for the active generation of vacuum or low pressure, such as suction mean, for example s. Such a vacuum atmosphere creates a suction effect which keeps the flexible foil 110 and the object 10 connected, thus allowing the object to be lifted by means of the gripping element 120.

[0052] The suction effect can be macroscopic or microscopic, preventing the gripping device 100 from detaching from the surface of the object 10.

[0053] Such a gripping device 100 still works on porous objects, even if it is not possible to create the vacuum described above or if the degree of vacuum is lower than in the case of non-porous objects. The configuration with the gripping element connected to the central region of the foil, however far from the edges, creates a long peeling perimeter and keeps the peeling angle low, generating a high adhesion force [7].

[0054] Such a peeling angle is the angle of attachment a of the foil to the object at the edge of such a detachment volume 200. Such an angle of attachment a is a function of the pulling force, therefore of the weight of the object, as well as of the electroadhesion force and the mechanical features of the foil (more rigid materials generally have lower angles, other parameters being equal). Therefore, it should be specifically determined for each application. However, for some applications of the invention, it is from 0 to 50°, preferably from 0 to 50° sexagesimal, even more preferably from 5 to 25° sexagesimal, in order to create a vacuum volume 200 below the inner regions 125 in a more effective manner. It should be noted here that the value of the peeling angle is not determined by design but it is a value which depends on the features of the object and the membrane, and it changes during the various steps of gripping and lifting the object.

[0055] Such a force of adhesion to the object can be further increased by modifying the geometry of the gripping element 120 to further increase the detachment area of the foil so as to create the vacuum and increase the length of the peeling detachment perimeter.

[0056] These different geometries are particularly useful when the vacuum cannot be created because the object is porous or the surface is too rough, for example. Examples of such geometries are a hollow cylinder, a cross shape and the division of the region for fixing the gripping element to the flexible foil into a series of smaller pillars distributed on the surface of the foil. In general, one or more inner regions 125 for fixing the gripping element to the foil will be present. There can also be multiple gripping elements, all included under the term "gripping element".

[0057] The foil can be made of flexible plastic such as, but not limited to, polyamide, polyester, Mylar, PVDF, polypropylene, or elastic elastomer such as, but not limited to, silicone, TPU, nitrile rubber, SEBS, butyl rubber, acrylic elastomers, Vyton, latex, or elastic hydrogels.

[0058] The foil can also be made from a combination of different materials. For example, it can be a multilayer foil in a combination of: plastic and elastomers or plastic and hydrogels or elastomers and hydrogels.

[0059] The surface of the flexible foil 110 can be continuous, or cuts and folds can be introduced to guide the deformation into the desired shape (similar to origami and kirigami structures). Stiffeners in the form of fibers, particles, rings, etc. can be added, both to strengthen the structure and to guide the deformation thereof into the desired shape.

[0060] The surface of the flexible foil 110 contacting the object can be coated with additional materials and / or patterned according to specific geometries to adjust the dry adhesion due to Van der Waals forces or capillary forces with the object surface. Examples of coating materials include one or more, without limitation, of: Cytop, Teflon, talcum powder, barium titanate, in bare form or mixed with a polymer binder, hydrogel and any additional additive which can reduce surface tension.

[0061] The electrodes 130 can have different geometries. They can be coplanar and interdigitated (see Figure 4) or can lie on different planes and be one flat and the other interdigitated, or can lie on different planes and be arranged in a grid.

[0062] The materials of the electrodes 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, molybdenum, in solid form or as powder or fibers, alone or combined with a polymer binder, conductive polymers such as PEDOT-PSS, conductive hydrogels. To apply torques on larger objects, it is possible to use a series of 2, 3 or more single gripping devices according to the invention, or an electroadhesion gripping device can be used in combination with mechanical pins which oppose the rotation of the object. This involves creating other pillars in parallel to the gripping member 120 on which the foil, adhered to the object, rests, constraining the rotation thereof along the axes x and y. These pillars are not glued to the foil, so as not to reduce the flexibility thereof. Therefore, they act as unilateral constraints.

[0063] The gripping element 120 can be rigid, flexible or extensible. It can be made of metals, polymers, hydrogel, ceramics, wood. The transverse dimension in the plane XY is generally smaller than the size of the flexible foil with embedded electroadhesion electrodes.

[0064] The electrical connections between the electroadhesion electrodes and an outer battery or a power supply can be made by means of flexible connections or electrical cables, which are external or included in the support. The power supply can be embedded into the gripping element 120.

[0065] According to an aspect of the invention, the electrical connections which connect the electrodes onto the electroadhesive membrane to the generator or power supply can also be made in the center (in the connection region 125), below or close to the handle. This is because the cables which create the electrical connections can also contribute to stiffening the membrane and thus not allowing the homogeneous deformation thereof on the object surface to remove the entire area and create a good contact.

[0066] With reference to Figure 3, an example of a gripping sequence with the device 100 of the invention is as follows:

[0067] - the gripping device 100 is brought close to the object 10 until a part of the surface of the flexible foil 110 is proximal to or in contact with the surface of the object 10 to be grasped;

[0068] - the voltage on the electroadhesion electrodes 130 is activated;

[0069] - the electroadhesion forces cause the flexible foil to deform so that it conforms to the shape of the surface of the object 10, both at macroscopic level and in microscale;

[0070] - the gripping element is pulled upwards (here the direction Z is that of the gravitational force, without limiting the invention, in which the object can also be lifted or moved obliquely or even horizontally in the plane XY) and optionally rotated to pick up the object;

[0071] - a combination of electroadhesion forces and induced vacuum ensure that the object 10 remains attached to the gripping device 100;

[0072] - the object 10 is repositioned in the rest position;

[0073] - the voltage is removed from the electroadhesion electrodes; both the electroadhesion forces and the induced vacuum disappear and the object 10 can detach from the foil 110 and thus from the gripping device 100. The same device and a similar procedure can also be used for applications other than the object pick-and- place, such as holding two objects together or anchoring drones to walls or ceilings or holding objects on walls, desks or ceilings. In this respect, the gripping element 120 can have any shape suited to the purpose.

[0074] It is emphasized herein that the gripping device according to the invention also works with objects with curved or irregular surfaces. The fact that the shape of the foil and the shape of the surface are initially different and that the foil deforms under the effect of electroadhesive zipping is an important feature of the present invention.

[0075] Two or more of the parts (elements, devices, systems) described above can be freely associated and considered as a part kit or system according to the invention.

[0076] References

[0077] [1] J. Shintake, S. Rosset, B. Schubert, D. Floreano, and H. Shea, "Versatile Soft Grippers with Intrinsic Electroadhesion Based on Multifunctional Polymer Actuators," Advanced Materials, vol. 28, no. 2, pp. 231- 238, 2016, doi: 10.1002 / adma.201504264.

[0078] [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 / US20190047157Al / en [3] V. Cacucciolo, J. Shintake, and H. Shea, "Delicate yet strong: Characterizing the electro-adhesion lifting force with a soft gripper" in 20192nd IEEE International Conference on Soft Robotics (RoboSoft), Apr. 2019, pp. 108-113. doi: 10.1109 / ROBOSOFT.2019.8722706.

[0079] [4] M. Mastrangelo and V. Cacucciolo, "High-force soft gripper with electroadhesion on curved objects, " presented at the IEEE 5th International Conference on Soft Robotics (RoboSoft), Edinburgh, 2022.

[0080] [5] V. Cacucciolo, H. Shea, and G. Carbone, "Peeling in electroadhesion soft grippers, " Extreme Mechanics Letters, vol. 50, p. 101529, Jan. 2022, doi: 10.1016 / j.eml.2021.101529.

[0081] [6] M. Mastrangelo, F. Caruso, G. Carbone, and V. Cacucciolo, "Electroadhesion zipping with soft grippers on curved objects," Extreme Mechanics Letters, vol. 61, p. 101999, Jun. 2023, doi: 10.1016 / j.eml.2023.101999.

[0082] [7] L. Afferrante, G. Carbone, G. Demelio, and N. Pugno, "Adhesion of Elastic Thin Films: Double Peeling of Tapes Versus Axisymmetric Peeling of Membranes, " Tribol Lett, vol. 52, no. 3, pp. 439-447, Dec. 2013, doi: 10.1007 / sll249-013-0227-6.

[0083] [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.

[0084]

[0010] US9308650 B2.

[0085]

[0011] US10780589 B2;

[0086]

[0012] WO 2014 / 059325 Al;

[0087]

[0013] KR 2022 0121091 Al. Preferred embodiments have been described above and variations of the present invention have been suggested, but it should be understood that those skilled in the art may make modifications and changes without departing from the related scope of protection, as defined by the appended claims.

Claims

CLAIMS1. A flexible gripping device working by electroadhesion, comprising:- a flexible foil (110) extending along a transverse plane (XY) and with an outer edge (111), wherein the flexible foil (110) comprises- a plurality of electrodes (130) on or in said flexible foil, configured and arranged to generate an electroadhesion force on a surface of an object (10), the electrodes (130) being connectable to electrical power supply means;- a gripping element (120) with a first end and one or more second ends between which it extends along a longitudinal direction (Z) emerging from the transverse plane (XY), wherein there are no means for the active generation of vacuum or low pressure; the device being characterized in that:- the one or more second ends of the gripping element (120) are fixed directly to said flexible foil (110) in respective one or more inner regions (125),- the respective one or more inner regions (125) are located at a distance from said outer edge (111); wherein said respective one or more inner regions (125) are located at a distance greater than or equal to a first minimum distance from said outer edge (111) such as to create in use, upon pulling said gripping element (120) along the longitudinal direction (Z), at least one closed empty volume (200) between said flexible foil andsaid surface of the object (10).

2. A device according to claim 1, wherein the first minimum distance is 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. A device according to claim 1 or 2, wherein said respective one or more inner regions (125) are mutually located at a distance greater than or equal to a second minimum distance such as to create one or more respective closed empty volumes (200).

4. A device according to claim 3, wherein said second minimum distance is determined for each of the respective one or more inner regions (125) and is at least equal to a radius of a circumference inscribed in said each of the respective one or more inner regions.

5. A device according to any one of claims 1 to 4, wherein said respective one or more inner regions (125) are central with respect to said outer edge (111).

6. A device according to one of claims 1 to 5, wherein from time to time in the at least one closed empty volume, the flexible foil (110) has an angle of attachment a to said surface within the range 0 < a < 50° as a function of the shape and composition parameters of object (10) and flexible foil (110).

7. A device according to claim 6, wherein the angle of attachment a is 0 < a < 30°.

8. A device according to one of claims 1 to 7, wherein said plurality of electrodes (130) are interdigitated electrodes .

9. A device according to one of claims 1 to 8, wherein said flexible foil (110) is made of one or more materials selected from: flexible plastic, polyamide, polyester, Mylar, PVDF, polypropylene, or elastomers.

10. A device according to claim 9, wherein the elastic elastomers are selected from the group comprising: silicone, TPU, nitrile rubber, SEBS, butyl rubber, acrylic elastomers, Vyton, latex, or elastic hydrogels.

11. A device according to one of claims 1 to 10, wherein the electric power supply means are embedded into said gripping element (120).

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

13. A device according to one of claims 1 to 12, wherein the flexible foil (110) has a flexural rigidity Dp < 10-2Pa-m3.

14. A device according to claim 13, wherein theflexible foil (110) has a flexural rigidity Dp < 10-3Pa-m3.

15. A device according to one of claims 1 to 13, wherein the one or more second ends is a second end.

16. A device according to claim 15, wherein the second end has a circular cross-section coinciding with said respective inner region.

17. A device according to one of claims 1 to 16, wherein a valve is provided in said gripping element (120), which connects said one or more respective closed empty volumes (200) to the external environment, the valve being openable upon manual or electric command, so as to speed up the release of the object.

18. A device according to one of claims 1 to 17, wherein there are no means for bending or supporting said foil other than and connected to said gripping element (120).

19. A device according to claim 18, wherein the flexible foil (110) is pre-bent starting from said one or more inner regions (125) towards the edge in a concave manner with respect to said second end.

20. A device according to claim 21, wherein the flexible foil comprises a layer made of an elastomerpolymerized at a temperature above the room temperature, preferably from 60 to 150°C.

21. A device according to one of claims 1 to 20, wherein electrical connections are provided between said plurality of electrodes (130) and the power supply means, said electrical connections being obtained in said one or more second ends.

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