WO2010063622A1

WO2010063622A1 - An adhesive pad

Info

Publication number: WO2010063622A1
Application number: PCT/EP2009/065801
Authority: WO
Inventors: Alessandro Mattozzi
Original assignee: ABB Research Ltd Switzerland
Current assignee: ABB Research Ltd Switzerland
Priority date: 2008-12-02
Filing date: 2009-11-25
Publication date: 2010-06-10
Anticipated expiration: 2011-06-02

Abstract

An adhesive pad (11, 21, 51, 71, 91) comprising a plurality of flexible micro or nano pillars (12, 22, 52, 72, 92) arranged on its outer surface (13, 23, 53, 73, 93), wherein each one of said pillars is arranged with one end attached to said outer surface and the other end extending in a direction away from said outer surface, and has an essentially flat top surface (27, 57, 77, 97) which is inclined so that the normal to said top surface deviates from the longitudinal direction of the pillar, wherein the top surface of each one of said pillars is inclined so that the normal to the top surface is directed away from a line being normal to the outer surface and emanating from a centre point (13c, 23c, 53c, 93c) on the outer surface.

Description

An adhesive pad

FIELD OF THE INVENTION AND PRIOR ART

The invention relates to an ad hesive pad accordi ng to the preamble of claim 1 or 6.

During robot assisted handling of delicate items such as vegetables, electronics and LCD panels it is desirable that a gripping device performing the handling action do so with a minimum of force applied to the items, otherwise said items can be damaged.

Geckos are known for their ability to climb on walls and roofs and that ability is due to the surface structure of the toes of the gecko. The adhesive mechanism of the gecko's toes has been widely studied and biomimetic adhesive surfaces have been developed. Such structures can also be useful for a gripping device handling the above mentioned delicate items, since a grip- ping device comprising such an adhesive surface can lift delicate items by the use of van der Waals forces exclusively, i.e. no actual gripping is needed.

US 2008025822 discloses a device and method for handling an object using one or more directional adhesive structures to adhere to the object using van der Waals forces.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a new adhesive pad.

This object is according to the invention achieved by means of an adhesive pad having the features defined in claim 1 and an adhesive pad according to the features defined in claim 6. The invention relates to an adhesive pad comprising a plurality of flexible micro or nano pillars arranged on its outer surface, wherein each one of said pillars:

^■ is arranged with one end attached to said outer sur- face and the other end extending in a direction away from said outer surface, and

^■ has an essentially flat top surface which is inclined so that the normal to said top surface deviates from the longitudinal direction of the pillar, wherein the top surface of each one of said pillars is inclined so that the normal to the top surface is directed away from a line being normal to the outer surface and emanating from a centre point on the outer surface.

In this description and the subsequent claims the term "centre point on the outer surface" refers to a point in the centre of the pillars of the outer surface, i.e. if only a part of the outer surface comprises pillars the centre point is located in the centre of that part. If the adhesive pad comprises more than one set of pillars, each one of the sets of pillars has its own centre point.

An adhesive pad having the above mentioned features will upon application of said pad to an object adhere to the object to which it is applied. The flexible pillars of the pad will bend so that the inclined top surfaces of the pillars will be in contact with the object. Due to the fact that the top surfaces of said pillars are inclined so that the normals to the top surfaces are directed away from the centre of the outer surface the van der Walls forces acting upon the pillars' top surfaces from the surface of the object are all directed inwards, to a point on the surface of the object situated directly under the centre of the pad. This results in a steady state situation where all the forces acting on the object from the pillars of the adhesive pad are directed outwardly from said point, thus keeping the pillars in the bent state. If all inclined top surfaces of the pillars would be directed in the same direction, a steady state of bent pillars would not be obtained.

According to one embodiment of the adhesive pad comprises a grid-like detachment member arranged in parallel with said outer surface so that each hole in the member surrounds at least one pillar, preferably only one pillar, said member being movable in a direction perpendicular to the outer surface in the longitudinal direction of the pillars towards their top surface to detach the adhesive pad from an object to which the adhesive pad is attached when it is in use. When the grid-like detachment member is moved towards the top surface of the pillars, the member straightens the pillars and the top surfaces detach from the surface of the object. In an alternative embodiment the grid-like detachment member consists of a flexible material, which can be stretched and compressed in all directions parallel to the outer surface of the pad. By compressing the member inwards towards the centre point of the outer surface, the adhering forces from the surface of the object to the top surfaces of the pillars are counteracted and the above mentioned steady state is interrupted, whereby the adhesive pad detach from the surface of the object to which it is attached. A further advantage with the grid- like detachment member is that it during detachment of the adhesive pad from an object also cleans the pillars from parti- cles and dirt by the movement of the member along the longitudinal direction of the pillars towards their top surface.

According to another embodiment of the invention the adhesive pad comprises detachment means configured to pull the centre of the outer surface away from an object to which the adhesive pad is attached when it is in use. The periphery of the outer surface is thus folded around an axis extending perpendicular outwards from the outer surface, like the folding of an umbrella. The detachment means can also be used in the opposite way when attaching the adhesive pad to an object. The periphery of the folded outer surface is brought in contact with the surface of the object to which it is to be attached. When the periphery reaches the object the centre of the outer surface is pushed towards the object by means of the detachment means, the outer surface is unfolded and the pillars of the adhesive pad are brought in contact with the object. This way the top surfaces of the pillars are dragged along the object in a direction outwards from the centre towards the periphery of the outer surface. The pillars are bent in a direction inwards towards the centre of the outer surface and the inclined top surfaces of the pillars are contacting the object. During detachment the pillars are displaced along the object in the opposite direction, which causes a detachment of each one of said pillars from the surface of the object.

According to another embodiment of the invention the top surface is inclined with an angle within the range of 20°-70°, preferably 30°-60°, most preferred 40°-50°, with respect to the longitudinal direction of the pillar. An inclined top surface provide for a large contact surface of the pillar to an object when the adhesive pad is in use.

According to another embodiment of the invention the material of the pillars comprises a polymer, preferably silicone. In order to provide the sufficient adhesion of the adhesion pad to an ob- ject it is necessary that the pillars can be bent and take a shape appropriate to the surface of the object. A polymeric material provides the necessary flexibility to achieve that.

The invention also relates to an adhesive pad comprising a plurality of flexible micro or nano pillars arranged on its outer surface, wherein each one of said pillars:

^■ is arranged with one end attached to said outer surface and the other end extending in a direction away from said outer surface, and ^■ has an essentially flat top surface, which is inclined so that the normal to said top surface deviates from the longitudinal direction of the pillar, wherein the top surface of each one of said pillars is inclined so that the normal to the top surface is directed towards a line being normal to the outer surface and emanating from a centre point on the outer surface. An adhesive pad having the above mentioned features will upon application of said pad to an object adhere to the object to which it is applied. The flexible pillars of the pad will bend so that the inclined top surfaces of the pillars will be in contact with the object. Due to the fact that the top surfaces of said pillars are inclined so that the normals to the top surfaces are directed towards a line being normal to the outer surface and emanating from the centre of the same the van der Waals forces acting upon the pillars' top surfaces from the object are all directed outwards towards the periphery of the outer surface. This results in a steady state situation where all the forces acting on the object from the pillars of the adhesive pad are directed inwardly from said periphery, thus keeping the pillars in the bent state. If all inclined top surfaces of the pillars would be directed in the same direction, a steady state of bent pillars would not be obtained.

According to another embodiment of the invention the adhesive pad comprises detachment means configured to pull the periphery of the outer surface away from an object to which the adhesive pad is attached when it is in use. The periphery of the outer surface is thus folded around an axis extending perpendicular inwards from the outer surface, like the folding of an umbrella. The detachment means can also be used in the opposite way when attaching the adhesive pad to an object, by closing the centre of the folded outer surface to the object to which it is to be attached. When the centre reaches the object the periphery of the outer surface is pushed towards the object by means of the detachment means, the outer surface is unfolded and the pillars of the adhesive pad are brought in contact with the ob- ject. This way the top surfaces of the pillars are displaced along the object in a direction inwards from the periphery towards the centre of the outer surface. This way the pillars are bent in a direction outwards towards the periphery of the outer surface and the inclined top surfaces of the pillars are contacting the object. During detachment the pillars are dragged along the object in the opposite direction, which causes a detachment of each one of said pillars from the object.

According to another embodiment of the invention each one of the pillars have a length of between 0.1 - 2000 μm, preferably 1 - 1000 μm, most preferred 100 - 500 μm. Pillars having lengths in the interval above show strong adhesion to all kinds of surfaces.

According to another embodiment of the invention each one of the pillars have a diameter of between 0.02 - 1000 μm, preferably 0.1 - 500 μm, most preferred 1 - 100 μm. Pillars having diameters in the interval above show strong adhesion to all kinds of surfaces.

According to another embodiment of the invention all the pillars have essentially the same length. By providing an adhesive pad having pillars with essentially the same length the adhesive pad adheres better to a smooth surface, such as a LCD panel.

According to another embodiment of the invention the pillars in a first group of the pillars have essentially the same length and the pillars of at least one other group of pillars have essentially the same length, the lengths of the pillars of the first group are different from the lengths of the pillars of the at least one other group of pillars. By providing an adhesive pad having pillars having two different lengths the adhesive pad adheres better to a rough surface. Further the invention relates to a method of fabricating an adhesive pad according to the invention, wherein the method comprising:

^■ providing a first mold, a second mold and a third mold, said first mold including a space that corresponds to the adhesive pad, said second mold including holes that correspond to pillars of said adhesive pad, said second mold further including V- shaped grooves, said third mold including V-shaped protrusions;

^■ attaching said second mold to said first mold;

^■ injecting liquid polymer into one or more of said holes of said second mold to fill said holes of said second mold and said space of said first mold with said liquid polymer;

^■ placing said third mold on said second mold such that said V-shaped protrusions are fitted into said V- shaped grooves of said second mold; and

^■ separating said first mold from said second mold to extract a solidified polymer structure in the form of said adhesive pad from said first, second and third molds.

Other advantages and advantageous features of the invention will appear from the other dependent claims and the subsequent description.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a specific description of embodiments of the invention cited as examples.

In the drawings: shows a very schematic planar view of an adhesive pad of the invention,

shows a very schematic cross-sectional view of an adhesive pad of the invention,

shows a very schematic planar of another adhesive pad of the invention,

shows a very schematic cross-sectional view of another adhesive pad of the invention,

shows very schematically in cross-section an adhesive pad of the invention attaching to a surface of an ob- ject,

shows very schematically in cross-section another adhesive pad of the invention attaching to a surface of an object,

shows very schematic cross-sectional view of an adhesive pad of the invention with a grid-like detachment member,

shows very schematically in cross-section an adhesive pad of the invention detaching from a surface of an object by means of a grid-like detachment member,

shows very schematically in cross-section another adhesive pad of the invention detaching from a surface of an object by means of detachment means, and

shows very schematically in cross-section yet another adhesive pad of the invention detaching from a sur- face of an object by means of detachment means. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Explained herein are preferred embodiments of the invention, describing the adhesive pad of the invention. The invention may, however, be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

In Fig 1 a very schematic planar view of an adhesive pad 1 1 of the invention is shown. The adhesive pad 1 1 comprises a plurality of flexible micro or nano pillars 12 arranged on its outer sur- face 13. Each one of said pillars 12 is arranged with one end attached to said outer surface 13 and the other end extending in a direction away from said outer surface 13. The essentially flat top surface of each one of said pillars 12 is inclined so that the normal to the top surface is directed away from a line being nor- mal to the outer surface and emanating from a centre point 13c on the outer surface 13. The arrows in Fig 1 show in which directions the normals to the top surfaces of the pillars 1 1 are directed.

In Fig 2 a very schematic cross-sectional view of an adhesive pad 21 of the invention is shown. The adhesive pad 21 in Fig 2 is similar to the adhesive pad in Fig 1 . The adhesive pad 21 comprises a plurality of flexible micro or nano pillars 22 arranged on its outer surface 23. Each one of said pillars 22 is ar- ranged with one end attached to said outer surface 23 and the other end extending in a direction away from said outer surface 23. The essentially flat top surface 27 of each one of said pillars 22 is inclined so that the normal to the top surface 27 is directed away from a line being normal to the outer surface and emanat- ing from a centre point 23c on the outer surface 23. In Fig 3 a very schematic planar view of an adhesive pad 31 of the invention is shown. The adhesive pad 31 comprises a plurality of flexible micro or nano pillars 32 arranged on its outer surface 33. Each one of said pillars 32 is arranged with one end attached to said outer surface 33 and the other end extending in a direction away from said outer surface 33. The essentially flat top surface 37 of each one of said pillars 32 is inclined so that the normal to the top surface 37 is directed towards a line being normal to the outer surface 33 and emanating from a centre point 33c on the outer surface 33. The arrows in Fig 1 show how the normals to the top surfaces of the pillars 32 are directed.

In Fig 4 a very schematic cross-sectional view of an adhesive pad 41 of the invention is shown. The adhesive pad 41 in Fig 4 is similar to the adhesive pad in Fig 3. The adhesive pad 41 comprises a plurality of flexible micro or nano pillars 42 arranged on its outer surface 43. Each one of said pillars 42 is arranged with one end attached to said outer surface 43 and the other end extending in a direction away from said outer surface 43. An essentially flat top surface 47 of each one of said pillars 41 is inclined so that the normal to the top surface 47 is directed towards a line being normal to the outer surface 43 and emanating from a centre point 43c on the outer surface 43.

Fig 5 shows very schematically in cross-section how an adhesive pad 51 of the invention attaches to a surface 56 of an object 55. Flexible pillars 52 of the pad 51 will bend so that the inclined top surfaces 57 of the pillars 52 will be in contact with the surface 56 of the object 55. Due to the fact that the top surfaces 57 of said pillars 52 are inclined so that the normals to the top surfaces 57 are directed away from a line being normal to the outer surface 53 and emanating from a centre point 53c on the outer surface 53, the van der Waals forces acting upon the pillars' top surfaces 57 from the surface 56 of the object 55 are all directed inwards towards the centre point 53c of the outer surface 53. This results in a steady state situation where all the forces acting on the object 55 from the pillars 52 of the adhesive pad 51 are directed outwardly towards the periphery 53p of the outer surface 53, thus keeping the pillars 52 in the bent position. If all inclined top surfaces of the pillars would be directed in the same direction, a steady state of bent pillars would not be obtained.

Fig 6 shows very schematically in cross-section how an adhesive pad 61 of the invention attaches to a surface 66 of an ob- ject 65. Flexible pillars 62 of the pad 61 will bend so that the inclined top surfaces 67 of the pillars 62 will be in contact with the surface 66 of the object 65. Due to the fact that the top surfaces 67 of said pillars 62 are inclined so that the normals to the top surfaces 67 are directed towards a line being normal to the outer surface 63 of the pad 61 and emanating from a centre point 63c on the outer surface 63, the van der Waals forces acting upon the pillars' top surfaces 67 from the surface 66 of the object 65 are all directed outwards towards the periphery 63p of the outer surface 63. This results in a steady state situation where all the forces acting on the object 65 from the pillars 62 of the adhesive pad 61 are directed inwards from said periphery 63p, thus keeping the pillars 62 in the bent position. If all inclined top surfaces of the pillars would be directed in the same direction, a steady state of bent pillars would not be obtained.

Fig 7 shows very schematically a cross-sectional view of an adhesive pad 71 of the invention with a grid-like detachment member 78. Here the pad 71 is illustrated as being a pad like that one shown in Fig 2, but the pad 71 can just as well be a pad like the pad shown in Fig 4. The grid-like detachment member 78 is arranged in parallel with the outer surface 73 of the pad 71 so that each hole in the member 78 surrounds at least one pillar 72, preferably only one pillar 72, said member 78 being movable in a direction perpendicular to said member 78 along the longitudinal direction of the pillars 72 towards their top surface 77 so as to detach the adhesive pad 71 from an object when the adhesive pad 71 is in use.

Fig 8 shows very schematically in cross-section how an adhe- sive pad 81 of the invention detaches from a surface 86 of an object 85 by means of a grid-like detachment member 88. During detachment of the adhesive pad 81 from the surface 86 of an object 85 the grid-like detachment member 88 is moved in a direction perpendicular to said member 88 along the longitudinal direction of the pillars 82 towards the pillars' 82 top surface 87. The member 88 straightens the pillars 82 and the top surfaces 87 detach from the surface 86 of the object 85. According to the invention, the grid-like detachment member can also be stretched and compressed in all directions parallel to the outer surface of the pad. By compressing the member inwards the centre of the outer surface the frictional forces from the surface of the object to the top surfaces of the pillars are counteracted, the above mentioned steady state is interrupted, whereby the adhesive pad detach from the object to which it is attached. An advantage with the grid-like detachment member 88 is that it during detachment of the adhesive pad 81 from the surface 86 of the object 85 also cleans the pillars 82 from particles and dirt by the movement of the member 88 along the longitudinal direction of the pillars 82 towards their top surface 87.

Fig 9 shows very schematically in cross-section how an adhesive pad 91 of the invention detaches from a surface 96 of an object 95. The adhesive pad 91 comprises detachment means configured to pull the centre point 93c of the outer surface 93 away from the object 95 to which the adhesive pad 91 is attached when it is in use, with respect to the periphery 93p of the outer surface 93. The periphery 93p of the outer surface 93 is thus folded towards an axis extending perpendicular outwards from the outer surface 93, like the folding of an umbrella. The detachment means can also be used in the opposite way when attaching the adhesive pad 91 to an object 95, by bringing the periphery 93p of the folded outer surface 93 in contact with the surface 96 of the object 95 to which it is to be attached. When the periphery 93p is in contact with the surface 96 of the object 95 the centre 93c of the outer surface 93 is pushed towards the object 95 by means of the detachment means, the outer surface 93 is unfolded and the pillars 92 of the adhesive pad 91 are brought in contact with the surface 96 of the object 95. This way the top surfaces 94 of the pillars 92 are dragged along the surface 96 of the object 95 in a direction outwards from the centre 93c towards the periphery 93p of the outer surface 93. The pillars 92 are bent in a direction inwards towards the centre 93c of the outer surface 93 and the inclined top surfaces 94 of the pillars are contacting the surface 96 of the object 95. During detachment the pillars 92 are dragged along the surface 96 of the object 95 in the opposite direction, which causes a detachment of each one of said pillars 92 from the object 95.

Fig 10 shows very schematically in cross-section how an adhesive pad 101 of the invention detaches from a surface 106 of an object 105. The adhesive pad 101 comprises detachment means configured to pull the periphery 103p of the outer surface 103 away from the object 105 to which the adhesive pad 101 is attached when it is in use, with respect to periphery 103p of the outer surface 103. The periphery 103p of the outer surface 103 is thus folded towards an axis extending perpendicular inwards from the centre 103c of the outer surface 103, like the folding of an umbrella. The detachment means can also be used in the opposite way when attaching the adhesive pad 101 to an object 105, by bringing the centre 103c of the folded outer surface 103 in contact with the surface 106 of the object 105 to which it is to be attached. When the centre 103c is in contact with the surface 106 of the object 105 the periphery 103p of the outer surface 103 is pushed towards the object 105 by means of the detachment means, the outer surface 103 is unfolded and the pillars 102 of the adhesive pad 101 are brought in contact with the surface 106 of the object 105. This way the top surfaces 104 of the pillars 102 are dragged along the surface 106 of the object 105 in a direction inwards from the periphery 103p towards the centre 103c of the outer surface 103. The pillars 102 are bent in a direction inwards towards the periphery 103p of the outer sur- face 103 and the inclined top surfaces 104 of the pillars are contacting the surface 106 of the object 105. During detachment the pillars 102 are dragged along the surface 106 of the object 105 in the opposite direction, which causes a detachment of each one of said pillars 102 from the object 105.

The detachment means described above can for instance be wires arranged in the adhesive pad and configured to actuate said adhesive pad in the above described folding. The detachment means can also be a piezoelectric material or an alloy whose shape can be affected by electricity or heat comprised in the adhesive pad.

The adhesive pad of the invention is of course not limited to having a circular shape, but can have any shape. The adhesive pad can comprise a plurality of pillar sets, wherein all of the pillars in each set are arranged according to the invention, i.e. the top surfaces of the pillars in each set of pillars are inclined with respect to a normal to the surface emanating from a centre point of each set of pillars on the outer surface of the adhesive pad.

The invention is of course not in any way limited to the embodiments described above. On the contrary, several possibilities to modifications thereof should be apparent to a person skilled in the art without departing from the scope of the invention as de- fined in the appended claims.

Claims

1 . An adhesive pad (1 1 , 21 , 51 , 71 , 91 ) comprising a plurality of flexible micro or nano pillars (12, 22, 52, 72, 92) arranged on its outer surface (13, 23, 53, 73, 93), wherein each one of said pillars:

^■ is arranged with one end attached to said outer surface and the other end extending in a direction away from said outer surface, and

^■ has an essentially flat top surface (27, 57, 77, 97) which is inclined so that the normal to said top surface deviates from the longitudinal direction of the pillar, characterized in that the top surface of each one of said pillars is inclined so that the normal to the top surface is directed away from a line being normal to the outer surface and emanating from a centre point (13c, 23c, 53c, 93c) on the outer surface.

2. An adhesive pad (1 1 , 21 , 71 ) according to claim 1 , characterized in that the adhesive pad comprises a grid-like detachment member (78) arranged in parallel with said outer surface (13, 23, 73) so that each hole in the member sur- rounds at least one pillar (12, 22, 72), preferably only one pillar, said member being movable in a direction perpendicular to the outer surface in the longitudinal direction of the pillars towards their top surface (27, 77) to detach the adhesive pad from an object to which the adhesive pad is attached when it is in use.

3. An adhesive pad (1 1 , 21 , 91 ) according to claim 1 , characterized in that the adhesive pad comprises detachment means configured to pull a centre point (13c, 23c, 53c, 93c) of the outer surface (13, 23, 93) away from an object (95) to which the adhesive pad is attached when it is in use.

4. An adhesive pad (1 1 , 21 , 51 , 71 , 91 ) according to any of the preceding claims, characterized in that the top surface (27, 57, 77, 97) is inclined with an angle within the range of 20°- 70°, preferably 30°-60°, most preferred 40°-50°, with respect to the longitudinal direction of the pillar (12, 22, 52, 72, 92).

5. An adhesive pad (1 1 , 21 , 51 , 71 , 91 ) according to any of the preceding claims, characterized in that the material of the pillars (12, 22, 52, 72, 92) comprises a polymer, preferably silicone.

6. An adhesive pad (31 , 41 , 61 , 81 , 101 ) comprising a plurality of flexible micro or nano pillars (32, 42, 62, 82, 102) ar- ranged on its outer surface (33, 43, 63, 83, 103), wherein each one of said pillars:

^■ is arranged with one end attached to said outer surface and the other end extending in a direction away from said outer surface, and ■ has an essentially flat top surface (47, 67, 87, 107), which is inclined so that the normal to said top surface deviates from the longitudinal direction of the pillar, characterized in that the top surface of each one of said pil- lars is inclined so that the normal to the top surface is directed towards a line being normal to the outer surface and emanating from a centre point (33c, 43c, 63c, 103c) on the outer surface.

7. An adhesive pad (31 , 41 , 61 , 81 ) according to claim 6, characterized in that the adhesive pad comprises a grid-like detachment member (88) arranged in parallel with said outer surface (33, 43, 63, 83) so that each hole in the member surrounds at least one pillar (32, 42, 62, 82), preferably only one pillar, said member being movable in a direction perpendicular to said member along the longitudinal direction of the pillars towards their top surface (47, 67, 87) to detach the adhesive pad from an object (65, 85) when the adhesive pad is in use by moving the member away from the outer surface towards the top surface of the pillars.

8. An adhesive pad (31, 41, 61, 101) according to claim 6, characterized in that the adhesive pad comprises detachment means configured to pull the periphery (63p, 103p) of the outer surface away from an object (65, 105) to which the adhesive pad is attached when it is in use.

9. An adhesive pad according to any of claims 6-8, characterized in that the top surface (47, 67, 87, 107) is inclined in an angle within the range of 20°-70°, preferably 30°-60°, most preferred 40°-50°, with respect to the longitudinal direction of the pillar (32, 42, 62, 82, 102).

10.An adhesive pad (31, 41, 61, 81, 101) according to any of claims 6 - 9, characterized in that the material of the pillars (32, 42, 62, 82) comprises a polymer, preferably silicone.

11.An adhesive pad (11, 21, 31, 41, 51, 61, 71, 81, 91, 101) according to any of the preceding claims, characterized in that each one of the pillars (12, 22, 32, 42, 52, 62, 72, 82, 92, 102) have a length of between 0.1 - 2000 μm, preferably 1 -

1000 μm, most preferred 100 - 500 μm.

12.An adhesive pad (11, 21, 31, 41, 51, 61, 71, 81, 91, 101) according to any of the preceding claims, characterized in that each one of the pillars (12, 22, 32, 42, 52, 62, 72, 82, 92) have a diameter of between 0.02 - 1000 μm, preferably 0.1 - 500 μm, most preferred 1 - 100 μm.

13.An adhesive pad (11, 21, 31, 41, 51, 61, 71, 81, 91, 101) ac- cording to any of the preceding claims, characterized in that all the pillars (12, 22, 32, 42, 52, 62, 72, 82, 92) have essentially the same length.

14.An adhesive pad (1 1 , 21 , 31 , 41 , 51 , 61 , 71 , 81 , 91 , 101 ) ac- cording to any of claims 1 - 12, characterized in that the pillars (12, 22, 32, 42, 52, 62, 72, 82, 92) in a first group of the pillars have essentially the same length and the pillars of at least one other group of pillars have essentially the same length, the lengths of the pillars of the first group being different from the lengths of the pillars of the at least one other group of pillars.

15. A method of fabricating an adhesive pad as defined in any of the claims 1 -14, characterized i n that the method compris- ing:

^■ providing a first mold, a second mold and a third mold, said first mold including a space that corresponds to the adhesive pad, said second mold including holes that correspond to pillars of said adhesive pad, said second mold further including

V-shaped grooves, said third mold including V- shaped protrusions;

^■ attaching said second mold to said first mold;

^■ placing said third mold on said second mold such that said V-shaped protrusions are fitted into said V-shaped grooves of said second mold; and