Abstract:
The present invention will provide adhesive technology adapted to adhere indefinitely to a surface without leaving a residue or sticky mess after removal. The self-preloading force provided by the electrostatic adhesion enables the present invention to be used in applications where directly applying a preload is not possible. Furthermore, the combination of electrostatic forces and Van der Waals forces allows electro-dry-adhesives to adhere to surfaces where traditional dry adhesives and electrostatic devices fail.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/772,599, filed on Mar. 5, 2013, and incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not Applicable. 
     FIELD OF THE INVENTION 
     This invention relates generally to dry and electrostatic adhesion, and more particularly, to a dry adhesion apparatus that is adapted to self-preload onto a target surface using electrostatic adhesion. 
     DISCUSSION OF RELATED ART 
     Generally, adhesion describes the attraction between two dissimilar surfaces or objects. 
     Wet adhesion can be described as adhering two objects through the use of a compound or substance, such as glue or paste. Electrostatic adhesion can be described as adhering two objects using electrical charges. Electrostatic adhesion typically incorporates electrodes having opposing polarity, from which the objects will be attracted to each other. Dry adhesion can be described as adhering two objects without the use of any liquid or surface tension, but rather, through van der Waal&#39;s forces. 
     Dry adhesives are inspired by the fibrillar structures found on geckos and some spiders which rely mainly on van der Waals; forces for adhesion. Dry adhesion is extremely unique, in that no composition or electrical requirements are necessary. One drawback of dry adhesives is that, in order to achieve optimal adhesion, often a relatively high preload is required. Generally, this is done by pushing the dry adhesive into the close contact necessary for van der Waals&#39; interactions to occur by hand or using a mechanical device or actuator. Similarly, dry adhesives are often peeled from a surface by hand or by a mechanical device or actuator. 
     While wet adhesion is the most common method of adhering two dissimilar surfaces together, there is a continued need for a device which can temporarily adhere two objects without leaving a sticky residue or requiring a constant power supply. Furthermore, there is a continued need for a device which can self-preload with respect to dry adhesion. The present invention satisfies these needs. 
     SUMMARY OF THE INVENTION 
     The present invention will provide a method and apparatus for adhering two dissimilar surfaces together without the need of a chemical composition, constant power, or initial preload. Furthermore, the present invention will not leave any residue behind, will easily attach and detach to a surface, and is adapted to self-clean if necessary. This is accomplished by combining the benefits of dry adhesion with those of electrostatic adhesion. 
     The present invention comprises a substrate material, a micro-featured and/or nano-scale featured surface, and conductive portion. These components work in conjunction to provide attractive or repulsive forces to permit a dry adhesive material to be self-preloaded, self-detached, or self-cleaned. More specifically, the generated electrostatic voltage produces an electrostatic field and either electrostatic adhesion forces or electrostatic repulsion forces depending on the polarity of the electrodes and the frequency with which it is applied. 
     When the present invention is placed near the surface of an object, the electrostatic forces either attract or repel an object based on the polarity of the objects intrinsic charge or the objects ability to reorganize surface charges into a dipole or charge regions that are either positively or negatively charged. Like charges generate repelling forces and opposing electrical charges generate attractive forces that are used by the present invention to either self-preload (attractive force), self-detach (repelling force), or self-clean (alternating attractive and repelling force). Electric control of the present invention can easily be switched on during self-preloading, self-detaching, or self-cleaning operations, but can be switched off to enable the present invention to operate in a low-power state using van der Waals and similar natural attraction forces. 
     These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments. It is to be understood that the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of the present invention; 
         FIG. 2  is a cross-sectional view of the present invention with insulating layer; 
         FIG. 3  is a cross-sectional view of the present invention configured for self-cleaning; 
         FIG. 4  is a cross-sectional view of the present invention configured for self-cleaning with insulating layer; 
         FIG. 5  is a schematic view of the fabrication process of the present invention; 
         FIG. 6  is a scanning electron microscope image of one embodiment of the present invention; 
         FIG. 7  is a scanning electron microscope image of an alternative embodiment of the present invention; 
         FIG. 8  is a graph illustrating an increase in conductivity as the percentage by weight of carbon black is added; 
         FIG. 9  is a cross-sectional view of the present invention illustrating micro-scale features; 
         FIG. 10  is a cross-sectional view of the present invention illustrating micro-scale features with carbon black particles; 
         FIG. 11  is a cross-sectional view of the present invention illustrating micro-scale features with carbon black particles and a conducting electrode layer; 
         FIG. 12  is a cross-sectional view of the present invention illustrating micro-scale features with a conducting electrode layer; 
         FIG. 13  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles; 
         FIG. 14  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles; 
         FIG. 15  is a cross-sectional view of the present invention illustrating micro-scale features with carbon black particles separated by a non-conducting material; 
         FIG. 16  is a cross-sectional view of the present invention illustrating micro-scale features with carbon black particles and a conducting electrode layer separated by a non-conducting material; 
         FIG. 17  is a cross-sectional view of the present invention illustrating micro-scale features with a separated conducting electrode layer; 
         FIG. 18  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles and a conducting electrode layer separated by a non-conducting material; 
         FIG. 19  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles and a conducting electrode layer separated by a non-conducting material; 
         FIG. 20  is a cross-sectional view of the present invention illustrating micro-scale features without carbon black particles; 
         FIG. 21  is a cross-sectional view of the present invention illustrating micro-scale features without carbon black particles, wherein the carbon black particles are separated; 
         FIG. 22  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles in the nano-scale features; 
         FIG. 23  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles in the nano-scale features; 
         FIG. 24  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles in the nano-scale features; 
         FIG. 25  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles in the micro-scale posts; 
         FIG. 26  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles in the micro-scale and not in the nano-scale features; 
         FIG. 27  is a cross-sectional view of the present invention illustrating micro-scale and nano-scale features with carbon black particles in the micro-scale posts and not in the nano-scale features; 
         FIG. 28  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 29  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 30  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 31  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 32  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 33  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 34  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 35  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 36  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 37  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 38  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 39  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 40  is a cross-sectional view of the present invention illustrating an alternative embodiment of the present invention; 
         FIG. 41  is a top view of the present invention illustrating a cap and post arrangement; 
         FIG. 42  illustrates a first electrode arrangement of the present invention; 
         FIG. 43  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 44  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 45  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 46  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 47  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 48  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 49  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 50  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 51  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 52  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 53  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 54  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 55  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 56  illustrates an alternative electrode arrangement of the present invention according to an alternative embodiment; 
         FIG. 57  is a cross-sectional view of the present invention illustrating an outward radial embodiment; 
         FIG. 58  is a cross-sectional view of the present invention illustrating an outward square embodiment; 
         FIG. 59  is a cross-sectional view of the present invention illustrating an inward square embodiment; 
         FIG. 60  is a cross-sectional view of the present invention illustrating the electrostatic preloading force. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Illustrative embodiments of the invention are described below. The following explanation provides specific details for a thorough understanding of and enabling description for these embodiments. One skilled in the art will understand that the invention may be practiced without such details. In other instances, well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. 
     Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words “herein,” “above,” “below” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. When the claims use the word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list. 
     In the preferred embodiment, the present invention comprises a micro-structured and/or nano-structured surface further comprising a deformable material  6 , in general, a conductive polymer, rubber or silicone rubber or a composite polymer, rubber, or silicone rubber material with embedded conductive particles  21  such as carbon black, carbon nanotubes, silver particles, or other conductive materials, and one electrode. The electrode may be composed of an electrically conductive metallic material or an electrically conductive polymer, rubber, or silicone rubber. Alternatively the electrode may be composed of a composite polymer, rubber, or silicon rubber with embedded conductive particles  21  such as carbon black, carbon nanotubes, silver particles, or other conductive materials which enable a current or electric charge to pass through the polymer, rubber, or silicon rubber material. 
     A voltage of at least about 500V is applied to the electrode which generates an electrostatic field attracting to or repulsing the electro-dry-adhesive from the surface to which is attached. Preloading of the present invention occurs when the electrostatic field is attractive. Reduced dry adhesion occurs when the electrostatic field is repulsive. After preloading occurs, the voltage may remain active to provide enhanced adhesion, or the voltage may be disabled to conserve power while the present invention relies on van der Waals&#39; forces for continued adhesion. Self-peeling or reduced adhesion aiding peeling occurs while a repelling electrostatic field is present. The applied voltage may be either constant or varying. 
     In an alternative embodiment, the present invention comprises the micro-structured and/or nano-structured surface and deformable material  6  of the preferred embodiment, and further comprises a plurality of electrodes. The electrodes may be composed of an electrically conductive metallic material or an electrically conductive polymer, rubber, or silicone rubber. Alternatively the electrodes may be composed of a composite polymer, rubber, or silicon rubber with embedded conductive particles such as carbon black, carbon nanotubes, silver particles, or other conductive materials which enable a current or electric charge to pass through the polymer, rubber or silicon rubber material. The plurality of electrodes are separated by a sufficient distance to prevent leakage currents or arcing between the electrodes and the gap between electrodes may be composed of air or a gas, liquid, or solid material. 
     Again, a voltage of at least about 500V is applied across the electrodes in such a manner that the voltage difference between electrodes is at least about 500V, which generates an electrostatic field attracting to or repulsing the electro-dry-adhesive from the surface to which it is attached. Preloading of the dry adhesive structures occurs when the electrostatic field is attractive. Reduced dry adhesion occurs when the electrostatic field is repulsive. After preloading occurs, the voltage may remain active to provide enhanced adhesion or the voltage may be disabled to conserve power while present invention relies on van der Waals&#39; forces for continued adhesion. Self-peeling or reduced adhesion aiding peeling occurs while a repelling electrostatic field is present. The applied voltage may be either constant or varying. 
     The present invention may be further adapted for self-cleaning Here, a voltage of at least about 500V is applied across the electrode or electrodes in such a manner that the voltage difference between electrodes is at least about 500V, which generates an electrostatic field attracting or repulsing any dirt, grease or fluids on the micro-structured and/or nano-structured surface of the present invention depending on the surface charge of the dirt, grease or fluid. The applied voltage may be of constant or varying amplitude and/or frequency and may be applied in such a manner as to direct any dust, grease or fluid towards the extremities of the present invention. 
     The present invention is manufactured such that the components work in conjunction to provide adequate dry and electrostatic adhesion. The method of manufacturing the present invention comprises first applying one or more layers of photoresistive material to a poly(methyl methacrylate) mold substrate, glass, silicon, or other suitable mold substrate. Next, the photoresistive material is patterned and developed to form a structured array of holes or posts which form the structure of the mold. Multiple layers of photoresists may be used to create holes with layers of varying diameter. A conductive silicone rubber material, conductive flexible polymer material, silicone rubber material containing conductive particles, or a flexible polymer containing conductive particles is positioned within the mold to form the electro-dry-adhesive electrodes. Next, a conductive silicone rubber material, conductive flexible polymer material, silicone rubber material containing conductive particles, or a flexible polymer containing conductive particles or other conductive material such as aluminum may be attached or incorporated into the electro-dry-adhesive as an electrical contact. 
     In an alternative method of manufacture, the non-conductive silicone rubber material or flexible polymer material is used to form the structured surface of the present invention. Here, a layer of conductive material such as gold, chromium, aluminum, conductive silicone rubber material, conductive flexible polymer material, silicone rubber material containing conductive particles, or a flexible polymer containing conductive particles is applied as an electrode layer to the unstructured side of the electro-dry-adhesive device. In a further alternative embodiment, a second layer of non-conducting material may be applied to the previously applied conducting layer to act as an insulating layer. 
       FIG. 1  illustrates the concept of electrostatic forces where the positive  1  and negative  2  electrodes are separated by an insulating material  3 . When an electric potential is applied across the electrodes, a positive  4  or negative  5  charge, opposite to that on the nearest positive  1  or negative  2  electrode, is formed on the surface of the substrate material  6  the electro-dry-adhesives are being attached to. The positive  4  and negative  5  charged regions of the substrate  6  are attracted to the positive  1  or negative  2  charged electrodes and the generated electrostatic forces draw the charged electrodes and the substrate material together as indicated by the arrows  7 . In this case, the positive  1  and negative  2  electrodes should be a conductive material to form the electrodes. The insulating material  3  could be air if sufficient space between the electrodes is maintained or a solid with an appropriate dielectric constant. The substrate material  6  in this case should be an insulating material. The substrate material  6  and the electro-dry-adhesive are separated by an air or liquid interface  8 . 
       FIG. 2  illustrates an alternative embodiment where the positive  1  and negative  2  electrodes are separated from each other by an insulating material  3  and an insulating layer  9  is directly attached to the electrodes and separates the positive  1  and negative  2  electrodes from the substrate material  6  the electro-dry-adhesives are being attached to. When an electric potential is applied across the positive  1  and negative  2  electrodes, a positive  4  or negative  5  charge, opposite to that on the nearest positive  1  or negative  2  electrode, is formed on the surface of the substrate material  6 . The positive  4  and negative  5  charged regions of the substrate material  6  are attracted to the oppositely charged positive  1  and negative  2  electrodes and the generated electrostatic forces draw the charged electrodes and the substrate material together as indicated by the arrows  7 . In this case, the positive  1  and negative  2  electrodes should be a conductive material to allow current to flow. The insulating material  3  should be in general an insulating material with high dielectric constant but could simply be air if sufficient space between the electrodes is maintained. The layer of material  9  separating the positive  1  and negative  2  electrodes from the substrate  6  in this case should be an insulating material. 
     The substrate material  6  can be either a nonconductive or a conductive material. When the substrate material  6  is a conductive material, the generated electrostatic force may be greater. The substrate material  6  and the present invention are separated by an air or liquid interface  8 . 
       FIG. 3  illustrates the present invention configured for self-cleaning Positive  1  and negative  2  electrodes are separated by an insulating material  3 . When a voltage is applied across the positive  1  and negative  2  electrodes positively  10  and negatively  11  charged electrodes dust, dirt, grease or fluids are repelled from the like-charged positive  1  and negative  2  electrodes and attracted towards the oppositely charged negative  2  and positive  1  electrodes respectively. The polarity of the positive  1  and negative  2  electrodes is reversed or applied in such a manner that the dust, dirt, grease or fluids are directed towards the edge of the present invention. The voltage applied to the positive  1  and negative  2  electrodes may be of constant or alternating polarity. 
       FIG. 4  shows the present invention configured for self-cleaning Positive  1  and negative  2  electrodes are separated by an insulating material  3 . A layer of insulating material  9  separates the electrodes from the dirt particles. When a voltage is applied across the positive  1  and negative  2  electrodes positively  10  and negatively  11  charged electrodes dust, dirt, grease or fluids are repelled form the like-charged positive  1  and negative  2  electrodes and attracted towards the oppositely charged negative  2  and positive  1  electrodes respectively. The polarity of the positive  1  and negative  2  electrodes is reversed or applied in such a manner that the dust, dirt, grease or fluids are directed towards the edge of the present invention. The voltage applied to the positive  1  and negative  2  electrodes may be constant or alternating polarity. 
       FIG. 5  illustrates a schematic view of one fabrication process of the present invention. First, a Polymethyl Methacrylate (PMMA) wafer  12  is coated with first a layer of polydimethylglutarimide (PMGI)  13  and then a layer of AZ 9260 photoresist  14 . Next, the PMGI  13  and AZ9260  14  photoresist is exposed to suitable UV light and developed in a suitable developing solution to create a mold cavity for the desired surface features  15  which may in this case include a post  16  and overhanging mushroom-like cap  17 . Next, uncured Poly(Dimethyl Siloxane) (PDMS)  18  is mixed and cast on the mold in order to replicate the surface features. Lastly, the PDMS  18  is cured and then demolded from the mold with the desired features  15  such as a post  16  and overhanging cap  17 . Conducting electrodes  19  are adhered to the unstructured surface of the PDMS to finalize the present invention. 
       FIGS. 6 and 7  are scanning electron microscope (SEM) images of alternative embodiments of the present invention showing the posts  16  and overhanging mushroom-like caps  17 .  FIG. 8  indicates the increase in conductivity of the PDMS as an increasingly larger percentage by weight of carbon black is added to the PDMS 
       FIG. 9  illustrates an embodiment of the present invention where a non-conductive polymer or silicone rubber material  20  is used to define the micro-scale surface features  15  of the present invention which include a supporting post  16  and overhanging cap  17 . 
       FIG. 10  illustrates an embodiment of the present invention where conductive carbon black particles  21  have been added to the polymer or silicone rubber  20  which is used to define the micro-scale surface features  15  of the present invention which include a supporting post  16  and overhanging cap  17 . 
       FIG. 11  illustrates yet another embodiment of the cross-section of the present invention where a conductive material or a polymer or silicon rubber which contains a sufficient number of conductive particles  21  and defines the micro-scale surface features  15  of the present invention which include a supporting post  16  and overhanging cap  17 . A conducting electrode layer  22  is used to enhance the electrical contact between the polymer or silicone rubber material  21  and the power source. 
       FIG. 12  illustrates yet another embodiment of the cross-section of the present invention where a layer of non-conducting material  23  or silicon rubber or polymer defines the micro-scale surface features  15  which include a supporting post  16  and an overhanging cap  17 . A layer of conducting material  22  is used to define the electrodes and is attached directly to the non-conducting material  23 . 
       FIG. 13  illustrates yet another embodiment of the cross-section of the present invention where a conductive material or a polymer or silicon rubber which contains a sufficient number of conductive particles  21  and defines the micro-scale surface features  15  of the present invention which include a supporting post  16  and overhanging cap  17 . A nano-scale layer of the dry adhesive structure  24  cover the overhanging cap  17  of the micro-scale. The conducting polymer or silicone rubber material  21  defines both micro-scale and nano-scale surface features of the present invention. 
       FIG. 14  illustrates yet another embodiment of the cross-section of the present invention where a conductive material or a polymer or silicon rubber which contains a sufficient number of conductive particles  21  and defines the micro-scale surface features  15  of the present invention which include a supporting post  16  and overhanging cap  17 . A nano-scale layer of dry adhesive structures  24  with overhanging caps  25  cover the overhanging cap  17  of the micros-scale. The conducting polymer or silicone rubber material  21  defines both micro-scale and nano-scale surface features of the present invention. 
       FIG. 15  illustrates yet another embodiment of the cross-section of the present invention where a conducting material or a polymer, silicon rubber or plastic material  21  in which conductive particles have been added to increase the conductivity of the material defines the surface features  15  of the present invention which includes a supporting post  16  and overhanging cap  17 . Areas made with a conducting material or a polymer, silicon rubber or plastic material  21  are separated by a non-conducting silicon rubber, polymer or plastic material  23  and operate to isolate the regions made from a conducting material or a polymer, silicon rubber or plastic material  21  from each other. 
       FIG. 16  indicates yet another embodiment of the cross-section of the present invention where 3 different materials have been used to fabricate the device. In this case, a conductive polymer, silicone rubber or plastic or a polymer, silicone rubber or plastic material that has been made conductive by the addition of an appropriate amount of conductive particles  21  defines the micro-scale features  15  composed of a supporting post  16  and an overhanging cap  17 . A conductive material  22  improves conductivity or electrical contact to the conductive polymer, silicone rubber or plastic material  21 . A third nonconductive layer of material  23  such as silicone rubber, polymer or plastic is used to electrically isolate conductive regions on the present invention. 
       FIG. 17  indicates yet another embodiment of the cross-section of the present invention where 2 materials have been used to fabricate the device. A nonconductive polymer, silicone rubber or plastic material  23  defines the micro-scale features  15  which include a supporting post  16  and overhanging cap  17 . A conductive material  22  such as silicone rubber, polymer or plastic or a polymer, silicone rubber or plastic material that has been made conductive by the addition of an appropriate amount of conductive particles or a metal layer defines the electrical electrodes of the present invention. 
       FIG. 18  illustrates yet another embodiment of the cross-section of the present invention where a hierarchy of micro-scale  15  and nano-scale  24  structures is used to enhance adhesion. A conducting polymer or silicone rubber material  21  defines the micros-scale features  15  which includes a supporting post  16  and overhanging cap  17  as well as the nano-scale features  24  of the present invention. The conducting polymer or silicone rubber material  21  are separated by a silicone rubber, polymer or plastic material  23  which is non-conducting and operates as an insulating region between the conducting regions of the present invention. 
       FIG. 19  illustrates yet another embodiment of the cross-section of the present invention where a hierarchy of micro-scale  15  and nano-scale  24  structures is used to enhance adhesion. A conducting polymer or silicone rubber material  21  defines the micros-scale features  15  which includes a supporting post  16  and overhanging cap  17  as well as the nano-scale features  24  with overhanging caps  25  of the present invention. The conducting polymer or silicone rubber material  21  are separated by a silicone rubber, polymer or plastic material  23  which is non-conducting and act as an insulating region between the conducting regions of the present invention. 
       FIG. 20  illustrates yet another embodiment of the cross-section of the present invention where the surface features  15  with supporting post  16  and overhanging cap  17  are made from non-conducting silicon rubber, polymer or plastic  23  and the backing layer is made from a layer of conducting silicone rubber, polymer or plastic material  21 .  FIG. 21  illustrates yet another embodiment of the cross-section of the present invention where a structured interlacing electrode pattern has been defined using conductive polymers, silicon rubber or plastic  21 . The micro-structures  15  on the surface of the present invention have a supporting post  16  and overhanging cap  17  which is formed from non-conducting silicon rubber, polymer or plastic material  23 . 
       FIG. 22  illustrates yet another embodiment of the cross-section of the present invention where the micro-scale surface features  15  with supporting post  16  and overhanging cap  17  are fabricated from non-conducting silicon rubber, polymer or plastic material  23  and the nano-scale features  24  are made from conducting material  21 . 
       FIG. 23  illustrates yet another embodiment of the cross-section of the present invention where the present invention micro-scale  15  and nano-scale  24  features are made of either a conducting  21  or non-conducting  23  polymer or silicone rubber material. The non-conducting polymer or silicone rubber material  23  defines the backing layer and micro-scale post  16 . The overhanging cap  17  of the micros-scale features  15  and nano-scale features  24  are made from a conducting polymer or silicone rubber material  21 . 
       FIG. 24  illustrates yet another embodiment of the cross-section of the present invention where the present invention micro-scale  15  and nano-scale  24  features are made of either a conducting  21  or non-conducting  23  polymer or silicone rubber material. The non-conducting polymer or silicone rubber material  23  defines the supporting post  16  of the micros-scale features  15  and the nano-scale features  24 . A conducting polymer or silicone rubber material  21  defines the micro-scale overhanging cap  17 . 
       FIG. 25  illustrates yet another embodiment of the cross-section of the present invention where the present invention micro-scale  15  and nano-scale  24  features are made of either a conducting  21  or non-conducting  23  polymer or silicone rubber material. The non-conducting polymer or silicone rubber material  23  defines the backing layer, overhanging cap  17  of the micros-scale features  15  and the nano-scale features  24 . A conducting polymer or silicone rubber material  21  defines the micro-scale supporting post  16   
       FIG. 26  illustrates yet another embodiment of the cross-section of the present invention where the present invention micro-scale  15  and nano-scale  24  features are made of either a conducting  21  or non-conducting  23  polymer or silicone rubber material. The non-conducting polymer or silicone rubber material  23  defines the nano-scale features  24  and the backing material. A conducting polymer or silicone rubber material  21  defines the micro-scale supporting post  16  and overhanging cap  17  of the micros-scale features  15 . 
       FIG. 27  illustrates yet another embodiment of the cross-section of the present invention where the present invention micro-scale  15  and nano-scale  24  features are made of either a conducting  21  or non-conducting  23  polymer or silicone rubber material. The non-conducting polymer or silicone rubber material  23  defines the overhanging cap  17  of the micro-scale features  15  and the nano-scale features  24 . A conducting polymer or silicone rubber material  21  defines the micro-scale supporting post  16  and of the micros-scale features  15  and the backing layer. 
       FIG. 28  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the structures shown with the micro-scale structures  15  composed of a triangular cross-sectioned supporting post  16  and an overhanging cap  17 . The angle of the caps with respect to the micro- or nano-scale supporting structure may be at any angle or combination of angles to the supporting structure as defined by a. 
       FIG. 29  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to fabricate the cross-section of the structures shown with the micro-scale structures  15  composed of a triangular cross-sectioned supporting post  16 . 
       FIG. 30  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions, combinations or device configurations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structures. The angle of the overhanging cap  17 , which is triangular in cross section, with respect to the micro-scale  15  or nano-scale supporting post  16  may be at any angle with respect to the supporting post  16  as defined by a. Similarly the angle, shown by θ, of the supporting post  16  with respect to the backing layer may be at any angle or combination of angles from 0 to 180 degrees. 
       FIG. 31  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions, combinations or device configurations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structures. The angle of the supporting post  16  with respect to the backing layer as given by θ, may be at any angle or combination of angles from 0 to 180 degrees. The overhanging cap  17  in this case is composted of spherical structures, with radis r. 
       FIG. 32  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. The angle of the overhanging caps  17  with respect to the micro- or nano-scale supporting post  16  may be at any angle with respect to the supporting structure as defined by a. Similarly the angle, shown by θ, of the supporting post  16  to the backing layer may be at any angle or combination of angles from 0 to 180 degrees. 
       FIG. 33  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. The angle of the overhanging caps  17  with respect to the micro- or nano-scale supporting post  16  may be at any angle with respect to the supporting post  16  as defined by a. Similarly the angle, shown by θ, of the supporting post  16  to the backing layer may be at any angle or combination of angles from 0 to 180 degrees. 
       FIG. 34  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. The angle of the overhanging caps  17  with respect to the micro- or nano-scale supporting posts  16  may be at any angle with respect to the supporting structure as defined by α. Similarly the angle, shown by θ, of the supporting post  16  to the backing layer may be at any angle or combination of angles from 0 to 180 degrees. 
       FIG. 35  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. The angles, shown by θ and Φ, of the supporting posts  16  with respect to the backing layer may be at any angle or combination of angles from 0 to 180 degrees. 
       FIG. 36  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. The angles, shown by θ and Φ, of the supporting posts  16  with respect to the backing layer may be at any angle or combination of angles from 0 to 180 degrees. Similarly, the angles, α and β, of the overhanging caps  17  with respect to the supporting posts  16  may be at any angle or combination of angles from 0 to 180 degrees. 
       FIG. 37  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions, combinations or device configurations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. The angles, shown by θ and Φ, of the supporting posts  16  with respect to the backing layer may be at any angle or combination of angles from 0 to 180 degrees. In this embodiment, the overhanging cap  17  is formed of spherical structures, with radius r. 
       FIG. 38  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. The angle of the supporting post  16 , shown by θ, of the supporting post  16  with respect to backing layer may be at any angle or combination of angles from 0 to 180 degrees. 
       FIG. 39  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. In this case the supporting posts  16  are triangular in cross-section and the micro-scale or nano-scale overhanging caps  17  are circular in cross-section with radius r. 
       FIG. 40  illustrates yet another embodiment of the cross-section of the present invention where any of the material compositions or combinations shown in  FIG. 9 through 27  may be used to form the cross-section of the micro-scale  15  or nano-scale structure. In this case the supporting posts  16  are triangular in cross-section and the angle of the overhanging caps  17  with respect to the micro- or nano-scale supporting post  16  may be at any angle or combination of angles to the supporting post  16  as defined by a. 
       FIG. 41  illustrates an end-on view of the overhanging cap  17  and the relative placement of the supporting post  16  in common configurations of the present invention nano-scale or micro-scale structures shown previously in cross-sectional view in  FIGS. 9 through 40 . 
       FIG. 42  illustrates one possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 42 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 43  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 43 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 44  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 44 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 45  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 45 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 46  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 46 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 47  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 47 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 48  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 48 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 49  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 49 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 50  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions preciously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 50 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 51  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 51 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 52  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 52 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 53  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 53 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 54  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 54 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 55  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 55 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 56  illustrates yet another possible configuration of the positive  26  and negative  27  electrodes for any of the present inventions previously shown in  FIG. 9 through 40 . While one possible electrode configuration is shown in  FIG. 56 , the positive  26  and negative  27  electrodes are interchangeable. 
       FIG. 57  illustrates another embodiment of the present invention where instead of using a planar sheet of electro-dry-adhesive, the present invention is formed into a circular cross-section with outer radius, R, and inner radius, r, where 0≦r≦R and where R is greater than 1 mm. The present invention with micro- or nano-scale structures  15  composed of supporting posts  16  and overhanging caps  17 , although only shown in one cross-sectional configuration, can be implemented in any of the configurations previously illustrated in  FIGS. 9 through 40 . 
       FIG. 58  illustrates yet another embodiment of the present invention where instead of using a planar sheet of electro-dry-adhesive, the present invention is formed in a square (shown) or polygonal cross-section with outer dimensions A and B being greater than 1 mm and side wall thicknesses, C and D ranging from 1 μm to one half of the length of B. Side wall thicknesses, E and F, range from as small as 1 μm to one half of the length of A. The present invention with micro- or nano-scale structures  15  composed of supporting posts  16  and overhanging caps  17 , although only shown in one cross-sectional configuration, can be implemented in any of the configurations or materials combinations previously illustrated in  FIGS. 9 through 40 . 
       FIG. 59  illustrates yet another embodiment of the present invention where instead of using a planar sheet of electro-dry-adhesive, the present invention is formed in a square or tubular cross-section with outer dimensions A and B being greater than 1 mm. The wall thicknesses, C and D, may range from 1 μm to one half of the length of B. Side wall thicknesses, E and F, range from as small as 1 μm to one half of the length of A. The present invention with micro- or nano-scale structures  15  composed of supporting posts  16  and overhanging caps  17 , although only shown in one cross-sectional configuration, can be implemented in any of the configurations or materials combinations previously illustrated in  FIGS. 9 through 40 . 
       FIG. 60  illustrates a compliant electro-dry-adhesive sheet  20  in cross-section self-complying to a macro-scale round substrate  6  also shown only in cross-section. A. The present invention  20  is placed near the surface of the round substrate  6 . B. After applying a voltage to the electrodes on the present invention  20  the generated attractive electrostatic force between the present invention  20  and the round substrate  6  is such that the compliant electro-dry-adhesive  20  is bent towards the surface of the round object. As the present invention  20  continues to be bent into compliant contact with the round substrate  6  as shown in C, the compliant electro-dry-adhesive sheet  20  is in conformal contact with the macro-scale round object as shown in D. For clarity, the micro- and nano-scale structures are not shown and a relatively large gap is shown between the macro-scale round substrate  6  and the present invention  2 . In reality, the electrostatic force is such that it self-preloads the present invention micro-scale structures into the close contact required for van der Waals interactions to occur. 
     In the preferred embodiment of the present invention, a 4″ diameter polymethyl methacrylate (PMMA) substrate is first rinsed under de-ionized (DI) water. After first drying with compressed N 2  gas, the PMMA is placed in a thermal chamber at 100° C. for 1 minute to thoroughly dry the PMMA surface. Polymethylglutarimide (PMGI  19 , MicroChem) is thinned 3:1 by weight with T-Thinner and is spin-coated onto the PMMA substrate at 2500 RPM for 30 seconds to obtain a 2.3 μm thick layer. Following a 100° C. soft bake for 2 minutes in a thermal chamber, a second photoresist layer (AZ9260 is spin coated at 3000 RPM for 30 seconds. Following a 1 hour bake at 80° C., the PMMA substrate with photoresist layers is subjected to 100° C. for 90 seconds within a thermal chamber. After allowing the photoresist layers to re-hydrate for 30 minutes in DI water, the photoresist layers are exposed to i-line UV light for a suitable period of time with a suitable mask defining the desired features. After UV exposure the PMMA substrate and photoresist layers are placed in developer solution (AZ 400K 1:4 DI water) in order to develop the micro-scale features. After the desired structure has been achieved, the photoresist and PMMA substrate are immediately rinsed with DI water and allowed to air dry for at least 1 hour prior to being used as a mold substrate. 
     PDMS is first mixed in a 10:1 ratio of prepolymer to curing agent and then 24% carbon black particles by weight are carefully mixed into the PDMS. After thoroughly mixing the PDMS and carbon black mixture (CB-PDMS), the CB-PDMS is spread over the surface of a prefabricated mold which defines the desired surface. After achieving the desired backing layer thickness, aluminum strips are placed on the CB-PDMS and then the mold, CB-PDMS and aluminum are placed in a thermal chamber and cured at 80° C. for 3 hours to cure the CB-PDMS. After the CB-PDMS has cured, it is removed from the mold and the present invention is ready for use. The manufacturing process is illustrated in  FIG. 5 . 
     The above method can be modified accordingly to further satisfy individual requirements. First, an increased percentage of carbon black by weight results in CB-PDMS with increased conductivity. It may be necessary to use a PDMS thinner such as Toluene or Hexane in order to achieve thorough mixing with CB concentrations greater than 25%. Alternating layers of CB-PDMS and PDMS may be used to suitably create alternating conductive and non-conductive layers. It may be desirable to spin coat a thin layer of PDMS onto the mold substrate before applying a layer of CB-PDMS in order to ensure that the microstructures are composed of only PDMS. The PDMS layer may be cured prior to the application of the CB-PDMS layer. Also, a metallic layer may be used to increase conductivity. Lastly, the metallic layer may be used to define the electrodes. 
     While the above description contains specific details regarding certain elements, sizes, and other teaching, it is understood that embodiments of the invention or any combination of them may be practiced without these specific details. Specifically, although certain materials are designated in the above embodiments, any suitable materials may be used. These details should not be construed as limitations on the scope of any embodiment, but merely as exemplifications of the presently preferred embodiments. In other instances, well known structures, elements, and techniques have not been shown to clearly explain the details of the invention. 
     The above detailed description of the embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above or to the particular field of usage mentioned in this disclosure. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. Also, the teachings of the invention provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments. 
     Changes can be made to the invention in light of the above “Detailed Description.” While the above description details certain embodiments of the invention and describes the best mode contemplated, no matter how detailed the above appears in text, the invention can be practiced in many ways. Therefore, implementation details may vary considerably while still being encompassed by the invention disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the invention should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the invention with which that terminology is associated. 
     While certain aspects of the invention are presented below in certain claim forms, the inventor contemplates the various aspects of the invention in any number of claim forms. Accordingly, the inventor reserves the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the invention.