Microstructured device for generating electroadhesion

Abstract

A microstructured device (200) is disclosed that utilizes coulombic field modification of surface energy and electro-adhesion to position or levitate a device surface relative to a target surface. The surface energy modification can be permanent or reversible depending on whether the charge is externally delivered to the device or electrochemically derived on the device. The microstructured aspect of the device induces various hydrophilic / hydrophobic interactions with the target surface. The coulombic field can be used to enhance or diminish the hydrophilic / hydrophobic interactions. In combination, the disclosed electro-microstructured device is provided for positioning an implant within a mammalian body, and additionally provides a means for controlling cell interactions with the implant.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to microstructured devices with an electrical management system that can change the state of the physical properties of the microstructured device. The present disclosure also relates to microstructured surfaces that interact with target surfaces through electro-adhesion and electrowetting by changing the surface energy of the disclosed microstructured surfaces. Further, electro-adhesive microstructured surfaces are disclosed herein, such as both implantable surfaces and general grip-enhancing surfaces. BACKGROUND

[0002] It is known in the art that surfaces can undergo a change in surface wetting properties through an applied electric field, which is known as electrowetting. Electrowetting can be understood based on the forces that result from an applied electric field. Typically, electrowetting is used with hydrophobic surfaces. Typically, when placed on a hydrophobic surface, water will approximate a sphere because the attraction between water molecules counteracts the force of gravity that tends to flatten the water on the surface. In contrast, non-polar liquids have little self-attraction and thus non-polar liquids can spread on a hydrophobic surface under the action of gravity. By contrast, when water is placed on a hydrophilic surface, the tendency of water to form a sphere by its own attraction is counteracted by the attraction of the water to the hydrophilic surface, so gravity dominates and the water droplet will spread. When a non-polar liquid is placed on a hydrophilic surface, one might expect gravity to dominate, but in some cases surface tension dominates and the non-polar liquid will typically form a spherical structure on the hydrophobic surface.

[0003] Recently, it has been discovered that exogenous electric fields can be used to modulate cell function, such as cell migration in wound healing processes. Therapeutic devices and wound dressings that exploit the effects of static or dynamic electric fields are increasing, particularly in bone repair. These devices use large electrodes and macroscopically uniform electromagnetic fields.

[0004] However, the disclosure provided in this specification relates to field strengths of the order of 100 kV / m fields. If such fields are placed on large electrodes with macroscopic separation, typically this field strength is sufficient for large scale electroporation and electrofusion of tissues. In contrast, because the fields that are generated are on the micron scale, they do not cause electroporation and electrofusion of tissues, as described in more detail below. Thus, a high field gradient does not equate to a high energy density on the microscale.

[0005] Those who conduct experiments in electro-adhesion understand that the actual force generated is far less than the theoretically calculated force. The reason for this deviation from theory is that no real material is a perfectly homogeneous dielectric. When the inhomogeneities are random, the inhomogeneities inhibit electro-adhesion. On the other hand, inhomogeneities in a layered structure can increase the gripping force above the theoretical expectation. Microstructured dielectrics, combined with microstructured charge localization, can be used to geometrically control the electro-adhesion force. For example, the same device can both localize the device in living tissue and direct the mobility of cells relative to the device.

[0006] Another fact that deviates from theory is that the contact between the dielectric and the target object is never perfect. As described below, the microstructure of the surface can play an important role. It is the purpose of this disclosure to describe the use of layered microstructured surfaces that can significantly improve dielectric contact through local electric field forces (high field gradients) and the formation of composite hydrophilic / hydrophobic domains known as Wenzel-Cassie interfaces.

[0007] It should be appreciated that the electro-adhesion effect is one in which the total energy of the two surfaces apart is greater than the total energy of the two surfaces in contact. Conversely, the electro-repulsion effect is one in which the total energy of the two surfaces apart is less than the total energy of the two surfaces in contact. While this specification will use the word "electro-adhesion" to describe an adhering surface with high shear and peel forces, the opposite is also possible, a surface with low shear and peel forces.

[0008] These effects, due to the layered arrangement of micro-surface textures (random and regular), create a spatial resonance effect that strengthens and amplifies the relatively weak effects. In particular, the spatial resonance can result in interlocking regions of highly attractive and repulsive micro-regions in the interface between the microstructured surface and a variety of target surfaces.

[0009] These interlocking regions of attractive and repulsive micro-regions result in engineered surfaces that are to be adhered firmly to a surface without causing frictional or abrasive damage to the target surface. This type of engineered surface has particular value in surgical kits where manipulation of tissue can cause frictional or abrasive tissue damage and lead to post-surgical adhesions. Often, this frictional tissue damage is not observable by the naked eye and is often overlooked. Thus, many of the beneficial aspects of the microstructured electro-adhesion devices of this specification and applications have not been appreciated or anticipated. SUMMARY

[0010] The present application provides, in one embodiment, an electro-microstructured device that can include a microstructured surface and at least one electrode. The microstructured device can include at least one of a Wenzel or Cassie wetting state that can be changed by charging the electrode, and wherein charging the electrode can create an electro-adhesion state.

[0011] In one embodiment, the electro-microstructured device can include at least one electro-adhesion state that can result in adhesion to a target surface.

[0012] In one embodiment, the electro-microstructured device can include at least one electro-adhesion state that can induce a change in Wenzel-Cassie wetting state.

[0013] In one embodiment, the electro-microstructured device can include an electro-adhesion state in combination with a Wenzel-Cassie state that can position the device to a target surface.

[0014] In one embodiment, the electro-microstructured device can include charging at least one electrode that can cause at least a portion of the device surface to transition from one wetting state to another wetting state.

[0015] In one embodiment, the electro-microstructured device can include charging at least one electrode that can change the surface energy gradient on the device.

[0016] In one embodiment, the electro-microstructured device can include charging of at least one electrode in combination with a hierarchical microstructure that can produce a fluidic valve state.

[0017] In one embodiment, the electro-microstructured device can include charging of at least one electrode that can transition the electro-microstructured device from at least one of a hydrophobic and a hydrophilic surface to at least one of a hydrophilic and a hydrophobic surface.

[0018] In one embodiment, the electro-microstructured device can include charging of at least one electrode that can produce a wetting state that includes structured water.

[0019] In one embodiment, the electro-microstructured device can be configured to function as a braking system.

[0020] In one embodiment, the electro-microstructured device can be configured to function as a fluid / particle separation system.

[0021] In one embodiment, the electro-microstructured device can be configured such that the device can adhere to a wetted non-conductive surface.

[0022] In one embodiment, the electro-microstructured device can be configured such that the device can adhere to a wetted conductive surface.

[0023] In one embodiment, the electro-microstructured device can be configured such that the device can switch between a hydrophilic state and a hydrophobic state, the hydrophobic state being a removal of water from a portion of a wetted surface when the device is passed over the wetted surface.

[0024] In one embodiment, an electro-microstructured device can include a substrate having a layered microstructure disposed thereon. The substrate can include a thickness in which at least one electrode can be at least partially embedded within the thickness of the substrate. The electrode can also be connected to a charge source, where the at least one electrode is configured to provide a local electric charge when powered by the charge source, and the charging of the electrode creates an electroadhesive state.

[0025] In one embodiment, an electro-microstructured device can be configured such that the local electric charge of the at least one electrode produces a microscale electric field.

[0026] In one embodiment, an electro-microstructured device can include a first electrode and a second electrode. Both the first electrode and the second electrode can be embedded within the thickness of the substrate. The first electrode can be configured to produce a positive charge, the second electrode can be configured to produce a negative charge, and the first electrode and the second electrode can be adjacent to each other.

[0027] In one embodiment, an electro-microstructured device can include a substrate that is a dielectric.

[0028] In one embodiment, an electro-microstructured device can be configured such that the space between adjacent first and second electrodes can include an electrical insulator.

[0029] In one embodiment, an electro-microstructured device can include a plurality of electrodes that can be at least partially embedded within the thickness of the substrate and can be arranged in a spatially periodic pattern.

[0030] In one embodiment, an electro-microstructured device can include a layered microstructure that can utilize a composite post. The composite post can include at least a first microfeature and a second microfeature, where the second microfeature can be disposed around the first microfeature. In some embodiments, the composite post can also include a third microfeature disposed around the second microfeature, a fourth microfeature disposed around the third microfeature, and a fifth microfeature disposed around the fourth microfeature, and so on.

[0031] In one embodiment, an electro-microstructured device can include a first microfeature having a height of 100 microns or less and a diameter of 20 microns or less.

[0032] In one embodiment, an electro-microstructured device can include a second microfeature having a height of 5 microns or less and a diameter of 2 microns or less.

[0033] In one embodiment, an electro-microstructured device can include a substrate that includes at least a portion that is hydrophobic. The electro-microstructured device can also include an electrode that can be arranged with a layered microstructure to change the hydrophobic portion of the substrate to a hydrophilic portion when the electrode is charged.

[0034] In one embodiment, the electro-microstructured device can include a substrate comprising at least a portion that is hydrophilic. The electro-microstructured device can further include an electrode arranged with a layered microstructure to change the hydrophilic portion of the substrate to a hydrophobic portion when the electrode is charged.

[0035] In one embodiment, the electro-microstructured device can include at least a portion of the electrode arranged within the first microfeature.

[0036] In one embodiment, the electro-microstructured device can include at least a portion of the electrode arranged within the second microfeature.

[0037] In one embodiment, the electro-microstructured device can include a surface having a thickness and comprising a layered microstructure disposed thereon. The layered microstructure can include a layer of metal particles disposed thereon. Further, the device can include at least one electrode at least partially embedded within the thickness of the substrate and connected to a source of electrical charge, wherein the at least one electrode is configured to provide a local electrical charge when powered by the source of electrical charge, and wherein charging the electrode creates an electroadhesive state.

[0038] In one embodiment, the electro-microstructured device can be configured such that the layered microstructure can include a composite pillar. The composite pillar can include at least a first microfeature and a second microfeature disposed around the first microfeature.

[0039] In one embodiment, the electro-microstructured device can include metal particles having a diameter between 0.1 and 1.0 microns.

[0040] In one embodiment, the electro-microstructured device can be configured such that the layered microstructure includes two different microstructure regions, the metal particles in a first region comprising zinc, and the metal particles in a second region comprising silver.

[0041] In one embodiment, the electro-microstructured device can be configured such that the layered microstructure includes two different microstructure regions, the metal particles in a first region comprising zinc, and the metal particles in a second region comprising gold. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is an embodiment of an electroadhesive device.

[0043] Figure 2 is an embodiment of an electro-microstructured device.

[0044] Figure 3 is an embodiment of an electro-microstructured device.

[0045] Figure 4A and 4B is an embodiment of a tissue scaffold with cell type electrical selection.Figure 5 is an embodiment of a non-contact brake utilizing reversible Wenzel-Cassie domains.

[0046] Figure 6 is an embodiment of a blood filtration device using structured water valves and charge repulsion.

[0047] Figure 7 is an embodiment of a layered electrical microstructure adhesion device.

[0048] Figure 8 is an embodiment of a 4-stage layered arrangement of electrodes and surface microstructures on an electrical microstructure device.

[0049] Figure 9A and 9B is an embodiment of an electrical microstructure device for superhydrophobic / superhydrophilic conversion.

[0050] Figure 10 is an embodiment of a spiral field effect electrical microstructure device.

[0051] Figure 11 is an embodiment of an electrical adhesion microstructure device for wet conductive surfaces.

[0052] Figure 12 is an embodiment of an electrical adhesion microstructure device for non-conductive surfaces. DETAILED DESCRIPTION

[0053] Exemplary applications of the apparatus and methods according to the present disclosure are described in this section. These examples are provided solely to add context and assist with understanding the present disclosure. It will thus be apparent to one of ordinary skill in the art that the present disclosure can be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the present disclosure. Other applications are possible, and therefore the examples should not be taken as limiting.

[0054] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration specific embodiments of the present disclosure. While these embodiments are described in sufficient detail to enable those skilled in the art to practice the application, it should be understood that these embodiments are not limiting, and that other embodiments can be used, and that changes can be made without departing from the spirit and scope of the present disclosure.

[0055] As used herein, the term "electro-adhesion" refers to the coupling of two objects using electrostatic forces. Electro-adhesion as described herein can use electrical control of these electrostatic forces to allow for temporary and detachable attachment between two objects. This electrostatic adhesion holds the two surfaces of these objects together through Coulomb attraction forces or through the formation of Wenzel-Cassie domains between the surfaces of the device and the target. The formation of Wenzel-Cassie domains can be induced or enhanced by increasing the surface energy of the microstructured surface.

[0056] As used herein, the term "layered microstructure" when used to describe a three- dimensional plastic web, a matrix of protrusions, porosity, and any surface geometry modification has resulted in a surface that conforms to a three-dimensionally shaped structure such that both surfaces exhibit the three-dimensional pattern of the formed structure that is not readily visible to the normal human eye when the vertical distance between the viewer's eye and the plane of the microstructure is about 12 inches. It should be understood that the microstructure can be defined in any geometry and can include portions that are flat, circular, spherical, pyramidal, cylindrical, etc. The cross-section of individual microfeatures of the microstructure can be circular, square, triangular, circular with flutes, rectangular, or other geometric shapes, including combinations thereof.

[0057] Generally, as used herein, the term "macroscopic" is used to refer to structural features or elements that are readily visible to the normal human eye when the vertical distance between the viewer's eye and the plane of the web is about 12 inches.

[0058] The present disclosure describes devices having microstructured surfaces, where a portion of the surface can include discrete regions of charge. In some embodiments, the charge can be applied with a charge source and discrete electrodes embedded in the surface. In some embodiments, the charge can also be generated environmentally. It should be understood that the application or development of charge in one embodiment can be generated by multiple and / or different sources.

[0059] One embodiment utilizing electro-adhesion is shown in Figure 1 The electro-adhesive device 100 can include a charge source 102 that can be connected to electrodes 104 embedded in a dielectric substrate 106. The charge source 102 can charge one half of the electrodes 108 with a positive charge and the other half of the electrodes 110 with a negative charge. When the power source is on, the powered electro-adhesive device 100 can attract a substrate 112. Turning off the charge source 102 can result in the substrate 112 and the dielectric substrate 106 no longer attracting each other.

[0060] It is known that zinc generates an electrical potential when placed in a humid environment. Reference is made to Figure 2The electro-microstructured device 200 can include a flat polymeric substrate 202, which can include composite posts 204. The composite posts 204 can be composed of a base post 206 and a top post 208. The base posts 206 can be spaced in a triangular array with a pitch 208 (center-to-center distance) of 50 microns. The base posts 206 can have a vertical height 210 of 100 microns and a diameter 212 of 20 microns. The vertical surface of the base posts 206 can include a triangular profiled fin 214 with a width of 5 microns. The top posts 208 can have a diameter 216 of 2 microns and a vertical height 218 of 5 microns. The top posts 208 can be disposed on the top surface of the base posts 206, arranged in a triangular array with a pitch of 4 microns. In some embodiments, the base posts 206 can be of two types, described as Type A 220 and Type B 222. Type A base posts 220 can include a top post 208 disposed on the top surface, and further, the top surface 224 of the top post 208 can include a zinc particle deposit (0.1 to 1.0 microns in diameter). Type B base posts 222 can include a top post 208 disposed on the top surface, and further, the top surface 224 of the top post 208 can include a silver particle deposit (0.1 to 1.0 microns in diameter). The metal particles can be adhered using a solution that can include the polymeric substrate 202 (e.g., a solution of ethanol and a non-crosslinked polyurethane polymer).

[0061] When the device 200 is implanted in vivo, zinc can produce a voltage of -0.6 V and silver can produce a voltage of +0.2 V. Type A posts 220 and Type B posts 222 can be spaced about 30 microns apart between each post, as determined by the pitch measured from the center of each post to center, minus the diameter of each post (50 micron pitch - 20 micron diameter), which can produce a field gradient of 26 kV / m. It can be found that the adhesive force is directly proportional to the square of the field gradient.

[0062] The resulting electro-adhesive force can be influenced by the contact area between the electro-adhesive surface and the target surface, and can also be influenced by the polarization characteristics or dielectric constant of the target substrate. The contact area can be directly subject to the substrate surface texture of both surfaces (the electro-adhesive surface and the target surface). Thus, the substrate surface texture can need to be considered when developing microstructured surfaces. One approach to eliminate variability due to surface texture can be to construct the electro-adhesive appearance on multiple scales, referred to as hierarchical scales.

[0063] The microstructured electro-adhesive surfaces of the present disclosure can adhere to both conductive surfaces and insulating surfaces. The principles of creating electro-adhesive forces are different on conductive substrate materials versus insulating substrate materials, which are further detailed herein.

[0064] Electro-adhesion on conductive surfaces can be based on electrostatic induction as disclosed herein, while electro-adhesion on insulating surfaces can be primarily attributed to electric polarization. Modeling of electro-adhesion forces on conductive substrates can be approximated by a theory based on parallel capacitance (i.e., coplanar capacitance). Modeling of electro-adhesion forces on insulating substrates can be modeled by complex dynamic polarization processes.

[0065] In the embodiment shown in Figure 2 In the embodiment shown in

[0066] While saturation electro-adhesion forces can be obtained for conductive substrates quickly (typically within 1 second), in some embodiments, dynamic electrostatic attraction force generation processes are required. For example, in embodiments requiring short-term reversibility of adhesion, reversibility can be obtained when the electrode's zeta potential is slowed by adjusting the porosity of the dielectric and thus delaying the development of the zeta potential. As Figure 2 Embodiments as depicted in

[0067] The electro-adhesive devices of the present disclosure can use electrostatic forces between a target surface and a microstructured electro-adhesive surface at a microscopic level. For Coulombic electrostatic surfaces, electrostatic forces can be generated by dielectric polarization due to a potential difference. Based on the charge (or electrode) configuration, microstructured electro-adhesive surfaces can be divided into two types: unipolar (plate-plate-capacitor) and bipolar (interdigitated electrodes). These basic electrode configurations can be set on various levels of stratification. Complex mixtures of these basic electrode configurations can be further possible when the electrodes are externally charged.

[0068] Reference is now made to Figure 3An externally charged electro-microstructured device 300, including a flat polymer substrate 302, can include composite posts 304. The composite posts can be composed of a base post 306 and a top post 308. The base posts 306 can be spaced in a triangular array with a pitch of 50 microns (center to center distance). The base posts 306 can have a vertical height of 100 microns and can have a diameter of 20 microns. Further, the base posts 306 can include triangular profile fins 314 with a 5 micron diameter. The top posts 308 can include a 2 micron diameter and a 5 micron vertical height. The top posts 308 can include a center to center pitch of 4 microns. In some embodiments, the top posts 308 can be arranged in a triangular array.

[0069] In some embodiments, the base posts 306 can include two types of posts 320, 322. The base posts 306 can include A-type posts 320, which can include a top post 308 disposed thereon in layers, and a top surface 324 of the top post 308 can include a gold layer deposited thereon. Additionally, the top post 308 can further include a conductor 326, which can be embedded into the substrate and traverse into the layered composite. The base posts 306 can further include B-type posts 322, which can include a top post 308 disposed thereon in layers, and a top surface 328 of the top post 308 can include a gold layer deposited thereon. Additionally, the top post 308 can further include a conductor 332, which can be embedded into the substrate and traverse into the layered composite. In one embodiment, the flat polymer substrate 302 can include a deposited gold circular layer 334, which can be in contact with a conductor 336. In some embodiments, the gold layer can be coated or left exposed, or can include one coated region and another exposed region.

[0070] In some embodiments, the electrode configuration can be obtained by charging the gold layer of the A-type posts and the gold layer of the B-type posts at a potential difference. In one embodiment, +0.5 V on the conductor 326 and -0.5 V on the conductor 332 can generate a charge through the potential difference of the conductors. In another embodiment, the conductor 336 can be charged differently from the conductor of the self-charging gold layer. When the gold layers 324 and 328 form a field gradient, the electrode configuration can be approximately unipolar. When the gold layers 324 and 328 are charged differently, the electrode configuration can be bipolar.

[0071] The electrode geometry and pitch as disclosed herein can work in concert with the microstructured surface. In some embodiments, the microstructured surface is a layered stack, which can provide the opportunity for layered electrodes on different layer levels in a unipolar configuration. Within a layer level, the electrodes can be further spaced apart in a bipolar configuration. For externally provided charge, different regions of the electro-microstructured device can be unipolar, while other regions can be bipolar.

[0072] A unipolar microstructured electroadhesive surface can generate adhesion. In this embodiment, one of the electrodes can contact the target surface, with the second electrode insulated from the target surface by a dielectric layer. The target surface can be electrically conductive, such that a capacitor is formed between the electrode and the electrically conductive target surface.

[0073] A bipolar microstructured electroadhesive surface can generally be composed of interleaved electrodes of two charged regions. In this embodiment, the electrodes can be insulated from the target surface by a dielectric layer. The space between the electrodes can be filled with an electrical insulator. For a microstructured device, a Wenzel-Cassie interface can be formed, with air bubbles trapped between the electrodes. The air bubbles can act as insulators. In some embodiments, the trapped substance can be oil, attracted by the hydrophobic matrix. When the oil is trapped, for example, between the posts, it can act as an insulator and a dielectric.

[0074] When alternating positive and negative charges are induced on adjacent electrodes and the device is placed in contact with a target surface, an electric field can generate opposite charges on the target surface, thus creating electrostatic adhesion between the charges induced on the electrodes and the target surface.

[0075] One important distinction of the unipolar configuration is that each hierarchical level can not be continuous. This configuration is advantageous because the discontinuity creates “holes” or gaps between the plates. This configuration can be counterintuitive based on prior art because the electric field can be highest in the dielectric between the two electrodes rather than on the target surface that the device is in contact with.

[0076] The gaps can allow the electric field to essentially “leak” to the target surface. This “leakage” can result in a stronger electric field than a traditional bipolar design. This is because the hierarchical design can allow for significantly smaller gaps between the electrodes. The gap size can have a large impact on the adhesion force per unit area. Smaller gaps are possible in this configuration because the hierarchical design can allow for a dielectric with a high voltage breakdown constant compared to a standard bipolar design.

[0077] Further considerations regarding the gap size between the electrodes depend on any residual material in the gap, external particles, and trapped air. Because of the sensitivity of the gap to these issues, the addition of a microstructured surface can play an important role. By designing the microstructure to have a specific juxtaposition of surface energies, the interface constituents can be attracted or repelled.

[0078] Generally, prior art relies on macroscopic electrode structures, typically larger than a few millimeters. In this macroscopic design, the electroadhesive stress and energy can be estimated by empirical equations. However, these equations are not successful at the microstructure level. Furthermore, the lack of a theoretical model to reveal the relationship between adhesion and microstructure parameters is disclosed herein.

[0079] Electro-adhesion and electro-repulsion devices used in the prior art do not have optimal design principles. Some progress has been made on the electrostatic levitation problem, but the model applies to macroscopic electrodes. When it comes to microscopic electrodes, if the goal is to create a surface that cycles between electro-adhesion and non-electro-adhesion, special attention must be paid to optimizing the charging rate with respect to the geometric parameters of the electrodes. One example could include the development of the foot surface of a wall-climbing robot.

[0080] It should be appreciated that the following examples can employ four- and five-layer hierarchical textures, although in practice any number of layers (as long as they are hierarchical) can be sufficient for most applications.

[0081] With respect to electro-adhesion on a conductive target surface, electrostatic induction phenomena can occur in which an external electrostatic field generated by a charged electrode embedded into an insulator that includes a microstructured surface can induce a negative charge on one side of the target conductor and a positive charge on the opposite side of the target conductor.

[0082] It should be appreciated that“conductive material” can generally refer to a material composed of a large number of mobile free charge carriers. In some embodiments, wetting tissue can cause the concentration of free mobile charge carriers to be on the same order of magnitude as the concentration of the number of molecules. These charges can be quickly and easily rearranged. After the application of a high field gradient on an electrical microstructured surface / device, equal and opposite charges can be induced on the surface of the target conductive substrate. An electro-adhesive force between the device and the target surface can then be formed.

[0083] In some embodiments, an electrical microstructured device can be unipolar, bipolar, and / or even tri-polar. In the prior art, a dipole design is generally the most commonly used design in electro-adhesion applications. For a Coulomb-type dipole electrical microstructured device, the electro-adhesive force between the device and the target substrate can result from a series of parallel connections of several ideal capacitors with a series dielectric. Particular parameters that can be of special interest for efficiently producing an electro-adhesive force include the air gap between the device and the target substrate, the dielectric thickness, the capacitance of the dielectric material, the interfacial capacitance between the dielectric and the target substrate surface. The total capacitance between the device and the target substrate and between the pad and the substrate can depend on the number of electrodes, the effective electro-adhesive area, the dielectric constant of the interfacial volume, and the relative dielectric constant of the dielectric. The electro-adhesive force varies as the square of the total capacitance.

[0084] Johnsen-Rahbek forces can arise when imperfect dielectrics with finite bulk resistivity, such as semiconducting materials, interact with high charge mobility target substrates. Current leakage or charge transfer can occur through contact points between the device and the target substrate. In some embodiments, strong electrostatic attractive forces can be generated at the interface by charge accumulation in the non-contact region. Small gap features of the hierarchical microstructured surface can be responsible for these strong Johnsen-Rahbek adhesion forces.

[0085] The adhesion of Johnsen-Rahbek electro-microstructured devices can depend on the potential difference applied across the interface, rather than the field gradient applied through the dielectric layer. Johnsen-Rahbek electrostatic attractive forces are independent of the dielectric material between the device and the target substrate. The specific parameters that can be determined to generate these forces in the microstructured device can include the capacitance of the non-contact region, the potential difference across the interface, and the potential difference across the non-contact region. In some embodiments, the stacked hierarchical structure is optimal for both gap placement and electrode placement.

[0086] In general, adhesion due to Coulombic potential can be much smaller than Johnsen-Rahbek forces, especially in embodiments where the interfacial gap is smaller than the thickness of the dielectric material.

[0087] In embodiments for cyclic adhesion devices, the separation time can be much faster when using Coulombic forces. In addition, less current leakage in Coulombic configurations can result in lower power consumption.

[0088] In some embodiments, electro-microstructured devices can involve a sum of polarizations including electronic polarization, ionic polarization, orientation polarization, space charge polarization, hopping polarization, interfacial polarization, spontaneous polarization, and other types of polarization such as nomadic polarization.

[0089] For embodiments with contact electro-microstructured devices, orientation polarization and interfacial polarization can explain the generation of electro-adhesion forces. The electro-adhesion phenomenon can be non-contact for both conductive and insulating substrates. For embodiments with non-contact electro-microstructured devices, atomic and electric polarization can account for the generation of electro-adhesion forces.

[0090] It should be appreciated that in the presently disclosed devices, electro-adhesion can strengthen over time. The steady-state value of the adhesion force can generally be much larger than the initial value. The time period to reach the steady-state value can depend on various design parameters.

[0091] In embodiments including certain monopolar electrode geometries, the electrodes can generally be arranged in a spatially periodic pattern. Generally, the length of the electrodes can be much greater than their width and / or thickness, and the electrode area can be much greater than the area between individual electrodes. For this reason, in some embodiments, a symmetric pattern can be preferred.

[0092] Those skilled in the art will recognize that layered structures are included in various embodiments of the present disclosure. Analyzing the performance of an electro-adhesion device with a layered structure, each layer scale can be treated as an additional layer and the calculation performed as if the device were a composite device with an effective dielectric constant. The effective dielectric constant can be evaluated by the rule of mixtures in parallel. Calculations show that electro-adhesion can decrease as the layer height of each layer increases. Therefore, in some embodiments, the layer height of the layering can decrease as the size decreases, so more layers can increase the electro-adhesion properties of the device.

[0093] Some embodiments can combine the electro-adhesive force with the van der Waals force of a microstructured surface to produce a strong adhesion force. Microstructures as small as microns or even nanometers in size can produce a strong adhesion force. Therefore, the smallest structures can not only reduce the gap between the device and the target surface, but can also absolutely enhance the attractive force. In one embodiment, an electro-adhesion device can be able to produce both electro-adhesive force and van der Waals force.

[0094] Another parameter that can be used is the inclusion of a semiconductor material for the insulating layer or microstructured substrate, which can enhance the electrostatic clamping force at lower electric field levels. This increased clamping force can be attributed to the Johnsen-Rahbek effect that can occur at the boundary between the metal electrode and the surrounding semiconductor material. Therefore, when using a semiconductor insulator instead of a completely dielectric insulator, lower voltages and currents can be used to achieve the same clamping force.

[0095] While polyurethane is known to work well as a semiconductor material, various other materials can also be used. These other semiconductor materials can generally have a bulk resistivity ranging from about 107to 1013Ωm, with a more preferred range of about 109to 1012Ωm. For example, various polyurethanes, nitrile butyl halogenated or latex rubbers, and certain silicones can be used as suitable insulating materials for some embodiments of the disclosed electro-adhesion devices. Deerfield polyurethane PT7811 is one material that works well.

[0096] In some embodiments, particulates, dopants, and / or solutions can be included to enhance the electrical conductivity of other insulating polymers. These particulates can include, but are not limited to, carbon, quaternary salts, and plasticizers such as dioctyl phthalate or diisooctyl phthalate.

[0097] In one embodiment using such a material, it can be possible to achieve a clamping force of up to about 70 psi. In one embodiment using a coating on the electrode rather than a full insulating layer, the coating can be about 10 to 30 microns thick. In other embodiments, the use of a semi-conductive insulator can allow for the use of an insulating layer that can be up to 100 microns thick. In various embodiments, the insulating material can include a compliant material with an elastic modulus of less than about 1 GPa, which can facilitate better clamping.

[0098] In addition to the use of high resistance materials in some embodiments of the disclosed adhesive devices, semi-conductive materials with different properties can also provide benefits when used as the electrode itself. In one embodiment, various polyurethanes or other materials can be used at least on the surface of one or more electrodes. For embodiments with high resistance electrodes, the electrostatic dissipative conductive strip material can have a surface resistivity ranging from about 0.1 to 1000 MΩ / square, a thickness of about 1 to 50 microns, be relatively inexpensive and readily available, and be mechanically and electrically robust. More preferably, the surface resistivity can be in the range of 1 to 100 MΩ / square. It is contemplated that one embodiment can include carbon particles mixed with a relatively soft polyurethane. Such polyurethanes can be spray, dip, or otherwise applied to a suitable electrode surface. Other alternatives for electrode materials can utilize nanotubes, which can conduct electricity at much lower load levels. Yet another option can include a graphite electrode with a thin coating as a sealing layer that can be applied, for example, by spraying. Embodiments with such a sealing layer can include very low carbon black loading, or none at all in some embodiments. Other options can include the addition of plasticizers or flexible polyurethanes blended in tetrahydrofuran. Di-iso-octyl phthalate can also be used as a polyurethane plasticizer. Examples of various specific materials that have been found to work well include Dupont 100XC10E7, Scicron ABF-300, and TMF-300 materials.

[0099] The following are embodiments that can be directed to the design of the electrical microstructure surface. These embodiments are not meant to be exhaustive, but rather examples of principles to guide the practice of this patent.

[0100] Example 1. Tissue scaffolds with cell type electrical selection

[0101] Biological materials are widely used in the medical field to maintain, improve, and / or restore diseased tissues or organs. The successful integration of a biological material with host tissue can depend on the substrate surface properties, as well as the host tissue quality and surrounding environment. Embodiments, defined more fully below, can utilize these different factors to allow for better incorporation of host tissue and biological materials.

[0102] Reference Figure 4A and 4Bmicrostructured posts 402 disposed on a polymer substrate 404. The microstructured posts 402 can be arranged in rows. In some embodiments, the rows of microstructured posts 402 can also include smaller posts 406 disposed between two opposing rows of microstructured posts. The two opposing rows of microstructured posts 402 can include a spacing of about 10 microns between the two rows, 408a. Additionally, the microstructured posts 402 within the same row can also be spaced about 10 microns apart, 408b. The microstructured posts 402 can include an interior portion 410 that can include an electrode 412 along a centerline of the microstructured post. Some of the electrodes 412 can be electrically connected by conductors 414, 416. The conductors 414 can have a positive electrical potential and the conductors 416 can have a negative electrical potential, thereby creating a field gradient in an area 418 located between two opposing rows of microstructured posts 402. The opposing rows of microstructured posts 402 can be positioned to create a symmetrical relationship as shown by the squares 420, 422, and 424. Within each square is a Y-shaped configuration 426 having a base 428, a left branch 430, and a right branch 432. The left and right branches can be connected to an adjacent base as shown at 434, thus creating a repeating pattern on the polymer substrate 404.

[0103] In some embodiments, the microstructured posts 404 can be about 10 microns high and about 3 microns in diameter with a circular cross-section. The smaller posts 406 can be about 3 microns high and about 1 micron in diameter with a circular cross-section. In one embodiment, the open area 436 of the substrate surface 404 can be filled with ridges 438 and wherein the ridges can be about 10 microns high and about 3 microns thick with a rectangular cross-section.

[0104] In some embodiments, cells disposed around the periphery 440 of the tissue scaffold 400 can be caused to move along the passageway 411 between opposing rows of microstructured posts 402. In some embodiments, the Y-shaped configuration 426 can facilitate the formation of blood vessels by endothelial cells.

[0105] Example 2. Non-contact brake created with reversible Wenzel-Cassie domains.

[0106] Reference Figure 5 The brake system 500 can include a brake element 502 and a rotating element 512. The brake element 502 can include a surface that includes a first hierarchical level 504, a second hierarchical level 506, and a third hierarchical level 508. In some embodiments, the first hierarchical level 504 can have a square cross-section. In some embodiments, the second hierarchical level 506 can have a circular cross-section. And in some embodiments, the third hierarchical level 508 can have a circular cross-section. In some embodiments, the brake element 502 can include two or more bearing channels 510.

[0107] In some embodiments, the rotating element 512 can include a surface that can be smooth. In other embodiments, the rotating element 512 can include a surface having microstructures disposed thereon. In some embodiments, the rotating element 512 can include a surface having both smooth portions and microstructured portions. In some embodiments, the rotating element can include at least two bearing channels 514. The bearing channel 510 of the braking element 502 and the bearing channel 514 of the rotating element can align and create a cavity. In some embodiments, the cavity can contain at least one ball bearing 516. In addition, the cavity can also contain a friction-reducing composition 518 that coats and / or surrounds the at least one ball bearing 516. In some embodiments, the bearing channels 510 and 514 can be positioned along the peripheral sides of the braking element 502 and the rotating element 512, creating an internal chamber 520. In some embodiments, the internal chamber 520 can be sealed and contain therein a hydrophilic liquid 522 and an insoluble hydrophobic liquid 524. The volumes of the hydrophilic liquid 522 and the insoluble hydrophobic liquid 524 can vary depending on the application. In some embodiments, the volume of the hydrophilic liquid 522 can be greater than the volume of the insoluble hydrophobic liquid 524. In other embodiments, the volume of the insoluble hydrophobic liquid 524 can be greater than the volume of the hydrophilic liquid 522. And in some embodiments, the volumes of each liquid 522, 524 can be approximately the same. It should be understood that while the term "liquid" is used herein, the term also includes semi-liquids, gels, viscous compositions, and the like. In some embodiments, the volume of the insoluble hydrophobic liquid 524 is less than the volume of the hydrophilic liquid 522, such that when the braking element 500 is moved, the hydrophobic liquid can form small globules 532 while disposed in the hydrophilic liquid.

[0108] Some embodiments of the rotating element 512 can include a surface that includes a first hierarchical level 526, a second hierarchical level 528, and a third hierarchical level 530. The first hierarchical level 526 can have a square cross-section. The second hierarchical level 528 can have a circular cross-section. The third hierarchical level can also have a circular cross-section. In some embodiments, the combined hierarchical microstructures 526, 528, and 530 can create a hydrophobic effect. Similarly, in some embodiments, the combined hierarchical microstructures 504, 506, 508 of the braking element 502 can also create a hydrophobic effect.

[0109] As a practical view, one embodiment of the braking system 500 can be used such that the braking element 502 is not powered and the rotating element 512 is rotating and moving. When this state occurs, the spheres 532 of the hydrophobic liquid 524 can be brought into contact with the microstructures 528, 530 of the rotating element 512 and the microstructures 506, 508 of the braking element 502. In this embodiment, the spheres 532 can act as micro ball bearings themselves. The hydrophilic liquid 522 can flow or move in the gaps created between the microstructures 526 and the braking element surface and between the microstructures 504 and the rotating element surface.

[0110] In some embodiments, the first hierarchical level 504 can contain alternating electrodes 534, 536 between adjacent microstructures. The electrodes 534 can be positively charged and the electrodes 536 can be negatively charged. Powering the electrodes 534 and 536 can cause the second and third hierarchical microstructures 506, 508 to transition from a Cassie state to a Wenzel state. When this transition occurs, the hydrophobic liquid 524 can migrate from the second and third hierarchical microstructures 506, 508 disposed on the braking element 502 to the second and third hierarchical microstructures 528, 530 on the rotating element 512. This transition of the hydrophobic liquid can create a locked Wenzel-Cassie state 538, which results in the rotating element 512 reducing its rotation.

[0111] Example 3. A blood filtration device using structured water valves and charge repulsion.

[0112] Sialylated glycoproteins on the surface of red blood cells can be the cause of the negative zeta potential. Referring to Figure 6 The blood filtration device 600 can include a surface having composite posts disposed thereon. The composite posts can be arranged in a hierarchy and include first posts 602 and second posts 604. The second posts 604 can be arranged on top of the first posts 602 in a hierarchical manner. In some embodiments, the composite posts can be arranged in rows 606. In some embodiments, the rows of composite posts can be further arranged such that multiple rows 608 are adjacent to each other and parallel to each other, forming columns.

[0113] In some embodiments, each first post 602 can include an electrode 610 associated therewith. In embodiments having at least three parallel rows 608, the rows can be electrically configured such that two adjacent columns 612 can have the same charge and a third column 614 can have an opposite charge. For example, two adjacent posts 612 can be positively charged while a third post 614 can be negatively charged. As a result of this configuration, the space between adjacent posts 612 and 614 having opposite charges creates a structured water state 615 in which the polarity of the water causes water molecules to align and can exclude microparticles such as red blood cells 616. Embodiments having this or a similar configuration can create a valvelike mechanism that can exclude microparticles but allow water to flow in a channel 618. The two positively charged columns of posts 612, 620 can undergo a sinusoidal variation in electric potential that can cause red blood cells 616 to be attracted and then pass in a direction 622 along the spatially varying surface energy lines.

[0114] In some embodiments, an inlet 624 can be configured to allow whole blood to enter under slight pressure. Whole blood entering through inlet 624 can then travel along the rows and columns of microstructured posts. Although Figure 6 A plane oriented perpendicular to gravity is shown, but other embodiments can include different configurations that can be advantageous. In one embodiment, vertically arranging parallel rows and columns can create a chimney effect. In addition, it can be effective to arrange red blood cell conductive channels in opposition to gravity and to arrange filtrate conductive channels in the direction of gravity. In this oppositional configuration, one can imagine a chimney discharge configuration in which a chimney effect can be achieved by a spatially varying gradient while a discharge effect can be achieved by gravity. This chimney discharge device can be reversed for the filtration of other components in blood, such as platelets.

[0115] Example 4. Hierarchical electric microstructured adhesive device.

[0116] Referring now to Figure 7 An electric microstructured adhesive device 700 is disclosed and can include composite posts 702. In some embodiments, the composite posts 702 can be flexible and in some embodiments, the composite posts can be rigid. In some embodiments, the composite posts 702 can be arranged in a regular pattern or a random pattern. In certain embodiments, a random pattern of composite posts 702 can be preferred to facilitate the device 700 adhering to surfaces of different microstructures. The composite posts 702 can have any cross-sectional shape. In some embodiments, the cross-section can be circular or elliptical. In embodiments having an elliptical cross-section, the major axis of the ellipse can be arranged randomly or in a concentric pattern.

[0117] In some embodiments, the composite post 702 can include a first post 704, a second post 706 stacked on the first post 704, and a third post 708 further stacked on the second post 706, thus incorporating a layered structure. The first posts 704 can be spaced apart from each other from the center over a length equal to the total height of their entire layered structure. In some embodiments, the height of the first posts 704 can be between 100 to 1000 microns. The height of the second posts 706 can be between 35 and 100 microns. The height of the third posts 708 can be between 1 to 35 microns. In some embodiments, the third posts 708 can be spaced apart from the center over a length between 0.1 to 1.5 times the length of the height of the posts 708.

[0118] In some embodiments, the composite post 702 can be disposed on a substrate 710 of the device 700. The substrate 710 can have a thickness that embeds positively charged electrodes 712 and negatively charged electrodes 714. In some embodiments, adjacent to each positively charged electrode 712 is a negatively charged electrode 714.

[0119] In some embodiments, the electrical adhesion of the device 700 to a target surface can be generated by charging the electrodes 712, 714 via wires 716, 718.

[0120] Example 5. Four-level layered arrangement of electrodes and surface microstructures on an electro-microstructured device.

[0121] Referring now to Figure 8 , a single four-level microstructure 800 is shown. In some embodiments, the microstructure 800 can be used in place of the composite post 702 disclosed in Example 4. In some embodiments, the overall electrode structure of Example 4 can remain the same with the four-layer microstructure 800. In one embodiment, the first microstructure 802 can be hemispherical and disposed around the surface 810 of the device. The second microstructure 804 can be cylindrical and disposed around the first microstructure 802. The third microstructure 806 can be cylindrical and disposed around the second microstructure 804. The fourth microstructure 808 can be a circular fibrous configuration and disposed around the third microstructure 806. The electrode 812 can be hemispherical and have a similar geometry as the first microstructure 702. The electrode 812 can be associated with and charged by a lead 816.

[0122] Example 6. A superhydrophobic / superhydrophilic conversion electro-microstructured device.

[0123] Referring now to Figure 9A and 9B , a superhydrophobic / superhydrophilic conversion electro-microstructured device 900 is shown. Figure 9B The right side 902 is shown depicting a superhydrophobic state, while Figure 9AThe left side 904 shown depicts a super-hydrophilic state. The electro-structured device 900 can include a substrate layer 906. A first post 908 and a second post 910 can be disposed around the substrate layer 906. The first post 908 and the second post 910 can be arranged in layers. In some embodiments, the first post 908 can have a hexagonal cross-section. In some embodiments, the second post 910 can have a circular cross-section. In some embodiments, the substrate layer 906 can include a thickness in which an electrode 914 is disposed. In some embodiments, a second electrode 912 can be disposed around the second post 910. Further, in some embodiments, a final hydrophobic coating 916 can also be included.

[0124] In one embodiment, the second electrode 912 can be disposed around the top of the second post 910. The second electrode 912 can be arranged to cover the entire upper surface of the second post 910 or can partially cover the upper surface. In one embodiment, the electrode can have an opposite charge from the first electrode 914. The first electrode 914 can be disposed within the thickness of the substrate layer 906 and can generally be located in the area between the first posts 908. When the electrodes 912, 914 have opposite charges, then the structure can have super-hydrophilic properties and achieve a Wenzel wetting state 918. When the electrodes 912, 914 have the same charge, the structure can exhibit super-hydrophobic properties and achieve a Cassie non-wetting state 920.

[0125] Example 7. Spiral field effect electro-microstructure device.

[0126] Reference is now made to Figure 10, a helical field effect electro-microstructure device 1000 is shown. In some embodiments, such a helical structure can be used to quickly reverse the hydrophilic / hydrophobic state of the device. The device 1000 can include a tapered post 1002 with ridges 1004 on the outer wall of the post 1002. In one embodiment, two tapered posts 1006, 1008 can be adjacent to each other and in which an elevated surface energy in a downward direction 1010 is created between them. Such an elevated surface energy can create a capillary force in the downward direction 1010. In some embodiments, the tapered post 1002 can have an interior in which an electrode 1012 is disposed. In one embodiment, the electrode 1012 can be arranged in a helical configuration. The helical configuration can be uniform, or the helical configuration can taper outwardly as the diameter of the tapered post 1002 increases. When the electrode 1012 is not energized, the surface can be Wenzel wetted. When the electrode 1012 is energized, in embodiments in which the electrode tapers outwardly, the field strength increases as the electrode becomes more tightly wound as it approaches the peak of the tapered post 1002. When two adjacent tapered posts 1006, 1008 with tapered electrodes 1016, 1018 have opposite charges, then the surface energy gradient can be reversed compared to the uncharged state, resulting in a Cassie wetted state.

[0127] Example 8. An electro-adhesive microstructure device for a wet conductive surface.

[0128] Referring now to FIG. 11, an electro-microstructure device 1100 for adhesion to a wet conductive surface is shown. The device 1100 can include a substrate layer 1102, a first post 1104 with ridges 1106, a second post 1108, an electrode 1110, and a conductor 1112. In some embodiments, the substrate material can be hydrophilic and naturally wetted. The device 1100 can be configured such that when the device contacts a wet conductive surface, water can be quickly wicked away, as shown by the arrows 1114. When the water is wicked away quickly, the electrode 1110 can be close to the conductive surface 1116, which can greatly enhance the electro-adhesion of the device 1100.

[0129] Example 9. An electro-adhesive microstructure device for a non-conductive surface.

[0130] Referring now to FIG. 12, an electro-microstructure device 1200 for adhesion to a non-conductive surface is shown. The device 1200 can include a substrate layer 1202, a first post 1204 with ridges 1206, a second post 1208, an electrode 1210, and a conductor 1212. In some embodiments, the substrate material can be hydrophobic and naturally wetted. The device 1200 can be configured such that when the device contacts a non-conductive surface, water can be quickly wicked away, as shown by the arrows 1214. When the water is wicked away quickly, the electrode 1210 can be close to the non-conductive surface 1216, which can greatly enhance the electro-adhesion of the device 1200. Figure 12, showing an electric microstructure device 1200 for adhering to a wet, non-conductive surface. The device 1200 can include a substrate layer 1202, a first post 1204 (with a ridge 1206), a second post 1208, electrodes 1210, 1212, and conductors 1214, 1216. In some embodiments, the substrate material can be hydrophilic and naturally wetting. The device 1200 can be configured such that when the device contacts a wet, non-conductive surface, water can be quickly wicked away. When the water is wicked away quickly, the electrode 1210 can be in close proximity in a unipolar configuration.

[0131] Thus, although particular embodiments of the present disclosure of novel and useful microstructure field effect devices have been described herein, these should not be taken as limiting upon the scope of the present disclosure, except insofar as such limitations are expressly stated in the following claims.

Claims

1. An electrical microstructure device, comprising: A substrate having a layered microstructure, the substrate having a thickness, the layered microstructure including a composite pillar, the composite pillar including at least a first microfeature and a second microfeature, the second microfeature being disposed around the first microfeature; as well as A first electrode and a second electrode, the first electrode and the second electrode being at least partially embedded within the thickness of the substrate and connected to a charge source, wherein when powered by the charge source, the first electrode is configured to provide a positive charge of +0.5V and the second electrode is configured to provide a negative charge of -0.5V, and wherein charging the first electrode and the second electrode generates an electroadhesive state via the Wenzel-Cassie wetting domain.

2. The electrical microstructure device according to claim 1, characterized in that, The first electrode is configured to provide localized positive charge, which generates a micrometer-scale electric field.

3. The electrical microstructure device according to claim 1, characterized in that, The first electrode and the second electrode are adjacent to each other.

4. The electrical microstructure device according to claim 1, characterized in that, The substrate is a dielectric.

5. The electrical microstructure device according to claim 3, characterized in that, The space between adjacent first and second electrodes includes an electrical insulator.

6. The electrical microstructure device according to claim 1, characterized in that, The first and second electrodes also include a plurality of electrodes, which are at least partially embedded within the thickness of the substrate, and the plurality of electrodes are arranged with alternating positive and negative charges.

7. The electrical microstructure device according to claim 1, characterized in that, The first micro-feature has a height of 100 micrometers or less and a diameter of 20 micrometers or less.

8. The electrical microstructure device according to claim 1, characterized in that, The second micro-feature has a height of 5 micrometers or less and a diameter of 2 micrometers or less.

9. The electrical microstructure device according to claim 1, characterized in that, The substrate further includes at least a hydrophobic portion, and the electrodes are arranged with a layered microstructure, thereby changing the hydrophobic substrate portion into a hydrophilic portion when the electrodes are charged.

10. The electrical microstructure device according to claim 1, characterized in that, The substrate further includes at least a hydrophilic portion, and the first and second electrodes are arranged with layered microstructures such that the hydrophilic substrate portion is converted into a hydrophobic portion when the electrodes are charged.

11. The electrical microstructure device according to claim 1, characterized in that, At least a portion of the first electrode is disposed within the first micro-feature.

12. The electrical microstructure device according to claim 1, characterized in that, The first electrode is not located within the second micro-feature.

13. An electrical microstructure device, comprising: A substrate having a thickness includes a layered microstructure disposed thereon, wherein the layered microstructure includes a layer of metal particles disposed thereon, the layered microstructure includes a composite pillar, the composite pillar including at least a first microfeature and a second microfeature, the second microfeature being disposed around the first microfeature; A first electrode and a second electrode, the first electrode and the second electrode being at least partially embedded within the thickness of the substrate and connected to a charge source, wherein when powered by the charge source, the first electrode is configured to provide a positive charge of +0.5V and the second electrode is configured to provide a negative charge of -0.5V, and wherein charging the first electrode and the second electrode generates an electroadhesive state via the Wenzel-Cassie wetting domain.

14. The electrical microstructure device according to claim 13, characterized in that, The first micro-feature has a height of 100 micrometers or less and a diameter of 20 micrometers or less.

15. The electrical microstructure device according to claim 13, characterized in that, The second micro-feature has a height of 5 micrometers or less and a diameter of 2 micrometers or less.

16. The electrical microstructure device according to claim 13, characterized in that, The metal particles have a diameter ranging from 0.1 to 1.0 micrometers.

17. The electrical microstructure device according to claim 13, characterized in that, The layered microstructure also includes two distinct microstructural regions, in which the metal particles contain zinc in the first region and silver in the second region.

18. The electrical microstructure device according to claim 13, characterized in that, The layered microstructure also includes two distinct microstructural regions, in which the metal particles contain zinc and in the second region, the metal particles contain gold.

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