HK1262339A1 - Low normal force retracting device comprising a microstructured surface - Google Patents

Description

Low normal force retractor instrument including microstructured surface

RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No. 62/237,448, filed on 5/10/2015, the contents of which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure relates to surgical retractors that include a micro-textured surface. The surgical retractor includes a microtextured surface on one or more portions of the retractor to advantageously provide a fixation or positioning force to a wet tissue surface while preventing or minimizing damage or trauma to the tissue.

Background

There are many natural and man-made objects characterized by relatively durable surfaces that enclose fine structures that are adversely altered by forces applied normal to the durable surface and are not altered by forces applied tangentially or in-plane to the durable surface. Accordingly, there is a need in the art for a retraction instrument that allows these objects to be secured, repositioned, or positioned without internal damage due to the force applied by the retractor.

A non-limiting example is the retraction of living tissue during a medical procedure such as surgery. In these procedures, it is often necessary to retract the organ to reach the target organ or tissue to be treated or observed. In other procedures, in order to reach the organ or tissue to be treated or observed, the organ to be treated must be separated from the tissue surrounding it. For example, in order to be able to view the outer surface of the heart, it must be separated from the pericardium. To achieve the necessary retraction, current laparoscopic procedures use several small retractors inserted through multiple incisions. Because such retractors have a relatively small surface area, they tend to cause damage and/or trauma to the retracted organ or tissue through the application of localized normal forces.

The Wenzel, Cassie, and Wenzel-Cassie states describe the phenomenon of wetting between the hydrophobic and hydrophilic components of a mixture at a surface interface. The Cassie-Baxter model describes the interaction of solid textured surfaces with water in a gaseous environment. In this model, air is trapped in the microgrooves of the textured surface and water droplets settle on the composite surface including the air and the tops of the microprotrusions. The importance of fractal dimension (fractional dimension) between multiple texture scales (scales) is well recognized and many methods are based on fractal contribution, i.e. the dimensional relationship between textures of different scales.

However, regardless of the materials used (organic or inorganic) and the geometry of the surface texture (particles, rod arrays or pores), multiple texture scales combined with low surface energy are required to obtain a so-called superhydrophobic surface. Superhydrophobicity is variously reported as a material that exhibits a contact angle with water that is greater than that achievable with a smooth but strongly hydrophobic material. The general consensus on the minimum contact angle for superhydrophobic materials is 150 degrees.

Hydrophobic surfaces repel water. For example, the hydrophobicity of a surface can be measured by determining the contact angle of a drop of water on the surface. The contact angle can be measured statically or dynamically. Dynamic contact angle measurements may include determining an advancing contact angle or a receding contact angle with respect to an adherent substance, such as a water droplet. Hydrophobic surfaces with a small difference between advancing and receding contact angles (i.e. low contact angle hysteresis) result in surfaces with low resistance to in-plane translation (low adhesion). Water may pass more easily through a surface with a low contact angle hysteresis than through a surface with a high contact angle hysteresis, and thus the magnitude of the contact angle hysteresis may be equivalent to the amount of energy required to move a substance.

A classic motivation from nature for surface texture studies is that lotus leaves, which have super-hydrophobicity due to a hierarchical structure with raised cell papillae and randomly oriented hydrophobic wax tubules, have high contact angle with water and low contact angle hysteresis, and show strong self-cleaning properties. A less understood motivation from nature is red rose petals, a hierarchical structure of raised cell papillae decorated with circumferentially disposed and axially oriented ridges with moderate contact angles and high angular contact differences.

Contact angle is a measure of the amount of water in direct contact with the textured surface, while contact angle hysteresis is a measure of the degree to which water can flow on the surface. The evolutionary motivation for each of these states is very obvious. In the case of lotus leaves and generally plant leaves, minimal contact with water and high fluidity of water results in preferential attachment of water to particulate contaminants which are removed from the leaves as the water is lost. This helps to reduce the amount of light absorbed by surface contaminants and improves photosynthetic efficiency. In the case of rose petals and typical plant petals, most pollinators are attracted to a high-tension water source that is readily available without flooding the insects. Thus, in the case where the evolution stimulus is plant propagation, high contact angle and high contact angle hysteresis pairing is preferred, and in the case where the evolution stimulus is metabolism and growth, high contact angle and low contact angle hysteresis pairing is preferred.

Considering briefly a single texture dimension, when water is placed on the textured surface, it may be on the peaks of the texture or sucked into the valleys. The former is called Cassie state, the latter is called Wenzel state. When the Wenzel regime dominates, both the contact angle and contact angle hysteresis increase with increasing surface roughness. However, when the roughness factor exceeds a critical level, the contact angle continues to increase and the hysteresis begins to decrease. At this time, the main wetting behavior changes due to the increase in the amount of hydrophobic component (air in this case) at the interface between the surface and the water droplet. When multiple texture scales are used, some may be Wenzel, others Cassie. Of these two states, the Wenzel state has a lower contact angle, a higher contact angle hysteresis, and lower flowability. In the mixed Wenzel-Cassie regime, high contact angles and high contact angle hysteresis are possible. However, the hydrophobicity of the textured solid relative to the interacting hydrophobic and hydrophilic components is very important.

In the plant kingdom, most textured surfaces are present on hydrophobic substrates. However, the Cassie state can be easily converted to the Wenzel state when a hydrophobic fluid is substituted for water. This is not always the case and depends on the vapor pressure and viscosity of the hydrophobic material, and how quickly the air trapped in the surface texture can be dissipated.

Various attempts have been made to obtain hydrophobic coatings and surfaces, as described below: us patent No. 6,994,045 describes a superhydrophobic coating for use as a substrate for very low viscosity gas lubricants having a graded fractal structure of the surface, wherein a first graded level form is located on the substrate of the coating and each successive graded level form is located on the surface of the previous graded level and each higher graded level form repeats the lower graded level form. U.S. patent No. 7,419,615 discloses a method of forming a superhydrophobic material by mixing a hydrophobic material with soluble particles to form a mixture. Us patent No. 7,887,736 discloses a superhydrophobic surface repeatedly printed using a stencil, whereby mass production of superhydrophobic polymers over large areas can be economically achieved. U.S. publication No. 20030147932 discloses a self-cleaning or lotus effect surface with anti-fouling properties. U.S. publication No. 20060029808 discloses coatings that can remain superhydrophobic after one week of immersion in water. U.S. publication No. 20080015298 discloses a superhydrophobic coating composition. U.S. publication No. 20080241512 discloses a method of depositing layers of materials at different locations on a given surface to provide superhydrophilic or superhydrophobic surface properties or a combination of these properties. U.S. publication No. 20090011222 discloses methods of applying lotus effect materials as superhydrophobic protective coatings for various system applications, and methods of making/preparing lotus effect coatings. U.S. publication No. 20090076430 discloses a bandage comprising a breathable material having a first surface and a plurality of superhydrophobic particles attached to the first surface. The material may have a second surface opposite the hydrophilic first surface. U.S. publication No. 20090227164 discloses that a superhydrophobic coating of a nonwoven material is coated with a sponge network in the micro and nano range. U.S. publication No. 20100112286 discloses controlling and switching droplet states on artificially structured superhydrophobic surfaces. U.S. publication No. 20100021692 discloses a method of providing a multi-scale (graded) superhydrophobic surface. The method includes texturing a polymer surface in a fractal-like or pseudo-fractal-like manner in three size scales, the lowest scale being nanoscale and the highest scale being microscale. U.S. publication No. 20100028604 discloses a superhydrophobic structure comprising a substrate and a graded surface structure disposed on at least one surface of the substrate, wherein the graded surface structure comprises a microstructure comprising a plurality of micro-protrusions and depressions arranged in a spaced-apart geometric pattern on at least one surface of the substrate. U.S. publication No. 20110077172 discloses a method of locally depositing a material and includes a superhydrophobic substrate comprising a raised surface structure.

It is therefore an object of the present invention to provide low normal force retractors that produce an adherent Cassie and Wenzel state when placed in contact with wet living tissue.

SUMMARY

The present disclosure relates to low normal force retraction instruments that mechanically retract a surface or object by applying a low slip microtextured surface. In its simplest embodiment, the retraction instrument includes one or more arms, jaws, or tentacles for retracting an object. These features will be collectively referred to as "arms". In some cases, the arms are soft and flexible in the normal direction and substantially non-expandable in the tangential direction. In other embodiments, one or more of the arms may be rigid in order to provide a lifting or support function, such rigid arms will typically have a larger surface area to minimize the normal force per unit surface area during lifting or holding applications.

In other embodiments, the retraction instrument may be comprised of a single flexible arm having a micro-textured surface, particularly useful for surrounding an object to be retracted. Retracting in this case may include folding one part of the object over another part of the same object and maintaining the folded object in that configuration. When the retraction instrument is a single flexible arm, it may be further equipped with other fastening features, such as holes or hooks that may be used to anchor the arm to an external anchoring structure. These additional fastening features can be used to couple two or more single-arm retractors together. These additional fastening features may include, but are not limited to, lockable graspers, such as pliers or tweezers.

In the following description, the term "microtextured surface" will be used to denote a surface having a hierarchical structure comprising microstructures of various spatial dimensions which are superimposed to form a single surface having a texture on at least two spatial dimensions. In some embodiments, the microtextured surface comprises three, four or more spatial dimensions, preferably three or four spatial dimensions. Examples of microtextured surfaces that may be used in the present retractor include superhydrophobic surfaces similar to the texture of natural rose petals. Other examples include surfaces that have a contact hysteresis with living tissue of greater than 5 degrees. These surfaces are characterized by the creation of a Wenzel-Cassie interface when the microtextured surface is in contact with a moist or smooth surface. Other graded microtextured surfaces include surfaces similar to the texture of lotus leaf surfaces, where the interface is a Cassie-Baxter type interface.

The microtextured surface may comprise a mixture of the rose and lotus surface textures described above, some of which are rose-like and others of which are lotus-like, to obtain a "rose lotus" surface. The arm of the present invention may have a lotus surface on one side and a rose surface on the other side. In the following description, the term "normal force" will be used to refer to force per unit surface area, or pressure, where the force is normal or normal to the surface area. The surface area generally refers to the textured surface area of the microtextured arm and the normal force refers to the force applied normal to the textured surface of the arm by contact with the object to be retracted. Thus, the normal force can generally be reduced by increasing the surface area of the arms. In some cases, it may be useful to be able to vary the surface area of the microtextured arms. Thus, the arm may have a corrugated structure that may be made with smaller corrugations to increase the surface area of the arm. Other retractors include expansion or dilation of the arms. In other embodiments, the area-increasing region is decoupled from microstructured regions in which the spatial dimensions of the microstructures are not altered by the effect of increasing the surface area of the arms. The expansion aspect may be used to change the rigidity of the microtextured arms, or to change their morphology. For example, the expansion of the two microstructured arms may be configured to produce a jaw movement, providing a change in the applied normal force.

In accordance with various aspects of the present invention, the microtextured retraction instrument according to the present invention maintains its ability to provide retraction in different ways while providing access to the object to be treated or viewed for other instruments. Microtextured retraction instruments according to one aspect of the invention (such retraction instruments are commonly designated as type I retraction instruments) provide retraction only by the Wenzel-Cassie action, where the microtextured surface naturally attaches itself to a wet surface by hydrophobic interaction. Type I devices typically have fixed mechanical properties such as elasticity, stiffness, modulus, and the like. Type II instruments include ancillary components for altering these characteristics and the relationship between the arms. For example, one arm may be stiffened or both arms may be in a preferred orientation by expansion. Expansion includes gas and liquid expansion. In gas expansion, the pressure is controlled, while in liquid expansion, the volume is controlled. Composite expanded structures are possible. The first expansion chamber may be formed between two opposing surfaces of the tubular microtextured arm, wherein a bridging structure between the opposing surfaces maintains the generally planar strip microtextured arm under expansion. Additional inflatable chambers form an inner smaller tubular structure within the first chamber of the microtextured arm. Under expansion, the second chamber may provide a preferred curved configuration for the microtextured arms. The second inflatable chamber is typically inflated after the main inflatable chamber of the retraction instrument has been inflated and the retraction instrument has produced its desired retraction effect. Such additional inflatable chambers are smaller and less powerful than the main inflatable chamber. Inflating this additional chamber alone does not always produce sufficient force to provide the desired retraction of the organ. However, the inflated additional chamber provides sufficient force to maintain the object retracted by the more powerful main inflatable chamber in its retracted position. Thus, the additional inflatable chamber is able to maintain the retracting effect of the retracting instrument after the retracting effect of the main inflatable chamber has been disrupted by perforating the envelope of the main chamber to provide access to the object to be treated.

According to another aspect of the invention, a type I or type II retraction instrument according to the invention may be provided with tabs attached to the surface of the microtextured arms of the instrument. The tabs are grasped with a suitable grasping tool to adjust the position and orientation of the retraction instrument relative to the tissue to be treated.

In accordance with another aspect of the present invention, a type I or type II retracting instrument, when in its first state prior to actuation, may be provided with indicia on its surface to aid in proper orientation prior to actuation, or may be provided with similar indicia for indicating areas of different surface texture. In accordance with another aspect of the invention, a type I or type II retractor instrument may have a corrugated surface, wherein one configuration of the corrugations provides an adhesive Wenzel-Cassie surface and in another configuration of the corrugations provides a low friction Cassie-Baxter surface. This feature can be used to release retracted objects in a manner that reduces potential damage to the object if release is attempted in a Wenzel-Cassie state. For example, a type I instrument can be in a first, attached state and then rendered non-attached by irreversibly deforming the microstructured arms by applying a tangential stretching motion to the microtextured arms. In type II devices, the same effect can be reversibly achieved by expansion.

According to another aspect of the invention, in the retracting instrument according to the invention, the arm may incorporate a suction tube for removing free liquid at the retracting site. Alternatively, the microstructured arm may be equipped with an attachment for such a suction tube. In the case of retraction during surgery, the suction side is connected to the operating room suction line and allows continuous or intermittent drainage of the fluids collected at the bottom of the operating cavity created by the retraction instrument during laparoscopic surgery.

Brief description of the drawings

FIG. 1 is a cross-sectional view of a superhydrophobic Wenzel-Cassie surface embodiment of the invention;

figure 2 is a perspective view of a band type II inflatable retraction instrument according to a second embodiment of the present invention;

figure 3 is a perspective view of a type I retracting instrument fitted with a suction device according to a third embodiment of the present invention.

Figure 4 depicts a microstructured surface that can be used in a low normal force retractor.

Figure 5 depicts a first embodiment of a low normal force retractor surface.

Fig. 6 depicts a second embodiment having a reverse side.

Fig. 7A-7D depict a selection of substrates 710 having various sinusoidal wave shaped patterns that provide alternative curved surface texture features across the substrate 710.

Fig. 8 depicts a side view of an embodiment of a microstructured surface on a substrate having a second set of features disposed on the surface of the substrate according to the present disclosure.

Fig. 9 depicts a side view of another embodiment of a microstructured surface on a thin substrate according to the present disclosure.

Fig. 10 depicts a perspective view of a microstructured surface having a fourth set of micro features.

Fig. 11 depicts a schematic top view of a microstructured surface having a fourth set of micro features.

Fig. 12 is a perspective view of a hybrid rose lotus type I retractor instrument according to another embodiment of the invention.

Fig. 13 is a perspective view of a ripple II retractor instrument according to another embodiment of the present invention.

Fig. 14 is a perspective view of a type II retracting instrument with an area change according to another embodiment of the present invention. The device 1400 has a surface texture 1414 and may be in two configurations 1410 and 1412. Configuration 1410 is a flat configuration with the largest surface area in contact with the flat surface, and configuration 1612 is an expanded configuration with the smallest surface area. Thus, when in configuration 1710, the instrument 1700 is adhesive and when in configuration 1412, it slides more easily. The expansion member 1416 causes the device 1400 to transition to the configuration 1412 upon pressurization.

Fig. 15 is a side view of a hybrid area changing type I retracting instrument 1500 according to a sixth embodiment of the present invention, wherein textured area 1514 is constant. The instrument 1500 assumes two bi-stable configurations 1510 and 1512. In configuration 1510, the rose petal texture 1514 is the only surface provided to the other surface to which the instrument 1500 is to be attached. The contact surface area in configuration 1510 is the sum of the area of 1514. Region 1516 is smooth and the area of feature 1512 is greater than the area of feature 1510. The area of the configuration 1512 is the sum of the regions 1514 and 1516. Configuration 1512 is achieved by pulling configuration 1510 in direction 1518.

Fig. 16 is a perspective view of a jaw movement type II retraction instrument 1600 in accordance with a seventh embodiment of the present invention. The instrument 1600 has a relaxed compliant state 1610 and a rigid clamped state 1612. The transition from state 1610 to state 1612 is achieved by expansion device 1616. Feature 1614 includes a rose petal attachment surface.

Fig. 17 depicts a retractor comprising an arm having a micro-textured surface of the present disclosure disposed on a portion thereof.

Detailed Description

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. At least one embodiment of the invention will be described and illustrated, and other embodiments of the invention may be shown and/or described herein. It is to be understood that any reference to "the invention" is a reference to a class of embodiments of the invention and that no single embodiment includes apparatus, methods or compositions necessarily included in all embodiments unless specifically stated otherwise.

I-type equipment

Fig. 1 illustrates a vertical view of a first embodiment 100 of a retraction instrument according to the present invention. This type of retraction instrument is substantially fixed in its mechanical and geometric aspects and will be designated as a type I retraction instrument. The retraction instrument is shown in its flat condition and it will be understood that the instrument is sufficiently flexible to enable it to conform to the surface of the object to be retracted. The retraction instrument 100 includes a first side 102 and a second side 104. The retraction instrument 100 is made from a relatively inelastic and tough film of plastic such as polypropylene, polyethylene, or polyurethane. The preferred material is a polyethylene and nylon composite. The retraction instrument 100 is typically 0.5 to 5mm thick. The surface texture 106 includes large-scale structures 108, intermediate-scale structures 110, and micro-scale structures 112. The micro-scale structures 112 are superimposed on the intermediate-scale structures 110, and the combination is superimposed on the large-scale structures 108. The large scale structures 108 have a feature size of 100 to 1000 microns. The mesoscale structures 110 have a feature size of 25 to 100 microns. The micro-scale structures 112 have a feature size of 1 to 25 microns.

Generally, the size and shape of the retraction instrument depends on the application. For example, in surgical applications, a retraction instrument according to the present invention may be sized in the range of about 2"(50mm) long by about 0.5" (12mm) wide for use within the pericardium to 10"14" (250-350 mm) long by 2"8" (50-200 mm) wide for use within the abdominal cavity. The size of the retraction instrument required for a given application depends on the application and the size of the patient.

Type II retractor

A basic embodiment of a type II retracting instrument includes a single inflation chamber. In alternative embodiments, a single chamber may be divided into multiple sub-chambers. These compartments are isolated from each other so that if one or more of them is accidentally punctured when the retraction instrument is used, total deflation of the retraction instrument can be avoided. Each subchamber may be provided with its own additional expansion tube. Alternatively, each subchamber may be connected to the expansion manifold by a check valve. This manifold arrangement requires that each compartment be separately deflated in preparation for the retraction instrument to be withdrawn from the body at the end of the procedure. The main advantage of these interconnected or separate compartments is that they define a preferred geometry under expansion.

Fig. 2 is a perspective view of a type II device 200 having multiple expansion chambers. The main housing 202 is made of a relatively inelastic and tough film of plastic such as polypropylene, polyethylene, or polyurethane. The preferred material for the main housing is a polyethylene and nylon composite. The wall thickness 204 of the main housing 202 is typically 0.5 to 5 mils (13 to 130 microns). When expanded, microstructured arm 200 has an instrument thickness 206 of 1mm to 5 mm. The instrument thickness 206 is limited by the height 210 of the inelastic member 208 forming each compartment 212. Subchamber 212 extends to manifold 214. Air or liquid pressure is delivered by tube 216. The delivery tube 216 may be a small and flexible tube having a diameter 218 in the range of 1mm to 5 mm. The main expansion tube 216 allows expansion gas to enter and exit the subchamber 212. The expansion gas is typically air, nitrogen or carbon dioxide, but other suitable gases may be used. The inflation fluid is typically saline. Typical inflation gas pressures are in the range of 0.3 to 0.7psi (0.21 to 0.48Pa), with a preferred pressure of 0.5psi (0.35 kPa). Once the instrument 200 is fully inflated, the inflation gas pressure may be reduced to about 0.3psi (0.21 kPa).

Additional features of type I and type II instruments

Suction aspect

According to another aspect of the invention, the retracting instrument according to the invention may be equipped with a tubular suction portion on the lowermost portion of the retracting instrument when the retracting instrument is arranged in the cavity with the presence of a liquid. Figure 3 shows a type I instrument with suction features attached. The suction portion of this aspect of the invention may be used with both type I and type II retraction instruments. Irrigation is commonly used when retraction is applied to a cavity environment. Flushing is used to remove debris. In the case of surgical applications, the debris consists of blood and coagulated components. This fluid collects at the bottom of the body cavity created by the retracting instrument and needs to be removed. Suction portion 302 is integral with microstructured retractor 300. The bottom of the retraction instrument 300 is connected to a suction line 302 and this fluid is removed during the treatment procedure, thereby keeping the cavity free of accumulated fluid. In the example shown, the suction portion 302 is a tubular attachment attached to the lowermost end of the retraction instrument. The suction portion may be made of a polyethylene nylon composite, which is a preferred material for the body of the retraction instrument. Such materials are sufficiently resilient that the tubular structure made therefrom can maintain its open cross-section under a low vacuum. The suction portion 302 is closed at one end; the other end is connected to a thin walled polyethylene tube 304, which thin walled polyethylene tube 304 extends up the side of the retraction instrument to exit the body through the same incision through which the retraction instrument is delivered. Suction is delivered to the surgical site through the holes 306.

Curved retractor instrument

The curvature may be formed in a ribbon-like microstructured retractor arm. For example, the curvature may have a radius of curvature that is significantly less than the length of the retractor, such that the arms curl themselves at least 1 time when in a relaxed state. The radius of curvature preformed and the stiffness of the material used determine the normal force when the object enclosed in the retractor is larger than the radius of curvature. In most cases, the normal force is proportional to the ratio of the diameter of the object to the radius of curvature of the retractor.

Referring to fig. 4, the surface of the low normal force retractor surface 400 of the present invention generally has a graded surface comprising a large scale structure 402 with a plurality of protrusions 404 and depressions 406 arranged in a geometric pattern on at least one surface of a substrate 408, and a medium scale structure 410 disposed on at least one surface of the large scale horizontal structure 402 comprising protrusions 412. The small-scale structures 414 similarly include protrusions 416 and recesses 418 disposed on the medium-scale structures 410. The large-scale protrusions 404 should be high enough so that the hydrophilic component of the hydrophobic/hydrophilic contact mixture does not contact the large-scale depressions between adjacent protrusions 404. In the embodiment of fig. 4, the large-scale protrusions 404 may comprise a height H of about 25 to about 1000 microns and a diameter D of about 25 to about 2000 microns, wherein the surface area fraction of the substrate 408 covered by the protrusions 404 may be about 0.1 to about 1.0. The mesoscale protrusions 412 may comprise a height 420 of 5 to about 25 microns and a diameter 422 of 5 to about 50 microns, wherein the surface area fraction of the substrate 408 covered by the protrusions 412 may be about 0.1 to about 0.9. The small-scale structures 414 may be disposed primarily on the medium-scale structures 412. The arrangement of the hierarchy may be geometric and may be described generally by mathematical equations. Alternatively, the hierarchical structure may be randomly arranged, possibly with varying pitch (pitch), which is more typical for natural structures. The arrangement of the hierarchy can be described in general by the fractal dimension.

The fractal dimension is a statistic that shows how completely a collection of structures shows how completely a space (a plane in the present case) is filled when the structures are examined on multiple spatial scales. Specifying a fractal dimension with statistical properties does not necessarily mean that the hierarchy is well defined by mathematical equations. Generally, a random arrangement of structures within a certain scale has a higher fractal dimension than an arrangement in which the structures are mathematically described at all points on the surface. Thus, random structures may be advantageous in that the adherent surfaces of the invention have greater efficacy when interacting with natural surfaces. Higher fractal dimensions within a particular spatial scale may be achieved by applying a multi-pitch arrangement to the substrate. The protrusions and depressions may be locally scaled with respect to the local pitch. Thus, the pitch may vary within the scale structure. In a practical implementation of a higher fractal dimension structure, the variation in pitch can be described by a mathematical equation, such as a sinusoidal variation in pitch, which has the effect of simulating a natural surface.

In general, structures can be described as sharp-edged or rounded, and the features are not typically obtained by fractal dimensions. Another structural aspect not addressed by the above descriptive parameters is the degree of communication between the structures. By connected is meant that structures such as protrusions or depressions have a spatial extent greater than the pitch. For example, a valley surrounding a protrusion may be connected to another valley surrounding another protrusion, so that a depression is said to be connected, while a protrusion is not. The communication can range from 1 to about 1000, and more specifically, the communication can extend over the entire surface of the substrate. These structures are constructed to create Wenzel and Cassie states on multiple scales when the low normal force retractors of the invention are contacted with a hydrophobic/hydrophilic contact mixture.

The scale of interaction is defined by the surface texture of the low normal force retractors of the invention and is typically graded and characterized by at least two spatial scales, one on the order of micrometers (microns) and the other on the order of hundreds of microns. The surface texture may cause one state with a large difference between advancing and receding contact angles (contact angle hysteresis) or another state with a small contact angle hysteresis. The states of interest are referred to as the Wenzel state and the Cassie state, respectively. Each hierarchical spatial scale can induce Wenzel or Cassie states separately, such that combinations can be made on multiple spatial scales.

These states are phenomena between the hydrophobic and hydrophilic components of the mixture that reside at the textured surface interface. In the Cassie state, the attached fabric is resistant to attachment of hydrophobic debris, such as oil in an oil-water mixture. In the Wenzel state, the implant reversibly attaches to a hydrophilic surface, such as a wet or ice surface. In a mixed Cassie-Wenzel state, where one texture scale is Wenzel and the other is Cassie, the retractor can be positioned on wet surfaces as well as resistant to hydrophobic contaminants, such as fat.

The Cassie-Baxter model describes the interaction of solid textured surfaces with water in a gaseous environment. In this model, air is trapped in the microgrooves of the textured surface and water droplets settle on the composite surface including the air and the tops of the microprotrusions. The importance of fractal dimension (fractional dimension) between multiple texture scales (scales) is well recognized and many methods are based on fractal contribution, i.e. the dimensional relationship between textures of different scales.

However, regardless of the materials used (organic or inorganic) and the geometry of the surface texture (particles, rod arrays or pores), multiple texture scales combined with low surface energy are required to obtain a so-called superhydrophobic surface. Superhydrophobicity is variously reported as a material that exhibits a contact angle with water that is greater than that achievable with a smooth but strongly hydrophobic material. The general consensus on the minimum contact angle for superhydrophobic materials is 150 degrees, so in this context, some embodiments of the invention are not strictly superhydrophobic, although this option is not excluded. The reason for this is that the Wenzel-Cassie state is the hydrophobicity between its non-textured surface and the surface that creates the Cassie-Baxter interface. Superhydrophobicity is only one aspect of many interesting texture control mechanisms in optimizing the adhesion of the fabrics of the invention, in which context the contact angle is less important than the contact angle hysteresis.

It is known in the art that the transition to the Wenzel state can be prevented by using sharp-angled features in the surface plane. However, the appearance of sharp-angled structures in natural structures such as rose petals is less common. Natural structures tend to have rounded surface features, particularly radiused or filleted corners. In nature, resistance to transition to the Wenzel state appears to involve the rounded structure that produces the involutes rather than sharp edges. By inward-rolling is meant concavity oriented in a line non-orthogonal to the substrate surface. Such structures are difficult to produce by etching or casting methods, but can be easily produced by embossing methods that bring about folding of the structure.

Similarly, the Wenzel regime can be prevented by using curved rather than straight line communication between structures. In most cases, higher hydrophobicity equates to lower Wenzel conversion propensity. By placing an external corner around the depression, the hydrophobicity of the surface is enhanced. In some embodiments, this is achieved by creating additional pairs of adjacent recess walls that extend into the interior of the recess and are connected thereto. In some embodiments, this is accomplished by designing an ordered array of first graded depressions (e.g., triangular, rectangular, pentagonal, or hexagonal, regular or irregular; and other polygonal shapes generally defined by straight line segments).

Second features of smaller size and different grading order are then superimposed on the recessed walls of the first pattern. The method for fabricating such structures may comprise first imprinting the large-scale structures and then second imprinting additional smaller-scale structures, preferably smaller-scale structures, onto the larger-scale structures.

Water has a dipole structure, making it attractive to any other charged species. Molecules with an excess of charge localized at a particular location on the molecule render the molecule hydrophilic. In the case of polymers, the charges may associate and a large number of species have macroscopic charges. In such macroscopic combinations, such materials strongly attract water. When those macroscopic charge sites are associated with the surface texture, then the substance becomes superhydrophilic. The term superhydrophilic has various meanings in the literature and in many cases simply refers to making a substance more hydrophilic or reducing the contact angle relative to a flat surface of the same substance. Here, this means an increase in surface charge and surface energy, so that water always binds to the substrate surface, even though any particular water molecule may have a short residence time on the polymer surface. This is commercially advantageous because the attachment surface of the low normal force retractor both protects from contaminating debris and is self-cleaning due to the random attachment/detachment of water molecules to the surface. Methods of manufacturing textured surface low normal force retractors of the invention include any of several methods of photolithography, casting, extrusion/embossing, and transferring texture to a surface. Methods for forming such graded microstructured surfaces are described in U.S. application No. 14/802,632, which is incorporated herein by reference in its entirety.

A preferred method is embossing, wherein the polymeric substance is heated to a molten state and passed through two rollers, wherein at least one roller contains a negative image of the desired embossed structure. Small scale textures are imprinted on the planar sheet. This embossed planar sheet is heated to a malleable but non-flowing state and passed through a twin roller having a mesoscale texture which prints the inverse image. This process may be repeated multiple times. The mesoscale texture is large relative to the small-scale texture, so the impression of the mesoscale texture overlaps the small-scale texture, making it possible to form an inner wrap structure that is not normally possible with lithographic or casting methods.

The low normal force retractors of the invention have three or more levels of texture assembled in a manner that creates a high surface area while maintaining a minimum spacing between the textures to allow liquid flow and penetration to promote surface cleaning first and surface attachment second; while maintaining a minimum structural strength that is obtained by keeping the aspect ratio of all features below a critical level (which exceeds the material strength).

Referring to fig. 5, there is shown a first embodiment of a low normal force retractor arrangement 500 on a fabric surface according to the present invention comprising a substrate generally designated 510. In the embodiment shown, the substrate 510 has a sinusoidal waveform including a series of rounded peaks and valleys that create a continuous curved surface over at least a portion of the substrate 510. The sinusoidal waveform of the substrate 510 defines a first set of macro-scale features, generally designated 512, with a second set of micro-features 514 disposed on the macro-scale features.

In FIG. 5, substrate 510 is constructed and arranged to be concentrated on a series of rounded knobs forming peaks 515 projecting upwardly from the surface with associated valleys 517 disposed between the peaks 515.

In a second embodiment shown in fig. 6, the opposite arrangement is shown, wherein the substrate 610 is constructed and arranged to be centered over a series of circular cavities, forming valleys 617 extending inwardly into the substrate 610 as the primary features, with associated peaks 615 disposed between the valleys 617, 614 representing a second set of micro-features. In both embodiments, the surface of the substrate 610 is continuously curved throughout the sinusoidal wave pattern area.

According to the present invention, the term sinusoidal waveform as used herein refers to a surface having a repeating oscillation of circular non-flat curvature described by a mathematical formula combining trigonometric functions sine, cosine, tangent, or exponential and power series functions. These mathematical formulas are used in computer aided design and computer aided manufacturing software to create textured surfaces using rapid prototyping, milling, electro-discharge machining or similar techniques to create polymer or metal surfaces with sinusoidal wave shaped texture features. The benefit of using mathematical formulas is that a large number of circular non-flat features can be generated quickly in computer-aided design and computer-aided manufacturing software. This type of texture feature cannot be created using photolithographic techniques.

Referring to fig. 7A-7D, an alternative to a substrate 710 having various sinusoidal wave shaped patterns that provide optional curved surface texture features across the substrate 710 is shown. These embodiments are merely illustrative of exemplary embodiments of the substrate 710 and do not limit the invention and the term sinusoidal waveform used herein. According to the present invention, the first set of textural features 712 includes dimensions selected from sizes in the range of about 100 microns to about 1000 microns. More specifically, as will be described in detail below, in a preferred embodiment, the sinusoidal waveform is configured such that the first set of textural features 712 have sinusoidal circular cavities of 750 microns, a pitch of 750 microns, and a depth of about 240 to 500 microns. This arrangement of the substrate is intended to promote the adhesive Wenzel-Cassie state of the hydrophobic/hydrophilic contact mixture. Referring to fig. 8 and 9, a second set of textural features 814 and 914 is disposed on the surface of substrates 810 and 910. In one embodiment, the second set of textural features 814 is molded onto the first set of textural features 812 and 912 of substrates 810 and 910, respectively. As described in detail below, in a preferred embodiment, the substrate 810 or 910 is a compression molded polymeric material, wherein the first and second sets of textural features 812, 814 and 912, 914 are formed on the substrate 810 and 910, respectively, during a single molding step. The first and second sets of textural features 812, 814 cooperate to increase surface area and affect at least one of adhesion, friction, hydrophilicity, and hydrophobicity of the substrates 810 and 910. Preferably, the compression molded polymeric material forming the substrate 810 is an environmentally durable polymer. In one embodiment, the substrate 810 or 910 includes a polyethylene nylon copolymer. In the embodiment shown, the second set of microstructures 814 or 914 is selected from the group consisting of microstructured projections and microstructured cavities and combinations thereof. In the embodiment shown in fig. 6, the second set of textural features 614 comprises microstructured cavities extending down into the substrate 610.

In the embodiment shown in fig. 8-11, second set of textural features 814, 914, 1014, and 1114 comprise microstructured projections extending upwardly from substrates 810, 910, 1010, and 110, respectively. Preferably, in the embodiment shown in fig. 8-11, the microstructured projections of the second set of textural features 814, 914, 1014 and 1114 comprise substantially cylindrical posts.

Preferably, in the embodiment shown in FIG. 6, the microstructured cavities of the second set of textural features 614 comprise substantially cylindrical depressions.

Referring to fig. 9, in one embodiment in which the substrate 910 is a thin film substrate and has operably opposing top and bottom surfaces, the first set of textural features 912 disposed on the top surface 921 of the substrate 910 form complementary shapes on the bottom surface 923 of the substrate 910 such that rounded peaks on the top surface 921 form rounded valleys on the bottom surface 923 and rounded valleys on the top surface 921 form rounded peaks on the bottom surface 923.

Referring again to fig. 9, in embodiments where the substrate 910 is a thin film substrate and has operably opposing top and bottom surfaces, the second set of textural features 914 comprises a series of microstructured projections on one of the top surface 921 and the bottom surface 923 of the substrate 910, which then define a series of complementary microstructured cavities on the other of the top surface and the bottom surface 921,923.

Similarly, in embodiments where the second set of textural features 914 comprises microstructured cavities projecting downward from the top surface 921 through the substrate 910, they form complementary microstructured projections on opposing bottoms.

Referring to fig. 5, 8 and 9, in the illustrated embodiment, the second set of textural features 514, 814 and 914 includes at least a portion of the textural features extending along an axis normal to the curve of the sinusoidal waveform of the substrates 510, 810 and 910 at a given point of the individual microstructures. In this manner, the second set of textural features follows the curvature of the first set of textural features 512, 812 and 912.

According to the present invention, the second set of textural features comprises dimensions selected from sizes in the range of about 10 microns to about 100 microns. Furthermore, the second set of textural features preferably has a height to width aspect ratio of less than 5, and a minimum spacing of 1 micron between each textural feature of said second set of textural features to maintain structural strength while allowing liquid flow and penetration between individual microstructures comprising the second set of textural features.

Referring again to fig. 8-11, a third set of textural features 820, 920, 1020 and 1120 may also be disposed on substrates 810, 910, 1010 and 1110, respectively. Preferably, the third set of textural features 820 is selected from the group consisting of microstructured projections and microstructured cavities and combinations thereof. In one embodiment, the microstructured projections of the third set of textural features 820, 920, 1020 and 1120 comprise generally cylindrical posts.

Referring to fig. 6, in one embodiment, the microstructured cavities of the third set of textural features 620 comprise generally cylindrical depressions. Preferably, the third set of textural features 620 is compression molded simultaneously with the first and second sets of textural features 612, 614. In another preferred embodiment, third set of textural features 620 has a height to width aspect ratio of less than 5 and a minimum spacing of 1 micron between each textural feature of third set of textural features 620 to maintain structural strength while allowing liquid flow and penetration between said third set of textural features. The aspect ratio is small when the instrument is made of a lower strength material and large when the instrument is made of a stronger material. The spacing between features is smaller for less viscous liquids and larger for more viscous liquids.

Referring to fig. 5, 8, and 9, the third set of textural features 520, 820, and 920 includes at least a portion of textural features extending along an axis normal to the curve of the sinusoidal waveform of the substrate 10. For the purposes of the present invention in which the second and third sets of textural features extend along axes normal to the sinusoidal wave profile, the normal to the profile is a line perpendicular to the tangent of the profile at a particular point. In the illustrated embodiment, the second set of textural features 514, 814 and 914 is smaller than the first set of textural features 512, 812 and 912, respectively, and the third set of textural features 520, 820 and 920 is smaller than the second set of textural features 514, 814 and 914, respectively. According to the present invention, the third set of textural features comprises dimensions selected from a size in the range of about 1 micron to about 10.

Referring to fig. 5 and 8-11, in one embodiment, a third set of textural features 520, 820, and 920 is disposed on end surfaces 522, 822, and 922 of second set of textural features 514, 814, and 914. In another advantageous embodiment, a third set of textural features 520, 820 and 920 is disposed on the first set of textural features 12 between the second set of textural features 14. In another advantageous embodiment, a third set of textural features 20 is disposed on the end surface 22 of the second set of textural features 14 and on the first set of textural features 12 between the second set of textural features 14, 30.

Referring to fig. 10 and 11, a fourth set of textural features 1024 and 1124 may be disposed on the side surfaces of the second set of textural features 1014 and 1114, respectively. The fourth set of textural features 1024 and 1124 are selected from the group consisting of grooves 1016,1116 and ribs 1018,1118 and combinations thereof. In the embodiment shown, the grooves (1016,1116) and ribs (1018,1118) extend vertically along the height of the side surface on the periphery of each microstructure that includes the second set of textural features (1014,1114). The fourth set of textural features preferably comprises dimensions selected from sizes in the range of about 1 micron to about 10 microns. Preferably, fourth set of textural features 1024 and 1124 are compression molded into substrate 1010,1110 at the same time as the first, second and third sets of textural features.

Preferably, grooves and/or ribs (1016,1018,1116,1118) having features and spacing greater than 1 micron are added to the exterior of the cylindrical posts or cavities defining the second set of textural features (1014,1114), thereby increasing surface area and increasing structural resistance to bending and fracture. The spacing between individual microstructures of the fourth set of textural features 1024,1124 and between individual microstructures of the second set of textural features (1014,1114) is smaller for lower viscosity liquids and larger for higher viscosity liquids.

The third set of textural features (1020,1120) covers the tops of the pillars and the bottoms of the cavities and the areas between the pillars or cavities defining the second set of textural features 1314 in a substantially uniform manner. The second and third sets of textural features (1014,1114), (1020,1120) together significantly increase the surface area of the liquid exposed to the opposing surface of the cover substrate. Depending on the desired application, the first, second, third, and fourth sets of texture features cooperate to increase the surface area of the substrate (1010,1110) to achieve at least one of adhesion, friction, hydrophilicity, and hydrophobicity of the substrate. In one embodiment, the substrate (1010,1110) has a surface attachment with a sliding friction force greater than 50 gr/cm2 when applied against a surface comprising a hydrophobic/hydrophilic mixture. In a preferred embodiment, the substrate (1010,1110) has a surface attachment with a sliding friction of about 325 gr/cm2 when applied against a surface comprising a hydrophobic/hydrophilic mixture.

In earlier studies, the inventors characterized the rose petal structure and observed a "sloppy" effect in the microstructure. Furthermore, the smaller microstructure is called "hair", which seems to strongly contribute to the superhydrophobic effect. To best simulate this scenario, the inventors have produced a sinusoidal design as described herein that can reproduce and improve the circular microstructure effects seen naturally, starting from a sinusoidal waveform substrate characterized by a 300 micron diameter and 100 micron pitch.

The dimensions of the third set of textural features (1020,1120) in one embodiment include pillars having a diameter of 3 microns, a pitch of 6 microns, and a height of 5 microns. In one embodiment, the second set of textural features (1014,1114) comprises grooved microstructure pillars having a diameter of at least 35 microns, a height of 35 microns and a pitch of 10 microns. When overlapped together, the second and third sets of micro-features (1014,1114,1020,1120) are formed along axes normal to the surface of the sinusoidal wave features. These are also maintained on the circle in multiple dimensions.

To improve the superhydrophobicity effect of rose petals found in nature, the second set of textural features (1014,1114) adds "grooves" or "ribs" features extending along the side surfaces. These grooves and rib-like features defining a fourth set of textural features (1024,1124) mimic the smaller hair-like microstructure of rose petals to further promote hydrophobicity. Thus, each microstructure in the first, second, third and fourth sets of textural features has a respective pitch, height/depth and diameter, and is arranged such that when used to cover a surface with a liquid, the liquid penetrates between at least the first and second sets of textural features in a Wenzel fully wetted state to promote adhesion between a substrate and an adjacent surface. Preferably, the sinusoidal wave shape of the first set of textural features comprises rounded peaks, which facilitate the distribution of pressure across the substrate when pressed against the liquid covered surface.

Preferably, the second and third sets (1014,1020,1114,1120) of textural features are evenly distributed across the circular peaks of the first set of textural features to provide increased surface area to the first set of textural features. When the substrate is used with a liquid-covered surface, the rounded peaks define areas of increased pressure that promote the transition of the droplets from the suspended Cassie-Baxter state to the Wenzel fully wetted state between at least the first and second sets of texture features. In a preferred embodiment, the first, second, and third sets (1012,1112,1112,1114) of texture features allow liquid penetration to Wenzel's fully wetted state, while the fourth set (1024,1124) of texture features is constructed and arranged to retain superhydrophobic properties.

The function of the second and third sets of textural features is to create a large surface area while the spacing is wide enough so that viscous liquid can flow through the structure at low pressure. The low pressure in this application is defined in the context of the weight associated with the droplets being sufficient to create a Wenzel fully wetted state to promote adhesion of the substrate 10 to the adjacent liquid covered surface. Thus, the microstructured surface of the present invention was designed to facilitate the transition from the Cassie-Baxter suspended droplet state to the Wenzel fully wetted state with water droplets having a size greater than 10 texture liters.

One function of the sinusoidal waveform of the first set of textural features is to further increase the surface area while creating areas of increased pressure at the peaks of the features. These areas of increased surface area wet first, resulting in a rapid transition from the Cassie-Baxter suspension droplet state to the Wenzel fully wetted state. The second function of the sinusoidal waveform of the first set of texture features is to keep the peak pressure low enough and spread the pressure so that little or no penetration through the liquid layer on the surface into the underlying material occurs. The second and third sets of textural features are evenly distributed on the sinusoidal waveform of the first set of textural features and normal to the surface curve. That is, they are perpendicular to the surface tangent of each point of the microstructure on the surface. This ensures that the maximum surface area is created in the structure that can be molded.

Detailed description of the preferred embodiments

Rose lotus I type

Figure 12 is a perspective view of a hybrid rose lotus type I retractor instrument according to a third embodiment of the invention. The instrument 1200 includes a rose textured side 1210 and a lotus textured side 1212. The rose texture 1210 is characterized by the geometry of the water droplets 1214, where the water droplets 1214 are characterized by a spherical 1216 shape of the superhydrophobic surface. Due to the wicking geometry 1218, the water droplets 1214 are immobilized on the surface 1210. The lotus texture 1212 is characterized by the geometry of the water droplet 1220, where the shape is spherical, without a wicking structure similar to the feature 1518. Water droplets 1220 resist adhesion to surface 1212 and roll off the surface easily.

Wave II type

Figure 13 is a side view of a ripple II retractor instrument according to a fourth embodiment of the present invention. It should be understood that a manually driven type I mode is also possible. The device 1300 may be in two configurations 1310 and 1312. Configuration 1310 is a rose-grain configuration and configuration 1312 is a lotus-grain configuration. Thus, when in configuration 1610, device 1300 is adhesive and when in configuration 1312, it slides easily. The instrument 1300 in the corrugated state 1310 has a first structure 1314 and a second structure 1316. Expansion member 1320 causes instrument 1600 to move in direction 1318 to transition to configuration 1312 when pressurized.

Type II with altered surface area

Fig. 14 is a perspective view of a type II retracting instrument with an area change according to a fifth embodiment of the present invention. The instrument 1400 has a surface texture 1314 and can be in two configurations 1310 and 1312. Configuration 1310 is a flat configuration with the largest surface area in contact with a flat surface, and configuration 1612 is an expanded configuration with the smallest surface area. Thus, when in configuration 1310, instrument 1300 is adhesive and when in configuration 1312, it slides more easily. When pressurized, the expansion member 1316 transitions the device 1300 to the configuration 1312.

Type I with changed area

Fig. 15 is a side view of a hybrid area changing type I retraction instrument 1500 according to a sixth embodiment of the present invention wherein the textured area 1514 is constant. The instrument 1500 assumes two bi-stable configurations 1510 and 1512. In configuration 1510, the rose petal texture 1514 is the only surface provided to the other surface to which the instrument 1500 is to be attached. The contact surface area in configuration 1510 is the sum of the area of 1514. Region 1516 is smooth and the area of feature 1512 is greater than the area of feature 1510. The area of the configuration 1512 is the sum of the regions 1514 and 1516. Configuration 1512 is achieved by pulling configuration 1510 in direction 1518.

Clamp type II

Fig. 16 is a perspective view of a jaw movement type II retraction instrument 1600 in accordance with a seventh embodiment of the present invention. The instrument 1600 has a relaxed compliant state 1610 and a rigid clamped state 1612. The transition from state 1610 to state 1612 is achieved by an expansion member 1616. Feature 1614 includes a rose petal attachment surface.

Fig. 17 depicts a retractor 1701 that includes arms 1703 and surgical anchors 1705. Surgical anchor 1705 enables the surgeon to anchor retractor 1701 to the perioperative surgical dressing. The proximal end 1707 of retractor 1701 has a superhydrophobic surface 1019. Detailed examples of superhydrophobic surfaces are depicted and described above. Optionally, the retractor may comprise an expansion member 1711, the expansion member 1711 comprising a hollow portion 1713 that may be pressurized via a tube 1715. As depicted, when the hollow portion 1713 is expanded, the retractor becomes rigid and straight along direction 1717. Optionally, the retractor can include a suction balloon that includes a series of holes 1719 that provide access to the internal suction volume 1723 from the tissue contacting side 1721. The suction balloon includes a tissue contacting side 1721 and a lateral side 1725. The outer side 1725 can have a tab 1726 to which a surgeon can suture an indwelling wire to the tab 1726 or grasp the tab 1726 to position the retractor 1 relative to a tissue surface. A suction tube 1727 attached to the suction balloon provides suction and draws tissue fluid 1729 into the suction balloon. Optionally, retractor 1 may have a pre-formed shape such that width 1731 is straight and length 1733 is curved and has radius of curvature 1735. Optionally, retractor 1701 has a corrugated 37 tissue contacting surface 1721. The corrugation frequency 1739 may be adjusted by the expansion member 1711 such that increased expansion decreases the frequency 1739 and increases the length 1733.

All references cited herein are incorporated by reference in their entirety.

Claims (16)

1. A microstructured retractor comprising at least one arm having a superhydrophobic surface comprising at least one of a Wenzel-Cassie surface, a Cassie-Baxter surface, or a combination of these surfaces, wherein a shear force required to move the microstructured retractor along a wet surface exceeds an applied normal force when placed on the wet surface.

2. The microstructured retractor of claim 1, further comprising an expansion member, wherein the expansion member provides adjustable rigidity to the microstructured retractor.

3. The microstructured retractor of claim 1, wherein a suction member is attached to provide fluid removal in use of the microstructured retractor.

4. The microstructured retractor of claim 1, wherein the retractor has a shorter dimension, referred to as a width, and a longer dimension, referred to as a length, and the retractor comprises a flexible material that is capable of being pre-formed with an inherent curvature, wherein the width has substantially zero curvature and the length dimension has a radius of curvature that is less than the length.

5. The microstructured retractor of claim 1, wherein the retractor is corrugated in a direction such that only a portion of the microstructured surface is in contact with a wet surface when the retractor is placed on the wet surface, and wherein the corrugations are adjustable by permanent deformation of the microstructured retractor, thereby changing the amount of surface of the microstructured retractor that is in contact with the wet surface.

6. The microstructured retractor of claim 5, wherein the corrugations are reversibly deformable, and the retractor further comprises an expansion member such that when expanded, the corrugation frequency reversibly changes, and the expansion member further comprises a valve such that the expansion volume can be controlled.

7. The microstructured retractor of claim 6, wherein an additional expansion member is incorporated that when expanded reversibly hardens the microstructured retractor.

8. The microstructured retractor of claim 5, wherein the first corrugation state is in a Wenzel-Cassie state when in contact with a wet surface and the second corrugation state is in a Cassie-Baxter state when in contact with a wet surface.

9. The microstructured retractor of claim 1, wherein one side comprises a Wenzel-Cassie micro textured surface and the other side comprises a Cassie-Baxter micro textured state.

10. The microstructured retractor of claim 1, wherein the first arm has at least one surface comprising a Wenzel-Cassie surface and the second arm has at least one surface comprising a Cassie-Baxter surface.

11. The microstructured retractor of claim 1, wherein the at least one arm comprises at least one rose-simulating surface.

12. The microstructured retractor of claim 1, wherein the at least one arm comprises at least one lotus-like surface.

13. The microstructured retractor of claim 1, wherein at least a portion of the arms comprise a superhydrophobic surface.

14. The microstructured retractor of claim 5, wherein at least a portion of the arms comprise a superhydrophobic surface.

15. The microstructured retractor of claim 1, wherein at least a portion of the retractor comprises a surface having a contact angle hysteresis greater than 5 degrees when in contact with a wet surface.

16. The microstructured retractor of claim 5, wherein at least a portion of the retractor comprises a surface having a contact angle hysteresis greater than 5 degrees when in contact with a wet surface.