Two-phase bonded non-standard COSA device

Abstract

A device having a set of microstructures arranged on a substrate for gripping a low coefficient of friction material. The microstructures can provide physical properties of gripping force exceeding the gripping force theoretically achievable by friction theory alone. The microstructures can provide a gripping force exceeding 50.0 N. The arrangement of the microstructures can have a gripping surface with a contact area of ​​25% or less of the macroscopic total area of ​​the device.

Description

Technical Field

[0001] The present invention relates to a microstructural pattern, and more particularly to a gripping surface having a microstructural pattern adapted to improve the gripping of a low-COSA material that does not depend on the modification of the COSA (Coefficient of Static Adhesion) of a bulk material.

Background Art

[0002] Devices using polymer materials having a low COSA such as PTFE, HDPE, nylon, PET, PLA, and POM have been manufactured, and in such devices, generally, a lubricant easily slides or moves on the surface without staying on or both on and above the device surface.

[0003] Examples known in the art having a low COSA include a PTFE shaft seal that can slide against a polymer housing, a nylon polymer-coated blood vessel catheter that slides through a polypropylene introducer tube, or a PTFE-coated guide wire that slides inside a polymer-lined blood vessel catheter. Often, this material can exhibit a coefficient of friction of 0.2 or less when the material is tested under standard conditions.

[0004] However, the low COSA of the material can be advantageous under some conditions while being disadvantageous under other conditions. For example, low-COSA materials can be difficult to handle or operate during manufacturing, use, or decomposition. Conventional attempts to provide sufficient adhesion to overcome the problems of low-COSA materials include using additives in the material to provide a "sticky" surface. Other attempts include adding or using adhesives to provide sufficient gripping force during handling or operation of low-COSA materials. However, such conventional attempts result in undesirable materials and do not provide sufficient results because the adhesiveness of the additives or adhesives is too strong, resulting in an unnecessarily rough surface or causing discomfort during handling or use.

[0005] Therefore, there is a need to create a surface that can grip low-COSA materials without damaging the material surface, while allowing for easier handling of the material. Surface structures intended for friction typically damage the target surface through mechanical contact. Thus, increasing the gripping force by increasing friction typically damages the material surface, inhibiting and / or limiting the material's low-COSA properties.

[0006] Therefore, the object of this disclosure is to provide a surface having a microstructured pattern that forms a gripping surface capable of gripping low-COSA materials with greater force than a patternless surface, and without causing damage to the low-COSA material. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows one embodiment of an apparatus for determining the COSA of a material. [Figure 2] Figure 2 shows one embodiment of a basic two-level microstructure and modification method. [Figure 3] Figure 3 shows one embodiment of the hierarchical and lateral arrangement of microstructure surfaces. [Figure 4] Figure 4 shows a diagram of one embodiment of a microstructured surface, illustrating parameters that affect the contact angle and surface energy. [Figure 5] Figure 5 shows a PET polymer used in the manufacture of microstructured devices. [Figure 6] Figure 6 shows a poloxamer polymer used in the manufacture of microstructured devices. [Figure 7] Figure 7 shows one embodiment of a microstructured device in which a portion of the microstructure is hierarchical and a portion is lateral. [Figure 8] Figure 8 illustrates one embodiment of a microstructured device in which one level of microstructure reflects the symmetry of another level of microstructure. [Figure 9]Figure 9 shows an embodiment of a microstructured device in which one microstructure includes a second microstructure. [Figure 10] Figure 10 shows one embodiment of a microstructured device that employs a microstructure designed to provide a Wenzel-Cassie bonding effect and another microstructure designed to provide a friction effect. [Figure 11] Figure 11 shows one embodiment of a microstructured device that employs a microstructure designed to provide an attraction effect and another microstructure designed to provide a sealing effect. [Modes for carrying out the invention]

[0008] Herein, various embodiments will be described in more detail with reference to the drawings. Unless otherwise defined, all technical and scientific terms used herein have definitions consistent with their respective professional terms. Methods, devices, and materials similar or equivalent to those described herein may be used in the implementation or testing of the subject matter of this disclosure, and representative methods, devices, and materials are described herein.

[0009] Unless otherwise specified, terms and variations thereof used herein should be interpreted as non-limiting, as opposed to limiting, unless otherwise specified. Similarly, groups of items connected by the conjunction "and" should not be interpreted as requiring each item and all items to be present in the group. Furthermore, "and" should be interpreted as "and / or" except in the claims, unless otherwise specified.

[0010] Similarly, groups of items connected by the conjunction "or" should not be interpreted as requiring mutual exclusivity within the group; rather, unless otherwise explicitly stated, they should be interpreted as "and / or."

[0011] Furthermore, while items, elements, or components of this disclosure may be described or claimed in these embodiments, unless otherwise specified, the scope of the technical scope is intended to include multiple or any combination thereof. Broadening words and phrases such as “one or more,” “at least,” “not limited to,” or other similar phrases in some instances do not imply that a narrower definition is intended or required in instances where such phrases may not be present.

[0012] The gripping force generated by the devices of the present invention can, in some embodiments, exceed the gripping force attributable solely to friction, particularly when the interface between the two surfaces contains a liquid. This higher wet gripping force, which occurs in some embodiments, may be achieved by attractive surfaces at the interface between the device and the target surface. For example, some embodiments of the microstructured surfaces of the present disclosure include Wenzel-Cassie interfaces, as well as evaluable capillaries due to the hierarchical arrangement of microstructures. Pipe force may be included.

[0013] Other embodiments that contribute to the improved gripping force of the embodiments described herein include a high contact periphery, as well as a combination of hydrophobic and hydrophilic regions of the microstructure that can promote adhesion.

[0014] In some embodiments disclosed herein, microstructured devices have high dynamic adhesion. Rather, high static adhesion can occur. Dynamic adhesion is generally mediated by mechanical bonding between the microstructured surface and the target surface. Also, in some embodiments, the microstructured surface may be capable of generating high COSA.

[0015] In some embodiments, the microstructured device may have a greater COSA when a liquid is present between the device and the target surface compared to when a liquid is present between the device and the target surface.

[0016] In certain embodiments, a microstructured surface may have a surface pattern applied to a material intended to grip a target surface. In certain embodiments of a microstructured surface, the microstructured surface may include micro-features that include hierarchically stacked protrusions and / or recesses. In some embodiments, the micro-features may be arranged longitudinally relative to one another. The micro-features may be of different sizes. In some embodiments, the micro-features may be arranged in a hierarchical pattern in which a first set of micro-features is larger than a second set of micro-features, and the larger set of micro-features reinforces or enhances the effect of the second set of micro-features.

[0017] The hierarchical arrangement of microstructure patterns can be scale-dependent, size-dependent, surface energy-dependent, or function-dependent. In such configurations, a first microfeature can reinforce the effect of a second microfeature. In some embodiments, the hierarchical pattern is understood to include a single structure present on the surface of the second structure, but embodiments of this disclosure are not limited to this interpretation.

[0018] In one embodiment of the present disclosure, a pattern of microstructures arranged hierarchically or laterally as disclosed herein can generate a first shear force. This first shear force can be much greater than the frictional force defined in standard physics literature. In particular, the microstructure layers or ranges of size can be arranged to generate "hydrophilic" and "hydrophobic" interface regions, which can be described as hydrophilic or hydrophobic, but may also be fatty, oily, etc., as in affinity and repellency. In some embodiments, these "hydrophilic" and "hydrophobic" regions can generate shear forces far exceeding the classical physical frictional forces of the same or similar materials.

[0019] In some embodiments, the microstructural pattern may be arranged such that two adjacent microfeatures have a pitch defined as a percentage of the diameter, width, and / or thickness of one or the other or both of the microfeatures. For example, in one embodiment, the microfeatures can include pillars having a diameter of 10 microns, and these pillars can be arranged at 1 micron intervals, thereby having a pitch of 10%.

[0020] In some embodiments, there may be an adhesive force associated with the surface having the microstructural pattern, and this adhesive force is of a magnitude that exceeds the expected frictional force. This adhesive force can be achieved by slightly increasing the frictional component. The mediating force of most frictional microstructures is said to have a coefficient of friction of 0.7 - 1.4.

[0021] The coefficient of friction as used herein can be understood to include the value obtained by dividing the normal applied force by the shear force required to move the surface relative to the contact surface. Typically, the shear force F is related to the normal force N by the coefficient of friction (COF) μ. This relationship can be defined as F = μN assuming that the contact area between the object and the target surface is equal. Thus, μ can be a linear function of the contact area.

[0022] In certain embodiments where the contact area is not known, the coefficient of friction can be measured assuming that the contact area is 1:1. In the case of a microstructured surface, the surface contact area can be less than 1, and in fact, the surface contact area is inversely proportional to the coefficient of friction. Thus, in the case of a surface contact area of 1:1, the coefficient of friction can be μ = 1. However, in the case of the same surface having a microstructural pattern with a decreasing contact area, typically, it has a coefficient of friction proportional to the decreased area. For example, in the case of a material having a coefficient of friction equal to 1, if the contact area is reduced by a factor of 2 due to microstructural patterning, the coefficient of friction can be 0.5 or less.

[0023] ​​Alternatively, the same microstructure pattern may also increase the coefficient of friction due to edge effects associated with the microstructure; for example, the coefficient of friction against a surface with microstructure may exceed 1. Therefore, a microstructure may have a higher or lower coefficient of friction than a surface of the same material without microstructure.

[0024] It is important to recognize that the coefficient of friction of any material can generally be modified within a range of 0.5 to 1.5 by simply increasing the perimeter (not the area) or decreasing the surface area contact.

[0025] As used herein, the contact surface area may be understood to include the contact area between the microstructured surface and the target surface when both surfaces are dry and oriented perpendicular to the direction of gravity.

[0026] The contact surface area of ​​the microstructured surface and the target surface when the target surface is wet can be understood as the contact surface area when no liquid is present between the microstructured surface and the target surface.

[0027] The edge effect has long been known in the prior art, and devices with increased perimeter length to achieve a higher coefficient of friction are not novel. In the various embodiments disclosed herein, their adhesive properties do not necessarily depend solely on the increased perimeter length. The edge effect and surface area contact in this disclosure result in variations for a more fundamental and stronger effect.

[0028] For example, it is important to recognize that the outer surface of a gripping pad containing micropillars, or a microstructured pattern having recesses instead of microstructures, can exhibit a higher gripping force and coefficient of friction compared to the same material without a microstructured pattern. In this disclosure, we rely on the juxtaposition of micro-features with different surface energies to achieve higher adhesion to a target surface. This increase in adhesion can occur when one or the other or both surfaces are dry or wet.

[0029] In some embodiments, the microstructured surface of a polymer (e.g., PTFE) may be placed on a mold of metal, such as silicon, and the polymer may have a coefficient of friction of 0.8 or higher with respect to the metal. Microstructured pattern placed on a mold of metal, such as silicon On the same polymer surface without microstructure, the coefficient of friction can be approximately 0.2. Therefore, microstructure Patterned polymers may have a higher COF (Coefficient of Friction) than unpatterned polymers. The coefficient of friction is generally understood to be defined between two materials where the contact area is infinite and the influence of the outer periphery is minimal.

[0030] In the case of a microstructured surface, the contact area can be minimized relative to the length of the outer circumference of the contact surface of each microstructure. The perimeter of a microstructure may be the perimeter of the microstructure's cross-section. The perimeter of a set of microstructures may be the product of the perimeter of one microstructure and the number of microstructures in the set. The perimeter of a microstructured device may be the sum of the perimeters of the sets of microstructures.

[0031] In one embodiment, the coefficient of friction can be changed by the ratio between the outer circumference and the contact area, but such a change does not actually occur when the effect of increasing the contact circumference is taken into consideration.

[0032] When comparing materials, the coefficient of friction has a standard meaning when the perimeter is constant. If the perimeter increases even microscopically, it may no longer depend on the simple formula F=μN above. In particular, the coefficient of friction can change significantly with respect to the perimeter relative to the contact area. This relationship is known in the prior art. However, the improvement in resistance to movement due to the effect of the perimeter is not the subject of this disclosure and its embodiments.

[0033] Includes a microstructure pattern formed on a pad of a highly elastic polymer such as polyester terephthalate (Mylar) or modified polyester terephthalate (Hytrel or Tritan). Prior art devices have a COF of approximately 0 for polyester terephthalate relative to PTFE. It can be increased from 0.4 to over 1.00. This effect is due to the microstructure, as shown in Table 1. This can be fully explained by the increase in perimeter. Table 1 shows the linear relationship between the coefficient of friction of individual microstructures and perimeter.

[0034] The COSA (μ) measurement is performed using the test apparatus shown in Figure 1. The COSA method and device 100 comprises the following: The sample 102 has a surface 104 and microstructure features 106 on both sides of the surface 104. This surface and microstructure features can be the same size as the first and second gripping surfaces 108, 110. The first gripping surface 108 is fixed in place, and the second gripping surface 110 applies a vertical force (N) 111, which is adjusted via a regulator 113 and a tension spring 112. This force can be measured with a strain gauge, which is removed before applying a weight 120. The applied vertical force (N) is measured by placing the sample 102, having the surface 104 and microstructure features 106, between the gripping surfaces 108, 110 and pulling it in direction 116 until the tensile force displaces the sample 102 between the gripping surfaces 108, 110. Furthermore, the sample surface 104 has a hole 118 to which a weight 120 can be attached. COSA(μ) is measured by connecting the weight (total force of 50 Newtons) 120 to the hole 118, reducing the applied force supplied by the tension spring 112 until the sample 102 falls from the gripping surfaces 108, 110, and then measuring the vertical force 111 using a strain gauge 114. COSA(μ) is calculated using the following formula.

number

[0035] Here, it is important to note the coefficient 2 in the denominator. This coefficient is due to the fact that the sample is bifacial, possessing both a surface 104 and microstructural features 106.

[0036] Figure 1 shows the test setup, but this setup uses a sample with a substrate having only one pattern on one side. In reality, COSA is measured as the average value of COSA of two surfaces, one of which has a microstructured surface and the other a smooth surface. This experimental setup does not measure the COSA or COF of both microstructured surfaces 106. Also, please note that the experimental setup shown in Figure 1 is insufficient for measuring the coefficient of dynamic friction.

[0037] According to the document "AIP Handbook, Coefficients of Friction, Dudley Fuller," kinetic friction The coefficient is the value obtained by dividing the magnitude of the maximum frictional force by the magnitude of the normal thrust once the motion is established. The problem associated with the dynamic definition is that the dynamic friction coefficient depends on atmospheric humidity, sliding speed, While it depends on temperature, vibration, and any surface contaminants, these factors are not significant when determining the coefficient of static friction.

[0038] For example, the "AIP Handbook" lists the following (Table 1) coefficients of kinetic friction.

[0039] Table 1: Dynamic coefficients of friction, steel and steel, lubrication [Table 1]

[0040] The data above shows that the coefficient of dynamic friction (COF) varies as a function of sliding speed for different materials. Unless ambient conditions are precisely defined and maintained, there are no consistent dynamic COF measurements that can be used to compare different materials with different microstructured surfaces.

[0041] The static friction coefficient is a single-value quantity that can occur under a wide variety of ambient conditions, provided that the sample being measured is not moving, i.e., the measurement is taken immediately before sliding occurs.

[0042] Table 2 shows examples of effects generally applicable to simple surface microstructuring patterns. For example, in a hierarchical pattern where one set of microstructures is positioned on top of a second set of microstructures, the effect generally applies only to the topmost microstructure. Therefore, each effect exhibits a classical dependence on the deformation of the microstructure caused by a given perpendicular force and is therefore not expected to be linear as shown by the above equations. Nevertheless, all of these effects are well known in terms of the precise calculation of edge effects quantified by perimeter length.

[0043] Table 2 shows the COSA(μ) measurement results for embodiments having the microstructured surface shown in Figure 2. The microstructured surface 200 may include a first microfeature 202 and a second microfeature 204, the second microfeature being positioned on the first microfeature. In some embodiments, the first microfeature 202 may have a diameter of about 200 microns. The second microfeature 204 may have a diameter of about 20 microns. To vary the perimeter, a strip of substrate is embossed on top of the microstructure. In some embodiments, the microstructured surface is molded from polylactic acid.

[0044] The term "100% microstructure" includes examples where 200-micron pillars are spaced 100 microns apart across the entire substrate surface. On the other hand, "90% microstructure" means that 10% of the microstructure is embossed on a flat surface. Surfaces with microstructure covering 100% to 10% of the substrate are tested. The minimum contact area between the microstructured surface and the target flat surface is provided by the 100% microstructured surface, and the contact area increases as the microstructure area decreases.

[0045] Table 2: COSA, dry (N=10) [Table 2]

[0046] The coefficient of static friction of a microstructured surface can depend on both the contact area (shown in Table 2) and the perimeter. The contact area is well-explained, and the coefficient of static friction can be linearly proportional to the contact area. In Table 2, the contact area and the perimeter of the microstructure can decrease by the same amount.

[0047] Referring to Figure 2, the microstructure surface may be stretched in a first direction 206 and compressed in a second direction 208, the density of the first microstructure 202 may change, and the surface area may change independently. The surface area of ​​the microstructure surface can be increased by compressing the second microstructure 204 and changing the arrangement of the microstructure features on the surface. The contact area may be the sum of the surface areas of the first microstructure 202. The perimeter of the first microstructure 202 may be the perimeter of the newly arranged surface. The contact perimeter is the sum of the perimeters of the first microstructure 202.

[0048] As the density of pillars decreases, the perimeter can be increased to maintain the contact area. In Table 3, the surface area is constant, the perimeter changes, and the COSA measurements are normalized to the pattern in Table 2, with a surface area of ​​1 and a perimeter of 1.

[0049] Table 3: COSA, dry [Table 3]

[0050] The table above shows that approximately 75% of the decrease in the coefficient of static friction can be attributable to the perimeter length rather than the contact surface. Therefore, when using the standard formula for the coefficient of static friction or COSA (for microstructured surfaces), the contact area may not be relatively important relative to the perimeter length of the microstructure. Thus, in two microstructures with the same contact area, one with large pillars and the other with small pillars, the microstructure with smaller pillars may have a higher COSA.

[0051] As a result, the microstructured pattern shown in Figure 1 is any one with a COF greater than 0.8 It can be formed from a steel or high modulus polymer pad that grips a polymer material with a low modulus of elasticity. In the friction coefficient measurement protocol of the present invention, it is not unexpected that a high modulus polymer with a microstructured surface can provide a tensile force of more than 50 Newtons, and a perpendicular force of 50 Newtons, according to the COSA protocol of the present invention.

[0052] It is important to understand that a distinction can be made between the friction coefficient of a single phase and the friction coefficient of a two-phase system. The standard physical description of the friction coefficient as expressed by the above formula includes only one solid phase in contact with a second solid phase. However, when a third phase is included, novel and unexpected shear and peeling forces appear, such as when the first and second solid phases are in contact with a liquid or gaseous phase (the third phase). The concept of friction coefficient does not readily apply to solids connected via a gaseous or liquid phase, gases connected via a solid phase or a gaseous phase, or gases connected via a solid phase or a liquid phase. These two-phase structures are the subject of this invention.

[0053] Referring to Tables 4 and 5, the structure shown in Figure 2 is tested in the two-phase (wet) embodiment. Comparing Tables 2 and 3 with Tables 4 and 5, for the one-phase (dry) microstructured surface and the two-phase wet microstructured surface, the COSA is linearly proportional to the shear force for the dry microstructured surface, not proportional to the contact area or perimeter. Furthermore, the COSA is greater than the higher size for the wet and dry microstructured devices of the present invention.

[0054] Tables 4 and 5 show a novel phenomenon that has not been previously understood and cannot be technically explained by the coefficient of friction. The effect found here is largely independent of surface area or perimeter, but instead, the geometry of the microstructure may play a dominant role in the resistance to the movement of the microstructured device when the target surface is coated with a liquid.

[0055] This effect is related to a metastable interface state called the Wenzel-Cassie interface. This interface in contact with the structure is unexpected and may reveal a wet interface between the microstructured surface and the target surface exhibiting non-classical physical shear force phenomena.

[0056] Table 4: Wetness (N=10) [Table 4]

[0057] Table 5: COSA, Wet [Table 5]

[0058] In reality, a true solid on a solid interface is never realized. For example, everyday objects often contain condensed liquids, oils, and other substances. These layers may be microscopic but can have macroscopic effects. For instance, the microstructure patterns of gripping pad surfaces, rotating gripping surfaces, glove fingertips, brake pads, clutch plates, pliers working surfaces, gripping instruments, retractors, cotton swabs, robotic tools, and laparoscopic surgical devices all involve a second phase, typically a liquid or fluid medium.

[0059] The gripping surface may take the form of a tape, film, or layer formed on a working surface, such as a handle and label for a tool, a closure, a surface for an instrument, or a coating surface for everyday objects that typically come into contact with liquids. Often, microstructured surfaces can be designed for interfaces with various second phases, such as water, surfactants, oils, or combinations thereof. The grip strength of the microstructured surface of the present invention may be enhanced by the liquid that can be structured by the interface. For example, in some embodiments, water forms a microstructured liquid with hydrogen bonds depending on van der Waals forces. In some embodiments, oil forms an encasing structure. Furthermore, in some embodiments, amphiphilic structures, surfactants, can form biological structures such as cell walls. All of these structures are synthetically induced on the microstructured surface with appropriate contact angles. These contact angles can be designed to vary across the hierarchical structure of the microstructure. The microstructured surface may be organized to have alternating high and low surface energy regions, where the high surface energy regions may generate flow regions and the low surface energy regions may generate locking or constraining regions. The combination of flow and locking regions is called the Wenzel-Cassie interface.

[0060] The reason why microstructured surfaces can have a higher dry COSA than unmicrostructured surfaces is that shear forces can be dominated by an increase in perimeter due to the microstructure in contact with the target surface.

[0061] In the case of hierarchical microstructures, the lower layers of the microstructure do not need to be in contact with the target surface (relative to a rigid target surface) and do not need to contribute to dry COSA. Therefore, the perimeter does not necessarily need to be increased and can even be decreased. Nevertheless, a hierarchical microstructure surface in contact with a wet interface can generate shear forces that may be insensitive to perimeter, and as described herein, these shear forces may exceed any of the dry shear forces for various perimeters.

[0062] For example, referring to Tables 6 and 7, it can be seen that when the second-level microstructure is planarized relative to the first layer, and the contact area is kept constant by the stretching and compression of the microstructure, a two-level hierarchical structure providing hydrophilic surface areas juxtaposed with hydrophobic surface areas has a higher COSA than a one-level surface in contact with a wet target surface. Here, all values ​​are normalized to 1, which is the force of the dry two-level. In these embodiments, there is essentially no difference between the one-level and two-level surfaces when dry, but the flexible surface can be deformed by the microstructure, which enhances the second level compared to the one-level device. Tables 6 and 7 should not be compared in an absolute sense because the normalizations differ in the two cases. In Tables 6 and 7, wetting the one-level has a lower COSA than drying the one-level (classical result).

[0063] Table 6: COSA, dry, steel grip [Table 6]

[0064] Table 7: COSA, drying, silicone rubber grip [Table 7]

[0065] In the embodiments disclosed herein, as shown in Tables 6 and 7, despite differences due to the elastic modulus of the target surface, the COSA of a two-level hierarchical surface including a liquid interface for the target surface is consistently more than an order of magnitude higher than that of a two-level hierarchical surface at a dry interface. While the difference between a one-level and a two-level microstructured surface is small at the dry interface, the difference is significant at the wet / liquid interface.

[0066] In some embodiments, at the water-gas interface, or in the case of biological interfaces, at the water-lipid interface, the two components of the liquid interface can separate into lipophilic and hydrophobic regions. That is, water droplets can adhere to the hydrophilic, high-surface-energy regions of the microstructure, while gas or lipid spheres can adhere to the hydrophobic, low-surface-energy regions of the microstructure. This type of lipophilic-hydrophobic separation interface, known as such, can be said to be in a lower energetic state than interfaces between gas and liquid, or a mixture of water and lipids. It produces a Wenzel-Cassie wetting state. When a finely structured surface is moved relative to a target surface between two surfaces, the energy required for the movement can be greater than that required for an interface where hydrophilic and hydrophobic components are not separated. As a result, the microstructure can be used to obtain a liquid interface with a target surface of any rigidity that exhibits a COSA at least an order of magnitude higher than that obtained at a gas-only interface.

[0067] It is known that interfaces consisting solely of water may not exhibit the enhanced gripping effect disclosed herein. In the case of microstructured surfaces with different surface energies, i.e., hierarchical or distributed structures, water alone can be organized into high-energy and low-energy regions via hydrogen bonding. Such separation is not visually apparent and is referred to in the literature as structured water.

[0068] The improved gripping effect in the embodiments disclosed herein depends on structural or steric changes in the interfacial composition between the microstructure and the target surface, and such structural effects can result in a COSA at least an order of magnitude greater than the effect attributable to the surface's contact area and / or perimeter.

[0069] Interestingly, as shown in Table 8, when there is a liquid interface, common sense regarding the static or kinetic friction coefficient between the two surfaces can be considered.

[0070] Table 8: Decrease in COF due to liquid interface [Table 8]

[0071] Embodiments having microstructured surfaces disclosed herein may fall outside the range of COF disclosed in Table 8. In particular, embodiments having microstructured surfaces disclosed herein may result in a COSA greater than 2.0 COSA.

[0072] (Example 1: Microstructure that gives rise to the Wenzel-Cassie interface)

[0073] In the art of the present invention, surface energy is generally understood as the contact angle of a water droplet when placed on a surface. Since the water droplet interacts with one or more layers of microstructure, the interface layer established between the microstructured surface, the fluid layer, and the target surface can be complex. In this example, it is intended to enable those skilled in the art to generate improved target COSA between a microstructured surface and a certain range of target surfaces.

[0074] One or more parameters relating to the microstructured surface include, but are not limited to, (1) the pitch or distance between the centers of the microstructure, (2) the area of ​​the microstructure, and (3) the height of the microstructure.

[0075] The latter parameters may not be considered relevant to those not implemented in the art of this invention. A microstructured surface having multiple layers of microstructures provides a three-dimensional surface to the environment. Such a surface can organize environmental components and a target surface according to the distribution of different surface energy surfaces.

[0076] For example, referring to Figure 3, the microstructured surface 300 includes a first microstructure level 302, a second microstructure level 304, and a third microstructure level 306. Transverse microstructures 308 may also be present. Such structures have surface energy distributions in both the plane 310 and the normal 312. For example, the first region 314 has a different surface energy than the second region 316. Thus, the interfacial fluid 318 includes hydrophilic components 320 and hydrophobic components 322, respectively, associated with high surface energy surfaces such as the first region 314 and low surface energy surfaces such as the second region 316. Furthermore, the regions of the lipophilic components 320 and hydrophobic components 322 are essentially three-dimensional. The lipophilic components 320 with different surface energies than the hydrophobic components 322 do not easily pass through each other and therefore require substantial energy for that, which is interpreted as a high static friction coefficient.

[0077] The embodiment shown in Figure 3 is understood to generate a Wenzel-Cassie interface when a liquid is present at the interface between the target surface and the microstructured surface.

[0078] (Example 2: Relationship between contact angle and pitch of a microstructured surface)

[0079] Understanding the relationship between microstructure pitch and contact angle can be beneficial when designing hierarchical microstructured surfaces with different surface energy (contact angle) regions.

[0080] Referring here to Figure 2, an embodiment is shown in which the surface contains a polymer, such as polylactic acid, and the microstructural features have a pitch that can be modified by thermal equilibrium elongation. The water contact angle can be measured as a function of pitch. Theoretically, the shape of the liquid-vapor interface can be determined by the Young-Dupre equation, and the contact angle plays the role of a boundary condition via Young's equation.

[0081] A theoretical explanation of contact is given by considering the thermodynamic equilibrium between the three phases: the liquid phase, the solid phase, and the gas or vapor phase (which may be a mixture of the ambient atmosphere and the liquid-vapor equilibrium concentration). Referring here to Figure 4, the microstructured surface 400 may include the surface 401 on which the microstructured features 402 are arranged. In some embodiments, the liquid 404 may be in contact with the microstructured features 402 so that the liquid "remains" on top of the microstructured features. The liquid phase 403 and the gas phase 405 may influence the thermodynamic equilibrium depending on the microstructured pattern and the interaction of all three phases.

[0082] The "gasic" phase can be replaced by another immiscible liquid phase, such as a lipid phase. Referring to Figure 4, the solid-vapor interface energy is expressed by the solid-liquid interface energy, and the liquid-vapor interface energy (i.e., surface tension) is expressed by the liquid-vapor interface energy, and the equilibrium contact angle is determined from these quantities by Young's equation.

number

[0083] Regarding the nomenclature of dimensions, for practical reasons, the pitch p is measured and reported as the distance between pillars at the first level, rather than the distance from pillar center to pillar center (the usual definition). The standard pitch dimension P is given by the following formula, relating the measured pitch dimension p to... They are related. In the following equation, D is the pillar diameter of the first level.

number

[0084] Embodiments disclosed herein having various pitches can be generated by spray-mounting the embodiment of Figure 1 onto a cooled copper plate, then slowly heating it to about 40°C to equilibrate, and then rapidly cooling it to 0°C so that the pattern can be easily released from the spray mount. This can result in uniform pitch variation in both the x and y directions. Increasing the pitch dimension can be achieved by applying this technique multiple times. The test area is microscopically selected so that the pattern in the test droplet is uniformly expanded.

[0085] Using water, the contact angle (degrees) X is measured relative to the pitch Y. The straight line to fit the data is given below for the embodiment shown in Figure 2.

number

[0086] (Example 3: Effect of contact angle on living cells)

[0087] Embodiments of microstructured surfaces disclosed herein may be useful as implants in the body because they can provide resistance to migration in wet conditions. Living cells serve as suitable probes for surface energy as a function of pitch or distance between surface microstructures. In addition to fixing implants in situ, microstructured surfaces can be used to promote healing. We can provide support.

[0088] By measuring the resonant frequency of a microstructured surface, the adhesion of cells to a microstructured substrate can be measured. Epithelial cells were cultured on an electrospun microstructured surface and a flat surface of the same material.

[0089] The resonant vibrations of individual epithelial cells supported on a surface are measured using a simple optical detection technique. The epithelial cells are impulsed with a stream of saline solution, a laser beam is passed through the cells, and the change in the intensity of the scattered light is measured using a fiber-optic-terminated spectrometer to monitor their time-dependent resonant vibrations. The obtained time-dependent intensity changes are Fourier transformed using software supplied to the spectrometer to obtain information about the vibration frequency of the droplet. The cell resonance frequencies are acquired on surfaces with water contact angles in the range of 55–72.5 degrees. The contact angle dependence of the resonant frequency of cells exposed to a stable water flow is measured.

[0090] Embodiments having a microstructured surface have the chemical structure shown in Figure 5 and a temperature of approximately 72.5 degrees It is constructed using PET with a contact angle. The PET is blended with polyurethane poloxamer in the form shown in Figure 6. The polyurethane poloxamer has a contact angle of approximately 55 degrees.

[0091] When PET is slowly added to polyurethane poloxamer in solution, contact angles of 55.3, 60.7, 65.5, 70.1, and 72.5 are obtained.

[0092] When the cell frequency Y is plotted against the contact angle X, the following equation is obtained.

number

[0093] Combining this with the pitch-contact angle formula above, we obtain the following equation:

[0094]

number

[0095] And the following equation is obtained.

[0096]

number

[0097] Here, the pitch contact angle is assumed to be close to the material contact angle, giving a relationship between the expected cell adhesion force (Freq.) as a function of the microstructure pitch.

[0098]

number

[0099] The above equation gives the relationship between the tone and pitch of cells for a given substrate material. Here, tone is understood as a resonant frequency that is somewhat independent of the flow that induces such tone.

[0100] For epithelial cells on a flat surface, lower material surface energy (lower contact angle) may correlate with lower resonant frequencies. On a microstructured surface, closer spacing (smaller pitch) may correlate with lower energy (higher hydrophobicity, higher contact angle). In conclusion, closer pillar spacing (smaller pitch) may result in lower resonant frequencies (looser coupling) between the cells and a given type of microstructured surface.

[0101] This result can be understood as surprising, given that it is the opposite of what was expected. This result may only be valid for pitches close to the cell dimensions, i.e., in the range of 5 to 100 microns. This result can be explained by the fact that the surface energy of the cell wall may be dominant on low-energy surfaces, and therefore the responsiveness to the underlying ultrastructure may be lower. This may suggest that the resonant frequency of free cells can be less than 1 Hz. Therefore, high-energy ultrastructured surfaces can bind cells more strongly to the environment.

[0102] (Example 4: Microstructured device for gripping low-COSA target surfaces containing multiple microstructures)

[0103] Referring to Figure 7, the microstructured device 700 has a surface 702, a first microstructure 704, a second microstructure 706, and a third microstructure 708. The first microstructure 704 may have a synusoidal surface. The second microstructure 706 may have a series of radial ridges (710) arranged hierarchically on the surface 704 and non-hierarchically on the surface 702. The third microstructure 708 may have pillars arranged on a portion of the first microstructure 704.

[0104] (Example 5: Microstructured device for gripping a low-COSA target surface, including multiple hierarchically arranged microstructures)

[0105] Referring to Figure 8, the microstructured device 800 has a surface 802, a first microstructure 804, a second microstructure 806, and a third microstructure 808. The first microstructure 804 may include a sinusoidal wavefront. The second microstructure 806 may have pillars arranged hierarchically on the first microstructure 804. The third microstructure may have a series of ridges 810 arranged hierarchically on the second microstructure 806 such that the direction of the ridges 812 on each second microstructure 806 is tangent to a circle 814 parallel to the substrate 802, whose center is also the center of the sinusoidal peak 816.

[0106] (Example 6: A microstructure device for gripping a low-COSA target surface, comprising two microstructure sets, wherein one microstructure set comprises the other microstructure set.)

[0107] Referring to Figure 9, the microstructured device 900 has a substrate 902, a first microstructure 904, and a second microstructure 906. The first microstructure 902 may have a second microstructure 906 having a stepwise changing height 908. The second microstructure 906 may have pillars of the first microstructure 904 embodied as tetrahedra.

[0108] (Example 7: Microstructured device for gripping low-COSA target surfaces including frictional sides)

[0109] Examples 4-6 can be used to target surfaces that achieve a higher COSA at the wet interface.

[0110] Referring to Figure 10, the microstructured device 1000 has a surface, a first microstructure 1004, a second microstructure 1006, and a third microstructure 1008. The first microstructure 1004 may have rectangular pillars. The second microstructure 1006 may have smaller rectangular pillars arranged on the first microstructure 1004. The third microstructure 1008 may have a series of hooked fibers arranged between a plurality of first microstructures 1004, so that the hooked fibers of the third microstructure 1008 readily adhere to irregular surfaces when dry and lie flat when wet.

[0111] (Example 8: Microstructured device for gripping low-COSA target surfaces, including liquid-encapsulated devices)

[0112] Referring to Figure 11, the microstructured device 1100 may have a surface 1102, a first microstructure 1104, a second microstructure 1106, and a third microstructure 1108, the third microstructure may have a contour that fills defects. The first microstructure 1104 and the second microstructure 1106 are composed of regular arrays and form a hierarchically arranged composite pillar capable of generating attractive forces when positioned in contact with a wet surface. The third microstructure 1108 may be located in a sealing region 1110 capable of generating undulations when wet. The volume of the undulation portion 1112 may extend to the third microstructure 1108 beyond the height of the second microstructure 1106 and / or the heights of the first microstructure 1104 and the second microstructure 1106. Therefore, the third microstructure 1108 can form a sealing region 1110 between the microstructured device 1100 and the target surface 1114.

[0113] In some cases, the Young's modulus of the material may be higher than, equal to, or lower than that of the target surface, depending on the degree of interface formation and the delicacy of the target surface.

[0114] In some embodiments, the Young's modulus may include any Young's modulus possible in solid form. In particular, the gripping surface does not have to have a high Young's modulus or a higher modulus than the target surface. Thus, embodiments having a gripping surface disclosed herein may not have a Young's modulus higher than the material being gripped, but the gripping force generally increases with Young's modulus, and the gripping material conforms well to the target surface. If the Young's modulus of the microstructured surface is poorly suited, the shear force may be impaired due to insufficient contact area.

[0115] In fact, in various examples of the embodiments disclosed herein, the gripping surface may have a lower Young's modulus than the target contact surface in at least one aspect of the pattern of the microstructured surface of the present application.

[0116] Therefore, although specific embodiments of the present invention relating to novel and useful "two-phase bonded non-standard COSA devices" have been described, this description is not intended to be construed as limiting the technical scope of the present invention, except as set forth in the following claims.

Claims

1. A microstructured device for gripping a low coefficient of friction material, The device has a substrate, the substrate has a gripping surface, the gripping surface has a first microstructure and a second microstructure, the first microstructure and the second microstructure have protrusions or voids, and the protrusions or voids create a Wenzel-Cassie state when in contact with a target surface. ru A microstructured device characterized by the following features.

2. The microstructured device according to claim 1, characterized in that the gripping surface further has a third microstructure.

3. The microstructured device according to claim 1, characterized in that the protrusion or the gap is cylindrical, conical, spherical, or polyhedral in shape.

4. The microstructured device according to claim 1, characterized in that the first microstructure is a two-dimensional synusoid microstructure.

5. The microstructured device according to claim 1, characterized in that the first microstructure and the second microstructure are configured such that the proportion of the contact area with the target surface is 50% or less.

6. The microstructured device according to claim 1, characterized in that the COSA (Coefficient of Static Adhesion) of the gripping surface is greater than 3.

7. The microstructured device according to claim 1, characterized in that the second microstructure is arranged hierarchically on the first microstructure.

8. The microstructured device according to claim 1, characterized in that the first microstructure and the second microstructure are provided with a pitch of 1 to 1000%, a height of 1 to 1000 microns, and a diameter of 1 to 1000 microns.

9. The microstructured device according to claim 8, characterized in that the first microstructure is provided with a pitch of 45 to 185%, a height of 50 to 250 microns, and a diameter of 35 to 125 microns.

10. The microstructured device according to claim 1, characterized in that at least one of the first microstructure and the second microstructure has a tapered shape toward the target surface.

11. The microstructured device according to claim 10, characterized in that at least one of the first microstructure and the second microstructure has a tapered shape toward the target surface, which can be represented by trigonometric functions.

12. The microstructured device according to claim 1, characterized in that the surface area of ​​the gripping surface is 10 times or more the surface area of ​​the substrate.

13. The microstructured device according to claim 2, characterized in that the third microstructure has a series of hooked fibers.

14. The series of hooked fibers are arranged between the first microstructure and the second microstructure. The microstructured device according to claim 13, characterized in that...

15. The microstructured device according to claim 2, characterized in that the third microstructure can generate undulation when wet.

16. The microstructured device according to claim 15, characterized in that the third microstructure exceeds the height of the second microstructure and / or the heights of the first and second microstructures when wet.

17. The microstructured device according to claim 2, characterized in that the third microstructure has a series of parallel ridges arranged hierarchically on the second microstructure.

18. The microstructured device according to claim 1, characterized in that the first microstructure has pillars whose height changes in steps.

19. A microstructured device for gripping a low coefficient of friction material, The device has a substrate, the substrate has a gripping surface, the gripping surface has a first microstructure, a second microstructure, and a third microstructure, the first microstructure, the second microstructure, and the third microstructure have protrusions or voids, the protrusions or voids are Wenzel-Cassie state to cause A microstructured device characterized by the following features.

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