Preparation method of bionic adhesive material with tip-expanded microstructural array

Abstract

A preparation method of a bionic adhesive material with a tip-expanded microstructural array includes the following steps: machining through-holes on a metal sheet; modifying morphology of a through-hole by electroplating, using the metal sheet in step 1 as an electroplating cathode, and arranging the electroplating cathode and an electroplating anode in parallel to prepare a hyperboloid-like through-hole array assembly, fitting a lower surface of the hyperboloid-like through-hole array assembly tightly to an upper surface of a substrate assembly to prepare a through-hole assembly of a mold; and filling the mold assembly with a polymer, curing, and demolding to obtain the adhesive material with the tip-expanded microstructural array.

Claims

1. A preparation method of a bionic adhesive material with a tip-expanded microstructural array, comprising the following steps: step 1: machining a through-hole array on a metal sheet; step 2: modifying morphology of a through-hole by an electroplating process, using the metal sheet in step 1 as an electroplating cathode, and arranging the electroplating cathode and an electroplating anode in parallel to prepare a hyperboloid-like through-hole array assembly, fitting a lower surface of the hyperboloid-like through-hole array assembly tightly to an upper surface of a substrate assembly under a positive pressure, wherein the upper surface of the substrate assembly extends over an opening of the hyperboloid-like through-hole array assembly, and the hyperboloid-like through-hole array assembly and the substrate assembly constitute a mold assembly; and step 3: filling the mold assembly in step 2 with a polymer to obtain a product, curing and demolding the product to obtain the bionic adhesive material with the tip-expanded microstructural array; wherein the substrate assembly is a plurality of elastic pads with different elastic moduli, and the elastic moduli of the substrate assembly range from 0.3 to 60 MPa; a tip morphology of the tip-expanded microstructural array is adjustable by adjusting the positive pressure between the hyperboloid-like through-hole array assembly and the substrate assembly.

2. The preparation method of the bionic adhesive material with the tip-expanded microstructural array of claim 1, wherein in the through-hole array in step 1, an aperture of the through-hole is not greater than 100 μm, a center distance between two adjacent through-holes is not greater than 100 μm, the through-hole is a cylindrical-shaped hole or a special-shaped hole, and a thickness of the metal sheet is not greater than 1 mm.

3. The preparation method of the bionic adhesive material with the tip-expanded microstructural array of claim 1, wherein the electroplating process in step 2 comprise the following steps: performing a first electroplating on a cleaned and activated through-hole array with a nickel pre-plating formula for 1-3 min at room temperature, with a first current density of 2-8 A/dm.sup.2 to obtain a pre-plated through-hole array; then placing the pre-plated through-hole array into an electroplating bath, wherein the pre-plated through-hole array is used as a cathode, a nickel plate is used as an anode, and the cathode and the anode are arranged in parallel; electroplating parameters include a second current density of 2-5 A/dm.sup.2, and a plating temperature of 50° C.−70° C.; subsequently, performing a mechanically stirring throughout the electroplating process, and performing a second electroplating on the pre-plated through-hole array for 1-3 h to form the hyperboloid-like through-hole array assembly with a central diameter smaller than diameters of two ends.

4. The preparation method of the bionic adhesive material with the tip-expanded microstructural array of claim 1, wherein the polymer in step 3 is an organic elastomer or an inorganic elastomer selected from the group consisting of polydimethylsiloxane, a silicon polymer elastomer with additional cross-linking agents, a prepolymer containing acrylate functional groups, a two-component prepolymer, a rubber material, a modified material of the polydimethylsiloxane, a modified material of the silicon polymer elastomer with additional cross-linking agents, a modified material of the prepolymer containing acrylate functional groups, a modified material of the two-component prepolymer, and a modified material of the rubber material.

5. The preparation method of the bionic adhesive material with the tip-expanded microstructural array of claim 1, wherein the polymer in step 3 is an inorganic elastomer selected from the group consisting of polydimethylsiloxane, a silicon polymer elastomer with additional cross-linking agents, a rubber material, a modified material of the polydimethylsiloxane, a modified material of the silicon polymer elastomer with additional cross-linking agents, and a modified material of the rubber material.

6. The preparation method of the bionic adhesive material with the tip-expanded microstructural array of claim 1, wherein the polymer in step 3 is an organic elastomer selected from the group consisting of a prepolymer containing acrylate functional groups, a two-component prepolymer, a rubber material, a modified material of the prepolymer containing acrylate functional groups, a modified material of the two-component prepolymer, and a modified material of the rubber material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow chart showing a preparation method of an adhesive material with a tip-expanded microstructural array of the present invention;

(2) FIG. 2 is a top view showing a through-hole assembly of the present invention;

(3) FIG. 3 is a cross-sectional view showing the through-hole assembly of the present invention;

(4) FIG. 4 is a schematic diagram showing a control principle of a substrate assembly on the tip morphology of a microstructure of the present invention;

(5) FIG. 5A is an electron microscope diagram showing an adhesive material with a tip-expanded cylindrical array in the embodiment of the present invention;

(6) FIG. 5B is an electron microscope diagram showing the adhesive material with the tip-expanded cylindrical array in the embodiment of the present invention; and

(7) FIG. 5C is an electron microscope diagram showing the adhesive material with the tip-expanded cylindrical array in the embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention is described hereinafter with the specific embodiments shown in the drawings. However, it should be understood that these descriptions are only illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and techniques is omitted to avoid unnecessary confusion of the concepts of the present invention.

(9) As shown in FIG. 1, the flow chart of the preparation method of the adhesive material with the tip-expanded microstructural array of the present invention is shown, and the specific steps are as follows.

(10) Step 1: a through-hole array is machined on a metal sheet by laser. The diameters of the through-holes are not greater than 100 μm, and the center distance between two adjacent through-holes is not greater than 100 μm. The thickness of the metal sheet is not greater than 1 mm, and the through-holes are cylindrical-shaped holes or special-shaped holes.

(11) Step 2: the morphology of the through-hole is modified by electroplating to prepare a mold assembly; the modification of the through-hole by electroplating means that the thickness of the coating in the middle of the through-hole is thicker by electroplating, and gradually becomes thinner to both sides along the axis direction of the through-hole.

(12) Step 3: the mold assembly is filled with a polymer, cured and demolded to obtain the adhesive material with the tip-expanded microstructural array. The mold assembly includes the through-hole assembly and a substrate assembly, the through-hole assembly is prepared by step 2 in claim 1, and the substrate assembly includes a series of components containing materials with different elastic moduli. When the substrate assemblies with different elastic moduli are selected for use, the tip morphology of the microstructure can be adjusted. The polymer is an organic elastomer or an inorganic elastomer, such as polydimethylsiloxane (PDMS), a silicon polymer elastomer with additional cross-linking agents, a prepolymer containing acrylate functional groups, a two-component prepolymer, a rubber material, or a modified material of the above materials.

(13) In this embodiment, SUS304 stainless steel strip is used for preparation, and the following technical solution are used for specific implementation.

(14) Step 1: SUS304 stainless steel strip with a thickness of 0.06 mm is used, and a picosecond laser is used to process a cylindrical through-hole array with a diameter of 0.085 mm and a hole spacing of 0.13 mm. The adjacent two rows of holes are arranged in a staggered arrangement.

(15) Step 2: the through-hole array prepared in step 1 is immersed in a 10 wt % oxalic acid solution, subjected to ultrasonic cleaning until the slag is removed, put into an alkaline degreaser for ultrasonic cleaning for 20 min, then cleaned with deionized water, immersed in 37% concentrated hydrochloric acid (HCl) for 0.5-1 min at room temperature to activate the surface, electroplated with a nickel pre-plating formula for 1 min at room temperature with a current density is 2 A/dm.sup.2. Subsequently, the through-hole array is placed into an electroplating bath, the through-hole array is used as a cathode, the nickel plate is used as an anode, and the two electrodes are arranged in parallel. The electroplating parameters include a current density of 2 A/dm.sup.2 and a plating temperature of 55° C.-60° C. Subsequently, mechanically stirring is performed throughout the whole electroplating process, and the electroplating is performed for 2 h to form the hyperboloid-like through-hole array assembly with a small diameter in the middle and large diameters at both ends, as shown in FIGS. 2-3.

(16) Step 3: (Sylgard 184A) and a curing agent (Sylgard 184B) are mixed evenly according to a mass ratio of 10:1 to prepare PDMS in advance. The lower surface of the through-hole assembly and the upper surface of the substrate assembly of the mold are closely fitted under a certain positive pressure, and the hyperboloid-like through-hole and the elastic pad form a “sucking plate-like” interface, as shown in FIG. 4. Then, the PDMS is poured into the mold. In this embodiment, polytetrafluoroethylene (PTFE) with large elastic modulus is selected as the substrate assembly of the mold. The bubbles are removed by vacuum for 10 min. Then the product is cured in a convection oven at 70° C. for 2 h. Finally, demolding is carefully performed to obtain the adhesive material with the tip-expanded cylindrical array, as shown in FIGS. 5A-C. The greater the pressure between the through-hole assembly and the substrate assembly, the smaller the elastic modulus of the substrate, the deeper the substrate sinks into the through-holes, and the deeper the central depression of the “sucking plate-like” tip in the microstructure of the finally poured adhesive material, thereby realizing the preparation of adhesive materials with different properties. The depth of the central depression of the “sucking plate-like” tip is positively correlated with the elastic modulus (E.sub.0), Poisson's ratio (μ.sub.0), and positive pressure (P) of the substrate.

(17) The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and the descriptions in the specification only illustrate the principle of the present invention. Various changes and modifications may be derived without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The protective scope of the present invention is defined by the protective claims and the equivalents thereof.