Flat-pressing manufacturing method of bionic adhesive structure based on micro through-hole nickel-based mold

Abstract

A flat-pressing manufacturing method of a bionic adhesive structure based on a micro through-hole nickel-based mold is disclosed. The method includes the following steps: preparing a nickel-based mold with a micro through-hole array; placing the nickel-based mold on an elastic pad in a magnetic mold closing system; coating a liquid prepolymer uniformly on a backing, and placing a side of the backing coated with the liquid prepolymer on the nickel-based mold, covering a sealing diaphragm on the backing to separate a cavity into an upper chamber and a lower chamber, and performing a vacuum treatment on the lower chamber and an inflation treatment on the upper chamber to apply a uniform pressure on the backing layer and achieve a full filling of prepolymers with different viscosities; and after the filling is completed, curing and demolding to obtain the bionic adhesive structure.

Claims

1. A flat-pressing manufacturing method of a bionic adhesive structure based on a micro through-hole nickel-based mold, comprising the following steps: (1) preparing a nickel-based mold with a micro through-hole array; (2) placing the nickel-based mold on an elastic pad in a magnetic mold closing system; (3) coating a prepolymer uniformly on a backing, and placing a side of the backing coated with the prepolymer on the nickel-based mold, covering a sealing diaphragm on the backing to separate a cavity into an upper chamber and a lower chamber, and performing a vacuum treatment on the lower chamber and an inflation treatment on the upper chamber to apply a uniform pressure on the backing and achieve a full filling of cavities of through-holes by the prepolymer; and (4) after the full filling is completed, curing and demolding to obtain the bionic adhesive structure.

2. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein the through-holes of the nickel-based mold in step (1) are cylindrical holes or special-shaped holes, wherein the special-shaped holes are trumpet-shaped holes or wedge-shaped holes, a maximum hole diameter of the through-holes is not greater than 100 μm, a thickness of the nickel-based mold is 20-500 μm, and a hole density of the nickel-based mold is greater than 10,000/cm.sup.2.

3. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein the nickel-based mold has been subjected to an anti-adhesion treatment.

4. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein the magnetic mold closing system in step (2) comprises a magnet and the elastic pad.

5. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 4, wherein a surface roughness Ra of the magnet is less than or equal to 0.05 μm, and a surface finish of the magnet is greater than level 10; and an elastic modulus of the elastic pad is 1 MPa-10 MPa.

6. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein the magnet is a permanent magnet or an electromagnet, and a substrate of the elastic pad is anti-adhesive or a surface of the substrate has been subjected to an anti-adhesion treatment.

7. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein the prepolymer in a liquid state in step (3) is a thermosetting prepolymer or an ultraviolet-curable prepolymer.

8. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein a coating thickness of the prepolymer in step (3) is 400-600 μm, and a magnetically induced pressure of the magnetic mold closing system during the full filling is 0.1-0.5 MPa.

9. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein the demolding in step (4) is to apply force from one side of the backing to tear off the backing uniformly and slowly.

10. The flat-pressing manufacturing method of the bionic adhesive structure based on the micro through-hole nickel-based mold of claim 1, wherein the bionic adhesive structure in step (4) is an elastomer microstructure array with a feature of tip expansion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, a brief introduction to the drawings required in the illustration of the embodiments is presented below. Apparently, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings may be derived according to these drawings without creative work.

(2) FIG. 1 is a flow diagram showing a flat-pressing manufacturing method of a bionic adhesive structure based on a micro through-hole nickel-based mold;

(3) FIG. 2A is a schematic diagram showing a preparation process of a micro through-hole metal-based mold by laser subtractive technology;

(4) FIG. 2B is a schematic diagram showing a preparation process of a micro through-hole metal-based mold by electroforming additive technology;

(5) FIG. 3A is a diagram showing auxiliary modification effects of electroplating time of 1 h on the morphology of through-holes;

(6) FIG. 3B is a diagram showing auxiliary modification effects of electroplating time of 1.5 h on the morphology of through-holes;

(7) FIG. 3C is a diagram showing auxiliary modification effects of electroplating time of 2 h on the morphology of through-holes;

(8) FIG. 3D is a diagram showing auxiliary modification effects of different electroplating time on the morphology of through-holes;

(9) FIG. 4A is a diagram showing effects of induced pressure of 0.3 MPa at the interface on the morphology of the tip surface of mushroom-shaped microstructure;

(10) FIG. 4B is a diagram showing effects of induced pressure of 0.5 MPa at the interface on the morphology of the tip surface of mushroom-shaped microstructure;

(11) FIG. 4C is a diagram showing effects of different induced pressures at the interface on the morphology of the tip surface of mushroom-shaped microstructure; and

(12) FIG. 5 is a diagram showing the morphology of a polyurethane acrylate (PUA) bionic adhesive material prepared by UV curing.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(13) Various exemplary embodiments of the present invention are described below in detail in order to better support the feasibility of the present invention.

(14) In the embodiments of the present invention, the heating curing method is that a heating curing module that can be started independently is installed at the bottom of the lower chamber. The heating curing module heats up and generates heat rapidly after starting, and the heat is radiated or conducted to the mold and the prepolymer, thereby curing the thermosetting prepolymer. The UV curing method is that a UV LED lamp that can be started independently is installed on the top of the upper chamber, and emit UV light downward after starting. Under the action of UV light, the UV-curable prepolymer undergoes a cross-linking and curing reaction. Meanwhile, a part of the UV light can pass through the transparent elastic pad to reach the surface of the magnet, and the surface roughness of the magnet reaches the mirror level, which can reflect the UV light and can assist the curing of the prepolymer in the micro-hole array of the mold. Especially for the tip-expanded structure, the UV light emitted by the light source cannot directly reach the covered area at the bottom, and the UV light reflected by the upper surface of the magnet can supplement the curing of the bottom area.

(15) In the present invention, the backing layer, the filling prepolymer and the cured polymer have good adhesive strength. When demolding, the backing layer can be uniformly and slowly torn off by applying force from one side of the backing layer. The force can be applied manually, mechanically or by air pressure.

Embodiment 1

(16) (1) Preparation of Nickel-Based Mold with Micro Through-Hole Array

(17) The processing of the high-quality and uniform micro through-hole array on the metal substrate can be achieved in two ways, one is the subtractive processing method of spiral drilling with femtosecond laser, and the other is the additive manufacturing method of silicon-based electroforming. The two manufacturing technology solutions are shown in FIGS. 2A-B. FIG. 2A shows the realization of the large-scale micro through-hole nickel-based basic mold by femtosecond laser. FIG. 2B shows the manufacturing method of combining photolithography and electroplating. The processing of micro-column array is realized by selecting the gold-plated silicon wafer, spin-coated photoresist, exposure, developing and cleaning; and then, the nickel-based micro hole array mold is obtained after the electroplating treatment, thinning and demolding.

(18) The electroplating-assisted modification technology of the array micro through-hole metal mold is the main way to control the micro through-hole cavity, which can indirectly realize the control of the side surface of the bionic adhesive microstructure. For the prepared array micro through-hole nickel-based template, after a series of pre-processing procedures, the electroplating nickel-assisted modification process is carried out to achieve the morphology control of the micro through-hole cavity (see FIGS. 3A-D). The obtained nickel-based mold is subjected to an anti-adhesion treatment. In the anti-adhesion treatment process, the pattern side is laid face up on the container, 10 μL/L (chamber volume) anti-adhesive material FOTS (1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane) is taken, vacuum pumped to 10 mbar, sealed and kept for 30 min. The collection container with residual anti-adhesive agent is taken out, then the mold is baked at 130° C. for 30 min, and cooled naturally.

(19) The prepared through-holes of the nickel-based mold with micro through-hole array are cylindrical holes, the maximum hole diameter is 80 μm, the thickness of the nickel-based mold is 20 μm, and the hole density is greater than 10,000/cm.sup.2. The nickel-based mold with micro through-hole array is subjected to an anti-adhesion treatment, and the anti-adhesion treatment includes oxygen plasma treatment and surface fluorination.

(20) (2) The Nickel-Based Mold is Placed on an Elastic Pad in a Magnetic Mold Closing System

(21) The nickel-based mold obtained in the previous step is placed on an elastic pad in a magnetic mold closing system. The magnet body in the magnetic mold closing system is a rubidium iron boron permanent magnet, with an electroplated layer on the outer surface, an upper surface roughness Ra of less than or equal to 0.05 μm, and a surface finish of greater than level 10. The elastic pad is a polyurethane (PU) elastic pad with an elastic modulus of 1 MPa and a thickness of 5 mm. In order not to affect the demolding, the surface of the PU elastic pad is modified with an anti-adhesion layer. The specific steps are as follows: firstly, the surface of the elastic pad is treated with oxygen plasma to oxidize the surface of the rigid structure layer to produce a very thin layer of silica-like material; and then the surface of the template reacts with 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (FOTS) to grow the anti-adhesion layer with low surface energy.

(22) (3) Process Steps for Imprint Filling and Curing

(23) Dow Corning's 184 silicone rubber prepolymer is coated uniformly on a polyethylene terephthalate (PET) backing with a coating thickness of 600 the side of the backing coated with the prepolymer is placed on the nickel-based mold, and the backing is covered with a polydimethylsiloxane (PDMS) sealing diaphragm to separate the cavity into an upper chamber and a lower chamber. The lower chamber is subjected to a vacuum treatment and the upper chamber is filled with N.sub.2 to apply a uniform pressure on the backing layer and achieve a full filling of the hole cavity by the prepolymer. The pressure difference between the two sides of the sealing diaphragm is applied to the backing layer through the sealing diaphragm to provide the driving force for filling the prepolymer. During the imprint filling process, the magnetically induced pressure is 0.3 MPa. After the filling is completed, the prepolymer is cured by a thermal curing module, the curing temperature is 100° C., and the curing time is 10 min.

(24) (4) Demolding Process After Curing

(25) After the curing is completed, the pressure is released and demolding is carried out. The force is applied from one side of the backing layer to tear off the backing layer uniformly and slowly to obtain the bionic adhesive structure with mushroom-shaped microstructure tip face.

(26) In the manufacturing process of the bionic adhesive structure involved in the embodiment, the side surface morphology of the bionic adhesive microstructure depends on the configuration of the through-hole cavity of the metal mold, while the tip surface morphology of the mushroom-shaped microstructure depends on the deformation control of the elastic pad induced by the magnetic pressure. The deformation of the elastic pad with a specific modulus can be induced and controlled by the pressure on the elastic pad.

(27) FIGS. 4A-C shows that for a PU elastic pad, different magnetic induced pressure has a significant effect on the tip face morphology. It is found that the mushroom-shaped microstructures can be effectively obtained under the pressure in the range of 0.1-0.5 MPa, while the formation of mushroom-shaped expended tip is often inhibited when the pressure is outside the range. Moreover, the induced pressure can also regulate the degree of tip face depression, and the tip face depression of bionic microstructure will bring the multi-mechanism synergy effect of adhesion, such as the synergy of negative pressure adsorption and Van der Waals' force dry adhesion, so as to realize the diversity and robustness of interface adhesion functions.

Embodiment 2

(28) (1) Preparation of Nickel-Based Mold with Micro Through-Hole Array, and the Specific Steps are the Same as that in Embodiment 1

(29) The prepared through-holes of the nickel-based mold with micro through-hole array are trumpet-shaped holes, the maximum hole diameter is 50 μm, the thickness of the nickel-based mold is 100 μm, and the hole density is greater than 10,000/cm.sup.2. The nickel-based mold with micro through-hole array is subjected to an anti-adhesion treatment, and the anti-adhesion treatment includes oxygen plasma treatment and surface fluorination.

(30) (2) The Nickel-Based Mold is Placed on an Elastic Pad in a Magnetic Mold Closing System

(31) The nickel-based mold obtained in the previous step is placed on an elastic pad in a magnetic mold closing system. The magnet body in the magnetic mold closing system is a rubidium iron boron permanent magnet, with an electroplated layer on the outer surface, an upper surface roughness Ra of less than or equal to 0.05 μm, and a surface finish of greater than level 10. The elastic pad is a PU elastic pad with an elastic modulus of 10 MPa and a thickness of 5 mm.

(32) (3) Process Steps for Imprint Filling and Curing

(33) The prepolymer in this embodiment is thermoplastic polypropylene (PP). PP film with a thickness of 200 μm is used as a backing, and the PP is uniformly coated on the PP film with a coating thickness of 600 μm. The side of the backing coated with the prepolymer is placed on the nickel-based mold, and the backing is covered with a PU sealing diaphragm to separate the cavity into an upper chamber and a lower chamber. The lower chamber is subjected to a vacuum treatment and the upper chamber is filled with N.sub.2 to apply a uniform pressure on the backing layer and achieve a full filling of the hole cavity by the prepolymer. The pressure difference between the two sides of the sealing diaphragm is applied to the backing layer through the sealing diaphragm to provide the driving force for filling the prepolymer. During the imprint filling process, the magnetically induced pressure is 0.1 MPa. After the sealing diaphragm is pressurized, the PP is heated to 200° C. for softening, and the mold is filled under pressure. After the filling is completed, the prepolymer is cooled to room temperature for curing.

(34) (4) Demolding Process after Curing

(35) After the curing is completed, the pressure is released and demolding is carried out. The force is applied from one side of the backing layer to tear off the backing layer uniformly and slowly to obtain the bionic adhesive structure.

Embodiment 3

(36) (1) Preparation of Nickel-Based Mold with Micro Through-Hole Array, and the Specific Steps are the Same as that in Embodiment 1

(37) The prepared through-holes of the nickel-based mold with micro through-hole array are wedge-shaped holes, the maximum hole diameter is 90 μm, the thickness of the nickel-based mold is 300 μm, and the hole density is greater than 10,000/cm.sup.2. The nickel-based mold with micro through-hole array is subjected to an anti-adhesion treatment, and the anti-adhesion treatment includes oxygen plasma treatment and surface fluorination.

(38) (2) The Nickel-Based Mold is Placed on an Elastic Pad in a Magnetic Mold Closing System

(39) The nickel-based mold obtained in the previous step is placed on an elastic pad in a magnetic mold closing system. The magnet body in the magnetic mold closing system is an electromagnet. The elastic pad is a PU elastic pad with an elastic modulus of 5 MPa and a thickness of 5 mm.

(40) (3) Process Steps for Imprint Filling and Curing

(41) In this embodiment, thermoplastic polyurethane (TPU) particles and a dimethylformamide solution are mixed according to a mass ratio of 1:4 and placed on a constant temperature heating magnetic stirrer, fully stirred at a temperature of 60° C.-80° C. until the TPU particles are completely dissolved in the dimethylformamide solution. After being cooled, a polyurethane transfer medium glue solution is obtained as a prepolymer.

(42) The prepared prepolymer is uniformly coated on a PET backing with a coating thickness of 500 μm by a rubber coating machine. The side of the backing coated with the prepolymer is placed on the nickel-based mold, and the backing is covered with a PU sealing diaphragm to separate the cavity into an upper chamber and a lower chamber. The lower chamber is subjected to a vacuum treatment and the upper chamber is filled with N.sub.2 to apply a uniform pressure on the backing layer and achieve a full filling of the hole cavity by the prepolymer. The pressure difference between the two sides of the sealing diaphragm is applied to the backing layer through the sealing diaphragm to provide the driving force for filling the prepolymer. During the imprint filling process, the magnetically induced pressure is 0.5 MPa. For the TPU prepolymer in this embodiment, the pressure applied by the sealing diaphragm is able to ensure that the prepolymer fully fills the cavity. After the filling is completed, the prepolymer is heated to 100° C. and cured after 0.5 h.

(43) (4) Demolding Process After Curing

(44) After the curing is completed, the pressure is released and demolding is carried out. The force is applied from one side of the backing layer to tear off the backing layer uniformly and slowly to obtain the bionic adhesive structure.

Embodiment 4

(45) (1) Preparation of Nickel-Based Mold with Micro Through-Hole Array, and the Specific Steps are the Same as that in Embodiment 1

(46) The prepared through-holes of the nickel-based mold with micro through-hole array are cylindrical holes, the maximum hole diameter is 60 μm, the thickness of the nickel-based mold is 500 μm, and the hole density is greater than 10,000/cm.sup.2. The nickel-based mold with micro through-hole array is subjected to an anti-adhesion treatment, and the anti-adhesion treatment includes oxygen plasma treatment and surface fluorination.

(47) (2) The Nickel-Based Mold is Placed on an Elastic Pad in a Magnetic Mold Closing System

(48) The nickel-based mold obtained in the previous step is placed on an elastic pad in a magnetic mold closing system. The magnet body in the magnetic mold closing system is an electromagnet. The elastic pad is a PU elastic pad with an elastic modulus of 6 MPa and a thickness of 5 mm.

(49) (3) Process Steps for Imprint Filling and Curing

(50) UV-curable polymer urethane acrylate (PUA) is used as a prepolymer, stirred and mixed uniformly according to a certain ratio (SC2565 (oligomer): M220:M2101=1:0.06:0.15, the additive amount of iGM1173 photoinitiator is 4 wt %) to remove bubbles. The prepared PUA glue solution is uniformly coated on a PET backing with a coating thickness of 400 μm by a rubber coating machine. The side of the backing coated with the prepolymer is placed on the nickel-based mold, and the backing is covered with a PDMS sealing diaphragm to separate the cavity into an upper chamber and a lower chamber. The lower chamber is subjected to a vacuum treatment and the upper chamber is filled with N.sub.2 to apply a uniform pressure on the backing layer and apply a full filling of the hole cavity by the prepolymer. The pressure difference between the two sides of the sealing diaphragm is applied to the backing layer through the sealing diaphragm to provide the driving force for filling the prepolymer. During the imprint filling process, the magnetically induced pressure is 0.4 MPa. After the filling is completed, a UV curing is performed with a curing light source power of 0.5 W/cm.sup.2, and the curing is completed after 60 s of lighting.

(51) (4) Demolding Process After Curing

(52) After the curing is completed, the pressure is released and demolding is carried out. The force is applied from one side of the backing layer to tear off the backing layer uniformly and slowly to obtain the bionic adhesive structure. The morphology of the bionic adhesive structure is shown in FIG. 5.

(53) The above-mentioned embodiments only describe the preferred modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made by those of ordinary skill in the art to the technical solution of the present invention shall fall within the protective scope specified by the claims of the present invention.