CN106892399A - A kind of bionical moisture condensation and collection structure and preparation method thereof - Google Patents

Abstract

The invention proposes a bionic water vapor condensation and collection structure and a preparation method, and the structure is a hydrophilic region and a hydrophobic region composed of specific shapes. The preparation method comprises the steps of spin-coating photoresist, etching silicon oxide layer, preparing hydrophobic region, treating hydrophilic region, preparing condensate drainage channel and the like. The invention utilizes the surface tension of the material instead of gravity, so that the size of the condensate can be collected in a directional manner when the size reaches hundreds of microns or even tens of microns; a special hydrophilic-hydrophobic structure is adopted to expose part of the condensation area and be hindered by the condensate Very small; using silicon nanowires as the structure of the hydrophobic region, the hydrophobic properties of the hydrophobic region can be effectively maintained for a long time; using porous materials as drainage channels, even when placed horizontally, the condensate in the condensate collection area can be quickly and effectively Drain out condensation structures. The invention has the advantages of easy preparation, fast condensation speed and the like, and has broad application prospects.

Description

A bionic water vapor condensation and collection structure and its preparation method

technical field

The present invention belongs to the field of bionic micro-nano manufacturing, and specifically relates to a bionic water vapor condensation and collection structure and a preparation method thereof. This water vapor condensation and collection structure has excellent water vapor condensation characteristics, and can collect water droplets formed by condensation in a directional manner. Efficient water vapor condensation and collection structures provide a solution.

Background technique

During the condensation process, since the condensate is attached to the surface of the condensation structure, the heat exchange process between the moist air and the surface of the condensation structure is hindered. Therefore, in order to obtain a water vapor condensation and collection structure with excellent performance, the condensate formed by condensation must be quickly and effectively separated from the surface of the condensation structure. At present, the industry mainly uses a hydrophobic surface or a super-hydrophobic surface to make the condensate into droplets, and let the condensate surface be inclined or placed vertically. The droplets formed by condensation will break away from the condensation structure under the action of gravity when the volume reaches a certain level. surface. However, in the initial stage of condensation, the condensation effect of the hydrophobic surface is much worse than that of the hydrophilic surface. If the condensate formed on the hydrophilic surface can be quickly shed, a more effective water vapor condensation structure can be obtained.

There are many biological structures with excellent water vapor condensation characteristics in nature. The surface is a hydrophilic or hydrophilic-hydrophobic structure. At the same time, the droplets formed by surface condensation can be collected in a directional manner, quickly detached from the surface of the condensation structure, and start a new condensation process. Such as the surface of beetles in the desert, spider silk, cactus spines and other structures. In 2001, Andrew R. Parker and others pointed out in the journal "Nature" that the excellent water vapor condensation characteristics on the surface of the desert beetle are mainly due to the periodic micro-nano structure between the hydrophilic and hydrophobic phases on the surface, and the droplets formed by condensation on the hydrophobic surface gather into the hydrophilic Area, complete directional collection with the help of wind force. In 2010, Jiang Lei and others reported the spindle structure of spider silk in the journal "Nature". There are wettability gradients and free energy gradients on the surface, which can directionally collect tiny droplets in the morning fog to form large droplets.

At present, there are two main structures for bionic water vapor condensation and collection. One is the conical cactus-like structure, which mainly utilizes the free energy gradient of the liquid drop on the conical surface to condense the liquid at the conical tip. The droplets gather at the bottom of the cone, so that the tip is exposed to the humid air again, and a new condensation process begins; the other is a desert beetle-like surface structure, that is, hydrophilic circular or rectangular arrays are distributed on the hydrophobic surface, The droplets formed by condensation will gather into the hydrophilic area. As the volume of the droplets increases, the droplets in the adjacent hydrophilic areas will merge, leaving a part of the hydrophilic area exposed. This process continues to occur, and the merged formed The volume of condensate droplets continues to increase. When the condensate surface is placed at an angle, large condensate droplets will be separated from the condensate surface under the action of gravity, allowing the condensation process to continue.

The above two bionic water vapor condensation and collection structures have certain limitations. The cactus-like structure is a cone-shaped structure, while the condensation surface used in general industries is a planar structure, and the scale preparation of the cone-shaped structure is difficult; The surface structure of the beetle finally detaches from the surface of the condensing structure under the action of gravity. The condensate is already large enough (usually the size of the condensate reaches several millimeters), which has formed a certain hindrance to the condensation process. In order to make the condensate detach quickly, It is necessary to reduce the proportion of the hydrophilic area, but this also limits the performance of the water vapor condensation and collection structure. In addition, the methods used in the existing technologies to prepare hydrophobic regions generally use self-assembled hydrophobic molecular layers or coating hydrophobic coatings. The surface of the prepared hydrophobic region is prone to be polluted, which will deteriorate the hydrophobic performance and reduce the surface condensation performance. .

Contents of the invention

In view of the above-mentioned technical defects, the present invention provides a bionic water vapor condensation and collection structure and its preparation method. It has high-efficiency water vapor condensation and collection capabilities, good condensation and collection performance, simple preparation method, and easy scale preparation.

A bionic water vapor condensation and collection structure proposed by the present invention is characterized in that, on the silicon substrate, a silicon oxide hydrophilic region is processed, and the thickness of the silicon oxide is 200-800nm; other areas on the surface of the silicon substrate are made of superhydrophobic silicon nanowire structure.

Further, the shape of the hydrophilic region of the structure of the condensation and collection structure is a wedge-shaped array of several isosceles triangles linearly arranged, or a hub-shaped array of isosceles triangles whose spokes are; wherein: the wedge-shaped array is equal to The bases of the waist triangles are arranged in a collinear manner, and the distance between each triangle is equal; the other side of the base line of each triangle is the condensate collection area; The bisectors are arranged at equal angles; the inner area of the inner circle of the hub is a condensate collection area; the base of the collection area is silicon oxide, and/or the drainage channel is made of porous material.

Correspondingly, the present invention proposes a bionic water vapor condensation and collection structure, which is characterized in that it includes the following steps:

(1) Spin-coat photoresist on the surface of the substrate, expose and develop through a photolithography mask, and form a sample; the substrate is a silicon wafer with a silicon oxide layer on the surface, and the pattern of the mask is several isosceles triangles A wedge-shaped array arranged linearly, or a hub-shaped array whose spokes are isosceles triangles;

The wedge-shaped array is formed by collinear arrangement of the bases of isosceles triangles, and the spacing of each triangle is equal; the other side of the bottom line of each triangle is a condensate collection area;

The hub array is arranged in a way that the base of an isosceles triangle is tangent to the inner circle of the hub and is arranged at equal angles according to the bisector of the apex angles of each triangle; the inner area of the inner circle of the hub is a condensate collection area;

(2) Etching the silicon oxide layer: etching the sample prepared in step (1), so that the silicon oxide layer not protected by the photoresist is etched to expose silicon;

(3) Preparation of hydrophobic region: etching the sample processed in step (2), and preparing a superhydrophobic silicon nanowire structure surface in the region not protected by photoresist; generally speaking, superhydrophobic surface generally refers to the surface contact angle Greater than 150°.

(4) Removal of photoresist: Put the sample obtained in step (3) into glue removal solution or acetone solution, perform ultrasonic cleaning, then clean it with deionized water, and dry it with a nitrogen gun to make the silicon oxide on the surface of the sample exposed layer

(5) Preparation of condensate drainage channels: use porous materials to prepare drainage channels in the condensate collection area, and drain the condensate in the condensate collection area out of the sample surface; the porous materials include chemical fibers and metal oxide nanowire network structures Or the foam metal material that has been treated with hydrophilicity.

Further, in the preparation method of the bionic water vapor condensation and collection structure, the vertex angle of a single triangle in the hub-shaped array in step (1) is 0.5-3°, the height is 0.5-2cm, and the adjacent sides of each triangle The minimum pitch is 0-300μm.

Further, in the preparation method of the biomimetic water vapor condensation and collection structure, the etching preparation of the hydrophobic region adopts the inductively coupled plasma method, and the parameters of the inductive plasma etching are: the radio frequency power is 20±2W, and the plasma coupling power 700±50W, air pressure 10±1mTorr, gas flow SF ₆ =17±2sccm, C ₄ F ₈ =30±5sccm.

Further, in the preparation method of the biomimetic water vapor condensation and collection structure, the etching solution used in step (2) is a mixed solution of hydrofluoric acid and ammonium fluoride, wherein the mass fraction of hydrofluoric acid in the mixed solution is 5- 10%, the mass fraction of ammonium fluoride is 15-20%.

Further, in the preparation method of the biomimetic water vapor condensation and collection structure, the thickness of the silicon nanowire structure prepared in the step (3) is 0.5-3 μm;

Further, in the preparation method of the biomimetic water vapor condensation and collection structure, the thickness of the silicon oxide layer is 200-800nm.

Further, in the preparation method of the biomimetic water vapor condensation and collection structure, the surface of the silicon oxide layer is treated with a hydrofluoric acid solution with a mass fraction of 0.5-1%, so that the silicon oxide layer structure has better hydrophilicity.

Further, in the biomimetic water vapor condensation and collection structure and its preparation method, the base of the collection area is silicon oxide, and/or the drainage channel is made of porous material.

Compared with the existing technical solutions, the above technical solutions conceived by the present invention have the following characteristics and excellent effects due to the use of special structures and new principles to prepare bionic water vapor condensation and collection structures:

(1) The present invention adopts a special hydrophilic-hydrophobic interphase structure, and uses surface tension instead of gravity to complete the directional collection of condensate, so that the condensate can be collected directionally when the size of the condensate reaches hundreds of microns or even tens of microns, so that the partial condensation area Exposed to start a new condensation process, little hindered by condensate;

(2) Using the structure prepared by the method used in the present invention, the surface contact angle of the hydrophilic region is less than 8°, and the surface contact angle of the hydrophobic region is greater than 150°;

(3) The present invention adopts inductively coupled plasma etching technology to prepare silicon nanowires as the structure of the hydrophobic region, and the hydrophobic characteristics are derived from the characteristics of silicon nanowires. At the same time, the surface of the nanowire structure prepared by this method has a layer of fluorine-based compound, which is hydrophobic. The hydrophobic properties of the region (1) can be effectively maintained for a long time;

(4) The present invention uses a porous material as a drainage channel. Since the porous material has very good water absorption performance, it can quickly and effectively drain the condensate in the condensate collection area out of the condensate structure even when it is placed horizontally.

Description of drawings

Figure 1(a) is a schematic diagram of the bionic water vapor condensation and collection structure of the linearly distributed wedge array;

Figure 1(b) is a schematic diagram of the bionic water vapor condensation and collection structure of the hub-shaped wedge-shaped array;

In the figure, 1 is a hydrophobic area, 2 is a hydrophilic wedge array, 3 is a condensate collection area, and 4 is a drainage channel.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

In the embodiment, the condensation and collection structure is processed with a silicon oxide hydrophilic region on the silicon substrate, and other regions on the surface of the silicon substrate are made with a superhydrophobic silicon nanowire structure; the shape of the hydrophilic region is a number of isosceles triangle linear Arranged wedge arrays, or hub-shaped arrays whose spokes are isosceles triangles; wherein: a single wedge refers to an isosceles triangle with a very small apex angle, and the wedge array is formed by collinear arrangement of the bases of the isosceles triangles, The distance between each triangle is equal; the other side of the bottom line of each triangle is the condensate collection area, and the condensate collection area is provided with a drainage channel outward; Angle bisectors are arranged at equal angles; the inner area of the inner circle of the hub is the condensate collection area, and the condensate collection area is provided with a drainage channel outward. The apex angle of the triangle is 0.5-3°, the height is 0.5-2cm, and the minimum distance between adjacent sides of each triangle is 0-300μm. In the present invention, the thickness of the silicon nanowire structure is 0.5-3 μm, and the thickness of silicon oxide is 200-800 nm;

The drainage channel is made of porous materials. The present invention adopts hydrophilic porous polyacrylonitrile fibers, copper oxide nanowire nets prepared by growth, porous copper foam after hydrophilic treatment and PET foam fibers as porous materials. Other types of porous materials are also practical.

By etching the silicon wafer with a silicon oxide layer on the surface, the silicon is exposed to form a silicon substrate with a condensation and collection structure, and then a super-hydrophobic silicon nanowire structure surface is prepared on the silicon substrate to form a hydrophilic region; by The rest of the silicon wafer covered by the wedge array or the hub array, the photoresist is removed to obtain the hydrophobic region. The specific steps are:

(1) Spin-coat photoresist on the surface of the substrate, expose and develop through a photolithography mask, and form a sample; the substrate is a silicon wafer with a silicon oxide layer on the surface;

(2) Etching the silicon oxide layer: etching the sample prepared in step (1), so that the silicon oxide layer not protected by the photoresist is etched to expose silicon;

(3) Preparation of hydrophobic regions: etching the sample processed in step (2), and preparing a superhydrophobic silicon nanowire structure surface in the region not protected by photoresist;

(4) remove the photoresist: remove the photoresist on the sample obtained by step (3) to expose the silicon oxide layer on the sample surface;

(5) Preparation of a condensate drainage channel: a porous material is used to prepare a drainage channel in the condensate collection area, and the condensate in the condensate collection area is drained out of the surface of the sample.

The method of etching to prepare the hydrophobic area is the inductively coupled plasma method. The etching parameters are: RF power is 20±2W, plasma coupling power is 700±50W, air pressure is 10±1mTorr, gas flow SF ₆ =17±2sccm, C ₄ F ₈ =30±5 sccm. The etching solution used for etching the silicon oxide layer is a mixed solution of hydrofluoric acid and ammonium fluoride, wherein the mass fraction of hydrofluoric acid in the mixed solution is 5-10%, and the mass fraction of ammonium fluoride is 15-20%. The method for removing the photoresist is as follows: put the sample in the glue remover or acetone solution, perform ultrasonic cleaning, then clean it with deionized water, and dry it with a nitrogen gun.

Further, the surface of the silicon oxide layer is treated with a hydrofluoric acid solution with a mass fraction of 0.5-1%, so that the structure of the silicon oxide layer has better hydrophilicity.

Embodiment one

(1) Preparation of photoresist pattern: spin-coat PR1-1000 photoresist on the surface of the substrate, and expose and develop; wherein the substrate is a silicon wafer with a silicon oxide layer on the surface, and the thickness of the silicon oxide layer is 200; the prepared photoresist The resist pattern is a wedge-shaped array (2) and a condensate collection area (3). The wedge-shaped structures are distributed in a linear array. The length of a single wedge-shaped (isosceles triangle with a small apex angle) structure is 2 cm, and the distance between adjacent wedges is 200 μm. The angle is 1°;

(2) Etching the silicon oxide layer: using a mixed solution of hydrofluoric acid and ammonium fluoride to etch the sample prepared in step (1), so that the silicon oxide layer not protected by the photoresist is completely etched, and the silicon is exposed; The massfraction of hydrofluoric acid in the mixed solution is 5%, and the massfraction of ammonium fluoride is 15%;

(3) Hydrophobic region (1) was prepared by inductively coupled plasma etching (ICP etching): the sample treated in step (2) was etched by ICP, and superhydrophobic silicon was prepared in the area not protected by photoresist. The surface of nanowire structure; where the parameters of ICP etching are: radio frequency power RF=20W, plasma coupling power ICP=700W, air pressure P=10mTorr, gas flow SF ₆ =17 sccm, C ₄ F ₈ =30 sccm, silicon nanometer The thickness of the wire structure is 0.5 μm;

(4) Removal of photoresist: Put the sample obtained in step (3) into an acetone solution for ultrasonic cleaning for 10 minutes, then wash it with sufficient deionized water, and dry it with a nitrogen gun to expose the silicon oxide layer on the surface of the sample ;

(5) Hydrophilic area treatment: soak the sample obtained in step (4) in a hydrofluoric acid solution with a mass fraction of 0.5% for 2 minutes to remove the contaminated surface of the silicon oxide layer and keep the structure of the silicon oxide layer hydrophilic.

(6) Preparing a condensate drainage channel (4): using hydrophilic porous polyacrylonitrile fibers to prepare a drainage channel (4) on the condensate collection area (3);

Embodiment two, three, four

Referring to the operation steps of the implementation case 1, change the corresponding parameters to the parameters shown in the table below to obtain the implementation cases 2, 3, and 4

Because the droplets formed by condensation will break away from the surface of the condensation structure under the action of gravity when the volume reaches a certain level. However, in the initial stage of condensation, the condensation effect of the hydrophobic surface is much worse than that of the hydrophilic surface. If the condensate formed on the hydrophilic surface can be quickly shed, a more effective water vapor condensation structure can be obtained.

When the droplet is on a wedge-shaped (isosceles triangle with a small vertex) surface or a wedge-shaped groove placed horizontally, the horizontal forces on both ends of the droplet are:

Among them, F ₁ and F ₂ are the component forces acting on the surface tension at both ends in the horizontal direction, γ is the surface tension of the liquid, θ is the contact angle between the liquid and the contact surface, and L ₁ and L ₂ are the effective length of the contact line at both ends. Obviously, the contact line lengths at both ends of the wedge-shaped region are not the same, so the droplet will be subjected to a horizontal driving force F=γcosθ(L ₂ -L ₁ ), and the magnitude of the driving force is related to the angle between the two sides of the wedge, that is, the wedge angle β.

Based on the above theoretical basis, the present invention proposes an efficient method for preparing a water vapor condensation and collection structure. Through this method, the condensate formed by condensation is directionally collected under the action of surface tension, quickly detaches from the surface of the condensation structure and starts a new condensation process.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (10)

1. A biomimetic water vapor condensation and collection structure, characterized in that, on the silicon substrate, a silicon oxide hydrophilic region is processed, and the silicon oxide thickness is 200-800nm; other regions on the surface of the silicon substrate are made of superhydrophobic silicon nanowires Structure; the shape of the hydrophilic region is a wedge-shaped array of several isosceles triangles linearly arranged, or the spokes are a hub-shaped array of isosceles triangles; wherein: The wedge-shaped array is formed by collinear arrangement of the bases of isosceles triangles, and the distance between each triangle is equal; the other side of the bottom line of each triangle is a hydrophilic condensate collection area, and the condensate collection area is provided with a drainage channel outward; The hub array is arranged in a tangent manner around the inner circle of the isosceles triangle around the inner circle of the hub, and arranged at equal angles according to the bisector of the apex angles of each triangle; the inner area of the inner circle of the hub is a hydrophilic condensate collection area, and the condensate There is a drainage channel outside the collection area. 2. The biomimetic water vapor condensation and collection structure according to claim 1, characterized in that, the substrate of the collection area is silicon oxide, and/or the drainage channel is made of porous material. 3. a preparation method of bionic water vapor condensation and collection structure, is characterized in that, comprises the steps: (1) Spin-coat photoresist on the surface of the substrate, expose and develop through a photolithography mask, and form a sample; the substrate is a silicon wafer with a silicon oxide layer on the surface; (2) Etching the silicon oxide layer: etching the sample prepared in step (1), so that the silicon oxide layer not protected by the photoresist is etched to expose silicon; (3) Preparation of hydrophobic regions: etching the sample processed in step (2), and preparing a superhydrophobic silicon nanowire structure surface in the region not protected by photoresist; (4) remove the photoresist: remove the photoresist on the sample obtained by step (3) to expose the silicon oxide layer on the sample surface; (5) Preparation of a condensate drainage channel: a porous material is used to prepare a drainage channel in the condensate collection area, and the condensate in the condensate collection area is drained out of the surface of the sample. 4. the preparation method of bionic water vapor condensation and collection structure according to claim 3, is characterized in that, the pattern of described mask is the wedge-shaped array that several isosceles triangles are linearly arranged, or the spoke is the wheel hub of isosceles triangles shape array; where: The wedge-shaped array is formed by collinear arrangement of the bases of isosceles triangles, and the distance between each triangle is equal; the other side of the bottom line of each triangle is a condensate collection area, and a drainage channel is opened outward in the condensate collection area; The hub array is arranged in a way that the base of an isosceles triangle is tangent to the inner circle of the hub and is arranged at equal angles according to the bisector of the apex angles of each triangle; There is a drainage channel. 5. The biomimetic water vapor condensation and collection structure according to claim 3 or 4, characterized in that, the base of the collection area is silicon oxide, and/or the drainage channel is made of porous material. 6. according to the preparation method of claim 3 or 4 described biomimetic water vapor condensation and collection structure, it is characterized in that, the vertex angle of described triangle is 0.5-3 °, height is 0.5-2cm, the minimum of adjacent sides of each triangle The pitch is 0-300μm. 7. The method for preparing the biomimetic water vapor condensation and collection structure according to claim 3 or 4, wherein the etching preparation of the hydrophobic region adopts an inductively coupled plasma method, and the etching parameters are: the radio frequency power is 20 ± 2W, the plasma coupling power is 700±50W, the air pressure is 10±1mTorr, the gas flow SF ₆ =17±2sccm, C ₄ F ₈ =30±5sccm; and/or step (4) removes the photoresist method is: the sample Put it in glue remover or acetone solution, clean it ultrasonically, clean it with deionized water, and dry it with a nitrogen gun. 8. according to the preparation method of claim 3 or 4 described biomimetic water vapor condensation and collection structure, it is characterized in that, the etching solution that adopts in step (2) is hydrofluoric acid and ammonium fluoride mixed solution, wherein in mixed solution The mass fraction of hydrofluoric acid is 5-10%, and the mass fraction of ammonium fluoride is 15-20%. 9. according to the preparation method of the described biomimetic water vapor condensation and collection structure of claim 3 or 4, it is characterized in that, step (5) described porous material comprises chemical fiber, metal oxide nanowire network structure or through hydrophilic treatment The metal foam material, and/or the thickness of the silicon nanowire structure prepared in the step (3) is 0.5-3 μm. 10. according to the preparation method of the described biomimetic water vapor condensation and collection structure of claim 3 or 4, it is characterized in that, use the hydrofluoric acid solution treatment silicon oxide layer surface that the mass fraction is 0.5-1%, make silicon oxide layer structure have Better hydrophilicity.