CN113441099B

CN113441099B - Nondestructive transfer liquid drop surface, preparation method and nondestructive transfer liquid drop method

Info

Publication number: CN113441099B
Application number: CN202110718529.7A
Authority: CN
Inventors: 刘明; 陈少华; 彭志龙; 姚寅; 张博
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2022-05-06
Anticipated expiration: 2041-06-28
Also published as: NL2032293B1; CN113441099A

Abstract

The invention discloses a lossless transfer liquid drop surface, a preparation method and a lossless transfer liquid drop method, and relates to the technical field of liquid drop transfer. The nondestructive transfer liquid drop surface, the preparation method and the nondestructive transfer liquid drop method provided by the invention can freely grab and release the liquid drop, and realize the nondestructive transfer of the liquid drop.

Description

Nondestructive transfer liquid drop surface, preparation method and nondestructive transfer liquid drop method

Technical Field

The invention relates to the technical field of liquid drop transfer, in particular to a liquid drop surface transfer without damage, a preparation method and a liquid drop transfer without damage.

Background

The organism in the nature coordinates and complements the structure and the function through long-term evolution, and shows a plurality of special surface infiltration performances. For example, the super-hydrophobic self-cleaning property of the lotus leaf surface, the super-hydrophobic high-adhesion property of the rose petal surface and the like. The common characteristic of the special wetting performance is realized by assembling multilayer micro-nano structures forming the surface. Therefore, by designing and preparing multilevel microstructure arrays with different morphologies on the surface of a material, special surface wettability is given to the material, which has attracted extensive attention of researchers.

The research on the water drop transfer or transport functional surface is a research hotspot of the design and preparation direction of bionic material mechanics and functionalized surfaces, is also the leading edge of the subject, and has been rapidly developed in recent years. The traditional research for constructing a typical wettability surface mostly focuses on constructing microstructure arrays with different levels and appearances on the surface of a material, and once the surface micro-appearances are formed, the wettability of the surface becomes a fixed attribute and cannot be adjusted. For example, a water drop exhibits a Cassie state on the surface of lotus leaves and cannot be grabbed, and exhibits a highly adhesive Wenzel state on the surface of rose petals and cannot achieve nondestructive release.

Therefore, the single surface wettability cannot meet the requirements of the intelligent material surface in the future. The design and preparation of the functional surface capable of grabbing and releasing the liquid drops at will are the development trend of the direction, and the functional surface for realizing the lossless transportation of the liquid drops is inevitably the development trend of the direction.

In the prior art, a surface with the adhesive force of 59.8 mu N is prepared by utilizing carbon nanotubes, each square millimeter of the surface is provided with more than 6000000 carbon nanotubes, and when a liquid drop is transferred, the liquid drop can only be transferred to the surface with stronger adhesive force, so that the free grabbing and releasing of the liquid drop by the surface cannot be realized. In the prior art, magnetic particles and polymers are used for preparing a magnetic film, a random microstructure is generated on the surface of the film under the action of a magnetic field, the adhesion force of a liquid drop can be switched between 30 mu N and 120 mu N by regulating the geometric dimension of the microstructure, the grabbing and releasing of the liquid drop can be realized by utilizing the change of the adhesion force, but the surface can cause 3% loss of the liquid drop in the process of transferring the liquid drop, and energy waste or surface pollution is easily generated in practical application. From the above analysis, the existing surface that can be used for transferring liquid droplets cannot realize the nondestructive transfer of liquid droplets.

Disclosure of Invention

The invention aims to provide a liquid drop surface and a preparation method thereof as well as a liquid drop lossless transfer method, which are used for solving the problems in the prior art, can freely grab and release liquid drops and realize the lossless transfer of the liquid drops.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a lossless transfer liquid drop surface, which comprises a substrate, wherein a plurality of micro-flat plates are sequentially arranged on the surface of the substrate at intervals, a plurality of grooves are formed in the same side surface of each micro-flat plate, a plurality of protrusions are formed in the other side surface of each micro-flat plate, one end of each protrusion extends to the top surface of the micro-flat plate where the protrusion is located, each micro-flat plate is an elastic micro-flat plate, each micro-flat plate can synchronously swing between a first position and a second position under the action of an external magnetic field, the first position is the position when the micro-flat plate is vertical to the surface of the substrate, and the second position is the position when the micro-flat plate swings from the first position to the surface layer of the groove.

Preferably, a plurality of grooves are distributed on the same side surface of each micro-flat plate in an array mode, and each groove is a rectangular groove or a circular groove.

Preferably, a plurality of the protrusions are distributed on the other side surface of each micro flat plate in an array manner, the protrusions are rectangular strip-shaped protrusions, and the rectangular strip-shaped protrusions are perpendicular to the top surface of the micro flat plate in the first position.

Preferably, a plurality of magnetic particles are uniformly distributed in each micro-flat plate.

Preferably, the micro-flat plate is made of polydimethylsiloxane.

Preferably, the size of the micro-plate is 5mm × 0.12mm × 1mm, and the distance between two adjacent micro-plates is 1 mm.

Preferably, the size of the micro-plate is 5mm × 0.12mm × 0.5mm, and the distance between two adjacent micro-plates is 0.5 mm.

The invention also provides a preparation method of the surface of the lossless transfer liquid drop, which comprises the following steps:

s1: manufacturing a template consistent with the surface appearance of the lossless transfer liquid drop, and sequentially carrying out ultrasonic cleaning and silanization treatment;

s2: pouring a curable elastic material on the template, and stripping the curable elastic material from the template after curing to obtain an intermediate template with the surface appearance opposite to that of the template, wherein grooves corresponding to the micro-slabs are formed in the intermediate template;

s3: performing silanization treatment on the intermediate template, and pouring and forming each micro-slab by adopting curable elastic material added with magnetic particles in grooves corresponding to each micro-slab on the intermediate template to obtain the surface of a composite structure;

s4: and casting and forming the substrate on the surface of the composite structure by adopting a curable elastic material without containing magnetic particles, placing the substrate in a magnetic field, arranging the magnetic particles in a chain shape along magnetic induction lines under the action of the magnetic field, and stripping the substrate without containing the magnetic particles and each micro-slab containing the magnetic particles on the surface of the substrate from the middle template after curing to obtain the surface of the lossless transfer liquid drop.

The invention also provides a lossless droplet transfer method based on the lossless droplet transfer surface, which comprises the following steps:

(1) moving the non-marring transferred drop surface of the microplate in the second position downwardly into contact with a target drop;

(2) after the nondestructive transfer liquid drop surface grabs the target liquid drop through the micro-flat plate, the nondestructive transfer liquid drop surface starts to move upwards, and then the nondestructive transfer liquid drop surface adhered with the target liquid drop is moved to be above a target position;

(3) and regulating the magnetic field to gradually swing the micro-slab at the second position to the first position, so that the target liquid drop is released to the target position without damage.

Compared with the prior art, the invention has the following technical effects:

the invention provides a nondestructive transfer liquid drop surface and a preparation method thereof and a nondestructive transfer liquid drop method, an elastic micro-flat plate can generate bending deformation under the action of a magnetic field to swing, when the micro-flat plate is at a second position, a groove on the micro-flat plate is positioned on a surface layer, at the moment, the surface adhesion is improved due to the arrangement of the groove, the nondestructive transfer liquid drop surface is in a high-adhesion infiltration state, a target liquid drop can be adhered to the nondestructive transfer liquid drop surface under the high-adhesion infiltration state, after the nondestructive transfer liquid drop surface adhered with the target liquid drop is moved to the position above the target position, the micro-flat plate at the second position is gradually swung to the first position through the regulation and control of the magnetic field, as the top surface of the micro-flat plate is positioned on the surface layer at the first position, at the moment, the surface adhesion is lower, the nondestructive transfer liquid drop surface is in a low-adhesion infiltration state, and the nondestructive transfer liquid drop surface can be switched from the high-adhesion infiltration state to the low-adhesion infiltration state, under the low-adhesion wetting state, the target liquid drop can be released to a target position without damage, so that the liquid drop can be transferred without damage.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic perspective view of a surface of a liquid droplet to be transferred without damage in accordance with a first embodiment;

FIG. 2 is a schematic view of another perspective structure of the surface of the liquid droplet without damage in the first embodiment;

FIG. 3 is a scanning electron micrograph of the left side of a microplate in the surface of a non-destructive transfer droplet provided by the present invention;

FIG. 4 is a scanning electron microscope image of the right side of a microplate in the surface of a non-destructive transfer droplet provided by the present invention;

FIG. 5 is a scanning electron micrograph of the top surface of a microplate in the surface of a non-destructive transfer droplet provided by the present invention;

FIG. 6 is a process diagram of a method for making a non-destructive transfer droplet surface according to the present invention;

FIG. 7 is a schematic diagram of the bending deformation of a single microplate in the surface of a non-destructive transfer drop provided by the present invention under the action of a magnetic field;

FIG. 8 is a schematic view of the bending deformation of the surface of a non-destructive transfer drop in a uniform magnetic field provided by the present invention;

FIG. 9 is a schematic view of a microplate without magnetic particles therein, wherein the microplate is not subjected to bending deformation when the magnetic field is rotated;

FIG. 10 is a schematic view of the surface topography of a microplate on the surface of a non-destructive transfer drop provided by the present invention when fully flexed;

FIG. 11 is a schematic view of an inverted adhering drop on the surface of an undamaged transfer drop when the microplate is fully flexed;

FIG. 12 is a schematic diagram illustrating the principle analysis of the surface of the microplate having grooves with high adhesion;

FIG. 13 is a graph showing the effect of the water droplet release process test using the surface of the non-destructive transfer droplet in the first embodiment;

FIG. 14 is the drawing of FIG. 13 instantaneous contact angle in Water drop Release Process experiment

And

a graph of variation with bend angle θ;

FIG. 15 is a diagram showing the effect of the experiment of the water droplet release process using the surface of the non-destructive transfer droplet of the second embodiment;

FIG. 16 is a graph of the experimental effect of non-destructive release that cannot be achieved without the rectangular bar-shaped protrusion on the right side of the microplate;

FIG. 17 is an effect diagram of an experimental process for non-destructive transfer of water droplets using the non-destructive transfer droplet surface provided by the present invention;

in the figure: 100-no damage transfer liquid drop surface, 1-substrate, 2-micro-flat plate, 3-groove, 4-protrusion, 5-magnetic particle, 6-template, 7-middle template, 8-glass slide.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a liquid drop surface and a preparation method thereof as well as a liquid drop lossless transfer method, which are used for solving the problems in the prior art and can freely grab and release liquid drops to realize the lossless transfer of the liquid drops.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

Example one

As shown in fig. 1 to 5, the present embodiment provides a lossless transfer droplet surface 100, which includes a substrate 1, a plurality of micro-plates 2 are sequentially arranged on the surface of the substrate 1 at intervals, a plurality of grooves 3 are disposed on the same side surface of each micro-plate 2, a plurality of protrusions 4 are disposed on the other side surface of each micro-plate 2, one end of each protrusion 4 extends to the top surface of the micro-plate 2 where the protrusion is disposed, each micro-plate 2 is an elastic micro-plate, each micro-plate 2 can synchronously swing between a first position and a second position under the action of an external magnetic field, the first position is a position where the micro-plate 2 is perpendicular to the surface of the substrate 1, and the second position is a position where the micro-plate 2 swings from the first position to a position where the groove is located on the surface layer.

When the device is used, the surface 100 of the lossless transfer liquid drop is placed in a uniform magnetic field, the magnetic field is regulated, the elastic micro-flat plate 2 generates bending deformation under the action of the magnetic field and swings, the micro-flat plate 2 is positioned at the second position, at the moment, the groove 3 on the micro-flat plate 2 is positioned on the surface layer, the surface adhesion force is improved due to the arrangement of the groove 3, the surface 100 of the lossless transfer liquid drop is in a high-adhesion infiltration state, then the surface 100 of the lossless transfer liquid drop is inverted and moves downwards to contact the target liquid drop to be transferred, the target liquid drop is adhered to the surface 100 of the lossless transfer liquid drop, then the surface 100 of the lossless transfer liquid drop starts to move upwards and moves to the position above the target position, and then the magnetic field is regulated, so that the micro-flat plate 2 at the second position is gradually changed to the first position, and as the top surface of the micro-flat plate 2 is positioned on the surface layer at the first position, at the moment, the surface adhesion force is lower, the lossless transfer droplet surface 100 is in a low adhesion wetting state, so that the lossless transfer droplet surface 100 is switched from a high adhesion wetting state to a low adhesion wetting state, and the target droplet is released to the target position in a lossless manner in the low adhesion wetting state, thereby realizing lossless transfer of the droplet.

In the present embodiment, the micro-plates 2 are arranged in an array, and when the micro-plates 2 are at the first position, the ratio of the height of the micro-plate 2 to the distance between two adjacent micro-plates 2 is preferably 1, so that the micro-plates 2 will not affect each other when being bent.

As shown in fig. 1, in the present embodiment, a plurality of grooves 3 are uniformly distributed on the same side surface of each micro-plate 2 in an array manner, each groove 3 is a rectangular groove or a circular groove, in the present embodiment, each groove 3 is a rectangular groove, and by providing a plurality of grooves 3, the adhesion of the surface to liquid drops can be improved. The principle of high surface adhesion is as follows: as shown in fig. 12, taking the groove 3 as a rectangular groove as an example, the arc-shaped dotted line at the opening of the rectangular groove represents a part where the droplet is pressed on the groove, which is called a three-phase contact line (TPCL), and the three-phase contact line represents a contour line of a contact area between the droplet and the surface of the material; the TPCL has a certain radian, so that Laplace pressure delta p pointing to the concave surface of the dotted line can be generated, liquid drops keep balance under the action of gravity mg and the Laplace pressure delta p, and the grooves are covered by the liquid drops, so certain air is sealed in the grooves; when a force F is applied to separate the water drops from the surface of the groove, the volume of sealed air (sealed air) is increased to generate negative pressure, so that the TPCL changes from a concave surface to a convex surface, the Laplace pressure delta p direction also changes, and at the moment, if the liquid drops are separated from the surface, a larger force F needs to be applied, namely, the surface adhesion force is improved.

As shown in fig. 2, in the present embodiment, a plurality of protrusions 4 are uniformly distributed on the other side surface of each micro-plate 2 in an array, each protrusion 4 is a rectangular strip-shaped protrusion, the rectangular strip-shaped protrusion is perpendicular to the top surface of the micro-plate 2 at the first position, and the rectangular strip-shaped protrusion extends to the top surface of the micro-plate 2, so that one end of the top surface of the micro-plate 2 is in a continuous concave-convex shape, thereby increasing the length of the TPCL and further increasing the adhesion force.

As shown in fig. 7 to 9, in the present embodiment, a plurality of magnetic particles 5 are uniformly distributed in each micro-plate 2, the surface 100 of the liquid drop to be transferred without damage is placed in a uniform magnetic field, the magnetic field is rotated, the magnetic particles 5 inside the micro-plate 2 are subject to magnetic moment under the action of the magnetic field, the micro-plate 2 is bent and deformed, and the substrate 1 correspondingly generates a couple to resist the bending and deformation of the micro-plate 2. As shown in fig. 7, assuming that the angle between the direction of the magnetic field B and the vertical direction is α, the magnetic moment experienced by the whole micro-slab 2 is M, the tilt angle thereof is θ, and the couple generated by the substrate 1 is T, because M and T are acting force and reacting force, M is T, and M has the following expression:

M＝VP_m×B (1)

wherein V represents the microplate volume, P_mRepresents saturation magnetization, and B represents magnetic flux of applied magnetic fieldDensity.

Writing equation (1) as a scalar:

M＝VP_mBsin(α-θ) (2)

from the fact that the couple T is proportional to θ, and M ═ T, it can be seen that:

kθ＝VP_mBsin(α-θ) (3)

wherein k is a proportionality coefficient and alpha is a magnetic field rotation angle.

The saturation magnetization P of the magnetic particles in the present invention can be found by measuring the hysteresis loop of the magnetic particles in experiments_mIs 4.6emu/mm³. The experiment measured a set of data, alpha 30 deg., theta 25 deg., and P_mIn the formula, k is 0.02. Thus, it can be seen that:

based on equation (4), by controlling the angle α of the magnetic field rotation, the bending deformation of the micro-plate can be accurately controlled.

As shown in fig. 8, the bending deformation of the surface 100 of the non-destructive transfer drop in a uniform magnetic field is schematically illustrated; as shown in fig. 9, if the microplate does not contain magnetic particles, the microplate does not undergo bending deformation when the magnetic field is rotated.

In the present embodiment, the micro-plate 2 is made of polydimethylsiloxane, but the micro-plate is not limited to polydimethylsiloxane (abbreviated as PDMS), and other elastic materials may be selected for the micro-plate.

As shown in fig. 1 to 2, in the present embodiment, the micro-slabs 2 have a size of 5mm × 0.12mm × 1mm in length × thickness × height, and the distance between two adjacent micro-slabs 2 is 1mm, wherein a rectangular groove array having a size of 60 μm × 60 μm × 50 μm in length × width × depth is provided on the left side surface of the micro-slab 2, and a rectangular stripe-shaped protrusion array having a size of 100 μm × 50 μm × 1000 μm in length × width × height is provided on the right side surface.

The complete droplet transfer process comprises two parts, grabbing and releasing, in this example the droplet is specifically chosen to be a water droplet.

A first part: snatch water droplet

The surface 100 of the lossless transfer liquid drop can be grabbed by having high adhesion to the water drop, the structure of the micro-flat plates 2 on the surface 100 of the lossless transfer liquid drop is completely bent by utilizing magnetic field regulation, namely theta is approximately equal to 90 degrees, as the left side of each micro-flat plate 2 is fully distributed with a micro-scale rectangular groove, the appearance of the whole surface is shown in figure 10, and the adhesion to the water drop is measured in the experiment to be up to 252 mu N; as shown in fig. 11, a water droplet is placed on the surface 100 of the intact transfer droplet, and the water droplet still does not fall off because the surface 100 of the intact transfer droplet is inverted due to strong adhesion. When the microplate 2 was not subjected to bending deformation and remained in the initial upright state, the adhesion of the top of the single microplate 2 to a water droplet was experimentally determined to be 57 μ N.

A second part: releasing water droplets

The surfaces that can be used to transfer water droplets in the prior art can cause a portion of the water droplets to remain on the surface when the water droplets are released, resulting in energy waste or surface contamination. The invention skillfully utilizes the relation between the instantaneous contact angle and the receding angle (the receding angle is the inherent property of the surface, the advancing angle is a fixed value when the surface microstructure is fixed) of the water drop and the micro-flat plate, and realizes the lossless release of the water drop. FIG. 13 is a graph showing the effect of the experiment of releasing water droplets, in which 10. mu.L of water droplets were first caught by two completely bent microplates, and then the magnetic field was rotated to gradually restore the bent microplates to the original vertical state, as shown in FIG. 13(a), and the contact state of the water droplets and the two microplates is shown in FIG. 14, in which

And

the instantaneous contact angles of the water drop and the left-side micro-flat plate and the right-side micro-flat plate are respectively shown, and the instantaneous contact angles are changed along with the change of the bending angle theta of the micro-flat plate,

and

and also gradually changed, and the change curve is shown in figure 14. As is known in the art, when the instantaneous contact angle of a water droplet is smaller than the receding angle inherent to the surface, the edge of the water droplet starts to move or shrink. In this example, the back-off angle of the left side of the microplate was found to be 86 ° by experiment.

The release process of the water droplets can be divided into four stages. In the first stage, as shown in FIGS. 13(a-c), the magnet is rotated and the angle θ of the microplate is gradually decreased

And

gradually decreases but still exceeds the receding angle, i.e. 86 deg., the edge of the water drop in contact with the two microplates, i.e. the three-phase contact line (TPCL), is still pinned in place and does not move. The second phase is shown in fig. 13(d-f), with theta continuing to decrease,

the leading decrease to 86 deg. so the TPCL in contact with the left microplate starts moving first, the TPCL in contact with the right microplate remains stationary, and the second phase ends when the left TPCL moves to the top of the microplate. The third stage is shown in fig. 13(g-i), as theta continues to decrease,

also decreases to 86 deg., at which time the TPCL in contact with the right microplate begins to move until it reaches the top of the microplate, while the left TPCL remains pinned to the left microplate. At this point the fourth stage begins as in fig. 13(j-l), and the drop hangs from the right microplate and on the left microplate, dropping under gravity due to the lower adhesion of the top of the individual microplates. As can be seen from fig. 13(l), the water droplets are completely released, and the lossless transport is achieved. Instantaneous contact angle throughout the release of the drop

And

the variation with the bending angle θ is shown in fig. 14.

Example two

The present embodiment provides a surface 100 for transferring a droplet without damage, which is different from the first embodiment in that the size of each micro plate 2 is 5mm × 0.12mm × 0.5mm, and the distance between two adjacent micro plates 2 is 0.5mm, and when a droplet is grabbed, since the distance between two adjacent micro plates is reduced, the contact area between the droplet and the surface can be increased, so that a droplet with a larger volume can be grabbed. Fig. 15 shows the process of grabbing and releasing a 20 μ L drop on the surface of this example, and fig. 15(a) shows that the drop can be initially contacted with 6 microplates, increasing the volume of the grabbed drop compared to the two plates in fig. 13 (a).

As can be seen from fig. 13 and fig. 15, during the releasing process, the water drop is firstly pinned on the top of the leftmost microplate and gradually separated from the right microplate, and until the water drop completely falls off, the water drop falls off from the surface of the leftmost microplate, which is caused by the rectangular strip-shaped protruding structure on the right side of the microplate. Because the right side of the micro-flat plate is designed with the rectangular strip-shaped protruding structure, one end of the top surface of the micro-flat plate is in a continuous concave-convex shape, as shown in figure 5, the length of TPCL is increased, and the surface adhesion is improved. As can be seen from fig. 13(i), the water droplets completely contact the entire top of the left microplate and do not completely contact the top of the right microplate, so the presence of the continuous concavo-convex shape of the top surface of the microplate increases the length of the left TPCL, further increasing the adhesion force, and at this time, the TPCL length of the left microplate is greater than the TPCL length of the right microplate, so the water droplets first detach from the top of the right microplate.

In the present invention, as shown in fig. 16, if a rectangular groove is designed only on the left side of the microplate and a rectangular strip-shaped protrusion is not designed on the right side of the microplate when the droplet transfer surface 100 is prepared, when the bending angle θ of the microplate is gradually reduced, a phenomenon that the droplet is left and right alternately separated from the microplate occurs, as shown in fig. 16(h), a liquid bridge (a portion in the circle of the black dotted line) is formed between the liquid adhered on the surface and the suspended liquid, and since the liquid adhered on the surface has not yet started to move, the liquid bridge is already broken by the suspended liquid, so that the nondestructive release cannot be completed, as shown in fig. 16(i), some liquid remains on the surface after the droplet is separated from the surface. Therefore, the design of the rectangular strip-shaped protruding structure on the right side of the micro-flat plate is essential for the nondestructive release of the liquid drop.

As shown in fig. 6, one or more methods for fabricating a non-destructive transfer droplet surface 100 includes the following steps:

s1: manufacturing a template 6 with the same appearance as the surface 100 of the lossless transfer liquid drop, and sequentially carrying out ultrasonic cleaning and silanization treatment;

s2: pouring the curable elastic material on the template 6, stripping the curable elastic material from the template 6 after curing to obtain an intermediate template 7 with the surface appearance opposite to that of the template 6, and forming grooves corresponding to the micro-slabs 2 on the intermediate template 7;

s3: silanization treatment is carried out on the middle template 7, and each micro-slab 2 is poured and formed by adopting curable elastic materials added with magnetic particles 5 in the grooves corresponding to each micro-slab 2 on the middle template 7, so as to obtain the surface of the composite structure;

s4: and (2) casting a substrate 1 on the surface of the composite structure by adopting a curable elastic material without containing the magnetic particles 5, placing the substrate 1 in a magnetic field, arranging the magnetic particles 5 in a chain shape along magnetic induction lines under the action of the magnetic field, and stripping the substrate 1 without containing the magnetic particles 5 and each micro-flat plate 2 containing the magnetic particles 5 on the surface of the substrate 1 from the middle template 7 after curing to obtain the lossless transfer liquid drop surface 100.

The template 6 is prepared according to the surface appearance of the surface 100 of the lossless transfer liquid drop, the intermediate template 7 with the surface appearance opposite to that of the template 6 is prepared through the template 6, and the lossless transfer liquid drop surface 100 is prepared according to the intermediate template 7 and by combining the magnetic field effect.

In step S1, the template 6 is printed by a 3D printing technique and cleaned in an ultrasonic cleaner for 5 minutes to remove impurities on the surface of the template 6. Then the surface of the template 6 is treated by 1H, 1H, 2H, 2H perfluorododecyl trichlorosilane (abbreviated as fluorosilane) for 10 hours in a vacuum environment (the process is called silanization treatment), and the subsequent demoulding is easy to realize.

In step S2, polydimethylsiloxane (abbreviated as PDMS) is selected as the curable elastic material, and when in use, the PDMS and the curing agent are mixed in a mass ratio of 10: 1, uniformly stirring to obtain a PDMS solution, pouring the PDMS solution on a template 6, vacuumizing to remove air bubbles in the solution, heating the template 6 poured with the PDMS solution at 80 ℃ for 2 hours, and taking out the template, wherein the PDMS solution is solidified to form a colloidal solid. Since the silylation process is performed in step S1, the chemical groups on the surface layer of the template 6 are changed, so that the surface of the template 6 is easily separated from the PDMS solid, thereby preventing the PDMS solid and the template 6 from being adhered together and being unable to be separated from each other, and facilitating the stripping of the intermediate template 7 (i.e., the mold release process).

In step S3, selecting hydroxyl iron powder as magnetic particles, wherein the particle diameter is about 5 μm, and mixing PDMS and a curing agent according to a mass ratio of 10: 1, preparing a PDMS solution, adding 60% of hydroxyl iron powder by mass into the PDMS solution, uniformly stirring, pouring a PDMS mixed solution containing magnetic particles onto the surface of the intermediate template 7, vacuumizing, dipping the PDMS mixed solution containing magnetic particles into the structure on the surface of the intermediate template 7 (namely, into the grooves corresponding to the micro-plates 2), scraping off the redundant mixed solution on the surface of the intermediate template 7 by using a glass slide 8, forming the micro-plates 2, and obtaining the surface of a composite structure.

In step S4, two rubidium magnets are used to form a uniform magnetic field, a PDMS solution (containing no magnetic particles) is poured on the surface of the composite structure obtained in step S3, a substrate 1 is formed, after the substrate is placed in the uniform magnetic field, the magnetic particles are spontaneously arranged along magnetic induction lines due to the action of magnetic moments exerted on the magnetic field, the temperature is raised to 80 ° under the real-time action of the magnetic field, the temperature lasts for 2 hours, at this time, the PDMS mixed solution containing the magnetic particles and the PDMS solution containing no magnetic particles are both cured, and after demolding, the lossless transfer droplet surface 100 can be obtained. In step S3, the intermediate template 7 is silanized to facilitate peeling the non-damage transferred droplet surface 100 from the intermediate template 7 (i.e., mold release treatment). As shown in fig. 6, the substrate 1 of the surface 100 of the lossless transfer droplet contains no magnetic particles, and the interior of the microplate 2 contains magnetic particles 5 arranged in a chain form.

As shown in fig. 3-5, scanning electron micrographs (SEM images) of the left, right and top side of the microplate, respectively, are shown, all three surfaces covered with a number of microtablet structures, which is caused by the precision of the 3D printer. It can be seen that the non-destructive transfer drop surface 100 of the present invention comprises three levels of structure, respectively: the primary structure is a submicron-scale micro-flat plate; the secondary structure is a rectangular groove array and a rectangular strip-shaped bulge array; the three-stage structure is a micro-flaky structure, and the micro-flaky three-stage structure is beneficial to reducing the actual contact area of the liquid drop and the surface of the material, reducing the wettability and improving the contact angle.

As shown in fig. 17, a method for non-destructive transfer of droplets based on the above-described non-destructive transfer droplet surface 100, comprises the steps of:

(1) moving the non-marred transfer droplet surface 100 with the microplate 2 in the second position down into contact with the target droplet;

(2) after the lossless transfer droplet surface 100 grabs the target droplet through the micro-flat plate 2, the lossless transfer droplet surface 100 starts to move upwards, and then the lossless transfer droplet surface 100 adhered with the target droplet is moved to a position above the target position;

(3) and regulating the magnetic field to gradually swing the micro-flat plate 2 at the second position to the first position, so that the target liquid drop is released to the target position without damage.

As shown in fig. 17, the process of transferring water droplets without damage using the liquid droplet transfer surface 100 of the present invention is described. As shown in fig. 17(a-c), a water drop is first placed on a surface, and the fully curved microplate surface is moved downward until the surface contacts the water drop; as shown in fig. 17(d-e), the catching water droplets are adhered and then start moving upward; as shown in fig. 17(f-k), the surface on which the water droplets are caught is moved to a desired position; as shown in fig. 17(l-p), finally, the magnetic field is rotated to gradually turn the completely bent microplate into a vertical state, releasing the water droplets.

The principle and the implementation mode of the invention are explained by applying a specific example, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the foregoing, the description is not to be taken in a limiting sense.

Claims

1. A non-destructive transfer drop surface, comprising: the magnetic field-driven micro-slab vibration sensor comprises a substrate, wherein a plurality of micro-slabs are sequentially arranged on the surface of the substrate at intervals, a plurality of grooves are uniformly distributed on the same side surface of each micro-slab in an array mode, a plurality of protrusions are uniformly distributed on the other side surface of the substrate in an array mode, one end of each protrusion extends to the top surface of the micro-slab where the protrusion is located, each micro-slab is an elastic micro-slab, a plurality of magnetic particles are uniformly distributed in each micro-slab, each micro-slab can synchronously swing between a first position and a second position under the action of an external magnetic field, the first position is the position when the micro-slab is perpendicular to the surface of the substrate, the second position is the position when the micro-slab swings to the surface layer of the groove from the first position, the protrusions are strip-shaped protrusions, and the strip-shaped protrusions are perpendicular to the top surface of the micro-slab when the first position.

2. The non-destructive transfer drop surface of claim 1, wherein: the groove is a rectangular groove or a circular groove.

3. The non-destructive transfer drop surface of claim 1, wherein: the bulges are rectangular strip bulges.

4. The non-destructive transfer drop surface of claim 1, wherein: the micro-flat plate is made of polydimethylsiloxane.

5. The non-destructive transfer drop surface of claim 1, wherein: the size of the micro-plate is long multiplied by thickness multiplied by height =5mm multiplied by 0.12mm multiplied by 1mm, and the distance between two adjacent micro-plates is 1 mm.

6. The non-destructive transfer drop surface of claim 1, wherein: the size of the micro-plate is long multiplied by thickness multiplied by height =5mm multiplied by 0.12mm multiplied by 0.5mm, and the distance between two adjacent micro-plates is 0.5 mm.

7. A method for preparing a surface of a lossless transfer droplet according to any one of claims 1 to 6, wherein: the method comprises the following steps:

s3: silanizing the intermediate template, and pouring and forming each micro-slab by adopting a curable elastic material with magnetic particles in the grooves corresponding to each micro-slab on the intermediate template to obtain the surface of a composite structure;

8. A method for lossless transfer of droplets based on the surface of droplets as claimed in any of claims 1 to 6, wherein: the method comprises the following steps: