WO2012152021A1

WO2012152021A1 - Shape memory meta-material and preparation process thereof

Info

Publication number: WO2012152021A1
Application number: PCT/CN2011/084575
Authority: WO
Inventors: 刘若鹏; 赵治亚; 盖佐⋅法布里齐亚
Original assignee: 深圳光启高等理工研究院; 深圳光启创新技术有限公司
Priority date: 2011-05-11
Filing date: 2011-12-23
Publication date: 2012-11-15
Also published as: CN102480014B; CN102480014A

Abstract

The present invention relates to a shape memory meta-material and a preparation process thereof, which method comprises the steps of: S1, preparing a base material having an initial shape using a shape memory material; S2, adhering an artificial microstructure to the base material, so as to obtain a meta-material layer; and S3, imparting deformation to the meta-material layer, so as to obtain the shape memory meta-material, wherein the deformed shape memory meta-material will restore to the initial shape when meeting shape recovery conditions thereof. The present invention also relates to a shape memory meta-material produced by the process of the present invention. Since a shape memory material is used as the base material, the shape memory meta-material of the present invention has the functions of both shape memory and special magnetic response, expanding a new application field for the metal-materials.

Description

Description book shape memory metamaterial and preparation method thereof

This invention relates to the field of metamaterials and, more particularly, to a shape memory metamaterial and a method of making same. Background technique

Metamaterials are a new type of material that consists of a substrate made of a non-metallic material and a plurality of artificial microstructures attached to or embedded in the surface of the substrate. The substrate can be virtually divided into a plurality of square substrate units arranged in a rectangular array, and each of the substrate units is attached with an artificial microstructure to form a metamaterial unit, and the entire metamaterial is hundreds of thousands, millions. Even hundreds of millions of such metamaterial units are composed of crystals that are made up of a myriad of lattices in a certain arrangement. The artificial microstructures on each metamaterial unit are the same or not identical. The artificial microstructure is a cylindrical or flat wire composed of a certain geometric shape, and the shape of the composition is a circular shape, a "work" shape, and the like.

Due to the existence of artificial microstructures, each metamaterial unit has an equivalent dielectric constant and equivalent magnetic permeability different from the substrate itself, so all metamaterials composed of metamaterial units exhibit a specific response to electric and magnetic fields. Characteristics; At the same time, the specific structure and shape of the artificial microstructure can be changed, and the equivalent dielectric constant and equivalent permeability of the unit can be changed, thereby changing the response characteristics of the entire metamaterial.

In the prior art, the substrate of the metamaterial is usually made of polytetrafluoroethylene or ceramic material, and its dielectric constant and magnetic permeability are close to air, so the influence on the electromagnetic field is small, and the strength is good, and is applicable. In various communication fields such as antennas and radars. However, PTFE and ceramics are brittle and brittle. For the supermaterials that have been manufactured, the shape is fixed. In some cases where the shape needs to be fine-tuned or deformed, for example, it is spiral at room temperature and is higher than room temperature. In the case where the degree is required to be adjusted to a flat shape, the metamaterial of the existing base material cannot satisfy such a demand. Summary of the invention The technical problem to be solved by the present invention is to provide a method for preparing a shape memory metamaterial capable of being deformed under specific conditions in view of the above-mentioned drawbacks of the prior art.

The technical solution adopted by the present invention to solve the technical problem thereof is to provide a method for preparing a shape memory metamaterial.

A method for preparing a shape memory metamaterial of the present invention comprises the following steps:

51. Forming a substrate having an initial shape with a shape memory material;

52. attaching an artificial microstructure to the substrate to obtain a metamaterial layer;

53. Apply deformation to the metamaterial layer to obtain a shape memory metamaterial, and the deformed shape memory metamaterial will return to an original shape when it reaches its shape recovery condition.

In the method of producing a shape memory metamaterial according to the present invention, the initial shape of the substrate is a flat plate shape.

In the method for preparing a shape memory metamaterial according to the present invention, the step S3 is performed twice, the first shape is a semi-cylindrical shape or a cylindrical shape, and the second time is a semi-cylindrical or cylindrical shape. The memory metamaterial is shaped like a spiral.

In the method of producing a shape memory metamaterial according to the present invention, the shape memory material is a thermally induced shape memory material having a stationary phase and a reversible phase.

In the method for preparing a shape memory metamaterial according to the present invention, the thermally induced shape memory material is a styrene-butadiene copolymer having a stationary phase transition temperature _Tf of 120 ° C and a reversible phase transition temperature. T _r is 60 ° C.

In the method of preparing a shape memory metamaterial according to the present invention, the step S1 is performed by an injection molding process.

In the method of fabricating a shape memory metamaterial according to the present invention, the step S2 uses a photochemical etching process to print an artificial microstructure onto the substrate.

In the method of producing a shape memory metamaterial according to the present invention, the artificial microstructure is a metal wire having a geometric pattern which is melted and arranged by metal particles.

In the method for preparing a shape memory metamaterial according to the present invention, the step of imparting deformation to the metamaterial layer in the step S3 comprises the following steps:

S3U raises the metamaterial layer to a temperature higher than its reversible phase transition temperature and lower than its stationary phase Transition temperature

532. deform the super material layer by manual or mechanical;

533. Rapidly cooling and cooling the metamaterial layer to solidify the metamaterial layer and maintain the deformed shape.

The present invention also provides a shape memory metamaterial comprising a substrate made of a shape memory material and an artificial microstructure attached to the substrate, the shape of the substrate being relative to the initial shape when it is manufactured Gives deformation.

The shape memory metamaterial of the present invention and the preparation method thereof have the following beneficial effects: Since the shape memory material is used as the substrate, the shape memory metamaterial of the present invention has both the shape memory and the special electromagnetic response function. Metamaterials broaden the scope of new applications. DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

1 is a flow chart showing a method of preparing a shape memory metamaterial of the present invention;

2 is a detailed step view of step S3 in the flow shown in FIG. 1;

Figure 3 is a side view of the metamaterial layer obtained in the step S2 in the form of a flat plate;

Figure 4 is a front elevational view of the metamaterial layer of Figure 3;

Figure 5 is a side elevational view of the metamaterial layer of Figure 4 deformed into a semi-cylindrical shape;

Figure 6 is a side view showing the metamaterial layer shown in Figure 4 deformed into a cylindrical shape;

Fig. 7 is a side view showing a state in which the metamaterial layer shown in Fig. 3 or Fig. 4 is further deformed into a spiral shape. detailed description

The invention combines the electromagnetic response function unique to the metamaterial and the shape memory function of the shape memory material to design a shape memory metamaterial and provide a preparation method thereof.

As shown in Figs. 5 to 7, the shape memory metamaterial 4 of the present invention comprises a substrate 1 and an artificial microstructure 2 attached to the substrate 1. The conventional substrate 1 is usually made of a material such as polytetrafluoroethylene or ceramic. In contrast to the present invention, a shape memory material is used as the material of the substrate 1.

Shape memory material, as the name suggests, is a material with shape memory function, according to shape memory The different materials can be divided into thermal induction type, electric induction type, photo induction type, chemical induction type, magnetic induction type, etc. The latter materials are designed based on the basic principle of thermally induced shape memory materials. of. Regardless of the type, a shape memory material which is not a metal or an alloy can be used as the substrate 1 in the metamaterial of the present invention.

A thermally induced shape memory material means that the material is deformed by an external force at a specific temperature, cooled and cooled to deform the shape, and the material will automatically return to the deformation state when the temperature rises to the above specific temperature. The shape of such a material is a thermally induced shape memory material. Generally, the difference between the specific temperature and the room temperature here is relatively large, at least above 10 degrees Celsius, to meet the application of shape memory materials in specific situations.

Commonly used thermally induced shape memory materials are:

1) Polyethylene terephthalate, polynorbornene, trans-polyisoprene, styrene-butadiene copolymer, polyethylene, ethylene-vinyl acetate copolymer, polytetrafluoroethylene and poly a polyolefin-based shape memory material such as vinyl chloride;

2) 4,4,-dibenyl diisocyanate I polycaprolactone I 1,4 butanediol, 4,4,-dibenyl diisocyanate I polytetrahydrofuran I 1,4 butanediol, 4, a urethane block shape memory material such as 4,-dibenyl diisocyanate I polybutylene adipate diol/trimethylol propyl hydrazine;

3) Polyester type memory materials such as polyethylene terephthalate H, polycaprolactone and polylactic acid. The substrate 1 made of a shape memory material may have any desired shape in its working state, for example, a spiral shape, as shown in Fig. 6, and before being deformed, there is no freedom of internal stress or internal stress. The initial shape produced in the state is a flat plate shape as shown in FIG. When the temperature reaches the shape recovery temperature, i.e., the specific temperature above, the spiral substrate 1 is re-expanded into a flat shape to achieve a certain function.

For example, solar panels, when transported into space to absorb solar energy, need to be expanded into a flat shape to increase the surface area to absorb as much sunlight as possible, and in the process of transporting to space, in order to reduce the transport volume, it needs to be wound up. In the form of a spiral, such a solar panel can be realized by the shape memory metamaterial 4 of the present invention. On the one hand, the substrate 1 of the shape memory material is used to realize automatic development when reaching a certain temperature, and on the other hand, on the substrate 1. The artificial microstructure 2 and the substrate 1 absorb heat energy in response to electromagnetic waves emitted from the sun. The artificial microstructure 2 is attached to the substrate before the substrate 1 is deformed. The artificial microstructure 2 is typically a wire that forms a geometric pattern, such as a "work" shape, a snowflake shape, a "ten" shape, an open resonant ring, or even any other shape. The presence of the wire allows the electric field to generate an electric field and/or a magnetic field response when the electromagnetic wave passes through, so that the entire metamaterial exhibits a characteristic electromagnetic response characteristic, realizing a special function not possessed by the natural material, such as absorbing, converging or Divergence of electromagnetic waves, etc.

The artificial microstructure 2 is attached to the substrate 1 by etching, ion etching, electroplating, printing, etc., and each of the substrate 1 and the artificial microstructure 2 on the surface thereof constitute a metamaterial layer 3, and each shape memory metamaterial 4 One or more such metamaterial layers 3 are included.

The method for preparing the shape memory metamaterial 4 of the present invention, as shown in Fig. 1, comprises the following steps:

Sl, using a shape memory material to make a substrate 1 having an initial shape;

In this step, an optional shape memory material has been described in detail above, and the above non-metallic, non-alloy thermally induced shape memory material can be used as the substrate 1 in the present invention. In practice, a commonly used shape memory material is selected from the group consisting of styrene-butadiene copolymer, prepolymer of diphenylformamidine diisocyanate and butanediol, and polynorbornene, preferably styrene- Butadiene copolymer.

Thermally induced shape memory materials typically include a stationary phase and a reversible phase. The reversible phase is a part of the shape memory that is realized by dynamic equilibrium, and is usually an amorphous rubber state and a glass transition, and melting and recrystallization of crystals. Stationary phase at its melting point may be a small "or _a glass transition temperature T _g of less molecular wound interpenetrating networks, such as the molecular weight of polycaprolactone (PLC), and polynorbornene, such polymers form a physical crosslinking The stationary phase of the joint may also be an amorphous region having a crosslinked structure, such as the first discovered shape memory polymer crosslinked polyethylene, forming a chemically crosslinked stationary phase.

For example, the above preferred styrene - butadiene copolymer, a polystyrene stationary phase is partially crystalline, partially reversible phase butadiene, stationary phase from a solid to a liquid melting transition temperature T _f of about 120 ° C, The transition temperature of the reversible phase is 1; it is about 60 °C. In order to make the shape memory material into the substrate 1, in order to make the internal stress of the substrate 1 small, the liquid shape memory material is usually injected into the cavity of the molding machine by injection molding or casting molding, and the temperature of the liquid material should be obvious at this time. Above T _f , usually between 125 and 135 ° C, to ensure that the material can flow freely, the internal stress is small, and after injecting into the cavity, it is solidified by natural cooling or water cooling to obtain a substrate 1 having an initial shape. If the substrate 1 is thin, it can be formed into a thick plate by casting or injection molding, and then calendered to obtain a thin plate. The initial shape may be a flat plate shape, or any other shape, depending on actual needs, as long as a cavity of a different shape is designed.

After step S1 is completed and the substrate 1 having the initial shape is obtained, the following steps are performed:

S2, attaching the artificial microstructure 2 to the substrate 1 to obtain a metamaterial layer 3, as shown in FIG. 3 and FIG. 4;

Step S2 can be achieved by etching or plating. The etching process here generally refers to photochemical etching, which is similar to the fabrication of a PCB, in which a metal foil layer is first deposited on the surface of the substrate, and after exposure and plate development, the protective film to be etched is removed. When the metal is in contact with the chemical solution in the region, it is dissolved and corroded, and the remaining metal wire having a certain geometric pattern is the artificial microstructure 2.

If an etching process is employed, the chemical solvent used for etching should be prevented from reacting with the substrate 1 so as not to damage the surface smoothness of the substrate 1, or even destroy the overall structure and shape of the substrate 1.

Step S2 can also be printed onto the substrate 1 by a printing process. Similar to a conventional printer, metal powder particles of a certain size range are placed in a printer, and in the region where the artificial microstructure 2 is required, the metal particles are pushed onto the region of the substrate 1 and heated and melted, which is a metal particle. Melting into a single metal wire forms the effect of "printing" the artificial microstructure 2.

If a printing process is employed, it should be noted that the temperature at which the metal particles are heated to melt should be lower than the stationary phase transformation temperature of the shape memory material, ie, the melting point of the stationary phase, to avoid melting deformation of the material; or, the metal particles are heated and solidified. The speed should be extremely fast and the action of "printing" the artificial microstructure 2 is completed before the heat is transferred to the substrate 1.

The specific process for producing the artificial microstructure 2 by the printing process can also refer to the patent "Fabrication of electronic components in plastic" (Application No. EP20060752653, inventor David Victor Thiel and Neeli Madhusudanrao), and its embossing machine A conductive artificial microstructure 2 having a certain geometric pattern is printed on the plastic substrate 1. This invention patent illustrates the step S2 of the present invention being feasible.

The individual artificial microstructures 2 are produced in turn, and the substrate and the artificial microstructures 2 thereon form a metamaterial layer 3 together. S3, deforming the metamaterial layer 3 to obtain a shape memory metamaterial 4.

The imparting deformation, referred to as shaping, is to use an external force to drive the metamaterial layer 3 to deform into another shape different from the original shape, such as a spiral shape. The shape memory effect characteristic of thermally induced shape memory materials is derived from its special structure, and its stationary phase transition temperature T _f (T _g or T _{m of the} stationary phase) is higher than the reversible phase transition temperature TV (T _g or T of the reversible phase) _m ), and requires reversible phase 1^ or 1 ¹ „ ₁ above room temperature, the reversible phase and the stationary phase are both in a glassy or crystalline state at room temperature, and the segment motion is limited.

When the temperature is higher than _Tf , the reversible phase molecular chain has sufficient energy for the conformational change, and the segmental motion is intensified. The macroscopic representation is the melting of the crystalline phase or the transition from the glassy state to the high elastic state. At this time, the material can be deformed by external force or other factors, and the stationary phase is still in a crystalline state or a glass state at this time, and the molecules are physically fixed by each other, preventing the molecular chain from slipping, resisting deformation, reversible phase and The interaction between the stationary phases inhibits the plastic movement of the chain and produces a back shape memory effect. The shaped material is cooled, the deformation of the reversible phase is fixed, the movement of the segment is limited, and the reversible phase is returned to the glassy or crystalline state, and the material is stably present in this shape.

When the outside gives a stimulus to the shaped shape memory material, the material will produce a shape recovery process. BP, after heating up again, the molecular chain curls due to entropy elasticity, the resilience of the stationary phase is released, and the deformation is restored, that is, the initial shape in step S1 is restored.

The metamaterial layer 3 of the present invention belongs to the range of metamaterials. Since the artificial microstructure 2 of the metal adhered to the substrate 1 can respond to electromagnetic waves, heat is generated inside the material, and shape recovery occurs after reaching a certain temperature. Until the initial shape. Among the shape memory materials, a material having a low thermal conductivity is preferable, so that heat is not easily diffused, a heat generation temperature is high, and a shape recovery is fast.

Therefore, step S3 is performed in order to apply the metamaterial to the actual environment, and once the environmental condition reaches its shape recovery condition, it will return to the original shape. For a thermally induced shape memory material, the shape recovery condition is the shape recovery temperature.

The shape recovery temperature is also the temperature at which the metamaterial layer 3 is shaped, the value of which is not lower than the reversible phase transition temperature and not higher than the stationary phase transition temperature _Tf , and the reversible phase at this time is in the glass state. Therefore, as shown in FIG. 2, step S3 can be performed as follows:

531. The super material layer 3 obtained in step S2 is heated to a shape recovery temperature;

532. deform the metamaterial layer 3 by manual or mechanical means; S33. The metamaterial layer 3 is rapidly cooled and cooled to solidify the metamaterial layer 3 and maintain the deformed shape.

As shown in Fig. 5 and Fig. 6, in step S32, the flat-shaped metamaterial layer 3 can be deformed into a semi-cylindrical shape or a cylindrical shape by means of punching.

If the metamorphic deformation of the metamaterial layer 3 does not reach the desired shape such as the spiral shape of the solar panel, it can be achieved by multiple deformations. For example, the steps S31, S32, and S33 are performed to first deform the metamaterial layer 3 into a cylindrical shape or a semi-cylindrical shape, and then perform the steps S31, S32, and S33 to manually change the cylindrical or semi-cylindrical metamaterial 4. Form a spiral, as shown in Figure 7.

It should be noted that the shape memory material of the present invention is not limited to the above-mentioned thermally induced type materials, and other shape memory materials such as magnetic induction type and photoinduced type shape memory materials may be utilized, and the steps and steps thereof are used. After the super material layer 3 is obtained by the same method of Sl and S2, when the step S3 is performed, the shaped environmental condition or the shape recovery condition is no longer the temperature but the magnetic field and the illumination. For example, when the shape memory material is a photoinduced material, step S3 should be performed as follows:

531. Illuminating the metamaterial layer 3 obtained in step S2;

532. deform the metamaterial layer 3 by manual or mechanical;

533. Stop the illumination of the metamaterial layer 3, and solidify the metamaterial layer 3 and maintain the deformed shape.

The metamaterial thus obtained also belongs to the shape memory metamaterial 4 of the present invention.

With the shape memory metamaterial 4 of the present invention, the design of the artificial microstructure 2 can realize a special response to electromagnetic waves, for example, can be used as a lens, a beam compressor, a beam shifter, an antenna. In the microwave field such as absorbing materials, the shape memory material of the present invention as the substrate 1 further expands the application range and application environment of the metamaterial, such as the solar panel described above. Another example is that the metamaterial can be used as a switch for preventing electromagnetic radiation, and the substrate 1 of the metamaterial is a magnetic induction type shape memory material, and the substrate 1 is bent without electromagnetic radiation or low radiation intensity. Contacting the switch contact to open the switch; when receiving a strong electromagnetic wave, the magnetic field excitation causes the shape memory material to heat up and deform, and after the deformation is in contact with the switch contact, the switch is turned on, then one can judge that there is a strong Electromagnetic wave radiation.

There are many other application examples of the present invention, which are not enumerated herein. Any step that conforms to the invention The method and the shape memory metamaterial prepared by the method of the present invention are all within the scope of the present invention.

Claims

Claim

A method for preparing a shape memory metamaterial, comprising the steps of:

51. Forming a substrate having an initial shape with a shape memory material;

The method of producing a shape memory metamaterial according to claim 1, wherein the initial shape of the substrate is a flat plate shape.

The method for preparing a shape memory metamaterial according to claim 2, wherein the step S3 is performed twice, the first shape is a semi-cylindrical shape or a cylindrical shape, and the second half is a semi-cylinder The shape or cylindrical shape memory metamaterial is shaped as a spiral.

4. The method of preparing a shape memory metamaterial according to claim 1, wherein the shape memory material is a thermally induced shape memory material having a stationary phase and a reversible phase.

The method of preparing a shape memory metamaterial according to claim 4, wherein the thermally induced shape memory material is a styrene-butadiene copolymer having a stationary phase transition temperature _Tf of 120 ° C, reversible phase transition temperature T _r of 60 ° C.

The method of preparing a shape memory metamaterial according to claim 4, wherein the step S1 employs an injection molding process.

7. The method of preparing a shape memory metamaterial according to claim 4, wherein the step S2 uses a photochemical etching process to print an artificial microstructure onto the substrate.

The method of preparing a shape memory metamaterial according to claim 7, wherein the artificial microstructure is a metal wire having a geometric pattern which is melted and arranged by metal particles.

9. The method of preparing a shape memory metamaterial according to claim 4, wherein the imparting deformation to the metamaterial layer in the step S3 comprises the following steps:

531. The metamaterial layer is heated to a temperature higher than a reversible phase transition temperature and lower than a stationary phase transition temperature thereof, wherein the reversible phase in the shape memory material is in a glass state;

532. deform the super material layer by manual or mechanical;

533. Rapidly cooling and cooling the metamaterial layer to solidify and maintain the deformation of the metamaterial layer. shape.

10. A shape memory metamaterial comprising: a substrate made of a shape memory material and an artificial microstructure attached to the substrate, the shape of the substrate being relative to an initial state when it is manufactured The shape is given a deformation.