CN115431513B - Preparation method of flexible tactile feedback array based on liquid crystal elastomer actuation - Google Patents
Preparation method of flexible tactile feedback array based on liquid crystal elastomer actuation Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/10—Processes of additive manufacturing
- B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
- B29C64/307—Handling of material to be used in additive manufacturing
- B29C64/314—Preparation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/10—Pre-treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/20—Post-treatment, e.g. curing, coating or polishing
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/06—Non-steroidal liquid crystal compounds
- C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
- C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
- C09K19/20—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and oxygen atoms as chain links, e.g. esters or ethers
- C09K19/2007—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and oxygen atoms as chain links, e.g. esters or ethers the chain containing -COO- or -OCO- groups
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/06—Non-steroidal liquid crystal compounds
- C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
- C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
- C09K19/20—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and oxygen atoms as chain links, e.g. esters or ethers
- C09K19/2007—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and oxygen atoms as chain links, e.g. esters or ethers the chain containing -COO- or -OCO- groups
- C09K19/2021—Compounds containing at least one asymmetric carbon atom
- C09K19/2028—Compounds containing at least one asymmetric carbon atom containing additionally a linking group other than -COO- or -OCO-, e.g. -CH2-CH2-, -CH=CH-, -C=C-; containing at least one additional carbon atom in the chain containing -COO- or -OCO- groups, e.g. -COO-CH*-CH3
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/38—Polymers
- C09K19/3833—Polymers with mesogenic groups in the side chain
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/38—Polymers
- C09K19/3833—Polymers with mesogenic groups in the side chain
- C09K19/3842—Polyvinyl derivatives
- C09K19/3852—Poly(meth)acrylate derivatives
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/06—Non-steroidal liquid crystal compounds
- C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
- C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
- C09K19/20—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and oxygen atoms as chain links, e.g. esters or ethers
- C09K19/2007—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing carbon and oxygen atoms as chain links, e.g. esters or ethers the chain containing -COO- or -OCO- groups
- C09K2019/2078—Ph-COO-Ph-COO-Ph
Abstract
The invention discloses a preparation method of a flexible tactile feedback array based on liquid crystal elastomer actuation, which comprises the following steps: step S1: preparing multi-element liquid crystal olefin molecules; step S2: preparing a 3D printing ink precursor; and step S3: preparing 3D printing ink; and step S4: preparing a flexible haptic feedback actuation material; step S5: preparing a dry liquid crystal elastomer film with an orientation structure and a thickness of 300 mu m; step S6: preparing a flexible circuit; step S7: a flexible tactile feedback array is prepared. The invention relates to a portable flexible tactile feedback array which is formed by regulating and controlling the composition and molecular weight of a reactive liquid crystal polymer mixture to enable the mixture to have an extrusion 3D printing characteristic, realizing the shear orientation of a liquid crystal polymer through the shearing of the mixture, namely a printing ink melt in a limited area on the basis, taking a prepared liquid crystal elastomer film capable of changing from two dimensions to three dimensions as a base material, and further combining a flexible substrate, a heating electrode and an energy supply system.
Description
Technical Field
The invention relates to the technical field of preparation of flexible actuating materials, in particular to a preparation method of a flexible tactile feedback array based on liquid crystal elastomer actuation.
Background
The liquid crystal molecules are organic molecules with a certain length-diameter ratio, can realize the transformation from an ordered condensed state structure to a disordered microstructure under the induction of certain external stimulation or internal factors, and cause the change of microscopic and macroscopic characteristics of liquid crystal molecular aggregates. By utilizing the characteristics, the oriented state single domain liquid crystal material can be used as an intelligent material in the aspects of soft robots, artificial muscles, actuators and the like, and stimulation sources of the oriented state single domain liquid crystal material comprise light, electricity, magnetism, heat and the like. In order to achieve the mobility of the liquid crystal material, the liquid crystal cell needs to be processed anisotropically, and the liquid crystal cell is usually aligned by shearing, stretching, compressing, and the like. The 3D printing technology enables the printing ink melt to be compressed and sheared in the limited space of the nozzle so as to be oriented, and then the complicated orientation of the liquid crystal in the plane can be realized through the control of the printing path so as to endow the liquid crystal with a special reversible stimulation deformation mode.
Virtual reality and augmented reality technologies are often used to simulate visual and auditory senses to give a user a near-realistic experience. The tactile feedback is an important means for further enhancing technologies such as virtual reality and augmented reality, and can bring the virtual environment to a feeling which is nearly indistinguishable from reality. The reversible and controllable two-dimensional to three-dimensional deformation characteristic of the liquid crystal elastomer is utilized, the liquid crystal elastomer can be prepared into an array which can be reversibly stretched up and down in space, the liquid crystal elastomer can be controllably raised and restored in a programmed manner through reasonable structural design, and human tactile receptors are stimulated, so that the tactile feedback is realized. In addition, since the entire device is composed of a polymer, it may have excellent flexibility and portability.
To this end, we propose a method for the preparation of a flexible tactile feedback array based on liquid crystal elastomer actuation.
Disclosure of Invention
The invention aims to provide a preparation method of a flexible tactile feedback array based on liquid crystal elastomer actuation, which solves the problems that how to have potential application in the aspects of virtual reality, augmented reality, braille and the like in the prior art can make the performance of the obtained brake material be controllably adjusted according to requirements, and the sensitivity of touch and the working stability of the tactile array are realized.
The technical scheme adopted by the invention is as follows:
a preparation method of a flexible tactile feedback array based on liquid crystal elastomer actuation comprises the following steps:
step S1: stirring and dissolving 4 equivalents of 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene in a tetrahydrofuran solvent, and adding 0.04 equivalent of a catalyst for uniform mixing to obtain a mixed solution; dissolving 1 equivalent of pentaerythritol tetrakis (3-mercaptopropionate) in tetrahydrofuran, dropwise adding the tetrahydrofuran into the mixed solution at constant pressure, continuously reacting completely at room temperature after the addition is finished, and finally, performing column chromatography to obtain a multi-element liquid crystal olefin molecule;
step S2: 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy]Dissolving 2-methylbenzene and 2,2' - (1, 2-ethanediylbis oxo) bisethanethiol in dichloromethane according to a molar ratio of 1.05-1.2 3 -3.0×10 2 Pa.s of 3D printing ink precursor;
and step S3: cleaning the 3D printing ink precursor with deionized water, filtering and drying to obtain a white solid, dissolving the white solid in dichloromethane, adding 1-10% of multi-element liquid crystal olefin molecules by mass fraction, uniformly mixing, performing reduced pressure volatilization at a preset temperature, and drying to obtain 3D printing ink;
and step S4: adding the 3D printing ink into a 3D printing material cylinder for heating, printing the heated 3D printing ink on a glass substrate coated with thin polyvinyl alcohol in a spinning mode, and meanwhile, adopting the intensity of 20-40mW/cm 2 The printing path is controlled to control the orientation structure of the liquid crystal unit in a two-dimensional plane, and the flexible tactile feedback actuating material is obtained;
step S5: continuing to react the flexible tactile feedback actuating material under the same ultraviolet light in the step S4, finally putting the flexible tactile feedback structure into water to dissolve polyvinyl alcohol, and drying to obtain a liquid crystal elastomer film with an orientation structure and a thickness of 300 mu m;
step S6: printing array-type annular copper heating electrodes on a flexible substrate and connecting the electrodes out by using copper leads, respectively mounting the liquid crystal elastomer films on the array-type annular heating electrodes, and bonding the edges by using an adhesive to obtain a flexible circuit;
step S7: and bonding a polymer protective layer on the flexible circuit, wherein the polymer protective layer enables the Z-direction actuation of the region where the annular copper heating electrode and the liquid crystal elastomer film are located to be not limited by the protective layer in a hole opening mode, so that the flexible tactile feedback array is obtained.
Further, the poly-liquid crystal olefin molecule in the step S1 is tetra (((4- (6-acryloyloxyhexyloxy) benzoyloxy) -2-methyl benzene) -4 ((4- (ethylpropyloyloxyhexyloxy) benzoyloxy) -2-methyl benzene) thioether) pentaerythritol ester, and is used for adjusting rheological characteristics of printing ink and a rate of thermoreversible deformation of the liquid crystal elastomer film.
Further, the catalyst in step S1 is di-n-propylamine or triethylamine, and the photoinitiator in step S2 is benzoin dimethyl ether or a photoinitiator 819.
Further, the molar ratio of the 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene and the 2,2' - (1, 2-ethanediylbisixoy) bisethanethiol in the step S2 was 1.1, and the complete reaction was carried out in a stoichiometric ratio, and the number average polymerization degree of the resulting polymer was 10.
Further, the mass fraction of the molecules of the multi-component liquid crystal olefin in the step S3 is 5%.
Further, the preset temperature in the step S3 is 60 ℃, the temperature for heating the 3D printing ink added into the 3D printing cartridge in the step S4 is 70 ℃, and the heating time is 1h.
Further, in the step S4, the pressure of printing the heated 3D printing ink on the glass substrate spin-coated with the thin layer of polyvinyl alcohol is 80psi, and the speed is 1-10mm/S.
Further, the wavelength of the ultraviolet light in the step S4 is 365nm.
Further, the time for continuing the reaction of the flexible tactile feedback structure under the ultraviolet light in the step S5 is 120min.
Further, the material of the flexible substrate in the step S6 or the polymer protective layer in the step S7 is one of polyethylene terephthalate, polyimide, polydimethylsiloxane, polyurethane, polycarbonate, and mono-or biaxially oriented polypropylene.
The invention has the beneficial effects that:
1. the invention relates to a portable flexible tactile feedback array which is formed by regulating and controlling the composition and molecular weight of a reactive liquid crystal polymer mixture to enable the mixture to have an extrusion 3D printing characteristic, realizing the shearing orientation of a liquid crystal polymer through shearing the mixture, namely a printing ink melt in a limited area on the basis, taking a prepared liquid crystal elastomer film capable of changing from two dimensions to three dimensions as a base material, and further combining a flexible substrate, a heating electrode and an energy supply system.
2. The invention has the advantages of clear and simple principle and simple and controllable preparation method. According to the actual application requirements, the dynamic controllability of the braking performance and the mechanical performance of the material can be realized through the control of ink composition and the adjustment of printing parameters, so that the material has potential application in the aspects of virtual reality, augmented reality, braille touch and the like.
Drawings
FIG. 1 is a schematic diagram of a flexible haptic feedback array in accordance with embodiment 1 of the present invention;
fig. 2 shows the thermal excitation cyclic deformation stability of the 3D printing liquid crystal elastomer film at 90 ℃ and normal temperature in embodiment 4 of the present invention;
FIG. 3 is a deformation-time diagram of a 3D printed liquid crystal elastic film in the heating process at 90 ℃ and the natural cooling process in embodiment 4 of the invention;
FIG. 4 is a temperature-deformation diagram of a 3D printed liquid crystal elastomer film in a temperature range of 50-100 ℃ in example 4 of the present invention;
FIG. 5 is a stress-strain curve of a 3D printed liquid crystal elastomer film in comparative example 1 of the present invention;
FIG. 6 is a stress-strain test graph of a 3D printed liquid crystal elastomer film in example 4 of the present invention;
fig. 7 is a diagram illustrating a height variation rule of a printed liquid crystal elastomer tactile unit in a periodic electric field according to embodiment 4 of the present invention.
Detailed Description
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. 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.
Example 1: a preparation method of a flexible tactile feedback array based on liquid crystal elastomer actuation comprises the following steps:
step S1: dissolving 4 equivalents of 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene in a tetrahydrofuran solvent by stirring, and adding 0.04 equivalent of catalyst di-n-propylamine for uniform mixing to obtain a light yellow solution; dissolving 1 equivalent of pentaerythritol tetrakis (3-mercaptopropionate) in tetrahydrofuran, dropwise adding at constant pressure into the mixed solution, continuing to react at room temperature for 2 hours after the addition is finished, and finally, performing column chromatography to obtain a multi-element liquid crystal olefin molecule, namely pentaerythritol tetrakis (((4- (6-acryloyloxyhexyloxy) benzoyloxy) -2-methylbenzene) -4 ((4- (ethylpropyloyloxyhexyloxy) benzoyloxy) -2-methylbenzene) thioether);
step S2: 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy]Dissolving-2-methylbenzene and 2,2' - (1, 2-ethanediylbis oxo) bis (ethanethiol) in dichloromethane according to a molar ratio of 1.05 3 Pa.s of a 3D printing ink precursor;
and step S3: washing, filtering and drying the 3D printing ink precursor by using deionized water to obtain a white solid, dissolving the white solid in dichloromethane, adding 8% of multi-element liquid crystal olefin molecules by mass percent, uniformly mixing, volatilizing at the temperature of 60 ℃ under normal pressure, and drying to obtain 3D printing ink;
and step S4: adding the 3D printing ink into a 3D printing material cylinder, heating for 1h at 70 ℃, extruding the ink at 80Psi, and printing on a glass substrate coated with thin polyvinyl alcohol in a spinning mode, wherein the printing speed is 1mm/s, and the strength is 20mW/cm 2 The wavelength of the liquid crystal is 365nm, a printing path is controlled to control the orientation structure of the liquid crystal unit in a two-dimensional plane, and the liquid crystal material with the thermoreversible Z-axis deformation is obtained and used as a basic material of the tactile feedback array;
step S5: continuously reacting the flexible tactile feedback structure for 120min under the ultraviolet light with the wavelength of 365nm, finally putting the flexible tactile feedback structure into water to dissolve polyvinyl alcohol, and drying to obtain a liquid crystal elastomer film with an orientation structure and the thickness of 300 mu m;
step S6: printing array-type annular copper heating electrodes on a polyethylene glycol terephthalate substrate, connecting the array-type annular copper heating electrodes out by using copper leads, respectively installing the liquid crystal elastomer films on the array-type annular heating electrodes, and bonding the edges by using an adhesive to obtain a flexible circuit;
step S7: and adhering a polyethylene glycol terephthalate protective layer on the flexible circuit, wherein the polyethylene glycol terephthalate protective layer enables the Z-direction actuation of the region where the annular copper heating electrode and the liquid crystal elastomer film are located to be not limited by the protective layer in a hole opening mode, so that a flexible tactile feedback array is obtained, and the composition structure of the flexible tactile feedback array is shown in figure 1.
Example 2: the procedure is the same as in example 1, except that:
the catalyst used in the step S1 and the step S2 is triethylamine;
1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy group in step S2]The mol ratio of the (E) -2-methylbenzene to the (2, 2' - (1, 2-ethanediylbis oxo) bisethanethiol is 1.1, and the photoinitiator 819 is used as a photoinitiator, so that the catalyst is preparedThe viscosity of the obtained 3D printing ink precursor is 3 multiplied by 10 3 Pa•s；
In the step S3, the mass fraction of the multi-element liquid crystal olefin molecules is 6%;
the printing speed in the step S4 is 4mm/S, and the ultraviolet light intensity is 30mW/cm 2 ；
The materials of the flexible substrate and the polymer protective layer in the steps S6 and S7 are polyurethane.
Example 3: the procedure was the same as in example 1, except that:
the catalyst used in the step S1 and the step S2 is triethylamine;
in the step S2, the photoinitiator is the photoinitiator 819, and the viscosity of the obtained 3D printing ink precursor is 5 x 10 3 Pa•s；
In the step S3, the mass fraction of the multi-component liquid crystal olefin molecules is 3%;
the printing speed in the step S4 is 8mm/S, and the ultraviolet light intensity is 35mW/cm 2 ；
The materials of the flexible substrate and the polymer protective layer in the steps S6 and S7 are polydimethylsiloxane.
Example 4: the procedure was the same as in example 1, except that:
1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy group in step S2]A molar ratio of-2-methylbenzene to 2,2' - (1, 2-ethanediylbisixoxy) bisethanethiol of 1.1, and a viscosity of the resulting 3D printing ink precursor of 3 × 10 3 Pa•s；
In the step S3, the mass fraction of the multi-component liquid crystal olefin molecules is 5%;
the printing speed in the step S4 is 5mm/S, and the ultraviolet light intensity is 40mW/cm 2 ；
The materials of the flexible substrate and the polymer protective layer in the steps S6 and S7 are polyimide.
The reversible thermomechanical cycle behavior of the splines obtained in the same way is shown in fig. 2; the time-varying behavior of the deformation is shown in fig. 3; the deformation quantity is plotted with the temperature, see fig. 4; the change rule of the two-dimensional to three-dimensional structure of the liquid crystal elastomer tactile unit under the periodic electric field is shown in figure 6, and the printed graph of the change rule of the height of the two-dimensional to three-dimensional change of the liquid crystal elastomer tactile unit under the periodic electric field is shown in figure 7.
Example 5: the procedure was the same as in example 1, except that:
1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy group in step S2]The molar ratio of-2-methylbenzene to 2,2' - (1, 2-ethanediylbis-oxo) bisethanethiol is 1.2, the photoinitiator is the photoinitiator 819, and the viscosity of the obtained 3D printing ink precursor is 2 × 10 2 Pa•s；
In the step S3, the mass fraction of the multi-element liquid crystal olefin molecules is 1%;
the printing speed in step S4 is 10mm/S, and the ultraviolet light intensity is 40mW/cm 2 ；
The materials of the flexible substrate and the polymer protective layer in the steps S6 and S7 are both polycarbonate.
Example 6: the procedure was the same as in example 1, except that:
in the step S3, the mass fraction of the multi-component liquid crystal olefin molecules is 10%;
the printing speed in the step S4 is 5mm/S, and the ultraviolet light intensity is 40mW/cm 2 ；
In step S6 and step S7, the flexible substrate and the polymer protective layer are both made of uniaxially stretched polypropylene.
Example 7: the procedure is the same as in example 1, except that:
the catalyst used in the step S1 and the step S2 is triethylamine;
1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy group in step S2]The molar ratio of the-2-methylbenzene to the 2,2' - (1, 2-ethanediylbis-oxo) bisethanethiol is 1.1, the photoinitiator is the photoinitiator 819, and the viscosity of the obtained 3D printing ink precursor is 3 × 10 3 Pa•s；
In the step S3, the mass fraction of the multi-element liquid crystal olefin molecules is 5%;
the printing speed in the step S4 is 5mm/S, and the ultraviolet light intensity is 40mW/cm 2 ；
The materials of the flexible substrate and the polymer protective layer in the steps S6 and S7 are both biaxially oriented polypropylene.
Comparative example 1: the procedure is the same as in example 4, except that: the molar ratio of 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene and 2,2' - (1, 2-ethanediylbisiroxo) bisethanethiol in step S2 was 0.8.
The mechanical properties are shown in fig. 5 (since the end group is thiol, the photo-initiated crosslinking reaction cannot be performed, and the number average degree of polymerization is only 5, the mechanical properties are very poor, and there is no reversible braking effect).
Comparative example 2: the procedure was the same as in example 4, except that: the molar ratio of 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene to 2,2' - (1, 2-ethanediylbisiloxy) bisethanethiol in step S2 was 1.5.
Comparative example 3: the procedure is the same as in example 4, except that: the mass fraction of the multi-component liquid crystal olefin molecules in the step S3 is 15%.
Comparative example 4: the procedure is the same as in example 4, except that: in step S3, no multi-component liquid crystal olefin molecules are added.
Comparative example 5: the procedure is the same as in example 4, except that: the ultraviolet light intensity in the step S4 is 10mW/cm 2 。
Comparative example 6: the procedure was the same as in example 4, except that: the ultraviolet light intensity in the step S4 is 60mW/cm 2 。
Comparative example 7: the procedure was the same as in example 4, except that: the printing speed in step S4 was 10mm/S.
The examples and the comparative examples are subjected to performance tests, and the test results are shown in table 1:
table 1 comparative table of performance test of examples and comparative examples
Description of the drawings: "-" indicates that the data is not available.
It can be seen that, according to comparative example 1 and comparative example 2, when the ratio of the molar ratio of 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene to 2,2' - (1, 2-ethanediylbis-oxo) bisethanethiol is lower than the optimum value in example 4 and is greater than 1, the molecular weight of the obtained ink precursor polymer is too large to perform alignment and printing of the liquid crystal material by hot-melt extrusion or to leave a mercapto group at the polymer terminal to perform subsequent photocrosslinking, resulting in a material having no reversible actuation characteristics; when the value is less than the optimum value in example 4 and less than 1, the end of the polymer constituting the printing ink is a mercapto group, and a subsequent crosslinking reaction cannot be performed, so that the polymer cannot be used as a thermoreversible actuating material; when the molecular weight of the obtained ink precursor polymer is higher than the optimal value in example 4, the molecular weight of the obtained ink precursor polymer is small, the melt viscosity of the obtained ink precursor polymer is too low, the printing process is uncontrollable, the orientation of liquid crystals caused by shearing is difficult to fix, the appearance form and reversible deformation rate of the material are reduced, and finally the performance of a final touch array is seriously weakened, and even the array cannot be successfully prepared.
According to comparative examples 3 and 4, the material crosslinking degree is too high due to too much crosslinking degree of the multi-component liquid crystal, so that the order-disorder transition of the liquid crystal unit is limited in the thermal braking process of the liquid crystal elastomer, and the reversible expansion and contraction amplitude of the array in the Z-axis direction is further reduced. When the value is less than the optimum value in example 4, the degree of crosslinking of the material is low and does not provide good mechanical properties, thereby affecting the self-support and the mechanical stability of the material in use.
According to comparative examples 5 and 6, when the intensity of ultraviolet light is lower than the optimum value in example 4, the material cannot fix the liquid crystal orientation induced by extrusion shearing during the primary crosslinking process, and finally the degree of orientation of the liquid crystal cell in the material is reduced and a large degree of reversible deformation cannot be provided; when the amount is larger than the optimum value in example 4, the degree of completion of primary crosslinking is large, and the fluidity of the melt is limited, so that fusion between the extruded strands cannot occur and a specifically oriented elastomeric film cannot be obtained or the quality of the film is not good, which is not the most preferable for the production of the tactile feedback array in the present invention.
According to comparative example 7, it was found that when the printing speed was higher than the optimum value in example 4, the appearance integrity of the printed liquid crystal elastomer was difficult to control and could not be used as a material for producing a tactile feedback array in the present invention. In addition, when the printing speed is lower than the optimum value in example 4, the shearing force of the printing ink in the head is relatively small, thereby reducing the degree of orientation of the liquid crystal cell and finally weakening the reversible deformation amount of the material.
In conclusion, the reversible actuation characteristic and the physical and mechanical characteristic of the liquid crystal elastomer are balanced by controlling the composition proportion of the ink and the extrusion printing condition, so that the liquid crystal elastomer can realize larger reversible thermotropic mobility and simultaneously ensure good mechanical property, and finally, the preparation of a high-performance tactile feedback array is realized.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of a flexible tactile feedback array based on liquid crystal elastomer actuation is characterized by comprising the following steps:
step S1: stirring and dissolving 4 equivalents of 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene in a tetrahydrofuran solvent, and adding 0.04 equivalent of catalyst for uniform mixing to obtain a mixed solution; dissolving 1 equivalent of pentaerythritol tetrakis (3-mercaptopropionate) in tetrahydrofuran, dropwise adding the tetrahydrofuran into the mixed solution at constant pressure, continuously reacting completely at room temperature after the addition is finished, and finally, performing column chromatography to obtain a multi-element liquid crystal olefin molecule;
step S2: 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy]Dissolving 2-methylbenzene and 2,2' - (1, 2-ethanediylbis oxo) bisethanethiol in dichloromethane according to a molar ratio of 1.05-1.2 3 -3.0×10 2 Pa.s of a 3D printing ink precursor;
and step S3: washing, filtering and drying the 3D printing ink precursor by using deionized water to obtain a white solid, dissolving the white solid in dichloromethane, adding 1-10% by mass of the multi-element liquid crystal olefin molecules prepared in the step S1, uniformly mixing, volatilizing at normal pressure at a preset temperature, and drying to obtain 3D printing ink;
and step S4: adding the 3D printing ink into a 3D printing material cylinder for heating, printing the heated 3D printing ink on a glass substrate which is coated with thin polyvinyl alcohol in a spinning way, and simultaneously adopting the intensity of 20-40mW/cm 2 The printing path is controlled to control the orientation structure of the liquid crystal unit in a two-dimensional plane, and a flexible touch feedback structure is obtained;
step S5: continuing to react the flexible tactile feedback structure under the same ultraviolet light in the step S4, finally putting the flexible tactile feedback structure into water to dissolve polyvinyl alcohol, and drying to obtain a liquid crystal elastomer film with an orientation structure and a thickness of 300 mu m;
step S6: printing array-type annular copper heating electrodes on a flexible substrate and connecting the electrodes out by using copper leads, respectively mounting the liquid crystal elastomer films on the array-type annular heating electrodes, and bonding the edges by using an adhesive to obtain a flexible circuit;
step S7: and bonding a polymer protective layer on the flexible circuit, wherein the polymer protective layer enables the Z-direction actuation of the region where the annular copper heating electrode and the liquid crystal elastomer film are located to be not limited by the protective layer in a hole opening mode, so that the flexible tactile feedback array is obtained.
2. The method of claim 1, wherein the poly-liquid crystal olefin molecule in step S1 is tetra (((4- (6-acryloyloxyhexyloxy) benzoyloxy) -2-methylbenzene) -4 ((4- (ethylpropyloyloxyhexyloxy) benzoyloxy) -2-methylbenzene) sulfide) pentaerythritol ester, and is used for adjusting the rheological properties of printing ink and the rate of thermo-reversible deformation of liquid crystal elastomer film.
3. The method for preparing a flexible tactile feedback array based on liquid crystal elastomer actuation according to claim 1, wherein the catalyst in step S1 is di-n-propylamine or triethylamine, and the photoinitiator in step S2 is benzoin dimethyl ether or a photoinitiator 819.
4. The method of claim 1, wherein the molar ratio of 1, 4-bis- [4- (6-acryloyloxyhexyloxy) benzoyloxy ] -2-methylbenzene to 2,2' - (1, 2-ethanediylbisixoxy) bisethanethiol in the step S2 is 1.1, and the polymer obtained by the complete reaction is a number average degree of polymerization of 10 according to a stoichiometric ratio.
5. The method of claim 1, wherein the poly-liquid crystal alkene molecules in step S3 are present in a mass fraction of 5%.
6. The method for preparing a flexible tactile feedback array based on liquid crystal elastomer actuation according to claim 1, wherein the preset temperature in the step S3 is 60 ℃, the temperature for adding the 3D printing ink into the 3D printing cartridge for heating in the step S4 is 70 ℃, and the heating time is 1h.
7. The method for preparing a flexible tactile feedback array based on liquid crystal elastomer actuation according to claim 1, wherein the step S4 of printing the heated 3D printing ink on the glass substrate which is spin coated with a thin layer of polyvinyl alcohol is performed at a pressure of 80psi and a speed of 1-10mm/S.
8. The method of claim 1, wherein the uv light in step S4 has a wavelength of 365nm.
9. The method for preparing a flexible tactile feedback array based on liquid crystal elastomer actuation according to claim 1, wherein the time for continuing the reaction of the flexible tactile feedback structure under ultraviolet light in step S5 is 120min.
10. The method of claim 1, wherein the flexible substrate in step S6 or the polymer protective layer in step S7 is made of one of polyethylene terephthalate, polyimide, polydimethylsiloxane, polyurethane, polycarbonate, and uni-or biaxially oriented polypropylene.
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