A flexible actuator with reconfigurable deformation and self-locking shape and 4D printing method thereof

Abstract

A reconfigurable deformable and self-shaped flexible actuator and a 4D printing method thereof, wherein the flexible actuator comprises a tubular polymer, the middle of the tubular polymer is filled with a low melting point alloy, the tubular polymer at both ends of the low melting point alloy is sealed by an adhesive, and an outer coating is provided on the outer side of the tubular polymer; the 4D printing method comprises firstly coaxially 4D printing of the tubular polymer and the low melting point alloy, then adhesive sealing at both ends, then single domain treatment of the liquid crystal elastic polymer LCE, and finally surface coating treatment of the tubular polymer; the present invention utilizes the thermal deformation of the liquid crystal elastomer and the high rigidity of the low melting point alloy to realize the self-shaped locking of the flexible actuator after deformation; the printing method adopts the process means of coaxial printing to realize the accurate and controllable manufacturing of the internal and external structures; the reconfigurable deformable and self-shaped flexible actuator can be widely used in technical fields such as medical applications, auxiliary work, bionic motion, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of bionic manufacturing in micro-nano engineering, and specifically relates to a flexible actuator with reconfigurable deformation and self-locking shape and a 4D printing method thereof. Background Art

[0002] Flexible actuators have important application value in medical applications, auxiliary work, bionic motion and other fields due to their soft and biofriendly characteristics. Ideal flexible actuators have the characteristics of large deformation, high force, reversible deformation, fast response, low energy consumption, multiple repeatability and precise control.

[0003] At present, flexible actuators usually use a polymer or shape memory alloy that can deform under external stimulation (such as magnetism, heat, light, electricity, etc.) as a material. Flexible actuators made of ferroelectric polymers can reach a stress of 45MPa and a stiffness of 400MPa, but usually require a voltage greater than 1kV to drive and are prone to yielding; flexible actuators made of liquid crystal elastomers have good response time (10ms when driven by an electric field) and large strain (4% when driven by an electric field and up to 45% when driven by heat), but low efficiency and thermal deformation are usually slow; flexible actuators made of conductive polymers have a maximum stress of 34MPa (up to 5MPa in general), can work at low voltage (about 2V), and have a stiffness of up to 1GPa, but deformation is slow and requires packaging. However, the skeletal muscles of organisms are attached to the bones, and rely on the high stiffness of the bones themselves to achieve posture maintenance during the actuation process. They can maintain self-locking of the shape with high stiffness to ensure the motion control of the organism.

[0004] Although most flexible actuators can reach or even exceed the performance of biological muscles in deformation and stress, they often cannot maintain their shape when the external field loading is removed during deformation, and require continuous supply of external energy, which affects the practical application of flexible actuators. Therefore, how to realize flexible actuators with shape self-locking characteristics is still a major problem in their engineering applications. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a flexible actuator with reconfigurable deformation and shape self-locking and a 4D printing method thereof, so as to achieve shape self-locking after deformation.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A reconfigurable deformable and self-locking flexible actuator comprises a tubular polymer 1, the middle of the tubular polymer 1 is filled with a low melting point alloy 2, the tubular polymer 1 at both ends of the low melting point alloy 2 is sealed with an adhesive 3, and an outer coating 4 is provided on the outer side of the tubular polymer 1.

[0008] The tubular polymer 1 is a liquid crystal elastomer (LCE); the low melting point alloy 2 is a bismuth-lead-tin alloy having a melting point slightly higher than the contraction actuation temperature of LCE; the adhesive 3 is a silicone adhesive, and the outer coating 4 is a polydopamine (PDA) coating.

[0009] When in the initial state, the flexible actuator as a whole maintains its shape due to the high stiffness of the inner layer of the low-melting-point alloy 2; when the near-infrared laser source 9 is used to irradiate a part of the tubular polymer 1, the light absorption and heat generation characteristics of the outer coating 4 are used to drive the local contraction and deformation of the thermally actuated tubular polymer 1; continued irradiation to increase the temperature will cause the low-melting-point alloy 2 to melt, and the local contraction and deformation of the tubular polymer 1 will manifest as a bending of the overall structure in this part, thereby realizing the controllable driving of the flexible actuator under light regulation; thereafter, the near-infrared laser source 9 is removed, and the temperature drops to first solidify the low-melting-point alloy 2, so that the overall structure remains in the deformed shape, and its stiffness is maintained by the stiffness of the low-melting-point alloy 2, thereby realizing the self-locking of the shape of the flexible actuator after deformation; after completing this deformation, complex deformations such as multiple bending and double-sided bending are realized by irradiating different positions, and the bending of the other side is realized by irradiating the near-infrared laser source 9 at another position, thereby realizing the reconfigurable deformation of the flexible actuator.

[0010] A 4D printing method for a reconfigurable deformable and self-locking flexible actuator comprises the following steps:

[0011] The first step is the coaxial 4D printing technology of the tubular polymer 1 and the low-melting-point alloy 2: the print head 5 used in the 4D printing method is divided into two layers, the outer layer is filled with LCE prepolymer slurry, and the inner layer is filled with liquid low-melting-point alloy 2, which is kept in liquid state under the heating action of the print head 5; during the printing process, the LCE prepolymer slurry and the liquid low-melting-point alloy 2 are coaxially printed on the plane 6 in the form of the outer layer LCE internal low-melting-point alloy, and are printed into a target shape by ink direct writing (DIW) printing; thereafter, the LCE prepolymer slurry is cooled on the plane 6 to form the tubular polymer 1, and the liquid low-melting-point alloy is cooled on the plane 6 to form the solid low-melting-point alloy 2, thereby obtaining the tubular polymer 1 filled with the low-melting-point alloy 2;

[0012] Step 2: Encapsulation of adhesive 3 at both ends: Use adhesive 3 to seal the openings at both ends of the tubular polymer 1 filled with the low-melting-point alloy 2, and place it in the air until the adhesive 3 solidifies;

[0013] The third step is to treat the liquid crystal elastic polymer LCE to be monodomainized: the obtained tubular polymer 1 filled with the low melting point alloy 2 is irradiated with 365 nm ultraviolet light 7 for 5 to 15 minutes to monodomainize the LCE;

[0014] The fourth step is surface coating treatment of the tubular polymer 1: immerse the tubular polymer 1 in a PDA solution 8 for 24 to 48 hours. The PDA solution 8 is a PDA solution prepared by dissolving dopamine hydrochloride and Tris base in water, wherein the dopamine hydrochloride is 0.2 g (1.05 mmol), the Tris base is 0.1 g (0.83 mmol), and the water is 100 mL. Then rinse it three times with deionized water and dry it to obtain a tubular polymer with a PDA coating, which is a flexible actuator with reconfigurable deformation and shape self-locking.

[0015] The beneficial effects of the present invention are as follows: the reconfigurable deformable and shape-self-locking flexible actuator of the present invention utilizes the thermal deformation of liquid crystal elastomers and the high stiffness of low-melting-point alloys to achieve shape self-locking of the flexible actuator after deformation; the 4D printing method of the reconfigurable deformable and shape-self-locking flexible actuator adopts ink direct writing technology, dip coating and other process means to achieve accurate and controllable manufacturing of internal and external structures. The reconfigurable deformable and shape-self-locking flexible actuator of the present invention can be widely used in medical applications, auxiliary work, bionic motion and other technical fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1-1 A three-dimensional cross-sectional schematic diagram of the flexible actuator with reconfigurable deformation and self-locking shape according to the present invention; Figure 1-2 It is a two-dimensional cross-sectional schematic diagram of the flexible actuator with reconfigurable deformation and self-locking shape of the present invention.

[0017] Figure 2-1 It is a schematic diagram of the deformation of the reconfigurable deformable and self-locking flexible actuator of the present invention when it is partially irradiated by laser; Figure 2-2 It is a schematic diagram of the deformation of the reconfigurable deformable and shape-self-locking flexible actuator of the present invention when another position is irradiated by laser after the first deformation.

[0018] Figure 3 Schematic diagram of the 4D printing method of the reconfigurable deformable and shape-self-locking flexible actuator of the present invention.

[0019] Figure 4 This is a schematic diagram of the present invention using adhesives to seal both ends of a tubular polymer.

[0020] Figure 5 Schematic diagram of the monodomainization process of the tubular polymer of the present invention.

[0021] Figure 6 It is a schematic diagram of the coating treatment on the surface of the flexible actuator according to the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the accompanying drawings.

[0023] Reference Figure 1-1 , Figure 1-2A flexible actuator based on reconfigurable deformation and shape self-locking includes a tubular polymer 1, the middle of the tubular polymer 1 is filled with a low melting point alloy 2, the tubular polymer 1 at both ends of the low melting point alloy 2 is encapsulated by an adhesive 3, and an outer coating 4 is provided on the outside of the tubular polymer 1.

[0024] The tubular polymer 1 is a liquid crystal elastomer (LCE); the low-melting-point alloy 2 is a low-melting-point alloy such as a bismuth-lead-tin alloy having a melting point slightly higher than the contraction actuation temperature of LCE; the adhesive 3 is a material used for bonding such as silicone glue, and the outer coating 4 is a photothermal material such as a polydopamine (PDA) coating.

[0025] When in the initial state, the flexible actuator as a whole maintains its shape due to the high rigidity of the low melting point alloy 2 and does not deform due to its own weight, stretching, etc. Figure 1-1 As shown; when a near-infrared laser source 9 is used to irradiate a part of the tubular polymer 1, the heat-absorbing and heating characteristics of the outer coating 4 are utilized to drive the local contraction and deformation of the thermally actuated tubular polymer 1; since the melting point of the low-melting-point alloy 2 is higher than the isotropic transition temperature of the tubular polymer 1, continued irradiation to increase the temperature will cause the low-melting-point alloy 2 to melt, and the local contraction and deformation of the tubular polymer 1 will manifest as a bending of the overall structure in this part, as shown in FIG. Figure 2-1 As shown, the controllable driving of the flexible actuator under light regulation is realized; then the near-infrared laser source 9 is removed. Since the melting point of the low-melting-point alloy 2 is higher than the isotropic transition temperature of the liquid crystal elastomer, the temperature drops to first solidify the low-melting-point alloy 2, so that the overall structure remains in the deformed shape, and its stiffness can be maintained by the stiffness of the low-melting-point alloy 2, so that the shape of the flexible actuator after deformation is self-locking; after completing this deformation, complex deformations such as multiple bending and bilateral bending can be realized by irradiating different positions, such as Figure 2-2 As shown, the bending of the other side is achieved by irradiating the near-infrared laser source 9 at another position, thereby realizing the reconfigurable deformation of the flexible actuator.

[0026] A 4D printing method for a reconfigurable deformable and self-locking flexible actuator comprises the following steps:

[0027] The first step is the coaxial 4D printing technology of the tubular polymer 1 and the low-melting-point alloy 2: the print head 5 used in the 4D printing method is divided into two layers, the outer layer is filled with LCE prepolymer slurry, and the inner layer is filled with liquid low-melting-point alloy 2, which is kept in liquid state under the heating action of the print head 5. During the printing process, the LCE prepolymer slurry and the liquid low-melting-point alloy 2 are coaxially printed on the plane 6 in the form of the outer layer LCE inner low-melting-point alloy, and are printed into a target shape by ink direct writing (DIW) printing; thereafter, the LCE prepolymer slurry is cooled on the plane 6 to form the tubular polymer 1, and the liquid low-melting-point alloy 2 is cooled on the plane 6 to form a solid low-melting-point alloy 2, as shown in FIG. Figure 3 As shown, a tubular polymer 1 filled with a low melting point alloy 2 is obtained;

[0028] The second step is to seal the two ends with adhesive 3: Use adhesive 3 to seal the openings at both ends of the tubular polymer 1 filled with the low melting point alloy 2, and place it in the air until the adhesive 3 solidifies. Figure 4 As shown;

[0029] The third step is to treat the liquid crystal elastic polymer LCE to be monodomainized: the obtained tubular polymer 1 filled with the low melting point alloy 2 is irradiated with 365 nm ultraviolet light 7 for 5 to 15 minutes to monodomainize the LCE, such as Figure 5 As shown;

[0030] Step 4: Surface coating treatment of the tubular polymer 1: Immerse the tubular polymer 1 in the PDA solution 8 for 24 to 48 hours. Figure 6 As shown, PDA solution 8 is a PDA solution prepared by dissolving dopamine hydrochloride and Tris base in water, wherein dopamine hydrochloride 0.2 g (1.05 mmol), Tris base 0.1 g (0.83 mmol), and water 100 mL, and then rinsed three times with deionized water and dried to obtain a tubular polymer with a PDA coating, which is a flexible actuator with reconfigurable deformation and shape self-locking.

[0031] The reconfigurable deformable and shape-self-locking flexible actuator structure designed in the present invention overcomes the problem that traditional flexible actuators cannot maintain their shape after deformation. The 4D printing process is used to achieve accurate and controllable manufacturing of the designed structure, which can be applicable to a wide range of needs in the medical and bionic fields.

Claims

1. A 4D printing method for a reconfigurable deformable and self-locking flexible actuator, characterized in that: The reconfigurable deformable and self-locking flexible actuator comprises a tubular polymer (1), the middle of the tubular polymer (1) is filled with a low melting point alloy (2), the inside of the tubular polymer (1) at both ends of the low melting point alloy (2) is sealed with an adhesive (3), and the outside of the tubular polymer (1) is provided with an outer coating (4); The tubular polymer (1) is a liquid crystal elastomer (LCE); the low melting point alloy (2) is a bismuth-lead-tin alloy having a melting point slightly higher than the contraction actuation temperature of LCE; the adhesive (3) is a silicone adhesive, and the outer coating (4) is a polydopamine (PDA) coating; The 4D printing method comprises the following steps: The first step is the coaxial 4D printing technology of the tubular polymer (1) and the low-melting-point alloy (2): the print head (5) used in the 4D printing method is divided into two layers, the outer layer is filled with LCE prepolymer slurry, and the inner layer is filled with liquid low-melting-point alloy (2), which is kept in liquid state under the heating action of the print head (5); during the printing process, the LCE prepolymer slurry and the liquid low-melting-point alloy are coaxially printed on the plane (6) in the form of the outer layer LCE and the inner low-melting-point alloy, and are printed into a target shape by ink direct writing (DIW) printing; thereafter, the LCE prepolymer slurry is cooled on the plane (6) to form the tubular polymer (1), and the liquid low-melting-point alloy is cooled on the plane (6) to form the solid low-melting-point alloy (2), thereby obtaining the tubular polymer (1) filled with the low-melting-point alloy (2); The second step is sealing with adhesive (3) at both ends: using adhesive (3) to seal the openings at both ends of the tubular polymer (1) filled with the low melting point alloy (2) and leaving it in the air until the adhesive solidifies; The third step is to treat the liquid crystal elastic polymer LCE to be monodomainized: the obtained tubular polymer (1) filled with the low melting point alloy (2) is irradiated with 365 nm ultraviolet light (7) for 5 to 15 minutes to monodomainize the LCE; The fourth step is surface coating treatment of the tubular polymer (1): the tubular polymer (1) is immersed in a polydopamine (PDA) solution (8) for 24 to 48 hours. The polydopamine (PDA) solution (8) is a polydopamine (PDA) solution prepared by dissolving dopamine hydrochloride and Tris base in water, wherein 0.2 g (1.05 mmol) of dopamine hydrochloride, 0.1 g (0.83 mmol) of Tris base, and 100 mL of water. The tubular polymer is then rinsed three times with deionized water and dried to obtain a polydopamine (PDA) coated tubular polymer, which is a flexible actuator with reconfigurable deformation and self-locking shape.

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