4D printing bionic artificial limb and preparation method and application thereof

Abstract

The invention relates to a 4D printing bionic artificial limb and a preparation method and application thereof, and relates to the technical field of medical rehabilitation instruments, the bionic artificial limb comprises a bionic skeleton and a flexible driving unit; the flexible driving unit is located at a joint moving part of the bionic skeleton and is used for driving the bionic skeleton to move; the bionic artificial limb is integrally formed through 4D printing, the bionic skeleton is made of a shape memory composite material, and the flexible driving unit is made of a hydrogel driving material; the shape memory composite material comprises a shape memory polymer and a reinforcing material in a mass ratio of (80-95%): (5-20%); the hydrogel driving material comprises a thermo-sensitive polymer matrix, a stabilizer and a functional filler in a mass ratio of (50%-80%): (20%-40%): (3%-15%). The 4D printing bionic artificial limb has the dynamic adjusting capacity, and the change requirements of the residual limb under different conditions can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical rehabilitation equipment, in particular to a 4D printed bionic prosthesis and a preparation method and application thereof. BACKGROUND

[0002] With the development of science and technology, the technology of prostheses is constantly improving, and bionic prostheses bring hope to improve the quality of life of disabled people. Traditional prostheses have many limitations, such as poor adaptability, and cannot adaptively adjust according to the subtle changes of the residual limb, different activity states, and changes of the residual limb over time. This often leads to discomfort, affects the use effect of the prosthesis, and may even cause harm to the residual limb. At the same time, the function of traditional prostheses is relatively single, and it is difficult to accurately simulate the complex movement of the human body.

[0003] Although 3D printing technology has improved the problem of personalized customization of prostheses to some extent, it can manufacture a prosthesis part that fits the shape of the residual limb according to the three-dimensional scanning data of the patient's residual limb, but if only hard materials are used, it still needs to print several parts and then assemble them, which reduces the efficiency of prosthesis customization. At the same time, for prostheses controlled by external switches, their functionality is very limited, and they can often only achieve basic grasping function. Moreover, they lack dynamic adjustment capability and cannot meet the changing needs of the residual limb in different situations. SUMMARY

[0004] In order to solve one or more technical problems in the prior art, the present application provides a 4D printed bionic prosthesis and a preparation method and application thereof. The 4D printed bionic prosthesis proposed by the present application not only simulates the mechanical properties and structural characteristics of human bones, has good support and carrying capacity, but also can change shape under external stimulation to adapt to different motion scenarios and needs.

[0005] In a first aspect, the present application provides a 4D printed bionic prosthesis, comprising: a bionic skeleton and a flexible driving unit; the flexible driving unit is located at the joint active part of the bionic skeleton and is used to drive the movement of the bionic skeleton; the bionic prosthesis is obtained by 4D printing integrated forming, the bionic skeleton is made of shape memory composite material, and the flexible driving unit is made of hydrogel driving material;

[0006] The shape memory composite material comprises shape memory polymer and reinforcing material in a mass ratio of (80% to 95%):(5% to 20%);

[0007] The hydrogel driving material comprises a temperature-sensitive polymer matrix, a stabilizer and a functional filler in a mass ratio of (50% to 80%):(20% to 40%):(3% to 15%).

[0008] Preferably, the shape memory polymer comprises at least one of shape memory polyethylene, shape memory polypropylene, shape memory polylactic acid, shape memory polycaprolactone, shape memory polyurethane, shape memory poly-L-lactic acid.

[0009] More preferably, the shape memory polymer is composed of shape memory polymers with two different glass transition temperatures.

[0010] Preferably, the reinforcing material comprises at least one of carbon fibers, nanosilica, magnetic nanoparticles.

[0011] More preferably, the length of the carbon fibers is 3-5 mm, and the diameter is 7-10 μm.

[0012] More preferably, the particle size of the nanosilica is 50-150 nm.

[0013] Preferably, the temperature-sensitive polymer matrix comprises at least one of poly-N-isopropyl acrylamide, polyacrylic acid, polymethacrylic acid.

[0014] Preferably, the stabilizer comprises at least one of polyethylene glycol, gelatin, polyacrylamide, carboxymethyl cellulose;

[0015] The functional filler comprises at least one of carbon nanotubes, graphene, silicon dioxide, and ferroferric oxide.

[0016] Preferably, the hydrogel driving material comprises a temperature-sensitive polymer matrix, a stabilizer, and a functional filler in a mass ratio of (60%-70%):(25%-35%):(5%-10%).

[0017] More preferably, the flexible driving unit has a response temperature of 20-35℃ and a response humidity of 40%-70%.

[0018] In a second aspect, the present application also provides a preparation method of a 4D printed bionic prosthesis, comprising the following steps:

[0019] (1) heating a shape memory polymer to a molten state, then adding a reinforcing material and mixing to obtain a shape memory composite material; wherein the mass ratio of the shape memory polymer and the reinforcing material is (80%-95%):(5%-20%);

[0020] (2) adding a temperature-sensitive polymer matrix, a stabilizer, and a functional filler in a mass ratio of (50%-80%):(20%-40%):(3%-15%) to water and mixing to obtain a mixed solution; then subjecting the mixed solution to freeze-thaw cycle treatment to obtain a hydrogel driving material;

[0021] (3) using the 4D printing technology to print the shape memory composite material to obtain a bionic skeleton, and then using the 4D printing technology to print the hydrogel driving material at a predetermined position of the bionic skeleton to obtain the bionic prosthesis; wherein the predetermined position is a joint movement part of the bionic skeleton, and the predetermined position of the bionic prosthesis is a flexible driving unit.

[0022] Preferably, in step (2), the number of cycles of the freeze-thaw cycle treatment is 3-4 times.

[0023] More preferably, the single freezing time in the freeze-thaw cycle treatment is 1.5-2.5 h, and the single thawing time is 0.8-1.8 h.

[0024] Preferably, the predetermined position is the hinge side or the stretching side of the joint movement part.

[0025] Preferably, the thickness of the flexible driving unit is 0.4-1.5 mm.

[0026] Preferably, the bionic skeleton is obtained by using the fused deposition modeling technology, and the flexible driving unit is obtained by using the direct ink writing technology.

[0027] In a third aspect, the present application also provides a 4D printed bionic prosthesis for use in the field of limb injury rehabilitation.

[0028] Preferably, a pressure sensor and a strain sensor are installed at a preset installation position of the bionic prosthesis, and the pressure sensor and the strain sensor are connected to a signal processing module, respectively; wherein the pressure sensor and the strain sensor are used to monitor the contact pressure of the bionic prosthesis with the outside world and the deformation of the bionic prosthesis itself in real time, respectively, and transmit the collected monitoring signals to the signal processing module; the signal processing module is used to analyze the received monitoring signals to determine the driving instructions of the flexible driving unit, so that the bionic prosthesis is adjusted.

[0029] Compared with the prior art, the present application has at least the following beneficial effects:

[0030] (1) The 4D printed bionic prosthesis prepared by the present application can sense the changes of the residual limb in real time and make adaptive adjustments, ensuring that it can closely fit the residual limb in various situations, greatly improving the comfort and stability of wearing. This helps to reduce the pain, wear and other complications caused by poor fitting of the prosthesis, enabling the disabled to use the prosthesis for a longer period of time and more comfortably, and has excellent adaptability.

[0031] (2) The 4D printed bionic prosthesis prepared by the application has the functions of personalized customization and dynamic optimization. By using the 4D printing technology, the bionic prosthesis can be customized according to the unique residual limb condition of each patient. At the same time, the shape memory composite material allows the bionic prosthesis to be dynamically optimized over time and under use conditions. This means that the bionic prosthesis can continuously adapt to the changes in the patient's body and use habits during use, always maintaining optimal performance, prolonging the service life of the bionic prosthesis, and reducing the cost and inconvenience of frequent replacement of the bionic prosthesis due to changes in the residual limb.

[0032] (3) The 4D printed bionic prosthesis prepared by the application can realize lightweight under the premise of ensuring strength and function through optimized design and material selection, thereby reducing the burden on the body. At the same time, its good motion simulation performance and self-adaptive adjustment capability make it easier for patients to use the bionic prosthesis, reducing the additional burden on other parts of the body due to compensation, and helping to protect the health of the patient. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments of the application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0034] The embodiments of the application provide a 4D printed bionic prosthesis, which comprises a bionic skeleton and a flexible driving unit; the flexible driving unit is located at a joint movement part of the bionic skeleton and is used for driving the movement of the bionic skeleton; the bionic prosthesis is obtained by 4D printing integrated forming, the bionic skeleton is made of a shape memory composite material, and the flexible driving unit is made of a hydrogel driving material.

[0035] The shape memory composite material comprises a shape memory polymer and a reinforcing material in a mass ratio of (80%-95%):(5%-20%);

[0036] The hydrogel driving material comprises a temperature-sensitive polymer matrix, a stabilizer and a functional filler in a mass ratio of (50%-80%):(20%-40%):(3%-15%).

[0037] It should be noted that the mass of the shape memory polymer accounts for 80% to 95% of the total mass of the shape memory composite material, for example, can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or 95%; the mass of the reinforcing material accounts for 5% to 20% of the total mass of the shape memory composite material, for example, can be 5%, 6%, 8%, 10%, 12%, 15%, 16%, 18% or 20%.

[0038] It should be noted that the mass of the temperature-sensitive polymer matrix accounts for 50% to 80% of the total mass of the hydrogel driving material, for example, can be 50%, 55%, 60%, 65%, 70%, 75% or 80%; the mass of the stabilizer accounts for 20% to 40% of the total mass of the hydrogel driving material, for example, can be 20%, 25%, 30%, 35% or 40%; the mass of the functional filler accounts for 3% to 15% of the total mass of the hydrogel driving material, for example, can be 3%, 5%, 6%, 8%, 10%, 12% or 15%.

[0039] In the embodiments of the present application, the 4D printed bionic prosthesis adopts shape memory polymer and reinforcing material to prepare bionic bone structure, has good mechanical properties and shape memory performance, can change shape under external stimulation, adapt to different motion scenes, and provide more natural and flexible motion experience for patients. The flexible driving unit adopts hydrogel driving material, can generate driving force when the temperature or humidity changes, drive the joint movement of the bionic prosthesis, has better flexibility and adaptability compared with the traditional rigid driving mode, and reduces the damage to the patient's body.

[0040] According to some preferred embodiments, the shape memory polymer includes at least one of shape memory polyethylene, shape memory polypropylene, shape memory polylactic acid, shape memory polycaprolactone, shape memory polyurethane, and shape memory poly-L-lactic acid.

[0041] According to some preferred embodiments, the reinforcing material includes at least one of carbon fiber, nano-silicon dioxide, and magnetic nanoparticles.

[0042] In the embodiment of the present application, experiments have proved that if the amount of reinforcing material is less than 5%, the mechanical properties of the shape memory composite material are poor, and there are functional defects. Specifically, if the amount of carbon fiber is insufficient, the tensile strength and impact resistance of the shape memory composite material will decrease significantly, resulting in that the bionic skeleton cannot bear the weight of the human body; at the same time, it will also lead to insufficient conductivity of the shape memory composite material, which cannot effectively couple with the strain sensor and the like installed on the bionic prosthesis. If the amount of nano-silicon dioxide is insufficient, the crystallization rate of the shape memory polymer will slow down, and the recovery time will be prolonged, thereby affecting the response speed of the bionic prosthesis to the changes of the residual limb; at the same time, it will lead to an increase in the creep rate of the shape memory composite material at high temperature (temperature exceeding the glass transition temperature) (> 10%), which may cause unexpected deformation of the joint structure after long-term use.

[0043] In the embodiment of the present application, experiments have proved that if the amount of reinforcing material is more than 20%, the processing performance of the shape memory composite material will deteriorate, and the shape memory function will decay. Specifically, too much reinforcing material will cause the viscosity of the shape memory composite material in the molten state to rise sharply, thereby increasing the extrusion resistance during 4D printing, causing nozzle blockage or poor layer bonding, and reducing the processing performance; at the same time, too much reinforcing material will limit the movement ability of the molecular chain of the shape memory polymer, causing the glass transition temperature to rise, and a higher temperature is required to trigger the memory effect, thereby expanding the difference between the response temperature of the hydrogel driving material, affecting the synergistic adaptability; moreover, too much reinforcing material will also reduce the elastic recovery rate of the shape memory composite material, thereby causing the joint structure of the bionic prosthesis to be unable to fully recover to the original shape after multiple deformations, and the cumulative error will affect the motion accuracy. In addition, too much reinforcing material will increase the risk of agglomeration of nano-silicon dioxide particles, causing stress concentration points in the composite material and reducing the impact strength.

[0044] According to some more preferred embodiments, the shape memory composite material uses shape memory polymers with two different glass transition temperatures.

[0045] In the embodiment of the present application, the temperature of the hydrogel driving material is less than the glass transition temperature of the shape memory composite material, in order to avoid the deformation of the bionic skeleton and the flexible driving unit at the same time when the glass transition temperature of the shape memory composite material is reached, therefore a bionic skeleton with two glass transition temperatures is selected, the shape memory polymer with a higher glass transition temperature is used to provide support, and the shape memory polymer with a lower glass transition temperature is used to provide shape memory function, so that the bionic skeleton still has a certain rigidity after reaching the glass transition temperature, thereby reducing the deviation of the joint angle when the flexible driving unit is driven, to further ensure the joint motion accuracy.

[0046] In the present application, in order to realize controllable movement of the bionic artificial joint when the bionic skeleton and the flexible driving unit deform simultaneously, the swelling / shrinking strain of the hydrogel driving material and the recovery strain of the shape memory composite material can be designed by matching, so that the deformation amounts of the two are complementary. For example, the glass transition temperature of the shape memory composite material is 55℃ or 70℃, the hydrogel driving material shrinks by 15% at 55℃, the shape memory composite material recovers by 8%, and the total deformation amount is limited within 20% to avoid joint jamming.

[0047] According to some more preferred embodiments, in order to further ensure the joint movement accuracy, a metal limiting structure is also embedded at the joint of the bionic skeleton to limit the maximum bending angle of the flexible driving unit within 20°, thereby improving the controllability of the movement of the bionic artificial limb. It should be noted that the connecting member (such as a pin shaft or a bearing) at the joint of the bionic skeleton is made of metal or high-strength plastic and is installed in the reserved position after printing is completed, thereby retaining the structure-driving integration advantage of the 4D printed artificial limb and ensuring the joint movement accuracy and durability through the connecting member.

[0048] According to some more preferred embodiments, the reinforcing material includes carbon fibers and nanosilica in a mass ratio of 1:1.

[0049] In the embodiments of the present application, in order to avoid joint jamming caused by opposite directions of the bionic skeleton and the flexible driving unit when they deform simultaneously, magnetic nanoparticles can be added to the shape memory composite material to control the recovery direction through an external magnetic field and offset the hydrogel driving force; or the mapping relationship between temperature and action can be preprogrammed, and when the temperature is lower than the glass transition temperature of the bionic skeleton, the driving instruction of the flexible driving unit is executed, and when the temperature is higher than the glass transition temperature of the bionic skeleton, the shape memory recovery mode is switched to, so that the uncontrollable driving of the bionic artificial limb caused by the simultaneous deformation of the two can be avoided.

[0050] According to some more preferred embodiments, the length of the carbon fiber is 3-5 mm (for example, it can be 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm), and the diameter is 7-10 μm (for example, it can be 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm).

[0051] According to some more preferred embodiments, the particle size of the nanosilica is 50-150 nm (for example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm or 150 nm).

[0052] According to some preferred embodiments, the temperature-sensitive polymer matrix comprises at least one of poly-N-isopropyl acrylamide, polyacrylic acid, polymethacrylic acid.

[0053] According to some preferred embodiments, the stabilizer comprises at least one of polyethylene glycol, gelatin, polyacrylamide, carboxymethyl cellulose;

[0054] The functional filler comprises at least one of carbon nanotubes, graphene, silicon dioxide and ferroferric oxide.

[0055] According to some more preferred embodiments, the response temperature of the flexible driving unit is 20-35℃ (for example, it can be 20℃, 22℃, 25℃, 28℃, 30℃, 32℃ or 35℃), and the response humidity is 40%-70% (for example, it can be 40%, 45%, 50%, 55%, 60%, 65% or 70%).

[0056] In the embodiments of the present application, the temperature-sensitive polymer matrix shrinks hydrophobically to generate driving force when the temperature is higher than the lower critical solution temperature (LCST). Experiments have shown that if the amount of the temperature-sensitive polymer matrix is less than 50%, the LCST of the hydrogel driving material will be increased to above 35℃, close to the upper limit of the human body temperature, which will cause the driving response of the bionic prosthesis to be delayed in daily activities; if the amount of the temperature-sensitive polymer matrix is more than 80%, the swelling rate of the hydrogel driving material will be reduced, the driving deformation will be insufficient, and the mechanical strength will be reduced.

[0057] In the embodiments of the present application, the stabilizer has the effects of enhancing mechanical properties, realizing temperature-sensitive adjustment and improving network stability. Specifically, the hydroxyl groups of the stabilizer can form hydrogen bonds with the amide groups and carboxyl groups of the temperature-sensitive polymer matrix, thereby improving the tensile strength and toughness of the hydrogel driving material. The hydrophilicity of the stabilizer can reduce the LCST of the temperature-sensitive polymer matrix, so that it is closer to the human body temperature, realizes temperature-sensitive adjustment, and improves the driving sensitivity. The stabilizer can physically cross-link the molecular chains of the temperature-sensitive polymer matrix, reduce phase separation, and make the network structure of the hydrogel driving material more stable. Experiments have shown that if the amount of the stabilizer is less than 20%, the tensile strength of the hydrogel driving material will be less than 200kPa, the joint connection will be easily torn during driving; and the LCST adjustment effect will be insufficient, the response temperature will still be 32℃, and the matching with the human body temperature will be poor; but if the amount of the stabilizer is more than 40%, the hydrogel driving material will be excessively swollen by water absorption, the dimensional stability will be reduced during humidity driving, and the joint movement angle will be greatly deviated.

[0058] In the embodiments of the present application, the functional filler can improve the electrical conductivity, enhance the mechanical properties of the hydrogel driving material, accelerate heat conduction, and further improve the temperature response speed of the hydrogel driving material. Experiments have proved that if the amount of functional filler is less than 3%, the electrical conductivity of the hydrogel driving material is insufficient, less than 0.5 S / m, and the sensing feedback signal delay is >0.3 s; and the mechanical enhancement effect is weak, and the tensile strength is improved by <10%. If the amount of functional filler is more than 15%, the functional filler is seriously agglomerated, the internal porosity of the hydrogel driving material is increased, and the swelling rate fluctuates by >±8%, thereby causing the driving accuracy to decrease.

[0059] In the embodiments of the present application, the synergistic effect of the temperature-sensitive phase transition of the temperature-sensitive polymer matrix and the moisture absorption of the stabilizer / functionality filler, directly drives the joint movement through the volume change of the hydrogel driving material, drives the bionic prosthesis to move, and solves the problem that the responsiveness and strength of the existing prosthesis driving material are difficult to be considered. Specifically, the synergism of temperature sensitivity and mechanical properties is reflected in the temperature-sensitive shrinkage force of the temperature-sensitive polymer matrix and the hydrogen bond network of the stabilizer, so that the hydrogel generates sufficient deformation when driving and avoids breaking. The synergism of electrical conductivity and response is reflected in the fact that the conductive network of the functional filler can accelerate temperature conduction, shorten the temperature response time of the temperature-sensitive polymer matrix, and at the same time provide a signal transmission path for the sensing feedback system. The network interpenetration synergism is reflected in the interpenetration of the chemical network of the temperature-sensitive polymer matrix and the physical network of the stabilizer, and the formation of a "double continuous phase" structure after freezing and thawing, which improves the swelling-shrinking cycle stability by 50% compared with a single network.

[0060] In the embodiments of the present application, the response temperature of the hydrogel driving material is 20-35°C, and the response humidity is 40%-70%, which covers the environmental temperature (such as indoor and outdoor temperature difference, human body movement heat production, etc.) and conventional humidity fluctuation scenarios (such as sweating, rainy days, etc.) of human daily activities, has stronger adaptability and higher driving stability, so that the flexible driving unit made of the hydrogel driving material and the shape memory-based bionic skeleton are integrated to realize the integration of sensing and driving. Specifically, when the environmental temperature exceeds the LCST of the hydrogel driving material, the molecular chain changes from an extended state to a curled state, the hydrogel rapidly shrinks, and a tensile force is generated to drive the joint to bend; when the environmental temperature decreases, the molecular chain swells again, and the joint resets. The introduction of the stabilizer and the functional filler increases the water absorption of the hydrogel driving material, and when the environmental humidity increases, the hydrogel absorbs water and expands, generating a pushing force; when the environmental humidity decreases, the water loss causes the hydrogel to shrink, generating a pulling force, so that the joint movement can be driven by the pushing and pulling action.

[0061] According to some preferred embodiments, the hydrogel driving material includes a temperature-sensitive polymer matrix, a stabilizer, and a functional filler in a mass ratio of (60%-70%):(25%-35%):(5%-10%).

[0062] It should be noted that the mass of the temperature-sensitive polymer matrix accounts for 60-70% of the total mass of the hydrogel driving material, for example, it can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69% or 70%; the mass of the stabilizer accounts for 25-35% of the total mass of the hydrogel driving material, for example, it can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%; the mass of the functional filler accounts for 5-10% of the total mass of the hydrogel driving material, for example, it can be 5%, 6%, 7%, 8%, 9% or 10%.

[0063] The application also provides a preparation method of the 4D printed bionic prosthesis, which comprises the following steps:

[0064] (1) heating a shape memory polymer to a molten state, then adding a reinforcing material to mix, to obtain a shape memory composite material; wherein the mass ratio of the shape memory polymer and the reinforcing material is (80%-95%):(5%-20%);

[0065] (2) adding a temperature-sensitive polymer matrix, a stabilizer and a functional filler with a mass ratio of (50%-80%):(20%-40%):(3%-15%) into water to mix, to obtain a mixed solution; then performing freeze-thaw cycle treatment on the mixed solution, to obtain a hydrogel driving material;

[0066] (3) printing the shape memory composite material by using a 4D printing technology to obtain a bionic skeleton, then printing the hydrogel driving material at a predetermined position of the bionic skeleton by using the 4D printing technology, to obtain a bionic prosthesis; wherein the predetermined position is a joint movement part of the bionic skeleton, and the predetermined position of the bionic prosthesis is a flexible driving unit.

[0067] In the embodiment of the application, the shape memory composite material is prepared into a bionic skeleton by using a 4D printing technology, the shape memory composite material takes a shape memory polymer as a matrix, adds reinforcing materials such as carbon fibers and nano silicon dioxide, and by changing the types, contents and distributions of the reinforcing materials, the mechanical properties and shape memory properties of the bionic skeleton structure can be adjusted, so that the bionic skeleton structure (i.e. the bionic skeleton) simulates the mechanical properties and structural characteristics of human bones, has good supporting and bearing capacity, and can change shape under external stimulation to adapt to different movement scenarios and requirements. By controlling the proportion of the temperature-sensitive polymer matrix, the stabilizer and the functional filler, the hydrogel driving material can swell or shrink when the temperature or humidity changes, so as to generate a driving force to drive the joint movement of the bionic prosthesis. The flexible driving unit is connected with the bionic skeleton structure, and can realize flexible movement of the bionic prosthesis.

[0068] In the embodiments of the present application, the physical crosslinking is achieved by freeze-thaw cycle treatment. The physical crosslinking has good process compatibility, does not require initiators or crosslinking agents, avoids potential harm to the human body caused by chemical residues, and is suitable for medical implantation scenarios (for example, the contact part of the bionic prosthesis and the residual limb). The crosslinking density can be adjusted by the number of freeze-thaw cycles, reversible regulation is achieved, and the response time of the hydrogel driving material is shorter than that of the chemically crosslinked hydrogel driving material. Therefore, the physical crosslinking is more suitable for dynamic driving requirements. In addition, the hydrogel driving material with a physical crosslinking network (including hydrogen bonds and π-π stacking) obtained by the method can rearrange under external stimulation. The driving performance of the physical crosslinking hydrogel decreases much less than that of the chemically crosslinked hydrogel after multiple cycles. Therefore, the hydrogel driving material has the potential for damage self-repair.

[0069] According to some preferred embodiments, in step (2), the mass ratio of the sum of the mass of the temperature-sensitive polymer matrix, the stabilizer and the functional filler to the mass of water is 1:(1-10) (for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10), preferably 1:(2-5).

[0070] In the embodiments of the present application, the amount of water is the main factor determining the viscosity of the mixed solution. The higher the concentration, the greater the viscosity. However, when the concentration is too high, the printing difficulty will increase. Therefore, the mass ratio of the sum of the mass of the temperature-sensitive polymer matrix, the stabilizer and the functional filler to the mass of water is selected to be 1:(1-10).

[0071] According to some preferred embodiments, in step (2), the number of freeze-thaw cycle treatments is 3-4 times.

[0072] In the embodiments of the present application, the physical crosslinking is achieved by freeze-thaw cycle treatment. The essence is to induce the rearrangement of polymer molecular chain segments to form crystalline domains or hydrogen bond networks by low temperature. Experiments have shown that if the number of cycles is less than 3 times, only part of the molecular chain segments are rearranged, the physical crosslinking points are insufficient, the crosslinking degree is low, and the tensile strength and swelling rate of the hydrogel driving material are affected. However, if the number of cycles is more than 4 times, the crosslinking density is too high, the molecular chain movement ability is limited, the hydrogel rigidity increases and the toughness decreases, which in turn prolongs the driving response time. At the same time, when the number of cycles is too high, the excessive crosslinking reduces the breaking elongation of the hydrogel driving material, and brittle fracture easily occurs during driving, resulting in deterioration of the mechanical properties. In addition, the high crosslinking density limits the temperature-sensitive phase transition ability of the temperature-sensitive polymer matrix molecular chain, reduces the swelling-shrinking rate during temperature driving, and causes the response sensitivity to decrease. Furthermore, the high crosslinking density increases the viscosity of the hydrogel driving material, increases the extrusion resistance during printing, and causes the printing adaptability to deteriorate.

[0073] According to some more preferred embodiments, the single freezing time in the freeze-thaw cycle treatment is 1.5-2.5 h (for example, it can be 1.5 h, 2 h or 2.5 h), and the single thawing time is 0.8-1.8 h (for example, it can be 0.8 h, 1 h, 1.5 h or 1.8 h).

[0074] In the embodiments of the present application, it has been proved by experiments that if the single freezing time in each cycle is less than 1 h, the molecular chain segments are not fully crystallized, and the physical crosslinking points are insufficiently formed; but if it is longer than 3 h, the ice crystals grow excessively, which can pierce the hydrogel network structure, resulting in an increase in internal porosity and easy structural collapse during swelling. If the single thawing time in each cycle is less than 0.5 h, the ice crystals are not completely melted, and the residual small ice crystals can become stress concentration points, reducing the impact resistance of the material; but if the time is longer than 2 h, the molecular chains are excessively relaxed at room temperature, and the formed crosslinking points can be partially dissociated, resulting in fluctuations in crosslinking density and affecting the elastic modulus of the hydrogel.

[0075] According to some preferred embodiments, the predetermined position is the hinge side or the stretching side of the joint movement part.

[0076] According to some preferred embodiments, the thickness of the flexible driving unit is 0.4-1.5 mm (for example, it can be 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm or 1.5 mm).

[0077] It should be noted that the thickness of the flexible driving unit needs to be designed to match the joint movement amplitude, for example, the thickness of the flexible driving unit at the knee joint is usually 0.8-1.2 mm, and the thickness of the flexible driving unit at the ankle joint is usually 0.4-0.6 mm, so as to avoid an increase in joint movement resistance due to excessive thickness. At the same time, the driving force of the flexible driving unit will increase with the increase in thickness; but when the thickness exceeds the critical value, the self-weight and stiffness of the hydrogel driving material will increase, which will offset part of the driving force, and the increase in thickness will also lengthen the heat conduction path, resulting in a prolonged response.

[0078] According to some preferred embodiments, the biomimetic skeleton is obtained by using the fused deposition modeling technology, and the flexible driving unit is obtained by using the direct ink writing technology.

[0079] In the embodiment of the present application, the bionic skeleton is first printed by the fused deposition modeling technology, and then the flexible driving unit is printed at the predetermined position of the skeleton by the direct ink writing technology. The interface is combined during the printing process. The micro-roughness on the surface of the bionic skeleton (such as the layer lines formed by the fused deposition modeling technology) and the fluidity of the hydrogel driving material (such as the wettability during extrusion by the direct ink writing technology) interact with each other. The molecular chains of the temperature-sensitive polymer matrix penetrate into the pores of the bionic skeleton to realize physical entanglement. At the same time, the carboxyl and amide groups in the hydrogel driving material spontaneously combine with the hydroxyl groups on the surface of the skeleton to form hydrogen bonds. These forces are generated synchronously during the solidification process of the hydrogel, and a firm connection can be formed without additional chemical reagents or processing. In order to further improve the interface bonding strength of the 4D printed bionic prosthesis, the 4D printed bionic prosthesis is further subjected to a freeze-thaw cycle treatment.

[0080] The present application also provides an application of the 4D printed bionic prosthesis, which is applied to the field of limb injury rehabilitation.

[0081] According to some preferred embodiments, the pressure sensor and the strain sensor are installed at the preset installation positions of the bionic prosthesis, and the pressure sensor and the strain sensor are respectively connected with the signal processing module; wherein the pressure sensor and the strain sensor are respectively used for real-time monitoring of the contact pressure of the bionic prosthesis with the outside world and the deformation condition of the bionic prosthesis itself, and transmitting the collected monitoring signals to the signal processing module; the signal processing module is used for analyzing the received monitoring signals, determining the driving instructions of the flexible driving unit, so that the bionic prosthesis is adjusted.

[0082] In the embodiment of the present application, the pressure sensor, the strain sensor and the signal processing module constitute a sensing feedback system. The pressure sensor and the strain sensor are distributed at the key positions of the bionic prosthesis, and are connected with the signal processing module through wires, for real-time monitoring of the contact pressure of the prosthesis with the outside world and the deformation condition of the prosthesis itself, and transmitting the monitoring signals to the signal processing module. The signal processing module analyzes and processes the signals, controls the driving of the flexible driving unit according to the preset program, and makes the bionic prosthesis make corresponding adaptive adjustment to solve the problems of poor adaptability and single function of the existing prosthesis. Through the 4D printing technology, the prosthesis can be adaptively adjusted according to the real-time state of the residual limb, different activity needs and time changes, and at the same time, the complex motion function of the human body limb is highly simulated, so as to provide a more comfortable, efficient and functionally rich prosthesis solution for the disabled.

[0083] In a specific embodiment, when the ambient temperature reaches the glass transition temperature of the shape memory composite material, the bionic skeleton and the flexible driving unit may deform at the same time. In order to avoid their simultaneous deformation and achieve controllable movement of the bionic prosthesis, a sensing feedback system composed of a pressure sensor, a strain sensor and a signal processing module can be used for real-time intervention. Specifically, the contact pressure between the bionic prosthesis and the outside world is monitored in real time by the pressure sensor, and the self-deformation is monitored in real time by the strain sensor. When the ambient temperature exceeds the glass transition temperature of the shape memory composite material, the signal processing module reduces the driving voltage of the flexible driving unit or cuts off the heat source, and controls the driving strain within the elastic range of the shape memory composite material.

[0084] In a specific embodiment, the shape memory effect of the 4D printed bionic prosthesis is mainly activated in the following scenarios: a. Long-term adaptation of residual limb morphology changes: When the patient's residual limb continuously changes in size (for example, the circumference changes by more than 5%) due to muscle atrophy, edema, etc., the glass transition temperature of the shape memory composite material is triggered by external heating (for example, hot water above 60℃ or electromagnetic induction) to change from a glassy state to a high-elastic state, and the joint structure (such as the angle of the socket and the arc of the skeletal support) is re-sized to achieve permanent adaptive adjustment. b. Daily life: When the patient's residual limb contacts warm water, the temperature of the warm water can drive the hydrogel driving material to change in volume, but it must be strictly lower than the glass transition temperature of the shape memory composite material to avoid simultaneous deformation of the two in daily use. It should be noted that although the glass transition temperature of shape memory polyethylene and shape memory polypropylene is lower than room temperature, shape memory polyethylene and shape memory polypropylene do not deform at room temperature. This is because the crystalline region of this polymer is much higher than the rigidity and dimensional stability provided at the glass transition temperature, which inhibits the large-scale flow of amorphous regions. Moreover, its deformation is mechanical and passive, and the temperature above the glass transition temperature only makes it easier for the chain segment to move, rather than being driven. Therefore, although its glass transition temperature is lower than the response temperature of the hydrogel driving material, it will not cause simultaneous deformation.

[0085] In a specific embodiment, due to the repeated swelling and shrinking of the hydrogel driving material and the restoring force of the shape memory composite material, the interface is prone to debonding and structural fatigue damage. In order to solve this problem, the bionic prosthesis can be periodically frozen at low temperature (for example, -20℃) to restore the interfacial crosslinking density, and at the same time, the carboxyl groups in the hydrogel driving material form hydrogen bonds with the hydroxyl groups on the surface of the bionic skeleton, thereby improving the interfacial bonding strength.

[0086] In the present application, the "and / or" appearing between multiple technical features means that these technical features are connected in the relationship of "and / or", indicating that it can be any one of these technical features, or a combination of any two or more of these technical features.

[0087] The present application will be further described below by way of examples, but the scope of protection of the present application is not limited to these examples.

[0088] Example 1

[0089] A 4D-printed bionic prosthesis and a preparation method and application thereof, comprising:

[0090] (1) Preparation of shape memory composite material: shape memory polylactic acid and shape memory polycaprolactone with a mass ratio of 6:4 are heated to 150℃ for melting, then chopped carbon fibers (length of 5mm, diameter of 8μm) and nanosilica (particle size of about 50nm) are added and mixed at a speed of 800rpm for 30min, and then cooled to room temperature to obtain shape memory composite material particles; wherein the mass ratio of shape memory polymer, chopped carbon fiber and nanosilica is 90%:5%:5%;

[0091] (2) Preparation of hydrogel driving material: weigh 2g of poly-N-isopropyl acrylamide, 1g of carboxymethyl cellulose and 0.2g of carbon nanotubes, and place them in 50mL of deionized water, and continuously stir at a stirring speed of 300rpm at room temperature for 60min until a uniform mixed solution is formed. Then, the mixed solution is frozen in a-20℃ refrigerator for 2h, and then taken out and thawed at room temperature for 1h, and the freezing-thawing cycle is repeated for 3 times to prepare the hydrogel driving material;

[0092] (3) Model design: based on the CT scan data of a right lower limb amputee adult male patient, a three-dimensional model of the bionic prosthesis is designed by using SolidWorks software, which can accurately simulate the shape and size of the normal human lower limb skeleton, wherein the flexible driving unit is designed at the knee joint and ankle joint parts, and the pressure sensor and strain sensor in the sensing feedback system are arranged at the stress area of the sole and the key parts of the joint movement, respectively;

[0093] (4) 4D printing: the shape memory composite material particles are placed into the 4D printer cartridge equipped with a 0.4mm nozzle, the printing temperature is set to 180℃, the printing speed is 60mm / s, and the layer height is 0.2mm, and the bionic skeleton is printed by using the fused deposition modeling technology;

[0094] The hydrogel driving material is loaded into a syringe of a 4D printer, a direct ink writing technology is adopted, the hydrogel driving material is printed at predetermined positions of the bionic skeleton such as knee joints and ankle joints at an extrusion speed of 1 mm / s and a printing layer height of 0.5 mm, the integration of the flexible driving unit and the bionic skeleton is realized, and the bionic artificial limb is obtained;

[0095] (5) Sensing feedback system integration: install the pressure sensor and the strain sensor at the preset installation positions of the bionic artificial limb, connect the pressure sensor and the strain sensor with the signal processing module through wires respectively, and complete the integration of the sensing feedback system.

[0096] Example 2

[0097] A 4D-printed bionic artificial limb and a preparation method and application thereof, comprising:

[0098] (1) Preparation of shape memory composite material: heat the shape memory polyurethane to 130 DEG C to melt, then add chopped carbon fibers (length 5 mm, diameter 8 μm) and nano-silica (particle size about 80 nm) and mix at a speed of 1000 rpm for 40 min, and then cool to room temperature to obtain shape memory composite material particles; wherein the mass ratio of the shape memory polymer, the chopped carbon fiber and the nano-silica is 80%:12%:8%;

[0099] (2) Preparation of hydrogel driving material: weigh 3 g of poly-N-isopropyl acrylamide, 1.5 g of carboxymethyl cellulose and 0.3 g of carbon nanotubes, place them in 60 mL of deionized water, and continuously stir at a stirring speed of 350 rpm at room temperature for 70 min until a uniform mixed solution is formed. Then, the solution is frozen in a-25 DEG C refrigerator for 2.5 h, and then taken out and thawed at room temperature for 1.5 h, and the freezing-thawing cycle is repeated 4 times to obtain the hydrogel driving material;

[0100] (3) Model design: based on the MRI scanning data of a left lower limb amputee patient of a young woman, a three-dimensional model of the bionic artificial limb is designed using AutoCAD software, and the bionic skeleton should be appropriately reduced in size to match the patient's body size, wherein the flexible driving unit is designed to be provided at the hip joint, the knee joint and the ankle joint, and the sensor layout of the sensing feedback system is optimized according to the characteristics of the young people's movement;

[0101] (4) 4D printing: the shape memory composite material particles are placed into a 4D printer cartridge equipped with a 0.4 mm nozzle, the printing temperature is set to 175 DEG C, the printing speed is 55 mm / s, and the layer height is 0.15 mm, and the bionic skeleton is printed by a fused deposition modeling technology;

[0102] The hydrogel driving material is loaded into a syringe of a 4D printer, and a direct ink writing technology is adopted to print the hydrogel driving material at predetermined positions of the skeleton, such as the hip joint, the knee joint, and the ankle joint, at an extrusion speed of 0.8 mm / s and a printing layer height of 0.4 mm, so as to realize integrated forming of the flexible driving unit and the skeleton, and obtain the bionic artificial limb.

[0103] (5) Sensing feedback system integration: The pressure sensor and the strain sensor are installed at the preset installation positions of the bionic artificial limb, and the pressure sensor and the strain sensor are respectively connected with the signal processing module through wires, so as to complete the integration of the sensing feedback system.

[0104] Example 3

[0105] Example 3 is basically the same as Example 1, except that in step (1), the mass ratio of the shape memory polymer, the short carbon fiber, and the nano-silicon dioxide is 95%:3%:2%.

[0106] Example 4

[0107] Example 4 is basically the same as Example 1, except that in step (2), the mass ratio of poly N-isopropyl acrylamide 2g, carboxymethyl cellulose 1.4g, and carbon nanotube 0.6g is 50%:35%:15%.

[0108] Example 5

[0109] Example 5 is basically the same as Example 1, except that in step (2), the mass ratio of poly N-isopropyl acrylamide 3.08g, carboxymethyl cellulose 0.8g, and carbon nanotube 0.12g is 77%:20%:3%.

[0110] Comparative Example 1

[0111] Comparative Example 1 is basically the same as Example 1, except that in step (2), carboxymethyl cellulose is not added, i.e., poly N-isopropyl acrylamide 2g and carbon nanotube 0.2g are weighed and placed in 50mL deionized water, and a mixed solution is obtained after mixing.

[0112] Comparative Example 2

[0113] Comparative Example 2 is basically the same as Example 1, except that in step (2), the freeze-thaw cycle treatment is not used, but chemical cross-linking is used. Specifically, N,N-methylenebisacrylamide (0.5wt% of the mixed solution) is added to the mixed solution as a cross-linking agent, and polymerization is initiated by heating to obtain the hydrogel driving material.

[0114] Comparative Example 3

[0115] Comparative Example 3 is substantially the same as Example 1, except that in step (2), no carbon nanotubes are added, i.e., 2 g of poly N-isopropyl acrylamide and 1 g of carboxymethyl cellulose are weighed out and placed in 50 mL of deionized water, and mixed to obtain a mixed solution.

[0116] Comparative Example 4

[0117] Comparative Example 4 is substantially the same as Example 1, except that in step (1), the mass ratio of shape memory polymer, short carbon fibers and nano-silica is 96%:2%:2%.

[0118] Comparative Example 5

[0119] Comparative Example 5 is substantially the same as Example 1, except that in step (1), the mass ratio of shape memory polymer, short carbon fibers and nano-silica is 76%:12%:12%.

[0120] Comparative Example 6

[0121] Comparative Example 6 is substantially the same as Example 2, except that in step (2), the number of freeze-thaw cycles is 5.

[0122] Comparative Example 7

[0123] Comparative Example 7 is substantially the same as Example 1, except that in step (2), the freezing time is 1 h and the thawing time is 0.5 h.

[0124] Comparative Example 8

[0125] Comparative Example 8 is substantially the same as Example 1, except that in step (2), the freezing time is 3 h and the thawing time is 2 h.

[0126] Through performance testing of the 4D-printed bionic prosthesis prepared in the above-mentioned Examples 1 to 5, it is found that the 4D-printed bionic prosthesis can all generate driving force under the condition of temperature 20-35℃ and humidity 40%-70%, drive the joint movement of the bionic prosthesis, and cover the daily environmental changes; and can all support the patient to move flexibly. Specifically, for the 4D-printed bionic prosthesis of Example 1, it can withstand a pressure of 150 kg without obvious deformation in the vertical loading test of the mechanical property test, and can recover to the initial shape within 5 min when heated to 50℃ in the shape memory performance test; the driving performance test shows that when the environmental temperature increases from 20℃ to 35℃, the response time of the hydrogel driving unit is 15±1 s, and the knee joint can be driven to produce a bending angle of 15°±1° within 5 min. Taking the knee joint as an example, after 50 driving cycles, the angle attenuation is still less than 8%. For the 4D-printed bionic prosthesis of Example 2, it can withstand a pressure of 120 kg without obvious deformation in the vertical loading test of the mechanical property test, and can recover to the initial shape within 3 min when heated to 45℃ in the shape memory performance test; the driving performance test shows that when the environmental humidity increases from 40% to 70%, the response time of the hydrogel driving unit is 12±1 s, and the ankle joint can be driven to produce a rotation of 12°±1° within 4 min. Taking the ankle joint as an example, after 50 driving cycles, the angle attenuation is still less than 5%. In this way, the large-angle driving speed of the hydrogel can meet the posture mode switching of the prosthesis, and the small-angle rapid fine-tuning ability combined with the preloaded state switching can adapt to the joint dynamic adjustment requirement in the gait cycle, so that the driver can provide the instantaneous required torque through the preloaded state switching and small-range dynamic fine-tuning, assist the joint to complete the movement within the physiological time, adapt to the human daily movement rhythm, and realize the dynamic self-adaptive adjustment.

[0127] Compared with Example 1, the knee joint bending angle of the prepared bionic prosthesis in Comparative Example 1 is reduced from 15° to 8°, the tensile strength of the hydrogel driving material is reduced from 220 kPa to 160 kPa, and due to the lack of hydrogen bond enhancement of carboxymethyl cellulose, the driving is prone to fracture. Compared with Example 1, the knee joint bending angle of the prepared bionic prosthesis in Comparative Example 2 is reduced from 15° to 10°, and the response time of the hydrogel driving material is extended from 15 s to 25 s, because the chemical crosslinking network is high in rigidity, resulting in a decrease in driving deformation ability. In Comparative Example 3, the lack of carbon nanotubes leads to insufficient conductivity of the flexible driving unit, resulting in a delay of the sensing feedback signal of more than 0.3 s and poor mechanical strength.

[0128] Compared with Example 1, in Comparative Example 4, the strength and impact resistance of the bionic skeleton are significantly reduced due to the too low amount of the added reinforcing material, the bionic skeleton is difficult to bear the weight of an adult male, and the recovery time of the bionic skeleton is prolonged, and the bionic skeleton cannot be effectively coupled with the sensing feedback system. In Comparative Example 5, the extrusion resistance increases during printing due to the too high amount of the added reinforcing material, which increases the printing difficulty and limits the shape memory function, so that the joint cannot completely recover to the initial shape after multiple deformations, affecting the motion accuracy.

[0129] In Comparative Example 6, compared with Example 2, the driving response time is prolonged from 12 s to 15 s after increasing the number of freeze-thaw cycles, and the elasticity of the hydrogel driving material is reduced due to excessive crosslinking. At the same time, during 4D printing, the extrusion speed is reduced from 0.8 mm / s to 0.5 mm / s due to the increased extrusion resistance.

[0130] Comparative Examples 7 and 8, compared with Example 1, in Comparative Example 7, the tensile strength of the hydrogel driving material is reduced by 15% due to the reduction of the freezing time from 2 h to 1 h, and the residual small ice crystals further reduce the impact resistance of the hydrogel driving material due to the reduction of the thawing time to 0.5 h. In Comparative Example 8, the freezing time is extended to 3 h, which leads to excessive growth of ice crystals, puncturing the hydrogel network structure, increasing the internal porosity, reducing the compression strength of the hydrogel from 180 kPa in Example 1 to 150 kPa, and causing the structure to collapse during swelling; and the thawing time is extended to 2 h, which causes excessive relaxation, resulting in fluctuations in the crosslinking density.

[0131] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application. The part of the present application not described in detail is the known technology to those skilled in the art.

Claims

1. A 4D printed bionic prosthesis, characterized in that, Comprising: a bionic skeleton and a flexible driving unit; the flexible driving unit is located at the joint active part of the bionic skeleton, and is used for driving the movement of the bionic skeleton; the bionic prosthesis is obtained by 4D printing integrated forming, the bionic skeleton is made of shape memory composite material, and the flexible driving unit is made of hydrogel driving material; the shape memory composite material comprises shape memory polymer and reinforcing material in a mass ratio of (80%-95%):(5%-20%); the hydrogel driving material comprises a temperature-sensitive polymer matrix, a stabilizer and a functional filler in a mass ratio of (50%-80%):(20%-40%):(3%-15%).

2. The 4D printed bionic prosthesis according to claim 1, characterized in that: The shape memory polymer comprises at least one of shape memory polyethylene, shape memory polypropylene, shape memory polylactic acid, shape memory polycaprolactone, shape memory polyurethane and shape memory poly-L-lactic acid; preferably composed of shape memory polymers with two different glass transition temperatures; and / or The reinforcing material comprises at least one of carbon fiber, nano-silicon dioxide and magnetic nanoparticles; preferably, the length of the carbon fiber is 3-5mm, and the diameter is 7-10um; preferably, the particle size of the nano-silicon dioxide is 50-150nm.

3. The 4D printed bionic prosthesis according to claim 1, characterized in that: The temperature-sensitive polymer matrix comprises at least one of poly-N-isopropyl acrylamide, polyacrylic acid and polymethacrylic acid; and / or The stabilizer comprises at least one of polyethylene glycol, gelatin, polyacrylamide and carboxymethyl cellulose; The functional filler comprises at least one of carbon nanotubes, graphene, silicon dioxide and ferroferric oxide.

4. The 4D printed bionic prosthesis according to any one of claims 1-3, wherein: The hydrogel driving material comprises a temperature-sensitive polymer matrix, a stabilizer and a functional filler in a mass ratio of (60%-70%):(25%-35%):(5%-10%); Preferably, the response temperature of the flexible driving unit is 20-35℃, and the response humidity is 40%-70%.

5. A method of preparing a 4D printed bionic prosthesis as claimed in any one of claims 1 to 4, characterized in that, The preparation method comprises the following steps: (1) heating the shape memory polymer to a molten state, then adding the reinforcing material and mixing to obtain a shape memory composite material; wherein the mass ratio of the shape memory polymer and the reinforcing material is (80%-95%):(5%-20%); (2) adding a temperature-sensitive polymer matrix, a stabilizer and a functional filler in a mass ratio of (50%-80%):(20%-40%):(3%-15%) to water and mixing to obtain a mixed solution; then the mixed solution is subjected to freeze-thaw cycle treatment to obtain a hydrogel driving material; (3) the shape memory composite material is printed by 4D printing technology to obtain a bionic skeleton, and then the hydrogel driving material is printed at a predetermined position of the bionic skeleton by 4D printing technology to obtain the bionic prosthesis; wherein the predetermined position is the joint active part of the bionic skeleton, and the predetermined position of the bionic prosthesis is the flexible driving unit.

6. The preparation method according to claim 5, characterized in that, In step (2): The number of cycles of the freeze-thaw cycle treatment is 3-4 times; Preferably, the freezing time of the freeze-thaw cycle treatment is 1.5-2.5 hours, and the thawing time is 0.8-1.8 hours.

7. The preparation method according to claim 5, characterized in that, The predetermined position is the hinge side or the stretching side of the joint movement part; and / or The thickness of the flexible driving unit is 0.4-1.5 mm.

8. The production method according to any one of claims 5 to 7, characterized by, The bionic skeleton is obtained by using a fused deposition modeling technology, and the flexible driving unit is obtained by using a direct ink writing technology.

9. Use of a 4D printed bionic prosthesis according to any one of claims 1 to 4, characterized in that, Applied to the field of limb injury rehabilitation.

10. Use according to claim 9, characterized in that, A pressure sensor and a strain sensor are installed at a preset installation position of the bionic artificial limb, and the pressure sensor and the strain sensor are connected with a signal processing module, respectively; wherein the pressure sensor and the strain sensor are used for monitoring the contact pressure of the bionic artificial limb with the outside world and the deformation of the bionic artificial limb in real time, respectively, and transmitting the collected monitoring signals to the signal processing module; the signal processing module is used for analyzing the received monitoring signals, determining the driving instruction of the flexible driving unit, so that the bionic artificial limb is adjusted.