Artificial finger based on thermally-actuated artificial muscle

Abstract

The invention provides a prosthetic finger based on thermally-actuated artificial muscles. The prosthetic finger comprises a prosthetic finger skeleton, a first artificial muscle attached to the buckling side of the prosthetic finger skeleton and a second artificial muscle attached to the stretching side of the prosthetic finger skeleton. The first artificial muscle and the second artificial muscle are made of one-way actuating shape memory polyurethane; the prosthetic finger also includes a heating mechanism for actuation of the first artificial muscle and the second artificial muscle. According to specific driving and transmission parameters required by finger target actions, one-way actuating shape memory polyurethane is selected as an artificial muscle material, a block (hard segment and soft segment) network structure is constructed, and bionic matching between the one-way actuating shape memory polyurethane and finger motion variables is achieved by regulating and controlling response temperature, orientation degree, crystallinity, modulus and microcosmic driving force.

Description

Technical Field

[0001] The invention relates to the technical field of intelligent materials, and in particular to a prosthetic finger based on thermally actuated artificial muscles. Background Art

[0002] At present, clinical treatment options for upper limb disability mainly include somatosensory electrical stimulation, acupuncture, and motor rehabilitation, with the goal of preserving the patient's limb function to the greatest extent. However, for more serious conditions such as hand defects, the above clinical treatments cannot provide sufficient improvement. Intelligently driven prosthetic hands can reconstruct the patient's missing limb motor function through hand compensation, helping patients reintegrate into society.

[0003] Most prosthetic hands are based on rigid structures and rely on high-energy-density motors to achieve the necessary control accuracy, torque output, and response speed. They are complex in structure, have high manufacturing costs, and require post-production technical support and maintenance. In addition, the average weight of an adult hand is 400g, but most current prosthetic hands weigh more than this value, even up to 1,200g, due to motors and transmission mechanisms. Unlike human hands, the use of prosthetic hands places all the weight on the stump muscles rather than the bones, so it is difficult for patients to wear them for a long time and is very likely to cause discomfort and muscle fatigue.

[0004] To further improve the performance of prosthetic hands, researchers have incorporated "flexibility" elements into the production of prosthetic hands. Currently, most flexible or soft prosthetic hands rely on fluid actuators, including air pressure and hydraulic drive. Pneumatic drives mostly use superelastic materials such as silicone and use air pressure for transmission, which greatly reduces the weight of the bionic hand itself and has better softness and adaptability. For example, Zhu's team from Shanghai Jiao Tong University proposed a soft, elastic, lightweight (292g), low-cost inflatable soft prosthetic hand. Its fingers are embedded with a fiber-reinforced soft structure with multiple distributed hard structural layers, which can achieve a variety of dexterous grasping gestures under air pressure drive [Nature Biomedical Engineering, 2021: 1-10]; Tawk et al. proposed using negative pressure to activate the 3D-printed prosthetic hand through vacuum [In 2019IEEE / ASME International Conference on Advanced Intelligent Mechatronics (AIM). 2019: 50-55], generating an output force of ~27N and a maximum linear displacement of 9.85mm [IEEE / ASME Transactions on Mechatronics, 2019, 24(5): 2118-2129.]. But overall, prosthetic hands that use gas as a power source require additional cylinders / pumps, and liquid drives require the addition of a pipeline system for transportation, which not only places strict requirements on sealing, but also limits the driving speed and efficiency. The independent driving and transmission systems reduce the portability of the entire hand [Robotics, 2022, 11(4):71].

[0005] Based on the artificial muscle-bone model, De Pascali et al. from the Italian Institute of Technology designed a 3D pneumatic artificial muscle actuator GRACE made of a polymer corrugated membrane, and connected 18 GRACEs of different sizes to make a bionic hand with a wrist. According to the precise calculation of the mathematical model, the contraction and extension of fingers of different scales can be achieved, and various actions can be achieved by combining different materials and mechanical properties [Science Robotics, 2022, 7(68): eabn4155.]. However, this method of increasing the degree of freedom through an external support structure involves more assembly parts, resulting in insufficient practicality and portability. The fundamental reason is the separation of drive and transmission. Summary of the invention

[0006] In view of the problems of current prosthetic hands such as complex mechanical structure, heavy weight, and insufficient bionic movement, the present invention provides a prosthetic finger based on thermally actuated artificial muscles, which transfers mechanical control from electric drive to structural and material design. Through the combination and design of thermally actuated materials and the skeleton structure of prosthetic fingers, the "drive-transmission" fusion creation of prosthetic fingers is achieved while reproducing the bionic movement of the human hand. In addition, the purpose of structural simplification and weight reduction is achieved.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a prosthetic finger based on thermally actuated artificial muscles, comprising a prosthetic finger frame, a first artificial muscle attached to the flexion side of the prosthetic finger frame, and a second artificial muscle attached to the extension side of the prosthetic finger frame; the first artificial muscle and the second artificial muscle are made of one-way actuated shape memory polyurethane; the prosthetic finger also includes a heating mechanism for actuating the first artificial muscle and the second artificial muscle.

[0009] As a preferred embodiment, the artificial finger skeleton includes a metacarpal bone, a proximal phalanx, a middle phalanx and a distal phalanx connected in sequence; the first artificial muscle is sequentially attached to the flexion side of the metacarpal bone, the flexion side of the proximal phalanx, the flexion side of the middle phalanx and the flexion side of the distal phalanx; the second artificial muscle is attached to the extension side of the metacarpal bone; the heating mechanism is an electric heating film, including a first electric heating film attached to one end of the flexion side of the metacarpal bone close to the proximal phalanx, a second electric heating film attached to the extension side of the metacarpal bone away from the proximal phalanx, a third electric heating film and a fourth electric heating film attached to both ends of the flexion side of the proximal phalanx, a fifth electric heating film attached to the flexion side of the middle phalanx and a sixth electric heating film attached to the flexion side of the distal phalanx.

[0010] As a preferred embodiment, the soft segment of the one-way actuated shape memory polyurethane is polycaprolactone diol, and the hard segment is a condensation product of diisocyanate and 1,4-butanediol;

[0011] Preferably, the diisocyanate is diphenylmethyl diisocyanate (MDI);

[0012] Preferably, the mass of the hard segment is 35% to 45% of the mass of the one-way actuated shape memory polyurethane;

[0013] Preferably, the method for preparing the one-way actuated shape memory polyurethane comprises the following steps:

[0014] (1) prepolymerizing polycaprolactone diol and diisocyanate at 80-100° C.;

[0015] (2) adding 1,4-butanediol and continuing the reaction at 80-100°C;

[0016] Preferably, the molar ratio of the total number of hydroxyl groups in the 1,4-butanediol and the polycaprolactone diol to the isocyanate in the diisocyanate is 1:1 to 1.2;

[0017] Preferably, the molecular weight of the polycaprolactone polyol is 3000 to 5000 g / mol;

[0018] Preferably, in step (1), the reaction time of the prepolymerization is 2 to 3 hours;

[0019] Preferably, in step (2), the reaction is continued for 0.5 to 5 minutes.

[0020] In the technical solution of the present invention, the one-way actuated shape memory polyurethane has thermal responsive actuation, the thermal responsive actuation temperature is determined by the "crystallization-melting" transition temperature of the soft segment, and the thermal actuation working capacity is determined by the thermal enthalpy change of the crystal melting during the thermal actuation process.

[0021] As a preferred embodiment, the one-way actuated shape memory polyurethane used to prepare the first artificial muscle is subjected to pre-stretching strain and shape fixation;

[0022] Preferably, the pre-stretching strain is the "crystallization-melting" temperature T m The tensile strain is ≥ 100%; the shape is fixed below the "crystallization-melting" temperature T m Fixed shape.

[0023] As a preferred embodiment, the extension sides of the metacarpal bone, proximal phalanx, middle phalanx and distal phalanx are connected in sequence through an extension tendon rope; a first positioning pulley and a second positioning pulley are sequentially arranged along the inner edge of the metacarpal bone in the direction toward the proximal phalanx; one end of the extension tendon rope is staggered to bypass the first positioning pulley and the second positioning pulley and is fixed to the second artificial muscle.

[0024] As a preferred embodiment, it also includes two joint series tendon ropes symmetrically distributed on both sides of the prosthetic finger skeleton; the connections of the metacarpal bone-proximal phalanx, proximal phalanx-middle phalanx, and middle phalanx-distal phalanx are provided with a rotation center, and the two symmetrical joint series tendon ropes connect the metacarpal bone and each phalanx in sequence through the rotation center.

[0025] As a preferred embodiment, it also includes a timing control mechanism; the timing control mechanism outputs a signal to control the heating of the first artificial muscle and the second artificial muscle by the heating mechanism; in the technical solution of the present invention, by controlling the heating sequence of artificial muscles in different regions, the artificial muscles on the extension side and the flexion side of each region can be actuated in coordination, thereby driving the bionic movement of the prosthetic finger.

[0026] The above technical solution has the following advantages or beneficial effects:

[0027] According to the specific driving and transmission parameters required for the finger target action, the present invention selects a one-way actuated shape memory polyurethane as the artificial muscle material, constructs a block (hard segment and soft segment) network structure, and achieves bionic matching with the finger motion variables by regulating the response temperature, orientation, crystallinity, modulus and microscopic driving force. Among them, the thickness, length and other dimensions of the artificial muscle can be calculated based on the force or response speed required for the artificial finger movement according to the modeling.

[0028] The present invention arranges artificial muscles on the flexion side and / or extension side of the metacarpal bones and finger joints respectively to form human-like antagonistic tissues. When heated, the artificial muscles on the flexion side contract, the finger movements are fixed when cooled, and the artificial muscles on the extension side contract when heated again, driving the entire finger to extend. The artificial finger designed by the present invention can constrain and guide the artificial muscles to extend and contract for transmission, so that the two are effectively integrated and the target movement is achieved.

[0029] The present invention heats artificial muscles in different areas through a timing control mechanism to achieve motion mimicry and bionic performance of the prosthetic hand. It has high bionics and integration, compact structure, simple control, fast response speed, and can be applied to prosthetic hands for infants with smaller space and lighter weight requirements. The driving threshold is low, and the driving can be achieved with 2V, and the energy consumption is low. In addition, the purpose of simplifying the structure and reducing the weight can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention and its features, configurations and advantages will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings. The same reference numerals indicate the same parts throughout the drawings. The drawings are not drawn to scale, but rather to illustrate the subject matter of the present invention.

[0031] Figure 1 It is a schematic diagram of the overall structure of the artificial finger based on thermally actuated artificial muscle in Example 2 of the present invention.

[0032] Figure 2 It is a full cross-sectional schematic diagram of the artificial finger based on thermally actuated artificial muscle in Example 2 of the present invention.

[0033] Figure 3 3 is a graph showing the tensile stress-strain test results of the one-way shape memory polyurethane with different hard segment contents in Example 1 of the present invention.

[0034] Figure 4 It is a performance test diagram of the unidirectional shape memory polyurethane before and after stretching in Example 1 of the present invention.

[0035] Figure 5 This is a diagram representing the contraction and actuation capability of the artificial muscle in Example 1 of the present invention.

[0036] Figure 6This is an infrared image of the fake finger in the actuation process in Example 2 of the present invention. DETAILED DESCRIPTION

[0037] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. It is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but only represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0038] In the description of the present invention, it should be noted that if the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The following embodiments are only some embodiments of the present invention, rather than all embodiments. Therefore, the detailed description in the embodiments of the present invention provided below is not intended to limit the scope of the present invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0041] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0042] Example 1 Synthetic artificial muscle:

[0043] In this embodiment, a one-way actuated shape memory polyurethane (T m-SMPU) is used as the material for synthesizing artificial muscles. The synthetic raw materials and amounts are shown in Tables 1 and 2.

[0044] Table 1

[0045]

[0046] Taking S2 as an example, the specific synthesis steps are as follows: weigh PCL, MDI, and BDO and heat them in a vacuum oven at 105°C for 2h to dry the moisture; take 30g PCL and 17.5g MDI and add them into a three-necked flask, carry out prepolymerization reaction in an oil bath at 85°C, stir with a stirring rod for 2h (speed is 260rpm), and remove bubbles in vacuum at the same time; add 5.85g BDO dropwise and react for 2min, and the product is T m -SMPU; the product was poured onto a polytetrafluoroethylene plate and dried in an oven at 85°C for 16 hours; 4 g of the dried sample was dissolved in 33.4 g of N,N-dimethylformamide (DMF) and stirred magnetically at 65°C for 2 hours; the sample was poured into a polytetrafluoroethylene mold and then formed into a film in an oven at 80°C for 8 hours to remove the solvent, thereby obtaining a one-way actuated shape memory polyurethane (T m -SMPU) artificial muscle film sample (thickness 0.12mm, "crystallization-melting" temperature T m The range is 38~50℃).

[0047] Table 2

[0048] Hard segment content PCL-diol(g) MDI(g) BDO(g) S1 35wt% 30 11.54 4.61 S2 40wt% 30 14.37 5.63 S3 45wt% 30 17.68 6.82

[0049] In Table 2, hard segment content = (m MDI +m BDO ) / (m MDI +m BDO +m PCL-diol ).

[0050] The T synthesized in this example m -The tensile stress-strain results of SMPU are shown in Figure 3 As can be seen from the figure, the tensile elongation at break of the artificial muscle film sample with a hard segment content of 40wt% is the highest, which is 1126%, and the elastic modulus is 2.33MPa. This is because the cross-linking degree of the system is optimal under this ratio. Therefore, the subsequent experiments were carried out with the sample with a hard segment content of 40wt% in S2.

[0051] Sample S2 was stretched at 50°C to a strain of 100% and then fixed at 15°C. The 2D-XRD test results before and after stretching are shown in Figure 4 From the figure, we can see the changes in the crystallinity and orientation of the sample before and after stretching, which can reflect the microstructural evolution caused by external force. Figure 4 a is the 2D-XRD pattern before stretching, Figure 4 b is the 2D-XRD pattern after stretching. Figure 4 c is the equatorial integral before stretching, Figure 4 d is the integral in the equatorial direction after stretching. Figure 4 It can be seen that the sample crystal surface before stretching presents a uniform diffraction ring pattern ( Figure 4 a), after stretching, the 2D diffraction signal is concentrated and enhanced in the equatorial direction, proving that the strain-induced crystal morphology has changed ( Figure 4 b); From the integration results of the two-dimensional diffraction signal, it can be seen that the integral in the equatorial direction before stretching ( Figure 4 c) After stretching, the overall crystallinity is significantly improved; by integrating the azimuth angle of the (110) crystal plane, we can get ( Figure 4 d), the crystals are oriented in the stretching direction. m -During the stretching process of SMPU, the oriented crystals will undergo a melt phase transition, releasing the mechanical energy stored in the stretching process, thereby doing work and generating thermal actuation.

[0052] Sample S2 was cut into a film sample with a length of 7 cm, a width of 6 mm, and a thickness of 0.12 mm. It was stretched at 50°C and fixed at 15°C. The length after fixing was 13.5 cm. After thermal stimulation (i.e., the temperature was higher than T m ) can lift heavy objects by contracting. Figure 5 As shown in the figure, the S2 film sample (mass 0.065 g) can lift an object (mass 50.0 g) weighing 810 times its own weight by about 6 cm within 4 seconds after being heated to a temperature higher than 50 °C, indicating that the material has excellent work and driving capabilities, with a work density of 461 J kg -1 , power density is 115Wkg -1 .

[0053] Example 2 Prosthetic finger based on thermally activated artificial muscle

[0054] In this example, the S2 sample in Example 1 was used as the artificial muscle material to prepare a prosthetic finger. Figure 1-2 As shown, the details are as follows:

[0055] The prosthetic finger based on thermally actuated artificial muscles in this embodiment includes a prosthetic finger skeleton, a first artificial muscle 01 attached to the flexion side of the prosthetic finger skeleton, and a second artificial muscle 02 attached to the extension side of the prosthetic finger skeleton; the first artificial muscle and the second artificial muscle are made of the S2 sample in Example 1; the prosthetic finger also includes a heating mechanism for actuating the first artificial muscle and the second artificial muscle.

[0056] Furthermore, the artificial finger skeleton includes a metacarpal bone 10, a proximal phalanx 20, a middle phalanx 30 and a distal phalanx 40 connected in sequence; the first artificial muscle 01 passes through and is attached to the flexion side of the metacarpal bone 10, the flexion side of the proximal phalanx 20, the flexion side of the middle phalanx 30 and the flexion side of the distal phalanx 40 in sequence; the second artificial muscle 02 is attached to the extension side of the metacarpal bone 10; the heating mechanism is an electric heating film, including a first electric heating film 11 attached to the flexion side of the metacarpal bone close to one end of the proximal phalanx, a second electric heating film 12 attached to the extension side of the metacarpal bone away from one end of the proximal phalanx, a third electric heating film 21 and a fourth electric heating film 22 attached to both ends of the flexion side of the proximal phalanx, a fifth electric heating film 31 attached to the flexion side of the middle phalanx and a sixth electric heating film 41 attached to the flexion side of the distal phalanx.

[0057] Furthermore, the one-way actuated shape memory polyurethane used to prepare the first artificial muscle 01 is stretched to 100% at 50°C and fixed in shape at 15°C. In this embodiment, the first artificial muscle on the flexion side is pre-stretched and shape-fixed, while the second artificial muscle 02 is not pre-stretched and shape-fixed. This ensures that during the bending actuation of the prosthetic finger, the second artificial muscle 02 can be stretched and strained and fully flexed.

[0058] Furthermore, the extension sides of the metacarpal bone 10, the proximal phalanx 20, the middle phalanx 30 and the distal phalanx 40 are connected in sequence through the extension tendon rope 03; the first positioning pulley 13 and the second positioning pulley 14 are arranged in sequence along the inner edge of the metacarpal bone in the direction toward the proximal phalanx 20; one end of the extension tendon rope 03 is staggered to bypass the first positioning pulley 13 and the second positioning pulley 14, and is fixed to the second artificial muscle 02.

[0059] Furthermore, the artificial finger also includes two joint series tendon ropes 04 symmetrically distributed on both sides of the artificial finger skeleton; a rotation center is provided at the connection between the metacarpal bone 10-proximal phalanx 20, the proximal phalanx 20-middle phalanx 30, and the middle phalanx 30-distal phalanx 40, and the two symmetrical joint series tendon ropes 04 connect the metacarpal bone 10 and each phalanx in sequence through the rotation center.

[0060] Furthermore, the artificial finger also includes a timing control mechanism; the timing control mechanism outputs a signal to control the heating mechanism to heat the first artificial muscle 01 and the second artificial muscle 02.

[0061] The actuation process of the fake finger in this embodiment is as follows:

[0062] When the artificial finger needs to be flexed, the timing control mechanism outputs a signal to heat the first electric heating film 11 and the second electric heating film 12 in the metacarpal bone 10, the third electric heating film 21 and the fourth electric heating film 22 in the proximal phalanx 20, the fifth electric heating film 31 in the middle phalanx 30, and the sixth electric heating film 41 in the distal phalanx 40 according to the grasping requirements. In order to achieve bionic flexion movement, the temperature of the electric heating film on the flexion side needs to be controlled to be higher than the temperature of the electric heating film on the extension side. For example, the first electric heating film 11, the third electric heating film 21, and the fourth electric heating film 22 on the flexion side are heated. 22. The fifth and sixth electric heating films 31 and 41 are heated to increase the temperature. The first artificial muscle 01 on the flexion side begins to contract under the thermal stimulation of more than 38°C, and is thermally contracted during the process of continuous heating to 50°C. At the same time, the second electric heating film 12 on the extension side is kept to rise in temperature slower than the electric heating film on the flexion side. During the process of the temperature rising to 45°C, the soft segment crystals of the second artificial muscle 02 on the extension side melt and, along with the flexion movement of the first artificial muscle 01, exhibit thermal passive stretching actuation. In the above process, the first artificial muscle 01 actuated by thermal contraction pulls each finger joint to start flexing around its own rotation center, and each joint flexes at the same angular velocity to achieve bionic motion. In addition, the flexion will transmit force to the second artificial muscle 02 on the extension side through the extension tendon rope 03, that is, the second artificial muscle 02 will be passively stretched and lengthened to fill the amount of stroke contracted by the flexion of the first artificial muscle 01. The artificial finger in this embodiment can also finely control the flexion of each joint at different angular velocities by adjusting the heating rate or heating sequence of the electric heating film on the flexed side to adapt to the grasping of objects of different shapes.

[0063] When the artificial finger in the thermally actuated flexed state needs to be extended, the timing control mechanism outputs a signal to heat the second electric heating film 12 (in the flexed state, the second artificial muscle 02 is in a passive stretching state) to raise its temperature to 50°C, and the second artificial muscle 02 is thermally contracted under thermal stimulation; at the same time, the timing control mechanism outputs a signal to stop heating the first electric heating film 11, the third electric heating film 21, the fourth electric heating film 22, the fifth electric heating film 31 and the sixth electric heating film 41 on the flexed side to reduce their temperatures, and the first artificial muscle 01 on the flexed side is thermally passively stretched during the temperature drop from 50°C to 38°C as the second artificial muscle 02 contracts. That is, while the second artificial muscle 02 is thermally contracted, it pulls the stretching tendon 03 to make each finger joint rotate in the opposite direction around its own rotation center, which is a stretching movement; and the first artificial muscle 01 on the flexed side will be stretched and lengthened by these finger joints until the artificial finger is restored to a fully extended state.

[0064] The artificial muscle and the artificial finger in this embodiment are weighed separately. The total weight of the first artificial muscle and the second artificial muscle of a single artificial finger is less than 0.1g, and the weight of a single artificial finger is only 6g. Figure 6As shown, the electric heating film in this embodiment can meet the 38°C thermal stimulation when driven by a 2V voltage, thereby realizing the bending actuation of the artificial finger.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A prosthetic finger based on thermally actuated artificial muscle, characterized in that: The artificial finger comprises a prosthetic finger frame, a first artificial muscle attached to the flexion side of the prosthetic finger frame, and a second artificial muscle attached to the extension side of the prosthetic finger frame; the first artificial muscle and the second artificial muscle are made of one-way actuated shape memory polyurethane; the prosthetic finger also comprises a heating mechanism for actuating the first artificial muscle and the second artificial muscle.

2. The artificial finger according to claim 1, characterized in that: The artificial finger skeleton includes a metacarpal bone, a proximal phalanx, a middle phalanx and a distal phalanx connected in sequence; the first artificial muscle sequentially penetrates and is attached to the flexion side of the metacarpal bone, the flexion side of the proximal phalanx, the flexion side of the middle phalanx and the flexion side of the distal phalanx; the second artificial muscle is attached to the extension side of the metacarpal bone; the heating mechanism is an electric heating film, including a first electric heating film attached to one end of the flexion side of the metacarpal bone close to the proximal phalanx, a second electric heating film attached to the extension side of the metacarpal bone away from the proximal phalanx, a third electric heating film and a fourth electric heating film attached to both ends of the flexion side of the proximal phalanx, a fifth electric heating film attached to the flexion side of the middle phalanx and a sixth electric heating film attached to the flexion side of the distal phalanx.

3. The artificial finger according to claim 1, characterized in that: The soft segment of the one-way actuated shape memory polyurethane is polycaprolactone diol, and the hard segment is a condensation product of diisocyanate and 1,4-butanediol.

4. The artificial finger according to claim 3, characterized in that: The diisocyanate is diphenylmethyl diisocyanate.

5. The artificial finger according to claim 3, characterized in that: The mass of the hard segment is 35% to 45% of the mass of the one-way actuated shape memory polyurethane.

6. The artificial finger according to claim 3, characterized in that: The preparation method of the one-way actuated shape memory polyurethane comprises the following steps: (1) prepolymerizing polycaprolactone diol and diisocyanate at 80-100° C.; (2) After adding 1,4-butanediol, continue the reaction at 80-100°C.

7. The artificial finger according to claim 1, characterized in that: The one-way actuated shape memory polyurethane used to prepare the first artificial muscle is subjected to pre-stretching strain and shape fixation.

8. The artificial finger according to claim 2, characterized in that: The extension sides of the metacarpal bone, proximal phalanx, middle phalanx and distal phalanx are connected in sequence through an extension tendon rope; a first positioning pulley and a second positioning pulley are sequentially arranged along the inner edge of the metacarpal bone in the direction toward the proximal phalanx; one end of the extension tendon rope is staggered and bypasses the first positioning pulley and the second positioning pulley, and is fixed to the second artificial muscle.

9. The artificial finger according to claim 2, characterized in that: It also includes two joint series tendon ropes symmetrically distributed on both sides of the artificial finger skeleton; the connections of the metacarpal bone-proximal phalanx, proximal phalanx-middle phalanx, and middle phalanx-distal phalanx are provided with a rotation center, and the two symmetrical joint series tendon ropes are connected to the metacarpal bone and each phalanx in sequence through the rotation center.

10. The artificial finger according to claim 1, characterized in that: It also includes a timing control mechanism; the timing control mechanism outputs a signal to control the heating mechanism to heat the first artificial muscle and the second artificial muscle.

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