A bionic ligament with programmable nonlinear mechanical behavior

Abstract

The application discloses a kind of bionic ligament with programmable nonlinear mechanical behavior, belong to medical prosthesis technical field;The application is formed by the double knot array of different directions, single number is the double knot of a structure, double number is the double knot of another structure, and the construction of ligament continuous structure is realized by periodic alternative knot arrangement;The application introduces clear topological rules and adjustable geometric weaving parameters in the weaving structure, so that the overall morphology and mechanical properties of artificial ligament can be programmable controlled under the condition of keeping the material unchanged;By changing the node direction sequence, the number of horizontal and vertical rope knots, the weaving length and the number of weaving lines, multiple mechanical gears from flexible to high stiffness can be obtained, so that artificial ligament can adapt to the biomechanical requirements of different joint systems such as knee joint and lumbar vertebra.

Description

Technical Field

[0001] This invention relates to the field of medical prosthesis technology, and in particular to a bionic ligament with programmable nonlinear mechanical behavior. Background Technology

[0002] Ligaments are important soft tissues in the human musculoskeletal system. By connecting bone segments and maintaining the stable range of motion of joints, they enable coordinated and orderly movement control. Natural ligaments consist of a multi-layered structure, including collagen fibers, fiber bundles, and wavy hierarchical arrangements. These structures collectively enable ligaments to exhibit a compliant, low-stiffness response during the initial stress phase, gradually transitioning to higher stiffness under further stretching, thereby maintaining the fine control of the joint. Ligaments in different joints exhibit significant differences in length, cross-sectional morphology, fiber orientation, and nonlinear mechanical characteristics, indicating that the biological function of ligaments is highly dependent on the close coupling between their specific morphological structure and mechanical behavior.

[0003] Clinically, functional damage to ligaments caused by trauma, degeneration, or surgical removal is difficult to recover naturally, thus increasing the demand for artificial ligament replacements. Existing artificial ligaments mostly utilize polymer fiber bundles or composite material strip structures, with strength and fatigue resistance enhanced through weaving or composite reinforcement. However, such designs often rely primarily on the inherent properties of the materials themselves, lacking the ability to reproduce the nonlinear mechanical behavior of natural ligaments, structure-dominated deformation modes, and joint coordinated movements. When faced with multi-joint environments with significantly different mechanical requirements, such as the knee and lumbar spine, the adaptability of these artificial ligaments remains limited. Furthermore, existing weaving processes typically lack a design method that maps target mechanical properties back to specific weaving structure parameters, making it difficult to tailor the weaving structure to the specific mechanical response requirements of different joints. This results in a lack of effective design coupling between the morphology and mechanical properties of artificial ligaments.

[0004] With the development of joint prostheses, personalized reconstruction, and bionic robotics, adjustable connection structures that can adapt to different motion scenarios are becoming increasingly important. Existing artificial ligaments struggle to achieve multiple levels of mechanical behavior through structural design on a single material basis, and their morphology and function cannot be adjusted through geometric design. Therefore, there is an urgent need for an artificial ligament system based on structural coding, which, through programmable knot topology and adjustable geometric parameters, enables programmable morphology and mechanical properties of the artificial ligament, allowing it to exhibit nonlinear mechanical behavior matching that of physiological ligaments in different joint environments.

[0005] The term "programmable" does not refer to adjustment through external control or electronic programs, but rather to the pre-design of the node topology sequence and geometric parameters in the braided structure. This allows the braided structure of the biomimetic ligament to be realized through various processes, including but not limited to hand weaving, mechanical weaving, knitting equipment weaving, or other forming processes that can achieve the interlacing configuration of yarns. All of these weaving processes can achieve controllable construction of the node direction and arrangement sequence. Different fabrication processes can complete the construction of the braided structure according to the preset node topology sequence and morphological parameters, thereby ensuring that the structural encoding can be effectively realized and converted into corresponding mechanical properties. The pre-set control of the morphology and mechanical properties of the artificial ligament is achieved within the material system, enabling it to exhibit nonlinear mechanical behavior matching that of physiological ligaments in different joint environments. The following two articles both elaborate and analyze the theory of "programmability."

[0006] 1.Programming mechanics in knitted materials, stitch by stitch.Nature Communications.2024.

[0007] 2.Programmable helix-tubular composites with bio-inspired architecture.Materials&Design.2025. Summary of the Invention

[0008] The purpose of this invention is to address the problems of existing artificial ligaments mentioned in the background art, and to provide a bionic ligament with programmable nonlinear mechanical behavior. By introducing explicit topological rules and adjustable geometric weaving parameters into the weaving structure, the overall shape and mechanical properties of the bionic ligament can be programmably controlled while keeping the material constant. By changing the knot direction sequence, the number of horizontal and vertical knots, the weaving length, and the number of weaving threads, multiple mechanical levels from compliant to high stiffness can be obtained, enabling the bionic ligament to adapt to the biomechanical needs of different joint systems such as the knee joint and lumbar spine.

[0009] A biomimetic ligament with programmable nonlinear mechanical behavior is composed of an alternating array of double knots in different directions. Odd-numbered rows form one type of double knot structure, while even-numbered rows form another type. The continuous ligament structure is constructed through the periodic alternation of knots. Each double knot consists of two basic half knots. The biomimetic ligament is woven from an axis and winding threads. Each crossing of the winding threads around the axis forms a basic half knot. The winding direction of the axis and winding threads changes due to the change of knots, thereby forming different mechanical properties. Each basic half-knot is characterized by two parameters: the winding position and the winding direction relative to the holding reference. The winding position includes the left and right sides of the holding axis, and the winding direction includes forward winding and backward winding around the holding axis. This forms four basic patterns: left front LF half-knot, left back LB half-knot, right front RF half-knot, and right back RB half-knot. These four half-knots form the basic unit of directional controllable weaving (Left is abbreviated as L, Right as R, Front as F, and Back as B).

[0010] Using the axis as the thread-holding pivot, with the weaver facing the axis, the weaver's left side is called Left L, the weaver's right side is called Right R, the side of the axis the weaver faces is called Front F, and the side opposite to Front is called Back B. The four basic half-knot wrapping methods are as follows: Left front LF half knot, the knot is made by wrapping the thread from the left side of the spool L to the front F and passing it over the axis; Left back LB half knot, the knot is made by wrapping the thread from the left side L of the spool to the back B of the spool and tying it around the axis; Right front RF half knot, the knot is made by wrapping the thread from the right side of the bobbin R forward F around the axis; The right rear RB half knot is a knot made by wrapping the thread from the right side R of the bobbin to the rear B around the axis.

[0011] The double knot formed by the continuous weaving of the two basic half knots is the smallest functional unit. According to the winding position and winding direction, it can be arbitrarily combined with two of the four basic half knot patterns to form eight smallest functional units, namely, left front left front LFLF double knot, right front right front RFRF double knot, left front left back LFLB double knot, right front right back RFRB double knot, left front right back LFRB double knot, right front left back RFLB double knot, left front right front LFRF double knot, and right front left front RFLF double knot.

[0012] The bionic ligament uses the smallest unit knot as a code, based on the eight smallest functional units: Alternatively, it can be constructed using a double node with left-front-left-front-LFLF for odd-numbered rows and a double node with left-front-left-front-LFLF for even-numbered rows; Alternatively, a double node with left-front-left-front-LFLF for odd-numbered rows and a double node with right-front-right-front-RFRF for even-numbered rows can be used. Alternatively, a double node with left-front-left-front-LFLF for odd-numbered rows and a double node with left-front-right-back-LFRB for even-numbered rows can be used. Alternatively, a double node with left-front-left-front-LFLF for odd-numbered rows and a double node with right-front-left-back-RFLB for even-numbered rows can be used. Alternatively, it can be constructed using a left-front-left-back LFLB double node for odd-numbered rows and a left-front-left-back LFLB double node for even-numbered rows; Alternatively, it can be constructed using a double LFLB structure with nodes in the odd-numbered rows as left-front-left-back and nodes in the even-numbered rows as right-front-right-back RFRB. Alternatively, it can be constructed using a left-front-left-back LFLB double node for odd-numbered rows and a left-front-right-front LFRF double node for even-numbered rows; Alternatively, it can be constructed using a double-structured LFLB structure with nodes in the odd-numbered rows being left-front-left-back and nodes in the even-numbered rows being right-front-left-front-RFLF.

[0013] The shaft and winding are made of high-modulus polyethylene fiber or polyethylene terephthalate fiber.

[0014] By changing the arrangement sequence of the double knots, different braided topologies can be formed, thereby altering the mechanical response characteristics of the biomimetic ligament during the stretching process.

[0015] Based on the aforementioned woven topology, the overall morphology of the bionic ligament can be controlled through morphological parameters, including weave length, number of weave threads, and weave structure. By adjusting these morphological parameters, the overall morphological dimensions of the bionic ligament can be altered, allowing bionic ligaments with the same woven topology to exhibit different mechanical properties under different morphological conditions.

[0016] By structurally encoding the basic half-knot and combining the arrangement of double knots with the control of morphological parameters, a variety of different braiding topologies can be formed, thereby realizing the programmable design of biomimetic ligament morphology and mechanical properties.

[0017] like Figure 14 As shown, the physical forms of the eight weaving structures are similar to... Figure 3 The braided structure is shown in the diagram. Figure 1 One-to-one correspondence. Each biomimetic ligament is formed by the alternating winding of the axis and the winding to create a nodal structure. Different colored braided threads are used to identify the axis and the winding respectively, so as to intuitively reflect the changes in their relative positions and paths under different nodal topological conditions.

[0018] During the initial weaving process, in each horizontal weaving row, the winding thread and the axis are located on predetermined sides (e.g., the winding thread is on one side and the axis is on the other side), and their spatial positions are alternated by changing the direction of the knots during subsequent weaving. Different winding methods and interlacing paths cause the axis and winding thread to form differentiated structural orientations in three-dimensional space, thereby constructing different weaving topologies.

[0019] Because different topologies differ in node constraint forms, wire crossing methods, and force transmission paths, the geometric unfolding behavior and force evolution process of braided structures vary during tension, resulting in different mechanical response characteristics in each biomimetic ligament. Therefore, by designing the node direction sequence and braiding method, the corresponding construction of target mechanical properties can be achieved, providing a foundation for designing biomimetic ligament structures based on performance requirements. The stable correspondence between the aforementioned structural changes and mechanical responses allows different mechanical properties to be predetermined through braided structure design, thus demonstrating the programmability of the mechanical behavior of biomimetic ligaments.

[0020] The working process and working principle of this invention: This invention achieves programmable adjustment of the mechanical properties of biomimetic ligaments through the coordinated design of braided topology and morphological parameters. The braided structure uses basic half-knots as structural coding units, and double-knot structures formed by different combinations of half-knots serve as coding units. Furthermore, different braided topologies are formed by arranging these double knots axially. Simultaneously, by adjusting morphological parameters such as braid length, number of braided threads, and structural width, the overall morphology and mechanical behavior of the biomimetic ligament can be systematically controlled while maintaining the material system unchanged.

[0021] In this structural system, the braided topology primarily determines the force transmission path of the biomimetic ligament during tension. Differences in the winding radius, rotation angle, and wire crossing methods among different types of nodes create varying degrees of geometric constraints within the structure, thus altering the unfolding sequence of the braided wires under stress. When the node structure is strongly constrained, some braided wires require a longer geometric unfolding process during the initial loading stage, resulting in a longer compliant deformation zone in the early stages of tension. Conversely, when the node structure is weakly constrained, the braided wires can enter a cooperative stress-bearing state earlier, leading to an earlier increase in the overall stiffness of the structure.

[0022] The arrangement of nodes in the axial direction also affects the force transmission mechanism inside the structure. When nodes of the same type are arranged continuously, a certain degree of torsional accumulation is easily formed in the structure, making the transition from the nonlinear stage to the linear stage of the bionic ligament during the stretching process more concentrated. When nodes in different directions are arranged alternately, local torques can cancel each other out inside the structure, making the overall mechanical response smoother, thus forming a deformation process similar to the gradual unfolding of fibers in natural ligaments.

[0023] Furthermore, the braided topology alters the path complexity of the braided threads in three-dimensional space. As the number of node intersections increases or the winding angle widens, more geometrically redundant paths form within the structure. This requires the braided threads to undergo a longer geometric rearrangement process before entering the main stress phase, resulting in a more compliant mechanical response in the initial tensile stage. As the tensile displacement gradually increases, these redundant paths gradually disappear, and the braided threads gradually enter a stable stress state, leading to a gradual increase in the overall stiffness of the structure.

[0024] Based on the determined braided topology, morphological parameters primarily regulate the overall mechanical properties of the biomimetic ligament. By changing the braid length and the number of braided threads, the range of the initial nonlinear region of the structure can be adjusted, allowing the biomimetic ligament to exhibit toe regions of different lengths and adjusting the overall stiffness of the structure in the later linear phase, achieving a continuous change from low stiffness to high stiffness. By changing the braided structure of ligaments of the same length and number of threads, the overall stress distribution can be further adjusted, allowing different topologies to exhibit differentiated mechanical responses under different morphological conditions.

[0025] Under the synergistic effect of the aforementioned braided topology and morphological parameters, the biomimetic ligament prepared by this invention can stably exhibit a J-shaped force-displacement response curve similar to that of a natural ligament during stretching. This curve includes a distinct initial nonlinear deformation region followed by a region of approximately linear stiffness enhancement. By adjusting different combinations of topological sequences and morphological parameters, various mechanical response modes can be obtained, allowing the structure to gradually transition from a compliant response to a high-stiffness state.

[0026] Therefore, by structurally encoding the basic half-knot and combining the design of the braided topology with the control of morphological parameters, this invention realizes the programmable design of the mechanical properties of the bionic ligament in a single material system. This allows the bionic ligament to be structurally configured according to the mechanical requirements of different joint systems, thereby meeting the biomechanical application requirements of various joint environments such as the knee joint and lumbar spine.

[0027] The beneficial effects of this invention are: 1. This invention changes the force transmission path and geometric unfolding process of the braided thread during the stretching process by adjusting the winding method, number of intersections and arrangement sequence of the nodes in the braided topology. This allows the biomimetic ligament to exhibit a J-shaped force-displacement curve similar to that of a natural ligament during the stress process, including a significant initial nonlinear deformation zone and a subsequent stiffness enhancement zone, thereby better simulating the mechanical behavior of a natural ligament.

[0028] 2. This invention uses basic half-knots as structural coding units and forms a woven topology through different combinations of double knots, enabling the mechanical behavior of the biomimetic ligament to be adjusted through the node topology sequence. While keeping the material system constant, different mechanical response modes can be achieved simply by changing the node arrangement, thus realizing programmable design of the biomimetic ligament stiffness.

[0029] 3. Based on the braided topology, this invention can achieve coordinated adjustment of the overall shape and mechanical properties of the bionic ligament by adjusting morphological parameters such as braiding length, number of braiding threads, and structural width. This allows the bionic ligament made of the same material system to adapt to the mechanical requirements of different joint systems, thus exhibiting good adaptability in application scenarios such as ligament implantation, joint prosthesis systems, and bionic robot connection structures. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the basic half knot of the programmable bionic ligament in this invention, wherein 11 is the left anterior LF half knot, 12 is the left posterior LB half knot, 13 is the right anterior RF half knot, and 14 is the right posterior RB half knot; Figure 2 This is a schematic diagram of the smallest functional unit of the programmable bionic ligament in this invention, wherein 21 is a left anterior left anterior LFLF double knot, 22 is a right anterior right anterior RFRF double knot, 23 is a left anterior left posterior LFLB double knot, 24 is a right anterior right posterior RFRB double knot, 25 is a left anterior right posterior LFRB double knot, 26 is a right anterior left posterior RFLB double knot, 27 is a left anterior right anterior LFRF double knot, and 28 is a right anterior left anterior RFLF double knot; Figure 3 This is a schematic diagram of eight weaving structures of the programmable bionic ligament in this invention, where 31 is an LFLF-LFLF structure bionic ligament, 32 is an LFLF-RFRF structure bionic ligament, 33 is an LFLF-LFRB structure bionic ligament, 34 is an LFLF-RFLB structure bionic ligament, 35 is an LFLB-LFLB structure bionic ligament, 36 is an LFLB-RFRB structure bionic ligament, 37 is an LFLB-LFRF structure bionic ligament, and 38 is an LFLB-RFLF structure bionic ligament. Figure 4 This is a comparison curve of the stiffness of different weaving structures of the programmable bionic ligament in this invention; Figure 5 This is a curve comparing the stiffness of different weaving lengths of the programmable bionic ligament in this invention. Figure 6 This is a comparison curve of the stiffness of the programmable bionic ligament with different weaving widths in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the application of the programmable bionic ligament in the lumbar joint in Embodiment 2 of the present invention; Figure 8 This is a comparison diagram of the stretching test results of ligament specimens of different lengths in Experiment 1 of this invention; Figure 9 This is a comparison diagram of the tensile test results of ligament patterns with different numbers of threads in Experiment 2 of this invention; Figure 10 This is a comparison chart of the experimental results of the nonlinear region length of programmable bionic ligaments of different lengths in Experiment 3 of this invention; Figure 11 This is a comparison chart of the experimental results of the nonlinear region length of the programmable bionic ligament with different numbers of lines in Experiment 4 of this invention; Figure 12 This is a comparison diagram of the experimental results of linear region stiffness of programmable bionic ligaments of different lengths in Experiment 5 of this invention. Figure 13 This is a comparison diagram of the experimental results of linear region stiffness of programmable bionic ligaments with different numbers of lines in Experiment 6 of this invention. Figure 14 In this invention Figure 3 The images shown correspond to the eight weaving structures, with Figure (a) being an example. Figure 3 Figure 31 shows a physical image of the LFLF-LFLF biomimetic ligament structure, and Figure (b) shows... Figure 3 Figure 32 shows a physical image of the LFLF-RFRF biomimetic ligament structure. Figure (c) is... Figure 3 Figure 33 shows a physical image of the LFLF-LFRB biomimetic ligament structure, and Figure (d) is... Figure 3 Figure 34 shows a physical image of the LFLF-RFLB biomimetic ligament structure, and Figure (e) is... Figure 3 Figure 35 shows a physical image of the LFLB-LFLB biomimetic ligament structure, and Figure (f) is... Figure 3 Figure 36 shows a physical image of the LFLB-RFRB biomimetic ligament structure. Figure (g) is... Figure 3 Figure 37 shows a physical image of the LFLB-LFRF biomimetic ligament structure. Figure (h) is... Figure 3 Image of the biomimetic ligament structure LFLB-RFLF shown in Figure 38; Figure 15 This is a comparison diagram of the biomimetic ligament morphology under different weaving parameters and topological structures in Experiment 7 of this invention; Figure 16 This is a curve comparing the performance of the biomimetic ligament and the biological ligament in Embodiment 1 of the present invention. Detailed Implementation

[0031] Please see Figures 1 to 6 As shown, this is Example 1 of the present invention, the preparation of a bionic ligament.

[0032] First, morphological and mechanical property tests are performed on the target biological ligaments (including intertransverse ligaments and interspinous ligaments) to obtain target parameters such as their length, width, and force-displacement curves during the stretching process.

[0033] Based on the acquired target parameters, the biomimetic ligament braiding structure is reverse-engineered according to the structural coding design method proposed in this invention. First, the force-displacement curve of the target ligament is feature-extracted, dividing it into an initial nonlinear deformation zone and a subsequent stiffness-enhancing stage. Key mechanical characteristic parameters, such as the corresponding deformation range and stiffness change trend, are obtained. Based on this, a corresponding node topology sequence is selected according to the target mechanical response characteristics. When the target ligament exhibits a long compliant deformation zone in the initial stretching stage, a topology with more complex node intersection paths and stronger geometric constraints is selected to prolong the geometric unfolding process of the braided lines. When the target ligament shows stiffness enhancement in a smaller deformation stage, a topology with weaker node constraints and earlier entry of the braided lines into a cooperative stress state is selected, thereby achieving matching of the mechanical response stage characteristics. After determining the node topology sequence, the overall mechanical response is further adjusted through morphological parameters, including braiding length, braiding width, and the number of braided lines. By adjusting the weaving length to control the range of the initial nonlinear deformation zone, adjusting the number of weaving threads to regulate the overall stiffness of the later linear stage, and adjusting the weaving width to optimize the stress distribution of the structure, the overall shape and amplitude of the force-displacement curve are matched. Through the combined design of the above-mentioned nodal topology sequence and morphological parameters, the correspondence between the target mechanical properties and the weaving structure parameters is established, and the structural design scheme of the biomimetic ligament is determined accordingly. Subsequently, the biomimetic ligament is woven and fabricated according to the stated structural parameters.

[0034] This embodiment uses the LFLF-RFRF structure biomimetic ligament 32 as an example to introduce the preparation method of the biomimetic ligament. The main body of the ligament is made of high-strength flexible wire as the braiding material, preferably high-modulus polyethylene fiber. The diameter and strength of each wire are predetermined according to the target tensile strength of the joint.

[0035] In this embodiment, ten threads are used as a group of braided threads, forming a knot array along the ligament axis with alternating rows of five and four knots. In the first row, every two threads form a group of braided threads, where the left thread of each group is the wrapping thread and the right thread is the axis. The left wrapping thread circles the axis from the front, extending to the left of the axis and pressing down on the wrapping thread to form a single-loop half-knot. It then circles the axis again from the front, extending to the left of the axis and pressing down on the wrapping thread again to form the lower half-knot. These two half-knots form the first complete double knot (LFLF), with the wrapping thread still on the left side of the axis. Each group of braided threads completes two half-knots, resulting in five double knots from ten groups. Figure 3As shown in Figure 32, all ten lines in the first row of the LFLF-RFRF biomimetic ligament 32 participate in forming five left anterior left anterior LFLF double knots. The first knot 321 in the first row connects the first and second lines of the braided ligament body, and the second knot 322 in the first row connects the third and fourth lines of the braided ligament body.

[0036] In the second row, only the inner eight threads participate in forming four right-front right-front RFRF double knots. The two outer threads in this row exist as transition lines and do not participate in knot formation. The second row of this bionic ligament has a total of eight braided threads participating in the structural weaving. Each pair of threads forms a group of braided threads, for a total of four groups. In each group, the left side thread is a wrapping thread, and the right side thread is an axis. At this point, the left wrapping thread of each group of braided threads in the second row is the right axis of each group of braided threads in the first row. This means that as the knot direction changes, the braided threads of the bionic ligament will alternate between axis and wrapping threads, forming different connection and force transmission paths. The left wrapping thread of each group of braided threads in the second row wraps around the axis from the rear, extends from the left rear, and presses down on the wrapping thread to form a single-loop half knot. It then wraps around the axis again from the rear, extends from the left rear, and presses down on the wrapping thread to form the lower half-loop half knot. At this point, the wrapping thread is still on the left side of the axis. At this point, the first node 323 of the second row connects the second and third lines of the first row, and connects the first node 321 of the first row with the second node 322 of the first row.

[0037] All ten lines in the third row participate in forming five left-front left-front LFLF double knots. The two outermost lines participate in weaving, repeating the weaving method of the first row. The first knot 324 of the third row connects the first and second lines of the main body of the braided ligament. The second knot 325 of the third row connects the third and fourth lines of the main body of the braided ligament. The braiding line of the first knot 323 of the second row is untied.

[0038] As odd-numbered rows with five nodes alternate with even-numbered rows with four nodes, the functional role of the wires changes between adjacent rows. In one row, the wire acts as a holding wire, while in the next row it becomes a working wire participating in the braiding process. This ensures that all wires are continuously interwoven within the overall structure, rather than working in pairs or in isolation. Through this combination of periodic topology and direction change, this embodiment establishes a stable mapping between local node orientation and global braiding pattern, achieving a unity of ligament geometric order and mechanical compliance.

[0039] In summary, the node topology sequence modulates local geometric constraints and torque transmission paths by changing different types of nodes and their axial arrangement, thereby influencing the rhythm of stiffness growth and the smoothness of nonlinear transitions in the influence displacement curve. Different braided biomimetic ligaments exhibit different mechanical properties, such as... Figure 4 As shown.

[0040] The braiding length affects the way deformation is transmitted along the ligament axis during tension by changing the number of nodes per unit length and the unfolding path of the nodes along the axial direction. As the braiding length increases, the sequential unfolding process of the nodes is lengthened, the nonlinear region in the tension curve widens, the slope of the linear phase decreases, the overall stiffness decreases, and the mechanical response becomes smoother. Figure 5 As shown.

[0041] The number of braided strands alters the number of strands simultaneously bearing the load and the contact constraints between them. When the number of strands increases from six to twelve, the force-displacement curve shifts upward overall, the slope of the linear phase increases significantly, indicating enhanced linear stiffness. Simultaneously, more strands begin to participate in the load-bearing process at smaller displacements, promoting a more uniform load distribution along the cross-section and reducing local strain concentration. For example... Figure 6 As shown.

[0042] After preparation, the bionic ligament was subjected to tensile mechanical property tests, and the test results were compared and analyzed with the mechanical curves of the corresponding human ligaments.

[0043] like Figure 16 As shown in the figure, the blue curve represents the tensile response of human ligaments, and the red curve represents the test results of the bionic ligament prepared according to the design method of this invention. The left group of curves compares the results of the intertransverse ligaments of the lumbar vertebrae, while the right group compares the results of the interspinous ligaments. It can be seen from the figure that the prepared bionic ligament can well reproduce the nonlinear mechanical response characteristics of human ligaments during the stretching process, including the initial compliant deformation zone and the subsequent stiffness enhancement stage, and its overall trend is basically consistent with that of human ligaments. In the comparison of the interspinous ligaments, the mechanical curves of the bionic ligament and the human ligament fit well, indicating that the designed structure can achieve a high-precision match to the target mechanical behavior.

[0044] The above results demonstrate that, while maintaining the material system constant, this invention enables the determination of structural parameters from target mechanical properties and the acquisition of biomimetic ligaments with corresponding mechanical responses through pre-designed braiding topology and morphological parameters. This process reflects the characteristic that the mechanical behavior of biomimetic ligaments is pre-set by structural design, thereby achieving programmable control of the mechanical properties of biomimetic ligaments.

[0045] Example 2: The programmable bionic ligament prepared according to Example 1 is used in the lumbar segmental system.

[0046] like Figure 7 As shown, in this embodiment, the programmable bionic ligament prepared according to Example 1 is applied to the lumbar segment system to simulate and replace the interspinous ligament structure of the human lumbar vertebrae, so as to realize the biomechanical control function of the segment in flexion, extension and lateral bending movements. Figure 7The lumbar vertebrae shown are, in order, the first lumbar vertebral body 41, the second lumbar vertebral body 42, and the third lumbar vertebral body 43; the first lumbar vertebral body 41 and the second lumbar vertebral body 42 are connected by a first bionic interspinous ligament 51, and the second lumbar vertebral body 42 and the third lumbar vertebral body 43 are connected by a second bionic interspinous ligament 52.

[0047] In this embodiment 2, based on the mechanical requirements of the interspinous ligaments in different lumbar vertebral segments, a weaving structure with a relatively flexible topological sequence, a wide nonlinear region, and a gradual increase in stiffness is selected for the programmable bionic ligament. A topological arrangement of alternating five-node rows and four-node rows is adopted, so that the bionic ligament initially unfolds primarily through the gradual unfolding of the nodes under tension, and then, as displacement further increases, it shifts to primarily aligning the entire wire, thereby achieving a gradual unfolding mechanical characteristic similar to that of the interspinous ligament.

[0048] The fabricated programmable bionic ligaments are sequentially fixed to the spinous processes and laminae of adjacent vertebrae using connecting elements. Specifically, the first bionic interspinous ligament 51 and the second bionic interspinous ligament 52 span the space between adjacent vertebrae and are connected to the spinous process regions of the first lumbar vertebra 41, the second lumbar vertebra 42, and the third lumbar vertebra 43, respectively, using pre-fabricated holes or metal fixing points. During installation, moderate tension is applied to each bionic ligament to maintain a slight constraint on the lumbar segment in a neutral position, simulating the initial contribution of the interspinous ligaments to segmental stability under physiological conditions.

[0049] In multi-segment cases, such as Figure 7 As shown, different topological sequences, braiding lengths, and wire quantities can be selected according to the mobility requirements of different segments. For example, lower segments can choose a structure with a compliant topology and a wider toe area to maintain greater mobility; upper segments can choose a structure with higher linear stiffness to provide stronger stability. By combining different parameters, a gradient stiffness distribution can be formed in the longitudinal direction of the lumbar spine, making the biomimetic ligament system exhibit segmental mechanical behavior that is closer to human characteristics.

[0050] When simulating physiological and pathological states such as flexion, extension, or external impact (e.g., ligament laxity, segmental instability), the segmental stiffness can be rapidly adjusted by replacing biomimetic ligaments with different topological parameters, allowing for the study of the influence of different structural designs on segmental motion characteristics. This invention thus enables programmable nonlinear mechanical responses to be obtained in a single material system by changing the weaving topology and geometric parameters. This allows the biomimetic ligament to function as a key structure connecting joints in the lumbar spine system, exhibiting mechanical behavior close to that of the physiological interspinous ligament, and possessing good designability and scalability.

[0051] Targeting the mechanical properties of the intertransverse and interspinous ligaments of the human lumbar vertebrae, eight intertransverse ligaments and four interspinous ligaments of the lumbar vertebrae were fabricated using programmable biomimetic ligament design principles. These were integrated into a lumbar vertebral model, with the intervertebral disc serving as an initial simplified prototype of the solid-liquid coupling intervertebral disc used in the project, and lateral bending, extension, neutral, and flexion experiments were conducted.

[0052] This study validates the potential for customizable application of programmable bionic ligaments in joint systems. It demonstrates the ability to design and implant bionic ligaments with specific properties based on target biomechanical requirements, enabling precise control of joint motion characteristics while simultaneously replacing natural ligaments. This provides a feasible path for the reconstruction and optimization of ligament function in bionic joint systems.

[0053] Furthermore, the biomimetic spinal system constructed in this experiment closely approximates the mechanical response of the real human body, providing a stable and controllable experimental platform for the performance testing of solid-liquid coupled intervertebral discs in the project "Multifunctional Integrated Principle and Key Technologies of Heterogeneous Biomimetic Intervertebral Discs Based on Solid-Liquid Composites." Within this platform, the introduction of programmable biomimetic ligaments effectively eliminates the uncertainties caused by individual differences in natural ligaments, thereby achieving a standardized testing environment that more closely resembles in vivo conditions and improving the accuracy and repeatability of intervertebral disc mechanical performance evaluation.

[0054] Tensile tests were conducted on programmable bionic ligament models.

[0055] Experiment 1: Tensile tests were conducted on programmable bionic ligament templates of different lengths. Each braided structure achieves programmable length adjustment by adding transverse braiding knots. For each braided structure, specimens with lengths of 2cm, 3cm, 4cm, and 5cm were prepared. Four identical specimens were prepared for each length specification, and each specimen underwent 15 tensile tests. Figure 8 The results shown are the statistical results for 60 test data.

[0056] Experiment 2: Tensile tests were conducted on programmable bionic ligament patterns with different line counts. Each braided structure achieves programmable width adjustment by increasing the number of transverse braiding points through increasing the number of braided threads. For each braided structure, specimens with 6, 8, 10, and 12 threads were prepared. Four identical specimens were prepared for each length specification, and each specimen underwent 15 tensile tests. Figure 9 The results shown are the statistical results for 60 test data.

[0057] Summarize: Based on the results obtained from Experiment 1 Figure 8 And the results obtained in Experiment 2 Figure 9The results, comprising 3360 tensile tests across 224 samples, compared the mechanical properties of eight different braided structures in both length and width dimensions. The study clearly demonstrated the synergistic influence of transverse nodes and longitudinal segments on tensile strength, elongation at break, and modulus. As the number of transverse nodes increased, the overall rigidity of the sample improved; however, excessively dense arrangement led to increased stress concentration, resulting in a non-linear decrease in elongation at break.

[0058] Two key mechanical parameters were extracted from the stretching curve: the length of the nonlinear region and the stiffness of the linear region. The length of the nonlinear region characterizes the process of the programmable bionic ligament gradually unfolding and stretching from its coiled structure in the initial stage of stress, reflecting its deformation capacity in the small load stage, and is an important indicator for evaluating the initial compliance of the programmable bionic ligament.

[0059] Experiments were conducted to determine the length of the nonlinear region of the programmable mechanical properties of a programmable bionic ligament.

[0060] Experiment 3: Verification of the nonlinear region length of programmable bionic ligaments of different lengths.

[0061] like Figure 10 Statistical results of the nonlinear region length for different weave structures at lengths of 2cm, 3cm, 4cm, and 5cm are presented. Each structure and length combination is analyzed based on 60 sets of experimental data. Overall, the nonlinear region length exhibits a certain regular trend with increasing sample length, indicating that geometric scale has a significant impact on its initial mechanical response. Simultaneously, under the same length conditions, there are significant differences in the nonlinear region length among different weave structures. For example, in the 2cm sample, the average value of some structures is close to 1mm (e.g., ...). Figure 10 (The small image shown in the first row and first column of the image), while other structures are approximately 0.25 mm (such as...). Figure 10 The small diagram shown in the second row and second column illustrates the dominant role of structural design in nonlinear response.

[0062] Experiment 4: Verification of the length of the nonlinear region of programmable bionic ligaments with different line counts.

[0063] like Figure 11 Statistical results of the nonlinear region length for different weave structures under different thread counts (6, 8, 10, and 12 threads) are presented. Each structure and thread count combination is analyzed based on 60 sets of experimental data. Overall, the nonlinear region length exhibits a certain regular trend with the increase of the weave thread count, indicating that the number and arrangement of fibers involved in the load-bearing process have a significant impact on the initial mechanical response. Further comparison reveals that, under the same thread count, there are still significant differences in the nonlinear region length among different weave structures. For example, in the 6-thread pattern, the average length of some structures is close to 0.1 mm (e.g., ...). Figure 11 (The small image shown in the first row and fourth column of the image), while other structures are approximately 0.4 mm (such as...). Figure 11 The small figure shown in the second row and fourth column illustrates that even with the same amount of material and thread count, the morphology and topology determined by the weaving method still dominate the nonlinear deformation behavior. Furthermore, as the thread count increases, some structures exhibit a tendency for the nonlinear region to extend, while others show a more gradual change, further demonstrating the regulatory role of structural design on the mechanical response path.

[0064] Summarize: Comparative results from Experiments 3 and 4 show that, while maintaining a constant macroscopic length or number of threads, the length of the nonlinear region can be precisely adjusted by controlling the weaving nodes, i.e., changing the topology of the woven ligament. Furthermore, without altering the weaving structure, the length of the nonlinear region can also be precisely adjusted by increasing or decreasing the transverse or longitudinal nodes, i.e., changing the morphology of the woven ligament. This characteristic further demonstrates that this type of programmable bionic ligament possesses programmable nonlinear mechanical response capabilities, allowing for customization of its initial deformation behavior according to different application requirements, thereby achieving structured design and control of the functional characteristics of the programmable bionic ligament.

[0065] Experiments were conducted on the linear region stiffness of the programmable mechanical properties of a programmable bionic ligament.

[0066] Linear region stiffness is used to characterize the deformation resistance of biomimetic ligaments after the structure has fully expanded and entered the stable stress stage, reflecting their mechanical support performance and structural stability under medium and high load conditions.

[0067] Experiment 5: Verification of the linear region stiffness of programmable bionic ligaments of different lengths.

[0068] like Figure 12 Statistical results of linear region stiffness for different braided structures at lengths of 2cm, 3cm, 4cm, and 5cm are presented. Each structure and length combination is analyzed based on 60 sets of experimental data. Overall, the linear region stiffness exhibits a certain regularity trend with increasing specimen length, indicating that geometric scale has a significant impact on its response to larger tensile forces. Meanwhile, under the same length conditions, there are significant differences in the linear region stiffness among different braided structures. For example, in the 2cm specimen, the average value of some structures is close to 60 N / mm (e.g., ...). Figure 12 The small image shown in the first row and first column of the image shows this, while other structures have a resistance of approximately 200 N / mm (e.g., Figure 12 The small diagram shown in the second row and second column illustrates the dominant role of structural design in linear response.

[0069] Experiment 6: Verification of the linear region stiffness of programmable bionic ligaments with different line counts.

[0070] like Figure 13 Statistical results of linear region stiffness for different weave structures under varying thread counts (6, 8, 10, and 12 threads) are presented. Each structure and thread count combination is analyzed based on 60 sets of experimental data. Overall, the linear region stiffness exhibits a certain regularity trend with increasing thread count, indicating that the number and arrangement of fibers involved in the load-bearing process significantly affect the structure's response to large tensile forces. Furthermore, under the same thread count, there are significant differences in linear region stiffness among different weave structures; for example, in the 10-thread pattern, the average value of some structures is close to 40 N / mm². Figure 13 The small image shown in the first row and first column of the middle section), while other structures are approximately 70 N / mm (such as...). Figure 13 The small diagram shown in the second row and fourth column illustrates the dominant role of structural design in linear response.

[0071] in conclusion: Comparative results from Experiments 5 and 6 show that, while maintaining a constant macroscopic length or number of threads, the stiffness of the linear region can be precisely adjusted by controlling the braiding nodes, i.e., changing the topology of the braided ligament. Different topologies alter the load transmission path and force distribution between fibers, thus affecting the overall stiffness performance of the structure after it enters the stable stress stage. Furthermore, while keeping the braiding structure type constant, the spatial density and constraint of the fibers can be further controlled by increasing or decreasing the transverse or longitudinal nodes, i.e., changing the morphology of the braided ligament. This change affects the contact state and cooperative stress-bearing capacity between fibers, thereby altering the stiffness response of the structure in the later stages of tension. Generally, increasing the number of nodes increases the structural density and constraint, leading to increased stiffness in the linear region, while decreasing the number of nodes makes the structure more relaxed, resulting in a corresponding decrease in stiffness. This result indicates that the linear mechanical properties of this type of programmable bionic ligament not only depend on the material itself but are also dominated by structural parameters, demonstrating significant structural programmability. By coordinating the design of topology and morphological parameters, the stiffness of linear regions can be quantitatively adjusted, thereby matching the target mechanical properties according to different application requirements and realizing the structured design and optimization of the functional characteristics of programmable bionic ligaments.

[0072] Experiment 7 further verifies the programmable design capability of the biomimetic ligament described in this invention at the morphological and structural levels, such as... Figure 15 As shown, comparative images of biomimetic ligaments fabricated under different weaving parameters are presented. In the figure, (a) and (b) correspond to the morphological changes of the biomimetic ligaments under different weaving topologies, respectively.

[0073] In the experiment, by adjusting the number of braiding threads (6, 8, 10, and 12 threads respectively) and the braiding length (30 mm, 40 mm, and 50 mm respectively), multiple sets of biomimetic ligament structures with different geometric shapes were prepared while keeping the material system constant. All samples maintained the same width (20 mm) to eliminate the influence of lateral dimension variations on structural contrast.

[0074] As shown in the figure, the density and cross-sectional shape of the bionic ligament change significantly with the number of braided threads. An increase in the number of threads results in a denser structure and a more regular overall shape. Furthermore, as the braiding length increases, the degree of axial expansion of the nodes changes, leading to a more extended spatial distribution of the structure. Different parameter combinations result in significant differences in the macroscopic morphology of the bionic ligament.

[0075] Furthermore, under different weaving topology conditions, such as Figure 15 (a) and Figure 15 As shown in (b), the biomimetic ligaments with the same combination of weaving parameters still exhibit different structural orientations and spatial arrangements, indicating that the node topology sequence has a significant impact on the overall structural morphology. Different topologies alter the weaving path of the wires in three-dimensional space, providing a basis for the subsequent control of force transmission paths and deformation modes.

[0076] The above results demonstrate that the present invention can achieve controllable construction of the macroscopic morphology of biomimetic ligaments by adjusting structural parameters such as the number of braided threads, braiding length, and node topology sequence. Since these structural parameters simultaneously determine the force transmission path and geometric unfolding within the structure, this morphological control process is inherently consistent with the mechanical performance control, thus demonstrating the programmable nature of the biomimetic ligament at the structural level.

[0077] In summary, programmable bionic ligaments not only play a key structural role in bionic joint systems, but also provide important support for experimental simulation and engineering applications of complex biomechanical systems.

Claims

1. A biomimetic ligament with programmable nonlinear mechanical behavior, characterized in that: It is formed by alternating arrays of double knots (2) in different directions. Odd-numbered rows are double knots of one structure, and even-numbered rows are double knots of another structure. The continuous structure of the ligament is constructed by periodically alternating knot arrangement. Each double knot (2) consists of two basic half knots (1). The bionic ligament is woven from an axis (4) and a winding (5). The winding (5) wraps around the axis (4) and crosses once to form a basic half knot. The axis (4) and the winding (5) change the winding direction due to the change of knots. Each basic half knot (1) is characterized by two parameters, namely the winding position and winding direction relative to the holding reference. The winding position includes the left and right sides of the holding axis, and the winding direction includes forward winding and backward winding around the holding axis, thereby forming four basic patterns: left front LF half knot (11), left back LB half knot (12), right front RF half knot (13), and right back RB half knot (14). These four half structures form the basic unit of directional controllable weaving. The two basic half-knots (1) continuously woven together to form a double knot (2) is the smallest functional unit. According to the winding position and winding direction, the two basic half-knot patterns are arbitrarily combined to form eight smallest functional units, namely, left front left front LFLF double knot (21), right front right front RFRF double knot (22), left front left back LFLB double knot (23), right front right back RFRB double knot (24), left front right back LFRB double knot (25), right front left back RFLB double knot (26), left front right front LFRF double knot (27), and right front left front RFLF double knot (28).

2. The biomimetic ligament with programmable nonlinear mechanical behavior according to claim 1, characterized in that: The aforementioned bionic ligament is based on the eight minimum functional units described above: Alternatively, it can be constructed using a double node (21) with left front left front LFLF nodes for odd-numbered rows and a double node (21) with left front left front LFLF nodes for even-numbered rows. Alternatively, a double node with left-front-left-front-LFLF for odd-numbered rows (21) and a double node with right-front-right-front-RFRF for even-numbered rows (22) can be constructed. Alternatively, it can be constructed using a double node with left front left front LFLF (21) for odd-numbered rows and a double node with left front right back LFRB (25) for even-numbered rows; Alternatively, it can be constructed using a double node with left front left front LFLF for odd-numbered rows (21) and a double node with right front left back RFLB for even-numbered rows (26); Alternatively, it can be constructed using a left-front-left-back LFLB double node (23) for odd-numbered rows and a left-front-left-back LFLB double node (23) for even-numbered rows; Alternatively, it can be constructed using a double node with left front and left back LFLB for odd-numbered rows (23) and a double node with right front and right back RFRB for even-numbered rows (24); Alternatively, it can be constructed using a double LFLB node with left front and left back nodes in odd-numbered rows (23) and a double LFRF node with left front and right front nodes in even-numbered rows (27); Alternatively, it can be constructed using a double node with left front left back LFLB for odd-numbered rows (23) and a double node with right front left front RFLF for even-numbered rows (28).

3. The biomimetic ligament with programmable nonlinear mechanical behavior according to claim 1, characterized in that: The shaft (4) and the winding (5) are made of high-modulus polyethylene fiber or polyethylene terephthalate fiber.

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