Auxiliary cavity and design and preparation method therefor

Abstract

The present invention relates to an auxiliary cavity and a design and preparation method therefor, belonging to the technical field of medical instruments. The present invention is used for helping a patient to make an auxiliary cavity comfortable to wear in a short time. The auxiliary cavity of the present invention is designed on the basis of a soft tissue model and a bone model, is prepared by means of multi-material printing, and is worn on a limb. The auxiliary cavity, when worn on the limb, comprises one or a combination of the following functional areas: a force-bearing area, a force-sensitive area, and a heat dissipation area. The force-bearing area is a negative Poisson's ratio structural body, made of a printable hard material. The force-sensitive area is a negative stiffness structural body, made of a printable flexible material. The heat dissipation area is of a porous structure, made of a printable shape-memory polymer material. By means of the design and the preparation method provided by the present invention, the auxiliary cavity with high wearing comfort can be obtained in a short time.

Description

An auxiliary cavity and its design and fabrication method Technical Field

[0001] This case relates to the field of medical device technology, and in particular to an auxiliary cavity and its design and preparation method. Background Technology

[0002] Currently, the number of people with disabilities and animals is gradually increasing. With rising living standards, they are placing higher demands on the comfort and portability of assistive devices such as prostheses, orthoses, and exoskeletons. The socket, as a crucial component connecting the residual limb and the prosthesis, plays a vital role in transmitting the prosthesis's force, accommodating the residual limb, bearing weight, and controlling the prosthesis. Meanwhile, the fixation devices of orthoses and exoskeletons provide support, correct limb shape, and enhance limb function; they also significantly impact wearing comfort and functionality. Therefore, the design and manufacturing of these components are crucial to the overall functionality of assistive devices.

[0003] Currently, the fabrication process for sockets, orthotics, and fixation devices for exoskeletons largely relies on traditional manual customization methods, such as using plaster casts to create models. This method is time-consuming and inefficient, and the dust and harmful gases generated can pollute the environment and pose a threat to the health of operators. Furthermore, traditional methods often neglect the precise assessment of the biomechanical characteristics of the residual limb, resulting in sockets and fixation devices that may not fit individual patient differences, causing discomfort, excessive local pressure, or even injury. In reality, these rehabilitation devices are not simply replicas of the residual limb or its shape. To achieve a good fit between these components and the body's biomechanical characteristics, appropriate biomechanical adjustments based on the patient's limb shape are necessary. Because amputations and deformities vary greatly, traditional methods relying on experience and manual skills cannot guarantee the accuracy and universality of components, and repeated modifications and adjustments lead to extended delivery times and increased manufacturing costs. After long-term wear, the patient's or animal's limb may change shape, requiring periodic replacement of these auxiliary cavities, increasing the time and labor burden of repeated fabrication.

[0004] Summary of the Invention

[0005] To address the issues of insufficient comfort and long manufacturing time in existing limb-wearing auxiliary cavities, this paper aims to propose an auxiliary cavity and its design and fabrication method. The specific technical solution is as follows.

[0006] Firstly, this case proposes an auxiliary cavity worn on a limb, comprising one or a combination of the following functional areas: a load-bearing area, a force-sensitive area, and a heat dissipation area; the load-bearing area is a negative Poisson's ratio structure made of a printable rigid material; the force-sensitive area is a negative stiffness structure made of a printable flexible material; and the heat dissipation area is a porous structure made of a printable shape memory polymer material.

[0007] In one embodiment of the above technical solution, the thickness of the auxiliary cavity ranges from [1mm to 10mm], and the thickness is uniform or variable.

[0008] In one embodiment of the above technical solution, the auxiliary cavity includes a prosthesis socket, a limb orthosis, and a fixation bracket device for an exoskeleton robot.

[0009] In one embodiment of the above technical solution, the surface of the auxiliary cavity has a pattern.

[0010] In one embodiment of the above technical solution, the types of printable rigid materials include: polylactic acid, acrylonitrile-butadiene-styrene copolymer, and impact-resistant polystyrene.

[0011] In one embodiment of the above technical solution, the types of printable flexible materials include: silicone and gel.

[0012] Secondly, this case proposes a method for designing and fabricating an auxiliary cavity, the method comprising the following steps: obtaining a first auxiliary cavity model based on a skeletal model and a limb model of a wearable limb; determining the functional areas of the first auxiliary cavity model as one or a combination thereof according to the wearable limb: the functional areas include a load-bearing area, a force-sensitive area, and a heat dissipation area; adjusting the dimensions of the functional areas and the remaining parts, and smoothing the wearable inlet end to obtain a second auxiliary cavity model; obtaining a soft tissue model by subtracting the skeletal model from the limb model, and then applying the second auxiliary cavity model... The auxiliary cavity is assembled with the soft tissue model, bone model, and bushing model. If there is no interference between the auxiliary cavity and the bone, soft tissue, and bushing during the simulation, the shape of the auxiliary cavity is adjusted based on the force analysis of the worn limb and combined with biomechanical characteristics to obtain a third auxiliary cavity model. The third auxiliary cavity model is then printed, wherein: the load-bearing area is a negative Poisson's ratio structure made of a printable rigid material; the force-sensitive area is a negative stiffness structure made of a printable flexible material; and the heat dissipation area is a porous structure made of a printable shape memory polymer material.

[0013] In one embodiment of the above technical solution, the size adjustment steps include: pressing the model corresponding to the force-bearing area inward [1mm, 10mm], increasing the model corresponding to the force-sensitive area outward [1mm, 10mm], shrinking the model of the remaining parts [0, 5%], then smoothing the overall model and offsetting it by [1mm, 10mm] to obtain the bushing model, and finally performing a shelling process on the bushing model, with a shelling thickness range of [1mm, 10mm]; if the limb end is bony, then the auxiliary cavity model is lengthened [1mm, 20mm].

[0014] In one embodiment of the above technical solution, the stress analysis includes the following steps: simulating the bone model and auxiliary cavity model using an isotropic and uniform linear elastic model, and simulating the soft tissue using a hyperelastic material; virtual topology of the multi-curved surfaces of the bone, soft tissue, bushing, and auxiliary cavity models, wherein the virtual topology of the outer surface of the bushing and the inner surface of the auxiliary cavity is a single surface; dividing the bone, soft tissue, bushing, and auxiliary cavity models into tetrahedral meshes, setting contact constraints between the bone and soft tissue, contact constraints between the soft tissue and bushing, and hard contact constraints between the bushing and the auxiliary cavity, and setting the friction coefficient between the bushing and the receiving cavity; and using finite element analysis to analyze the distribution of stress and strain in each region of the soft tissue.

[0015] In one embodiment of the above technical solution, the steps for obtaining the skeletal model and soft tissue model include: performing three-dimensional modeling of the limb's bones and limb based on image data of the wearable assistive cavity limb to obtain an initial skeletal model and limb model; in the initial skeletal model, cortical bone and cancellous bone are modeled as the same type of material, and then the defects of the skeletal model are optimized for shape, including defects such as gaps, connections, holes, noise, and burrs, to finally obtain a smooth skeletal model; in the initial limb model, skin, fat, and muscle are retained as soft tissue, and cortical bone and cancellous bone are retained as the same type of bone, while ligaments and / or cartilage are discarded as appropriate, and then the defects of the limb model are optimized for shape to obtain a smooth limb model, and finally the final skeletal model is deleted from the limb model to obtain the final soft tissue model; wherein: the defects include gaps, connections, holes, noise, and burrs.

[0016] The beneficial technical effects of this case are as follows: By adopting the design and manufacturing method proposed in this case, the auxiliary cavity is divided into different functional areas according to the limb to which it is worn, including a force-bearing area, a force-sensitive area, and a heat dissipation area. The auxiliary cavity can have one of these functional areas or a combination of functional areas, and the functional areas can be adjusted according to the force analysis and biomechanical characteristics of the limb to meet the needs of different individuals, improve the wearing comfort of the auxiliary cavity, and shorten the manufacturing time of the auxiliary cavity through multi-material printing. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a flowchart of the auxiliary cavity design and preparation method in one embodiment.

[0019] Figure 2 is a schematic diagram of bone and limb model reconstruction based on patient CT data in one implementation method.

[0020] Figure 3 is a schematic diagram of the bone model processing steps in one implementation method.

[0021] Figure 4 is a schematic diagram of the auxiliary cavity model in one implementation method.

[0022] Figure 5 shows a partial appearance adjustment of the auxiliary cavity model in one implementation method.

[0023] Figure 6 shows a hole model of a portion of the auxiliary cavity model in one embodiment.

[0024] Figure 7 is a schematic diagram of the assembly of the skeletal model, soft tissue model, bushing model, and auxiliary cavity model of the residual limb in one embodiment.

[0025] Figure 8 is a stress diagram of the residual limb after compression in one embodiment.

[0026] Figure 9 is a schematic diagram of the force-bearing area, force-sensitive area, and heat dissipation area of ​​the residual limb in one embodiment.

[0027] Figure 10 is a schematic diagram of a novel auxiliary cavity designed according to several regions in one embodiment.

[0028] Figure 11 is a schematic diagram of the force-sensitive area in one implementation method.

[0029] Figure 12 is a pressure-displacement curve of the force-sensitive region in one implementation method.

[0030] Figure 13 is a schematic diagram of the auxiliary cavity model design of the exoskeleton robot in one implementation method. Detailed Implementation

[0031] To address the issues of long manufacturing times and low comfort levels associated with traditional hand-made custom prosthetic sockets, limb orthotics, and exoskeleton robot fixation devices, although 3D printing technology has been developed to improve production efficiency and precision through digital manufacturing processes, the problem of low wearing comfort persists due to unreasonable load-bearing capacity in the socket design. This is because each individual's limb that needs to wear the auxiliary socket has different load-bearing capacity and sensitivity to force.

[0032] Based on this, this paper proposes an auxiliary cavity and its design and fabrication method. The method involves acquiring precise data of the patient's residual limb or limb, designing the auxiliary cavity according to biomechanical principles, and then performing personalized optimization through mechanical analysis based on the functional area division of the auxiliary cavity. Finally, the model data is imported into a 3D printer for multi-material printing. The auxiliary cavity obtained through this method not only has a short fabrication time but also significantly improves the wearing comfort of the patient's limb.

[0033] The auxiliary cavity in this case can be a prosthetic socket, a limb orthosis, or a fixation device for an exoskeleton robot. The auxiliary cavity is fixed by an assistive device, which can be a prosthesis, an exoskeleton robot, etc. The method in this case involves processes such as limb skeleton, limb model extraction and repair, auxiliary cavity model design and adjustment, assembly of limb and auxiliary cavity models, limb stress analysis and auxiliary cavity optimization, and 3D printing.

[0034] Figure 1 illustrates the design and fabrication process of the auxiliary cavity, including the following steps:

[0035] S10. Based on the patient's limb image data, obtain the limb skeleton model and limb model.

[0036] The patient can be a human or an animal. Limbs can be any part of the human body, including the upper limbs, lower limbs, waist, spine, etc. Image data of the patient's limbs can be obtained while the patient is wearing silicone / gel linings or clothing, depending on the situation. The patient should be in a relatively still position; they can lie flat on the examination table or stand. The limbs can be scanned in a relaxed, free state or under certain pre-stress restraint. The preferred method for acquiring image data is non-contact 3D scanning of the patient's limbs.

[0037] S20. Based on the limb skeleton model and limb model, design the first auxiliary cavity model.

[0038] S30. Determine the load-bearing area and force-sensitive area of ​​the first auxiliary cavity model according to the limb being worn. Adjust the size of the load-bearing area, force-sensitive area and the rest of the model, and smooth the inlet end of the wearable part to obtain the second auxiliary cavity model.

[0039] S40. Obtain the soft tissue model by removing the skeletal model from the limb model. Then, assemble the second auxiliary cavity model with the soft tissue model, skeletal model, and bushing model. If there is no mutual interference between it and the skeleton, soft tissue, and bushing during the simulation, adjust the shape of the auxiliary cavity based on the force analysis of the worn limb and combined with biomechanical characteristics to obtain the third auxiliary cavity model.

[0040] S50. 3D print the third auxiliary cavity model.

[0041] It is important to note that the steps in a flowchart do not have to be performed in sequence. Instead, operations can be performed in reverse order or simultaneously. Furthermore, one or more additional steps can be added to the flowchart, or one or more steps can be removed from it. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0042] The following will, with reference to Figure 2-13, use the lower limb receptacle of the human body as an example to clearly and completely describe how the technical solution of this case is implemented.

[0043] S11. Based on the patient's lower limb image data, obtain the limb skeleton model and limb model.

[0044] Use CT or MRI scans to obtain DICOM format CT or MRI data of the stump as image data.

[0045] Based on limb image data, 3D models of the patient's limb bones and soft tissues are created to obtain an initial skeletal model and a limb model (see Figure 2 for illustration). In the initial skeletal model, if the patient's limb has defects such as missing parts, connections, holes, or noise, the model undergoes shape optimization. For example, smoothing and repairing the model's surface involves some or all of the following steps: deleting holes, filling holes, removing features, deleting nails, relaxing, reducing noise, and sanding. Subsequently, through four steps—outline division, surface patch construction, grid construction, and surface fitting (see Figure 3 for illustration)—a skeletal model with smooth outlines and no self-intersecting surface patches is finally obtained. In the initial soft limb model, skin, fat, and muscle are treated as soft tissue and retained; cortical bone and cancellous bone are treated as similar materials and retained; cartilage and ligaments can be discarded as needed. Defects in the limb model, including missing parts, connections, holes, noise, and burrs, are addressed through shape optimization to obtain a smooth limb model.

[0046] S21. Based on the limb skeleton model and limb model, design the receiving cavity model.

[0047] First, the receptive cavity model of the patient's limb is designed using the obtained limb model. The outline is defined based on the patient's limb model, the boundaries are smoothed, the apex is deleted, and then the scars on the surface of the residual limb are smoothed.

[0048] Next, based on the limb skeletal model and the limb model, the socket model is divided into a weight-bearing area and a force-sensitive area, and a set of curved surfaces is constructed. The force-sensitive area includes the tibial crest, tibia, and distal fibula, while the weight-bearing area includes ligaments, the popliteal fossa, the lateral and medial sides of the tibia, etc. The model in the force-sensitive area is expanded outwards by 1-10 mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or a decimal between adjacent integers. The model in the weight-bearing area is compressed inwards by 1-10 mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or a decimal between adjacent integers. For other areas, the model is reduced by 0-5%, for example, remaining unchanged, or reduced by 1%, 2%, 3%, 4%, etc., with a maximum reduction of 5%. If the distal tibia is bony, the socket will be lengthened by 1-20mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, or a decimal between adjacent integers.

[0049] Next, the overall model is smoothed. Then, the overall model is offset by 1-10mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or a decimal between adjacent integers, to allow for the thickness of the receiving cavity bushing. The offset bushing model is then shelled, with a shell thickness of 1-10mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or a decimal between adjacent integers, resulting in a uniform or variable thickness. Finally, the top of the model is smoothed. The processed model is the receiving cavity model (see Figure 4).

[0050] In addition, to improve the appearance of the receiving cavity model, patterns are added to its surface, as shown in Figure 5. These patterns can resemble skin texture, making the receiving cavity look more like part of the limb, thus enhancing its aesthetics and structural stability. To increase the breathability of the receiving cavity and facilitate perspiration or heat dissipation of the residual limb, appropriate holes are machined into the receiving cavity model, as shown in Figure 6.

[0051] S31. Assemble the limb skeleton model, soft tissue model, bushing model, and receptive cavity model.

[0052] First, the limb, bone, bushing, and socket models are aligned at the origin. Then, the bone model within the limb is deleted to obtain the soft tissue model. Next, the model is rotated to a suitable position using software. Then, the socket or bone, soft tissue, and bushing models are offset until the socket is no longer in contact with the muscle, soft tissue, and bushing models. Finally, an interference check is performed to ensure that there is no mutual interference between the socket and the bone, soft tissue, and bushing models during movement. If interference exists, return to steps S21 and S31 for design adjustments. If there is no mutual interference, proceed to step S41. See Figure 7 for an assembly diagram.

[0053] S41. Based on the force analysis of the patient's limbs, the receiving cavity model is modified.

[0054] Finite element analysis is the preferred method for analyzing the force exerted on a patient's limbs. Details are as follows.

[0055] First, as mentioned above, the model in this case is divided into a skeleton, soft tissue, bushing model, and receiving cavity model. For the skeleton and receiving cavity models, their materials are defined as isotropic and homogeneous linear elastic models to ensure convergence of the calculation results. The Young's modulus of the skeleton model is 10 GPa, and the Poisson's ratio is 0.3. The Young's modulus of the receiving cavity model is 2 GPa, and the Poisson's ratio is 0.4. The Young's modulus of the bushing model is 2 MPa, and the Poisson's ratio is 0.45. Since soft tissue materials have nonlinear, viscoelastic characteristics and are incompressible, this case uses hyperelastic materials to simulate the soft tissue. The Mooney-Revlin hyperelastic model is selected for modeling, with the following material parameters: elastic modulus C10 = 85.5 kPa, hardness C01 = 21.38 kPa, and incompressibility parameter D1 = 0.459 MPa. -1 .

[0056] Since the model has a multi-surface structure, performing virtual topology on the model surfaces before analysis can increase the model's convergence probability. Specifically, virtual topology is performed on the multi-surfaces of the bone, soft tissue, bushing, and socket models, with a focus on virtually topologicaling the outer surface of the bushing and the inner surface of the socket as individual faces. Then, the mesh of the bone, soft tissue, bushing, and prosthesis socket models is divided into 5mm tetrahedral meshes. Appropriate mesh subdivision is needed for the socket and stump interfaces to improve solution accuracy and efficiency.

[0057] The residual limb and socket model features two types of contact: bone and soft tissue, soft tissue and bushing, and bushing and socket. The bone and soft tissue are inseparable, so they are set as a binding constraint. The soft tissue and bushing are in close contact, and to simplify the model, this is also set as a binding constraint. The contact between the bushing and socket is defined as a hard contact, and the friction coefficient between the bushing and socket is set to 0.5, a value that can be adjusted according to actual conditions.

[0058] The soft tissue undergoes deformation after the prosthesis is fitted with a socket and during its use. For a socket corresponding to a missing lower leg, this deformation includes both the fitting process and the upright weight-bearing state. Therefore, the stress analysis of the current socket model involves two steps: First, the socket is defined as the boundary and its bottom is fixed. A 50N force is applied to the proximal surface of the lower leg to simulate the fitting process. Alternatively, a component conversion step between the stump and the socket can be performed to simulate the stress distribution after fitting. Then, the single-leg weight-bearing state is simulated by applying the patient's body weight to the proximal femur section, analyzing the stress and strain distribution at the soft tissue-shoulder interface. See Figure 8 for strain and stress assessment of several regions of the stump in the finite element analysis.

[0059] To improve the weight-bearing capacity and wearing comfort of the prosthesis socket, this design divides the residual limb into two key areas based on the biomechanical characteristics of the patient's limb: the weight-bearing area and the force-sensitive area, as shown in Figure 9. The weight-bearing area mainly includes the lateral and medial tibia, ligaments, and popliteal fossa. These areas bear most of the body weight during walking or standing and play a stabilizing and force-transmitting role in limb movement. The force-sensitive area mainly includes the fibula, tibial crest, and distal tibia. These areas typically contain bone spurs or nerve endings and respond more strongly to tactile stimuli. Therefore, special attention must be paid to the comfort and protection of these areas when designing and fabricating the prosthesis socket.

[0060] Referring to Figure 10, a negative Poisson's ratio structural unit is introduced into the force-bearing area of ​​the prosthesis socket. This structure allows the force-bearing area of ​​the socket to be appropriately compressed during patient wear, thereby reducing the maximum pressure on this area and improving the comfort of the residual limb patient. The negative Poisson's ratio structural unit includes, but is not limited to, concave-angle structures, antipalmar structures, and rotationally rigid structures. The force-bearing area is made of printable rigid materials such as polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), and high-impact polystyrene (HIPS).

[0061] A negative stiffness structural unit is designed in the force-sensitive area of ​​the socket. This unit reduces contact stress in the force-sensitive area, thereby reducing bone spurs or nerve ending stimulation and improving patient comfort. Referring to Figure 11, the force-sensitive area of ​​the patient's residual limb does experience stress, but this stress is more stable than in other areas and does not fluctuate significantly with changes in the relative position of the residual limb and the socket. This means that during the patient's residual limb movement, regardless of the relative movement between the residual limb and the socket, the pressure on the force-sensitive area remains at a relatively constant level, while the pressure in other areas changes proportionally with the position of the socket. Figure 12 shows that the pressure-displacement curve of the force-sensitive area demonstrates the special characteristics of the negative stiffness structural unit: as the displacement of the residual limb by the socket gradually increases, the pressure on the residual limb gradually decreases. This indicates that during the wearing of the prosthesis socket, when the force-sensitive area of ​​the residual limb is touched and displaced, the pressure on that area gradually decreases. This design provides incremental comfort within the socket area, reducing stimulation of highly sensitive areas and thus improving overall prosthesis comfort throughout the wearing process. In this way, the negative stiffness structural units help distribute pressure, avoiding discomfort or pain that could be caused by excessive force concentration, ensuring a better experience and higher quality of life for patients using the prosthesis. Force-sensitive areas utilize printable soft materials such as silicone and gel.

[0062] Furthermore, this case specifically considers the unique characteristics of the gastrocnemius muscle at the posterior end of the residual limb. Because this area of ​​muscle generates heat more easily than other parts of the body, its temperature is higher, making it more prone to sweating and providing a breeding ground for bacteria. This can lead not only to skin problems such as inflammation or infection but also to the patient's comfort and overall health within the prosthesis socket. Therefore, shape memory polymer materials are chosen for fabrication in areas of the socket prone to sweating, such as the gastrocnemius muscle region. Shape memory polymer materials possess the ability to change their shape at appropriate temperature thresholds. Utilizing the temperature-responsive properties of this material, when the local temperature in the patient's gastrocnemius muscle region rises, the material in that location contracts appropriately, thereby increasing the ventilation area of ​​the socket, promoting sweat excretion, and effectively inhibiting bacterial growth. For example, printable shape memory polymer materials can be used, processed using 3D printing technology. As a further improvement, perforations can be added to increase the breathability of the auxiliary cavity.

[0063] Next, based on the feedback from disabled patients, the weight-bearing area of ​​the residual limb also has a corresponding pain threshold (see example in Table 1), and the pain threshold may vary slightly depending on the individual. However, based on the biomechanical experience of the residual limb, the shape of the receiving cavity is adjusted accordingly using the above-mentioned finite element analysis of the residual limb to improve the pressure situation at the interface between the residual limb and the receiving cavity.

[0064] Table 1 Pain thresholds of different regions on the surface of the residual limb

[0065] S51. 3D print the modified receiving cavity.

[0066] The prosthetic socket was rapidly prototyping using 3D printing. After pressure assessment, the socket model was sliced ​​using software, and the sliced ​​data was then imported into the 3D printer. Materials used included resin, nylon, glass fiber, and carbon fiber, which were used to fabricate the socket after printing.

[0067] In addition, some contact surfaces in the auxiliary cavity will be equipped with certain components, such as the receiving cavity support frame, orthotic restraint straps, and exoskeleton mechanisms. After the components are assembled, the patient will wear the device clinically.

[0068] The above embodiments, taking the prosthetic socket of a human limb as an example, introduce the design and preparation method of the auxiliary cavity. As can be seen from the method description, this invention provides personalized solutions for auxiliary cavities for different patients, ensuring a higher degree of comfort and functionality.

[0069] The above method can also be used for the fixation device of a robot exoskeleton, as shown in Figure 13. The schematic diagram shows that before designing the robot fixation device, the limb area is first divided into a load-bearing area, a force-sensitive area, and a heat dissipation area according to biomechanical principles, and then designed as a negative Poisson's ratio structure, a negative stiffness structure, and a perforated structure, respectively. The device is then 3D printed using printable rigid materials, flexible materials, and shape memory polymer materials, and the method and steps are the same as those for the receiving cavity model.

[0070] Through the above description of the embodiments, those skilled in the art can clearly understand that the method of this disclosure can obtain a wearable auxiliary cavity on the limb, which has one or a combination of the following functional areas: a load-bearing area, a force-sensitive area, and a heat dissipation area. Some auxiliary cavities only have a load-bearing area, a force-sensitive area, or a heat dissipation area. Some auxiliary cavities have a load-bearing area and a force-sensitive area, some have a force-sensitive area and a heat dissipation area, some have a load-bearing area and a heat dissipation area, and some have all three functional areas. This is determined according to the specific situation of the wearable limb. The load-bearing area is a negative Poisson's ratio structure, using a printable rigid material, such as polylactic acid, acrylonitrile-butadiene-styrene copolymer, impact-resistant polystyrene, etc.; the force-sensitive area is a negative stiffness structure, using a printable flexible material, such as silicone or gel; the heat dissipation area is a porous structure, using a printable shape memory polymer material. The thickness of the auxiliary cavity ranges from 1 to 10 mm, and the thickness can be uniform or variable. The surface of the auxiliary cavity may have a pattern.

[0071] Through the above description of the embodiments, those skilled in the art can clearly understand that a corresponding auxiliary cavity design and fabrication system can be realized according to the method of this disclosure. For example, the system obtains a limb skeleton model and a limb model from image data of the wearable auxiliary cavity limb, and obtains a first auxiliary cavity model; based on the wearable limb, the functional areas of the first auxiliary cavity model are determined to be one or a combination of the following: the functional areas include a load-bearing area, a force-sensitive area, and a heat dissipation area; the dimensions of the functional areas and the remaining parts are adjusted, and the wearable inlet end is smoothed to obtain a second auxiliary cavity model; a soft tissue model is obtained by deleting the skeleton model from the limb model, and then the second auxiliary cavity model is assembled with the soft tissue model, the skeleton model, and the bushing model. If there is no interference between it and the skeleton, soft tissue, and bushing during the simulation process, the shape of the auxiliary cavity is adjusted based on the force analysis of the wearable limb and combined with biomechanical characteristics to obtain a third auxiliary cavity model; the third auxiliary cavity model is printed, wherein: the load-bearing area is a negative Poisson's ratio structure and uses a printable rigid material; the force-sensitive area is a negative stiffness structure and uses a printable flexible material; the heat dissipation area is a porous structure and uses a printable shape memory polymer material.

[0072] The above-described methods or systems can be implemented using software and necessary general-purpose hardware, or they can be implemented using dedicated hardware, including dedicated integrated circuits, dedicated CPUs, dedicated memory, and dedicated components. Generally, any function performed by a computer program can be easily implemented using corresponding hardware, and the specific hardware structure used to implement the same function can be diverse, such as analog circuits, digital circuits, or dedicated circuits. However, for the purposes of this disclosure, software implementation is more often a preferred method.

[0073] Although the embodiments of this application have been described above in conjunction with the accompanying drawings, this application is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, not restrictive. Those skilled in the art, guided by this specification and without departing from the scope of protection of the claims, can make many other forms, all of which are protected under this application.

Claims

1. An auxiliary cavity, characterized in that: The auxiliary cavity is worn on the limb and has one or a combination of the following functional areas: a force-bearing area, a force-sensitive area, and a heat dissipation area. The load-bearing area is a negative Poisson's ratio structure, made of printable rigid material; The force-sensitive area is a negative stiffness structure made of printable flexible material; The heat dissipation area is a porous structure made of printable shape memory polymer material.

2. The auxiliary cavity according to claim 1, characterized in that, The thickness of the auxiliary cavity ranges from [1mm to 10mm], and the thickness can be uniform or variable.

3. The auxiliary cavity according to claim 1, characterized in that, The types of auxiliary cavities include prosthetic sockets, limb orthotics, and fixation brackets for exoskeleton robots.

4. The auxiliary cavity according to claim 1, characterized in that, The surface of the auxiliary cavity has a pattern.

5. The auxiliary cavity according to claim 1, characterized in that, The types of printable rigid materials include: polylactic acid, acrylonitrile-butadiene-styrene copolymer, and impact-resistant polystyrene.

6. The auxiliary cavity according to claim 1, characterized in that, The types of printable flexible materials include: silicone and gel.

7. A method for designing and fabricating an auxiliary cavity, characterized in that, The method includes the following steps: Based on the skeletal and limb models of the wearable assistive cavity limb, the first assistive cavity model is obtained; The functional areas of the first auxiliary cavity model are determined based on the limb being worn, and are one or a combination of the following: the functional areas include a load-bearing area, a force-sensitive area, and a heat dissipation area. The dimensions of the functional areas and the remaining parts are adjusted, and the inlet end of the wearable device is smoothed to obtain the second auxiliary cavity model. The soft tissue model is obtained by removing the skeletal model from the limb model. Then, the second auxiliary cavity model is assembled with the soft tissue model, the skeletal model, and the bushing model. If there is no interference between it and the skeleton, soft tissue, and bushing during the simulation, the shape of the auxiliary cavity is adjusted based on the force analysis of the worn limb and combined with biomechanical characteristics to obtain the third auxiliary cavity model. The third auxiliary cavity model is printed, wherein: the load-bearing area is a negative Poisson's ratio structure and is made of a printable rigid material; the force-sensitive area is a negative stiffness structure and is made of a printable flexible material; and the heat dissipation area is a porous structure and is made of a printable shape memory polymer material.

8. The method according to claim 7, characterized in that, The size adjustment steps include: The model corresponding to the load-bearing area is squeezed inward [1mm, 10mm], the model corresponding to the force-sensitive area is increased outward [1mm, 10mm], the model of the remaining parts is reduced [0, 5%], then the overall model is smoothed and offset [1mm, 10mm] to obtain the bushing model, and finally the bushing model is shelled, with the shell thickness ranging from [1mm, 10mm]. If the extremity is bony, the auxiliary cavity model is lengthened [1mm, 20mm].

9. The method according to claim 7, characterized in that, The force analysis includes the following steps: The skeletal model and auxiliary cavity model are simulated using an isotropic and uniform linear elastic model, while the soft tissue is simulated using a hyperelastic material. Virtual topology is applied to the multi-curved surfaces of the bone, soft tissue, liner, and auxiliary cavity models, where the virtual topology of the outer surface of the liner and the inner surface of the auxiliary cavity are single surfaces. The skeleton, soft tissue, bushing, and auxiliary cavity models are divided into tetrahedral meshes. The skeleton and soft tissue are bound by contact constraints, the soft tissue and bushing are bound by contact constraints, and the bushing and auxiliary cavity are hard contact constraints. The friction coefficient between the bushing and the receiving cavity is also set. The distribution of stress and strain in different regions of soft tissue was analyzed using the finite element method.

10. The method according to claim 7, characterized in that, The steps for obtaining the skeletal model and soft tissue model include: Based on image data of wearable assistive cavity limbs, three-dimensional modeling of the limb's skeleton and limbs is performed to obtain an initial skeleton model and limb model. In the initial skeletal model, cortical bone and cancellous bone are modeled as the same type of material. Then, the defects of the skeletal model are optimized in shape, including defects, connections, holes, noise, and burrs, and finally a skeletal model with a smooth surface is obtained. In the initial limb model, skin, fat, and muscle are treated as soft tissue and preserved, while cortical bone and cancellous bone are treated as similar bones and preserved. Ligaments and / or cartilage are discarded as appropriate. Then, the defects of the limb model are optimized to obtain a smooth limb model. Finally, the final bone model is deleted from the limb model to obtain the final soft tissue model. The defects include missing parts, gaps, holes, noise, and burrs.

Images