CN208313736U - Bionical bone samples for the shock-testing of Terahertz original position - Google Patents

Abstract

The utility model relates to a kind of bionical bone samples for the shock-testing of Terahertz original position, belong to Biomechanics test field.The bionical bone samples being made of bionics skin-muscle-bone are constructed by topological structure from outward appearance to inner essence.The Bionics Bone with porous gradient characteristics is prepared, is also attached to Bionics Bone outer layer with the bionic muscle of natural biological mechanics of muscle similar performance, outer layer covers artificial skin is fabricated to the bionical bone samples of simulation complete bio extremity body structures.Thin-film pressure sensor is embedded in each component part of bionical bone samples, comprehensive, multi-level, three-dimensional detection is carried out to impact force value suffered by each component part of bionical bone samples.Alternative nature bone carries out impact property and tests and can integrate various new detection mode, a kind of effective tool not only is provided for biological Impact Properties of Materials test, but also provides a kind of new research means for the research of the impact failure mechanism of the biomimetic materials utensils such as bionical limbs, the bionical bone of implanted.

Description

Bionical bone samples for the shock-testing of Terahertz original position

Technical field

It is the utility model relates to Biomechanics test field, in particular to a kind of for the imitative of Terahertz original position shock-testing Raw bone samples.The utility model can be used for simulating the mechanical property of natural biologic material and replace its progress Terahertz former in real time The lower shock-testing of position detection, for the test of biomimetic material sample impact property provide it is a kind of it is repeated by force, can largely prepare it is more Function sample, which, which compensates for nature bone and be made after sample, has the shortcomings that larger difference in structure and ingredient, reduces natural The unnecessary experimental variable of bone difference bring provides preparation simply for the test of nature bone impact property and mechanical property repeatability The Measurements of Material Mechanical Performance such as high normalized sample is also biomimetic material, biomaterial for medical purpose provide a kind of new research Means.

Background technique

In daily life, organism is often by the influence of various shock loadings, due to shock loading wink Between generation destructive power it is larger, huge injury, especially bone often are brought to organism, by greater impact load When often generate the more serious consequence such as bone split, fracture.Therefore we need to the bone of organism in impact force action Under failure, failure mechanism studied, due to nature bone be it is more complicated, different parts, different role bone shape, knot All there is apparent differences for structure, density, hardness, carry out impact experiment often to bone because of the production of sample, nature bone Acquisition limited source and keep experimental result otherness big in addition some experiment bone (such as human body bone) be inherently difficult to obtain, because This finds in mechanical property close to nature bone and the substitution sample that can largely produce becomes the test of nature bone impact property urgently A problem to be solved.

Bio-medical material has characteristics that good biocompatibility, safety, certain mechanical strength, controllable The biological degradability of system, these characteristics are also that natural biomaterial is possessed, not comparable due to possessing these other materials Quasi- advantage, so that it is providing a brand-new approach for research natural biologic material impact property test.Nature bone is The composite material of natural organic matter and inorganic matter is mainly made of organic matter, inorganic matter and water etc., and organic components account for about bone The 35% of gross mass, wherein collagenous fibres account for about 95%, remaining is [amorphous.Type i collagen fiber accounts for 90% in collagenous fibres. [amorphous is mainly the compound of protein and polysaccharide, such as chondroitin sulfate, hyaluronic acid.Inorganic matter accounts for the total of bone The 60% ~ 70% of quality, main component are hydroxyapatites.For bone bionical beginning mainly based on ingredient and structure, but Since the Bionics Bone of this biomimetic material production enbrittles the disadvantages of big, mechanical property is poor compared with nature bone, promote people must It must make improvements.The main material of Bionics Bone is divided into following three classes: HA/ organic composite material at present, organic phase be collagen, Polyethylene, polymethyl ester methyl ester etc.；HA/ inorganic composite materials, inorganic phase are mainly CaO, Al₂O₃、CaSO₄Deng；HA is thin Film, substrate are mainly metal, including Ti, Co-Cr-Mo alloy and stainless steel etc..To connect bionical bone structure in mechanical property Nearly natural bone biologic material and the needs that in situ detection is carried out in integrated THz imaging technology, select HA/ to have during fabrication Machine composite material.Compared with this material of latter two material in terms of composition with the ingredient of nature bone more closely, utilizing this material Expect the sample made closer nature bone in terms of impact property, the reliability of experimental data is higher, and otherness is smaller." 3D is beaten Print technology " is also " increases material manufacturing technology ", is a kind of using layer-by-layer rapid shapings of adhesive materials such as powdery metal or plastics Technology.3D printing technique can make structure and the very complicated entity of shape, and grinding tool needed for not needing manufacture production.Phase It is to process required shape based on cutting off extra material for traditional material manufacture that subtracts, 3D printing technique can be according to adding The structure and size of work require reasonably use, distribution material greatly to save so that the utilization rate of material has significant raising Material and processing cost are saved.Nowadays with the development and maturation of 3D printing technique and equipment, its use scope is more and more wider, The type of printed material also gradually increases.Currently, 3D printing technique has been applied to biologic medical field, especially in Bionics Bone Inside fine structure, the shape wheel of bone are studied by carrying out structural analysis to the skeleton dissection model to be made in equal fields Wide and mechanical property, then converts obtained data to the Fabrication parameter of 3D printing, by control 3D printing technological parameter, The size of basic material ingredient and material, shape, the bionical mold thus manufactured just have the compact bone and spongiosa of nature bone The structure feature of bone, and possess the mechanical property very close with nature bone, Bionics Bone can from structure, mechanical property, shape, The accuracy of manufacture and surface roughness etc. realize the imitation to bone.Not only meet knot by the sample that 3D printing technique manufactures Simulation in terms of structure and mechanical property to nature bone, and machining accuracy with higher and processing efficiency.Therefore this is selected to add The manufacture of the complete paired samples of work mode.Terahertz is a kind of electromagnetic wave of wavelength between 0.03mm ~ 3mm, and corresponding frequency is 10THZ ~ 0.1THZ, due to the development of ultrafast laser technique so that Terahertz Technology reaches its maturity, Terahertz Technology communication, Contain huge application prospect and unrivaled advantage in terms of national defence, medicine, space flight, thus receives the wide of developed country General attention.In life medicine field, Terahertz has following unique application advantage and characteristic.1) photon energy of Terahertz is very It is low, it is approximately the 1/10 of X-ray⁶, this energy will not the intracorporal molecule of ionized biological.2) vibration and rotation of most large biological molecules Turn frequency all within the scope of Terahertz, thus shows very strong absorption and resonance in terahertz wave band.3) Terahertz can be with very Small decaying penetrates nonmetallic substance such as fat, fiber, plastics.Biological innocuousness, high-penetration based on Terahertz etc. are only Special advantage is applied in the impact property test of biomaterial, can be research skeletal structure deformation, underbead crack, destruction Mechanism provides a kind of novel detection means and research angle.

Do impact property test using nature bone and mainly face following two problem: 1, the resource of experiment nature bone is limited Prevent sample is from largely preparing or even some experimental materials (such as skeleton) are difficult to obtain, thus cause experimental repeatability Experimental data poor that abundance obtains.2, nature bone due to its position, effect difference cause the forms of bone, micro-structure, It differs greatly between mechanical property, density, growing environment, eating habit, the difference of health status also result in bone with poor The opposite sex causes to bring unnecessary Variable Factors, error to experiment due to the intrinsic mechanics of sample itself, architectural difference, makes reality The impact property of nature bone cannot clearly be reflected by testing data, it would be highly desirable to be solved.

Summary of the invention

The purpose of this utility model is to provide a kind of bionical bone samples for the shock-testing of Terahertz original position, solve The above problem of the existing technology.The alternative nature bone of the utility model carries out impact property and tests and can integrate various new Detection mode, the sample not only can provide a kind of effective tool for biological Impact Properties of Materials test, but also can be bionical The research of the impact failure mechanism of the biomimetic materials utensils such as the bionical bone of limbs, implanted provides a kind of new research means.

The above-mentioned purpose of the utility model is achieved through the following technical solutions:

Sample generally rectangular-shape, including imitative compact bone 1, sensor array 2, bionic muscle 3, artificial skin 4, main biography Sensor 5, imitative cancellous bone 6, hydrogel 7.The imitative cancellous bone 6, imitative compact bone 1 and hydrogel 7 constitute bionical bone structure, Bionics Bone Structure is the main structure of sample and the test object of impact property experiment.Imitative cancellous bone 6 is that internal distribution has function rule Cylinder hole array rectangular parallelepiped structure, when facing imitative 6 left view of cancellous bone, from vertical vertically symmetrical axis direction to two sides cylinder Hole porosity parabolically successively decrease by rule, remains unchanged along vertically symmetrical axis direction porosity；When facing top view, from vertical water Equalling symmetrical axis direction, parabolically rule is successively decreased to two sides cylindrical hole porosity, is kept not along horizontal symmetrical axis direction porosity Become, the cylindrical hole array structure in both direction follows identical parabolic function rule.Imitative cancellous bone 6 and imitative compact bone 1 are real It is integrated；Filling hydrogel 7 simulates marrow in the hole of imitative cancellous bone 6；Production material using medical silica-gel as bionic muscle 3 Material, is adhered to by 3D printing technique and is fixed on imitative 1 surface of compact bone to simulate muscle；Artificial skin 4 is wrapped in bionical 3 outer layer of muscle.During bionical bone samples are hit, using Terahertz in situ detection technology to the deformational behavior of sample, Defect evolution mechanism and splitting mechanism are analyzed in real time.

Sensor array 2, master reference 5 select thin-film pressure sensor, by 5 groups of sensor array 2, master reference At sensor group be embedded into each structure sheaf of sample the Extending Law of impact force and power in all directions suffered by detection structure. The sensor group that master reference 5, sensor array 2 are constituted arranges three layers from inside to outside, and first layer sensor group is arranged in imitative pine 6 outer surface of matter bone and 1 inner surface junction of imitative compact bone are to detect imitative cancellous bone impact force numerical value；The insertion of second layer sensor group Imitative 1 outer surface of compact bone, makes sensor sensing area two sides be fitted in 1 outer surface of 3 inner surface of bionic muscle and imitative compact bone respectively Detect imitative 1 impact force numerical value of compact bone；Third layer sensor group is embedded in 3 outer surface of bionic muscle, makes sensor circle induction zone Two sides are fitted in 3 impact force numerical value of 4 inner surface of artificial skin and 3 outer surface measuring bionic muscle of bionic muscle respectively, ignore people The influence for making skin 4 sets this layer of surveyed impact force as the initial impact force numerical value of impact bar.The sensing being embedded at each structure sheaf Device group uses identical arrangement, arranges that master reference 5 measures major skock power numerical value, three layers of sensor on percussion point 2 structure of array is arranged in the shock zone centered on shock point in rice font, and every layer of sensor array 2 includes eight pieces of sensings Device, the angle that the center of circle of the round induction zone of sensor is distributed on the circle centered on shock point and between adjacent sensors are equal It is 45 °, first layer sensor array 2 and master reference 5 are tangent, the center of circle and second of the round induction zone of first layer circular array The center of circle of the center of circle spacing distance and second layer of layer is 1:1.5 with the ratio between the center of circle spacing distance of third layer.First layer is round Between the center of circle of the round induction zone of array and the center of circle with third layer in the center of circle of the center of circle spacing distance of the second layer and the second layer Gauge is not from point can Wei 8mm, 12mm.

The utility model has the beneficial effects that: provide it is a kind of standardization, can standardized bionical bone samples.This is practical The novel bionical bone samples for instead of nature bone progress impact property test, carry out mechanical property and structure point to nature bone Analysis is simplified the fine structure of nature bone, comes out the bionical bone modelling of design using biomimetic material, adjust bionical bone Machined parameters make it have the mechanical property close to nature bone, the porosity rule application parabolic function of cancellous bone is carried out Fitting, is manufactured using 3D printing technique, replaces nature bone to carry out impact property experiment using bionical bone samples.In addition, The bionic muscle made of biomaterial, biomimetic material etc. and artificial skin are adhered in Bionics Bone structural outer surface, is fabricated to mould Biological extremity body structures under quasi- real impact environment, the influence using bionical bone samples research skin and muscle to impact force Defencive function regular and to bone.It is embedded in thin-film pressure sensor group in each structure sheaf of bionical bone samples, passes through multilayer Sensor group realizes comprehensive to bionical bone samples, multi-level, three-dimensional impact force value detection.Bionical bone samples by In impact process, using Terahertz in situ detection technology for analyzing deformational behavior, defect evolution mechanism and the layer of test specimen in real time Between peeling mechanism.

Detailed description of the invention

Attached drawing described herein is used to provide a further understanding of the present invention, and is constituted part of this application, The illustrative example and its explanation of the utility model do not constitute the improper limit to the utility model for explaining the utility model It is fixed.

Fig. 1 is the structural schematic diagram of the utility model；

Fig. 2 is the local semi-cutaway of bionical bone structure；

Fig. 3 is master reference, sensor array distribution map on the sample structure face of the utility model；

Fig. 4 is terahertz imaging Instrument observation sample position figure.

In figure: 1, imitating compact bone；2, sensor array；3, bionic muscle；4, artificial skin；5, master reference；6, pine is imitated Matter bone；7, hydrogel；8, THz source A；9, THz source B；10, THz source C；11, terahertz camera A；12, Terahertz Camera B；13, terahertz camera C.

Specific embodiment

The detailed content and its specific embodiment of the utility model are further illustrated with reference to the accompanying drawing.

Referring to FIG. 1 to FIG. 4, the bionical bone samples for the shock-testing of Terahertz original position of the utility model, can For replacing natural bone material to carry out the shock-testing under the detection of Terahertz real-time in-situ.Including imitating compact bone 1, sensor array 2, bionic muscle 3, artificial skin 4, master reference 5, imitative cancellous bone 6, hydrogel 7, the imitative cancellous bone 6, imitative compact bone 1 and water Gel 7 constitutes bionical bone structure.

Bionical bone structure is the main structure of sample and the test object of impact property experiment, first to the structure of nature bone and Mechanical property is analyzed, and the porosity rule of imitative cancellous bone 6 is fitted with parabolic function, establishes succinct, standardization Bionics Bone structural model and determine 3D printing parameter.Make Bionics Bone that there is mechanical property similar with nature bone, reduces its knot The complexity and diversity of structure.The making material of bionical bone structure is hydroxyapatite and collagenous fibres compound, is beaten using 3D Print technology is manufactured by designed Bionics Bone structural model, and the Bionics Bone manually made simulates and matches experiment nature bone Material.Filling hydrogel 7 simulates marrow in the hole of imitative cancellous bone 6.Mechanical test is carried out to the muscle at nature bone, is measured Influence of the muscle to impact force numerical reduction, the material using medical silica-gel as bionic muscle 3, by 3D printing technique by its Adhere to and be fixed on imitative 6 surface of compact bone to simulate muscle, the thickness of bionic muscle 3 is according to the muscle pair at experiment nature bone The mechanics influence of bone determines.Mechanical test, influence rule of the analyzing skin to impact property are carried out to the skin near experiment bone Rule makes it have mechanical property similar with natural skin and is wrapped in bionic muscle 3 by adjusting the thickness of artificial skin 4 Outer layer.By designing above, by sample making at the bionical bone samples of simulation complete bio extremity body structures.

The sensor group that sensor array 2, master reference 5 form is embedded into each structure sheaf of sample suffered by detection structure The Extending Law of impact force and power in all directions.The sensor group that master reference 5, sensor array 2 are constituted is from inside to outside Three layers of arrangement, first layer sensor group, which is arranged on the inside of imitative 6 outside of cancellous bone and imitative compact bone 1, measures the suffered punching of imitative cancellous bone 6 Hit power numerical value；Second layer sensor group is embedded in imitative 1 outer surface of compact bone, and sensor sensing area two sides are fitted in Bionic muscle respectively 3 inner surface of meat and 1 outer surface measuring of imitative compact bone imitate 1 impact force numerical value of compact bone；Sensor group is embedded in Bionic muscle by third layer 3 outer surface of meat, and be fitted in sensor circle induction zone two sides respectively outside 4 inner surface of artificial skin and bionic muscle 3 and show, The impact force of third layer is set as the initial impact force numerical value of impact bar.The sensor group being embedded at each structure sheaf is using identical Arrangement arranges that master reference 5 measures major skock power on percussion point, is in rice word by three layers of 2 structure of sensor array Type is arranged in the shock zone centered on shock point, and every layer of sensor array 2 includes eight pieces of sensors, the round sense of sensor Angle on the circle for answering the center of circle in area to be arranged in centered on shock point and between adjacent sensors is 45 °, first layer sensing Device array 2 and master reference 5 are tangent, the center of circle of the induction zone of first layer sensor array and the center of circle spacing distance of the second layer and The center of circle of the second layer is respectively 10mm, 15mm with the center of circle spacing distance of third layer.

The detection method of the bionical bone samples for the shock-testing of Terahertz original position of the utility model is as follows:

Make detection module using terahertz imaging system in the impact property experiment of bionical bone samples and carries out inspection in situ It surveys, by adjusting the relative position of terahertz imaging instrument and sample room, realizes to the carry out multi-angle of sample, three-dimensional sight It surveys.Sample observation angle is designed as three in the utility model, by THz source A8, B9, C10 and THz wave camera before experiment A11, B12, C13 are arranged in design observation position, in the sample side location arrangements Terahertz vertical with shock point action direction Source C10, in the other side, isometry position arrangement terahertz camera C13 predominantly detects the deformational behavior of internal imitative cancellous bone, defect is drilled Change mechanism and splitting mechanism, sample front arrange THz source A8 and THz source B9, two THz sources A8, B9 with The plane of percussion point composition keeps horizontal and line and impact force action between THz source A8, B9 and percussion point The angle of line is identical, and terahertz camera A11 and terahertz camera B12 are arranged in sample rear ramp and emission source, position and too Hertz camera keeps sight alignment, change when being impacted using front and back to the terahertz imaging system detection sample front of arrangement Phenomena such as shape, crackle.By the way that the information observed on three directions is compared, combinatory analysis, obtain Bionics Bone interior three-dimensional Three-dimensional deformation, fracture image information.

Embodiment:

Referring to figs. 1 to shown in Fig. 4, the bionical bone sample of Terahertz original position shock-testing is used for involved by the utility model Product, the size of main body of sample are 120mm × 60 mm × 10mm, are suitable for medium-and-large-sized impact property test equipment.

The sample of the utility model is using 3D printing technique using the manufacture from inside to outside, successively printed.According to phase Closing the natural cancellous bone of paper data has following rule: the center line along column bone horizontally outward until compact bone, cancellous bone Porosity is gradually reduced；On the contour section of the parallel direction with column bone center line, the numerical value of porosity is kept not substantially Become.The fitting that a kind of parabola rule is proposed to the porosity of imitative cancellous bone, analyze the nature bone of experimental study fine structure, Physical property and mechanical property simplify bone structure and remove its complexity and diversity redesign Bionics Bone structural model, utilize 3D printing parameter is arranged in experimental data, and the parameter by adjusting the imitative compact bone of manufacture makes it have mechanical property similar with nature bone Energy.The material that bionical bone structure uses is HA/ organic composite material, and organic phase is collagen, polyethylene, polymethyl ester methyl ester It is close with the constituent of nature bone in constituent Deng, this material, thus otherness is small, makes sample and impact experiment more With convincingness.Hydrogel is filled in cancellous bone structure simulates marrow.Mechanical test is carried out to the muscle at nature bone and is divided Analysing muscle influences impact force numerical reduction, analyzes the fine structure of muscle and determines required 3D printing parameter, use is medical Silica gel makees material production and is adhered to and be fixed on bionical bone surface, and the thickness of medical silica-gel is according to the mechanical property of natural muscle It is adjusted.Bionic muscle in sample selects silicon rubber, it has colourless, nontoxic, resistance to oxidation, good biocompatibility etc. excellent Point, and there is the characteristics similar with natural muscle such as soft sense of touch.Mechanics property analysis is carried out to the skin at nature bone, adjusts people The thickness for making skin is close to influence of the natural skin to impact property and artificial skin is adhered to bionic muscle surface.It is logical The above design is crossed, by sample making at the bionical bone samples of simulation complete bio extremity body structures.

Impact force value suffered by structure each in impact experiment is carried out using thin-film pressure sensor inspection multi-level, three-dimensional Detection.The sample of the utility model selects RX-D1016 fexible film pressure sensor, and RX-1016 is the pressure resistance type of a standard Flexible sensor, master reference are made of round induction zone and DOL Data Output Line, induction diameter be 10mm, outer diameter 16mm, The range of selection is 10 ~ 25kg with a thickness of 0.2mm, and it is 200mm that DOL Data Output Line, which selects length,.The static resistance of RX-1016 For 1 ~ 200M, hysteresis is less than 5%, and for drift rate less than 6%, operating voltage is less than 10ms in 3 ~ 5V, response time.Three layers of circle Diaphragm type formula pressure sensor in array is mainly distributed on impact force action marginal zone or the zone of influence, therefore selects to obtain pressure range It is smaller, in the utility model select RFP resistance-type diaphragm pressure sensor, selected range be 0 ~ 10kg, two kinds of 0 ~ 5kg, wherein The selection great Cheng close apart from impact zone.The diameter of induction zone is 6mm, and with a thickness of 0.1mm, transmission line overall length is 200mm.Utilize this The advantages that kind sensor bulk is small, measuring accuracy is high, realization precisely detect impact force suffered by component part each in sample.

By terahertz imaging system to the deformational behavior of bionical bone samples, defect evolution mechanism and splitting mechanism Phenomenon is measured in real time, and terahertz imaging system selects the Terahertz camera arrangement of U.S. TeraSense company, selection type Number it is Tera-4096, has 4096 pixel arrays (64X64), the size of terahertz imaging equipment is 16.5cmX16.5cmX4.5cm.The frequency of THz source is 0.05 ~ 0.7THz, and the THz wave of this range can penetrate big portion Point object, Terahertz instrument can be mounted on support frame by when experiment or the position driving enterprising line position of platform is set movement and solid Fixed, which has many advantages, such as fast response time, imaging clearly, simple and easy to use.

The foregoing is merely the preferred embodiments of the utility model, are not intended to limit the utility model, for ability For the technical staff in domain, various modifications and changes may be made to the present invention.It is all to made by the utility model it is any modification, Equivalent replacement, improvement etc., should be included within the scope of protection of this utility model.

Claims (2)

1. a kind of bionical bone samples for the shock-testing of Terahertz original position, it is characterised in that: sample generally rectangular-shape, Including imitative compact bone (1), sensor array (2), bionic muscle (3), artificial skin (4), master reference (5), imitative cancellous bone (6), hydrogel (7), the imitative cancellous bone (6), imitative compact bone (1) and hydrogel (7) constitute bionical bone structure, bionical bone structure It is the main structure of sample and the test object of impact property experiment；Imitative cancellous bone (6) are the length of internal distribution cylindrical hole array Cube structure imitates cancellous bone (6) and imitative compact bone (1) structure actually one；Hydrogel is filled in the hole of imitative cancellous bone (6) (7) marrow is simulated；Making material using medical silica-gel as bionic muscle (3), is adhered to and is consolidated by 3D printing technique Imitative compact bone (1) surface is scheduled on to simulate muscle；Artificial skin (4) is wrapped in bionic muscle (3) outer layer.

2. the bionical bone samples according to claim 1 for the shock-testing of Terahertz original position, it is characterised in that: described Sensor array (2), master reference (5) be thin-film pressure sensor, by sensor array (2), master reference (5) group At sensor group be embedded into each structure sheaf of sample the Extending Law of impact force and power in all directions suffered by detection structure； The sensor group that master reference (5), sensor array (2) are constituted arranges three layers from inside to outside, and first layer sensor group is arranged in Imitative cancellous bone (6) outer surface and imitative compact bone (1) inner surface junction are to measure impact force suffered by imitative cancellous bone (6)；The second layer Sensor group is embedded in imitative compact bone outer surface, and sensor sensing area two sides is made to be fitted in bionic muscle (3) surface respectively and imitate close Matter bone (1) outer surface is to measure impact force suffered by imitative compact bone；Third layer sensor group is embedded in bionic muscle (3) outer surface, makes Sensor circle induction zone two sides be fitted on artificial skin (4) inner surface and bionic muscle (3) outer surface respectively measure it is bionical Impact force suffered by muscle sets this layer of surveyed impact force as the initial impact force numerical value of impact bar；The biography being embedded at each structure sheaf Sensor group uses identical arrangement, arranges that master reference (5) measure major skock power on percussion point, three layers are sensed Device array (2) structure is arranged in the shock zone centered on shock point in rice font, and every layer of sensor array (2) includes eight pieces Sensor, the center of circle of the round induction zone of sensor are distributed in the angle on the circle centered on shock point and between adjacent sensors Degree is 45 °, and first layer sensor array (2) and master reference (5) are tangent, the circle of the round induction zone of first layer circular array The center of circle of the center of circle spacing distance and the second layer of the heart and the second layer is respectively 8mm, 12mm with the center of circle spacing distance of third layer.