KR20210125660A - Preparation of ceramic scaffolds with improved strength and gyroid structure through pore structure control - Google Patents

Abstract

The present invention relates to a technology for manufacturing a ceramic scaffold having a gyroid structure with enhanced strength through control of a pore structure stretched in one axial direction, and more specifically, to a low-viscosity photo-curable ceramic slurry composition capable of applied to a ceramic-based 3D printing technology by optimizing the types and contents of a photo-curable monomer, ceramic powder, a diluent, a dispersant, and a photo-curable initiator.

Description

Preparation of ceramic scaffolds with improved strength and gyroid structure through pore structure control

The present invention relates to the manufacture of a ceramic scaffold having a gyroid structure elongated in a uniaxial direction and having improved strength through pore structure control, and a photocurable ceramic slurry composition therefor.

Metal alloys, polymers, bioactive glasses, and ceramics are mainly used as bone substitutes in the biomedical field. A porous structure is mainly used as a bone substitute. The porous structure forms a physicochemical bond with the surrounding bones when inserted into the human body, and thanks to the interconnected three-dimensional pore structure, it creates an environment favorable for the attachment, proliferation, and differentiation of bone cells. Have. In particular, bioceramics are widely used as main materials for artificial bones because they provide osteoconductivity, biostability, and appropriate biodegradability. However, there is a limitation in that the mechanical strength is weak to use the porous structure as a bone substitute, so studies to increase the mechanical strength are being attempted. One of the methods of manufacturing a porous structure having stronger mechanical strength while maintaining a high porosity is to elongate the pores of the scaffold in the uniaxial direction.

Additive manufacturing is mainly used as a method of manufacturing a scaffold having pores elongated in the axial direction so that the porous structure has high strength. Therefore, it can be manufactured to have higher mechanical strength than a porous scaffold manufactured using general manufacturing techniques such as freeze casting and sponge replication. Recently, photocurable based additive manufacturing such as stereolithography (SLA) and digital light processing (DLP) are used. SLA and DLP can manufacture scaffolds by using light to harden and laminate ceramics in a designed shape.

Using DLP technology, a ceramic molded body can be manufactured according to the designed design, but the viscosity and flow properties vary depending on the content of the ceramic slurry used. Because the degree of broadening is different, it is important to control the ceramic content and set the printing conditions such as the laminate thickness. In particular, when manufacturing a scaffold with a complex and small pore structure, the residual slurry is not properly removed after manufacturing, so clogging may occur that blocks the pores of the scaffold. The pores may be blocked. Therefore, when manufacturing a porous scaffold with a complex shape using DLP, it is necessary to develop a technology to set the ceramic slurry and printing conditions optimized for printing and design.

Development and evaluation of Al2O3-ZrO2 composite processed by digital light 3D printing; Ceramics International (2019) Volume 46, Issue 7,　May 2020, Pages 8682-8688

The present invention includes a ceramic powder, a photocurable monomer, a camphor as a diluent, a dispersant and a photocuring initiator,

In the photocurable ceramic slurry composition, the strength of the ceramic powder is improved by controlling the pore structure of 30 to 39 vol% by volume, and a photocurable ceramic slurry composition for manufacturing a ceramic scaffold having a gyroid structure elongated in the uniaxial direction. Its purpose is to provide

In addition, the present invention comprises the steps of filling the above-described photo-curable ceramic slurry composition in a container (vat);

forming a ceramic molding layer by raising a build plate by a programmed thickness from the lower surface of the container, and curing the photo-curable ceramic slurry composition into a programmed shape by ultraviolet rays irradiated from the bottom of the container; and

Another object of the present invention is to provide a method of manufacturing a ceramic molded body including; forming the ceramic molded body by repeatedly performing the rising of the build plate and the formation of the ceramic molded layer by ultraviolet rays.

The present invention includes a ceramic powder, a photocurable monomer, a camphor as a diluent, a dispersant and a photocuring initiator,

In the photocurable ceramic slurry composition, the volume of the ceramic powder is 30 to 39 vol%, and the strength is enhanced through pore structure control, and the photocurable ceramic slurry composition is elongated in a uniaxial direction.

Hereinafter, the photocurable ceramic slurry composition of the present invention will be described in more detail.

A slurry generally refers to a liquid state with low fluidity containing a high concentration of suspended substances. In the present invention, the slurry may be used in the sense of including a paste or dough state.

The photo-curable ceramic slurry composition (hereinafter, slurry composition) according to the present invention includes a ceramic powder, a photo-curable monomer, a diluent, a dispersant, and a photo-curing initiator.

The slurry composition of the present invention may include a high content of ceramic powder to improve the physical properties of the ceramic compact and structure. In the case of a composition having a low content of the ceramic powder in the slurry composition, the structure is not maintained during printing, so the design is not reproduced, and as the slurry content increases, it is difficult to reproduce a thin wall in the case of the slurry composition.

As used herein, the term "gyroid structure" is a three-dimensional structure with infinite surfaces maintained at regular intervals, and has a large surface area, so it is a biomimetic structure advantageous for attachment, proliferation, and differentiation of osteocytes when used as a bone substitute. am.

As used herein, the term “pore” means a distance between ceramic walls.

The type of the ceramic powder is not particularly limited, for example, hydroxyapatite (HA), fluorine-containing hydroxyapatite (FHA), tricalciumphosphate (TCP), BCP (biphasic calcium phosphate) , one or more selected from the group consisting of alumina, zirconia, silica, and bioglass may be used.

In addition, the content of the ceramic powder may be 50 to 80 parts by weight, 5 to 75 parts by weight, or 60 to 70 parts by weight based on 100 parts by weight of the slurry composition. In the above content range, it is possible to manufacture a ceramic molded body and a structure having excellent physical properties.

In the present invention, the photocurable monomer (monomer) may perform a role of uniformly complexing the ceramic powder and controlling the viscosity of the slurry composition and the strength of the molded body. The slurry composition used in the conventional 3D printer requires a low viscosity. However, as the content of the ceramic powder increases, the viscosity increases, which causes a problem in 3D printing. In the present invention, it is possible to prepare a molded article by preparing a slurry composition having a low viscosity, and photocuring it to laminate it.

In the present invention, the photocurable monomer may be used to include not only 'unit molecules forming a polymer' in the dictionary meaning, but also oligomers which are oligomers produced by polymerization of the unit molecules to a low degree.

The type of the photocurable monomer is not particularly limited, and an acrylate-based monomer may be used, and specifically, 1,6-hexanediol diacrylate (HDDA), urethane dimethacrylate (Diurethane) At least one selected from the group consisting of dimethacrylate, UDMA), acryloyl morpholine, and triethylene glycol dimethacrylate (TEGDMA) may be used.

The content of the photocurable monomer may be 10 to 35 parts by weight, or 15 to 30 parts by weight based on 100 parts by weight of the slurry composition.

In the present invention, the diluent may hold the curing shrinkage that occurs during curing, and may be used to lower the viscosity of the slurry composition. The diluent does not react upon curing. In the present invention, a more uniform highly filled slurry composition can be prepared by using a diluent.

In the present invention, camphor may be used as such a diluent. In general, camphor is used as a freezing medium, but in the present invention, the camphor serves as a diluent for lowering the viscosity of the slurry composition.

The content of the diluent may be 5 to 20 parts by weight, or 10 to 15 parts by weight based on 100 parts by weight of the slurry composition. In addition, the weight ratio of the photocurable monomer and the diluent may be 5 to 7:4. In the above range, the photocurable monomer is not supersaturated and the photocurable monomer can be dissolved in the diluent as much as possible, and a lower viscosity can be imparted.

In the present invention, the dispersant may be used to facilitate dispersion of the high content of the ceramic powder.

The type of the dispersant is not particularly limited, and for example, an alkylammonium salt copolymer compound, a polyester/polyether-based compound, a copolymer containing a phosphoric acid group, and a copolymer having an amine group. One or more selected from the group consisting of may be used.

The content of the dispersant may be 1 to 5 parts by weight, or 2 to 4 parts by weight based on 100 parts by weight of the slurry composition. A uniform slurry composition can be prepared in the above range.

In addition, in the present invention, the photocurable initiator polymerizes the photocurable monomer by forming free radicals by UV in a specific wavelength band that is selectively controlled.

The type of the photocuring initiator is not particularly limited, and for example, phenylbis(2,4,6-trimethyl benzoylphosphine oxide) (Phenylbis(2,4,6-trimethyl benzoylphosphine oxide), PPO), phenylbis (2,4,6-trimethyl benzoylphosphine oxide) (Phenylbis (2, 4, 6-trimethyl benzoylphosphine oxide), PPO), 1-hydroxy-cyclohexyl-phenyl-ketone (1-Hydroxy-cyclohexyl-phenyl- ketone), 2-hydroxy-2-methyl-1-phenyl-1-propanone (2-Hydroxy-2-methyl-1-phenyl-1-propanone), 2-hydroxy-1-[4- (2) -Hydroxyethoxy)phenyl]-2-methyl-1-propanone (2-Hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone), methylbenzoylformate (Methylbenzoylformate) ), oxy-phenyl-acetic acid-2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester (oxy-phenyl-acetic acid -2-[2 oxo-2phenyl-acetoxy-ethoxy]-ethyl ester), oxy-phenyl-acetic acid-2-[2-hydroxy-ethoxy]-ethyl ester (oxy-phenyl-acetic acid-2-[2-hydroxy-ethoxy]-ethyl ester), alpha-dimethoxy- alpha-dimethoxy-alpha-phenylacetophenone, 2-benzyl-2-(dimethylamino)1-[4-(4-morpholinyl) phenyl]-1-butanone (2-Benzyl-2 -(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone), 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1 -propanone (2-Methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone) and diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide (Diphenyl) (2 One or more selected from the group consisting of ,4,6-trimethylbenzoyl)-phosphine oxide) may be used.

The content of the photocuring initiator may be 0.1 to 1 parts by weight, or 0.2 to 0.7 parts by weight based on 100 parts by weight of the slurry composition. In addition, the content of the photocuring initiator may be 1 to 5 parts by weight or 1 to 3 parts by weight based on 100 parts by weight of the photocurable monomer. In the above range, photocuring of the photocurable monomer may be easily performed.

The photocurable ceramic slurry composition according to the present invention may further include a dye. Printing of a complex shape with high resolution can be performed using the dye. In the present invention, since 3D printing is performed through a bottom-up stacking method, there is a risk that ceramic particles present in the slurry composition may affect light dispersion and transmittance. In the present invention, such a phenomenon can be suppressed by using a dye.

The type of the dye is not particularly limited, for example, benzopurpurin benzopurpurin), bromophenol blue (Bromophenol blue), indocyanine green (Indocyanine green), Alcian blue (Alcian blue) or oil red o ( Oil Red O) can be used.

The content of the dye may be 0.01 to 0.5 parts by weight, or 0.005 to 0.2 parts by weight based on 100 parts by weight of the slurry composition. In addition, the content of the dye may be 0.005 to 0.5 parts by weight based on 100 parts by weight of the photocurable monomer. In the above range, high-resolution complex shape printing can be performed. As the content increases, the ability to implement details increases, while the curing depth decreases, so it is preferable to adjust it within the above range.

In the present invention, the slurry composition may be prepared by mixing the above-mentioned components, that is, ceramic powder, photocurable monomer, diluent, dispersant, photocurable initiator and dye. The mixing method may be performed according to a general method in the art.

When the viscosity of the ceramic slurry increases, the ceramic structure is manufactured thicker than the design by light scattering, and the clogging phenomenon in which the remaining slurry is not removed and pores are clogged may occur. In order to minimize this and to realize the smallest size pores (the gap between the surfaces forming the gyroid) that can be removed from the residual slurry, the ceramic slurry composition is preferably 30 to 39 vol%.

Accordingly, the slurry composition of the present invention can maintain a viscosity of 0.5 Pa·s or less or 0.3 Pa·s or less while including a high content of ceramic powder. Accordingly, it is possible to manufacture a ceramic molded body and a structure having a more precise and various gyroid structure.

In addition, the temperature of the slurry composition of the present invention may be 10 to 70 ℃ or 15 to 50 ℃. Since the diluent used in the present invention has volatility, it is possible to prevent volatilization of the diluent to have the above temperature range.

In addition, the present invention comprises the steps of filling the above-described photo-curable ceramic slurry composition in a container (vat);

forming a ceramic molding layer by raising a build plate by a programmed thickness from the lower surface of the container, and curing the photo-curable ceramic slurry composition into a programmed shape by ultraviolet rays irradiated from the bottom of the container; and

The raising of the build plate and the formation of the ceramic molding layer by ultraviolet rays are repeatedly performed to form a ceramic molding body.

In the present invention, the shape of the molded body can be maintained while having a high ceramic content by using the above-described photocurable ceramic slurry composition, and the physical properties of the molded body can be controlled.

At this time, since the diluent in the slurry composition has volatility, printing may be performed at 10 to 70°C or 15 to 50°C.

In the present invention, it is possible to provide a high-filling photocurable ceramic-based 3D printing technology applicable to a 3D printer for vaporization through the fusion of computer-controlled 3D printing technology and photocurable molding technology.

In one embodiment, according to the present invention, a ceramic molded body may be manufactured using a vapor-soluted bottom-up stacking 3D printer. 3D printing technology based on photocurable material selectively photocures a liquid photocurable resin as much as a preset area and laminates it layer by layer. Currently, research on manufacturing ceramic compacts using this technology has a very low level of technological maturity compared to other 3D printing technologies. In addition, due to the limitation of the printable ceramic viscosity, the requirement to control various parameters such as the curing depth and the position of the build plate, ceramic slurry printing is applied to top-down and tape casting. (tape casting) is used.

In the present invention, by solving this problem, a low-viscosity photo-curable ceramic slurry composition was prepared, and a ceramic molded body can be manufactured by using the slurry composition in a bottom-up lamination method. By applying the bottom-up lamination method, the manufacturing time increases according to the height of the molded body in the existing photocurable ceramic printing technology (ie, top-down and tape casting) and unreacted solution in the molded body after curing reaction It is possible to overcome limitations such as removal. In addition, it is possible to reduce the manufacturing time and cost, and reduce the gap between the walls in the structure of the microporous molded body. In addition, there is no need for a separate slurry composition supply system through the application of the bottom-up lamination method.

That is, in the present invention, since the ceramic slurry has a very low viscosity, it is possible to print in a 3D printer of a bottom-up lamination method for vaporization that mainly prints a polymer resin.

In the present invention, step (S1) is a step of filling the photo-curable ceramic slurry composition in a container (vat).

The shape of the container is not particularly limited as long as it can be filled with the photo-curable ceramic slurry composition. The material of the lower surface of the container may be formed so that ultraviolet rays irradiated from the lower part of the container are transmitted.

In one embodiment, the container has a build plate therein. The build plate moves down when the container is filled with the slurry composition and rises from the bottom according to the thickness of the programmed shaping layer (eg 20-100 μm). Thus, the slurry composition in the gap is selectively cured by the projector beam. That is, the slurry composition may be photocured on the surface of the build plate to form a molding layer. The build plate is then raised and the slurry is refilled during the rise time. A molding layer may be laminated through the movement of the build plate upward to manufacture a ceramic molded body.

In the present invention, step (S2) is a process in which the build plate rises by a programmed thickness from the bottom of the container, and the photo-curable ceramic slurry composition is cured into a programmed shape by ultraviolet rays irradiated from the bottom of the container to form a ceramic molding layer. is a step

In the present invention, 3D printing can print 3D drawing data using a printer according to a program designed in advance by a computer.

Specifically, the build plate is raised by the programmed thickness on the lower surface (bottom) of the container, and the slurry composition present on the lower surface of the build plate, that is, the slurry composition present between the lower surface of the build plate and the container bottom, is Depending on the shape, it is completely or partially cured to form a ceramic molding layer. In the present invention, since the molding layer is formed by a bottom-up stacking method, a separate feeding part is not required. In addition, when the slurry composition contains a dye, it is possible to print complex shapes with high resolution.

In one embodiment, the thickness of the ceramic molding layer may be 20 to 100 μm or 20 to 70 μm.

In one embodiment, the slurry composition may be photocured by ultraviolet rays irradiated from the bottom of the container. The ultraviolet irradiation device may be separately located at the bottom of the container, and ultraviolet irradiation may be performed by a UV beam or the like.

The intensity of the irradiated ultraviolet rays may be 1 to 5 W.

In addition, in the present invention, step (S3) is a step of forming a ceramic molded body by repeatedly performing the rising of the build plate and the formation of the ceramic molding layer by ultraviolet rays.

When the ceramic molding layer is formed in step S2, the build plate rises again by the programmed thickness. When the build plate rises, the ceramic slurry is filled again as much as the area cured in step (S2), and by curing it, the molding layer is laminated on the slurry molding layer. That is, in the present invention, an autonomous feeding system can be implemented.

In one embodiment, the photocuring time is that the ceramic molding layer is completely cured and in order to bond with the previously cured upper layer, the bonding site of the layer during photocuring may be cured a little deeper than the thickness of the previously programmed layer. can be adjusted appropriately. This allows the cured layer to overlap the top layer. If the curing time is short, the bonding force with the bottom of the container may be higher due to the characteristics of the bottom-up printer, and there is a fear that the bonding between the molding layers is very weak.

In the present invention, it is possible to manufacture a ceramic molded body having a programmed shape by repeatedly performing the raising of the build plate and the formation of the ceramic molding layer by ultraviolet rays.

In particular, according to the present invention, a ceramic molded body having various structures and pore structures can be manufactured by controlling the thickness of the molding layers and the intensity of the UV beam.

In one embodiment, a process of separating the manufactured ceramic compact from the build plate may be additionally performed.

In the present invention, the step of manufacturing a ceramic structure by heat-treating the ceramic compact may be additionally performed.

The heat treatment may be performed through two heat treatment processes of the first heat treatment and the second heat treatment (sintering).

In the first heat treatment, the polymer and the dispersant inside the photocured ceramic molded body may be removed. The first heat treatment may be performed at 80 to 700° C., or 100 to 600° C. for 2 to 15 hours, or 4 to 8 hours. In addition, by performing heat treatment while increasing the temperature step by step, it is possible to more easily remove impurities. The secondary heat treatment (sintering) can densify the ceramic wall. Through the secondary heat treatment, the adhesion between the ceramic walls may be improved. The secondary heat treatment may be performed at 1000 to 1500° C. for 1 minute to 5 hours. If the secondary heat treatment temperature is too high or the time is long, there is a risk that the chemical composition of the ceramic structure is changed.

The ceramic structure may be expressed as a gyroid structure. Gyroid refers to a porous three-dimensional nanostructure, and is a biomimetic structure advantageous for use as a bone substitute. The gyroid structure has pores stretched in the uniaxial direction, and thus may have excellent compressive strength of 3 MPa or more or 10 MPa or more.

The wall thickness of the prepared ceramic structure may be 180 μm to 300 μm or 200 μm to 290 μm, and when the z-axis elongation of the structure is 15 to 65%, porosity of 70 to 80%, small pores (that is, the ceramic wall The distance between ceramic walls was 800 μm to 1600 μm or 900 μm to 1400 μm). At this time, when the elongation is less than 15%, it is difficult to realize a desired thin wall, and when the elongation is more than 65%, there is a problem such as clogging of pores due to the broadening of the ceramic due to scattering of light.

The present invention can be applied to ceramic-based 3D printing technology by optimizing the type and content of the photocurable monomer, ceramic powder, diluent, dispersant, and photocuring initiator, and can provide a low-viscosity photocurable ceramic slurry composition. In particular, it is a ceramic 3D printing technology for designing a pore structure that can control the pore structure of a bioceramic scaffold for bone tissue regeneration and enhance mechanical strength and its manufacturing, and is a technique for three-dimensionally connected two independent pores (between ceramic walls). It is intended to apply a gyroid structure having a distance between ceramic walls structure to a ceramic scaffold. In particular, in order to increase the strength of the scaffold, elongation in the uniaxial direction rather than the conventional uniform gyroid structure is used. We designed a ceramic scaffold with a unique structure and optimized the process of photo-curing-based ceramic 3D printing technology (digital light processing, DLP) for manufacturing it, through which very thin ceramic walls and small It is possible to manufacture a porous ceramic scaffold having pores, so it has high porosity and high strength, and at the same time, the strength can be increased by about 1.5 to 3 times depending on the design of the pore structure, and its control is also possible.

In particular, the present invention has a high porosity and high mechanical strength by using a gyroid structure that has a similar shape to a living body and is advantageous for the differentiation and proliferation of bone cells, so that the mechanical strength of other porous structures used as an existing bone substitute is weak. compensates for the shortcomings.

In the present invention, so that the gyroid structure has a very thin strut thickness and small pores; It is possible to prepare a ceramic molded body and a structure having a gyroid structure with improved strength through pore structure control by using the low-viscosity, photo-curable ceramic slime composition at the same time as setting.

In addition, the DLP 3D printing technology of the bottom-up lamination method of the present invention has a structure in which the slurry is poured into the vat compared to the existing traditional top-down lamination method, so that automatic Ceramic slurry can be supplied. Thereby, a separate feeding system is not required and the process can be simplified. In particular, in the bottom-up stacking method, the amount of wasted photo-curable ceramic slurry composition is very small, so that material cost can be reduced. In addition, the mechanical strength of the porous body is increased by stretching the pores of the porous gyroid structure in the uniaxial direction using a vapor-solute DLP printer. In particular, by stretching the gyroid structure in the z-axis direction, a ceramic molded body having a gyroid structure having a very thin strut thickness and small pores can be manufactured using a bottom-up stacking printer.

The ceramic molded body having a biological gyroid structure according to the present invention is not only a gyroid structure having a bone-like shape, but also a porous scaffold stretched in the uniaxial direction. is promoted In addition, since the strength can be adjusted according to the design of the pore structure, it is possible to manufacture high-quality ceramic materials having various structures and shapes as well as artificial bones and scaffolds for bone tissue regeneration, and various industrial fields (structure, environment, energy, etc.) ) is applicable to

1 shows a schematic diagram of the modified gyroid structure used in this experiment and measurement values accordingly [Distance between walls means actual pores, and length and width, which are interconnection sizes, are shown when the gyroid unitcell is viewed from the front. It means the z-axis and x-axis length of the pore, not the actual pore size].
2 shows the results of the ceramic molded body, and shows measured values accordingly.
3 is an image obtained by measuring a cross-section of the ceramic molded body prepared in the schematic diagram of FIG. 1 under an optical microscope.
4 shows the TGA results of the ceramic molded body, and degreasing conditions were established based thereon.
5 shows the results after sintering of the ceramic compact, and shows measured values accordingly.
6 is a SEM measurement of the upper surface of the ceramic compact.
7 is a SEM measurement of the fracture surface of the ceramic molded body.
8 is a measurement of the compressive strength of the ceramic compact.
9 is a measurement of the inner appearance of the ceramic molded body through μ-CT.
10 is a measurement of the ceramic wall thickness according to the ceramic content.

Advantages and features of the present invention, and methods of achieving them, will become apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

Example

Preparation Example 1: Preparation of photocurable slurry composition

A photocurable slurry composition having the composition and content (g) of Table 1 was prepared.

The photocurable slurry composition was prepared at room temperature (25° C.).

Specifically, a mixture was prepared by mixing a photocurable monomer and a diluent, and then ceramic powder (35 vol%) and a dispersant (about 5 wt% relative to the ceramic powder) were added and mixed using a shear mixer for 40 minutes. In addition, inert dye and photocuring initiator were added to realize high resolution and mixed using a shear mixer for 10 minutes. Through this, a photo-curable low-viscosity (about 0.120 Pa·s) ceramic slurry composition (35 vol% ceramic slurry composition) for 3D printing that was highly uniformly complexed was prepared.

division photocurable monomer diluent ceramic powder dispersant photocuring initiator dyes HDDA Camphor BCP BYK-2001 PPO oil Red O density
(g/cm ³ ) 1.01 0.99 3.14 1.03 1.17 - Content (g) 18 12 55.24 2.76 0.27 0.005

- HDDA: 1,6 Hexanediol diacrylate (Sigma Aldrich, Germany), CAS#: 13048-33-4

- Camphor: Camphor (96%) (Sigma Aldrich, Germany), CAS#: 76-22-2

- Biphasic calcium phosphate (BCP): BCP powder with an average particle size of 0.5 to 0.8 μm composed of about 60 wt% of hydroxyphosphite (HA) and 40 wt% of triphosphate (TCP) (Sun Medical, Korea); Marked as CaP (calcium phosphate) on the drawing.

- BYK-2001 (BYK USA Inc, Germany)

- PPO: Phenylbis (2, 4, 6-trimethyl benzoylphosphine oxide) (Sigma Aldrich, Germany)

- Oil Red O (Sigma Aldrich, Germany) CAS#:1320-06-5 [1-(2,5-dimethyl-4-(2,5-dimethylphenyl)phenyldiazinyl)azonaphthalen-2-ol]

Preparation Example 2: Preparation of a ceramic molded body using a photocurable slurry composition

A ceramic molded body was prepared using the photocurable ceramic slurry composition prepared in Preparation Example 1.

Specifically, the photo-curable ceramic slurry composition prepared in Preparation Example was poured into a vapor-solute bottom-up lamination type printer's vat. After the build plate was raised by a programmed thickness (25 μm) on the lower surface of the container, a ceramic molding layer was formed by partial photo-curing (2.5 seconds curing, UV intensity 1.12 W) by a beam of a beam projector on the lower surface. Formation and photocuring of such a ceramic molding layer was performed in connection with the elevation of the build plate.

Experimental Example 1: Deformation of the gyroid structure

In the present invention, FIG. 1 is a schematic diagram of a gyroid structure made through a computer program, and shows a schematic diagram of the deformed gyroid structure, the size of the pores, the thickness of the strut, and the spacing between the struts. It can be seen that as the gyroid structure is stretched in the uniaxial direction, the length of the pores increases and the width decreases, and the thickness of the struts becomes thinner and the gap becomes narrower. Using the Magics computer program, the thickness of the gyroid unit cell was increased to 140 μm, which was increased by 120, 140, and 160 % in the z-axis direction and decreased by 20, 40, and 60 % in the x and y-axis directions. Each cell is prepared. As the ratio increases and decreases, the thickness of each unit cell decreases from 140 μm to 115, 100, and 85 μm, and the pore size decreases from 2350 μm to 1965, 1680, and 1475 μm. Using the 3D Max program, unit cells were combined and stacked layer by layer to form a cylindrical shape with a diameter of 1.5 cm and a height of 1.8 cm.

FIG. 2 of the present invention shows four types of scaffolds (0, 20, 40, 60%) manufactured by increasing the gyroid structure and changing the thickness and spacing between the struts by using a 35 vol% ceramic slurry. It is a microscopic image and the measurement result. In order to apply the 0, 20, 40, 60% gyroid scaffold file designed in FIG. 1 to the vaporized DLP equipment, it is converted into g-code using a conversion program and then 35 vol% ceramic slurry with low viscosity to print using The printed scaffolds were washed with ethanol using sonication, dried at room temperature, and then freeze-dried for 24 hours.

FIG. 2 is a result of printing based on FIG. 1 , measuring the upper end of the scaffold using an optical microscope image and SEM. It can be seen that the design value and the actual printing value are different (the actual printed wall is thicker) due to the broadening phenomenon that occurs during photocuring. As the ratio of stretching the gyroid in the uniaxial direction increases, the strut thickness of the design becomes thinner, but the measurement results show similar values. This is because broadening is more severe. As a slurry with a high ceramic content is used, light scattering occurs more severely, and the design is thicker than the design. After printing, the residual slurry is not removed and clogging may occur that clogs pores. A modified gyroid molded body having a pore size of about 1171 μm with a minimum strut thickness of about 308 μm, which is the minimum strut thickness that can be realized when printing using a 35 vol% ceramic slurry, was prepared. .

FIG. 3 is an optical microscope image of a cross-section of a ceramic molded body prepared in the schematic diagram of FIG. 1 with a stacking thickness of 25 μm using a 35 vol% ceramic slurry. It can be seen that as the ratio of elonagtion of the gyroid unit cell in the uniaxial direction increases, the distance between the surfaces constituting the gyroid becomes narrower. In addition, as shown in the cross-sectional photo, it can be confirmed that the shape of the cross-sectional pores formed in the x- and z-axis directions is also narrowed in the x-axis direction and stretched in the z-axis direction.

Experimental Example 2: Measurement of physical properties of ceramic compacts

A ceramic structure was printed using a 35 vol% ceramic slurry with a vaporized bottom-up type 3D printer. This was washed with ethanol using sonication, and then dried at room temperature. After TGA (Thermogravimetric analysis) was performed with the dried ceramic structure, the degreasing process and the sintering schedule of the specimen were established through this. 4 shows the TGA result and the sintering schedule of the ceramic structure. The degreasing process was carried out based on two points (365 ℃ and 415 ℃) with a large change in weight. The temperature was slowly raised to each point at a rate of 1 °C/min, and the dwelling time was designated for 2 hours each. In addition, in order to suppress the rapid growth of the grain size of the ceramic, pre-sintering was performed at 600 °C, and the final sintering temperature was 1200 °C for 3 hours.

5 is an image obtained by confirming the appearance of the ceramic compact after sintering in this way with an optical microscope, and a value obtained by measuring the thickness of the struts and the spacing between the struts by SEM. It can be seen that the laminated surface was sintered well while maintaining the structure of the molded body without layer separation and defects, and it was confirmed that 0, 20, 40, and 60% were all shrunk at a similar rate. The minimum thickness is about 234 μm, and it can be seen that the pores (the gap between the gyroid face and the face, the gap between the walls) are manufactured at a small level of 941 μm.

6 is a view showing the upper end of each group of ceramic compacts sintered at 1200° C. using SEM. It can be seen that as the ratio of elongation of the gyroid in the axial direction increases, the thickness of the strut becomes thinner and the spacing between the struts also becomes thinner.

Experimental Example 3: Measurement of densification of ceramic compacts

Densification of the ceramic compact prepared with the ceramic slurry of 35 vol% was measured for the ceramic content in the slurry composition. The fracture surface of the prepared ceramic molded body was measured at high magnifications of 1000 times and 4000 times using SEM.

7 is a measurement of densification of a ceramic compact sintered at 1200° C. using SEM. Since the ceramic slurry of 35 vol% was used, it can be confirmed that there are many residual pores and the density is low.

Experimental Example 4: Measurement of Porosity and Strength of Ceramic Formed Body

The porosity of the ceramic formed body according to the elongation of the gyroid prepared in Preparation Example was measured. The porosity of the ceramic molded body has Archimedes, a method of measuring using mass and volume, and a method of measuring using μ-CT. In this experiment, the porosity was measured using μ-CT.

Specifically, by using the photocurable ceramic slurry composition prepared in Preparation Example 1, scaffolds having the porosity shown in Table 2 of the following 4 scaffolds according to the elongation of the gyroid were prepared. Then, compressive strength and physical properties were evaluated for the scaffold.

Table 2 below shows the results of measuring the porosity according to the elongation of the gyroid. As the ratio of stretching the gyroid in the uniaxial direction increased, the porosity decreased, which can be explained by the decrease due to broadening in which the ceramic slurry appears wider than the design during photocuring due to scattering of light.

In the present invention, FIG. 8 is a result of evaluating the mechanical strength of the manufactured ceramic compact. The test was conducted with a sintered compact, and paraffin wax was applied to the upper and lower parts of the compact to level the compressive strength. A compression test was performed perpendicularly to the laminated surface of the molded article at a speed of 1 mm/min, and 8 measurements were taken for each group (0, 20, 40, 60%) to obtain an average value. As the elongation ratio in the uniaxial direction increases, the compressive strength increases about three times from a minimum of about 3.75 MPa to a maximum of about 11.47 MPa, and it can be seen that the mechanical strength can be controlled according to the design of the pore structure. Also, FIG. 9 is an image confirming the inside of the molded body by μ-CT. Although the strut spacing was very narrow and the size of the pores was small, it was confirmed that the struts were well manufactured without structural defects and clogging.

Therefore, a complex-shaped ceramic structure having a wall of about 190 to 300 μm was manufactured using the bottom-up DLP equipment, and the residual slurry removal was difficult even though the pore size was very small by using a ceramic slurry of low viscosity. made it easy

In order to compensate for the weak mechanical strength of the porous body, a gyroid structure in which pores are uniaxially tensioned was prepared.

Experimental Example 5: Measurement of broadening according to ceramic content

The physical properties of the ceramic compact produced according to the content of the ceramic powder were measured. A ceramic compact was prepared by the method of Preparation Example except that the ceramic content in the slurry composition was adjusted to 40 vol%.

As the ceramic content (vol%) increases, an experiment on broadening, which is a phenomenon in which the ceramic is cured more widely than the design when photocured, was conducted. This experiment was conducted to support the reason for using 35 vol%, and after printing cylinders with diameters of 171, 228, and 285 μm of the same design using ceramic slurry of 35 vol% and 40 vol%, design by SEM Contrast increase rate was measured.

10 is a comparison of the results of broadening when the ceramic content is 35 vol% and 40 vol%, and is the result of printing when the initial design is 171, 228, 285 μm.

As can be seen from the graph, a value greater than 35 vol% was measured at 40 vol%.

The thickness of the thinnest ceramic wall (elongation 60%) in the current experiment is 85 µm by design, so it is not shown on the graph, but in terms of the trend, using a 35 vol% slurry is better than using a 40 vol% slurry. It can be expected that it will be printed thinly.

Therefore, in order to realize the goal of realizing a thin wall, a low-viscosity slurry of 35 vol% was used.

Claims (13)

Ceramic powder, a photocurable monomer, including camphor as a diluent, a dispersant and a photocuring initiator,
In the photocurable ceramic slurry composition, the volume of the ceramic powder is 30 to 39 vol%, the strength is enhanced through control of the pore structure, and the photocurable ceramic slurry composition for manufacturing a ceramic scaffold having a gyroid structure elongated in the uniaxial direction.
The method of claim 1,
Ceramic powder is hydroxyapatite (HA), fluorine-containing hydroxyapatite (FHA), tricalciumphosphate (TCP), BCP (biphasic calcium phosphate), alumina, zirconia, silica (silica) and a photocurable ceramic slurry composition comprising at least one selected from the group consisting of bioglass.
The method of claim 1,
The photocurable monomer is 1,6-hexanediol diacrylate (HDDA), urethane dimethacrylate (UDMA), acryloyl morpholine (Acryloyl morpholine) and triethylene glycol diacrylate A photocurable ceramic slurry composition comprising at least one selected from the group consisting of methacrylate (Triethylene glycol dimethacrylate, TEGDMA).
The method of claim 1,
A photo-curable ceramic slurry composition wherein the weight ratio of the photo-curable monomer and the diluent is 5 to 7: 4.
The method of claim 1,
The dispersant comprises at least one selected from the group consisting of an alkylammonium salt copolymer compound, a polyester/polyether-based compound, a copolymer containing a phosphoric acid group, and a copolymer having an amine group. Martian Ceramic Slurry Composition.
The method of claim 1,
The photocuring initiator is phenylbis(2,4,6-trimethyl benzoylphosphine oxide) (PPO), 1-hydroxy-cyclohexyl-pennyl-ketone, 2-hydroxy-2-methyl-1-phenyl-1- Propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methylbenzoylformate, oxy-phenyl-acetic acid-2-[2-oxo -2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic acid-2-[2-hydroxy-ethoxy]-ethyl ester, alpha-dimethoxy-alpha-phenylacetophenone, 2-benzyl -2-(dimethylamino)1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholyl) A photocurable ceramic slurry composition comprising at least one selected from the group consisting of nyl)-1-propanone and diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide.
The method of claim 1,
It further contains a dye,
The dye is benzopurpurin benzopurpurin), bromophenol blue (Bromophenol blue), indocyanine green (Indocyanine green), Alcian blue (Alcian blue) or oil red O (Oil Red O) photocurable ceramic slurry composition.
The method of claim 1,
The temperature of the photo-curable ceramic slurry composition is 10 ℃ to 70 ℃ photo-curable ceramic slurry composition.
filling a vat with the photocurable ceramic slurry composition according to claim 1;
forming a ceramic molding layer by raising a build plate by a programmed thickness from the bottom of the container, and curing the photocurable ceramic slurry composition into a programmed shape by ultraviolet rays irradiated from the bottom of the container; and
The method of manufacturing a ceramic molded body comprising a; the step of forming the ceramic molded body by repeatedly performing the rising of the build plate and the formation of the ceramic molding layer by ultraviolet rays.
10. The method of claim 9,
A method for producing a ceramic compact, wherein the wall thickness of the ceramic compact is 180 µm to 300 µm, and the spacing between the ceramic walls is 800 µm to 1600 µm.
10. The method of claim 9,
The intensity of the irradiated ultraviolet light is 1 to 5 W method of manufacturing a ceramic molded body.
10. The method of claim 9,
Method for producing a ceramic compact further comprising the step of heat-treating the ceramic compact.
13. The method of claim 12,
Heat treatment is a method of manufacturing a ceramic molded body to perform a primary heat treatment for 2 to 15 hours at 80 ° C. to 700 ° C., and then performing a secondary heat treatment (sintering) at 1000 ° C. to 1500 ° C. for 1 to 5 hours.

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