Low-temperature Deposition Manufacturing Research Articles

Towards the Clinical Translation of 3D PLGA/β-TCP/Mg Composite Scaffold for Cranial Bone Regeneration.

Recent years have witnessed the rapid development of 3D porous scaffolds with excellent biocompatibility, tunable porosity, and pore interconnectivity, sufficient mechanical strength, controlled biodegradability, and favorable osteogenesis for improved results in cranioplasty. However, clinical translation of these scaffolds has lagged far behind, mainly because of the absence of a series of biological evaluations. Herein, we designed and fabricated a composite 3D porous scaffold composed of poly (lactic-co-glycolic) acid (PLGA), β-tricalcium phosphate (β-TCP), and Mg using the low-temperature deposition manufacturing (LDM) technique. The LDM-engineered scaffolds possessed highly porous and interconnected microstructures with a porosity of 63%. Meanwhile, the scaffolds exhibited mechanical properties close to that of cancellous bone, as confirmed by the compression tests. It was also found that the original composition of scaffolds could be maintained throughout the fabrication process. Particularly, two important biologic evaluations designed for non-active medical devices, i.e., local effects after implantation and subchronic systemic toxicity tests, were conducted to evaluate the local and systemic toxicity of the scaffolds. Additionally, the scaffolds exhibited significant higher mRNA levels of osteogenic genes compared to control scaffolds, as confirmed by an in vitro osteogenic differentiation test of MC3T3-E1 cells. Finally, we demonstrated the improved cranial bone regeneration performance of the scaffolds in a rabbit model. We envision that our investigation could pave the way for translating the LDM-engineered composite scaffolds into clinical products for cranial bone regeneration.

3D printed PLGA/MgO/PDA composite scaffold by low-temperature deposition manufacturing for bone tissue engineering applications

IntroductionBones are easily damaged. Biomimetic scaffolds are involved in tissue engineering. This study explored polydopamine (PDA)-coated poly lactic-co-glycolic acid (PLGA)-magnesium oxide (MgO) scaffold properties and its effects on bone marrow mesenchymal stem cells (BMSCs) osteogenic differentiation. MethodsPLGA/MgO scaffolds were prepared by low-temperature 3D printing technology and PDA coatings were prepared by immersion method. Scaffold structure was observed by scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS), fourier transform infrared spectrometer (FTIR). Scaffold hydrophilicity, compressive/elastic modulus, and degradation rates were analyzed by water contact angle measurement, mechanical tests, and simulated-body fluid immersion. Rat BMSCs were cultured in scaffold extract. Cell activity on days 1, 3, and 7 was detected by MTT. Cells were induced by osteogenic differentiation, followed by evaluation of alkaline phosphatase (ALP) activity on days 3, 7, and 14 of induction and Osteocalcin, Osteocalcin, and Collagen I expressions. ResultsThe prepared PLGA/MgO scaffolds had dense microparticles. With the increase of MgO contents, the hydrophilicity was enhanced, scaffold degradation rate was accelerated, magnesium ion release rate and scaffold extract pH value were increased, and cytotoxicity was less when magnesium mass ratio was less than 10%. Compared with other scaffolds, compressive and elastic modulus of PLGA/MgO (10%) scaffolds were increased; BMSCs incubated with PLGA/MgO (10%) scaffold extract had higher ALP activity and Osteocalcin, Osteopontin, and Collagen I expressions. PDA coating was prepared in PLGA/MgO (10%) scaffolds and the mechanical properties were not affected. PLGA/MgO (10%)/PDA scaffolds had better hydrophilicity and biocompatibility and promoted BMSC osteogenic differentiation. ConclusionLow-temperature 3D printing PLGA/MgO (10%)/PDA scaffolds had good hydrophilicity and biocompatibility, and were conducive to BMSC osteogenic differentiation.

Low-temperature deposition manufacturing technology: a novel 3D printing method for bone scaffolds.

The application of three-dimensional printing technology in the medical field has great potential for bone defect repair, especially personalized and biological repair. As a green manufacturing process that does not involve liquefication through heating, low-temperature deposition manufacturing (LDM) is a promising type of rapid prototyping manufacturing and has been widely used to fabricate scaffolds in bone tissue engineering. The scaffolds fabricated by LDM have a multi-scale controllable pore structure and interconnected micropores, which are beneficial for the repair of bone defects. At the same time, different types of cells or bioactive factor can be integrated into three-dimensional structural scaffolds through LDM. Herein, we introduced LDM technology and summarize its applications in bone tissue engineering. We divide the scaffolds into four categories according to the skeleton materials and discuss the performance and limitations of the scaffolds. The ideas presented in this review have prospects in the development and application of LDM scaffolds.

A Study of the Gelatin Low-Temperature Deposition Manufacturing Forming Process Based on Fluid Numerical Simulation.

Low-temperature deposition manufacturing has attracted much attention as a novel printing method, bringing new opportunities and directions for the development of biological 3D printing and complex-shaped food printing. In this article, we investigated the rheological and printing properties of gelatin solution and conducted numerical simulation and experimental research on the low-temperature extrusion process of gelatin solution. The velocity, local shear rate, viscosity, and pressure distribution of the material in the extrusion process were calculated using Comsol software. The effects of the initial temperature, inlet velocity, and print head diameter of the material on the flow field distribution and printing quality were explored. The results show that: (1) the fluidity and mechanical properties of gelatin solution vary with its concentration; (2) the initial temperature of material, inlet velocity, and print head diameter all have varying degrees of influence on the distribution of the flow field; (3) the concentration change of the material mainly affects the pressure distribution in the flow channel; (4) the greater the inlet velocity, the greater the velocity and shear rate in the flow field and the higher the temperature of the material in the outlet section; and (5) the higher the initial temperature of the gel, the lower the viscosity in the flow field. This article is of great reference value for the low-temperature 3D printing of colloidal materials that are difficult to form at room temperature.

Hierarchical porous ECM scaffolds incorporating GDF-5 fabricated by cryogenic 3D printing to promote articular cartilage regeneration

BackgroundIn recent years, there has been significant research progress on in situ articular cartilage (AC) tissue engineering with endogenous stem cells, which uses biological materials or bioactive factors to improve the regeneration microenvironment and recruit more endogenous stem cells from the joint cavity to the defect area to promote cartilage regeneration.MethodIn this study, we used ECM alone as a bioink in low-temperature deposition manufacturing (LDM) 3D printing and then successfully fabricated a hierarchical porous ECM scaffold incorporating GDF-5.ResultsComparative in vitro experiments showed that the 7% ECM scaffolds had the best biocompatibility. After the addition of GDF-5 protein, the ECM scaffolds significantly improved bone marrow mesenchymal stem cell (BMSC) migration and chondrogenic differentiation. Most importantly, the in vivo results showed that the ECM/GDF-5 scaffold significantly enhanced in situ cartilage repair.ConclusionIn conclusion, this study reports the construction of a new scaffold based on the concept of in situ regeneration, and we believe that our findings will provide a new treatment strategy for AC defect repair.

Hierarchical macro-microporous WPU-ECM scaffolds combined with Microfracture Promote in Situ Articular Cartilage Regeneration in Rabbits

Tissue engineering provides a promising avenue for treating cartilage defects. However, great challenges remain in the development of structurally and functionally optimized scaffolds for cartilage repair and regeneration. In this study, decellularized cartilage extracellular matrix (ECM) and waterborne polyurethane (WPU) were employed to construct WPU and WPU-ECM scaffolds by water-based 3D printing using low-temperature deposition manufacturing (LDM) system, which combines rapid deposition manufacturing with phase separation techniques. The scaffolds successfully achieved hierarchical macro‐microporous structures. After adding ECM, WPU scaffolds were markedly optimized in terms of porosity, hydrophilia and bioactive components. Moreover, the optimized WPU-ECM scaffolds were found to be more suitable for cell distribution, adhesion, and proliferation than the WPU scaffolds. Most importantly, the WPU-ECM scaffold could facilitate the production of glycosaminoglycan (GAG) and collagen and the upregulation of cartilage-specific genes. These results indicated that the WPU-ECM scaffold with hierarchical macro‐microporous structures could recreate a favorable microenvironment for cell adhesion, proliferation, differentiation, and ECM production. In vivo studies further revealed that the hierarchical macro‐microporous WPU-ECM scaffold combined with the microfracture procedure successfully regenerated hyaline cartilage in a rabbit model. Six months after implantation, the repaired cartilage showed a similar histological structure and mechanical performance to that of normal cartilage. In conclusion, the hierarchical macro‐microporous WPU-ECM scaffold may be a promising candidate for cartilage tissue engineering applications in the future.

Preparation and characterization of a three dimensional porous poly(lactic-co-glycolic acid)/mesoporous silica nanoparticles scaffold by low-temperature deposition manufacturing

In this study, we introduced mesoporous silica nanoparticles (MSNs) into poly(lactic-co-glycolic acid) (PLGA) to prepare a novel three dimensional (3D) porous scaffold by low-temperature deposition manufacturing (LDM). During the scaffolds preparing process, LDM managed to fabricate scaffolds with 3D geometry and desirable big pore structures but not damage the bioactivity of biomaterials. In the subsequent freeze-drying process, the as-fabricated scaffolds produced small pore structures due to the phase separation process. The scaffolds were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometer, hydrophilicity, porosity and mechanical test. The mean diameters of big pores were 445 ± 50 μm and 431 ± 32 μm, and those of small pores were 11 ± 3 μm and 8 ± 2 μm for PLGA and PLGA/MSNs scaffolds, respectively. Hydrophilicity examination revealed enhanced hydrophilicity of the composite scaffolds. Besides, the incorporation of MSNs also improves the mechanical property of the composites. Human bone marrow mesenchymal stem cells (hMSCs) were seeded on scaffolds for 3, 5, and 7 days. CCK-8 assay revealed that the introduction of MSNs improved cell proliferation. The adhesion and growth of cells on PLGA/MSNs scaffolds were enhanced over time during culturing period when compared to that on PLGA scaffolds. The results suggested that the 3D-printed PLGA/MSNs scaffolds are promising in cartilage tissue engineering.

Design, modeling and 3D printing of a personalized cervix tissue implant with protein release function

Cervical cancer induced by human papillomavirus (HPV) causes severe morbidity worldwide. Although cervical conization has been widely accepted as the most conventional surgery against cervical cancer, tissue defects and high recurrence rates have a significant negative impact on women’s mental and physical health. Herein we developed an implantable, personalized cervical implant with drug release function using 3D printing technology. The cervical implant was designed in cone-shape with hieratical porous structures according to the clinical data, 3D-printed using polyurethane by low-temperature deposition manufacturing (LDM), and finished by lyophilization. Anti-HPV protein was loaded into the porous structure under negative pressure afterwards. Elastic biomedical polyurethane and the porous structure ensured that these cervical implants were equipped with tailored mechanical properties comparable to physiological cervix tissue. Cytotoxicity and cytocompatibility tests indicated that these 3D-printed cervical implants supported cell adhesion and growth. More importantly, the cervical implants with regulated pores could help to quantitatively control the loading and release of anti-HPV protein to inhibit dissociative viruses near the cervix validly. As a result, the 3D-printed cervical implants in the present study showed considerable potential for use as functional tissue implants against HPV infection after cervical conization.

Low-Temperature Deposition Manufacturing: A Versatile Material Extrusion-Based 3D Printing Technology for Fabricating Hierarchically Porous Materials

Low-temperature deposition manufacturing (LTDM) is a technology that combines material extrusion-based 3D printing and thermally induced phase separation (TIPS) into one process. With this feature, both the merits of 3D printing and TIPS can be incorporated including complex geometries with tailorable ordered macroporous features facilitated by 3D printing and microporous/nanoporous features endowed by TIPS. These macroporous/microporous/nanoporous combined structures are important to some important applications such as tissue engineering scaffolds, porous electrodes for electrochemical energy storage, purification, and filtering applications. However, the unique advantages and potential applications of LTDM have not been fully recognized and exploited yet. In this review, we will discuss the origin, principle, advantages, processes, and machine setup of LTDM technology with an emphasis on its unique advantages in fabricating porous materials. Then, current applications of LTDM including porous tissue engineering scaffolds and emerging porous electrodes for electrochemical storage will be described. The versatility of LTDM including its capability of processing a wide range of materials, multimaterial and gradient structures, and core-shell structures will be introduced. Finally, we will conclude with a perspective and outlook on the future development and applications of LTDM technology.

Fabrication of 3D cryo-printed scaffolds using low-temperature deposition manufacturing for cartilage tissue engineering

Osteoarthritis is predicted to become the fourth leading cause of disability by 2020. Engineered scaffolds have shown promise in the field of cartilage tissue engineering. The primary aim of scaffolds is to mimic the architecture and mechanical properties of the native cartilage to promote successful regeneration. This study employs cryo-printing, an adaptation of low-temperature deposition manufacturing (LDM), which integrates 3D printing and directional freezing. A 3D printer was developed to allow direct printing onto a cold plate set at −40 °C. Scaffolds were fabricated using various concentrations of polycaprolactone (PCL) (6%, 8% and 10%), print-head temperatures (35 °C and 45 °C) and needle diameters (0.8, 0.6 and 0.3 mm). Adjusting these parameters influenced scaffold morphology and pore diameter. More specifically, scaffolds exhibited average pore diameters ranging from 3.597 ± 0.077 µm to 5.808 ± 0.213 µm between different polymer concentrations. Additionally, Young's modulus of scaffolds ranged between 0.76 MPa and 2.03 MPa in the 0–10% strain region, which is within the range expressed by the native cartilage. Ultimate tensile properties of scaffolds was found to correlate with polymer concentration and print-head temperature. Incremental Young's modulus was significantly reduced in the 10–20% strains compared to the 0–10% strains with the use of different print-head temperatures and needle diameters. Needle diameter had no influence on the mechanical properties of scaffolds. Overall, this study shows that cryo-printing allows the fabrication of scaffolds with highly reproducible pore diameters and mechanical properties that can be easily tuned by changing polymer concentration and print-head temperature.

Preparation and biocompatibility of diphasic magnetic nanocomposite scaffold

We describe the study of a new type of diphasic magnetic nanocomposite scaffold (PLGA/Col-I-PLGA/n-HA/Fe2O3) and its preparation using a novel low-temperature deposition manufacturing (LDM) technology. In order to study the biocompatibility of this scaffold, we evaluated and explored its feasibility as a scaffold for tissue engineering. Diphasic magnetic nanocomposite scaffolds (PLGA/Col-I-PLGA/n-HA/Fe2O3) were prepared using LDM technology. The mechanical properties of the scaffold were tested using an electronic testing machine, electron microscopy was utilized to observe the ultrastructure, and a medium (ethanol) immersion method was used to determine the porosity of the scaffold. The scaffold was co-cultured with bone mesenchymal stem cells (BMSCs) and was induced to differentiate. The biocompatibility of the scaffold was then tested. The mechanical test results of the diphasic magnetic nanocomposite scaffold demonstrated good mechanical properties. Electron microscopy studies revealed two layers of pore sizes each with a uniform distribution, with the upper cartilage pore size observed to be small while the middle continuous phase was found to be in a good integration. Pore size and porosity test results demonstrated a cartilage layer pore size of 186 μm, with a porosity measured to be 89.5%. The pore size and porosity of the bone layer were 394 μm and 86.1%, respectively. These properties met the design requirements of double layer scaffolds. Co-culture of the diphasic magnetic nanocomposite scaffold and bone mesenchymal stem cells (BMSCs) exhibited good proliferation of bone mesenchymal stem cells (BMSCs), and the scaffold was found to be able to promote differentiation of the differentiation-oriented cells. These results demonstrated a good biocompatibility of the diphasic magnetic nanocomposite scaffold. The diphasic magnetic nanocomposite scaffold (PLGA/Col-I-PLGA/n-HA/Fe2O3) was found to have suitable mechanical properties as well as cell compatibility. The measured pore size and porosity met the requirements for cell adhesion and cell growth, which matched more closely to that of the physiological structure of normal articular cartilage and subchondral bones. We expect this to represent new technology for improved repair of cartilage and subchondral bone lesions caused by osteoarthritis or trauma.

Experimental Study on 3D Chi - Hap Scaffolds for Thyroid Cartilage Repairing

Due to the limitation of self-repairing capability for cartilage injury, the construction of tissue engineering in vitro has been an ideal treatment to repair tissue injury. In this paper, hydroxyapatite (Hap) and chitosan (Chi) were selected to fabricate the scaffold through low temperature deposition manufacturing (LDM) technique. The scaffold was characterized with interconnected structure and high porosity, as well as lower toxicity to cells (TDC-5-EGPE). Animal experiment was performed, Twelve white New Zealand rabbits were randomly divided into two groups, the side of the thyroid cartilage was removed, Chi-HAP composite scaffold was implanted into the cartilage defect as the experimental group A. Group B was treated for thyroid cartilage defects without any treatment. After 10 weeks, hematoxylin-eosin (HE) staining and S-O staining were carried out on the injured tissues. The result showed that newborn chondrocytes were found in repaired areas for group A, and there are no new cells found for group B. Therefore, Chi-HAP composite scaffolds formed by LDM possess biological activity for repairing injury cartilage.

A 3D-Printed PLCL Scaffold Coated with Collagen Type I and Its Biocompatibility.

Scaffolds play an important role in tissue engineering and their structure and biocompatibility have great influence on cell behaviors. In this study, poly(l-lactide-co-ε-caprolactone) (PLCL) scaffolds were printed by a 3D printing technology, low-temperature deposition manufacturing (LDM), and then PLCL scaffolds were treated by alkali and coated with collagen type I (COLI). The scaffolds were characterized by scanning electron microscopy (SEM), porosity test, mechanical test, and infrared spectroscopy. The prepared PLCL and PLCL-COLI scaffolds had three-dimensional (3D) porous structure and they not only have macropores but also have micropores in the deposited lines. Although the mechanical property of PLCL-COLI was slightly lower than that of PLCL scaffold, the hydrophilicity of PLCL-COLI was significantly enhanced. Rabbit articular chondrocytes were extracted and were identified as chondrocytes by toluidine blue staining. To study the biocompatibility, the chondrocytes were seeded on scaffolds for 1, 3, 5, 7, and 10 days. MTT assay showed that the proliferation of chondrocytes on PLCL-COLI scaffold was better than that on PLCL scaffold. And the morphology of cells on PLCL-COLI after 1-day culture was much better than that on PLCL. This 3D-printed PLCL scaffold coated with COLI shows a great potential application in tissue engineering.

Biomimetic design and fabrication of multilayered osteochondral scaffolds by low-temperature deposition manufacturing and thermal-induced phase-separation techniques

Integrative osteochondral repair is a useful strategy for cartilage-defect repair. To mimic the microenvironment, it is necessary that scaffolds effectively mimic the extracellular matrix of natural cartilage and subchondral bone. In this study, biomimetic osteochondral scaffolds containing an oriented cartilage layer, a compact layer, and a three-dimensional (3D)-printed core-sheath structured-bone layer were developed. The oriented cartilage layer was designed to mimic the structural and material characteristics of native cartilage tissue and was fabricated with cartilage matrix-chitosan materials, using thermal-induced phase-separation technology. The 3D-printed core-sheath structured-bone layer was fabricated with poly(L-lactide-co-glycolide)/β-tricalcium phosphate-collagen materials by low-temperature deposition technology, using a specially designed core-sheath nozzle, and was designed to mimic the mechanical characteristics of subchondral bone and improve scaffold hydrophilicity. The compact layer was designed to mimic the calcified-layer structure of natural cartilage to ensure the presence of different suitable microenvironments for the regeneration of bone and cartilage. A dissolving-bonding process was developed to effectively combine the three parts together, after which the bone and cartilage scaffolds exhibited good mechanical properties and hydrophilicity. Additionally, goat autologous bone mesenchymal stem cells (BMSCs) were isolated and then seeded into the bone and cartilage layers, respectively, and following a 1 week culture in vitro, the BMSC-scaffold constructs were implanted into a goat articular-defect model. Our results indicated that the scaffolds exhibited good biocompatibility, and 24 weeks after implantation, the femoral condyle surface was relatively flat and consisted of a large quantity of hyaloid cartilage. Furthermore, histological staining revealed regenerated trabecular bone formed in the subchondral bone-defect area. These results provided a new method to fabricate biomimetic osteochondral scaffolds and demonstrated their effectiveness for future clinical applications in cartilage-defect repair.

3D Poly(Lactic-co-glycolic acid) Scaffolds for Treating Spinal Cord Injury.

In this paper, poly(lactic-co-glycolic acid) (PLGA) was used to fabricate spinal cord scaffolds using low temperature deposition manufacturing (LDM) technology. The PLGA scaffolds were characterized as having good porosity, hydrophilicity and considerable biodegradability. The effects of the PLGA scaffolds on cell proliferation and cytotoxicity were evaluated by culturing Schwann cells (SCs) on the surfaces of the scaffolds. The results showed that the SCs spread and proliferated well on the PLGA scaffolds. Histological assessment including Glia fibrillary acidic protein (GFAP) staining, Nissl staining, Luxol fast blue (LFB) staining and Bielschowsky silver staining showed that the spinal cord recoveries considerably improved with the PLGA scaffolds, indicating that the PLGA scaffolds exhibited potential for applications in the management of spinal cord injuries.

Design and Development of a Novel Frozen-Form Additive Manufacturing System for Tissue Engineering Applications

High-quality scaffolds play a vital role in tissue engineering. The frozen-form method (FFM) (also known as low-temperature deposition manufacturing) can be used to fabricate scaffolds from biomedical polymers. These scaffolds may have both macroporous and microporous characteristics and may incorporate bioactive compounds or biomolecules during the process. In addition, scaffolds produced at low temperatures can prevent the occurrence of thermal hydrolysis, thereby improving the mechanical properties of scaffolds. In fabricating high-quality (without deformation and collapse) bioscaffolds through the FFM, the most crucial requirement is the creation of a uniform low-temperature environment. This study developed a frozen-form additive manufacturing system that includes a uniform cryogenic device to generate the uniform distribution of a low-temperature environment over a local region to produce large scaffolds that will not deform and collapse. A large square scaffold block and a high aspect ratio tubular scaffold were fabricated to verify the efficiency of this system. Furthermore, this study employed a selective compliance assembly robot arm to traverse two-dimensional deposition paths, unlike the conventional Cartesian gantry system. This study investigated the challenges stemming from the use of such a device for scaffold production and suggests methods for resolving such issues.

Low-temperature deposition manufacturing: A novel and promising rapid prototyping technology for the fabrication of tissue-engineered scaffold

Developed in recent years, low-temperature deposition manufacturing (LDM) represents one of the most promising rapid prototyping technologies. It is not only based on rapid deposition manufacturing process but also combined with phase separation process. Besides the controlled macropore size, tissue-engineered scaffold fabricated by LDM has inter-connected micropores in the deposited lines. More importantly, it is a green manufacturing process that involves non-heating liquefying of materials. It has been employed to fabricate tissue-engineered scaffolds for bone, cartilage, blood vessel and nerve tissue regenerations. It is a promising technology in the fabrication of tissue-engineered scaffold similar to ideal scaffold and the design of complex organs. In the current paper, this novel LDM technology is introduced, and its control parameters, biomedical applications and challenges are included and discussed as well.

Preparation of an adipose-derived stem cell/fibrin–poly(d,l-lactic-co-glycolic acid) construct based on a rapid prototyping technique

Currently, large, thick, and complex tissue vascularization is one of the research focuses of tissue engineering. Numerous studies have proven that microvascular systems can be developed by cultivating endothelial cells in a hydrogel/scaffold structure. As the sources of adult endothelial cells are very limited and very easily degraded, it is better to induce stem cells into endothelial cells. In this article, a grid poly(d,l-lactic- co-glycolic acid) structure with defined internal channels was fabricated using a low-temperature deposition manufacturing technique under computer direction. In a fibrinogen mixture, an aqueous adipose-derived stem cell fibrinogen mixture was incorporated into the internal walls of the poly(d,l-lactic- co-glycolic acid) scaffold and stabilized with thrombin solution. After several days of in vitro culture, the adipose-derived stem cells immobilized in the fibrin hydrogel were induced into endothelial-like cells with endothelial growth factor and basic fibroblast growth factor. Morphological and biological properties of the composite cell/fibrin–poly(d,l-lactic- co-glycolic acid) construct were characterized.

Pneumatic feeding system for low-temperature deposition manufacturing based on system identification

Low-temperature deposition manufacturing (LDM), which is based on the principles of additive manufacturing, can preserve biological activity by fabricating custom pore-sized three-dimensional (3D) scaffolds. Appropriate extrusion velocity is significant to the fabrication of ideal macro-porous structures, which prevents collapse between layers and over-accumulation of material. This paper: proposes a new pneumatic feeding system consisting of an air source and valves; focuses on combinations of mathematical delay models of the first order and least squares identification; and describes the construction of a model of pressure and extrusion velocity by analysing the process of pneumatic material feeding. Our tests confirmed the time series used to adjust the desired pressure via opening and closing valves to change the feeding velocity using the parameters of our model. Furthermore, we verified that gelatin scaffolds could be formed by LDM, and over-accumulation and decrease overlap had been solved to some extent using our time series.

On-Line Control for the Pore Size of Bone Scaffold Based on LDM

The scaffold is a key part of the artificial regeneration osseous tissues. The ideal scaffold will have the ability to mimic the fully functional tissue, which can afford the fibrous form and complex function of the native ECM. Although Low-temperature deposition manufacturing is a promising method for fabricate tissue scaffold because scaffold can maintain a good performance of biomaterials in low temperature, the scaffold pore size can not be controlled according to demands. Therefore, the key factors that affect the pore size of bone scaffolds are firstly analyzed. Then the mechanism for on-line control is given. Finally, an automatic control system is proposed and some experimental results are given, which have demonstrated the effects of processing parameters on the Shaping of scaffold material.