Jatender Pal Singh, Pulak M. Pandey and Anita Kamra Verma
Scaffolds are essentially required to have open porous structure for facilitating bone to grow. They are generally placed on those bone defective/fractured sites which are more…
Abstract
Purpose
Scaffolds are essentially required to have open porous structure for facilitating bone to grow. They are generally placed on those bone defective/fractured sites which are more prone to compressive loading. Open porous structure lacks in strength in comparison to solid. Selective laser sintering (SLS) process is prominently used for fabrication of polymer/composite scaffolds. So, this paper aims to study for fabrication of three-dimensional open porous scaffolds with enhanced strength, process parameters of SLS of a biocompatible material are required to be optimized.
Design/methodology/approach
Regular open porous structures with suitable pore size as per computer-aided design models were fabricated using SLS. Polyamide (PA-2200) was used to fabricate the specimen/scaffold. To optimize the strength of the designed structure, response surface methodology was used to design the experiments. Specimens as per ASTM D695 were fabricated using SLS and compressive testing was carried out. Analysis of variance was done for estimating contribution of individual process parameters. Optimized process parameters were obtained using a trust region algorithm and correlated with experimental results. Accuracy of the fabricated specimen/scaffold was also assessed in terms of IT grades. In vitro cell culture on the fabricated structures confirmed the biocompatibility of polyamide (PA-2200).
Findings
Optimized process parameters for open cell process structures were obtained and confirmed experimentally. Laser power, hatch spacing and layer thickness have contributed more in the porous part’s strength than scan speed. The accuracy of the order of IT16 has been found for all functional dimensions. Cell growth and proliferation confirmed biocompatibility of polyamide (PA-2200) for scaffold applications.
Originality/value
This paper demonstrates the biocompatibility of PA-2200 for scaffold applications. The optimized process parameters of SLS process for open cell structure having pore size 1.2 × 1.2 mm2 with strut diameter of 1 mm have been obtained. The accuracy of the order of IT16 was obtained at the optimized process factors.
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Gaurav Tripathi and Pulak Mohan Pandey
Topologically ordered functionally graded composite (TOFGC) biodegradable materials are needed in the field of metallic degradable implants, as they degrade over a period of time…
Abstract
Purpose
Topologically ordered functionally graded composite (TOFGC) biodegradable materials are needed in the field of metallic degradable implants, as they degrade over a period of time avoiding the necessity of another surgery for implant removal. Also, their rate of degradation can be tailored to match the requirement of the patient. These biomaterials also have the functionality to assist bone growth and eliminate stress shielding in orthopaedic implants.
Design/methodology/approach
In this study, TOFGC biomaterials were developed for the first time using additive manufacturing, pressureless microwave sintering and casting methods, and their cytocompatibility, hemocompatibility and in vitro degradation evaluations were done. Also, pure dense iron and iron scaffolds were included in the study, for the comparison of results with the iron-hydroxyapatite-zinc functionally graded composite biomaterial.
Findings
The maximum weight loss and corrosion rate were found to be 6.98% and 2.38 mmpy, respectively, in the immersion test and electrochemical test for Fe-3.5HAp-54Zn biomaterial. Zinc-infiltrated composite biomaterials exhibited excellent cytocompatibility and hemocompatibility as compared to pure dense iron and iron scaffolds. A comparative analysis was conducted, taking into account relevant literature, and it was determined that the fabricated iron-hydroxyapatite-zinc biomaterial demonstrated desirable degradation and biological characteristics, customized to meet the specific requirements of bone tissue engineering applications.
Originality/value
TOFGC iron-hydroxyapatite-zinc biomaterial has been fabricated for the first time using the developed novel methodology and their degradation and biological characterizations were performed.
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Gurminder Singh and Pulak Mohan Pandey
The purpose of this study is to study the mechanical, tribological and electrical properties of the copper-graphene (Cu-Gn) composites fabricated by a novel rapid tooling…
Abstract
Purpose
The purpose of this study is to study the mechanical, tribological and electrical properties of the copper-graphene (Cu-Gn) composites fabricated by a novel rapid tooling technique consist of three-dimensional printing and ultrasonic-assisted pressureless sintering (UAPS).
Design/methodology/approach
Four different Cu-Gn compositions with 0.25, 0.5, 1 and 1.5 per cent of graphene were fabricated using an amalgamation of three-dimensional printing and UAPS. The polymer 3d printed parts were used to prepare mould cavity and later the UAPS process was used to sinter Cu-Gn powder to acquire free-form shape. The density, hardness, wear rate, coefficient of friction and electrical conductivity were evaluated for the different compositions of graphene and compared with the pure copper. Besides, the comparison was performed with the conventional method.
Findings
Cu-Gn composites revealed excellent wear properties due to higher hardness, and the lubrication provided by the graphene. The electrical conductivity of the fabricated Cu-Gn composites started increasing initially but decreased afterwards with increasing the content of graphene. The UAPS fabricated composites outperformed the conventional method manufactured samples with better properties such as density, hardness, wear rate, coefficient of friction and electrical conductivity due to homogeneous mixing of metal particles and graphene.
Originality/value
The fabrication of Cu-Gn composite freeform shapes was found to be difficult using conventional methods. The novel technique using a combination of polymer three-dimensional printing and UAPS as rapid tooling was introduced for the fabrication of freeform shapes of Cu-Gn composites and mechanical, tribological and electrical properties were studied. The method can be used to fabricate optimized complex Cu-Gn structures with improved wear and electrical applications.
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Brijesh H. Patel and Pulak Mohan Pandey
Natural elements in the biological organs of plants and animals consist of repetitive geometries, which often form the basis for the new lattice structure design with improved…
Abstract
Purpose
Natural elements in the biological organs of plants and animals consist of repetitive geometries, which often form the basis for the new lattice structure design with improved performance. The purpose of this study is to investigate the energy absorption capabilities and deformation behavior of lattice structures inspired by Helleborus petticoat flower and fish scale patterns.
Design/methodology/approach
The authors designed arc-shaped strut lattice structures by incorporating the geometrical features of Helleborus petticoat flower and fish scale pattern into lattice strut configuration. The structures were printed from thermoplastic polyurethane (TPU) material using fused deposition modeling process and tested under uniaxial compression. The energy absorption parameters, such as specific energy absorption (SEA), mean plateau stress, onset densification strain and absorption efficiency were determined, and deformation mechanism under static compression was analyzed. The SEA of proposed structures was compared with other TPU structures in the reported literature.
Findings
The results show that the lattice strut configuration affects the mechanical properties, energy absorption characteristics and deformation behavior of the proposed bio-inspired structures. The SEA was found to be in the range of 0.34–0.97 kJ / kg. Overall, the novel flower-inspired structure displayed significantly higher SEA (+185%), compared to fish scale-derived structure.
Originality/value
To the best of the authors’ knowledge, the authors have designed the proposed lattice structures for the first time. The energy absorption characteristics and deformation behavior of proposed lattice structures had never been reported previously.
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Jatender Pal Singh and Pulak Mohan Pandey
The requirements of open cell porous regular interconnected metallic structure (OCPRIMS) in applications such as heat exchangers, sound absorption, fluid flow control, spark…
Abstract
Purpose
The requirements of open cell porous regular interconnected metallic structure (OCPRIMS) in applications such as heat exchangers, sound absorption, fluid flow control, spark arresters and biocompatible inserts have been increased. As per available technology in the present scenario, only the metallic-based rapid prototyping (RP) machines can guarantee fabrication of OCPRIMS. Metal-based RP machines are capital-intensive. So, this study aims to develop a technique for fabrication of OCPRIMS economically using three-dimensional printing (3 DP) and pressureless sintering.
Design/methodology/approach
Three computer-aided design (CAD) models of varying designed interconnected porosity 73, 70 and 60 per cent were modeled to target metallic porosity 27, 30 and 40 per cent. The same were fabricated with ceramic-based powder using 3 DP. Thereafter, spherical bronze powder with average size of 200 µm was filled and sintered in pressureless manner under inert atmosphere of argon. After sintering, the specimens were cleaned with the help of pricking needles and high-pressure water. It flushed the burnt ceramic powder and allowed metallic portion to remain intact. The obtained specimens were inverse of CAD/3 DP models. The dimensional measurement at different stages of fabrication was carried out to find shrinkage. Sintered density and interconnected porosity were measured using Archimedes’ principle. The characterization of the fabricated specimens was done with the help of microstructure analysis, scanning electron microscopy and energy dispersive x-ray analysis. Mechanical properties were assessed using compressive, tensile and Charpy tests.
Findings
The feasibility has been explored successfully to fabricate OCPRIMS of phosphor bronze using 3 DP and pressureless sintering process. Interconnected porosity of 51.45, 56.45, 64.09 per cent of final metallic specimens has been observed against the targeted 27, 30 and 40 per cent. The increase in pore dimensions up to 19.13 per cent and shrinkage up to 5.44 per cent of outer dimensions were found to be the main causes of increase in interconnected porosity level. The characterization results exhibit the behavior of pressureless sintering process and stability of the fabricated specimens. Mechanical properties of fabricated structures are found to be dependent on porosity and strut diameter. Compressive and tensile strength decrease with the increase in porosity for strut diameter less than 1 mm, whereas they increase with the increase in strut diameter of 1 mm or more. A similar trend has been observed for impact strength also.
Originality/value
This paper explores the feasibility to fabricate OCPRIMS economically using 3 DP and pressureless sintering process.
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Arun Kumar, Pulak Mohan Pandey, Sunil Jha and Shib Shankar Banerjee
This paper aims to discuss the successful 3D printing of styrene–ethylene–butylene–styrene (SEBS) block copolymers using solvent-cast 3D printing (SC-3DP) technique.
Abstract
Purpose
This paper aims to discuss the successful 3D printing of styrene–ethylene–butylene–styrene (SEBS) block copolymers using solvent-cast 3D printing (SC-3DP) technique.
Design/methodology/approach
Three different Kraton grade SEBS block copolymers were used to prepare viscous polymer solutions (ink) in three different solvents, namely, toluene, cyclopentane and tetrahydrofuran. Hansen solubility parameters (HSPs) were taken into account to understand the solvent–polymer interactions. Ultraviolet–visible spectroscopy was used to analyze transmittance behavior of different inks. Printability of ink samples was compared in terms of shape retention capability, solvent evaporation and shear viscosity. Dimensional deviations in 3D-printed parts were evaluated in terms of percentage shrinkage. Surface morphology of 3D-printed parts was investigated by scanning electron microscope. In addition, mechanical properties and rheology of the SC-3D-printed SEBS samples were also investigated.
Findings
HSP analysis revealed toluene to be the most suitable solvent for SC-3DP. Cyclopentane showed a strong preferential solubility toward the ethylene–butylene block. Microscopic surface cracks were present on tetrahydrofuran ink-based 3D-printed samples. SC-3D-printed samples exhibited high elongation at break (up to 2,200%) and low tension set (up to 9%).
Practical implications
SC-3DP proves to be an effective fabrication route for complex SEBS parts overcoming the challenges associated with fused deposition modeling.
Originality/value
To the best of authors’ knowledge, this is the first report investigating the effect of different solvents on physicomechanical properties of SC-3D-printed SEBS block copolymer samples.
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Jasvinder Singh, Pulak Mohan Pandey, Tejinder Kaur and Neetu Singh
The purpose of this paper is to fabricate pre-existing geometries of the stents using solvent cast 3D printing (SC3P) and encapsulation of each stent with heparin drug by using…
Abstract
Purpose
The purpose of this paper is to fabricate pre-existing geometries of the stents using solvent cast 3D printing (SC3P) and encapsulation of each stent with heparin drug by using aminolysis reaction.
Design/methodology/approach
The iron pentacarbonyl powder and poly-ɛ-caprolactone blend (PCIP) were used to print stent designs of Art18z, Palmaz-Schatz and Abbott Bvs1.1. The properties of antithrombosis, anticoagulation and blood compatibility were introduced in the stents by conjugation of heparin drug via the aminolysis process. The aminolysis process was confirmed by energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy due to presence of amide group and nitrogen peak in the respective analysis. Biological studies were performed to depict the cell viability, hemocompatibility and antithrombotic properties. Besides, mechanical behaviors were analyzed to study the behavior of the stents under radial compression load and bending load.
Findings
The amount of heparin immobilized on the Art18z, Palmaz-Schatz and Abbott Bvs1.1 stents were 255 ± 27, 222 ± 30 and 212 ± 13 µg, respectively. The cell viability studies using L929 fibroblast cells confirmed the cytocompatibility of the stents. The heparinized SC3P printed stents displayed excellent thrombo-resistance, anticoagulation properties and hemocompatibility as confirmed by blood coagulation analysis, platelet adhesion test and hemolysis analysis. Besides, mechanical behavior was found in context of the real-life stents. All these assessments confirmed that the developed stents have the potential to be used in the real environment of coronary arteries.
Originality/value
Various customized shaped biodegradable stents were fabricated using 3D printing technique and encapsulated with heparin drug using aminolysis process.
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Dilpreet Singh, Bhavuk Garg, Pulak Mohan Pandey and Dinesh Kalyanasundaram
The purpose of this paper is to establish a methodology for the design and development of patient-specific elbow implant with an elastic modulus close to that of the human bone…
Abstract
Purpose
The purpose of this paper is to establish a methodology for the design and development of patient-specific elbow implant with an elastic modulus close to that of the human bone. One of the most preferred implant material is titanium alloy which is about 8 to 9 times higher in strength than that of the human bone and is the closest than other metallic biomedical materials.
Design/methodology/approach
The methodology begins with the design of the implant from patient-specific computed tomography information and incorporates the manufacturing of the implant via a novel rapid prototyping assisted microwave sintering process.
Findings
The elastic modulus and the flexural strength of the implant were observed to be comparable to that of human elbow bones. The fatigue test depicts that the implant survives the one million cycles under physiological loading conditions. Other mechanical properties such as impact energy absorption, hardness and life cycle tests were also evaluated. The implant surface promotes human cell growth and adhesion and does not cause any adverse or undesired effects i.e. no cytotoxicity.
Practical implications
Stress shielding, and therefore, aseptic loosening of the implant shall be avoided. In the event of any trauma post-implantation, the implant would not hurt the patient.
Originality/value
The present study describes a methodology for the first time to be able to obtain the strength required for the medical implant without sacrificing the fatigue life requirement.
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Rudranarayan Kandi, Pulak Mohan Pandey, Misba Majood and Sujata Mohanty
This paper aims to discuss the successful fabrication of customized tubular scaffolds for tracheal tissue engineering with a novel route using solvent-based extrusion 3D printing.
Abstract
Purpose
This paper aims to discuss the successful fabrication of customized tubular scaffolds for tracheal tissue engineering with a novel route using solvent-based extrusion 3D printing.
Design/methodology/approach
The manufacturing approach involved extrusion of polymeric ink over a rotating predefined pattern to construct customized tubular structure of polycaprolactone (PCL) and polyurethane (PU). Dimensional deviation in thickness of scaffolds were calculated for various layer thicknesses of 3D printing. Physical and chemical properties of scaffolds were investigated by scanning electron microscope (SEM), contact angle measurement, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD). Mechanical characterizations were performed, and the results were compared to the reported properties of human native trachea from previous reports. Additionally, in vitro cytotoxicity of the fabricated scaffolds was studied in terms of cell proliferation, cell adhesion and hemagglutination assay.
Findings
The developed fabrication route was flexible and accurate by printing customized tubular scaffolds of various scales. Physiochemical results showed good miscibility of PCL/PU blend, and decrease in crystalline nature of blend with the addition of PU. Preliminary mechanical assessments illustrated comparable mechanical properties with the native human trachea. Longitudinal compression test reported outstanding strength and flexibility to maintain an unobstructed lumen, necessary for the patency. Furthermore, the scaffolds were found to be biocompatible to promote cell adhesion and proliferation from the in vitro cytotoxicity results.
Practical implications
The attempt can potentially meet the demand for flexible tubular scaffolds that ease the concerns such as availability of suitable organ donors.
Originality/value
3D printing over accurate predefined templates to fabricate customized grafts gives novelty to the present method. Various customized scaffolds were compared with conventional cylindrical scaffold in terms of flexibility.
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While rapid increase in demand for foods but limited availability of croplands has forced to adopt input-intensive farming practices to increase yield, there are serious long-term…
Abstract
While rapid increase in demand for foods but limited availability of croplands has forced to adopt input-intensive farming practices to increase yield, there are serious long-term ecological implications including degradation of biodiversity. It is increasingly recognised that ensuring agricultural sustainability under the changing climatic conditions requires a change in the production system along with necessary policies and institutional arrangements. In this context, this chapter examines if climate-smart agriculture (CSA) can facilitate adaptation and mitigation practices by improving resource utilisation efficiency in India. Such an attempt has special significance as the existing studies have very limited discussions on three main aspects, viz., resource productivity, adaptation practices and mitigation strategies in a comprehensive manner. Based on insights from the existing studies, this chapter points out that CSA can potentially make significant contribution to enhancing resource productivity, adaptation practices, mitigation strategies and food security, especially among the land-constrained farmers who are highly prone to environmental shocks. In this connection, staggered trench irrigation structure has facilitated rainwater harvesting, local irrigation and livelihood generation in West Bengal. However, it is necessary to revisit the existing approaches to promotion of CSA and dissemination of information on the design of local adaptation strategies. This chapter also proposes a change in the food system from climate-sensitive to CSA through integration of technologies, institutions and policies.