Current Researches
3D Printing/Fused Deposition Modelling:
Additive manufacturing (commonly referred to as 3D printing) has the potential to revolutionize manufacturing. However direct 3D printing of functional materials (with electrical or magnetic capabilities) at the same time as the bulk structures are not feasible with today’s commercially available technologies. Therefore, the main objective of this research is to develop methods to use several types of materials simultaneously for printing micro-structures for electronics and MEMS in three dimensional directions in single processes. One of the most important concern of this project is to fabricate devices in the field of Information and Communication Technology (ICT) like antennas etc. Not only that, wearable devices like pressure sensor, strain sensor etc. are also included in the intersect of this research.
The planned methodology starts from taking an existing commercial 3D printer (Fused Deposition Modelling type) and modifying the extrusion head to permit deposition or printing of different materials from a single nozzle in a predetermined pathway making 3D micro structures on a suitable substrate. This should allow the modification of materials properties while extruding in a single process. Multiple filaments of different materials will be fed through one extrusion nozzle and tested for flow compatibility and adhesion during this work. Analysis of heat involving the extrusion process to change the make-up of material as it is being deposited would also be a component of this research. The properties of the adhesion of heterogeneous materials like composites, low melting point alloys or different polymers (hard and soft) will be examined to optimize the characteristics of printed structures. Another important issue is their flow property, which also will be characterized using micro-extruder systems. Finally integration of the deposition of the different materials with finishing techniques to place other important components like electrodes, composites, liquid metals would also be investigated. These other techniques may include ink-jet type nozzles, or rollers to improve surface qualities.
During the project, we hope to accomplish to develop micro sized antenna materials in objects that may alter shape and size to permit changing the frequency ranges of the antennas using mainly polymer based composite materials enabling low cost and light weight production. We will not only be concerned on technical efficiency but also on the feasibility in terms of production processes. My extensive prior experience in synthesis and characterization of silver nanoparticle based conductive ink will greatly help this project. This work will significantly advance the capacities of one of the most common types of 3D printing tools available and may allow for cheap manufacturing of complete functional devices in future, including simple circuits or even motors. This is the promise once metals, semi-conductors, plastics and ceramics can be deposited in a single process.
Liquid Metal:
There are several metallic alloy which remain liquid at room temperature. Example includes Gallium and Indium based liquid metals like Galinstan (68.5% Ga, 21.5% In & 10.0% Sn), eutectic EGaIn ( 75.5% Ga & 24.5% In). The micro-structured liquid metal embedded in elastomers like PDMS, Silicone etc. has potentiality to use as flexible pressure, strain sensors in the field of wearable electronics. Currently research is going on this liquid metal to enhance the applicability of the those sensors.
Additive manufacturing (commonly referred to as 3D printing) has the potential to revolutionize manufacturing. However direct 3D printing of functional materials (with electrical or magnetic capabilities) at the same time as the bulk structures are not feasible with today’s commercially available technologies. Therefore, the main objective of this research is to develop methods to use several types of materials simultaneously for printing micro-structures for electronics and MEMS in three dimensional directions in single processes. One of the most important concern of this project is to fabricate devices in the field of Information and Communication Technology (ICT) like antennas etc. Not only that, wearable devices like pressure sensor, strain sensor etc. are also included in the intersect of this research.
The planned methodology starts from taking an existing commercial 3D printer (Fused Deposition Modelling type) and modifying the extrusion head to permit deposition or printing of different materials from a single nozzle in a predetermined pathway making 3D micro structures on a suitable substrate. This should allow the modification of materials properties while extruding in a single process. Multiple filaments of different materials will be fed through one extrusion nozzle and tested for flow compatibility and adhesion during this work. Analysis of heat involving the extrusion process to change the make-up of material as it is being deposited would also be a component of this research. The properties of the adhesion of heterogeneous materials like composites, low melting point alloys or different polymers (hard and soft) will be examined to optimize the characteristics of printed structures. Another important issue is their flow property, which also will be characterized using micro-extruder systems. Finally integration of the deposition of the different materials with finishing techniques to place other important components like electrodes, composites, liquid metals would also be investigated. These other techniques may include ink-jet type nozzles, or rollers to improve surface qualities.
During the project, we hope to accomplish to develop micro sized antenna materials in objects that may alter shape and size to permit changing the frequency ranges of the antennas using mainly polymer based composite materials enabling low cost and light weight production. We will not only be concerned on technical efficiency but also on the feasibility in terms of production processes. My extensive prior experience in synthesis and characterization of silver nanoparticle based conductive ink will greatly help this project. This work will significantly advance the capacities of one of the most common types of 3D printing tools available and may allow for cheap manufacturing of complete functional devices in future, including simple circuits or even motors. This is the promise once metals, semi-conductors, plastics and ceramics can be deposited in a single process.
Liquid Metal:
There are several metallic alloy which remain liquid at room temperature. Example includes Gallium and Indium based liquid metals like Galinstan (68.5% Ga, 21.5% In & 10.0% Sn), eutectic EGaIn ( 75.5% Ga & 24.5% In). The micro-structured liquid metal embedded in elastomers like PDMS, Silicone etc. has potentiality to use as flexible pressure, strain sensors in the field of wearable electronics. Currently research is going on this liquid metal to enhance the applicability of the those sensors.
Previous Researches
Conductive Silver Ink for Inkjet Printing:
Silver nanoparticle of less than 50 nm size was synthesized from silver nitrate, Polyvinylpyrrolidone and Ethylene Glycol as metal precursor, stabilizer and reducing agent respectively. Then conductive silver ink was prepared with suitable solvent by adding surfactant and viscosifier to adjust surface tension and viscosity to make useful for inkjet printer. In this research work, the influences of Polyvinylpyrrolidone molecular weight (MW = 10,000, 40,000, 360,000) and reaction temperature (100C, 120C, 140C, 160C) on the size of silver nano particle were analyzed. Moreover, the effects of solvent, sintering temperature and solid content on electrical resistivity were also examined with spin coated silver ink sintered on dry cellulose film. It has been found that, 50% co-solvent system of Deionized water and Di-ethylene glycol and solid content of around 50% maximize the performance of silver ink in terms of electrical conductivity. This silver ink can be used for Pen-on-Paper (PoP) technology for light, flexible electronic devices. Finally the synthesized silver ink has been used in Dimatix inkjet printer to print conductive micro-electrode on previously developed cellulose film.
Silver nanoparticle of less than 50 nm size was synthesized from silver nitrate, Polyvinylpyrrolidone and Ethylene Glycol as metal precursor, stabilizer and reducing agent respectively. Then conductive silver ink was prepared with suitable solvent by adding surfactant and viscosifier to adjust surface tension and viscosity to make useful for inkjet printer. In this research work, the influences of Polyvinylpyrrolidone molecular weight (MW = 10,000, 40,000, 360,000) and reaction temperature (100C, 120C, 140C, 160C) on the size of silver nano particle were analyzed. Moreover, the effects of solvent, sintering temperature and solid content on electrical resistivity were also examined with spin coated silver ink sintered on dry cellulose film. It has been found that, 50% co-solvent system of Deionized water and Di-ethylene glycol and solid content of around 50% maximize the performance of silver ink in terms of electrical conductivity. This silver ink can be used for Pen-on-Paper (PoP) technology for light, flexible electronic devices. Finally the synthesized silver ink has been used in Dimatix inkjet printer to print conductive micro-electrode on previously developed cellulose film.
Cellulose Based Bio-sensors:
Different types of bio-sensor can be developed by using Cellulose-Metal Oxide nanocomposites. As a metal oxide, SnO2, TiO2 and ZnO are very useful in bio-sensor application. Glucose bio-sensor and Urea bio-sensor have been developed with Cellulose-SnO2 blended nanocomposite. The feasibility study of glucose oxidase (GOx) immobilized cellulose–tin oxide (SnO2)hybrid nanocomposite as a glucose biosensor was examined. Porous SnO2 layer was grown on regenerated cellulose films via liquid phase deposition technique with varying deposition time. Tin oxide was crystallized in the solution and formed nanocrystal coatings on the cellulose films. Enzyme (GOx) was immobilized into cellulose–SnO2 hybrid nanocomposite by physical absorption method. X-ray photoelectron spectroscopy analysis revealed the successful immobilization of GOx into the cellulose–SnO2 hybrid nanocomposite via covalent bonding between GOx and SnO2. The glucose biosensor under study is displayed linear response in the range of 0.5–12 mM with correlation coefficient of 0.96, which can cover the clinical region of glucose concentration. These results indicate that the cellulose–SnO2 hybrid nanocomposite can be an inexpensive, flexible and disposable glucose biosensor.
Different types of bio-sensor can be developed by using Cellulose-Metal Oxide nanocomposites. As a metal oxide, SnO2, TiO2 and ZnO are very useful in bio-sensor application. Glucose bio-sensor and Urea bio-sensor have been developed with Cellulose-SnO2 blended nanocomposite. The feasibility study of glucose oxidase (GOx) immobilized cellulose–tin oxide (SnO2)hybrid nanocomposite as a glucose biosensor was examined. Porous SnO2 layer was grown on regenerated cellulose films via liquid phase deposition technique with varying deposition time. Tin oxide was crystallized in the solution and formed nanocrystal coatings on the cellulose films. Enzyme (GOx) was immobilized into cellulose–SnO2 hybrid nanocomposite by physical absorption method. X-ray photoelectron spectroscopy analysis revealed the successful immobilization of GOx into the cellulose–SnO2 hybrid nanocomposite via covalent bonding between GOx and SnO2. The glucose biosensor under study is displayed linear response in the range of 0.5–12 mM with correlation coefficient of 0.96, which can cover the clinical region of glucose concentration. These results indicate that the cellulose–SnO2 hybrid nanocomposite can be an inexpensive, flexible and disposable glucose biosensor.
CNT Based Composite:
A computational modeling approach for evaluating the mechanical behavior of CNT based nanocomposite was performed. The CNT’s interaction with matrix material was modeled using the continuum mechanics theory and finite element approach. The effective mechanical properties of CNT based nanocomposite were then evaluated by using the finite element method (FEM) models. Two different models were constructed. The first model was a CNT through the length of the square representative volume element (RVE). The second model considers a CNT inside the square representative volume element (RVE). Several numerical examples were carried out to investigate the influence of Young’s modulus of matrix, CNT thickness, Poisson’s ratio and interphase on the effective modulus of CNT based nanocomposite in longitudinal direction. The computed results were compared with those obtained from the simple rule of mixture for validity.Characterization of carbon nano tube (CNT) based nanocomposites with the help of ANSYS 10.0. Simulation has been performed to predict the Young's modulus of elasticity of the composite material. It has been found that, inclusion of only 1% CNT can increase Young's modulus of elasticity as 10 times.
A computational modeling approach for evaluating the mechanical behavior of CNT based nanocomposite was performed. The CNT’s interaction with matrix material was modeled using the continuum mechanics theory and finite element approach. The effective mechanical properties of CNT based nanocomposite were then evaluated by using the finite element method (FEM) models. Two different models were constructed. The first model was a CNT through the length of the square representative volume element (RVE). The second model considers a CNT inside the square representative volume element (RVE). Several numerical examples were carried out to investigate the influence of Young’s modulus of matrix, CNT thickness, Poisson’s ratio and interphase on the effective modulus of CNT based nanocomposite in longitudinal direction. The computed results were compared with those obtained from the simple rule of mixture for validity.Characterization of carbon nano tube (CNT) based nanocomposites with the help of ANSYS 10.0. Simulation has been performed to predict the Young's modulus of elasticity of the composite material. It has been found that, inclusion of only 1% CNT can increase Young's modulus of elasticity as 10 times.