Engineering Sciences and Technology - Publications

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Browsing Engineering Sciences and Technology - Publications by Author "Acharyya, Amit"
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    Area-elficient interlayer signal propagation in 3D IC by introducing electron spin
    ( 2017-10-31) Debroy, Sanghamitra ; Acharyya, Amit ; Singh, Shiv Govind ; Acharyya, Swati Ghosh
    Through Silicon Via (TSV) is the major technology in order to transmit data among various devices in 3D IC. Therefore higher concentration of TSV is required for higher packing density in 3D IC. In order to obtain high density of TSV, the dimensions of TSV needs to be reduced. This may be achieved by increasing the surface area per layer which will benefit in packing of more components for any operation including logic implementation. In this paper we introduce electron spin rather than charge for the first time for interlayer signal transmission in 3D IC resulting in area efficiency. Ansys electromagnetic simulator (Maxwell 2D and 3D) and OOMMF simulation supported by theoretical analysis specifies an average of 90% area reduction per layer of 3D IC as compared to state-of-the art TSV.
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    Effects of Orientation and Temperature on the Tensile Strength of Pristine and Defective Bi-Layer Graphene Sheet – A Molecular Dynamics Study
    ( 2021-07-01) Debroy, Sanghamitra ; Acharyya, Swati Gosh ; Acharyya, Amit
    Molecular dynamics simulations with adaptive intermolecular reactive empirical bond order (AIREBO) potential were carried out to study the effect of temperature and orientation on the tensile strength of pristine and defective bilayer graphene (BLG) sheet. Results obtained reveal that the fall in tensile strength of pristine AA stacked BLG due to the presence of vacancy is significant at room temperature (300 K) but decreases at higher temperature (1073 K). Interestingly, this phenomenon reverses in case of AB stacked BLG, wherein the percentage fall in strength at higher temperature due to defect is more than that at room temperature. In order to understand these discrepancies in the results obtained, three case studies were conducted, and the results obtained suggested that when defects are present in armchair direction, this phenomenon occurs. The study also reveals that in case of AB stacked BLG, zigzag direction is more defect tolerant at room and high temperatures. Interestingly, variation of tensile strength due to the orientation is in good agreement with projections from potential energy concepts and theoretical calculations. We envisage that the study will provide useful information to the device engineers for the optimisation of the mechanical properties and convenient structural adaptation of bilayer graphene while working at wide range of temperatures.
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    Graphene heals thy cracks
    ( 2015-07-20) Debroy, Sanghamitra ; Miriyala, V. Pavan Kumar ; Sekhar, K. Vijaya ; Ghosh Acharyya, Swati ; Acharyya, Amit
    Molecular Dynamics simulations revealed the phenomena of self healing of cracks which were generated in graphene on application of tensile load exceeding its ultimate tensile strength. The phenomenon of self healing was observed when the system was studied at a very slow rate of 0.05 ps. Cracks initiated in the graphene sheet was allowed to propagate till it reached a critical length following which the load was removed and the sheet was relaxed. The study revealed that self healing of cracks took place within a critical crack opening displacement range of 0.3-0.5 nm in absence of any external stimulus. However, the self healing phenomenon was found to be independent of crack length. This self healing phenomenon occurred not only in pristine graphene sheet, but also in presence of pre-existing vacancies. The mechanism of self healing has been explained by detailed bond length/angle distribution analysis.
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    Nanomagnetic computing for next generation interconnects and logic design
    ( 2019-01-01) Debroy, Sanghamitra ; Sivasubramani, Santhosh ; Acharyya, Swati Ghosh ; Acharyya, Amit
    In this chapter a holistic approach towards the design of energy-efficient circuitry has been discussed. The novel material graphene with extraordinary mechanical, electrical, thermal and magnetic properties has been shown to have a huge potential in replacing copper for clocking the nanomagnetic-based circuits so that the huge current required for generating external magnetic field can be reduced. Through simulation results the above mentioned has also been established. This chapter on the other hand also provides an insight on nanomagnetic computing for next generation interconnects and logic design. The role of MQCA-based digital arithmetic circuits and their impact has also been well demonstrated in this chapter.
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    Self healing nature of bilayer graphene
    ( 2016-08-01) Debroy, Sanghamitra ; Pavan Kumar Miriyala, V. ; Vijaya Sekhar, K. ; Acharyya, Swati Ghosh ; Acharyya, Amit
    The phenomenon of self healing of cracks in bilayer graphene sheet has been studied using molecular dynamics simulations. The bilayer graphene sheet was subjected to uniaxial tensile load resulting in initiation and propagation of cracks on exceeding the ultimate tensile strength. Subsequently, all forces acting on the sheet were removed and sheet was relaxed. The cracks formed in the graphene sheet healed without any external aid within 0.4 ps The phenomenon of self healing of the cracks in graphene sheet was found to be independent of the length of the crack, but occurred for critical crack opening distance less than 5 Å for AA stacked sheet and 13 Å for AB stacked bilayer graphene sheet. Self healing was observed for both AB (mixed stacking of armchair and zigzag graphene sheet) and AA (both sheets of similar orientation i.e. either armchair-armchair or zigzag-zigzag) stacking of bilayer graphene sheet.
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    Self-healing phenomena of graphene: Potential and applications
    ( 2016-01-01) Vijayasekhar, K. ; Acharyya, Swati Ghosh ; Debroy, Sanghamitra ; Miriyala, V. Pavan Kumar ; Acharyya, Amit
    The present study investigates the self healing behavior of both pristine and defected single layer graphene using a molecular dynamic simulation. Single layer graphene containing various defects such as preexisting vacancies and differently oriented pre-existing cracks were subjected to uniaxial tensile loading till fracture occurred. Once the load was relaxed, the graphene was found to undergo self healing. It was observed that this self healing behaviour of cracks holds irrespective of the nature of pre-existing defects in the graphene sheet. Cracks of any length were found to heal provided the critical crack opening distance lies within 0.3-0.5 nm for a pristine sheet and also for a sheet with pre-existing defects. Detailed bond length analysis of the graphene sheet was done to understand the mechanism of self healing of graphene. The paper also discusses the immense potential of the self healing phenomena of graphene in the field of graphene based sub-nano sensors for crack sensing.
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    Shape memory alloy smart knee spacer to enhance knee functionality: Model design and finite element analysis
    ( 2016-10-13) Gautam, Arvind ; Rani, A. Bhargavi ; Callejas, Miguel A. ; Acharyya, Swati Ghosh ; Acharyya, Amit ; Biswas, Dwaipayan ; Bhandari, Vasundhra ; Sharma, Paresh ; Naik, Ganesh R.
    In this paper we introduce Shape Memory Alloy (SMA) for designing the tibial part of Total Knee Arthroplasty (TKA) by exploiting the shape-memory and pseudo-elasticity property of the SMA (e.g. NiTi). This would eliminate the drawbacks of the state-of-the art PMMA based knee-spacer including fracture, sustainability, dislocation, tilting, translation and subluxation for tackling the Osteoarthritis especially for the aged people of 45-plus or the athletes. In this paper a Computer Aided Design (CAD) model using SolidWorks for the knee-spacer is presented based on the proposed SMA adopting the state-of-the art industry-standard geometry that is used in the PMMA based spacer design. Subsequently Ansys based Finite Element Analysis is carried out to measure and compare the performance between the proposed SMA based model with the state-of-the art PMMA ones. 81% more bending is noticed in the PMMA based spacer compared to the proposed SMA that would eventually cause fracture and tilting or translation of spacer. Permanent shape deformation of approximately 58.75% in PMMA based spacer is observed compared to recoverable 11% deformation in SMA when same load is applied on both separately.
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    Shape memory effect of nano-ferromagnetic particle doped NiTi for orthopedic devices and rehabilitation techniques
    ( 2017-09-13) Gautam, Arvind ; Balouria, Anuradha ; Acharyya, Amit ; Acharyya, Swati Ghosh ; Panwar, Madhuri ; Naik, Ganesh R.
    This paper introduces a novel shape memory alloy (SMA) material for the controllability in the shape recovery of traditional SMA for orthopedic devices and rehabilitation techniques. The proposed material is formed by doping nano-ferromagnetic particle into porous NiTi alloy. The finite element analysis of shape memory effect property of the different distribution of nano-ferromagnetic particle is done and compared for same load and boundary conditions. The comparative analysis of the percentage change in volume deformation when load is released (for 2nd step) shows an average of 2.55 % with standard deviation of 1.69 whereas on thermal loading (for 3rd step) shows an average of 94.94% with standard deviation of 7.75 for all heterogeneous distribution of nano-particles in porous NiTi alloy. Our findings are, all the different conditions of heterogeneous distributions of nano-ferromagnetic particle doped NiTi alloy exhibits its inherent SME property.
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    Shape-memory-alloy-based smart knee spacer for total knee arthroplasty: 3D CAD modelling and a computational study
    ( 2018-05-01) Gautam, Arvind ; Callejas, Miguel A. ; Acharyya, Amit ; Acharyya, Swati Ghosh
    This study introduced a shape memory alloy (SMA)-based smart knee spacer for total knee arthroplasty (TKA). Subsequently, a 3D CAD model of a smart tibial component of TKA was designed in Solidworks software, and verified using a finite element analysis in ANSYS Workbench. The two major properties of the SMA (NiTi), the pseudoelasticity (PE) and shape memory effect (SME), were exploited, modelled, and analysed for a TKA application. The effectiveness of the proposed model was verified in ANSYS Workbench through the finite element analysis (FEA) of the maximum deformation and equivalent (von Mises) stress distribution. The proposed model was also compared with a polymethylmethacrylate (PMMA)-based spacer for the upper portion of the tibial component for three subjects with body mass index (BMI) of 23.88, 31.09, and 38.39. The proposed SMA -based smart knee spacer contained 96.66978% less deformation with a standard deviation of 0.01738 than that of the corresponding PMMA based counterpart for the same load and flexion angle. Based on the maximum deformation analysis, the PMMA-based spacer had 30 times more permanent deformation than that of the proposed SMA-based spacer for the same load and flexion angle. The SME property of the lower portion of the tibial component for fixation of the spacer at its position was verified by an FEA in ANSYS. Wherein, a strain life-based fatigue analysis was performed and tested for the PE and SME built spacers through the FEA. Therefore, the SMA-based smart knee spacer eliminated the drawbacks of the PMMA-based spacer, including spacer fracture, loosening, dislocation, tilting or translation, and knee subluxation.
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    Synergistic effect of temperature and point defect on the mechanical properties of single layer and bi-layer graphene
    ( 2017-10-01) Debroy, Sanghamitra ; Pavan Kumar, V. ; Vijaya Sekhar, K. ; Acharyya, Swati Ghosh ; Acharyya, Amit
    The present study reports a comprehensive molecular dynamics simulation of the effect of a) temperature (300–1073 K at intervals of every 100 K) and b) point defect on the mechanical behaviour of single (armchair and zigzag direction) and bilayer layer graphene (AA and AB stacking). Adaptive intermolecular reactive bond order (AIREBO) potential function was used to describe the many-body short-range interatomic interactions for the single layer graphene sheet. Moreover, Lennard Jones model was considered for bilayer graphene to incorporate the van der Waals interactions among the interlayers of graphene. The effect of temperature on the strain energy of single layer and bilayer graphene was studied in order to understand the difference in mechanical behaviour of the two systems. The strength of the pristine single layer graphene was found to be higher as compared to bilayer AA stacked graphene at all temperatures. It was observed at 1073 K and in the presence of vacancy defect the strength for single layer armchair sheet falls by 30% and for bilayer armchair sheet by 33% as compared to the pristine sheets at 300 K. The AB stacked graphene sheet was found to have a two-step rupture process. The strength of pristine AB sheet was found to decrease by 22% on increase of temperature from 300 K to 1073 K.
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    Temperature and Size Effect on the Electrical Properties of Monolayer Graphene based Interconnects for Next Generation MQCA based Nanoelectronics
    ( 2020-12-01) Debroy, Sanghamitra ; Sivasubramani, Santhosh ; Vaidya, Gayatri ; Acharyya, Swati Ghosh ; Acharyya, Amit
    Graphene interconnects have been projected to out-perform Copper interconnects in the next generation Magnetic Quantum-dot Cellular Automata (MQCA) based nano-electronic applications. In this paper a simple two-step lithography process for patterning CVD monolayer graphene on SiO2/Si substrate has been used that resulted in the current density of one order higher magnitude as compared to the state-of-the-art graphene-based interconnects. Electrical performances of the fabricated graphene interconnects were evaluated, and the impact of temperature and size on the current density and reliability was investigated. The maximum current density of 1.18 ×108 A/cm2 was observed for 0.3 μm graphene interconnect on SiO2/Si substrate, which is about two orders and one order higher than that of conventionally used copper interconnects and CVD grown graphene respectively, thus demonstrating huge potential in outperforming copper wires for on-chip clocking. The drop in current at 473 K as compared to room temperature was found to be nearly 30%, indicating a positive temperature coefficient of resistivity (TCR). TCR for all cases were studied and it was found that with decrease in width, the sensitivity of temperature also reduces. The effect of resistivity on the breakdown current density was analysed on the experimental data using Matlab and found to follow the power-law equations. The breakdown current density was found to have a reciprocal relationship to graphene interconnect resistivity suggesting Joule heating as the likely mechanism of breakdown.
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    Thermo-magnetic control system for nano-ferromagnetic particle doped shape memory alloy for orthopedic devices and rehabilitation techniques
    ( 2017-12-01) Gautam, Arvind ; Balouria, Anuradha ; Andem, Divya ; Mounika, Kare ; Rani, A. Bhargavi ; Acharyya, Amit ; Acharyya, Swati Ghosh
    This paper introduces a control mechanism targeting mechatronic devices by use of thermomagnetic loading instead of thermal loading for the proposed nano-ferromagnetic doped porous Shape Memory Alloy (SMA). The proposed material is formed by doping nano-ferromagnetic particle into porous NiTi alloy, an example of SMA. The Computer Aided design (CAD) and corresponding finite element analysis of shape memory effect (SME) property of the different distribution of nanoferromagnetic particle are done and compared against the same load and boundary conditions. The comparative analysis of the percentage change in the volume deformation in finite element analysis for SME when load is released (for 2nd step) shows an average of 2.55% with standard deviation of 1.69 whereas on thermal loading (for 3rd step) shows an average of 94.94% with standard deviation of 7.75 for all heterogeneous distribution of nano-particles in porous NiTi alloy. Thus, all the distribution of nano-ferromagnetic doped porous NiTi show SME property. For the proof of concept demonstration of the mechatronic device using the proposed SMA, an experiment is designed using a bimetallic strip, microcontroller, sensor and feedback circuitry system. It is observed that for the supply of 4 V and bent angle for flex sensor between 0 to 45 degree, current through the solenoid is 3.63 A producing magnetic field of 1.42 mT and for flex sensor bent angle 45 to 55 degree the current through the solenoid is 1.2 A producing magnetic field of 0.47 mT for same supply and if the flex sensor bent angle increases more than 55 degree then the voltage supply cuts off indicating absence of magnetic field substantiating the claim of controllability.
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    Thermo-magnetic shape control of nano-ferromagnetic particle doped shape memory alloy for orthopedic devices and rehabilitation techniques
    ( 2017-07-12) Gautam, Arvind ; Mounika, Kare ; Andem, Divya ; Karhade, Pallavi ; Rani, A. Bhargavi ; Acharyya, Amit ; Acharyya, Swati Ghosh
    Recent advancement in smart materials facilitated the use of Shape Memory Alloy(SMA) in treatment of different orthopedic problems and rehabilitation technique to treat paralyzed patients. But Shape Memory alloy lacks the controllability while regaining the shape from martensite to austenite during thermal loading. Therefore, in this paper we introduced a mechatronic device which provides the control over the shape change of new hybrid material having property of SMA and shape memory property of anticipated material is verified by finite element analysis in COMSOL Multiphysics. In the proposed methodology the shape is controlled by generating a controlled thermo-magnetic loading, and hybrid material formed by doping a nano-ferromagnetic particle in porous NiTi SMA. For the proof of the concept an experiment is carried out by using a bimetallic strip, microcontroller, sensor and proper feedback circuitry system and it is observed that for the supply of 4V and bent angle for flex sensor between 0 to 40 degree, current through the solenoid is 3.63A producing Magnetic field of 1.42mT and for flex sensor b ent angle 4 0 to 7 5 degree the current through the solenoid is 1.2A producing Magnetic field of 0.47mT for same supply and if the flex sensor bent angle increases more than 75 degree then the voltage supply cutoffs which indicate the absence of Magnetic field.
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    Tunable intrinsic magnetic phase transition in pristine single-layer graphene nanoribbons
    ( 2018-09-07) Sivasubramani, Santhosh ; Debroy, Sanghamitra ; Acharyya, Swati Ghosh ; Acharyya, Amit
    In this paper, we report on the interesting phenomenon of magnetic phase transitions (MPTs) observed under the combined influence of an electric field (E) and temperature (T) leading to a thermo-electromagnetic effect on the pristine single-layer zigzag graphene nanoribbon (szGNR). Density functional theory-based first principles calculations have been deployed for this study on the intrinsic magnetic properties of graphene. Interestingly, by tuning electric field (E) and temperature (T), three distinct magnetic phase behaviors, para-, ferro- and antiferromagnetic are exhibited in pristine szGNR. We have investigated the unrivaled positional parameters of these MPTs. MPT occurring in the system also follows a positional trend and the change in these positional parameters with regard to the size of the szGNR along with the varied E and T is studied. We propose a bow-tie schematic to induce the intrinsic magnetism in graphene and present the envisaged model of the processor application with the reported intrinsic MPT in szGNR. This fundamental insight into the intrinsic MPTs in graphene is an essential step towards developing graphene-based spin-transfer torque magnetoresistive random access memory, quantum computing devices, magnonics and spintronic memory application.