Department of Mechanical engineering

Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1921

Browse

Author: search.filters.author.Rao, Venkatesh K.P.Subject: search.filters.subject.Mechanical Engineering

Search Results

Now showing 1 - 10 of 25
  • No Thumbnail Available
    Item
    Extraction of Modal Parameters of Micromachined Resonators in Higher Modes
    (Springer, 2014-01) Rao, Venkatesh K.P.
    In this paper, a micro machined resonator is fabricated using SOI MUMPs process. A total of 50 out-of-plane mode shapes and their corresponding modal parameters (resonant frequency and damping) are extracted. With the applied voltage, due to joule heating, natural frequency (f n ) and Quality (Q) factor change. This can be effectively used for tuning the resonator. A detailed modal analysis is carried out using an FEM simulator to compute the modal parameters across all the modes and results are within 5% of the data measured using a Laser Vibrometer. Q is estimated using the half-power point approach for the first 42 modes. It is also observed that Q goes up by a factor > 2 for modes beyond 27, as only a portion of the structure contributes to modal displacement. At higher voltages, thermal softening is observed due to local heating which results in structure behaving like a coupled resonator. Under these conditions, peak splitting is observed. This structure can be used in different sensor and actuator applications depending on the mode of operation.
  • No Thumbnail Available
    Item
    Influence of Slotting and Boss Radius on the Response of MEMS Based Intracranial Pressure Sensor
    (UPI Journals, 2018) Rao, Venkatesh K.P.
    In the present paper, we design a Microelectro- Mechanical System (MEMS) piezoresistive pressure sensor for intracranial pressure monitoring. The pressure sensor design presented in this paper consists of a square diaphragm. The slots were introduced to square diaphragm increases the stresses developed thus enhancing the sensitivity of the sensor In addition to slots, a central boss was introduced to enhance the sensitivity of the sensor. We carried out numerical simulation to evaluate the sensitivity of the sensor. Parametric studies were done to optimize the central boss radius to enhance the sensitivity of the sensor.
  • No Thumbnail Available
    Item
    Analysis of vibration based windmill coupled micromachined energy harvester
    (Vibroengineering Procedia, 2019-11) Rao, Venkatesh K.P.
    The present work exploits the centripetal, Coriolis and Euler forces generated in a rotating windmill. The MEMS device is placed on the blade of a windmill to harvest the energy. Modal analysis is carried out to optimize the dimensions of the structure to match the desired conditions. The real time response of the structure and the voltage generated in the piezoelectric layer are evaluated using transient analysis. It was noticed that Euler and Coriolis forces have a significant contribution in the initial time when the wind turbine accelerates from rest. The later portion is dominated by the Coriolis and Euler forces, and in some instances they cancel out each other. However, there is always a steady contribution from the centripetal force which is proportional to the magnitude of angular velocity of the wind turbine.
  • No Thumbnail Available
    Item
    Coupled Field Analysis of Hemispherical Resonator Gyroscope
    (International Journal of Vehicle Structures & Systems, 2022) Rao, Venkatesh K.P.
    This work deals with the electromechanical analysis of the Hemispherical Resonator Gyroscope (HRG). The HRG is a type of Coriolis vibratory gyroscope (CVG), which uses Coriolis force to measure the input angular rate. For any CVG drive and sense mode, frequencies play a critical role, which decides the sensitivity and bandwidth of a sensor. In this study, we carry out modal analysis to evaluate the natural frequencies and corresponding mode shapes of an HRG. As HRG is an electromechanical structure, the device is driven at resonance in the drive direction, and the Coriolis force leads to motion in the sense direction. In this study, we present the piezoelectric based HRG; coupled field simulations are carried out to evaluate the performance characteristics of a sensor
  • No Thumbnail Available
    Item
    Effect of external electric potential on the mechanical resonance of MEMS cantilever resonator
    (IOP, 2022-08) Rao, Venkatesh K.P.
    This work presents an analytical model to predict the natural frequency of electrostatically actuated micromachined cantilever beam under the application of DC voltage. The analytical modelling uses an energy based method with a sinusoidal vibration assumption. The electric field between the cantilever electrodes is assumed to be vertical and fringing field effects are neglected. The behaviour of natural frequency and a closed-form expression for pull-in voltage are evaluated. The electrostatic spring softening effect of DC bias on the resonant natural frequency is studied in particular. Results are compared with simulation in ANSYS.
  • No Thumbnail Available
    Item
    Design and Analysis of Single Drive Tri-Axis MEMS Gyroscope
    (Springer, 2022-11) Rao, Venkatesh K.P.
    MEMS based single and dual-axis gyroscopes have been widely explored for potential application in automotive, space, defense, and consumer electronics sectors. Tri-axis gyroscopes based on MEMS, however, have been sparsely studied. This work presents a novel design for tri-axis MEMS gyroscope and an analytical model to obtain the natural frequencies in drive and sense modes. These frequency values have been compared with the numerically obtained frequencies using Finite Element Analysis (FEA). The analytical results lie within 10% of their numerically obtained values. The frequency matching process involves many iterations of geometric dimensions if the end application requires minor design changes. The proposed analytical model will make the design customization easy as the frequencies of each mode will be expressed as a function of critical geometrical parameters saving multiple numerical runs required for design optimization.
  • No Thumbnail Available
    Item
    Modulating the Mechanical Resonance of Huh-7 Cells Based on Elasticity of Adhesion Proteins
    (IEEE, 2023-07) Rao, Venkatesh K.P.
    The atomic force microscope (AFM) has been used in cell biology for a decade. AFM is a unique tool for investigating the viscoelastic characteristics of live cells in culture and mapping the spatial distribution of mechanical properties, giving an indirect signal of the underlying cytoskeleton and cell organelles. Although several experimental and numerical studies were conducted to analyze the mechanical properties of the cells. We established the non-invasive Position Sensing Device (PSD) technique to evaluate the resonance behavior of the Huh-7 cells. This technique results in the natural frequency of the cells. Obtained experimental frequencies were compared with the numerical AFM modeling. Most of the numerical analysis were based on the assumed shape and geometry. In this study, we propose a new method for numerical AFM characterization of Huh-7 cells to estimate its mechanical behavior. We capture the actual image and geometry of the trypsinized Huh-7 cells. These real images are then used for numerical modeling. The natural frequency of the cells was evaluated and found to be in the range of 24 kHz. Furthermore, the impact of focal adhesion (FA’s) stiffness on the fundamental frequency of the Huh-7 cells was investigated. There has been a 6.5 times increase in the natural frequency of the Huh-7 cells on increasing the FA’s stiffness from 5 pN/nm to 500 pN/nm. This indicates that the mechanical behavior of FA’s leads to change the resonance behavior of the Huh-7 cell. Hence FA’s are the key element in controlling the dynamics of the cell. These measurements can enhance our understanding of normal and pathological cell mechanics and potentially improve disease etiology, diagnosis, and therapy choices. The proposed technique and numerical approach are further useful in selecting the target therapies parameters (frequency) and evaluating of mechanical properties of the cells.
  • No Thumbnail Available
    Item
    Design and Simulation of Tactical Grade Capacitive Based MEMS Vibratory Ring Gyroscope
    (IEEE, 2023) Rao, Venkatesh K.P.
    MEMS Vibratory Ring Gyroscopes (VRGs) are highly sensitive owing to their in-plane symmetric structure that ensures mode matching. We present a VRG with Comb drive actuation that offers linearity in drive mode, and variable gap capacitive detection in sense mode provides a high-scale factor. The numerical analysis of the VRG is undertaken at atmospheric pressure. High linearity is observed between sense mode movement and change in capacitance, indicative of scale factor stability. It offers an operating range of more than 100 degrees per second (dps) and resolution of 0.002 dps. The VRG has been designed to suit the tactical grade mobility requirements of platform stabilization, robotics, and unmanned aerial vehicles.
  • No Thumbnail Available
    Item
    Mechanical microscopy of cancer cells: TGF-β induced epithelial to mesenchymal transition corresponds to low intracellular viscosity in cancer cells
    (AIP, 2023-09) Chowdhury, Rajdeep; Laskar, Inamur Rahaman; Rao, Venkatesh K.P.; Mukherjee, Sudeshna
    Viscosity is an essential parameter that regulates bio-molecular reaction rates of diffusion-driven cellular processes. Hence, abnormal viscosity levels are often associated with various diseases and malfunctions like cancer. For this reason, monitoring intracellular viscosity becomes vital. While several approaches have been developed for in vitro and in vivo measurement of viscosity, analysis of intracellular viscosity in live cells has not yet been well realized. Our research introduces a novel, natural frequency-based, non-invasive method to determine the intracellular viscosity in cells. This method can not only efficiently analyze the differences in intracellular viscosity post modulation with molecules like PEG or glucose but is sensitive enough to distinguish the difference in intra-cellular viscosity among various cancer cell lines such as Huh-7, MCF-7, and MDAMB-231. Interestingly, TGF-β a cytokine reported to induce epithelial to mesenchymal transition (EMT), a feature associated with cancer invasiveness resulted in reduced viscosity of cancer cells, as captured through our method. To corroborate our findings with existing methods of analysis, we analyzed intra-cellular viscosity with a previously described viscosity-sensitive molecular rotor-based fluorophore-TPSII. In parity with our position sensing device (PSD)-based approach, an increase in fluorescence intensity was observed with viscosity enhancers, while, TGF-β exposure resulted in its reduction in the cells studied. This is the first study of its kind that attempts to characterize differences in intracellular viscosity using a novel, non-invasive PSD-based method.
  • No Thumbnail Available
    Item
    Design and Analysis of General Purpose MEMS Accelerometer
    (KTH, 2007) Rao, Venkatesh K.P.
    Inertial sensors including accelerometers and gyroscopes play an important role in vibration sensing, health monitoring, automotive applications etc. Here we design, fabricate and characterize the set of accelerometers with natural frequencies varying from 8 to 18 kHz. The design is compatible with PolyMUMPs process and has an ease of integrability with the electronic circuits. The operating voltage of the sensor is less than 3.5 V and both the structural and electrode layers are in polysilicon. The user is given an option of choosing the accelerometer in terms of sensitivity and the working range of g (acceleration due to gravity) based on the need of the application. Analytical, Numerical and experimental studies are carried out to determine the sensitivity, frequency range, maximum measurable acceleration and the pull-in voltage of each device. Effect of residual stress on the static and dynamic response characteristics of the accelerometer has been explored and the effect of same on its sensitivity.