BITS Faculty Publications

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Author: search.filters.author.Rao, Venkatesh K.P.

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    Modeling and simulation of a high sensitivity mems tuning fork gyroscope
    (IEEE, 2024-04) Rao, Venkatesh K.P.
    MEMS Gyros are the emerging technology for sensing angular motion of the platform they are installed on. The biggest advantages they offer is their low size, weight, cost and power consumption. In this paper we present a mode matched MEMS Tuning Fork Gyro (TFG) which offers high sensitivity and resolution. The frequency separation between drive and sense modes is only 14Hz. The TFG displays a sensitivity of 924pm/dps and a resolution of 0.001 dps. This MEMS TFG offers high sensitivity, resolution and immunity from external vibrations, which makes it a suitable choice for any device that needs to measure and control angular motion in industrial, medical, automotive, aerospace or defence sector applications.
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    Design and fabrication of single drive tri-axis MEMS gyroscope
    (Elsevier, 2024-03) Rao, Venkatesh K.P.
    Gyroscopes are sensors that measure the angular rate of an rotating object along one or more coordinate axis. For measuring angular rate along all three axes, usually three different single axis gyroscopes are used. Three sensor systems imply more space and power requirements which are precious commodities in microelectronics. Single-drive tri axis gyroscopes overcome this issue. Owing to their design complications, they have not been explored to the scale of the single axis gyroscopes. In this paper we present a novel design of single drive tri-axis MEMS gyroscope with detail explanation of its working principle. Since gyroscopes are resonant sensors, the natural frequencies of drive and sense modes are expected to be as close to each other as possible to ensure maximum sensitivity. These frequencies depend on the structural dimensions of the design. A design optimization procedure using Finite Element Method (FEM) based parametric modal analysis has been suggested in order to achieve mode matching. An equivalent analytical model is also presented for drive mode and all three sense modes. The optimized design is fabricated using modified silicon on glass bulk micromachining technique. The natural frequencies in drive and sense modes of as fabricated devices were measured and compared with the numerical and analytical values, The experimental values of frequencies are well within 16% of the numerical values. A design upgrade has been suggested to further reduce this error value.
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    Coupled field simulation of mems tuning fork gyroscope
    (Springer, 2025-06) Rao, Venkatesh K.P.
    The use of Microelectromechanical Systems (MEMS) based sensors has become increasingly popular due to the growing demand for miniaturization in electronics. Though developing these sensors may require multiple iterations on smaller samples, Finite Element Method (FEM) based simulations offer a viable solution by enabling the optimization of design parameters to a significant degree. A FEM based simulation methodology has been designed in this paper to incorporate electromechanical coupling in an electrostatically actuated tuning fork gyroscope using COMSOL Multiphysics. The simulation results have been compared with analytical values and an existing simulation example that combines numerical and analytical approaches. The obtained sense mode displacement values predicted by the model lie within 5% of the analytically predicted values and the values predicted by the simulation example.
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    Influence of nanocarrier additives on biomechanical response of a rat skin
    (IEEE, 2024-10) Rao, Venkatesh K.P.; Singhvi, Gautam
    Skin health monitoring focuses on identifying diseases by assessing the mechanical properties of the skin. These properties may degrade with time, which can alter the skin’s natural frequencies and the modeshapes associated with those frequencies. Exploring the skin’s mechanical properties can enhance our understanding of its dynamics, improving clinical trials and diagnostics. In this work, the dynamics of the skin were measured using a laser-based non-invasive optical sensor experiment. We measured the skin’s mechanical properties over time by analyzing its resonant frequencies and mode shapes. A nanocarrier gel and ketoconazole cream were topically applied to keep the skin hydrated and facilitate deeper penetration of the additives in the skin. Time-based research was used to assess the effect of different formulations on skin elasticity. Experimental results for the modulus of elasticity were compared with those obtained using Finite Element Analysis (FEA) simulations. We observed a reduction in frequencies of cream and gel-treated skin by 29.98% and 44.029%, respectively, compared to normal skin (frequency: 263.3±1.18 Hz and Modulus of elasticity: 7.56±2.60 MPa). A decrease in stiffness is attributed to increased water content, was observed in cream- and nanocarrier gel-treated skin compared to normal skin. Experimental and numerical results are found to be consistent with one another. This optical sensor-based approach has the potential for studying diseased skin mechanics and its response to gel and cream treatments, aiming to reduce skin disorder morbidity and severity.
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    Unlocking the potential of photodynamic therapy in Psoriasis: Mechanistic insights, wide-ranging applications, challenges and future directions
    (Elsevier, 2025-10) Rao, Venkatesh K.P.; Jain, Ankit; Rao, Venkatesh K.P.
    Psoriasis is an autoimmune skin disorder involving the interaction of genetic factors and environmental stress which leads to uncontrolled proliferation of keratinocytes and activation of the immune system. Conventional treatment options, including topical therapies, phototherapy, systemic drugs, and biologics, are used based on disease severity. Recently, photodynamic therapy (PDT) has gained attention due to its unique advantages over traditional treatments. PDT relies on three key components i.e. photosensitizer (PS) administered either locally or systemically, specific light irradiation, and molecular oxygen to generate reactive oxygen species (ROS), leading to the damage of photoactivated cells through cellular apoptosis and necrosis. Recent studies have explored innovative PSs and delivery strategies to enhance the efficacy of PDT in psoriasis. Emerging research highlights the potential of PDT to suppress keratinocyte proliferation and modulate inflammatory pathways, such as JAK/STAT inhibition via ROS-mediated upregulation of SOCS1/3. Innovative delivery strategies and photosensitizers, including chlorin e6, IR820, ZnPc-F7, and 5-aminolevulinic acid (ALA), have been developed to enhance selectivity, reduce treatment-associated discomfort, and improve skin penetration. Nanocarrier systems, such as mesoporous silica nanoparticles, polydopamine-based platforms, and lipid-based nanocarriers, have enabled synergistic photochemotherapy and dual photothermal-photodynamic approaches, leading to improved therapeutic outcomes by inducing apoptosis, restoring skin barrier function, and attenuating proinflammatory signaling. This review highlights PDT principles, mechanisms, approved PSs, and emerging combinations. Despite its promising effects, PDT remains underutilized in psoriasis, demanding further research and nanotech-driven optimization for patient-friendly therapies.
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    Influence of electric potential boundary condition on the electrospraying process
    (Elsevier, 2025-08) Rao, Venkatesh K.P.; Yadav, Shyam Sunder
    In the current work, we perform three dimensional numerical simulations of the electrospraying process. Our aim is to investigate the effect of electric potential boundary condition on the electrospraying process of a liquid. We observe a steady electrospraying process in the cone jet mode for the case of uniform electric potential boundary condition. On the other hand, we observe a highly unsteady, violent electrospraying process for the case of non-uniform boundary condition. We provide explanation of this widely different behavior of the electrospraying process.
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    A three-dimensional open-source solver for incompressible viscoelastic two-component flows
    (ASME, 2025-10) Rao, Venkatesh K.P.; Yadav, Shyam Sunder
    In this study, we unveil a three-dimensional flow solver designed to simulate viscoelastic two-phase flows using the Oldroyd-B formulation. Acknowledging the challenges that researchers encounter in this dynamic field, we have integrated the three-dimensional Log conformation approach into the open-source flow solver basilisk, significantly enhancing its capabilities beyond its two-dimensional predecessors. Our solver stands as a testament to rigorous testing against a wide range of three-dimensional viscoelastic flow challenges, encompassing both single and two-phase scenarios drawn from established literature. True to its two-dimensional roots, it exhibits extraordinary robustness, adeptly managing viscoelastic flows, even at high Weissenberg numbers. By offering this powerful solver as an open-source resource, we aspire to empower the computational fluid dynamics community. We believe it will become an invaluable tool for researchers delving into the complexities of viscoelastic flows, fostering innovation and inspiring new progress in the field.
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    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.
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    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.
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    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.