Ashwin A. Seshia

University of Cambridge

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Guillermo Sobreviela

University of Cambridge

Milind Pandit

Philips (United States)

Chun Zhao

State Key Laboratory on Integrated Optoelectronics

Yu Jia

State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering

Sijun Du

Delft University of Technology

Jize Yan

University of Southampton

Xudong Zou

Chinese Academy of Sciences

Cuong Do

VinUniversity

Adarsh Ganesan

Birla Institute of Technology and Science, Pilani - Dubai Campus

Joshua E.-Y. Lee

University of Technology Sydney

Cooperative Institutions

University of Cambridge

112

University of Leeds

Institute of Electrical and Electronics Engineers

École Polytechnique Fédérale de Lausanne

Ultrasonic Technologies (United States)

University of Waterloo

Centre National de la Recherche Scientifique

Drexel University

Chinese Academy of Sciences

Sorbonne Université

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Studying particulate adsorption by drying droplets on a microfabricated electro-acoustic resonator

Abhinav Prasad Ashwin A. Seshia Arthur T. Zielinski Markus Kalberer R. L. Jones

Microfabricated in-plane bulk acoustic resonators can be configured as gravimetric sensors wherein the mass of surface-bound species is transduced as a shift in the resonant frequency. Using this principle, we examine the adsorption of spherical polystyrene latex particles on the resonator surface by drying particulate laden droplets. Distribution of particles on the surface is governed by the coffee-ring effect which is correlated to the observed frequency response of the resonators. We also present an analytical approach to describe the spatial dependence of adsorbed mass on the induced frequency shift for square plate resonators which can be extended to model other resonator geometries.

Gravimetric analysis

Polystyrene

10.1109/eftf.2014.7331418

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Citations (7)

Manipulating Vibration Energy Confinement in Electrically Coupled Microelectromechanical Resonator Arrays

Journal of Microelectromechanical Systems (2010)

Pradyumna Thiruvenkatanathan J. Woodhouse Jize Yan Ashwin A. Seshia

This paper reports the first detailed experimental evidence of the phenomena of eigenvalue loci veering and vibration mode localization in microelectromechanical resonator arrays subjected to weak electroelastic coupling. A rapid but continuous interchange of the eigenfunctions associated with the eigenvalues is experimentally observed during veering as the variations in the eigenvalues are studied for induced stiffness variations on one of the coupled resonators. It is also noticed that the electrical tunability of the coupling spring constant in such microsystems enables a manipulation of the severity of modal interchange during veering and in consequence, the extent of energy confinement within the system. These results, while experimentally confirming the elastic behavior of such electrical coupling elements, also suggest that such microsystems provide a unique platform for investigating the general nature and properties of these dynamic phenomena under significantly weaker tunable coupling spring constants that are very difficult to implement in corresponding "macroscopic" systems.

Microsystem

Eigenfunction

10.1109/jmems.2010.2090501

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Citations (37)

On Weakly Coupled Resonant MEMS Transducers Operating in the Modal Overlap Regime

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control (2020)

Hemin Zhang Milind Pandit Jiangkun Sun Dongyang Chen Guillermo Sobreviela

Miniaturized physical transducers based on weakly coupled resonators have previously demonstrated the twin benefits of high parametric sensitivity and the first-order common-mode rejection of environmental effects. Current approaches to sensing based on coupled resonator transducers employ strong coupling where the modal overlap of the responses is avoided. This strong coupling limits the sensitivity for such mode-localized sensors that utilize an amplitude ratio (AR) output metric as opposed to tracking resonant frequency shifts. In this article, this limitation is broken through by theoretically and experimentally demonstrating the operation of the weakly coupled resonators in the weak-coupling (modal overlap) regime. Especially, a prototype microelectromechanical systems (MEMS) sensor based on this principle is employed to detect shifts in stiffness, with a stiffness bias instability of 10.3 μN/m (9.5 ppb) and a corresponding noise floor of 7.1 μN/m/ √Hz (6.8 ppb/ √Hz). The linear dynamic range of such AR readout sensors is first explored and found to be defined by the dynamic range of the secondary resonator. The proposed method provides a promising approach for high-performance resonant force and inertial sensors.

10.1109/tuffc.2020.3028567

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Citations (18)

An analytical formulation for phase noise in MEMS oscillators

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control (2014)

Deepak K. Agrawal Ashwin A. Seshia

In recent years, there has been much interest in the design of low-noise MEMS oscillators. This paper presents a new analytical formulation for noise in a MEMS oscillator encompassing essential resonator and amplifier nonlinearities. The analytical expression for oscillator noise is derived by solving a second-order nonlinear stochastic differential equation. This approach is applied to noise modeling of an electrostatically addressed MEMS resonator-based square-wave oscillator in which the resonator and oscillator circuit nonlinearities are integrated into a single modeling framework. By considering the resulting amplitude and phase relations, we derive additional noise terms resulting from resonator nonlinearities. The phase diffusion of an oscillator is studied and the phase diffusion coefficient is proposed as a metric for noise optimization. The proposed nonlinear phase noise model provides analytical insight into the underlying physics and a pathway toward the design optimization for low-noise MEMS oscillators.

Oscillator phase noise

10.1109/tuffc.2014.006511

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Citations (36)

A Single-Crystal-Silicon Bulk-Acoustic-Mode Microresonator Oscillator

IEEE Electron Device Letters (2008)

Joshua E.-Y. Lee Behraad Bahreyni Yong Zhu Ashwin A. Seshia

A timing reference incorporating a single-crystal-silicon micromechanical resonator with a quality factor of larger than one million and a resonant frequency of 2.18 MHz is demonstrated. The resonator is excited in the square extensional bulk acoustic mode at 4 mtorr, and it has been fabricated in a foundry SOI MEMS process. The silicon microresonator is adapted as a timing element for a precision oscillator with a measured short-term Allan deviation of 0.6 ppb.

Allan variance

Q factor

Crystal oscillator

10.1109/led.2008.2000643

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Citations (58)

Modal Coupling in Micromechanical Vibratory Rate Gyroscopes

IEEE Sensors Journal (2006)

A. Srikantha Phani Ashwin A. Seshia Moorthi Palaniapan Roger T. Howe J. Yasaitis

The authors present modeling approaches to describe the coupling of modes in a resonant vibratory rate gyroscope. Modal coupling due to off-diagonal stiffness and damping terms is considered. Three analytical modeling approaches are presented in the context of a $z$ -axis micromechanical vibratory rate gyroscope fabricated in an integrated polysilicon surface-micromachining process. The first approach is based on frequency-response analysis of the gyroscope output. The second approach takes the route of state-space-based system identification to identify the modal-coupling parameters. A third approach based on measured vibration data identifies the coupling parameters due to stiffness and damping. These three methods are then applied to predict the extent of displacement and force coupling between the drive and the sense axes of an existing device as a function of varying degrees of matching between the resonant frequencies associated with the drive and the sense modes. Experimental data show that as the resonant frequencies of the drive and sense modes are brought closer together, an improvement in overall resolution and scale factor of the device is obtained at the expense of an enhanced coupling of forces to displacements between the two axes and the onset of instability for an open-loop sensing implementation.

10.1109/jsen.2006.881432

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Citations (50)

IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society - Administrative Committee

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control (2013)

Pascal Laugier Dan Stevens Ashwin A. Seshia

The Ultrasonics, Ferroelectrics, and Frequency Control Society is an organization, within the framework of the IEEE, of members with principal professional interest in ultrasonics, ferroelectrics, and frequency control.The scope of interest of the Society shall include the theory, technology, materials, and applications relating to: (1) the generation, transmission, and detection of mechanical waves and vibrations and their interactions with other phenomena; (2) medical ultrasound, including hyperthermia, bioeffects, tissue characterization and imaging; (3) ferroelectric, piezoelectric, and piezomagnetic materials, including crystals, polycrystalline solids, films, polymers, and composites; (4) frequency control, timing and time distribution, including crystal oscillators and other means of classical frequency control, and atomic, molecular, and laser frequency control standards.Areas of interest range from fundamental studies to the design and/or applications of devices and systems within the general scope defined above.

10.1109/tuffc.2013.2761

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A microfluidic device for the hydrodynamic immobilisation of living fission yeast cells for super-resolution imaging

Sensors and Actuators B Chemical (2013)

Laurence L. Bell Ashwin A. Seshia David Lando Ernest D. Laue Matthieu Palayret

We describe a microfluidic device designed specifically for the reversible immobilisation of Schizosaccharomyces pombe (Fission Yeast) cells to facilitate live cell super-resolution microscopy. Photo-Activation Localisation Microscopy (PALM) is used to create detailed super-resolution images within living cells with a modal accuracy of >25 nm in the lateral dimensions. The novel flow design captures and holds cells in a well-defined array with minimal effect on the normal growth kinetics. Cells are held over several hours and can continue to grow and divide within the device during fluorescence imaging.

Schizosaccharomyces

Live cell imaging

Fluorescence-lifetime imaging microscopy

10.1016/j.snb.2013.10.002

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Citations (37)

Seismic Recording Using A Mode Localized MEMS Accelerometer

Milind Pandit Chun Zhao Guillermo Sobreviela Xudong Zou Ashwin A. Seshia

This paper reports the first demonstration of a mode localized resonant accelerometer (MLRXL) as a seismometer. The prototype sensor demonstrates a noise floor of 4.5μg/√Hz at a defined operating point corresponding to an amplitude ratio of 1.22. The device situated in Cambridge, UK recorded an earthquake of magnitude 3.8 with the epicenter at Grimsby, UK on the 9th of June, 2018. This measurement demonstrates the potential for mode localized MEMS accelerometers to be utilized for seismic applications with comparable performance to existing seismometers, with particular relevance to long-period measurements.

Seismometer

Epicenter

Mode (computer interface)

10.1109/transducers.2019.8808572

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Citations (5)

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control Society

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control (2013)

Pascal Laugier Dan Stevens Ashwin A. Seshia

10.1109/tuffc.2013.2730

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Citations (0)