Mark Sheplak

University of Florida | UF · Departments of Mechanical and Aerospace Engineering & Electrical and Computer Engineering

View Video Presentation: https://doi.org/10.2514/6.2021-2131.vid This paper describes the development and experimental characterization of a flush-mount aeroacoustic microphone designed for through-wall installation. The aluminum nitride piezoelectric microelectromechanical systems (MEMS) sensor is fabricated using a novel, low-cost approach to cre...

This paper describes the development and experimental characterization of a temperature-compensated wall shear stress sensor system designed to reduce temperature sensitivity and be non-invasive to low-speed aerodynamic flows. The differential capacitive microelectromechanical systems (MEMS) sensor is fabricated using a novel, low-cost approach to...

This paper presents the first realization of a fiber-optic lever-based, miniature five-hole probe (5HP) for aerodynamic flow angle sensing applications. Five MEMS optical transducers are embedded in a hemispheric probe tip to mitigate the pneumatic lag problem of conventional 5HP technology. A silicon die with five optical pressure transducers of 4...

This paper presents the fabrication, packaging, and calibration of a flush-mounted, dual-axis, differential capacitive wall shear stress sensor. The two-mask fabrication process produces a 7-mm die with a 2-mm by 2-mm floating element supported by eight, compliant crab-leg tethers. Taking advantage of backside wire bonds, the hydraulically smooth p...

Synchronous stereo particle image velocimetry (PIV) and fluctuating wall shear stress measurements were performed in a moderate Reynolds number zero pressure gradient turbulent boundary layer. Multiple, discrete PIV planes allow for a reconstruction of the wall shear stress-streamwise velocity cross correlation in a volume around the sensor. The ve...

This experimental work studies the impact large scale motions in a zero pressure gradient turbulent boundary layer have on the fluctuating streamwise wall shear stress component using a recently developed 1×1mm2 floating element differential capacitive shear stress sensor. The sensing system allows for a flat band response with a bandwidth up to 1....

Background Pharyngeal swallowing power (PSP) is a novel measure of pharyngeal bolus‐driving function derived from fluid dynamics principles. This study examined the impact of bolus volume and viscosity on PSP to determine bolus effects on pharyngeal bolus dynamics. The impact of bolus accommodation and physical characteristics of boluses were also...

One of the most prevalent materials used in sensor technologies is silicon which suffers degradation in operating regimes that exceed 1000 °C unless the sensor is actively cooled. Substitution of silicon with sapphire in pressure sensors offers unique capabilities due to its high melting point and chemical inertness; however, these same properties...

Background The primary function of the pharyngeal swallowing mechanism is to drive ingested materials into the esophagus. Currently, a definitive measure of pharyngeal bolus‐driving function that accounts for bolus movement remains lacking. The primary objectives of this study were to describe the derivation of a novel biofluid dynamics measure of...

In the above paper [1] , references [46] and [54] were cited incorrectly. The corrected references are as follows.

A microelectromechanical systems (MEMS) capacitive-type passive wireless pressure sensor designed to operate in harsh environments at temperatures up to 1000 °C is presented. The pressure sensor has a sapphire-based diaphragm and structural body, and a platinum-based capacitive element. The capacitive element is configured as a part of a slot patch...

In support of Topic A.2.8 of NASA NRA NNH10ZEA001N, the University of Florida (UF) has investigated the use of flow field optical diagnostic and micromachined sensor-based techniques for assessing the wall shear stress on an acoustic liner. Stereoscopic particle image velocimetry (sPIV) was used to study the velocity field over a liner in the Grazi...

This talk presents the development of several microelectromechanical systems (MEMS)-based acoustic transducer technologies for fluid mechanics and aeroacoustics applications. Specifically, this presentation will focus on several aluminum nitride piezoelectricMEMS dynamic pressure sensors and microphones. These devices offer the promise of reducing...

Many piezoelectric microelectromechanical systems (MEMS) measure or generate acoustic signals via the motion of radially non-uniform, thin film composite plates. The composite layers provide piezoelectric actuation, structural support, electrode metallization, passivation, etc. Often, the layers are non-uniform over the plate and contain residual s...

A large scale spatio-temporally periodic disturbance was excited in a turbulent boundary layer via a wall-actuated dynamic roughness. Streamwise velocity, wall pressure, and direct wall shear stress measurements were made with a hot wire, pressure microphone, and a micro-scale differential capacitive sensor, respectively. Phase-averaged fields for...

The scanning probe microscope has revolutionized our ability to image and characterize the physical and chemical properties of material with atomic resolution. It has evolved as a versatile instrument for nanofabrication including atomic deposition, nanolithography, nanomachining, atomic manipulation, and assembly. However, in order to enable pract...

This paper presents the development of the first sapphire micromachined wall shear stress sensor for high-temperature applications utilizing geometric moire optical transduction. A folded tether floating element structure is employed to extend the linear operating range of the sensor. Picosecond pulsed laser micro-machining processes are developed...

A laser-generated plasma acoustic point source is used to directly measure the point spread function (PSF) of a microphone phased array. In beamforming analysis of microphone phased array data, the true acoustic field is convolved with the array׳s PSF. By directly measuring the PSF, corrections to the array analysis can be computed and applied. The...

The focus of this chapter is on micromachined implementations of acoustic energy harvesters (AEHs); however, mesoscale devices will also be discussed in depth to provide a historical and technical background to the field. The chapter begins with a historical introduction to the field, providing an overview of devices, applications, and approaches....

Sensing of pressure at high temperatures is currently limited by melting temperature and the plastic deformation undergone by silicon based technologies due to brittle to ductile transition.1 Sapphire has been proposed as an alternative sensing material that can overcome these temperature limitations using photonic methods. In order to manufacture...

This paper presents the fabrication, packaging, and characterization of a sapphire optical pressure sensor for hightemperature applications. Currently available instrumentation poses significant limitations on the ability to achieve realtime, continuous measurements in high-temperature environments such as those encountered in industrial gas turbin...

We report the development of a time-resolved direct wall shear stress senor using an optical moiré transduction technique for harsh environments. The floating-element sensor is a lateral-position sensor that is micromachined to enable sufficient bandwidth and to minimize spatial aliasing. The optical transduction approach offers several advantages...

This paper describes the development of a shear stress sensor for use in harsh environments as well as experimental characterization of the sensor system. The microelectromechanical systems (MEMS) sensor utilizes optical moiré transduction of a floating element structure created using a silicon-on-Pyrex fabrication process. Interrogation of the amp...

A capacitive microphone and method of fabricating the same are provided. One or more holes can be formed in a first printed circuit board (PCB). A diaphragm can be surface micro-machined onto an interior surface of the first PCB at a region having the one or more holes. Interface electronics can also be interconnected to the interior surface of the...

In this paper, the development and use of acoustic energy harvesting technology as a source of local power for aeroacoustic sensing and control applications is discussed. As an example, the application of acoustic energy harvesting as a primary local power source for aircraft engine noise reduction technology is addressed. Noise generated in turbof...

Nomenclature C aC = acoustic compliance of cavity C aD = acoustic compliance of diaphragm G = gyrator constant L eCoil = electrical coil inductance M aD = acoustic mass of diaphragm M aN = acoustic mass of neck M aRad = acoustic radiation mass Q C = volumetric flow velocity of cavity compression and expansion Q D = total volumetric flow velocity ge...

This paper describes the design and characterization of a micromachined microphone for aircraft fuselage arrays utilized by aeroacousticians to help identify aircraft noise sources and/or assess the effectiveness of noise-reduction technologies. The developed microphone utilizes piezoelectric transduction via an integrated aluminum nitride layer in...

The process dependence of 1/f noise in p-type piezoresistors was investigated in this work using both electrical and materials characterization approaches. P-type piezoresistors were fabricated with 20 keV and 40 keV boron implants with and without implant oxide and varying isochronal 900 °C inert anneals. The devices were characterized electricall...

This work presents the modeling, fabrication, and experimental analysis of a compact (33 cm(3), 91 g) electrodynamic zero-net mass-flux (ZNMF) actuator for flow control applications. The electrodynamic actuation scheme employs a magnetic assembly to establish a radial magnetic field pattern with an imbedded current-carrying coil winding. The coil i...

This paper presents technology development toward the goal of a micromachined acoustic proximity sensor for real-time cavity monitoring of underwater high-speed supercavitating vehicles. Low-resistance polysilicon-based through-silicon vias (TSVs) have been integrated with the device to enable backside contacts for drive and sense circuitry. The se...

This paper describes the development of a micro- machined microphone for aircraft fuselage arrays that are utilized by aeroacousticians to help identify aircraft noise sources and/or assess the effectiveness of noise-reduction technologies. The developed microphone utilizes piezoelectric transduction via an integrated aluminum nitride layer in a th...

Many micromachined electroacoustic devices use thin plates in conjunction with electrical components to measure acoustic signals. Composite layers are needed for electrical passivation, moisture barriers, etc. The layers often contain residual stresses introduced during the fabrication process. Accurate models of the composite plate mechanics are c...

The Capon Beamforming algorithm is an optimal spatial filtering algorithm used in various signal processing applications where excellent interference rejection performance is required, such as Radar and Sonar systems, Smart Antenna systems for wireless communications. Its lack of robustness, however, means that it is vulnerable to array calibration...

This paper describes the motivation, packaging, and preliminary experimental results for a new passive microelectromechanical systems (MEMS)-based aeroacoustic microphone. The passive technology utilized - piezoelectric transduction, with aluminum nitride serving as the piezoelectric material - together with the small size make this microphone idea...

This article describes a mathematical model and solution methodology for efficiently predicting the many equilibrium paths of an arbitrarily-shaped, pre-curved, clamped beam subjected to arbitrary dead loading. Such structures are common among multistable microelectromechanical systems (MEMS), and the presented model provides designers with an easy...

This paper presents the design, fabrication, and characterization of a passive wireless sensor for the measurement of wall shear stress. A micromachined variable-capacitor shear stress transducer is realized using a silicon-on-Pyrex microfabrication process. The design features a diamond-shaped 2.25 mm2 silicon floating-element to accommodate more...

A novel suite of parameter extraction experiments were used to assess the accuracy of individual elements of a lumped element model for a microelectromechanical systems based piezoelectric microphone. The MEMS microphone was developed via model-based design utilizing the lumped element model for use in aeroacoustic applications. Laser vibrometer sc...

In this paper, the development of a first generation MEMS-based piezoelectric energy harvester capable of converting ambient vibrations into storable electrical energy is presented. The energy harvester is designed using a validated analytical electromechanical Lumped Element Model (LEM) that accurately predicts the behavior of a piezoelectric comp...

This paper presents the development of a floating-element-based capacitively sensed direct wall-shear-stress sensor intended for measurements in a turbulent boundary layer. The design principle is presented, followed by details of the fabrication, packaging, and characterization process. The sensor is designed with an asymmetric comb finger structu...

Capon Beamforming algorithm is an optimal spatial filtering algorithm used in various signal processing applications where excellent interference rejection performance is required, such as Radar and Sonar systems, Smart Antenna systems for wireless communications. Its lack of robustness, however, means that it is vulnerable to array calibration err...

This paper presents the preliminary wind tunnel characterization of a microelectromechanical systems (MEMS)-based capacitive floating element shear stress sensor. The floating element structure incorporates interdigitated comb fingers forming differential capacitors, which provide electrical output proportional to the floating element deflection. A...

Microphone arrays can be used to localize and estimate the strengths of acoustic sources present in a region of interest. However, the array measurement of a region, or beam map, is not an accurate representation of the acoustic field in that region. The true acoustic field is convolved with the array's sampling response, or point spread function (...

This paper presents a reduced analytical modeling method for the initial optimal design of thermoelastic micromachined actuators. The key aspects of the model are a Green’s function formulation of the axisymmetric heat conduction equation that incorporates an internal heat source and the solution of the thermoelastically forced bending wave equatio...

A piezoelectric micromachined ultrasonic radiator was developed using aluminum nitride (AlN) for air-coupled applications. A commercially proven CMOS-compatible fabrication process was leveraged to form the devices. The transducer design consists of a radially nonuniform circular composite diaphragm with an integrated layer of AlN between two annul...

Phased arraybeamforming is commonly applied to assess the spatial distribution of noise sources in aeroacousticwind tunneltesting, generally with planar microphone arrays. As classically applied with a conventional beamforming algorithm, results can suffer contamination due to cross?flow over the array face in the wind tunnel test environment. When...

Phased microphone arrays are useful tools for noise source localization using a process known as beam‐forming. In scale‐model wind tunnel experiments, the frequency range of interest can extend as high as 90 kHz. In both open and closed wall wind tunnels,microphones with high dynamic range are required to sense large turbulentpressurefluctuations f...

Actuators are transducers that convert an electrical signal to a desired physical quantity. Active flow control actuators modify a flow by providing an electronically controllable disturbance. The field of active flow control has witnessed explosive growth in the variety of actuators, which is a testament to both the importance and challenges assoc...

This paper describes the design, fabrication, and measurement of silicon v-grooves used to position optical fibers in micro-sensors Three designs were selected, produced, and assembled (10 sets each). Images were analyzed to determine the v-groove dimensions and fiber center locations. While the fibers were positioned accurately in the X direction...

Wall shear stress or skin friction causes a significant amount of drag in an aerodynamic system. As a result, measurements are extremely important for efficient and effective aerodynamic design as well as fundamental understanding of the underlying flow physics. This measurement is also important for a wide variety of applications ranging from feed...

This paper describes the packaging and characterization of micromachined piezoelectric microphones designed as aircraft fuselage instrumentation for full-scale noise characterization flight tests. An important requirement for such microphones is a high maximum sound pressure level (SPL) >150 dB coupled with noise floor <45 dB SPL (narrow bin) and f...

This paper describes the fabrication and characterization of a sapphire based fiber optic microphone designed for the harsh environment of gas turbine engines. The performance requirements are driven by turbine inlet temperatures that have risen in excess of 1500 °C. The harsh environment makes conventional instrumentation unsuitable for time-accur...

A method for the direct measurement of the pressure sensitivity of a microelectromechanical system (MEMS) microphone is developed for frequencies from 10 to 100 kHz. The use of a simultaneous pressure field measurement reduces the errors in calculating the pressure sensitivity from free field measurements, and it allows calibration of non-reciproca...

A microelectromechanical systems (MEMS)-based capacitive floating element shear stress sensor, developed for time-resolved turbulence measurement, is studied for its response to unsteady pressure forcing. The floating element structure incorporates interdigitated comb fingers forming differential capacitors, which provide electrical output proporti...

A miniaturized optical package was developed for a floating-element shear stress sensor that permits the direct measurement of skin friction based on geometric Moiré interferometry. Aluminum gratings are placed on a silicon floating element and a Pyrex support structure to generate a Moiré fringe pattern, which is used to optically amplify the floa...

The development of a piezoelectric micromachined ultrasonic radiator is presented. The transmitter is formed by a radially non‐uniform circular composite diaphragm. The diaphragm consists of a layer of piezoelectric material with annular electrodes. Transduction of the diaphragm occurs when an electric field is induced between annular electrodes ac...

The paper presents a direct, capacitive shear stress sensor with performance sufficient for time-resolved turbulence measurements. The device employs a bulk-micromachined, metal-plated, differential capacitive floating-element design. A simple, two-mask fabrication process is used with DRIE on an SOI wafer to form a tethered floating element struct...

The eduction of the acoustic impedance for liner configurations is fundamental to the reduction of noise from modern jet engines. Ultimately, this property must be measured accurately for use in analytical and numerical propagation models of aircraft engine noise. Thus any standardized measurement techniques must be validated by providing reliable...

We report our investigation on electroosmotic flow (EOF) in a wavy channel between a plane wall and a sinusoidal wall. An exact solution is obtained by using complex function formulation and boundary integral method. The effects of the channel width and wave amplitude on the electric field, streamline pattern, and flow field are studied. When a pre...

This research plans to develop enhanced contrast thermal acoustic imaging (TAI) technology for the detection of breast cancer by combining amplitude-modulated (AM) electromagnetic (EM) field excitation, resonant acoustic scattering, and advanced signal processing techniques. While EM-induced TAI possesses great promise, the thermal acoustic signals...

This paper demonstrates the system operation of a self-powered active liner for the suppression of aircraft engine noise. The fundamental element of the active liner system is an electromechanical Helmholtz resonator (EMHR), which consists of a Helmholtz resonator with one of its rigid walls replaced with a circular piezoceramic composite plate. Fo...

A microelectromechanical systems (MEMS)-based capacitive floating element shear stress sensor, developed for time-resolved turbulence measurement, is dynamically characterized via Stokes layer excitation. The floating element structure incorporates interdigitated comb fingers forming differential capacitors, which provide electrical output proporti...