Ferroelectrics are essential components in a wide range of applications, including ultrasonic transducers, sensors, and actuators. In the single crystal form, relaxor-PbTiO3 (PT) piezoelectric materials have been extensively studied due to their ultrahigh piezoelectric and electromechanical properties. In this article, a perspective and future development of relaxor-PT crystals are given. Initially, various techniques for the growth of relaxor-PT crystals are reviewed, with crystals up to 100 mm in diameter and 200 mm in length being readily achievable using the Bridgman technique. Second, the characterizations of dielectric and electromechanical properties are surveyed. Boundary conditions, including temperature, electric field, and stress, are discussed in relation to device limitations. Third, the physical origins of the high piezoelectric properties and unique loss characteristics in relaxor-PT crystals are discussed with respect to their crystal structure, phase, engineered domain configuration, macr...

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High performance ferroelectric relaxor-PbTiO3 single crystals: Status and perspective

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

Systems including an implantable receiver-stimulator and an implantable controller-transmitter are used for leadless electrical stimulation of body tissues. Cardiac pacing and arrhythmia control is accomplished with one or more implantable receiver-stimulators and an external or implantable controller-transmitter. Systems are implanted by testing external or implantable devices at different tissue sites, observing physiologic and device responses, and selecting sites with preferred performance for implanting the systems. In these systems, a controller-transmitter is activated at a remote tissue location to transmit/deliver acoustic energy through the body to a receiver-stimulator at a target tissue location. The receiver-stimulator converts the acoustic energy to electrical energy for electrical stimulation of the body tissue. The tissue locations(s) can be optimized by moving either or both of the controller-transmitter and the receiver-stimulator to determine the best patient and device responses.

Leadless tissue stimulation systems and methods

Probing Systems in Dimensional Metrology

Method and systems for optimizing acoustic energy transmission in implantable devices are disclosed. Transducer elements transmit acoustic locator signals towards a receiver assembly, and the receiver responds with a location signal. The location signal can reveal information related to the location of the receiver and the efficiency of the transmitted acoustic beam received by the receiver. This information enables the transmitter to target the receiver and optimize the acoustic energy transfer between the transmitter and the receiver. The energy can be used for therapeutic purposes, for example, stimulating tissue or for diagnostic purposes.

Optimizing energy transmission in a leadless tissue stimulation system

A small-scale positioning device employing a platform, a levering mechanism and a floating actuator device The platform is movably attached to a fixed frame by a lever, a pair of levers, or more The floating actuator device is coupled between at least one lever and the platform When the actuator device is activated, it generates a force on the platform and an equal but opposite force on the levering mechanism, causing one or more levers to rotate around their respective fulcrums, thereby controlling the position of the movable platform relative to the fixed frame The amount of displacement of the platform is dependent upon the effective expansion or contraction of the actuator device and the lever ratio If the pair of levers are symmetrical, then motion is created in only a single degree of motion Flexures may be included to prevent motion in unwanted directions

Positioning device employing a platform, levering mechanism and floating actuator device

This paper presents a comparative study of digital methods to improve the signal to noise ratio in ac bridge measurements and other applications requiring demodulation of amplitude-modulated signals. Three types of discrete Fourier transform (DFT) based algorithms are analyzed. The algorithms considered are single-sine conventional DFT, single-sine running DFT, and multi-sine running DFT. We report on a case study using a field programmable gate array (FPGA) to monitor the output signal from a typical ac bridge with variable capacitive sensors in two arms. Theoretically, both the single- and multi-sine running DFT algorithms are shown to provide improved ripple noise performance over the conventional single-sine DFT approach. Additionally, in the presence of a high noise background, theoretical calculations indicate that the multi-sine running DFT provides a factor of 2 improvement in signal to noise ratio compared to the single-sine conventional DFT. Experimental results also show a moderate improvement in ripple noise, but not at the level predicted by the theory. Finally, the method for running multi-sine reported can be used for any periodic basis function. As a result, higher complex basis functions, particularly those with orthogonal properties, such as those that can be generated from a Fourier series or functions that contain continuous spectra (wavelets for example), could also be used.

Single- and multi-sine DFT demodulation with an application to precision capacitive sensors

Fiber-coupled 3-DOF interferometer for euv lithography stage metrology

This paper presents researches into the application of energy absorbing foams as a passive damping medium to enhance the controllability for fast steering (tip-tilt) of lightweight mirrors. The direct relationship between passive damping and control highlights the merits of energy absorbing foams that have shown significant attenuation in high mode resonant frequencies (typically above 1 kHz) without adding significant mass. Studies by these researchers suggest that attenuation is coupled to standing waves through the foam. In this case study these foams have been applied to a 300 mm diameter aluminum platen that represents the final mirror geometry. In practice,mirrors for our application will be made from silicon carbide. The platen is designed with an open-back honeycomb structure and high-speed machined from 6160-T7 aluminum. Three dominant mode shapes were observed at approximately 1140,1350 and 2100 Hz with high ‘Q’. In general,the platen or any adaptive structure may require high-bandwidth dynamic control. Fundamentally,the high ‘ Q’ values limit the control dynamics. This paper shows the benefits of energy absorbing foams as a passive damping medium for large lightweight structures. The foams are strategically placed inside the honeycomb pockets at the back of the mirror and experimental investigations demonstrate damping coefficients up to x ¼ 0:12 (factor of 60 improvement) compared to a x� 0:002 with no added passive damping in the system. Furthermore,the energy absorbing foam only adds 6% additional mass to the overall lightweight platen. As a result of this high damping coefficient,the Q values were attenuated by 25–50 dB for all high-frequency modes and as a result the controller parameters (i.e. such as

Shane C. Woody

Papers

Positioning device employing a platform, levering mechanism and floating actuator device

Single- and multi-sine DFT demodulation with an application to precision capacitive sensors

Fiber-coupled 3-DOF interferometer for euv lithography stage metrology

Short Communication Damping of a thin-walled honeycomb structure using energy absorbing foam

Compact six degree-of-freedom interferometer for precision linear stage metrology