In this paper, we present the ultrasonic wireless power transmission system as part of a brain-machine interface (BMI) system in development to supply the required electric power. Making a small-size implantable BMI, it is essential to design a low power unit with a rechargeable battery. The ultrasonic power transmission system has two piezoelectric transducers, facing each other between skin tissues converting electrical energy to mechanical vibrational energy or vice versa. Ultrasound is free from the electromagnetic coupling effect and medical frequency band limitations which making it a promising candidate for implantable purposes. In this paper, we present the design of piezoelectric composite transducer, the rectifier circuit, and rechargeable battery that all packaged in biocompatible titanium can. An initial prototype device was built for demonstration purpose. The early experimental results demonstrate the prototype device can reach 50% of energy transmission efficiency in a water medium at 20mm distance and 18% in animal skin tissue at 18mm distance, respectively.
Polyvinylidene difluoride (PVDF) is a piezoelectric polymer with a low-cost, high flexibility and biocompatibility that is
suitable for various energy conversion applications between the electrical and mechanical forms of energy. One of the
novel techniques to create PVDF fibers is electro-spinning. In the present work, the above technique has been applied to
develop electro-spun thin-film based on PVDF with the use of high electric field and a high-frequency mechanical
vibratory motion as an electro-spinning setup. The high-frequency vibratory motion is used to create effective fluid
viscous forces to achieve a localized fluid spreading and thinning behavior of extremely thin polymer fiber solution.
We report on the production of thin films of titanium nickelides (TiNi) shape memory alloy, prepared via Current-
Activated Tip-based Sintering (CATS), a new localized powder sintering process. Mechanically alloyed equi-atomic
TiNi powder was tip-sintered at varying currents and cycles of current exposure time. The effect of processing
conditions on the developed localized microstructure and properties are discussed. The number of cycles of current
exposure time and current magnitude were studied. Both number of cycles and current magnitude in general result in an
increase micro-hardness and a reduction in residual porosity in the sintered thin films.
This paper compares frequency measurements in lead magnesium niobate-lead titanate (PMN-PT) resonators with
conventional quartz crystal microbalance (QCM) resonators when exposed to acetone vapors under identical test
conditions. A pumpless mechanism for driving acetone vapors by convection force was developed in our experimental
setup. The frequency shift recorded in response to acetone vapor exposure for the PMN-PT resonator was more than
10,000 times larger than for the QCM resonator. Our experimental results reinforce the notion that PMN-PT resonators
could be a superior replacement for QCM resonators in a variety of biosensor applications. The experimental setup
heated water to produce acetone vapors, a volatile organic chemical, which were delivered to a sensing chamber to
interact with the sensing unit. Chemical vapors were driven toward the sensing unit and circulated through the system via
a pumpless mechanism by the principle of convection. Both types of resonators displayed a change in frequency as
acetone vapors were applied, but PMN-PT showed a more significant change by several orders of magnitude.
Improving the energy conversion efficiency is one critical factor for practical usage of vibrational energy harvesting
devices. In this paper, we design and prototype a vibration-based energy harvester with a high output
energy density. The proposed harvester is based on a composite cantilever beam-mass design. The cantilever
beam is made of a high piezoelectric constant, lead magnesium niobate-lead titanate (PMN-PT) material. A
polydimethylsiloxane (PDMS) coating is applied to the cantilevers to decrease stress concentration of the thin
PMN-PT and therefore increase the strength of the cantilever. A PDMS proof mass is also added to decrease
the natural frequency of the cantilever system and to increase displacement and the voltage output. It is found
that a 7.4 mm PMN-PT cantilever with a PDMS coating and proof mass produces a sustained 0.7 mW of RMS
power (16.8 V, 58 μA) at an acceleration of 55 m/s2.
In this paper, a cantilever-based manipulator using (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single-crystal relaxor
ferroelectric material is presented. We report the design of a novel piezoelectric multi-degree-of-freedom motion
cantilever. The structure has interdigitated electrode (IDE) on the top and bottom surfaces of the cantilever and possesses
both longitudinal and flexural actuation capabilities. PMN-PT materials are ideal for actuator applications since they
exhibit a very high piezoelectric strain. We separately pattern interdigitated electrode (IDE) on the top and bottom
surfaces of a single crystal cantilever beam. Furthermore, we propose a novel L-shaped cantilever manipulator that can
provide up to four-degrees of freedom motion. The small and planar structure has potential applications in optical beam
steering systems and nano-manipulators inside a scanning electron microscope.
Pneumatic tires are critical components in mobile systems that are widely used in our lives for passenger and
goods transportation. Wheel/ground interactions in these systems play an extremely important role for not only
system design and efficiency but also safe operation. However, fully understanding wheel/ground interactions
is challenging because of high complexity of such interactions and the lack of in situ sensors. In this paper, we
present the development of a tire tread deformation sensor and energy harvester for real-time tire monitoring and
control. Polyvinylidene fluoride (PVDF) based micro-sensor is designed and fabricated to embed inside the tire
tread and to measure the tread deformation. We also present a cantilever array based energy harvester that takes
advantages of the mechanical bandpass filter concept. The harvester design is able to have a natural frequency
band that can be used to harvest energy from varying-frequency vibrational sources. The energy harvester
is also built using with new single crystal relaxor ferroelectric material (1 - &Vkgr;)Pb(Mg1/3Nb2/3)O3-&Vkgr;PbTiO3 (PMN-PT) and interdigited (IDT) electrodes that can perform the energy conversion more efficiently. Some
preliminary experiment results show that the performance of the sensor and the energy harvester is promising.
This paper presents the fabrication process of a novel aperture which allows near field optical data storage. We use
PMN-PT ((1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3) single crystal material - a new generation oxide material known as relaxor
ferroelectrics that exhibits extraordinary piezoelectric properties - to fabricate microlenes using photolithography and dry
etching techniques. In this paper, we describe the fabrication processes of a PMN-PT single crystal material microlens
prototype with a miniature aperture for near field optical data storage. PMN-PT has the merits of transparency for optical
usage and also has a high dielectric coefficient that is suitable for actuator and sensor applications. It provides an
advantage of manufacturing both aperture and actuator/sensor with the same material. The thermal reflow technique is
used to fabricate photoresist microlenses on a freestanding single crystal PMN-PT film as a mask. The PMN-PT lenses
are fabricated by a chemically assisted ion beam etching (CAIBE) technique. Finally the focused ion beam (FIB)
machining process is used to place a miniature aperture at the apex of the microlens. We were able to successfully
fabricate the 10μm PMN-PT microlenses with less than 100nm apertures. From the experimental measurement, we were
able to obtain the optical throughput of 1.83x10-7 from a 50nm aperture.
The MEMS (micro-electro-mechanical systems) microphone enables the manufacturing of small mechanical
components on the surface of a silicon wafer. The MEMS microphones are less susceptible to vibration because of the
smaller diaphragm mass and an excellent candidate for chip-scale packaging. The PMN-PT materials itself exhibit
extremely high piezoelectric coefficients and other desirable properties for an acoustic sensor. In this paper, we present a
piezoelectric MEMS microphone based on PMN-PT single crystal diaphragm. The fabrication process including dry
etching conditions and scale-factored prototype is presented. In particular, this paper introduces the design of a PMN-PT
single crystal diaphragm with interdigitated electrode.
Piezoelectric actuators are used as critical units or elements of various electromechanical systems. In this paper, we propose a novel piezoelectric actuator cantilever with double interdigitated electrode patterns. We investigate the possibility of both flexural and longitudinal actuation capabilities of the double interdigitated electrode patterns applied on a piezoelectric cantilever structure. This monomorph structure has the interdigitated electrode patterns top and bottom. The structure also uses single-crystal relaxor ferroelectric material. We separately pattern interdigitated electrodes on the top and bottom surfaces of a PMN-PT single crystal cantilever beam. The interdigitated electrode design on a surface of the cantilever beam results in an electric field gradient. This results in a flapping actuation. Previously, we showed that the vertical field component induced by the interdigitated electrode is dominant over the horizontal component under input bias voltage, and generates subsequent contraction of the surface along the axial direction after poling. In this paper, we show that a contraction on the top surface and an elongation on the bottom leads to upward bending motion because of the differential contraction along the thickness induced by the interdigitated electrode pattern. Similarly, an equivalent elongation on the top and bottom surfaces is shown to lead to longitudinal motion in the double interdigitated electrode sample.
We report on an experimental comparison between PMN-PT single crystal resonators with commercially available QCM resonators showing significant superiority for new sensors over conventional quartz. Thickness acoustic mode resonators made out of PMN-PT film were fabricated for these tests. The thickness mode resonators make use of a mechanically polished PMN-PT single crystal film of thickness 30μm. The sensor response to methanol vapor condensation shows a frequency shift for the PMN-PT resonator 1000 times larger under the same environmental conditions than the commercial quartz microbalance sensor. A surface acoustic mode resonator using mechanically polished PMN-PT single crystal film of thickness 100μm was also fabricated and tested. The dimensions of the PZN-PT film sample were 5×2×0.12mm3. Thin gold interdigitated electrodes were applied on one side of the sample. A 50nm-thick gold film was evaporated on the surface and patterned using standard photolithography. This resonator sample also exhibits a resonance frequency similar to that of a commercial quartz microbalance sensor. A large frequency drop or sensitivity is again found for the PMN-PT sensors than the quartz sensors in this case. The frequency shift in the PMN-PT surface mode resonator is ~300 times larger to methanol vapor loading than in the quartz resonator.
Advances in low power design open the possibility to harvest energy from the environment to power electronic circuits. Electrical energy can be harvested from various transducers including piezoelectric materials. Piezoelectric materials can be used as mechanisms to transfer mechanical energy usually ambient vibration into electrical energy that can be stored and used to power other devices. It has been found that a piezoelectric device attached to a beam with cantilever boundary conditions provides an effective configuration for capturing transverse vibrations and converting them into useful electrical power. Piezoelectric thin films attached to a silicon beam also have attracted attention for energy harvesting applications. In this paper, we present the results of a preliminary study of the effect of vibration amplitude on the performance of a PMN-PT single crystal beam with interdigitated electrodes pattern. The structure is used to demonstrate that feasibility of a novel piezoelectric monomorph cantilever beam for producing high AC voltage. The energy harvesting capability of a PMN-PT cantilever beam is tested on a 10mm-long and 1.2mm-wide rectangular prototype made out of 0.1mm-thick PMN-PT film with interdigitated electrodes. The experiments are performed to test the level of AC voltage and current generated from the PMN-PT cantilever beam device when subjected to transverse vibration of varying amplitude at the first mode of the resonant frequency. The frequency response of the monomorph prototype shows that the first mode resonance frequency of the excitation model is approximately 190Hz. We found that increasing the poling voltage also causes increased output AC voltage magnitude. These tests show that a significantly high AC voltage of 13V was achieved with 50μm shaker displacement. The measured RMS current was ~20μA.
A novel design of an atomic force microscope (AFM) with a (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystal scanner and a self-sensing cantilever is presented in this paper. The piezoelectric scanner and the self-sensing cantilever are integrated into a small-sized all-in-one structure with a microscope objective focused on the tip. The Z-scanner consists of two parallel PMN-PT unimorphs. This design can minimize the rotation and the sideways deflection at the sensing tip. The XY-scanner consists of two perpendicular small rods of PMN-PT. In this design, each PMN-PT rod serves as an actuator as well as a flexure because of the elastic property of the single crystal material. Under this configuration, the XY scanner can guarantee a fully decoupled planar scanning motion without positioning sensors and a sophisticated closed-loop control mechanism which is required for a XY scanner with conventional piezoelectric tubes. Furthermore, by adopting a self-sensing MEMS cantilever, the AFM design is simplified by discarding various optical sensing components. The attached objective offers fast visible inspection and rough positioning of the tip for measurement setups. We used a digital signal processor (DSP) based control scheme to achieve fast control speeds of the AFM. We also used LABVIEW for a flexible programming environment. We conducted finite-element analyses to characterize the dynamic performance of the AFM system. The system showed a high frequency band due to the small inertia of the moving part with relatively rigid structure. In addition, various scanning tests were performed to demonstrate that the system is capable of providing near video images.
A smart cantilever structure using single-crystal relaxor ferroelectric material is presented. The smart cantilever possesses both sensing and actuation capabilities, embedded in a monomorph and resulting in a smart structure. Single crystal relaxor ferroelectric materials (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) are ideal for actuator and sensor applications since they exhibit very high piezoelectric coefficients. We separately pattern interdigitated electrodes on the top and bottom surfaces of a single crystal cantilever beam. The interdigitated electrode design results in an electric field- gradient that after poling not only induces flapping actuation but also, simultaneously, allows us to detect internally or externally induced stresses. As a monolithic actuator integrated with a sensor, it has potential applications in various Micro-Electro-Mechanical Systems (MEMS), Scanning Probe Microscopy (SPM) and Near-field Scanning Optical Microscopy (NSOM). We fabricate monomorph prototypes and characterize their performance in terms of actuation displacement and sensing capabilities, respectively. Finally, an active vibration control experiment was successfully conducted by using the smart cantilever structure.
In this paper, novel piezoelectric microbalance biosensors using single crystal lead zinc niobate-lead titanate (PZN-PT) and lead magnesium niobate-lead titanate (PMN-PT) are presented. The PZN-PT/ PMN-PT materials exhibit extremely high piezoelectric coefficients and other desirable properties for biosensors, supposed to be a superior substitution for the conventional quartz crystal with the improved performance. . These biosensors provide rapid and minute quantitative target detection by monitoring the change in resonance frequency of the crystal probe. With the geometrical variations, various prototypes are compared with conventional quartz crystal microbalances (QCM). The superiority of the materials over conventional quartz crystal is demonstrated experimentally in terms of sensitivity. In addition, we examine the feasibility of ultra miniaturization of the PZN-PT based biosensor by fabricating freestanding single crystal films of the PZN-PT and patterning micro-scale biosensors with ion milling and argon-ion laser-induced etching technique. A fabricated prototype sensor utilizing the material in a thin film form has a size of 300x100x7um3.
In this paper, we report an innovative depth-sensing nanoindenter using a lead zirconium titanate (PZT) stack actuator. The conventional nanoindenter requires two sensors and closed-loop controls for precise loading or positioning due to inherent high hysteresis and creep characteristics of the PZT actuators. On the other hand, we have shown that an open-loop positioning control scheme using a single displacement sensor can be used for nanoindentation. The developed control scheme compensates for the hysteresis and creep errors of PZT actuators. By adopting the single-sensor open-loop control, the overall system structure can be simplified and a robust control environment can be achieved. In addition, a high positioning repeatability was achieved by using a flexure type mainframe with a high preload applied to the PZT actuator. To verify the system performance, we conducted the standard indentation tests on a fused quartz sample, and the results were compared with those from a commercial nanoindenter. Besides the basic nanoindentation functions, the developed system also has the capability for surface imaging through a scanning function. The pre-indentation scanning capability proved to be a very useful method for positioning the tip in the desired indentation location. Similarly, post-indentation scanning allows for visualization of the indentation marks after the tests.
An approach to improve the accuracy of phase-shift interferometry is presented. In this paper, an algorithm for estimating phase shift step errors is demonstrated. The algorithm is based on the fact that the sinusoidal intensity data from the same pixels of two interferograms with different phase shifts form an elliptic Lissajous curve. The elliptic Lissajous curve can be fitted by the least squares method from which the phase shift steps can be accurately estimated. The estimated phase shift step errors are then compensated to measure 3D topography of specimen. In addition, the approach provides a simple technique of measuring 3D topography without sophisticated actuation mechanism. Simulations and experiments also demonstrate that the intensity noise in interferograms provides very small effect on the accuracy of the algorithm.
The focus of this paper is to design a small incremental linear motor that could have the potential performance for light load applications. Due to its superior piezoelectric coefficients, PZN-PT (Pb(Zn1/3Nb2/3)O3-PbTiO) is considered as a fungible material to conventional PZT. For the design of a lightweight linear motor, PZN-PT piezoelectric actuator was utilized to drive the motor due to its fast resopnse time and high piezoelectric coefficient. Furthermore, this paper presents the design and expected performances of a PZN-PT inchworm linear motor. We propose a new method of inchworm motion based on a novel electrode design using a single rectangular rod of PZN-PT single crystal piezoelectric material. The size of the monolithic PZN-PT linear motor can be very small (a length less than 5mm). The motor has a high-resolution positioning capability.
In this paper, a small size monolithic XY scanner was designed and fabricated. The scanner has a flat triangular shape and consists of two 0.5mm-thick and 5mm-long lead-zinc-niobate-lead-titanate ((1x)Pb(ZnNb)O3 - xPbTiO3) or PZN-PT rods. The use of this material is critical to the reduction of the scanner size. The mechanical resonance characteristics for the PZN-PT rods and the assembled scanner were tested. The fabricated scanner provides a high resonance frequency and assured parallelism between the scanner and the sample surface. It enables a fast open loop control capability that naturally lends itself to use in scanning probe microscopy. The scanner and a self-sensing cantilever were integrated into a small-size atomic force microscope (AFM) design. A commercially available self-sensing cantilever and an additional actuator were used for contact scanning of a HOPG (Highly Ordered Pyrolytic Graphite) sample surface. The scanning performance of the scanner was verified by obtaining atomically resolved image of the HOPG surface.
This paper presents an investigation of a stand-alone PZN-PT film-based movable micro-mirror and characterizes its precision level. Micro-mirrors have received considerable attention for applications in various micro-opto-electro-mechanical systems (MOEMS). For example, there is considerable interest in creating micro-mirror arrays for image display and telecommunication applications. Such optical applications require high precision position control of micro-mirrors. We present the development of stand-alone self-moving micro-mirrors on the basis of a single-film actuation mechanism. The mirror design provides for tilt motion using a single-crystal Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) film unimorph actuator. A prototype micro-mirror plate is designed to a size of 600 × 400 × 10 μm3 including actuation device. In this paper, it is shown that a prototype micro-mirror fabricated in our laboratories can be operated at frequency of 50 kHz.
This paper presents a new non-contact method for measuring 3-D features of biological materials. The method can provide 3-D images of samples under liquid such as water with a microscopic resolution. One of the advantages of measuring under liquid includes protecting air sensitive surfaces of biological materials. The method is based on optical microscopy with machine vision and precision actuation. The geometric information of 3-D samples can be obtained by analyzing the focus errors of the image pixels. Experimental results have been presented and discussed to demonstrate the technique.
A phase shift interferometer with an improved phase unwrapping is presented. The nanometer resolution XY stage is integrated into the standard temporal phase shifting interferometer. The nanometer resolution XY stage is used to position specimen in subpixel of CCD detector, therefore CCD detector's sampling frequency is made high. This paper presents spatial sampling of CCD and two scanning algorithms, whose simulation and experiment results are also presented. The results show that the scanning algorithms make CCD detector's sampling frequency high, and phase unwrapping is improved also.
The surface finish of a turned part is primarily generated from process parameters such as feed, tool geometry, and cutting speed. A micropositioner system utilizing a magnetostrictive material, Terfenol-D, as a linear motor is presented as a means to actively control the process. The system has an actuator clamped in a flexor that is rigid in the feed and main cutting force directions, yet is flexible in the radial direction. Using control algorithms implemented on a digital computer, the system can provide a means to compensate for deleterious vibrations. The system has also been used to manipulate the tool position in the radial direction so that non-circular turning can be accomplished.