Experimental Study of Cochlear Dynamics With an Intracochlear Acoustic Micro-Actuator

2019 ◽  
Author(s):  
Sergiy Taylakov ◽  
I. Y. Shen
Keyword(s):  
Lead Zirconate Titanate ◽  
Laser Doppler Vibrometer ◽  
Electrode Array ◽  
Petri Dish ◽  
Lead Zirconate ◽  
Squeeze Film ◽  
Test Rig ◽  
Micro Actuator ◽  
Squeeze Film Effect ◽  
Pzt Thin Film

Abstract An intracochlear lead-zirconate-titanate (PZT) micro-actuator can complement a cochlear implant electrode array to rehabilitate hearing loss patients with enhanced speech recognition. The presence of the intracochlear micro-actuator has significantly altered the cochlear dynamics, because the actuation now results from the micro-actuator instead of the stapes. To understand sound induction mechanisms by the micro-actuator, we design a test rig that mimics the box model of a human cochlea. The test rig consists of two connected fluid canals, one aluminum membrane sandwiched between the canals, and a PZT thin-film micro-actuator. Frequency response functions of the micro-actuator and the aluminum membrane are measured using a laser Doppler vibrometer and a spectrum analyzer. Measurements are taken when the micro-actuator is in air, in a petri dish surrounded by oil, and in the fluid canals inside the test rig. When the micro-actuator is moved from the petri dish (i.e., an open environment) to the inside of the fluid canals (i.e., a closed environment), the natural frequency and static gain of the micro-actuator both drop significantly indicating substantial increase in stiffness and inertia. A possible reason for the change, which remains to be confirmed, is the squeeze film effect from the fluid between the micro-actuator and the aluminum membrane.

Effects of Added Mass on Lead-Zirconate-Titanate (PZT) Thin-Film Microactuators in Aqueous Environments

2013 ◽  
Author(s):  
Chuan Luo ◽  
Chen-Wei Yang ◽  
G. Z. Cao ◽  
I. Y. Shen
Keyword(s):  
Thin Film ◽  
Lead Zirconate Titanate ◽  
Silicon Substrate ◽  
Laser Doppler Vibrometer ◽  
Lead Zirconate ◽  
Added Mass ◽  
Surrounding Water ◽  
Zirconate Titanate ◽  
Pzt Thin Film ◽  
Aqueous Environments

In this paper, we conduct experimental and theoretical studies of a lead-zirconate-titanate (PZT) thin-film microactuator probe submerged in water. The microactuator consists of a base silicon diaphragm, a layer of bottom electrode, a layer of lead-zirconate-titanate (PZT) thin film, and a layer of top electrode. The diaphragm is anchored on a silicon substrate by etching the silicon substrate from the back to form a cavity under the diaphragm. The diaphragm along with part of its anchor is then diced off from the silicon substrate to form a PZT probe and subsequently packaged with parylene. The probe tip has dimensions of 1 mm × 1 mm × 0.4 mm, while the diaphragm has dimensions of 800 μm × 800 μm × 2 μm. In the experimental study, frequency response functions of actuator displacement are measured via a laser Doppler vibrometer and a spectrum analyzer. The measurements show that the first natural frequency of the microactuator reduces from 80 kHz in air to 20 kHz when the microactuator is submerged in water. A literature search indicates that the surrounding water induces significant added mass to the microactuator. Estimation of the added mass based on theories in fluid mechanics successfully reconcile the predicted frequency to the vicinity of 20 kHz confirming the effects of added mass.

Effects of Air on Enclosure Design of Lead-Zirconate-Titanate (PZT) Thin-Film Diaphragm Microactuators

2012 ◽  
Author(s):  
Chuan Luo ◽  
Kai-Yi Hsiao ◽  
Perry Cheung ◽  
Howard Lin ◽  
A. Q. Shen ◽  
...  
Keyword(s):  
Thin Film ◽  
Lead Zirconate Titanate ◽  
Silicon Substrate ◽  
Lead Zirconate ◽  
Ideal Gas ◽  
Experimental Results ◽  
Micro Actuator ◽  
Zirconate Titanate ◽  
Pzt Thin Film ◽  
Elastic Spring

In this paper, we evaluate performance of two types of piezoelectric diaphragm micro-actuators: open-end design and closed-end design. In the open-end design, the micro-actuator consists of a base silicon diaphragm, a layer of bottom electrode, a layer of lead-zirconate-titanate (PZT) thin film, and a layer of top electrode. The diaphragm is anchored on a silicon substrate by etching the silicon substrate from the back to form a cavity under the diaphragm. In the closed-end design, the bottom of the cavity is sealed with a piece of glass, silicon or PDMS. Experimental results show that the measured displacements from the closed-end design are always 5%–30% lower than those from the open-end design. To explain the experimental results, we hypothesize that the air inside the cavity of the closed-end design behaves like an elastic spring increasing the stiffness of the closed-end design. To confirm the hypothesis, we estimate the stiffness of the air by modeling the air as an ideal gas with a constant temperature. We also model the diaphragm as a lumped spring. Combination of the stiffness from the diaphragm and the air predicts the overall stiffness and displacement of the closed-end design. The predictions agree well with the experimental measurements, indicating that the air in the cavity significantly stiffens the closed-end design.

scholarly journals Effects of Added Mass on Lead-Zirconate-Titanate Thin-Film Microactuators in Aqueous Environments

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Chuan Luo ◽  
W. C. Tai ◽  
Cheng-Wei Yang ◽  
G. Z. Cao ◽  
I. Y. Shen
Keyword(s):  
Thin Film ◽  
Finite Element ◽  
Natural Frequency ◽  
Lead Zirconate Titanate ◽  
Laser Doppler Vibrometer ◽  
Lead Zirconate ◽  
Added Mass ◽  
Surrounding Water ◽  
Zirconate Titanate ◽  
Pzt Thin Film

In this paper, we conduct experimental, theoretical, and numerical studies of a lead-zirconate-titanate (PZT) thin-film microactuator probe submerged in water. The major component of the actuator is a PZT diaphragm anchored on four silicon sidewalls. There is also silicon residue at the juncture of the diaphragm and the sidewalls due to imperfect etching processes. In the experimental study, frequency response functions of actuator displacement are measured via a laser Doppler vibrometer and a spectrum analyzer. The measurements show that the first natural frequency of the microactuator reduces from 80 kHz in air to 20 kHz when the microactuator is submerged in water. A viable explanation is that the surrounding water induces significant added mass to the microactuator. Estimation of the added mass based on theories in fluid mechanics successfully reconciles the predicted frequency to the vicinity of 20 kHz confirming the effects of added mass. Finite element models are also created to study how the silicon sidewalls and residue affect the added mass. Simulations show that presence of the sidewalls or residue would modify the fluid flow thus altering the added mass and natural frequency. In general, the finite element predictions agree well with the experimental measurements within 10% difference.

Correlations Among Degradations in Lead Zirconate Titanate thin Film Capacitors

1993 ◽  
Vol 310 ◽  
Author(s):  
In K. Yoo ◽  
Seshu B. Desu ◽  
Jimmy Xing
Keyword(s):  
Thin Film ◽  
Leakage Current ◽  
Lead Zirconate Titanate ◽  
Oxygen Vacancies ◽  
Lead Zirconate ◽  
Electrical Degradation ◽  
Zirconate Titanate ◽  
Thin Film Capacitors ◽  
Pzt Thin Film ◽  
Degradation Properties

AbstractMany attempts have been made to reduce degradation properties of Lead Zirconate Titanate (PZT) thin film capacitors. Although each degradation property has been studied extensively for the sake of material improvement, it is desired that they be understood in a unified manner in order to reduce degradation properties simultaneously. This can be achieved if a common source(s) of degradations is identified and controlled. In the past it was noticed that oxygen vacancies play a key role in fatigue, leakage current, and electrical degradation/breakdown of PZT films. It is now known that space charges (oxygen vacancies, mainly) affect ageing, too. Therefore, a quantitative ageing mechanism is proposed based on oxygen vacancy migration under internal field generated by either remanent polarization or spontaneous polarization. Fatigue, leakage current, electrical degradation, and polarization reversal mechanisms are correlated with the ageing mechanism in order to establish guidelines for simultaneous degradation control of PZT thin film capacitors. In addition, the current pitfalls in the ferroelectric test circuit is discussed, which may cause false retention, imprint, and ageing.

scholarly journals Effects of Acetylacetone Additions on PZT Thin Film Processing

1994 ◽  
Vol 361 ◽  
Author(s):  
Robert W. Schwartz ◽  
R.A. Assink ◽  
D. Dimos ◽  
M.B. Sinclair ◽  
T.J. Boyle ◽  
...  
Keyword(s):  
Thin Film ◽  
Lead Zirconate Titanate ◽  
Sol Gel ◽  
Precursor Solution ◽  
Lead Zirconate ◽  
Pzt Thin Film ◽  
Precursor Structure ◽  
Drying Behavior ◽  
Ceramic Microstructure ◽  
Gel Processing

ABSTRACTSol-gel processing methods are frequently used for the fabrication of lead zirconate titanate (PZT) thin films for many electronic applications. Our standard approach for film fabrication utilizes lead acetate and acetic acid modified metal alkoxides of zirconium and titanium in the preparation of our precursor solutions. This report highlights some of our recent results on the effects of the addition of a second chelating ligand, acetylacetone, to this process. We discuss the changes in film drying behavior, densification and ceramic microstructure which accompany acetylacetone additions to the precursor solution and relate the observed variations in processing behavior to differences in chemical precursor structure induced by the acetylacetone ligand. Improvements in thin film microstructure, ferroelectric and optical properties are observed when acetylacetone is added to the precursor solution.

A Study on Long-Term In Vitro Reliability of Intracochlear Lead-Zirconate-Titanate Microactuators

2018 ◽  
Vol 1 (3) ◽  
Author(s):  
Yifeng Liu ◽  
Chuan Luo ◽  
G. Z. Cao ◽  
Clifford R. Hume ◽  
I. Y. Shen
Keyword(s):  
Lead Zirconate Titanate ◽  
Electrical Breakdown ◽  
Failure Mechanisms ◽  
Electrode Array ◽  
Lead Zirconate ◽  
Acoustic Stimulation ◽  
Structural Failure ◽  
Significant Drop ◽  
Zirconate Titanate

An intracochlear lead-zirconate-titanate (PZT) microactuator integrated with a cochlear implant electrode array could be a feasible strategy to implement combined electric and acoustic stimulation inside the cochlea. The purpose of this paper is to characterize in vitro a prototype PZT microactuator for intracochlear applications, including service life, failure mechanisms, and lead leaching. PZT microactuators were driven sinusoidally to failure in air and in artificial perilymph. Frequency response functions (FRFs) and electrical impedance were monitored. After the PZT microactuators failed, the amount of leached lead was measured via inductive coupled plasma mass spectrometry (ICP-MS). Two failure mechanisms are identified: electrical breakdown and structural failure. The electrical breakdown, possibly from loss of parylene encapsulation, is evidenced by a sudden and significant drop of the actuators' electrical resistance. The structural failure, possibly from electrode delamination, is evidenced by a sudden and significant drop of FRFs. The amount of lead leached from the PZT microactuator is well below published safety guidelines from federal agencies.

The Role of the Lead Zirconate Titanate (PZT)-Pt Interface in the Anomalous Phase Transformation Kinetics in Sputtered Pzt Thin Film Capacitors at Sub-2000 Å Thicknesses

1991 ◽  
Vol 243 ◽  
Author(s):  
Vinay Chikarmane ◽  
Jiyoung Kim ◽  
C. Sudhama ◽  
Jack Lee ◽  
Al Tasch ◽  
...  
Keyword(s):  
Thin Film ◽  
Phase Transformation ◽  
Lead Zirconate Titanate ◽  
Lead Zirconate ◽  
Initial Increase ◽  
Transformation Kinetics ◽  
Pzt Film ◽  
Zirconate Titanate ◽  
Phase Transformation Kinetics ◽  
Pzt Thin Film

AbstractThe Pt-Lead Zirconate Titanate (PZT) thin film interface plays a key role in determining the electrical properties and phase transformation kinetics of Pt-PZT-Pt thin film capacitor structures. The results of the electrical and material properties of PZT (65/35) films that vary in thickness between 500 Å to 4000 Å deposited by DC-magnetron sputtering under identical deposition conditions, and subjected to the same post-deposition thermal processing conditions shows that the Pt-PZT interface dominates thin film properties at low thicknesses (≦ 2000 Å). The charge storage density (Qc') and maximum polarization (Pmax) shows an anomalous variation with thickness, showing an initial increase followed by a drastic decrease as the film thickness is scaled down to 500Å. Significant interdiffusion at the PZT film-Pt electrode retards the pyrochlore-to-perovskite phase transformation nucleation and growth rate in PZT films of thickness 2000Å and lower. Gate polarity dependence of the time-tobreakdown and the degradation field is observed for all PZT film thicknesses (including 4000Å). This indicates that the ferroelectric film-electrode interface has an important role to play in determining the electrical reliability properties even in the 4000Å thick PZT film, although Qc' and Pmax are not adversely affected at these thicknesses.

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