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Piezoelectric Tube Actuators
Arrows Indicate Directions of Contraction
Top View of the PT49LM
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The inner surface of the piezo tube is the positive electrode and should receive a positive voltage.
These piezoelectric chips consist of a thin ceramic sheet in a cylindrical shape. They have an outer diameter of 8.0 mm and an inner diameter of 7.0 mm. The piezo tubes provide a maximum displacement of 2.8 µm along the axis of the cylinder and 1.8 µm in the radial direction. The actuators contract in both the radial and axial directions when a positive voltage is applied to the electrodes. The inner surface is the positive electrode that should receive positive bias. In the case of the wired actuators, the wire soldered to the positive electrode is red.
When using these piezos, the load should be mounted on either the curved surface (for radial displacement) or the top and bottom rims (for axial displacement). Do not use with loads mounted to both areas. The radial load should be less than 20 N; exceeding 20 N may cause mechanical failure. In addition, a radial load should only be attached to the central area of the outer surface, at least 1 mm away from the edges. Attaching a radial load to the edges may lead to mechanical failure. For axial loads, try to obtain as large an area of contact as possible on the top and bottom edges of the tube without interfering with the attached wires. See the Operation tab for more information on using these piezoelectric actuators.
Because these piezo elements contract with an applied voltage, applying a pushing load to the piezo enhances the stroke; however, the load negatively influences the recovery. For this reason, we do not specify a load for maximum displacement as with other piezo designs.
The shape of these piezo elements makes them ideal for fiber-stretching and micro-dosing applications.
Piezo Tube Construction and Operation
Piezo chips with custom dimensions, voltage ranges, and coatings are available. Additionally, customers can order these piezo chips in high-volume quantities. Please contact Tech Support for more information.
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Dicing the PZT Block into Individual Elements
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Chips After Binder Burnout and Sintering
Thorlabs' In-House Piezoelectric Manufacturing
Our piezoelectric chips are fabricated in our production facility in China, giving us full control over each step of the manufacturing process. This allows us to economically produce high-quality products, including custom and OEM devices. A glimpse into the fabrication of our piezoelectric chips follows. For more information about our manufacturing process and capabilities, please see our Piezoelectric Capabilities page.
Soldering Wire Leads to the Electrodes
Interfacing a Piezoelectric Element with a Load
Operating Under High-Frequency Dynamic Conditions
Estimating the Resonant Frequency for a Given Applied Load
Quick changes in the applied voltage result in fast dimensional changes to the piezoelectric stack. The magnitude of the applied voltage determines the nominal extension of the stack. Assuming the driving voltage signal resembles a step function, the minimum time, Tmin, required for the length of the actuator to transition between its initial and final values is approximately 1/3 the period of resonant frequency. If there is no load applied to the piezoelectric stack, its resonant frequency is ƒo and its minimum response time is:
After reaching this nominal extension, there will follow a damped oscillation in the length of the actuator around this position. Controls can be implemented to mitigate this oscillation, but doing so may slow the response of the actuator.
Applying a load to the actuator will reduce the resonant frequency of the piezoelectric stack. Given the unloaded resonant frequency of the actuator, the mass of the stack, m, and the mass of the load, M, the loaded resonant frequency (ƒo') may be estimated:
Estimating Device Lifetime for DC Drive Voltage Conditions
A ceramic moisture-barrier layer that insulates Thorlabs' piezoelectric devices on four sides is effective in minimizing the effects of humidity on device lifetime. As there is interest in estimating the lifetime of piezoelectric devices, Thorlabs conducted environmental testing on our ceramic-insulated, low-voltage, piezoelectric actuators. The resulting data were used to create a simple model that estimates the mean time to failure (MTTF), in hours, when the operating conditions of humidity, temperature, and applied voltage are known. The estimated MTTF is calculated by multiplying together three factors that correspond, respectively, to the operational temperature, relative humidity, and fractional voltage of the device. The fractional voltage is calculated by dividing the operational voltage by the maximum specified drive voltage for the device. The factors for each parameter can be read from the following plots, or they may be calculated by downloading the plotted data values and interpolating as appropriate.
In the following trio of plots, the solid-line segment of each curve represents the range of conditions over which Thorlabs performed testing. These are the conditions observed to be of most relevance to our customers. The dotted-line extensions to the solid-line segments represent extrapolated data and represent a wider range of conditions that may be encountered while operating the devices.
Calculation of MTTF to Estimate Lifetimes: MTTF = fV * fT * fH
Given the relative humidity conditions, device temperature, and DC operational voltage, the device lifetime can be estimated. It is the product of voltage, temperature, and humidity factors, which can be determined using relationships plotted at right, lower-right, and below.
As an example, when a device of type PK2FSF1 is operated with a voltage of 60 V, at a temperature of 30 °C, and in an environment with 75% relative humidity:
Then MTTF = 472 * 83 * 2.8 = 99234.8 hours, which is greater than 11 years.
Note that relationships graphed on this page apply only to Thorlabs' ceramic-insulated, low-voltage, piezoelectric stack actuators.
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For an Excel file containing these fH vs. relative humidity data, please click here.
The data used to generate these temperature, voltage, and humidity factor plots resulted from the analysis of measurements obtained from testing devices under six different operational conditions. Different dedicated sets of ten devices were tested under each condition, with each condition representing a different combination of operational voltage, device temperature, and relative humidity. After devices exhibit leakage current levels above a threshold of 100 nA, they are registered as having failed. The individual contributions of temperature, humidity, and voltage to the lifetime are determined by assuming:
where A1, A2, A3, b1, b2, and c are constants determined through analysis of the measurement data, V is the DC operational voltage, T is the device temperature, and H is the relative humidity. Because the MTTF has a different mathematical relationship with each factor, the dependence of the MTTF on each factor alone may be determined. These are the data plotted above. The regions of the above curves marked by the blue shading are derived from experimental data. The dotted regions of the curves are extrapolated.
Lifetime testing of these devices continues, and additional data will be published here as they become available.