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Amplified Piezoelectric Actuators, 220 µm to 1500 µm Travel
Amplified Piezoelectric Actuator with 220 µm Displacement
Amplified Piezoelectric Actuator with 560 µm Displacement
Direction of Translation
Direction of Translation
Thorlabs' Amplified Piezoelectric Actuators consist of a discrete piezoelectric stack mounted inside a flexure housing. The flexure mount acts as a lever arm that amplifies the free stroke displacement of the stand-alone discrete stack. While the displacement achieved by this assembly is significantly larger than that of the piezo stack, the fast response times and low drive voltage ranges of the discrete stack are maintained. Because this displacement is created by a piezo stack within a flexure mount, these actuators do not suffer from backlash.
Two types of amplified piezo actuators are available. The PK2F Series Amplified Piezos utilize a flexure structure that pushes the load away from the stack when the voltage is increased. These actuators feature a U-shaped, protective metal cover, as well as a ball contact for mounting a load on top. In contrast, the APF Series is designed to pull the load toward the stack when the voltage is increased. The APF Series piezos are installed in an open frame with several tapped holes for mounting components, making them ideal for OEM applications. See the table to the right for further comparison between the two types, and see the Specs tab for complete specifications.
Please see the Operation tab for guidance on integrating these piezoelectric devices into applications, special operational considerations, and data that will allow their lifetimes to be estimated when their operational conditions are known.
Note: When building the setup, keep the wire leads of each piezo bundled together to avoid static discharge, which can damage the piezo elements.
Thorlabs also offers Co-fired Piezoelectric Stacks with maximum displacements from 4.6 µm to 17.4 µm, including one with a built-in strain gauge that can be used to provide feedback. Unlike discrete piezo stacks that are composed of PZT chips that have been bonded together, co-fired piezoelectric stacks are composed of PZT chips that have been sintered together to form a single monolithic structure. Our piezoelectric tutorial contains more information about the design and function of piezoelectric stacks.
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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.
All specifications are quoted at 25 °C unless otherwise stated.
Displacement vs. Voltage Curves
The displacement vs. voltage hysteresis curves for the amplified piezos are available here. The hysteresis is a result of some variability in the orientations of the ferroelectric domain polarizations within the PZT crystal. During fabrication, the polarizations of the large majority of crystal domains are aligned along the same direction by applying a strong electric field, which is considerably stronger than the one applied during device operation, across the PZT crystal. It is the contribution of other, extrinsic, ferroelectric domains that are the source of the hysteresis, and the magnitudes of their contributions depend on factors that include the mechanical pre-loading of the actuator, the temperature of the device, the control frequency, the dimensions of the device, and the history of the voltage signal driving the device.
To view the plots, click More [+] in the appropriate row below.
Resonant Frequency vs. Load Curves
A parameter of significance to many applications is the rate at which the piezoelectric actuator changes its length. This dimensional rate of change depends on a number of factors, including the bandwidth of the piezoelectric actuator (its resonant frequency), the absolute maximum bandwidth of the driver (its slew rate), the maximum current the piezoelectric device can produce, the capacitance of the piezoelectric stack, and the amplitude of the driving signal. The length of the voltage-induced extension is a function of the amplitude of the applied voltage driving the actuator and the length of the piezoelectric stack. The higher the capacitance, the slower the dimensional change of the actuator.
Quick changes in the applied voltage result in fast dimensional changes to the piezoelectric 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 value and that corresponding to the final applied voltage is approximately 1/3 the period of resonant frequency. If there is no load applied to the piezoelectric stack, its resonance 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 using the following equation:
The unloaded resonant frequencies of the amplified piezos can be seen by clicking More [+] in the rows below.
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The image above shows the PK2F series flexure mount without the U-shaped protective cover.
APF Series: Typically, the electrode attached to the black wire (APF503) or white wire (APF705 and APF710) should be grounded, while a bi-polar power supply is used to apply a voltage from -30 V to +150 V to the red wire. Alternatively, the full range of motion can be achieved by holding the black or white wire at +30 V and varying the voltage on the red lead between 0 and +180 V if a bi-polar power supply is not available.
Interfacing the Amplified Piezoelectric Actuator with a Load
APF Series: Loads should be mounted to the taps on the top or sides of the actuator housing. Be careful to align the load properly with the actuator's translation axis to avoid introducing angular resonance modes.
Soldering Wire Leads to the Electrodes
Operating Under High-Frequency Dynamic Conditions
Estimating Device Lifetime for DC Drive Voltage Conditions
The lifetime of a piezoelectric device is a function of the operating temperature, applied voltage, and relative humidity conditions. Lifetimes are reduced as a consequence of humidity-driven electrolytic reactions, which occur at the electrodes of the piezoelectric devices when a DC voltage is applied. These reactions both generate hydrogen and result in metal dendrites growing from the cathode towards the anode. The hydrogen liberated by the electrolytic reaction chemically reacts with and degrades the piezoelectric material. Dendrites that grow to electrically connect the cathode and anode result in increasing levels of leakage current. Failed piezoelectric devices are defined as those that exhibit leakage current levels above an established threshold.
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 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.
The data shown in these graphs was taken using the PK2FSF1 piezo actuator. The other actuators on this page exhibit similar performance.
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For an Excel file containing these fH vs. relative humidity data, please click here.
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.
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Bottom of the U-Shaped Protective Cover
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Piezo Flexure Mount Without U-Shaped Protective Cover
These Amplified Piezoelectric Actuators consist of a discrete piezoelectric stack housed within a flexure mount. The flexure mount acts as a lever arm that amplifies the free stroke displacement of the stand-alone discrete stack, providing 220 µm or 420 µm total travel.
These piezo actuators come with pre-attached wires; the electrode attached to the red wire should be positively biased, and the electrode attached to the black wire should be grounded.
The U-shaped metal cover protects the piezo stack and wire connections. Additionally, it has two M2.5 taps to provide easy and secure mounting options (see drawing above). This cover may be removed by unscrewing the M2 cap screw holding it in place; the screw is secured with thread glue, but it can be removed with a 2 mm hex wrench.
A tungsten-carbide spherical contact on the top of the actuator housing allows for precise mounting of the load along the translation axis and prevents undesired stress along the other axes. When working with these lead zirconate titanate (PZT) devices or integrating them into a setup, take care not to squeeze them at their edges and ensure the piezoelectric stack is stressed only in the translation direction.
Each stack is covered on four sides by an insulating ceramic layer that acts as a barrier to moisture. The ceramic layer offers better protection against moisture than an epoxy coating. For convenience, the stacks have pre-attached 75 mm long wires and are wrapped in Kapton® tape.
These actuators are compatible with the MDT69xB and KPZ101 open-loop controllers, and the MPZ601 or BPC30x closed-loop controllers. However please note that these actuators do not contain a strain gauge and will therefore not provide positional feedback information when closed-loop controllers are used. If closed-loop feedback is required, please consider the Piezoelectric Actuators with Attached Strain Gauges.
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Mounting Holes on the APF503
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Mounting Holes on the APF705 and APF710
These Amplified Piezoelectric Actuators consist of a discrete piezoelectric stack housed within a flexure mount. The flexure mount acts as a lever arm that amplifies the free stroke displacement of the stand-alone discrete stack, providing 390 µm, 560 µm, or 1500 µm total travel.
The piezo actuators come with pre-attached wires. Under typical usage conditions, the electrode attached to the black wire (APF503) or white wire (APF705 and APF710) should be grounded, while a bi-polar power supply is used to apply a voltage from -30 V to +150 V to the red wire. Alternatively, the full range of motion can be achieved by holding the black or white wire at +30 V and varying the voltage on the red lead between 0 and +180 V if a bipolar power supply is not available.
The flexure housing has one tapped mounting hole on the top and on the bottom, as well as four tapped mounting holes on the front and on the back. See the drawings to the right for the threading specifications of the mounting holes on each piezo actuator housing. These mounting options provide flexibility when integrating the actuators into a setup, but care must be taken to align the load properly with the actuator's translation axis to avoid introducing angular resonance modes. See the manual for details on linear and angular resonance modes.
These actuators can be driven with the MDT69xB and KPZ101 open-loop controllers, and the MPZ601 or BPC30x closed-loop controllers. These controllers are capable of providing drive voltages from 0 to 150 V and thus will not achieve the full range of the piezo actuators. Please also note that these actuators do not contain a strain gauge and will therefore not provide positional feedback information when closed-loop controllers are used. If closed-loop feedback is required, consider the Piezoelectric Actuators with Attached Strain Gauges.