Piezoelectric microelectromechanical systems

Last updated

A piezoelectric microelectromechanical system (piezoMEMS) is a miniature or microscopic device that uses piezoelectricity to generate motion and carry out its tasks. It is a microelectromechanical system that takes advantage of an electrical potential that appears under mechanical stress. PiezoMEMS can be found in a variety of applications, such as switches, inkjet printer heads, sensors, micropumps, and energy harvesters. [1]

Contents

Development

Interest in piezoMEMS technology began around the early 1990s as scientists explored alternatives to electrostatic actuation in radio frequency (RF) microelectromechanical systems (MEMS). [2] For RF MEMS, electrostatic actuation specialized high voltage charge pump circuits due to small electrode gap spacing and large driving voltages. In contrast, piezoelectric actuation allowed for high sensitivity as well as low voltage and power consumption as low as a few millivolts. [3] [4] It also had the ability to close large vertical gaps while still allowing for low microsecond operating speeds. [5] Lead zirconate titanate (PZT), in particular, offered the most promise as a piezoelectric material because of its high piezoelectric coefficient, tunable dielectric constant, and electromechanical coupling coefficient. [4] PiezoMEMS have been applied to various different technologies from switches to sensors, and further research have led to the creation of piezoelectric thin films, which aided in the realization of highly integrated piezoMEMS devices. [6]

The first reported piezoelectrically actuated RF MEMS switch was developed by scientists at the LG Electronics Institute of Technology in Seoul, South Korea in 2005. [3] The researchers designed and actualized a RF MEMS switch with a piezoelectric cantilever actuator that had an operation voltage of 2.5 volts. [7]

In 2017, researchers from the U.S. Army Research Laboratory (ARL) evaluated the radiation effects in the piezoelectric response of PZT thin films for the first time. They determined that PZT exhibited a degree of radiation hardness that could be further extended by using conductive oxide electrodes instead of traditional platinum electrodes. Gamma radiation tests have also shown that actuated devices such as switches, resonators, and inertial devices could benefit from the radiation tolerance of PZT, suggesting the possibility that actuators and sensors can be integrated into platforms evaluating nuclear material and reduce human exposure to radiation. [8] [9]

This experiment was part of a decades-long research investment effort at ARL to improve the use of PZT thin film technology for piezoMEMS. [4] Other piezoMEMS-related work included developing a piezoelectric microphone based on PZT thin films, [10] creating new integrated surface micromachining processes for RF MEMS to incorporate thin film PZT actuators, [11] providing the first experimental demonstration of monolithically integrated piezoMEMS RF switches with contour mode filters, [12] and demonstrating the feasibility of vibrational energy harvesting using thin film PZT MEMS. [13] In their work, researchers from ARL have also increased the overall electromechanical response of PZT thin films by 15-30% by incorporating iridium oxide electrode materials. [8]

Design

There exists three primary approaches to realizing PiezoMEMS devices: [14]

  1. The additive approach: The piezoelectric thin films are deposited on silicon substrates with layers of insulating and conducting material followed by surface or silicon bulk micromachining.
  2. The subtractive approach: Single crystal or polycrystalline piezoelectrics and piezoceramics are subjected to direct bulk micromachining and then electrodes.
  3. The integrative approach: Micromachined structures are integrated in silicon or piezoelectrics by using bonding techniques on bulk piezoelectric or silicon substrates.

PiezoMEMS use two principal crystal structures, the wurtzite and perovskite structures. [6]

Challenges

PiezoMEMS still face many difficulties that impede its ability to be successfully commercialized. For instance, the success of depositing uniform films of piezoelectrics still depend heavily on the use of appropriate layers of proper nucleation and film growth. As a result, extensive device-specific development efforts are needed to create a proper sensor structure. In addition, researchers continue to search for ways to reduce and control the material and sensor drift and aging characteristics of thin film piezoelectric materials. Deposition techniques to create thin films with properties approaching those of bulk materials remain in development and in need of improvement. Furthermore, the chemistry and etching characteristics of most piezoelectric materials remain very slow. [14]

Related Research Articles

<span class="mw-page-title-main">MEMS</span> Very small devices that incorporate moving components

MEMS is the technology of microscopic devices incorporating both electronic and moving parts. MEMS are made up of components between 1 and 100 micrometres in size, and MEMS devices generally range in size from 20 micrometres to a millimetre, although components arranged in arrays can be more than 1000 mm2. They usually consist of a central unit that processes data and several components that interact with the surroundings.

<span class="mw-page-title-main">Piezoelectricity</span> Electric charge generated in certain solids due to mechanical stress

Piezoelectricity is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure and latent heat. It is derived from Ancient Greek πιέζω (piézō) 'to squeeze or press', and ἤλεκτρον (ḗlektron) 'amber'.

<span class="mw-page-title-main">Lead zirconate titanate</span> Chemical compound

Lead zirconate titanate, also called lead zirconium titanate and commonly abbreviated as PZT, is an inorganic compound with the chemical formula Pb[ZrxTi1−x]O3(0 ≤ x ≤ 1). It is a ceramic perovskite material that shows a marked piezoelectric effect, meaning that the compound changes shape when an electric field is applied. It is used in a number of practical applications such as ultrasonic transducers and piezoelectric resonators. It is a white to off-white solid.

Energy harvesting is the process by which energy is derived from external sources, then stored for use by small, wireless autonomous devices, like those used in wearable electronics, condition monitoring, and wireless sensor networks.

<span class="mw-page-title-main">Piezoelectric sensor</span> Type of sensor

A piezoelectric sensor is a device that uses the piezoelectric effect to measure changes in pressure, acceleration, temperature, strain, or force by converting them to an electrical charge. The prefix piezo- is Greek for 'press' or 'squeeze'.

A thin-film bulk acoustic resonator is a device consisting of a piezoelectric material manufactured by thin film methods between two conductive – typically metallic – electrodes and acoustically isolated from the surrounding medium. The operation is based on the piezoelectricity of the piezolayer between the electrodes.

<span class="mw-page-title-main">Deformable mirror</span>

Deformable mirrors (DM) are mirrors whose surface can be deformed, in order to achieve wavefront control and correction of optical aberrations. Deformable mirrors are used in combination with wavefront sensors and real-time control systems in adaptive optics. In 2006 they found a new use in femtosecond pulse shaping.

Micropower describes the use of very small electric generators and prime movers or devices to convert heat or motion to electricity, for use close to the generator. The generator is typically integrated with microelectronic devices and produces "several watts of power or less." These devices offer the promise of a power source for portable electronic devices which is lighter weight and has a longer operating time than batteries.

A MEMS thermal actuator is a microelectromechanical device that typically generates motion by thermal expansion amplification. A small amount of thermal expansion of one part of the device translates to a large amount of deflection of the overall device. Usually fabricated out of doped single crystal silicon or polysilicon as a complex compliant member, the increase in temperature can be achieved internally by electrical resistive heating or by a heat source capable of locally introducing heat. Microfabricated thermal actuators can be integrated into micromotors.

<span class="mw-page-title-main">Radio-frequency microelectromechanical system</span>

A radio-frequency microelectromechanical system is a microelectromechanical system with electronic components comprising moving sub-millimeter-sized parts that provide radio-frequency (RF) functionality. RF functionality can be implemented using a variety of RF technologies. Besides RF MEMS technology, III-V compound semiconductor, ferrite, ferroelectric, silicon-based semiconductor, and vacuum tube technology are available to the RF designer. Each of the RF technologies offers a distinct trade-off between cost, frequency, gain, large-scale integration, lifetime, linearity, noise figure, packaging, power handling, power consumption, reliability, ruggedness, size, supply voltage, switching time and weight.

<span class="mw-page-title-main">Micropump</span>

Micropumps are devices that can control and manipulate small fluid volumes. Although any kind of small pump is often referred to as micropump, a more accurate definition restricts this term to pumps with functional dimensions in the micrometer range. Such pumps are of special interest in microfluidic research, and have become available for industrial product integration in recent years. Their miniaturized overall size, potential cost and improved dosing accuracy compared to existing miniature pumps fuel the growing interest for this innovative kind of pump.

<span class="mw-page-title-main">MEMS magnetic field sensor</span>

A MEMSmagnetic field sensor is a small-scale microelectromechanical systems (MEMS) device for detecting and measuring magnetic fields (Magnetometer). Many of these operate by detecting effects of the Lorentz force: a change in voltage or resonant frequency may be measured electronically, or a mechanical displacement may be measured optically. Compensation for temperature effects is necessary. Its use as a miniaturized compass may be one such simple example application.

A MEMS magnetic actuator is a device that uses the microelectromechanical systems (MEMS) to convert an electric current into a mechanical output by employing the well-known Lorentz Force Equation or the theory of Magnetism.

Microelectromechanical system oscillators are devices that generate highly stable reference frequencies to measure time. The core technologies used in MEMS oscillators have been in development since the mid-1960s, but have only been sufficiently advanced for commercial applications since 2006. MEMS oscillators incorporate MEMS resonators, which are microelectromechanical structures that define stable frequencies. MEMS clock generators are MEMS timing devices with multiple outputs for systems that need more than a single reference frequency. MEMS oscillators are a valid alternative to older, more established quartz crystal oscillators, offering better resilience against vibration and mechanical shock, and reliability with respect to temperature variation.

<span class="mw-page-title-main">Microscanner</span>

A microscanner, or micro scanning mirror, is a microoptoelectromechanical system (MOEMS) in the category of micromirror actuators for dynamic light modulation. Depending upon the type of microscanner, the modulatory movement of a single mirror can be either translatory or rotational, on one or two axes. In the first case, a phase shifting effect takes place. In the second case, the incident light wave is deflected.

Piezoelectric Micromachined Ultrasonic Transducers (PMUT) are MEMS-based piezoelectric ultrasonic transducers. Unlike bulk piezoelectric transducers which use the thickness-mode motion of a plate of piezoelectric ceramic such as PZT or single-crystal PMN-PT, PMUT are based on the flexural motion of a thin membrane coupled with a thin piezoelectric film, such as PVDF. In comparison with bulk piezoelectric ultrasound transducers, PMUT can offer advantages such as increased bandwidth, flexible geometries, natural acoustic impedance match with water, reduced voltage requirements, mixing of different resonant frequencies and potential for integration with supporting electronic circuits especially for miniaturized high frequency applications.

<span class="mw-page-title-main">Richard S. Muller</span>

Richard Stephen Muller is an American professor in the Electrical Engineering and Computer Science Department of the University of California at Berkeley.

A nanoelectromechanical (NEM) relay is an electrically actuatedswitch that is built on the nanometer scale using semiconductor fabrication techniques. They are designed to operate in replacement of, or in conjunction with, traditional semiconductor logic. While the mechanical nature of NEM relays makes them switch much slower than solid-state relays, they have many advantageous properties, such as zero current leakage and low power consumption, which make them potentially useful in next generation computing.

<span class="mw-page-title-main">Inkjet technology</span>

Inkjet technology originally was invented for depositing aqueous inks on paper in 'selective' positions based on the ink properties only. Inkjet nozzles and inks were designed together and the inkjet performance was based on a design. It was used as a data recorder in the early 1950s, later in the 1950s co-solvent-based inks in the publishing industry were seen for text and images, then solvent-based inks appeared in industrial marking on specialized surfaces and in the1990's phase change or hot-melt ink has become a popular with images and digital fabrication of electronic and mechanical devices, especially jewelry. Although the terms "jetting", "inkjet technology" and "inkjet printing", are commonly used interchangeably, inkjet printing usually refers to the publishing industry, used for printing graphical content, while industrial jetting usually refers to general purpose fabrication via material particle deposition.

References

  1. ↑ "High-Speed Switching Enhances Piezoelectric Response in piezoMEMS Devices". AZoSensors. August 30, 2017. Retrieved August 27, 2018.
  2. ↑ "PZT". SINTEF. April 22, 2010. Retrieved August 27, 2018.
  3. 1 2 Polcawich, Ronald; Judy, Daniel; Pulskamp, Jeffrey; Trolier-McKinstry, Susan; Dubey, Madan (June 2007). "Advances in Piezoelectrically Actuated RF MEMS Switches and Phase Shifters". 2007 IEEE/MTT-S International Microwave Symposium: 2083–2086. doi:10.1109/MWSYM.2007.380297. ISBN   978-1-4244-0687-6. ISSN   0149-645X. S2CID   19897747.
  4. 1 2 3 Metzger, Brian. "Piezoelectric MEMS (PiezoMEMS) Patent Portfolio: Thin Film PZT Deposition, Development, Device Designs, and Testing". TechLink. Retrieved August 27, 2018.
  5. ↑ Polcawich, Ronald; Pulskamp, Jeffrey; Judy, Daniel; Ranade, Prashant; Trolier-McKinstry, Susan; Dubey, Madan (December 6, 2007). "Surface Micromachined Microelectromechancial Ohmic Series Switch Using Thin-Film Piezoelectric Actuators". IEEE Transactions on Microwave Theory and Techniques. 55 (12): 2642–2654. Bibcode:2007ITMTT..55.2642P. doi:10.1109/TMTT.2007.910072. S2CID   15283027.
  6. 1 2 Eom, Chang-Beom; Trolier-McKinstry, Susan (November 2012). "Thin-film piezoelectric MEMS". MRS Bulletin. 37 (11): 1007–1017. doi:10.1557/mrs.2012.273. S2CID   110494049.
  7. ↑ Lee, Hee-Chul; Park, Jae-Yeong; Bu, Jong-Uk (April 11, 2005). "Piezoelectrically actuated RF MEMS DC contact switches with low voltage operation". IEEE Microwave and Wireless Components Letters. 15 (4): 202–204. doi:10.1109/LMWC.2005.845689.
  8. 1 2 "Army Research Laboratory (ARL) Scientist Honored as the Department of Defense (DoD) Laboratory Scientist of the Quarter". Department of Defense Research & Engineering Enterprise. Retrieved August 27, 2018.
  9. ↑ Brewer, Steven; Cress, Cory; Williams, Samuel; Zhou, Hanhan; Rivas, Manuel; Polcawich, Ronald; Glaser, Evan; Jones, Jacob; Bassiri-Gharb, Nazanin (July 13, 2017). "Phenomenological Model for Defect Interactions in Irradiated Functional Materials". Scientific Reports. 7 (1): 5308. Bibcode:2017NatSR...7.5308B. doi:10.1038/s41598-017-05071-z. PMC   5509665 . PMID   28706227.
  10. ↑ Polcawich, Ronald (November 2004). "A Piezoelectric MEMS Microphone Based on Lead Zirconate Titanate (PZT) Thin Films". U.S. Army Research Laboratory. Archived from the original on June 3, 2018 – via Defense Technical Information Center.
  11. ↑ Polcawich, Ronald; Pulskamp, Jeffrey; Judy, Daniel; Ranade, Prashant; Trolier-McKinstry, Susan; Dubey, Madan (December 6, 2007). "Surface Micromachined Microelectromechancial Ohmic Series Switch Using Thin-Film Piezoelectric Actuators". IEEE Transactions on Microwave Theory and Techniques. 55 (12): 2642–2654. Bibcode:2007ITMTT..55.2642P. doi:10.1109/TMTT.2007.910072. S2CID   15283027.
  12. ↑ Pulskamp, Jeffrey; Judy, Daniel; Polcawish, Ronald; Kaul, Roger; Chandrahalim, Hengky; Bhave, Sunil (January 2009). Monolithically Integrated Piezomems SP2T Switch and Contour-Mode Filters. 2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems. pp. 900–903. CiteSeerX   10.1.1.162.2655 . doi:10.1109/MEMSYS.2009.4805529. ISBN   978-1-4244-2977-6. S2CID   18225031.
  13. ↑ Pulskamp, Jeffrey (February 2005). "Modeling, Fabrication, and Testing of a Piezoelectric MEMS Vibrational Energy Reclamation Device". U.S. Army Research Laboratory. Archived from the original on June 1, 2018 – via Defense Technical Information Center.
  14. 1 2 Tadigadapa, Srinivas (September 2010). "Piezoelectric microelectromechanical systems — challenges and opportunities". Procedia Engineering. 5: 468–471. doi: 10.1016/j.proeng.2010.09.148 .
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.