A variety of mechanisms that can be used for actuation in Micro-Electro-Mechanical System (MEMS) design include thermal, electrothermal, magnetic, electromagnetic, piezoelectric, magnetostrictive, electrostatic, and shape-memory alloy (SMA), actuation. A multimorph actuator or sensor incorporates two or more materials, wherein each material deforms differently upon application of a stimulus, such as heat, a magnetic field, a voltage potential, among other possible stimuli. A two material multimorph is typically referred to as a bimorph. The materials are typically formed in layers and stacked as shown in
Multimorph actuators are typically composed of topologically straight beams. The theory of straight multimorphs is well developed [S. Timoshenko, Journal of Optical Society of America, vol. 11, pp. 233-256, 1925]. But little attention has been paid to topologically curved multimorphs. Xu et al. reported the fabrication of a 2D electrothermal micromirror actuated by curved bimorphs [Y. Xu, J. Singh, C. S. Premachandran, A. Khairyanto, K. W. S. Chen, N. Chen, C. J. R. Sheppard, and M. Olivo, J. Micromech. Microeng., 18, 125005, 2008]. Shi et al. reported the analysis of curved bimorphs whose constituent layers lie in the same plane [Z. Shi, Smart Mater. and Struct., 14, 835, 2005]. Such structures undergo in-plane bending but do not twist upon actuation. The analysis of curved bimorphs that undergo out-of-plane bending and twisting has not been reported before.
Microactuators can be used in various applications, such as biomedical imaging, optical displays, laser beam steering, communications, space exploration, and surveillance, among other applications. In particular, micoractuators can be used to produce a scanning motion with an object, such as an antenna, radiation beam, laser beam, mirror, among other objects. A micromirror is an optical semiconductor device that has mirror plate moved by one or more microactuators. 2D micromirrors typically utilize two or more actuators for achieving 2D scan and therefore require more than one signal line [A. Jain, PhD Thesis Dissertation, University of Florida, 2006; L. Wu and H. Xie, IEEE Transducers 2007]. Currently, state-of-the-art 2D scanning mirrors employ as many as 4 signal lines [K. Jia, S. Pal, and H. Xie, J. MEMS, 18, 1004-1015, 2009]. This makes system miniaturization difficult. Lammel et al. reported L-shaped actuators that can realize 2D scan using a single actuator [G. Lammel, S. Schweizer, and P. Renaud, Optical Microscanners and Microspectrometers Using Thermal Bimorph Actuators: Kluwer Academic Publishers, 2002]. But such L-shaped actuators produce significant mirror-plate center shift during actuation which makes optical alignment difficult.
Embodiments of the subject invention relate to a method and apparatus for providing a curved multimorph actuator capable of both bending and twisting deformations. Such actuators can be used for various applications, such as, but not limited to biomedical imaging, optical displays, laser beam steering, communications, space exploration, and surveillance, among other applications. In a specific embodiment, such an actuator can be used to produce a scanning motion with an object, such as an antenna, radiation beam, laser beam, mirror, among other objects. In an embodiment, an actuator is used to move an object, such a mirror plate. In a further embodiment, a plurality of actuators is used to move the object. One or more actuators can generate tip/tilt and piston (TTP) motions of the object. In an embodiment, such actuators are capable of rotating the object about an axis. In a particular embodiment, a single actuator is capable of rotating the object about its center without significantly shifting the center of the object in one or more dimensions. In a further embodiment, a single actuator can be used to rotate an object about a first axis and to rotate the same object about a second axis, wherein the first axis and the second axis are mutually perpendicular. In an embodiment, rotation about the first axis and the second axis are achieved sequentially by providing a first stimulus to the actuator to achieve rotation about the first axis and providing a second stimulus to the actuator to achieve rotation about the second axis. In a specific embodiment, rotation about the first axis is produced in response to a first electrical current pattern that heats the actuator in a first pattern and rotation about the second axis is produced in response to a second electrical current pattern that heats the actuator in a second pattern. The first and second current pattern can drive electrical currents to different portions of the actuator, can drive different magnitude electrical currents to all or portions of the actuator, or a combination thereof.
A multimorph actuator can be provided that incorporates a plurality of materials. Each material can exhibit different deformations in response to a stimulus, such as heat. In an embodiment, three or more different materials are used. In another embodiment, a bimorph actuator is incorporating two different materials. The materials of the multimorph can be formed in layers, such as thin-film layers, and stacked. In an embodiment, the layers have uniform thicknesses, widths, and cross-sections. In another embodiment, the thickness of the different layers can vary. In yet another embodiment, the materials can have different widths or cross-sections.
Embodiments of the subject invention relate to a method and apparatus for providing a curved multimorph actuator capable of both bending and twisting deformations. In a specific embodiment, the bimorph can lie in a plane and have a curve in the plane, where the layers of materials are parallel to the plane, and where heat is applied by driving electric current along the length of at least portions of the actuator. The actuator bends out of the plane and twists over at least segments of the length of the actuator. Such actuators can be used for various applications, such as, but not limited to, biomedical imaging, optical displays, laser beam steering, communications, space exploration, and surveillance, among other applications. In a specific embodiment, such an actuator can be used produce a scanning motion with an object, such as an antenna, radiation beam, laser beam, minor, among other objects. In an embodiment, an actuator is used to move an object, such a mirror plate. In a further embodiment, a plurality of actuators is used to move the object. One or more actuators can generate tip/tilt and piston (TTP) motions of the object. In an embodiment, such actuators are capable of rotating the object about an axis. In a particular embodiment, a single actuator is capable of rotating the object about its center without significantly shifting the center of the object in one or more dimensions. In a further embodiment, a single actuator can be used to rotate an object about a first axis and to rotate the same object about a second axis, wherein the first axis and the second axis are mutually perpendicular. In an embodiment, rotation about the first axis and the second axis are achieved sequentially by providing a first stimulus to the actuator to achieve rotation about the first axis and providing a second stimulus to the actuator to achieve rotation about the second axis. In a specific embodiment, rotation about the first axis is produced in response to a first electrical current pattern that heats the actuator in a first pattern and rotation about the second axis is produced in response to a second electrical current pattern that heats the actuator in a second pattern. The first and second current pattern can drive electrical currents to different portions of the actuator, can drive different magnitude electrical currents to all or portions of the actuator, or a combination thereof.
In an embodiment, a multimorph actuator is provided that incorporates a plurality of materials. Each material can exhibit different deformations in response to a stimulus, such as heat. In an embodiment, three or more different materials are used. In another embodiment, a bimorph actuator is provided incorporating two different materials. The materials of the multimorph are formed in layers, such as thin-film layers, and stacked. In an embodiment, the layers have uniform thicknesses, widths, and cross-sections. In another embodiment, the thickness of the different layers can vary. In yet another embodiment, the materials can have different widths or cross-sections.
As further discussed below, embodiments of the subject invention have been validated via analysis and finite element (FE) simulations results. The analysis is applicable to multimorphs of arbitrary shape. The analysis draws upon the theory of multimorphs, S. Timoshenko, Journal of Optical Society of America, vol. 11, pp. 233-256, 1925, and the theory of curved beams, A. E. Armenàkas, Advanced Mechanics of Materials and Applied Elasticity. Boca Raton: CRC Taylor & Francis, 2005.; A. Blake, Handbook of Mechanics, Materials, and Structures. New York: Wiley, 1985.
As in the case of straight bimorphs [S. Pal and H. Xie, J. Micromech. Microeng., 20, 045020, 2010.], key equations in curved bimorph analysis are the beam deformation equations, the force and moment balance equations, and strain continuity at the interface between the two layers. The bending and twisting of curved actuators can be determined based on these equations, allowing the design of curved actuators in accordance with embodiments of the invention.
For small deformations the deflection is given by A. Blake, “Handbook of Mechanics, Materials, and Structures,” New York: Wiley, 1985:
If the beam is clamped at s=0, the boundary conditions are U(0)=0, U′(0)=0 and φ(0)=0. Solving (1) and (2) and imposing boundary conditions,
Then the axial strain produced due to bending moment is given by A. E. Armenàkas, “Advanced Mechanics of Materials and Applied Elasticity,” Boca Raton: CRC Taylor & Francis, 2005:
N1=N2=N (7)
Moment balance gives,
The strains produced in the top and bottom layers match at the interface between the two. The three components of the total axial strain produced in the ith layer are the strain due to axial force (εN
εN
The strain due to bending moment is given by (6). Thermal strain is αiΔT, where αi is the coefficient of thermal expansion of the ith layer and ΔT is the rise in temperature. M. S. Weinberg, J. MEMS, 8, 529-533, 1999. Piezoelectric strain is given by diξi, where di and ξi are the piezoelectric coefficient of the ith layer and the electric field in the ith layer respectively. M. S. Weinberg, J. MEMS, 8, 529-533, 1999. If both thermal and piezoelectric effects are present, εact
εN
The out-of-plane bimorph deflection may be obtained by using (3), (6), (7), (8), (9) and (10),
The beam twist angle may be obtained by using (4). Next, the analytical expressions can be validated against simulation results.
As the calculated deflections are based upon the small deflection theory of curved beams. A. Blake, “Handbook of Mechanics, Materials, and Structures,” New York: Wiley, 1985, large deflections may not follow the calculated deflectors as accurately as smaller deflections. For instance,
As shown by the above analytical and FE simulated results, embodiments of the curved biomorphs can undergo combined out-of-plane bending and twisting upon actuation. In further embodiments, curved bimorphs/multimorphs are produced having arbitrary shapes. By treating the in-plane radius of curvature, R, as a function of the distance along the bimorph s, these further embodiments can be analyzed as discussed above using equations 1-11 and FE analysis. Although illustrative embodiments are discussed herein, other embodiments can have different configurations, stimuli, deformations, and/or functions.
Embodiments of the subject invention significantly decrease or eliminate such center shift. For example, a semicircular actuator is shown in
Embodiments of a curved actuator in accordance with the subject invention can achieve 2D scanning using a single actuator. For example,
Compound actuators, such as lateral-shift-free (LSF) actuators, L. Wu and H. Xie, “A Lateral-Shift-Free and Large-Vertical-Displacement Electrothermal Actuator for Scanning Micromirror/Lens,” presented at IEEE Transducers, Lyon, France, 2007, and inverted-series-connected (ISC) actuators, K. Jia, S. Pal, and H. Xie, “An Electrothermal Tip-Tilt-Piston Micromirror Based on Folded Dual S-Shaped Bimorphs,” Microelectromechanical Systems, Journal of, vol. 18, pp. 1004-1015, 2009, the teachings of both references, which are incorporated by reference herein in their entirety, can also be utilized in accordance with the subject invention. These actuators utilize two or more straight bimorphs and/or multimorphs and rigid beams to achieve large out of plane displacement.
In embodiments, at large deformations, the effective stiffness of the actuators can change significantly from the stiffness in the unactuated state. Therefore, it is possible to realize MEMS devices with variable resonant frequencies.
In embodiments, greater design flexibility may be achieved by using bimorphs and/or multimorphs of different widths. For example,
As also shown in
Curved multimorph test structures and electrothermal micromirrors were fabricated on an SOI wafer with 20 μm device layer thickness. The test results on curved multimorph test structure (Example 1), a circular micromirror (Example 2), and an elliptical micromirror (Example 3).
The actuator embodiments shown and discussed herein are illustrative. Other embodiments are possible including different materials; having different widths, lengths, thicknesses, or radii of curvature; or being subjected to different stimuli.
In an embodiment, one or more suitably programmed computers are used to control one or more stimuli applied to at least one actuator. Such stimuli can include signals transmitted to the at least one actuator. In an embodiment, the one or more suitably programmed computers comprise a processing system as described below.
In an embodiment, a method of controlling at least one actuator is provided including receiving commands, determining one or more stimuli needed to execute the command, and transmitting the one or more stimuli to the at least one actuator. In an embodiment, one or more of steps of the method for are preformed by one or more suitably programmed computers. In a particular embodiment, the determining step is preformed by the one or more suitably programmed computers. Computer-executable instructions for performing these steps can be embodied on one or more computer-readable media as described below. In an embodiment, the one or more suitably programmed computers comprise a processing system as described below.
Aspects of the invention can be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Such program modules can be implemented with hardware components, software components, or a combination thereof. Moreover, those skilled in the art will appreciate that the invention can be practiced with a variety of computer-system configurations, including multiprocessor systems, microprocessor-based or programmable-consumer electronics, minicomputers, mainframe computers, and the like. Any number of computer-systems and computer networks are acceptable for use with the present invention.
Specific hardware devices, programming languages, components, processes, protocols, formats, and numerous other details including operating environments and the like are set forth to provide a thorough understanding of the present invention. In other instances, structures, devices, and processes are shown in block-diagram form, rather than in detail, to avoid obscuring the present invention. But an ordinary-skilled artisan would understand that the present invention can be practiced without these specific details. Computer systems, servers, work stations, and other machines can be connected to one another across a communication medium including, for example, a network or networks.
As one skilled in the art will appreciate, embodiments of the present invention can be embodied as, among other things: a method, system, or computer-program product. Accordingly, the embodiments can take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware. In an embodiment, the present invention takes the form of a computer-program product that includes computer-useable instructions embodied on one or more computer-readable media. Methods, data structures, interfaces, and other aspects of the invention described above can be embodied in such a computer-program product.
Computer-readable media include both volatile and nonvolatile media, removable and nonremovable media, and contemplate media readable by a database, a switch, and various other network devices. By way of example, and not limitation, computer-readable media comprise media implemented in any method or technology for storing information. Examples of stored information include computer-useable instructions, data structures, program modules, and other data representations. Media examples include, but are not limited to, information-delivery media, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile discs (DVD), holographic media or other optical disc storage, magnetic cassettes, magnetic tape, magnetic disk storage, and other magnetic storage devices. These technologies can store data momentarily, temporarily, or permanently. In an embodiment, non-transitory media are used.
The invention can be practiced in distributed-computing environments where tasks are performed by remote-processing devices that are linked through a communications network or other communication medium. In a distributed-computing environment, program modules can be located in both local and remote computer-storage media including memory storage devices. The computer-useable instructions form an interface to allow a computer to react according to a source of input. The instructions cooperate with other code segments or modules to initiate a variety of tasks in response to data received in conjunction with the source of the received data.
The present invention can be practiced in a network environment such as a communications network. Such networks are widely used to connect various types of network elements, such as routers, servers, gateways, and so forth. Further, the invention can be practiced in a multi-network environment having various, connected public and/or private networks.
Communication between network elements can be wireless or wireline (wired). As will be appreciated by those skilled in the art, communication networks can take several different forms and can use several different communication protocols.
Embodiments of the subject invention can be embodied in a processing system. Components of the processing system can be housed on a single computer or distributed across a network as is known in the art. In an embodiment, components of the processing system are distributed on computer-readable media. In an embodiment, a user can access the processing system via a client device. In an embodiment, some of the functions or the processing system can be stored and/or executed on such a device. Such devices can take any of a variety of forms. By way of example, a client device may be a desktop or laptop computer, a personal digital assistant (PDA), an MP3 player, a communication device such as a telephone, pager, email reader, or text messaging device, or any combination of these or other devices. In an embodiment, a client device can connect to the processing system via a network. As discussed above, the client device may communicate with the network using various access technologies, both wireless and wireline. Moreover, the client device may include one or more input and output interfaces that support user access to the processing system. Such user interfaces can further include various input and output devices which facilitate entry of information by the user or presentation of information to the user. Such input and output devices can include, but are not limited to, a mouse, touch-pad, touch-) screen, or other pointing device, a keyboard, a camera, a monitor, a microphone, a speaker, a printer, a scanner, among other such devices. As further discussed above, the client devices can support various styles and types of client applications.
All patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.
It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.
The present application claims the benefit of U.S. Provisional patent application No. 61/350,137, filed Jun. 1, 2010, which is hereby incorporated by reference herein in its entirety, including any figures, tables, or drawings.
The subject invention was made with government support under National Science Foundation, Contract No. 0725598. The government has certain rights to this invention.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US11/38786 | 6/1/2011 | WO | 00 | 12/3/2012 |
Number | Date | Country | |
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61350137 | Jun 2010 | US |