Top cavity cavity for center fixed actuator

Abstract

Flow chambers, cooling systems, and methods are described. A flow chamber includes an upper chamber having a top wall, an actuator, and a lower chamber. The actuator is positioned distal to the top wall. The lower chamber receives fluid from the upper chamber when the actuator is actuated. The top wall includes at least one cavity therein. A cooling system utilizes a cooling unit including the flow chamber. The method includes driving the actuator at a frequency that directs fluid through the flow chamber.

Description

BACKGROUND

[0001] As the speed and computing power of computing devices have increased, the heat generated by computing devices has also increased. Various mechanisms have been proposed to address the generation of heat. Active devices, such as fans, can be used to drive air through large computing devices, such as laptop computers or desktop computers. Passive cooling devices, such as heat sinks, can be used for smaller mobile computing devices, such as smartphones, virtual reality devices, and tablet computers. However, such active and passive devices can not sufficiently cool both mobile devices, such as smartphones, and larger devices, such as laptop computers and desktop computers. Accordingly, additional cooling solutions for computing devices are desired. Moreover, it can be desirable for such cooling systems to be optimized to better provide desired cooling for mobile devices and other devices. BRIEF DESCRIPTION OF DRAWINGS

[0002] Various embodiments of the application are disclosed in the following detailed description and the accompanying drawings.

[0003] Figures 1A-1F An embodiment of an active cooling system is depicted that includes an actuator and a cavity in an upper chamber.

[0004] Figure 2 An embodiment of an active cooling system is depicted that includes an actuator and a cavity in an upper chamber.

[0005] Figure 3 A relationship of back pressure to flow for an embodiment of an active cooling system that includes a centrally anchored actuator is depicted.

[0006] Figures 4A-4B A graph of behavior for an embodiment of an active cooling system that includes a centrally anchored actuator and a cavity is depicted.

[0007] Figure 5 An embodiment of an active cooling system is depicted that includes an actuator and a cavity in an upper chamber.

[0008] Figures 6A-6B An embodiment of an active cooling system is depicted that includes an actuator and a cavity in an upper chamber.

[0009] Figures 7A-7B An embodiment of an active cooling system is depicted that includes an actuator and a cavity in an upper chamber.

[0010] Figure 8 An embodiment of an active cooling system is depicted that includes an actuator and a cavity in an upper chamber.

[0011] Figure 9Embodiments of an active cooling system are depicted that include an actuator and a cavity in an upper chamber.

[0012] Figures 10A-10B Embodiments of an active cooling system are depicted that include an actuator and a cavity in an upper chamber.

[0013] Figures 11A-11C Embodiments of an active cooling system formed in a tile are depicted.

[0014] Figure 12 is a flowchart depicting embodiments of a method for driving flow through a flow chamber. DETAILED DESCRIPTION

[0015] The application can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product of a computer readable storage medium; and / or a processor, such as a processor configured to fetch and execute instructions stored on and / or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the application can take, can be referred to as techniques. In general, the order of the steps of disclosed processes can be altered, unless such alteration would render the process non-functional. Unless otherwise specified, components configured to perform tasks that are described as being configured to perform a task can be implemented as generic components configured to perform the task at a given time, or as specific components manufactured to perform the task. As used in this document, the term “processor” refers to one or more devices, circuits, and / or processing cores configured to process data, such as computer program instructions.

[0016] A detailed description of one or more embodiments of the application is provided below along with accompanying figures that illustrate the principles of the application. The application is described in connection with such embodiments, but the application is not limited to any embodiment. The scope of the application is limited only by the claims and the application encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the application. These details are provided for the purpose of example and the application can be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the application has not been described in detail so that the application is not unnecessarily obscured.

[0017] As semiconductor devices become more powerful, the heat generated during operation also increases. For example, processors of mobile devices such as smartphones, tablets, laptops, and virtual reality devices can operate at high clock speeds, but generate a large amount of heat. Due to the amount of heat generated, the processor can only run at full speed for a relatively short period of time. After this time elapses, throttling occurs (e.g., the processor clock speed slows down). While throttling can reduce heat generation, it also adversely affects processor speed, and thus the performance of the device using the processor. This problem is expected to worsen as technology moves towards 5G and beyond.

[0018] Larger devices, such as laptops or desktop computers, include fans with rotating blades. The fans can be energized in response to an internal component temperature increase. The fans drive air through the larger device to cool the internal components. However, such fans are typically too large for mobile devices such as smartphones or thinner devices such as tablets. The fans can also have limited efficacy due to an air boundary layer present at the surface of the components, providing limited air speed for airflow across the hot surface desired to be cooled, and can generate excess noise. Passive cooling solutions can include components such as heat sinks and heat pipes or vapor chambers to transfer heat to a heat exchanger. While heat sinks alleviate temperature increases at hot spots to some extent, the amount of heat generated in current and future devices can not be adequately addressed. Similarly, the amount of heat transfer that can be provided by heat pipes or vapor chambers is insufficient to remove the excess heat generated. Thus, additional cooling solutions that can be used with smaller mobile devices as well as larger devices are desired.

[0019] While described in the context of cooling systems, the techniques and / or devices described herein can be used in other applications. For example, the actuators can be used in other devices and / or the cooling systems can be used for other purposes. These devices are also described in the context of actuators (i.e., cooling elements) coupled to a support structure at a central region or an edge. In other embodiments, the actuators can be coupled to (e.g., anchored to) the support structure in another manner. For example, the actuators can be attached to the support structure along an edge of the actuators.

[0020] A flow chamber that can be used in a cooling system is described. The flow chamber includes an upper chamber having a top wall, an actuator, and a lower chamber. The actuator is positioned distal to the top wall. The lower chamber receives fluid from the upper chamber when the actuator is activated. The top wall includes at least one cavity therein.

[0021] In some embodiments, the flow chamber includes a support structure. The actuator includes a central region and a periphery. The actuator is supported by the support structure at the central region. At least a portion of the actuator periphery is not fixed. The actuator is configured to undergo a vibrational motion when activated to drive fluid from the upper chamber to the lower chamber. In some embodiments, the actuator includes an anchor region and a cantilever. The anchor region is fixed by the support structure. The cantilever extends outwardly from the anchor region and can include a step region, at least one extension region, and an outer region. The step region extends outwardly from the anchor region and has a step thickness. The extension region extends outwardly from the step region and has an extension thickness that is less than the step thickness. The outer region extends outwardly from the extension region and has an outer thickness that is greater than the extension thickness.

[0022] In some embodiments, the top wall includes at least one vent therein. The actuator is located between the top wall and the lower chamber. In some embodiments, the upper chamber of the flow chamber has a length corresponding to an odd multiple of a wavelength divided by 4. The wavelength is an acoustic wavelength of the frequency of the vibrational motion. The frequency of the vibrational motion corresponds to a structural resonance of the actuator and an acoustic resonance of the upper chamber having the wavelength. In some embodiments, the flow chamber further includes an orifice plate having at least one orifice therein. The orifice plate forms a bottom wall of the lower chamber. The actuator is activated to drive fluid through the at least one orifice. In some embodiments, the length of the one or more cavities is at least 0.25 times the length of the free portion of the actuator and no more than 2 / 3 times the length of the free portion of the actuator. In some embodiments, the width of the cavity is at least 50 microns and no more than 100 microns. In some embodiments, the cavity can have a depth of at least 0.25 times and no more than 1 times the height of the upper chamber (e.g., at least 50 microns and no more than 500 microns).

[0023] In some embodiments, a cooling system is described. The cooling system includes cooling units, each cooling unit including a flow chamber. Accordingly, each cooling unit includes an upper chamber, a cooling element, and a lower chamber. The upper chamber includes a top wall. The cooling element is positioned distal to the top wall. The lower chamber receives fluid from the upper chamber when the cooling element is activated. Further, the top wall includes at least one cavity therein. In some embodiments, each of the plurality of cooling units further includes a support structure. In such embodiments, the cooling element includes a central region and a periphery. Additionally, the cooling element is supported at the central region by the support structure. At least a portion of the periphery is unfixed. The cooling element is configured to undergo a vibrational motion when activated to drive fluid from the upper chamber to the lower chamber. In some embodiments, the actuator includes an anchor region and a cantilever. The anchor region is fixed by the support structure. The cantilever extends outwardly from the anchor region and can include a step region, at least one extension region, and an outer region. The step region extends outwardly from the anchor region and has a step thickness. The extension region extends outwardly from the step region and has an extension thickness that is less than the step thickness. The outer region extends outwardly from the extension region and has an outer thickness that is greater than the extension thickness.

[0024] In some embodiments, the top wall includes at least one vent therein. In such embodiments, the cooling element is positioned between the top wall and the lower chamber. Further, the upper chamber can have a length that corresponds to an odd multiple of a wavelength divided by 4. The wavelength is an acoustic wavelength of a frequency of the vibrational motion. The frequency of the vibrational motion corresponds to a structural resonance of the cooling element and an acoustic resonance of the upper chamber having the wavelength. In some embodiments, each of the cooling units includes an orifice plate having an orifice therein. The orifice plate can form a bottom wall of the lower chamber. The cooling element is activated to drive fluid through the orifice. In some embodiments, the cavity has a length that is at least 0.25 (1 / 4) of the actuator free portion length and no more than 2 / 3 of the actuator free portion length. In some embodiments, a width of the cavity is at least fifty percent and no more than one hundred percent of a width of the chamber. In some embodiments, the cavity can have a depth that is at least 0.25 and no more than 1 times an upper chamber height (e.g., at least 50 microns and no more than 500 microns).

[0025] A method of cooling a heat generating structure is described. The method includes driving a cooling element to induce vibrational motion at a frequency. The cooling element is configured to undergo vibrational motion when driven to direct fluid toward a chamber including an upper chamber, a lower chamber, and the cooling element. The upper chamber includes a top wall. The cooling element is positioned distal to the top wall. The lower chamber receives fluid from the upper chamber when the cooling element is activated. The top wall includes at least one cavity therein. In some embodiments, the cooling element includes a central region and a perimeter. The cooling element is supported by a support structure at the central region. At least a portion of the perimeter is unsecured. The cooling element is configured to undergo vibrational motion when activated to drive fluid from the upper chamber to the lower chamber. The top wall includes a vent therein. An actuator is positioned between the top wall and the lower chamber. In some embodiments, the cavity / cavities are proximate to the perimeter of the cooling element. In some embodiments, the cavity / cavities have a length that is at least 0.25 (1 / 4) of the length of the free portion of the actuator and no more than 2 / 3 of the length of the free portion of the actuator. In some embodiments, the width of the cavity is at least fifty percent and no more than one hundred percent of the width of the chamber. In some embodiments, the cavity can have a depth of at least 0.25 and no more than 1 times the height of the upper chamber (e.g., at least 50 microns and no more than 500 microns).

[0026] Figures 1A-1F is a drawing depicting an exemplary embodiment of an active cooling system 100 that can be used with a heat generating structure 102 and includes a centrally anchored actuator 120. When used in a cooling system, the actuator can also be referred to as a cooling element. Thus, the actuator 120 can also be referred to as a cooling element herein. For clarity, only certain components are shown. Figures 1A-1F Not drawn to scale. Although shown as symmetrical, the cooling system 100 need not be symmetrical.

[0027] Figure 1A and 1B depicts a cross-sectional view and a top view of the cooling system 100. The cooling system 100 includes a top plate 110 having a vent 112 therein, an actuator (or cooling element) 120, an aperture plate 130 having apertures 132 therein, a support structure (or “anchor”) 160, and flow chambers 140 and 150 (collectively, flow chambers 140 / 150) formed therein. In the illustrated embodiment, the top wall of the flow chambers 140 / 150 is formed by the bottom surface of the top plate 110. The top wall of the flow chambers 140 / 150 has a cavity 170 therein. The flow chambers 140 / 150 can thus be considered to be formed between the top plate 110 and the aperture plate 130. The actuator 120 is supported by the anchor 160 at a central region thereof. In Figure 1B In, the actuator 120 is shown by dashed lines and the anchor 160 is shown by dotted / dashed lines. For simplicity, the apertures 132 are not shown inFigure 1B The actuator 120 is closer to and includes a region of the actuator perimeter portion (e.g., the tip 121) that vibrates when actuated. In some embodiments, the tip 121 of the actuator 120 includes a portion of the perimeter that is farthest from the anchor 160 and experiences the greatest deflection during actuation of the actuator 120. For clarity, only one tip 121 of the actuator 120 is labeled in Figure 1A

[0028] Figure 1A and 1B The cooling system 100 is depicted in a neutral position. Thus, the actuator 120 is shown as substantially flat. For in-phase operation, the actuator 120 is driven to vibrate between the positions shown in Figure 1C and 1D This vibrational motion draws fluid (e.g., air) into the vent 112 at high speed and / or high flow rate, through the flow chamber 140 / 150, and out the hole 132. For example, the speed of the fluid impinging the heat-generating structure 102 can be at least thirty meters per second. In some embodiments, the fluid is driven by the actuator 120 toward the heat-generating structure 102 at a speed of at least forty-five meters per second. In some embodiments, the fluid is driven by the actuator 120 toward the heat-generating structure 102 at a speed of at least sixty meters per second. In some embodiments, other speeds are possible. The cooling system 100 is also configured such that little or no fluid is drawn back into the flow chamber 140 / 150 through the hole 132 by the vibrational motion of the actuator 120.

[0029] The heat-generating structure 102 is desirably cooled by the cooling system 100. In some embodiments, the heat-generating structure 102 generates heat. For example, the heat-generating structure can be an integrated circuit. In some embodiments, the heat-generating structure 102 is desirably cooled, but does not itself generate heat. The heat-generating structure 102 can conduct heat (e.g., from a nearby heat-generating object). For example, the heat-generating structure 102 can be a heat sink or a vapor chamber. Thus, the heat-generating structure 102 can include a semiconductor component, including a separate integrated circuit component, such as a processor, other integrated circuit, and / or chip package; a sensor; an optical device; one or more batteries; other components of an electronic device, such as a computing device; a heat sink; a heat pipe; other electronic components, and / or other devices desirably cooled.

[0030] ​The device in which the cooling system 100 is intended to be used may also have limited space to house the cooling system. For example, the cooling system 100 can be used in a computing device. Such a computing device may include, but is not limited to, smartphones, tablets, laptops, tablets, 2-in-1 laptops, handheld gaming systems, digital cameras, virtual reality headsets, augmented reality headsets, mixed reality headsets, and other thin devices. The cooling system 100 may be a microelectromechanical system (MEMS) cooling system capable of residing within a mobile computing device and / or other devices having limited space in at least one dimension. For example, the total height of the cooling system 100 (from the top of the heating structure 102 to the top of the top plate 110) may be less than 2 mm. In some embodiments, the total height of the cooling system 100 is no more than 1.5 mm. In some embodiments, the total height is no more than 250 micrometers. In some embodiments, the total height is no more than 1.1 mm. In some embodiments, the total height is no more than 1 mm. Similarly, the distance y between the bottom of the perforated plate 130 and the top of the heating structure 102 (e.g., ...) Figure 1C The value (as shown) can be small. In some embodiments, y is at least two hundred micrometers and no more than one millimeter. In some embodiments, y is at least two hundred micrometers and no more than three hundred micrometers. Thus, in some embodiments, the distance between the surface of the orifice plate 130 closest to the heating structure 102 and the surface of the top plate 110 furthest from the heating structure 102 is no more than 700 micrometers. Therefore, the cooling system 100 can be used in computing devices and / or other devices with limited space in at least one dimension. However, nothing prevents the use of the cooling system 100 in devices with fewer restrictions on space and / or purposes other than cooling. Although one cooling system 100 (e.g., a cooling unit) is shown, multiple cooling systems 100 can be used in conjunction with the heating structure 102. For example, a one-dimensional or two-dimensional array of cooling units can be utilized.

[0031] The cooling system 100 is in fluid communication with the heat-generating structure 102. The fluid can be a gas or a liquid. For example, the fluid can be air. In some embodiments, the fluid includes fluid from outside the device where the cooling system 100 is located (e.g., provided through an external vent in the device). In some embodiments, the fluid circulates within the device where the cooling system is located (e.g., in a closed device).

[0032] The actuator 120 can be considered to divide the interior of the active cooling system 100 (e.g., the flow chamber 140 / 150) into a top (or upper) chamber 140 and a bottom (or lower) chamber 150. The top chamber 140 is formed by the actuator 120, the sides, and the top plate 110. The bottom chamber 150 is formed by the orifice plate 130, the sides, the actuator 120, and the anchor 160. The top chamber 140 and the bottom chamber 150 are connected at the periphery of the actuator 120 and together form the flow chamber 140 / 150 (e.g., the interior chamber of the cooling system 100).

[0033] The dimensions and configuration of the top chamber 140 can vary depending on the cell (cooling system 100) size, actuator 120 motion, and frequency of operation. The top chamber 140 has a height hi. The height of the top chamber 140 can be selected to provide sufficient pressure to drive fluid to the bottom chamber 150 and through the orifice 132 at a desired flow rate and / or velocity. The top chamber 140 is also sufficiently high so that the actuator 120 does not contact the top plate 110 when actuated. In some embodiments, the height of the top chamber 140 is at least fifty microns and no more than five hundred microns. In some embodiments, the height of the top chamber 140 is at least two hundred microns and no more than three hundred microns.

[0034] The top plate 110 also includes a cavity 170 therein. The cavity 170 is formed by the top plate 110 and the anchor 160. The cavity 170 is configured to receive the actuator 120. The cavity 170 is configured to receive the actuator 120 when the actuator 120 is in a relaxed state. The cavity 170 is configured to receive the actuator 120 when the actuator 120 is in an actuated state. The cavity 170 is configured to receive the actuator 120 when the actuator 120 is in an intermediate state. Figure 1BIn some embodiments, the cavity 170 is depicted by dashed lines. Although shown as having a particular shape (i.e., rectangular), the cavity 170 can have another shape, including but not limited to triangular, oval, circular, and / or diamond shaped. Although the cavity 170 is shown as being symmetrical and having the same shape, in some embodiments, the cavity 170 can have different shapes and / or can be asymmetrical. While shown as being positioned at the outer edge of the flow chamber 140 / 150, the cavity 170 can be positioned elsewhere. The dimensions of the cavity 170 can also vary. The cavity 170 can have a height u of at least fifty microns and no more than four hundred microns (e.g., in some embodiments, at least twenty-five percent of the height hi of the top chamber 140 and no more than one hundred percent of the height of the upper chamber). In some embodiments, the cavity 170 can have a height of no more than two hundred microns (e.g., in some embodiments, no more than fifty percent of the height of the upper chamber). The length vi of the cavity 170 can be at least five hundred microns and no more than 2.5 millimeters (e.g., in some embodiments, at least twenty-five percent of the length of the free portion of the actuator 120 and no more than two-thirds thereof). For example, the free portion of the actuator 120 can have a length Li of three millimeters (e.g., at least one millimeter and no more than five millimeters). In such embodiments, the cavity 170 can have a length of at least 1 millimeter and no more than 2 millimeters. In some embodiments, the cavity 170 can have a length of no more than 1.5 millimeters. In some embodiments, the length vi is at least two times the distance between the tip 121 of the actuator 120 and the outer wall of the top chamber 140 (e.g., twice the length of the edge vent) and no more than one-half of Li. The width v2 of the cavity 170 can be at least one-half of the width Di of the top chamber 140 and no more than the width of the upper chamber. In some embodiments, the cavity 170 has a width of at least 6 millimeters and no more than 8 millimeters. In some embodiments, other shapes can be used for the cavity 170. In some such embodiments, it can be desirable for the area of the cavity to be in the same range as the rectangular cavity indicated above. As a result of the presence of the cavity 170, the top plate 110 can be considered to have a varying thickness, the top chamber 140 (and the flow chamber 140 / 150) can be considered to have a varying height, and the flow chamber 140 / 150 can be considered to have a top surface with the cavity 170 therein.

[0035] The top plate 110 includes a vent 112 through which fluid can be drawn into the cooling system 100. The vent 112 may have a size selected based on the desired sound pressure level in the top chamber 140. For example, in some embodiments, the width w of the vent 112 is at least 500 micrometers and no more than 1,000 micrometers. In some embodiments, the width of the vent 112 is at least 250 micrometers and no more than 2,000 micrometers. In the illustrated embodiment, the vent 112 is a centrally located opening in the top plate 110. In other embodiments, the vent 112 may be located elsewhere. For example, the vent 112 may be closer to one of the edges of the top plate 110. The vent 112 may have a circular, rectangular, or other shaped footprint. Although a single vent 112 is shown, multiple vents may also be used. For example, the vents may be offset toward the edge of the top chamber 140 or located on one or more sides of the top chamber 140. In some embodiments, multiple vents offset from the page plane may be used.

[0036] The bottom chamber 150 has a height h2. In some embodiments, the height of the bottom chamber 150 is sufficient to accommodate the movement of the actuator 120. Therefore, during normal operation, no part of the actuator 120 contacts the orifice plate 130. The bottom chamber 150 is typically smaller than the top chamber 140 and can help reduce backflow of fluid into the orifice 132. In some embodiments, the height of the bottom chamber 150 is the maximum deflection of the actuator 120 plus at least 5 micrometers and no more than 10 micrometers. In some embodiments, the deflection of the actuator 120 (e.g., the deflection of the tip 121) has an amplitude z of at least 10 micrometers and no more than 100 micrometers (e.g., ...). Figure 1D (As shown). In some such embodiments, the deflection amplitude of actuator 120 is at least 10 micrometers and no more than 60 micrometers. However, the deflection amplitude of actuator 120 depends on factors such as the desired flow rate through cooling system 100 and the configuration of cooling system 100. Therefore, the height of bottom chamber 150 generally depends on the flow rate through cooling system 100 and other components of cooling system 100.

[0037] Anchor (support structure) 160 supports actuator 120 at its central portion. Therefore, at least a portion of the periphery of actuator 120 is not fixed and vibrates freely. In some embodiments, anchor 160 extends along the central axis of actuator 120 (e.g., perpendicular to...). Figures 1A-1FIn such embodiments, the portion of the actuator 120 (e.g., including the tip 121) that vibrates moves in a cantilevered fashion. Thus, portions of the actuator 120 can move in a manner similar to a butterfly wing (i.e., in phase) and / or in a manner similar to a seesaw (i.e., out of phase). Accordingly, the portion of the actuator 120 that vibrates in a cantilevered fashion vibrates in phase in some embodiments and out of phase in other embodiments. In some embodiments, the anchor 160 does not extend along the axis of the actuator 120. In such embodiments, all portions of the periphery of the actuator 120 are free to vibrate (e.g., similar to a jellyfish). In the illustrated embodiment, the anchor 160 supports the actuator 120 from the bottom of the actuator 120. In other embodiments, the anchor 160 can support the actuator 120 in another manner. For example, the anchor 160 can support the actuator 120 from the top (e.g., the actuator 120 hangs from the anchor 160). In some embodiments, the anchor 160 has a width a of at least 0.5 millimeters and no more than 4 millimeters. In some embodiments, the anchor 160 has a width of at least two millimeters and no more than 2.5 millimeters. The anchor 160 can occupy at least ten percent and no more than fifty percent of the actuator 120.

[0038] The actuator 120 has a first side distal from the heat-generating structure 102 and a second side proximal to the heat-generating structure 102. In the illustrated embodiment, the first side of the actuator 120 is the top of the actuator 120 (further from the aperture plate 130), and the second side is the bottom of the actuator 120 (closer to the aperture plate 130). The actuator 120 is actuated to undergo a vibrational motion, as illustrated. Figures 1A-1F Figures 1A-1F The vibrational motion of the actuator 120 drives fluid from the first side of the actuator 120 distal from the heat-generating structure 102 (e.g., from the top chamber 140) to the second side of the actuator 120 proximal to the heat-generating structure 102 (e.g., to the bottom chamber 150). In other words, actuation of the actuator 120 directs fluid through the flow chambers 140 / 150 and from the top chamber 140 to the bottom chamber 150. The vibrational motion of the actuator 120 also draws fluid through the vent 112 and into the top chamber 140; forces fluid to flow from the top chamber 140 to the bottom chamber 150; and drives fluid from the bottom chamber 150 through the apertures 132 of the aperture plate 130.

[0039] The actuator 120 has a length L that depends on the frequency at which the actuator 120 is desired to vibrate. In some embodiments, the length of the actuator 120 is at least four millimeters and no more than ten millimeters. In some such embodiments, the actuator 120 has a length of at least six millimeters and no more than eight millimeters. The depth D (as illustrated) of the actuator 120 (e.g., perpendicular to the length L) is at least 0.5 millimeters and no more than 2.5 millimeters in some embodiments. Figure 1B Figure 1A 1C ​​​The plane shown in -1F can vary from one-quarter to twice the length of L. For example, actuator 120 can have a depth equal to its length. The thickness t of actuator 120 can vary based on the configuration of actuator 120 and / or the frequency at which actuator 120 is expected to be actuated. In some embodiments, for actuator 120 with a length of eight millimeters and driven at a frequency of at least 20 kHz and no more than 25 kHz, the actuator thickness is at least two hundred micrometers and no more than three hundred and fifty micrometers. The length C of flow chamber 140 / 150 is close to the length L of actuator 120. For example, in some embodiments, the distance d between the edge of actuator 120 and the wall of flow chamber 140 / 150 is at least one hundred micrometers and no more than one thousand micrometers. In some embodiments, d is at least one hundred micrometers and no more than five hundred micrometers. In some such embodiments, d is at least three hundred micrometers. In some embodiments, d is at least two hundred micrometers and no more than three hundred micrometers. In some embodiments, d is no more than eight hundred micrometers. This distance d can be referred to as an edge vent.

[0040] In the illustrated embodiment, the actuator 120 is anchored by the anchor 160 along the central axis (in... Figure 1A Outside the plane of the page, the cantilever 123 is supported (held in place) at the central portion 122 (hereinafter referred to as the anchoring area 122). Therefore, the cantilever 123, which is actuated to vibrate, is supported (held in place) only at the central portion 122 (hereinafter referred to as the anchoring area 122). Figure 1B (Indicated in the middle) on the right and left sides of the anchor 160. In some embodiments, the actuator 120 is a continuous structure having two parts (e.g., cantilever 123) that are free and actuated. In some embodiments, the actuator 120 includes separate cantilever sections, each of which is attached to and actuated by the anchor 160. The cantilever 123 of the actuator 120 can be driven to vibrate in a manner similar to a butterfly wing (in phase) or a seesaw (out of phase).

[0041] Despite Figures 1A-1FThe piezoelectric can be positioned only on or in the cantilever 123 of the actuator 120 in some embodiments. In some embodiments, the piezoelectric can be on or in all of the actuator 120. Thus, the actuator 120 can be a multilayer actuator in which the piezoelectric is integrated into the actuator 120. For example, the actuator 120 can include a piezoelectric layer on a substrate. The substrate can be a stainless steel, a Ni alloy, and / or a Hastelloy substrate. In some embodiments, the piezoelectric layer includes a plurality of sub-layers formed as a thin film on the substrate. In other embodiments, the piezoelectric layer can be a bulk layer attached to the substrate. Such a piezoelectric actuator 120 also includes electrodes for activating the piezoelectric. In some embodiments, the substrate functions as the electrodes. In other embodiments, a bottom electrode can be disposed between the substrate and the piezoelectric layer. Other layers can be included in the piezoelectric actuator including, but not limited to, a seed layer, a capping layer, a passivation layer, or other layers. Although described in the context of a piezoelectric, another mechanism for actuating the actuator 120 can be utilized. Such other mechanisms can be on the actuator 120 (e.g., attached to the actuator 120), integrated into the actuator 120, or can be positioned elsewhere (e.g., on the anchor 160).

[0042] In Figure 1B In the illustrated embodiment, the anchor 160 extends most, but not all, of the depth D of the actuator 120. The entire perimeter of the actuator 120 is free. However, the anchor 160 still holds the center of the actuator 120, the anchored region 122, in place. Thus, the anchor 160 need not extend the entire length of the center axis for the cantilever 123 to vibrate as desired. In some embodiments, the anchor 160 extends to the perimeter of the actuator 120 along the center axis. In some such embodiments, the anchor 160 has a depth of at least D.

[0043] Although the actuator 120 is depicted as rectangular, the actuator can have another shape. In some embodiments, the corners of the actuator 120 can be rounded. In some embodiments, the entire cantilever 123 can be rounded. Other shapes are possible as well. For example, in some embodiments, the anchor can be confined to a region near the center of the actuator. In some such embodiments, the actuator can be symmetric about the anchor. For example, the anchor 160 and the actuator 120 can have a circular footprint. Such an actuator can be configured to vibrate in a manner similar to a jellyfish or in a manner similar to the opening / closing of an umbrella. In some embodiments, the entire perimeter of such an actuator vibrates in phase (e.g., moves up and down together). In other embodiments, portions of the perimeter of such an actuator vibrate out of phase.

[0044] The actuator 120 can be driven at a frequency that is at or near the resonance frequency of both the acoustic resonance of the pressure wave in the fluid in the top chamber 140 and the resonance frequency of the structural resonance of the actuator 120. The portion of the actuator 120 (e.g., the cantilevered section with length (L-a) / 2) that experiences vibrational motion is driven at or near the resonance of the actuator 120 (the structural resonance). In some embodiments, this portion of the actuator 120 that experiences vibration can be the cantilevered section. The frequency of the vibration for the structural resonance is referred to as the structural resonance frequency. Using the structural resonance frequency in driving the actuator 120 reduces the power consumption of the cooling system 100. The actuator 120 and the top chamber 140 can also be configured such that this structural resonance frequency corresponds to the resonance of the pressure wave in the fluid being driven through the top chamber 140 (the acoustic resonance of the top chamber 140). The frequency of this pressure wave is referred to as the acoustic resonance frequency. At the acoustic resonance, a node in pressure occurs near the vent 112 and an antinode in pressure occurs near the periphery of the cooling system 100 (e.g., near the tip 121 of the actuator 120 and near the junction between the top chamber 140 and the bottom chamber 150). The distance between these two regions is C / 2. Thus, where is the acoustic wavelength of the fluid and n is an odd number (e.g., n = 1, 3, 5, etc.). For the lowest order mode, Because the length of the top chamber 140 (e.g., C) is close to the length of the actuator 120, in some embodiments, is also approximately true, where is the acoustic wavelength of the fluid and n is an odd number. Thus, the frequency at which the actuator 120 is driven is at or near the structural resonance frequency of the actuator 120. For at least the top chamber 140, the frequency is also at or near the acoustic resonance frequency. The acoustic resonance frequency of the top chamber 140 typically varies less dramatically with changes in parameters such as temperature and size than the structural resonance frequency of the actuator 120. Thus, in some embodiments, the actuator 120 can be driven at (or closer to) the structural resonance frequency rather than the acoustic resonance frequency.

[0045] Orifice plate 130 has holes 132 therein. Although a particular number and distribution of holes 132 are shown, other numbers and / or other distributions can be used. A single orifice plate 130 is used for a single cooling system 100. In other embodiments, multiple cooling systems 100 can share an orifice plate. For example, multiple units 100 can be provided together in a desired configuration. In such embodiments, the units 100 can be the same size and configuration or different sizes and / or configurations. Holes 132 are shown as having an axis oriented normal to the surface of heat generating structure 102. In other embodiments, the axis of one or more holes 132 can be at another angle. For example, the angle of the axis can be selected from substantially zero degrees and a non-zero acute angle. Holes 132 also have sidewalls that are substantially parallel to the surface normal of orifice plate 130. In some embodiments, the holes can have sidewalls that are at a non-zero angle to the surface normal of orifice plate 130. For example, holes 132 can be tapered. Further, although orifice plate 130 is shown as substantially flat, in some embodiments, grooves and / or other structures can be provided in orifice plate 130 to modify the configuration of bottom chamber 150 and / or the area between orifice plate 130 and heat generating structure 102.

[0046] The size, distribution, and location of the holes 132 are selected to control the flow rate of fluid driven to the surface of the heat generating structure 102. The location and configuration of the holes 132 can be configured to increase / maximize the fluid flow from the bottom chamber 150 through the holes 132 to the ejection channel (the area between the bottom of the orifice plate 130 and the top of the heat generating structure 102). The location and configuration of the holes 132 can also be selected to reduce / minimize the suction flow (e.g., backflow) from the ejection channel through the holes 132. For example, it is desirable for the location of the holes to be far enough from the tip 121 so that the suction force in the upstroke of the actuator 120 (the tip 121 is far from the orifice plate 130) is reduced that would pull fluid through the holes 132 into the bottom chamber 150. It is also desirable for the location of the holes to be close enough to the tip 121 so that the suction force in the upstroke of the actuator 120 also allows the higher pressure from the top chamber 140 to push fluid from the top chamber 140 into the bottom chamber 150. In some embodiments, the ratio of the flow rate from the top chamber 140 into the bottom chamber 150 in the upstroke to the flow rate through the holes 132 from the ejection channel (“net flow ratio”) is greater than 2: 1. In some embodiments, the net flow ratio is at least 85: 15. In some embodiments, the net flow ratio is at least 90: 10. To provide the desired pressure, flow rate, suction force, and net flow ratio, it is desirable for the holes 132 to be at least a distance r1 from the tip 121 and no more than a distance r2 from the tip 121 of the actuator 120. In some embodiments, r1 is at least one hundred microns (e.g., r1 > 100 pm) and r2 is no more than one millimeter (e.g., r2 < 1000 pm). In some embodiments, the holes 132 are at least two hundred microns (e.g., r1 > 200 pm) from the tip 121 of the actuator 120. In some such embodiments, the holes 132 are at least three hundred microns (e.g., r1 > 300 pm) from the tip 121 of the actuator 120. In some embodiments, the holes 132 have a width o of at least one hundred microns and no more than five hundred microns. In some embodiments, the holes 132 have a width o of at least two hundred microns and no more than three hundred microns. In some embodiments, the hole spacing s is at least one hundred microns and no more than one millimeter. In some such embodiments, the hole spacing is at least four hundred microns and no more than six hundred microns. In some embodiments, it is also desirable for the holes 132 to occupy a particular portion of the area of the orifice plate 130. For example, the holes 132 can cover at least five percent and no more than fifteen percent of the footprint of the orifice plate 130 in order to obtain the desired flow rate of fluid through the holes 132. In some embodiments, the holes 132 cover at least eight percent and no more than twelve percent of the footprint of the orifice plate 130.

[0047] In some embodiments, cooling system 100 includes a vent (not shown) or other duct. Such a duct provides a path for the heated fluid to flow away from heat generating structure 102. In some embodiments, the duct returns the fluid to the side of ceiling 110 away from heat generating structure 102. In some embodiments, the duct can instead direct the fluid away from heat generating structure 102 in a direction parallel to heat generating structure 102 or perpendicular to heat generating structure 102, but in the opposite direction (e.g., toward the bottom of the page). For devices that use fluid external to cooling system 100, the duct can direct the heated fluid to a vent. In such embodiments, additional fluid can be provided from an inlet vent. In embodiments where the device is enclosed, the duct can provide a circuitous path back to the area near vent 112 and away from heat generating structure 102. Such a path allows the fluid to dissipate heat before being used again to cool heat generating structure 102. In other embodiments, the duct can be omitted or otherwise configured. Thus, allowing fluid to take heat away from heat generating structure 102.

[0048] Operation of cooling system 100 is described in the context of Figures 1A-1F Operation of cooling system 100 is described in the context of Figures 1C-1D An in-phase operation of cooling system 100 is depicted. Referring to Figure 1C , actuator 120 has been actuated such that its tip 121 is moving away from ceiling 110. Thus, Figure 1C may be considered to depict the end of the downstroke of actuator 120. Due to the oscillating motion of actuator 120, the size of gap 152 of bottom chamber 150 has decreased and is shown as gap 152B. Conversely, the size of gap 142 of top chamber 140 has increased and is shown as gap 142B. During the downstroke, a lower (e.g., minimum) pressure is created at the periphery when actuator 120 is at the neutral position. As the downstroke continues, the size of bottom chamber 150 decreases and the size of top chamber 140 increases, as Figure 1CThe fluid is driven out of the hole 132. The fluid driven from the hole 132 can travel in a direction that is normal to the surface of the orifice plate 130 and / or the top surface of the heat generating structure 102. The fluid is driven from the hole 132 at a high velocity, for example, more than thirty-five meters per second, toward the heat generating structure 102. In some embodiments, the fluid then travels along the surface of the heat generating structure 102 and toward the periphery of the heat generating structure 102, where the pressure is lower than the pressure near the hole 132. Also in the downstroke, the size of the top chamber 140 increases, and there is a lower pressure in the top chamber 140. As a result, fluid is drawn into the top chamber 140 through the vent 112. The motion of the fluid into the vent 112, through the hole 132, and along the surface of the heat generating structure 102 is shown by the unlabelled arrows in Figure 1C

[0049] The actuator 120 is also actuated so that the tip 121 moves away from the heat generating structure 102 and toward the top plate 110. Thus, it can be considered that Figure 1D The end of the upstroke of the actuator 120 is depicted. As a result of the motion of the actuator 120, the size of the gap 142 has decreased, and is shown as gap 142C. The size of the gap 152 has increased, and is shown as gap 152C. During the upstroke, a higher pressure is created at the periphery when the actuator 120 is at the neutral position. As the upstroke continues, the size of the bottom chamber 150 increases, and the size of the top chamber 140 decreases, as shown by the unlabelled arrows in Figure 1D As a result, fluid is driven from the top chamber 140 (e.g., the periphery of the flow chamber 140 / 150) to the bottom chamber 150. Thus, the top chamber 140 acts as a nozzle into which fluid is accelerated and driven toward the bottom chamber 150 as the tip 121 of the actuator 120 moves upward. The motion of the fluid into the bottom chamber 150 is shown by the unlabelled arrows in Figure 1D The position and configuration of the actuator 120 and the hole 132 are selected to reduce the suction and, thus, the backflow of fluid from the jetting channel (between the heat generating structure 102 and the orifice plate 130) into the hole 132 during the upstroke. Thus, the cooling system 100 is able to drive fluid from the top chamber 140 to the bottom chamber 150 without an undue amount of backflow of heated fluid from the jetting channel into the bottom chamber 150.

[0050] The motion between the positions shown in Figure 1C and 1D is repeated. Thus, the actuator 120 experiences Figures 1C-1D ​The illustrated vibrational motion thereby draws fluid from distal to the top plate 110 through the vent 112 into the top chamber 140; transfers fluid from the top chamber 140 to the bottom chamber 150; and pushes fluid through the holes 132 and toward the heat generating structure 102. As described above, the actuator 120 is driven so as to vibrate at or near the structural resonant frequency of the actuator 120. Further, the structural resonant frequency of the actuator 120 is configured to align with the acoustic resonant frequency of the flow chambers 140 / 150. The structural and acoustic resonant frequencies are typically selected to be in the ultrasonic range. For example, the vibrational motion of the actuator 120 can be at a frequency from 15 kHz to 30 kHz. In some embodiments, the actuator 120 vibrates at a frequency of at least 20 kHz and no greater than 30 kHz. The structural resonant frequency of the actuator 120 is within ten percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the actuator 120 is within five percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the actuator 120 is within three percent of the acoustic resonant frequency of the cooling system 100. As a result, efficiency and flow rates can be improved. However, other frequencies can also be used.

[0051] The fluid driven toward the heat generating structure 102 can move substantially normal (perpendicular) to the top surface of the heat generating structure 102. In some embodiments, the fluid motion can have a non-zero acute angle with respect to the normal of the top surface of the heat generating structure 102. In either case, the fluid can be thin and / or form an orifice in the fluid boundary layer at the heat generating structure 102. As a result, heat transfer from the heat generating structure 102 can be improved. The fluid diverges from the heat generating structure 102, traveling along the surface of the heat generating structure 102. In some embodiments, the fluid moves in a direction substantially parallel to the top of the heat generating structure 102. As a result, heat from the heat generating structure 102 can be extracted by the fluid. The fluid can exit the area between the orifice plate 130 and the heat generating structure 102 at the edge of the cooling system 100. A vent or other duct (not shown) at the edge of the cooling system 100 allows the fluid to be carried away from the heat generating structure 102. In other embodiments, the heated fluid can be further transferred from the heat generating structure 102 in another manner. The fluid can exchange heat transferred from the heat generating structure 102 to another structure or the ambient environment. As a result, the fluid at the distal side of the top plate 110 can remain relatively cool, thereby allowing additional heat extraction. In some embodiments, the fluid circulates, returning to the distal side of the top plate 110 after cooling. In other embodiments, the heated fluid is carried away and replaced by new fluid at the distal side of the actuator 120. As a result, the heat generating structure 102 can be cooled.

[0052] Figures 1E-1FAn embodiment of an active cooling system 100 is depicted that includes a centrally anchored actuator 120 in which the actuator is driven out of phase. More specifically, segments of the actuator 120 on opposite sides of the anchor 160 (and thus on opposite sides of a central region of the actuator 120 that is supported by the anchor 160) are driven to vibrate out of phase. In some embodiments, the segments of the actuator 120 on opposite sides of the anchor 160 are driven 180 degrees out of phase or close to 180 degrees out of phase. Thus, one segment of the actuator 120 vibrates toward the top plate 110 while another segment of the actuator 120 vibrates toward the orifice plate 130 / heat generating structure 102. Movement of the segments of the actuator 120 toward the top plate 110 (upstroke) drives fluid in the top chamber 140 to the bottom chamber 150 on that side of the anchor 160. Movement of the segments of the actuator 120 toward the orifice plate 130 drives fluid through the orifices 132 and toward the heat generating structure 102. Thus, fluid traveling at high speed (e.g., at the speeds described with respect to in-phase operation) is alternately driven out of the orifices 132 on opposite sides of the anchor 160. In Figure 1E and 1F In

[0053] The motion between the positions shown in Figure 1E and 1F is repeated. Thus, the actuator 120 undergoes a vibrational motion as shown in Figure 1A , 1E and IF, alternately drawing fluid into the top chamber 140 on each side of the actuator 120 from a distance from the top plate 110 through the vents 112; passing fluid from each side of the top chamber 140 to the corresponding side of the bottom chamber 150; and pushing fluid through the orifices 132 on each side of the anchor 160 and toward the heat generating structure 102. As discussed above, the actuator 120 is driven so as to vibrate at or near a structural resonant frequency of the actuator 120. Further, the structural resonant frequency of the actuator 120 is configured to align with an acoustic resonant frequency of the flow chambers 140 / 150. The structural and acoustic resonant frequencies are typically selected to be in the ultrasonic range. For example, the vibrational motion of the actuator 120 can be at the frequencies described for in-phase vibration. The structural resonant frequency of the actuator 120 is within ten percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the actuator 120 is within five percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the actuator 120 is within three percent of the acoustic resonant frequency of the cooling system 100. Thus, efficiency and flow rates can be improved. However, other frequencies can also be used.

[0054] Fluids driven toward the heat-generating structure 102 to oscillate out of phase can move substantially normal (perpendicular) to the top surface of the heat-generating structure 102 in a manner similar to the in-phase operation described above. Similarly, vents or other ducts (not shown) at the edges of the cooling system 100 allow the fluids to be carried away from the heat-generating structure 102. In other embodiments, the heated fluids can be further transferred from the heat-generating structure 102 in another manner. The fluids can exchange heat transferred from the heat-generating structure 102 to another structure or the ambient environment. As a result, the fluids at the distal side of the top plate 110 can remain relatively cool, allowing additional heat extraction. In some embodiments, the fluids circulate, returning to the distal side of the top plate 110 after cooling. In other embodiments, the heated fluids are carried away and replaced by new fluids at the distal side of the actuator 120. As a result, the heat-generating structure 102 can be cooled.

[0055] With the cooling system 100 actuated for in-phase or out-of-phase vibration, fluid drawn in through the vent 112 and driven through the aperture 132 can be efficiently cooled from the heat-generating structure 102. Because the fluid impinges on the heat-generating structure at a sufficient speed (e.g., at least thirty meters per second) and, in some embodiments, substantially normal to the heat-generating structure, the fluid boundary layer at the heat-generating structure can be thinned and / or partially removed. As a result, heat transfer between the heat-generating structure 102 and the moving fluid is improved. Because the heat-generating structure is more efficiently cooled, the corresponding integrated circuit can be run at a higher speed and / or power for a longer period of time. For example, if the heat-generating structure corresponds to a high-speed processor, such a processor can be run for a longer period of time before throttling. As a result, the performance of a device utilizing the cooling system 100 can be improved. Moreover, the cooling system 100 can be a MEMS device. Thus, the cooling system 100 can be suitable for use in smaller and / or mobile devices where space is limited, such as smartphones, other mobile phones, virtual reality headsets, tablets, two-in-one computers, wearable devices, and handheld games. As a result, the performance of such devices can be improved. Because the actuator 120 can vibrate at a frequency of 15 kHz or higher, any noise associated with actuation of the actuator can not be audible to a user. If driven at or near a structural and / or acoustic resonance frequency, the power used in operating the cooling system can be significantly reduced. During vibration, the actuator 120 does not physically contact the top plate 110 or the aperture plate 130. As a result, the resonance of the actuator 120 can be more easily maintained. More specifically, physical contact between the actuator 120 and other structures interferes with the resonance conditions of the actuator 120. Interfering with these conditions can drive the actuator 120 out of resonance. As a result, additional power would be required to maintain actuation of the actuator 120. Moreover, the fluid flow driven by the actuator 120 can be reduced. By using a differential pressure and fluid flow as described above, these problems can be avoided. The benefits of improved quiet cooling can be achieved with limited additional power. Moreover, out-of-phase vibration of the actuator 120 allows the center of mass position of the actuator 100 to remain more stable. Although torque is applied to the actuator 120, the force resulting from center of mass motion is reduced or eliminated. As a result, vibrations resulting from motion of the actuator 120 can be reduced. Moreover, by using out-of-phase vibration motion to both sides of the actuator 120, the efficiency of the cooling system 100 can be improved. As a result, the performance of a device incorporating the cooling system 100 can be improved. Moreover, the cooling system 100 can be used in other applications (e.g., with or without the heat-generating structure 102) where high fluid flow and / or speed is desired.

[0056] The cavity 170 within the flow chambers 140 / 150 can provide additional benefits to the operation of the cooling system 100. As previously mentioned, the pressure in the top chamber 140 increases during the upward stroke of the actuator 120 tip. The presence of the cavity 170 mitigates this pressure increase. The cavity 170 is configured such that sufficient pressure is generated to drive fluid from the top chamber 140 to the bottom chamber 150. This... Figure 1D , 1E (Right / upward stroke portion of actuator 120) and 1F (left / upward stroke portion of actuator 120) are indicated by arrows indicating fluid movement. However, because the pressure has been reduced, the pressure resisted by the tip 121 of actuator 120 during the upward stroke has been reduced by the pressure in the top chamber (e.g., having a cavity 170) excluding the cavity 170. Figure 1A , Figure 1C and Figure 1E The pressure is lower in the top chamber (indicated by the dashed line at a constant height). Therefore, in embodiments including cavity 170, the power required to drive actuator 120 during the upward stroke can be reduced. Thus, in addition to the benefits discussed above, the power required to drive actuator 120 can be reduced while maintaining fluid flow and velocity.

[0057] Similarly, the edge vent (the distance d between the tip 121 of actuator 120 and the outer wall of flow chambers 140 / 150) can be used to adjust the pressure in the top chamber 140 and the bottom chamber 150. Generally, a smaller edge vent (lower d) results in higher pressure in the top chamber 140, while a larger edge vent (higher d) results in lower pressure in the top chamber 140. Although the pressure can vary, the pressure variation can be limited within a certain range of edge vent sizes. For example, within the range discussed herein (e.g., at least one hundred micrometers and no more than one thousand micrometers, or at least three hundred micrometers and no more than eight hundred micrometers), the pressure actuator 120 is driven to reduce resistance to increase the size of the edge vent while substantially not reducing the flow rate. Therefore, the power consumed by driving actuator 120 can be reduced. The size of the edge vent can be adjusted in many ways. The flow chambers 140 / 150 can be made longer (e.g., C increases) without increasing the length of the actuator 120, the actuator 120 can be made shorter (e.g., L decreases), and / or the actuator 120 and anchor 160 can be made shorter (L and a decrease). Increasing the length of the flow chambers 140 / 150 increases the size of the edge vents without changing the structural resonance of the actuator 120. Decreasing the length of the actuator 120 and the anchor 160 can increase the size of the edge vents while maintaining the structural resonance frequency (i.e., decreasing L and a so that the free cantilever portion of the actuator 120 remains the same length).

[0058] Figure 2 An embodiment of an active cooling system 200 is depicted, including a centrally anchored engineered actuator. Figure 2 This is not drawn to scale. For simplicity, only a portion of the cooling system 200 is shown. The cooling system 200 is similar to the cooling system 100. Therefore, similar components have similar labels. For example, the cooling system 200 is used in conjunction with a heating structure 202 similar to the heating structure 102. The cooling system 200 includes a top plate 210 with vents 212, an actuator 220, an orifice plate 230 with holes 232, a top chamber 240 with gaps, a bottom chamber 250 with gaps, flow chambers 240 / 250, an anchor (i.e., support structure) 260, and a cavity 270, which are respectively similar to the top plate 110 with vents 112, the actuator 120, the orifice plate 130 with holes 132, the top chamber 140 with gaps 142, the bottom chamber 150 with gaps 152, the flow chambers 140 / 150, the anchor (i.e., support structure) 160, and the cavity 170. Therefore, the actuator 220 is centrally supported by the anchor 260, allowing at least a portion of the periphery of the actuator 220 to vibrate freely.

[0059] Actuator 220 includes anchoring regions 222 and cantilever 223, which are similar to anchoring regions 122 and cantilever 123. The spacing between anchoring regions 222 and cantilever 223 is indicated by a dashed line. Each cantilever 223 terminates in a tip 221. Anchoring regions 222 are supported (e.g., held in place) in cooling system 200 by anchors 260. Cantilever 223 undergoes vibratory motion in response to actuation of actuator 220.

[0060] Actuator 220 can also be considered an engineered actuator because each cantilever 223 includes a stepped region 224, an extension region 226, and an outer region 228. Figure 2 In the illustrated embodiment, the anchoring region 222 is positioned at the center. A stepped region 224 extends outward from the anchoring region 222 (towards the tip 121). An extension region 226 extends outward from the stepped region 224. An outer region 228 extends outward from the extension region 226. In other embodiments, the anchoring region 222 may be at one edge of the actuator, and the outer region 228 at the opposite edge. In such an embodiment, the actuator is edge-anchored.

[0061] The thickness of the extension region 226 (extension thickness) is less than the thickness of the step region 224 (step thickness) and less than the thickness of the outer region 228 (outer thickness). Thus, the extension region 226 can be considered to be recessed. The extension region 226 can also be considered to provide a larger bottom chamber 250. In some embodiments, the outer thickness of the outer region 228 is the same as the step thickness of the step region 224. In some embodiments, the outer thickness of the outer region 228 is different than the step thickness of the step region 224. Thus, in various embodiments, the outer region 228 can be thicker than the extension region 224 or thinner than the extension region 224. The outer thickness of the outer region 228 and the step thickness of the step region 224 are each at least three hundred micrometers and no greater than three hundred sixty micrometers. In other embodiments, other thicknesses are possible. In some embodiments, the step (difference between the step region thickness and the extension region thickness) is at least fifty micrometers and no greater than two hundred micrometers. In some embodiments, the outer step (difference between the outer region thickness and the extension region thickness) is at least fifty micrometers and no greater than two hundred micrometers. The outer region 228 can have a width (from the inner edge of the step region 226 to the tip 221) of at least one hundred micrometers and no greater than three hundred micrometers. In some embodiments, the extension region 226 has a length (from the step region 224 to the outer region 228) of at least 0.5 millimeters and no greater than 1.5 millimeters. In some embodiments, the outer region 228 has a higher mass per length (in the direction from the anchor region 222 towards the tip 221) than the extension region 226. This difference in mass can be due to the larger size / thickness of the outer region 228, a difference in density between portions of the actuator 220, and / or another mechanism.

[0062] The cooling system 200 operates in a manner similar to the cooling system 100. The cooling system 200 thus shares the benefits of the cooling system 100. Thus, the performance of a device employing the cooling system 200 can be improved. As with the cooling system 100, the presence of the cavity 270 can further reduce the pressure that the actuator 220 resists during the upstroke of each cantilever 223. Thus, the power consumed can be reduced.

[0063] The use of the engineered actuator 220 can further improve the performance of the cooling system 200. The extension region 226 is thinner than the step region 224 and the outer region 228. This creates a cavity in the bottom of the actuator 220 that corresponds to the extension region 226. The presence of this cavity helps to improve the efficiency of the cooling system 200. In a manner similar to that described above with respect to the cooling system 100, the presence of the cavity 270 can further reduce the pressure that the actuator 220 resists during the upstroke of each cantilever 223. Thus, the power consumed can be reduced. Figures 1A-1FIn the manner discussed, the cantilever 223 oscillates toward the ceiling 210 in the upstroke and away from the ceiling 210 in the downstroke. The cantilever 223 can oscillate in phase or out of phase. When the cantilever 223 moves toward the ceiling 210, the higher pressure fluid in the top chamber 240 resists the movement of the cantilever 223. However, the presence of the cavity 270 mitigates the resistance to the upward movement of the cantilever 223. The suction in the bottom chamber 250 also resists the upward movement of the cantilever 223 during the upstroke. In the downstroke of the cantilever 223, the increased pressure in the bottom chamber 250 and the suction in the top chamber 240 resist the downward movement of the cantilever 223. However, the presence of the cavity in the cantilever 223 corresponding to the extended region 226 mitigates the suction in the bottom chamber 250 during the upstroke. The cavity formed by the extended region 226 also reduces the increase in pressure in the bottom chamber 250 during the downstroke. Similarly, the cavity 270 can reduce the suction from the top chamber 240. Because the magnitude of both the suction and the pressure that increase is reduced for both the upstroke and the downstroke, the cantilever 223 can move more easily through the fluid than the cantilever 123. This can be achieved while substantially maintaining a high enough pressure in the top chamber 240 to drive fluid flow through the cooling system 200. Thus, efficiency can be improved.

[0064] Furthermore, the presence of the outer region 228 can improve the ability of the cantilever 223 to move through the fluid being driven through the cooling system 200. The outer region 228 has a higher mass, and thus a higher momentum. Therefore, the outer region 228 can improve the ability of the cantilever 223 to move through the fluid being driven through the cooling system 200. The deflection magnitude of the cantilever 223 can also be increased. By using a thicker step region 224, these benefits can be achieved while maintaining the stiffness of the cantilever 223. Thus, the efficiency of the cooling system 200 can again be improved.

[0065] This improvement can also be understood as follows. Q can be thought of as a measure of the efficiency of the actuator 220. The Q value is determined at least in part by the interaction of the actuator 220 with the surrounding fluid (i.e., a gas such as air or a liquid), structural losses within the actuator 220, anchoring and / or other characteristics of the actuator 220. Q can be thought of as being determined by where is the deflection at resonance, and is the corresponding static deflection. The higher the Q value, the higher the deflection at resonance, and the slower the deflection decays (i.e., the lower the damping). Due to its engineered configuration, actuator 220 is better able to cut through the surrounding fluid. As a result, a higher static deflection can be achieved, the deflection can be amplified better at resonance, the power consumed to drive actuator 220 can be reduced, and the deflection can decay more slowly (i.e., be affected by reduced damping). The Q of actuator 220, and thus the efficiency of cooling system 200, can thus be improved through the configuration of actuator 220.

[0066] The use of engineered actuator 220 can also improve the reliability of cooling system 200. Due to its reduced thickness, extended region 226 can be less rigid than outer region 228 and step region 224. This reduction in rigidity reduces the stress on actuator 220 during vibration. Actuator 220 can be less likely to fail. As a result, the reliability of cooling system 200 can be improved.

[0067] Thus, using cooling system 100 and / or cooling system 200, not only can performance be improved compared to conventional cooling systems (not shown) having different configurations, but performance can be improved compared to cooling systems in which there is no cavity 170 / 270 and / or in which the actuator is not designed as actuator 220. This can be seen in Figure 3 , 4A and 4B.

[0068] Figure 3 is a plot 300 that depicts the back pressure versus flow rate for embodiments of an actively cooled system including a centrally anchored actuator. The back pressure is the pressure at which the flow rate through the cooling system becomes zero. Curve 310 indicates the back pressure versus flow rate for a cooling system similar to system 100, but having a uniform flow chamber (no cavity) and a uniform actuator (similar to actuator 120). Curve 320 indicates the back pressure versus flow rate for a cooling system similar to cooling system 200, but having a uniform flow chamber (no cavity 170 / 270) and an engineered actuator (similar to actuator 220). Curve 330 indicates the back pressure versus flow rate for a cooling system similar to cooling system 200, but having a cavity (e.g., cavity 270) and an engineered actuator (similar to actuator 220). As can be seen, the use of an engineered actuator 220 can improve the performance of a cooling system 200 compared to a cooling system having a uniform actuator (curve 320) and compared to a cooling system having a cavity (curve 330). Figure 3As indicated, the flow rate, particularly the maximum flow rate at zero back pressure, is substantially the same for curves 310, 320, and 330. However, the back pressure can be reduced without significantly affecting the flow rate. The difference between curves 310 and 320 indicates that the use of an engineered actuator, such as actuator 220, can reduce the back pressure with little or no impact on the flow rate. As indicated by the difference between curves 320 (no cavity, engineered actuator) and 330 (cavity, engineered actuator), the presence of cavity 170 and / or 270 can reduce the back pressure with little or no impact on the flow rate. Further, variations in the size of cavity 170 and / or 270 can be used to adjust the reduction in back pressure. For example, the area (e.g., length and width) of the cavity can be used to vary the reduction in back pressure. Thus, the back pressure, as well as the power used to operate cooling systems 100 and 200, can be reduced by the presence of cavity 170 and / or 270 and by the use of engineered actuator 220. In addition, the back pressure can be at least partially decoupled from the flow rate.

[0069] Figure 4A and Figure 4B are graphs 400A and 400B, respectively, depicting behavior of embodiments of actively cooled systems. Figure 4A depicts pressure in a top chamber (e.g., top chamber 140 and / or 240) of a flow chamber of relative time through a vibration cycle of an actuator (e.g., actuator 120 and / or 220). Figure 4B depicts pressure in a bottom chamber (e.g., bottom chamber 150 and / or 250) of a flow chamber of relative time through a vibration cycle of an actuator (e.g., actuator 120 and / or 220).

[0070] In Figure 4A , curve 410A indicates pressure in a top chamber of a cooling system similar to system 100 but having a uniform flow chamber (no cavity) and a uniform actuator (similar to actuator 120) relative to time. Curve 420A indicates pressure in a top chamber of a cooling system similar to cooling system 200 but having a uniform flow chamber (no cavity 170 / 270) and an engineered actuator (similar to actuator 220) relative to time. Curve 430A indicates pressure in a top chamber of a cooling system similar to cooling system 200 having a cavity (e.g., cavity 270) and an engineered actuator (similar to actuator 220) relative to time. Thus, one cycle (e.g., actuator 120 in Figure 1C and 1D the positions shown or in Figure 1E and 1Fbetween the positions shown). The use of an engineered actuator (e.g., actuator 220) having a cavity in the surface closest to the orifice plate does not significantly change the pressure in the top chamber against which the actuator works. Thus, curves 410A and 420A are very similar. However, the introduction of a cavity (e.g., cavity 170 and / or 270) mitigates the pressure changes in the top chamber (e.g., top chamber 140 and / or 240). This can be seen from the difference between curve 430A and curves 410A and 420A. Due to the presence of the cavity, the pressure against which the actuator is driven is reduced in magnitude. Thus, the actuator can be driven at lower power.

[0071] In Figure 4B , curve 410B indicates the pressure in the bottom chamber of a cooling system similar to system 100, but having a uniform flow chamber (no cavity) and a uniform actuator (similar to actuator 120) versus time. Curve 420B indicates the pressure in the bottom chamber of a cooling system similar to system 200, but having a uniform flow chamber (no cavity 170 / 270) and an engineered actuator (similar to actuator 220) versus time. Curve 430B indicates the pressure in the bottom chamber of a cooling system similar to system 200, but having a cavity (e.g., cavity 270) and an engineered actuator (similar to actuator 220) versus time. Thus, one cycle (e.g., actuator 120 is on Figure 1C and 1D between the positions shown or between Figure 1E and 1F between the positions shown). The use of an engineered actuator (e.g., actuator 220) having a cavity in the surface closest to the orifice plate significantly reduces the pressure in the bottom chamber (e.g., bottom chamber 150 and / or 250) against which the actuator works. Thus, a significant reduction in the magnitude of the pressure can be seen between curves 410B and 420B. However, the introduction of a cavity (e.g., cavity 170 and / or 270) does not significantly change the pressure in the bottom chamber. Thus, curve 430B is very similar to curve 420B. Due to the use of an engineered actuator having a cavity formed by an extended region, the pressure against which the actuator is driven is reduced in magnitude. Thus, the actuator can be driven at lower power.

[0072] As can be seen from Figure 3 , 4A and Figure 4BAs can be seen, fluid flow through the flow chambers 140 / 150 and / or 240 / 250 can be maintained while reducing the pressure within the chambers 140, 150, 240, and / or 250. Thus, a high fluid flow volume can be provided while reducing the operating power of the cooling systems 100 and / or 200. Thus, the performance of the cooling systems 100 and / or 200 can be improved not only relative to conventional cooling systems, but also relative to cooling systems that do not use cavities and / or engineered actuators.

[0073] Figure 5 An embodiment of an active cooling system 500 is depicted that includes an actuator and a cavity in an upper chamber. Figure 5 Not drawn to scale. Only portions of the cooling system 500 are shown for simplicity. The cooling system 500 is similar to the cooling systems 100 and / or 200. Thus, similar components have similar labels. For example, the cooling system 500 is used in conjunction with a heat-generating structure 502 that is similar to the heat-generating structure 102.

[0074] The cooling system 500 includes a top plate 510 having vents 512, an actuator 520, an aperture plate 530 including apertures 532, a top chamber 540 having a gap, a bottom chamber 550 having a gap, a flow chamber 540 / 550, an anchor (i.e., support structure) 560, and a cavity 570 that are respectively similar to the top plate 110 having vents 112, the actuator 220, the aperture plate 130 including apertures 132, the top chamber 140 having a gap 142, the bottom chamber 150 having a gap 152, the flow chamber 140 / 150, the anchor (i.e., support structure) 160, and the cavity 170. Thus, the actuator 520 is centrally supported by the anchor 560 such that at least a portion of the periphery of the actuator 520 is free to vibrate. Although not labeled in Figure 5 The anchor 560 extends along the axis of the actuator 520 such that the actuator 520 includes a cantilevered and a central anchoring region similar to the actuator 520, although not labeled in. In some embodiments, the actuator 520 can be designed in a manner similar to the actuator 220. Thus, the actuator 520 can include an anchoring region and a cantilevered arm that includes a step region, an extended region, and an outer region that are respectively similar to the anchoring region 222, the cantilevered arm 223, the step region 224, the extended region 226, and the outer region 228. In some embodiments, the cantilevered arm of the actuator 520 is driven in phase. In some embodiments, the cantilevered arm of the actuator 520 is driven out of phase. In other embodiments, the anchor 560 is only near the central portion of the actuator 520. The cooling system 500 operates in a manner similar to the cooling systems 100 and / or 200.

[0075] The flow chamber 540 / 550 includes a cavity 570. In the illustrated embodiment, the cavity 570 has been moved closer to the center of the actuator 520. Additionally, the depth of the cavity 570 varies with distance from the central axis of the actuator 520. Thus, in some embodiments, the cavity can not terminate at the outer wall of the flow chamber. In some embodiments, the cavity 570 can have a shape other than rectangular. Thus, the location, depth, shape, and / or other properties of the cavity 570 can vary. However, the cavity 570 can still be configured to mitigate pressure in the top chamber 540 in a manner similar to that described in the background of Figures 3-4B

[0076] The cooling system 500 thus shares the benefits of the cooling systems 100 and / or 200. Thus, the performance of a device employing the cooling system 500 can be improved. In a manner similar to the cooling systems 100 and / or 200, the cavity 570 can further reduce the pressure against which the actuator 520 works. Thus, power consumption can be reduced. Additionally, if an engineered actuator similar to the actuator 220 is used in place of the uniform actuator 520, the additional benefits of the cooling system 200 can be realized. Thus, performance, reliability, and power consumption can be improved.

[0077] Figures 6A-6B An embodiment of an active cooling system 600 is depicted that includes an actuator and a cavity in the upper chamber. Figure 6A is a side view of the cooling system 600, while Figure 6B is a plan view of the cooling system 600. Figures 6A-6B are not drawn to scale. For simplicity, only portions of the cooling system 600 are shown. The cooling system 600 is similar to the cooling systems 100, 200, and / or 500. Thus, similar components have similar labels. For example, the cooling system 600 is used in conjunction with a heat-generating structure 602 that is similar to the heat-generating structure 102.

[0078] The cooling system 600 includes a top plate 610 having vents 612, an actuator 620, an aperture plate 630 including apertures 632, a top chamber 640 having gaps, a bottom chamber 650 having gaps, a flow chamber 640 / 650, an anchor (i.e., support structure) 660, and cavities 670-1, 670-2, and 670-3 (collectively or generically cavities 670) that are respectively similar to the top plate 110 having vents 112, the actuator 220, the aperture plate 130 including apertures 132, the top chamber 140 having gaps 142, the bottom chamber 150 having gaps 152, the flow chamber 140 / 150, the anchor (i.e., support structure) 160, and the cavities 170. Thus, the actuator 620 is centrally supported by the anchor 660 such that at least a portion of the perimeter of the actuator 620 is free to vibrate. Although in the illustrated embodiment the actuator 620 is a uniform actuator, in some embodiments an engineered actuator similar to the actuator 220 can be used.​Figures 6A-6B The anchor 660 is not labeled, but extends along the axis of the actuator 620, such that the actuator 620 includes a cantilevered arm and a central anchoring region similar to the actuator 620. In some embodiments, the actuator 620 can be designed in a manner similar to the actuator 220. Thus, the actuator 620 can include an anchoring region and a cantilevered arm including a step region, an extension region, and an outer region similar to the anchoring region 222, the cantilevered arm 223, the step region 224, the extension region 226, and the outer region 228, respectively. In some embodiments, the cantilevered arm of the actuator 620 is driven in phase. In some embodiments, the cantilevered arm of the actuator 620 is driven out of phase. In other embodiments, the anchor 660 is only near the central portion of the actuator 620. The cooling system 600 operates in a manner similar to the cooling systems 100, 200, and / or 500.

[0079] The flow chamber 640 / 650 includes cavities 670. In the illustrated embodiment, cavities 670-1, 670-2, and 670-3, as well as the spaces 672 between cavities 670-1, 670-2, and 670-3 (only two of which are labeled) occupy approximately the same area of the top plate 610 as the cavity 170 occupies in the cooling system 100. However, the spaces 672 between cavities 670-1, 670-2, and 670-3 are thicker (e.g., not recessed or less recessed than the cavities 670-1, 670-2, and 670-3). The cavities 670 can still be configured to mitigate pressure in the top chamber 640 in a manner similar to that described in the context of the cavities 170. Figures 6A-6B Figures 3-4B In addition, the spaces 672 can mitigate the reduction in stiffness of the top plate 610 introduced by the cavities 670. Because the top plate 610 can be stiffer, vibrations due to motion of the actuator 620 can be reduced.

[0080] The cooling system 600 thus shares the benefits of the cooling systems 100, 200, and / or 500. Thus, the performance of a device employing the cooling system 600 can be improved. In a manner similar to the cooling systems 100, 200, and / or 500, the cavities 670 can further reduce the pressure against which the actuator 620 works. Thus, power consumption can be reduced. Furthermore, if an engineered actuator similar to the actuator 220 is used in place of the uniform actuator 520, the additional benefits of the cooling system 200 can be realized. Due to the increased stiffness of the top plate 610, vibrations can also be reduced. Thus, performance, reliability, and power consumption can be improved.

[0081] Figures 7A-7B An embodiment of an active cooling system 700 is depicted, including an actuator and cavities in an upper chamber. Figure 7A is a side view of the cooling system 700, while​Figure 7B is a plan view of cooling system 700. Figures 7A-7B is not drawn to scale. For simplicity, only a portion of cooling system 700 is shown. Cooling system 700 is similar to cooling systems 100, 200, 500, and / or 600. Accordingly, similar components have similar labels. For example, cooling system 700 is used in conjunction with a heat-generating structure 702, which is similar to heat-generating structure 102.

[0082] Cooling system 700 includes a top plate 710 having vents 712, an actuator 720, an aperture plate 730 including apertures 732, a top chamber 740 having a gap, a bottom chamber 750 having a gap, a flow chamber 740 / 750, an anchor (i.e., support structure) 760, and a cavity 770, which are respectively similar to top plate 110 having vents 112, actuator 220, aperture plate 130 including apertures 132, top chamber 140 having a gap 142, bottom chamber 150 having a gap 152, flow chamber 140 / 150, anchor (e.g., support structure) 160, and cavity 170. Accordingly, actuator 720 is centrally supported by anchor 760 such that at least a portion of the perimeter of actuator 720 is free to vibrate. Although not labeled in FIG. 7, anchor 760 extends along the axis of actuator 720 such that actuator 720 includes a cantilevered and a central anchoring region similar to actuator 720. In some embodiments, actuator 720 can be designed in a manner similar to actuator 220. Accordingly, actuator 720 can include an anchoring region and a cantilevered arm including a step region, an extension region, and an outer region, which are respectively similar to anchoring region 222, cantilevered arm 223, step region 224, extension region 226, and outer region 228. In some embodiments, the cantilevered arm of actuator 720 is driven in phase. In some embodiments, the cantilevered arm of actuator 720 is driven out of phase. In other embodiments, anchor 760 is only near the central portion of actuator 720. Cooling system 700 operates in a manner similar to cooling systems 100, 200, 500, and / or 600.

[0083] Flow chamber 740 / 750 includes cavity 770. In the illustrated embodiment, cavity 770 has been moved closer to the center of actuator 720. Accordingly, in some embodiments, cavity 770 can not terminate at the outer wall of the flow chamber. In some embodiments, cavity 770 can have a shape other than rectangular. Additionally, the sidewalls of cavity 770 are not perpendicular to the bottom surface of top plate 710. Accordingly, the location, depth, shape, and / or other properties of cavity 770 can vary. Cavity 770 can still be configured to mitigate pressure in top chamber 740 in a manner similar to that described in the background of Figures 3-4B

[0084] ​Cooling system 700 thus shares the benefits of cooling systems 100, 200, 500, and / or 600. Thus, the performance of a device employing cooling system 700 can be improved. In a manner similar to cooling systems 100, 200, 500, and / or 600, cavity 770 can further reduce the pressure against which actuator 720 works. Thus, power consumption can be reduced. Furthermore, if an engineered actuator similar to actuator 720 is used in place of uniform actuator 520, the additional benefits of cooling system 200 can be realized. Thus, performance, reliability, and power consumption can be improved.

[0085] Figure 8 An embodiment of an active cooling system 800 is depicted that includes an actuator and a cavity in an upper chamber. Figure 8 Not drawn to scale. For simplicity, only a portion of cooling system 800 is shown. Cooling system 800 is similar to cooling systems 100, 200, 500, 600, and / or 700. Thus, similar components have similar labels. For example, cooling system 800 is used in conjunction with a heat-generating structure 802 that is similar to heat-generating structure 102.

[0086] Cooling system 800 includes a top plate 810 with vents 812, an actuator 820, an aperture plate 830 including apertures 832, a top chamber 840 with a gap, a bottom chamber 850 with a gap, a flow chamber 840 / 850, an anchor (i.e., support structure) 860, and a cavity 870 that are respectively similar to top plate 110 with vents 112, actuator 220, aperture plate 130 including apertures 132, top chamber 140 with a gap 142, bottom chamber 150 with a gap 152, flow chamber 140 / 150, anchor (i.e., support structure) 160, and cavity 170. Thus, actuator 820 is centrally supported by anchor 860 such that at least a portion of the periphery of actuator 820 is free to vibrate. Although in the embodiment depicted in FIG. 8, actuator 820 is centrally supported by anchor 860, it is contemplated that actuator 820 can be supported in other manners. For example, actuator 820 can be supported by a plurality of anchors 860. Figure 8The anchor 860 is not labeled, but extends along the axis of the actuator 820, such that the actuator 820 includes a cantilever and a central anchoring region similar to the actuator 820. In the illustrated embodiment, the actuator 820 can be designed in a manner similar to the actuator 220. Thus, the actuator 820 includes an anchoring region 822, a cantilever 823, a step region 824, an extension region 826, and an outer region 828, which are similar to the anchoring region 222, the cantilever 223, the step region 224, the extension region 226, and the outer region 228, respectively. In some embodiments, the actuator 820 can be configured in another manner. For example, in some embodiments, the actuator 820 can be a simple actuator similar to the actuator 120. In some embodiments, the cantilever of the actuator 820 is driven in phase. In some embodiments, the cantilever of the actuator 820 is driven out of phase. In other embodiments, the anchor 860 is only near the central portion of the actuator 820. The cooling system 800 operates in a manner similar to the cooling systems 100, 200, 500, 600, and / or 700.

[0087] The actuator 820 also includes a recessed region 880 near the tip 821. The recessed region 880 functions in a manner similar to the cavity 870. Thus, the recessed region 880 can reduce the pressure that the actuator 820 must work against when the driving fluid is passed through the flow chamber 840 / 850. Thus, power consumption can be reduced.

[0088] The cooling system 800 shares the benefits of the cooling systems 100, 200, 500, 600, and / or 700. Thus, the performance of a device that employs the cooling system 800 can be improved. In a manner similar to the cooling systems 100, 200, 500, 600, and / or 700, the cavity 870 and the recessed region 880 can further reduce the pressure against which the actuator 820 works. Thus, power consumption can be reduced. Furthermore, because an engineered actuator 820 similar to the actuator 220 is used in place of a uniform actuator, the cooling system 800 can obtain the additional benefits of the cooling system 200.

[0089] Figure 9 An embodiment of an active cooling system 900 is depicted, including an actuator and a cavity in an upper chamber. Figure 9 Not drawn to scale. For simplicity, only a portion of the cooling system 900 is shown. The cooling system 900 is similar to the cooling systems 100, 200, 500, 600, 700, and / or 800. Thus, similar components have similar labels. For example, the cooling system 900 is used in conjunction with a heat-generating structure 902, which is similar to the heat-generating structure 102.

[0090] The cooling system 900 includes a top plate 910 with a vent 912, an actuator 920, an orifice plate 930 with holes 932, a top chamber 940 with gaps, a bottom chamber 950 with gaps, flow chambers 940 / 950, an anchor (i.e., support structure) 960, and a cavity 970, which are respectively similar to the top plate 110 with a vent 112, the actuator 220, the orifice plate 130 with holes 132, the top chamber 140 with gaps 142, the bottom chamber 150 with gaps 152, the flow chambers 140 / 150, the anchor (i.e., support structure) 160, and the cavity 170. Therefore, the actuator 920 is centrally supported by the anchor 960, allowing at least a portion of the periphery of the actuator 920 to vibrate freely. Although in Figure 9 While not explicitly labeled, anchor 960 extends along the axis of actuator 920, such that actuator 920 includes a cantilever and a central anchoring region similar to actuator 220. In the illustrated embodiment, actuator 920 may be designed in a manner similar to actuator 220. Therefore, actuator 920 includes an anchoring region 922, a cantilever 923, a stepped region 924, an extension region 926, and an outer region 928, which are respectively similar to anchoring region 222, cantilever 223, stepped region 224, extension region 226, and outer region 228. In some embodiments, actuator 920 may be configured in another manner. For example, in some embodiments, actuator 920 may be a simple actuator similar to actuator 120. In some embodiments, the cantilever of actuator 920 is driven in phase. In some embodiments, the cantilever of actuator 920 is driven out of phase. In other embodiments, anchor 960 is only located near the central portion of actuator 920. Cooling system 900 operates in a manner similar to cooling systems 100, 200, 500, 600, 700 and / or 800.

[0091] The orifice plate 930 includes a recessed region (or cavity) 980. Although shown with vertical sidewalls extending to the anchor 960, the recessed region 980 in the orifice plate 930 (and therefore in the bottom chamber 950) can be used to control the pressure in the flow chambers 940 / 950. When the drive fluid flows through the flow chambers 940 / 950, the recessed region 980 can reduce the pressure that the actuator 920 must withstand. Therefore, power consumption can be reduced. Furthermore, the recessed region 980 can be used to control the clearance between the orifice plate 930 and the actuator 920. Therefore, backflow of fluid through the orifice 932 into the bottom chamber 950 can be further reduced.

[0092] Cooling system 900 shares the benefits of cooling systems 100, 200, 500, 600, 700, and / or 800. Thus, the performance of a device employing cooling system 900 can be improved. In a manner similar to cooling systems 100, 200, 500, 600, 700, and / or 800, cavity 970 and recessed region 980 can further reduce the pressure against which actuator 920 works. The backflow or fluid through hole 932 can also be controlled. Thus, power consumption can be reduced. Moreover, because an engineered actuator 920 similar to actuator 220 is used in place of a uniform actuator, system 900 can obtain the additional benefits of cooling system 200.

[0093] Figures 10A-10B An embodiment of an active cooling system 1000 is depicted, which includes a top center anchored actuator. Figure 10A A side view of cooling system 1000 in a neutral position is depicted. Figure 10B A top view of cooling system 1000 is depicted. Figures 10A-10B Not drawn to scale. For simplicity, only a portion of cooling system 1000 is shown. Reference is made to Figures 10A-10B Cooling system 1000 is similar to cooling systems 100, 200, 500, 600, 700, 800, and / or 900. Thus, similar components have similar labels. For example, cooling system 1000 is used in conjunction with a heat generating structure 1002, which is similar to heat generating structure 102.

[0094] Cooling system 1000 includes a top plate 1010 having vents 1012, an actuator 1020, a hole plate 1030 including holes 1032, a top chamber 1040 having a gap, a bottom chamber 1050 having a gap, a flow chamber 1040 / 1050, an anchor (i.e., support structure) 1060, and a cavity 1070, which are similar to top plate 110 having vents 112, actuator 220, hole plate 130 including holes 132, top chamber 140 having a gap 142, bottom chamber 150 having a gap 152, flow chamber 140 / 150, anchor (i.e., support structure) 160, and cavity 170. Thus, actuator 1020 is centrally supported by anchor 1060, such that at least a portion of the perimeter of actuator 1020 is free to vibrate. In some embodiments, anchor 1060 extends along the axis of actuator 1020 (e.g., in a manner similar to anchors 360C and / or 360D). In other embodiments, anchor 1060 is only near the center portion of actuator 1020 (e.g., similar to anchors 1060C and / or 1060D). Although in the depicted embodiment, anchor 1060 is depicted as a single piece, in other embodiments, anchor 1060 can be formed of multiple pieces (e.g., similar to anchors 360A, 360B, 1060A, and / or 1060B). Figure 10A and 10BWhile not explicitly labeled, actuator 1020 includes an anchoring region and a cantilever, the cantilever comprising a stepped region, an extended region, and an outer region that are respectively similar to anchoring region 1022, cantilever 1023, stepped region 1024, extended region 1026, and outer region 1028. In some embodiments, the cantilever of actuator 1020 is driven in phase. In some embodiments, the cantilever of actuator 1020 is driven out of phase. In some embodiments, a simple actuator, such as actuator 120, may be used.

[0095] Anchor 1060 supports actuator 1020 from above. Therefore, actuator 1020 is suspended from anchor 1060. Anchor 1060 is suspended from top plate 1010. Top plate 1010 includes vent 1013. Vent 1012 on the side of anchor 1060 provides a path for fluid to flow into the side of chamber 1040.

[0096] As discussed above regarding cooling system 100, actuator 1020 can be driven to vibrate at or near its structural resonant frequency. Furthermore, the structural resonant frequency of actuator 1020 can be configured to align with the acoustic resonance of chambers 1040 / 1050. The structural and acoustic resonant frequencies are typically chosen within the ultrasonic range. For example, the vibrational motion of actuator 1020 can be at a frequency described relative to cooling system 100. This can thus improve efficiency and flow rate. However, other frequencies may also be used.

[0097] Cooling system 1000 operates in a manner similar to cooling systems 100, 200, 500, 600, 700, 800, and / or 900. Cooling system 1000 therefore shares the benefits of cooling systems 100, 200, 500, 600, 700, 800, and / or 900. Consequently, the performance of devices employing cooling system 1000 can be improved. Furthermore, suspending actuator 1020 from anchor 1060 can further enhance performance. Specifically, vibrations in cooling system 1000 that might affect other cooling units (not shown) can be reduced. For example, less vibration can be induced in top plate 1010 due to the movement of actuator 1020. Therefore, crosstalk between cooling system 1000 and other cooling systems (e.g., other units) or other parts of the device containing cooling system 1000 can be reduced. Thus, performance can be further improved.

[0098] Various cooling systems 100, 200, 500, 600, 700, 800, and 900 have been described, and specific features have been highlighted. Various characteristics of cooling systems 100, 200, 500, 600, 700, 800, 900, and / or 1000 can be combined in ways not explicitly described herein.

[0099] Figures 11A-11C An embodiment of an active cooling system 1100 is depicted, which includes a plurality of cooling units configured as a sheet of material or an array. Figure 11A A top view is depicted, while Figures 11B-11C A side view is depicted. Figures 11A-11C Not drawn to scale. The cooling system 1100 includes four cooling units 1101A, 1101B, 1101C, and 1101D (collectively or generically 1101), which are similar to one or more of the cooling systems described herein. More specifically, the cooling units 1101 are similar to the cooling systems 100, 200, 500, 600, 700, 800, 900, 1000, and / or some combination thereof. Although four cooling units 1101 are shown in a 2x2 configuration, in some embodiments another number and / or another configuration of cooling units 1101 can be employed. Multiple cooling unit arrays can also be utilized. In the depicted embodiment, the cooling units 1101 include a shared top plate 1110 with apertures 1112, actuators 1120, a shared aperture plate 1130 including holes 1132, a top chamber 1140, a bottom chamber 1150, a flow chamber 1140 / 1150, an anchor (support structure) 1160, and a cavity 1170, which are respectively similar to the top plate 110 with vents 112, the actuators 120, the aperture plate 130 with holes 132, the top chamber 140, the bottom chamber 150, the flow chamber 140 / 150, the anchor 160, and the cavity 170. In some embodiments, the cooling units 1101 can be similar to the cooling systems 200, 500, 600, 700, 800, 900, 1000, and / or some combination thereof. In some embodiments, the cooling units 1101 can be manufactured together and separated, for example by cutting through the top plate 1110 and the aperture plate 1130. The actuators 1120 are driven out of phase (i.e., in a manner similar to a seesaw). Moreover, as can be seen in Figures 11B-11C Figures 11B-11C ​In the depicted example, the actuators 1120 in the columns and rows are driven out of phase. Thus, the actuators 1120 in the cell 1101A are out of phase with the actuators 1120 in the cell 1101B. Similarly, the actuators 1120 in the cell 1101C are out of phase with the actuators 1120 in the cell 1101D. Thus, the actuators 1120 in the cells 1101A and 1101D are in phase. The actuators 1120 in the cells 1101B and 1101C are in phase. Other configurations are possible, particularly for larger arrays. For example, the actuators 1120 in the cells 1101A and 1101C can be in phase, the actuators 1120 in the cells 1101B and 1101D can be in phase, the actuators in the cells 1101A and 1101B can be out of phase, and the actuators 1120 in the cells 1101C and 1101D can be out of phase. By driving the actuators 1120 out of phase, vibrations in the cooling system 1100 can be reduced.

[0100] The cooling cells 1101 of the cooling system 1100 function in a manner similar to the cooling systems 100, 200, 500, 600, 700, 800, 900, 1000, and / or similar cooling systems. Thus, the cooling system 1100 can share the benefits described herein. Because the actuators in nearby cells are driven out of phase, vibrations in the cooling system 1100 can be reduced. Because multiple cooling cells 1101 are used, the cooling system 1100 can enjoy enhanced cooling capacity. Moreover, multiple individual cooling cells 1101 and / or cooling systems 1100 can be combined in various ways to obtain a desired cooling cell footprint.

[0101] Figure 12 is a flowchart depicting an example embodiment of a method 1200 for operating a cooling system. The method 1200 can include steps not depicted for simplicity. The method 1200 is described in the context of the piezoelectric cooling system 100. However, the method 1200 can be used for other cooling systems, including but not limited to the systems and cells described herein.

[0102] At 1202, one or more actuators in the cooling system are actuated to vibrate. At 1202, an electrical signal with a desired frequency is used to drive the actuators. In some embodiments, at 1202, the actuators are driven at or near their structural and / or acoustic resonant frequencies. The driving frequency can be 15 kHz or higher. If multiple actuators are driven at 1202, the cooling actuators can be driven out of phase. In some embodiments, the actuators are driven substantially 180 degrees out of phase. Furthermore, in some embodiments, individual actuators are driven out of phase. For example, different parts of the actuators can be driven to vibrate in opposite directions (i.e., similar to a seesaw). In some embodiments, individual actuators can be driven in phase (i.e., similar to a butterfly). Additionally, a driving signal can be provided to the anchor, the actuator, or both the anchor and the actuator. Furthermore, the anchor can be driven to bend and / or translate.

[0103] At 1204, feedback from the piezoelectric actuator is used to regulate the drive current. In some embodiments, the regulation is used to maintain the frequency at or near the acoustic and / or structural resonant frequency of the actuator and / or cooling system. The resonant frequency of a particular actuator may drift, for example, due to temperature variations. The regulation performed at 1204 allows for taking into account the drift in the resonant frequency.

[0104] For example, at 1202, the piezoelectric actuator 120 can be driven at its structural resonant frequency. This resonant frequency can also be at or near the acoustic resonant frequency of the top chamber 140. This can be achieved by driving the anchor 160 ( Figures 1A-1F This is achieved using a piezoelectric layer (not shown) in the actuator 120 and / or a piezoelectric layer in the actuator 120. At 1204, feedback is used to maintain the actuator 120 at resonance and, in some embodiments where multiple actuators are driven, to maintain a 180-degree out-of-phase state. Therefore, the efficiency of the actuator 120 driving fluid flow through the cooling system 100 and onto the heating structure 102 can be maintained. In some embodiments, 1204 includes sampling the current through the actuator 120 and / or the current through the anchor 160, and adjusting the current to maintain resonance and low input power.

[0105] Accordingly, actuators such as actuators 120, 220, 520, 620, 720, 820, 920, 1020, and / or 1120 can operate as described herein. The method 1200 thus provides for the use of piezoelectric cooling systems described herein. Moreover, due to the presence of cavities 170, 270, 570, 670, 770, 870, 880, 970, 980, 1070, and / or 1170, the power consumed by the cooling systems 100, 200, 500, 600, 700, 800, 900, 1000, and / or 1100 can be further reduced. Accordingly, the piezoelectric cooling systems can cool semiconductor devices more efficiently and quietly at lower power.

[0106] While the forgoing examples have been described in some detail for purposes of clarity of understanding, the application is not limited to the details provided. There are many alternative ways of implementing the application. The disclosed examples are illustrative and not restrictive.

Claims

1. A flow chamber, comprising: Including the upper chamber in the roof; An actuator positioned on the distal side of the top wall; and The lower chamber receives fluid from the upper chamber when the actuator is activated; The top wall includes at least one cavity that extends through only a portion of the thickness of the top wall, such that the fluid does not leave the chamber through the at least one cavity, and the at least one cavity is configured to mitigate the increase in pressure in the upper chamber caused by the vibratory motion of the actuator.

2. The flow chamber according to claim 1, further comprising: Support structure; Furthermore, the actuator includes a central region and a periphery, the actuator being supported by the support structure in the central region, at least a portion of the periphery being unfixed, and the actuator being configured to undergo vibratory motion when activated to drive fluid from the upper chamber to the lower chamber.

3. The flow chamber according to claim 2, wherein, The top wall includes at least one vent, and the actuator is located between the top wall and the lower chamber.

4. The flow chamber according to claim 3, wherein, The upper chamber has a length corresponding to an odd number multiplied by the wavelength divided by 4, where the wavelength is the acoustic wavelength of the frequency of the vibration, which corresponds to the structural resonance of the actuator and the acoustic resonance of the upper chamber having the wavelength.

5. The flow chamber according to claim 2, further comprising: An orifice plate having at least one hole therein, the orifice plate forming the bottom wall of the lower chamber, the actuator being activated to drive fluid through the at least one hole.

6. The flow chamber according to claim 5, wherein, At least one of the actuators has a recessed region therein, and the orifice plate has an additional cavity therein.

7. The flow chamber according to claim 2, wherein, The actuator includes an anchoring region and a cantilever. The anchoring region is fixed by the support structure. The cantilever extends outward from the anchoring region and includes a stepped region, at least one extended region, and an outer region. The stepped region extends outward from the anchoring region and has a stepped thickness. The at least one extended region extends outward from the stepped region and has at least one extended thickness less than the stepped thickness. The outer region extending outward from the extended region has an outer thickness greater than the extended thickness.

8. The flow chamber according to claim 2, wherein, The length of the at least one cavity is at least 0.25 times the length of the free portion of the actuator, and not greater than 2 / 3 times the length of the free portion of the actuator.

9. A cooling system, comprising: Multiple cooling units, each of which includes an upper chamber, a cooling element, and a lower chamber, the upper chamber including a top wall, the cooling element being located away from the top wall, and the lower chamber receiving fluid from the upper chamber when the cooling element is activated; The top wall includes at least one cavity that extends through only a portion of the thickness of the top wall, such that the fluid does not leave the chamber through the at least one cavity, and the at least one cavity is configured to mitigate the increase in pressure in the upper chamber caused by the vibratory movement of the cooling element.

10. The cooling system according to claim 9, wherein, Each of the plurality of cooling units further includes: A support structure; wherein the cooling element includes a central region and a periphery, the cooling element being supported by the support structure in the central region, at least a portion of the periphery being unfixed, and the cooling element being configured to undergo vibratory motion when activated to drive fluid from the upper chamber to the lower chamber.

11. The cooling system according to claim 10, wherein, The top wall includes at least one vent, and the cooling element is located between the top wall and the lower chamber.

12. The cooling system according to claim 11, wherein, The upper chamber has a length corresponding to an odd number multiplied by the wavelength divided by 4, where the wavelength is the acoustic wavelength of the vibrational motion frequency, which corresponds to the structural resonance of the cooling element and the acoustic resonance of the upper chamber having the wavelength.

13. The cooling system of claim 10, wherein each of the plurality of cooling units further comprises: An orifice plate having at least one hole therein, the orifice plate forming the bottom wall of the lower chamber, wherein the cooling element is activated to drive fluid through the at least one hole.

14. The cooling system according to claim 13, wherein, At least one of the cooling elements has a recessed region therein, and the perforated plate has an additional cavity therein.

15. The cooling system according to claim 10, wherein, The cooling element includes an anchoring region and a cantilever. The anchoring region is fixed by the support structure. The cantilever extends outward from the anchoring region and includes a stepped region, at least one extended region, and an outer region. The stepped region extends outward from the anchoring region and has a stepped thickness. The at least one extended region extends outward from the stepped region and has at least one extended thickness less than the stepped thickness. The outer region extending outward from the extended region has an outer thickness greater than the extended thickness.

16. The cooling system according to claim 10, wherein, The length of the cavity is at least 0.25 times the length of the free portion of the cooling element, and not greater than 2 / 3 times the length of the free portion of the cooling element.

17. A method for cooling a heat-generating structure, comprising: A cooling element is driven to induce vibrational motion at a certain frequency. The cooling element is configured to undergo vibrational motion when driven to guide fluid toward a chamber comprising an upper chamber, a lower chamber, and a cooling element. The upper chamber includes a top wall, the cooling element is positioned distal to the top wall, and the lower chamber receives fluid from the upper chamber when the cooling element is activated. The top wall includes at least one cavity that extends through only a portion of the thickness of the top wall, such that the fluid does not leave the chamber through the at least one cavity, and the at least one cavity is configured to mitigate the increase in pressure in the upper chamber caused by the vibratory movement of the cooling element.

18. The method according to claim 17, wherein, The cooling element includes a central region and a periphery, the cooling element is supported by a support structure in the central region, at least a portion of the periphery is not fixed, and the cooling element is configured to undergo vibratory motion when activated to drive fluid from the upper chamber to the lower chamber.

19. The method according to claim 18, wherein, The top wall includes at least one vent, and the cooling element is located between the top wall and the lower chamber.

20. The method according to claim 19, wherein, The at least one cavity is located near the periphery of the cooling element, and wherein the at least one cavity has a length that is at least 0.25 times the length of the free portion of the cooling element and not greater than 2 / 3 times the length of the free portion of the cooling element.

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