MEMS-based flow system in watertight devices

Abstract

A computing device includes a housing having a plurality of apertures therein, an active cooling system, and at least one of a plurality of membranes or a plurality of valves. Membranes and / or valves are coupled with the apertures. Each of the membranes is watertight and breathable. The valve is configured to prevent ingress of water through the aperture. An active cooling system is located in the housing. When activated, the active cooling system drives gas through the membrane, but does not drive water through the membrane.

Description

Cross-references to other applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 355,493, filed on June 24, 2022, entitled “MEMS-BASED FLOW SYSTEM USABLE IN WATERTIGHT DEVICES,” which is incorporated herein by reference for all purposes. Background Art

[0002] As computing devices increase in speed and computing power, the heat generated by computing devices is also increasing. 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 radiators can be used in smaller mobile computing devices such as smart phones, virtual reality devices, and tablet computers. However, such active and passive devices may not be able to adequately cool both mobile devices such as smart phones and larger devices such as laptop computers and desktop computers. In addition, incorporating cooling solutions into computing devices may be challenging. Therefore, it is desirable to have additional cooling solutions for computing devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Various embodiments of the invention are disclosed in the following detailed description and accompanying drawings.

[0004] Figures 1A-1G Embodiments of an active MEMS cooling system are depicted that include a centrally anchored cooling element.

[0005] Figure 2A-2B Embodiments of an active MEMS cooling system are depicted that include a centrally anchored cooling element.

[0006] Figures 3A-3E An embodiment of an active MEMS cooling system formed in a tile is depicted.

[0007] Figure 4 An embodiment of an active MEMS cooling system for use in a watertight device is depicted.

[0008] Figure 5 An embodiment of an active MEMS cooling system for use in a watertight device is depicted.

[0009] Fig. 6A -B depicts an embodiment of an active MEMS cooling system used in a watertight device and a heatmap of the device during use.

[0010] Figure 7is a graph indicating the performance of an active MEMS cooling system in a watertight device.

[0011] Figure 8 An embodiment of an active MEMS cooling system for use in a watertight device is depicted.

[0012] Fig. 9 Embodiments of methods for using actively cooled MEMS systems are described. DETAILED DESCRIPTION

[0013] The present invention may be implemented in a variety of ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer-readable storage medium; and / or a processor, such as a processor configured to execute instructions stored on and / or provided by a memory connected to the processor. In this specification, these embodiments or any other form that the present invention may take may be referred to as techniques. In general, the order of the steps of the disclosed processes may be changed within the scope of the present invention. Unless otherwise stated, a component such as a processor or memory described as being configured to perform a task may be implemented as a general-purpose component temporarily configured to perform the task at a given time, or manufactured as a dedicated component to perform the task. As used herein, the term "processor" refers to one or more devices, circuits, and / or processing cores configured to process data such as computer program instructions.

[0014] A detailed description of one or more embodiments of the present invention is provided below, as well as drawings illustrating the principles of the present invention. The present invention is described in conjunction with such embodiments, but the present invention is not limited to any embodiment. The scope of the present invention is limited only by the claims, and the present invention encompasses many alternatives, modifications and equivalents. Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. These details are provided for the purpose of example, and the present invention can be implemented according to the claims without some or all of these specific details. For the purpose of clarity, technical materials known in the technical field related to the present invention are not described in detail so that the present invention will not be unnecessarily obscure.

[0015] As semiconductor devices become more powerful, the heat generated during operation also increases. For example, processors for mobile devices such as smart phones, tablet computers, notebook computers, and virtual reality devices, as well as processors for other computing devices such as servers, can operate at high clock speeds, but can generate a lot of heat. Due to the amount of heat generated, the processor may only run at full speed for a relatively short period of time. After the expiration of this time, throttling (for example, a slowing down of the clock speed of the processor) occurs. Although throttling can reduce heat generation, it can also adversely affect the processor speed, and therefore affect the performance of the device using the processor. As technology develops toward 5G and beyond, this problem is expected to intensify. In addition, other components in the computing device may also generate heat. Therefore, for computing devices, thermal management is becoming more and more of a problem.

[0016] Larger computing devices such as laptops, desktop computers, or servers include active cooling systems. An active cooling system is a system in which an electrical signal is used to drive cooling. An electric fan with rotating blades is an example of an active cooling system, while a heat sink is an example of a passive cooling system. When powered on, the rotating blades of the fan drive air through the larger device to cool the internal components. However, space limitations and other limitations in computing devices limit the use of active cooling systems. For mobile and / or thinner devices such as smart phones and tablet computers or notebook computers, fans are typically too large. Fans may also have limited efficacy because there is an air boundary layer at the surface of the component, because the fan provides a limited air speed for the airflow through the hot surface that is expected to be cooled, and because the fan can generate excessive noise. The fan also has a limited back pressure. Space limitations and power limitations can further restrict the ability to provide electrical connections to the active cooling system. For example, if multiple active cooling systems are used, it may be necessary to fit the connections to the active cooling system in a small area. In addition, particularly for mobile devices, it may be desirable that the power consumed by such a cooling system is small. In addition, space limitations may adversely affect the ability to provide sufficient flow for cooling computing devices. It is increasingly expected that mobile devices such as smart phones are waterproof. It may be particularly difficult to incorporate active cooling devices into watertight packages without significantly reducing the cooling effect of the active cooling system. Therefore, when used in computing devices such as active computing devices, active cooling systems face special challenges. Passive cooling solutions may include components such as radiators and heat pipes or steam chambers to transfer heat to heat exchangers. However, passive cooling solutions may not provide enough heat to remove the excess heat generated. Therefore, additional cooling solutions are desired.

[0017] A computing device includes: a housing having an aperture therein, an active cooling system, and at least one of a membrane or a valve coupled to the aperture. Each of the membranes is watertight and air permeable. The valve is configured to prevent water from entering through the aperture. The active cooling system is in the housing. When activated, the active cooling system drives gas through the membrane but does not drive water through the membrane. In some embodiments, the computing device is a smart phone.

[0018] The computing device may include a water immersion sensor that determines whether the computing device is immersed in water. The active cooling system is deactivated in response to the determination that the computing device is immersed in water. In some such embodiments, the vent is closed in response to the determination that the computing device is immersed in water. The computing device may also include a splash guard for the plurality of apertures.

[0019] In some embodiments, the computing device includes a membrane. In such embodiments, the active cooling system, when activated, draws gas into the housing through an additional membrane in the plurality of membranes but does not draw water through the additional membrane, and drives the gas through the membrane to leave the housing. The housing may have a first side and a second side opposite the first side. The membrane is connected to a first pore on the first side, and the additional membrane is connected to a second pore on the second side. The active cooling system includes an egress, which may be adjacent to the membrane. In some embodiments, the active cooling system includes a spout, which has an egress. The spout is connected to the housing and terminates at or near the membrane (i.e., close to the membrane). In some embodiments, the active cooling system includes (one or more) cooling elements, and when the active cooling system is activated, the (one or more) cooling elements undergo a vibratory motion. The vibratory motion drives the gas. In addition, the active cooling system is thermally coupled to the heat generating structure of the computing device through a thermal conduction portion.

[0020] A method is described. The method is used to operate an active cooling system in a computing device such as a smart phone. The computing device includes: an active cooling system, a housing having pores therein, and at least one of a plurality of membranes or a plurality of valves coupled to the plurality of pores. Each of the membranes is watertight and air permeable. The valve is configured to prevent water from entering through the pores. The method includes: driving at least one cooling element of the active cooling system to undergo a vibratory motion. When activated, the vibratory motion of the cooling element(s) drives gas through a membrane of the plurality of membranes, but does not drive water through the membrane.

[0021] Figures 1A-1G1 is a diagram depicting an exemplary embodiment of an active MEMS cooling system 100 that can be used with a heat generating structure 102 and includes a centrally anchored cooling element 120 or 120'. Although referred to as a cooling system, the MEMS system 100 and similar systems described herein may be considered heat transfer systems and / or fluid transfer systems. The cooling element 120 is located at Figures 1A-1F and the cooling element 120' is shown in Figure 1G For clarity, only certain components are shown. Figures 1A-1G Not to scale. Figure 1A and 1B A cross-sectional view and a top view of the cooling system 100 in a neutral position are depicted. Figure 1C-1D The cooling system 100 is depicted during in-phase vibration motion activation. Figure 1E-1F The cooling system 100 is depicted during an out-of-phase vibration motion activation. Although shown as symmetrical, the cooling system 100 need not be symmetrical.

[0022] The cooling system 100 includes a top plate 110 having vents 112 therein, a cooling element 120, an orifice plate 130 having orifices 132 and cavities 134 therein, a support structure (or "anchor") 160, and chambers 140 and 150 (collectively, chambers 140 / 150) formed therein. The cooling element 120 is supported at its central region by the anchor 160. Although the cooling element 120 is not shown in FIG. 1 , the cooling element 120 is supported at its central region by the anchor 160. Figures 1A-1G Although referred to as a cooling element, the cooling element 120 and similar elements described herein may also be considered an actuator, a vibrating element, a vibrating member, an active member, and / or other terms that indicate that the element is configured to, when activated (or energized), undergo a vibratory motion and / or drive a fluid through a system. A region of the cooling element 120 that is closer to the periphery of the cooling element and includes a portion of the periphery of the cooling element (e.g., the tip 121) vibrates upon actuation. In some embodiments, the tip 121 of the cooling element 120 includes a portion of the periphery farthest from the anchor 160 and experiences the greatest deflection during actuation of the cooling element 120. For clarity, in Figure 1AOnly one tip 121 of the cooling element 120 is labeled. A base 190 is also shown, which connects the orifice plate 130 to the heat generating structure 102 and offsets the orifice plate 130 from the heat generating structure 102. In some embodiments, the base 190 also thermally couples the orifice plate 130 to the heat generating structure 102. In some embodiments, additional jet channel plates may be present and supported by the base 190. Therefore, the orifice plate 130 and / or such jet channel plates may be part of or all of the bottom plate supported by the base 190. Therefore, for the cooling system 100, multiple plates and / or plates with various structures may be used at the bottom plate.

[0023] Figure 1A The cooling system 100 is depicted in a neutral position. Thus, the cooling element 120 is shown as being substantially flat. For in-phase operation, the cooling element 120 is driven to Figure 1C and 1D 150. The oscillating motion draws fluid (e.g., air) into the vent 112 at a high velocity and / or high flow rate, through the chambers 140 and 150, and out of the orifice 132. For example, the velocity at which the fluid impinges on the heat generating structure 102 may be at least thirty meters per second. In some embodiments, the fluid is driven toward the heat generating structure 102 by the cooling element 120 at a velocity of at least forty-five meters per second. In some embodiments, the fluid is driven toward the heat generating structure 102 by the cooling element 120 at a velocity of at least sixty meters per second. In some embodiments, other velocities are possible. The cooling system 100 is also configured so that little or no fluid is drawn back into the chamber 140 / 150 through the orifice 132 by the oscillating motion of the cooling element 120.

[0024] It is desirable that the heat generating structure 102 is cooled by the cooling system 100. In some embodiments, the heat generating structure 102 generates heat. For example, the heat generating structure may be an integrated circuit. In some embodiments, it is desirable that the heat generating structure 102 is cooled but does not itself generate heat. The heat generating structure 102 may conduct heat (e.g., from a nearby object that generates heat). For example, the heat generating structure 102 may be a heat sink or a vapor chamber. Thus, the heat generating structure 102 may include: (one or more) semiconductor components, the (one or more) semiconductor components including individual integrated circuit components such as processors, (one or more) other integrated circuits and / or (one or more) chip packages; (one or more) sensors; (one or more) optical devices; one or more batteries; (one or more) other components of an electronic device such as a computing device; a heat sink; a heat pipe; (one or more) other electronic components and / or (one or more) other devices that are desired to be cooled. In some embodiments, the heat generating structure 102 may be a thermally conductive portion of a module that includes the cooling system 100. For example, cooling system 100 may be attached to heat generating structure 102, which may be coupled to another heat sink, a vapor chamber, an integrated circuit, or other separate structure that is desired to be cooled.

[0025] The device in which the cooling system 100 is desired to be used may also have limited space in which the cooling system is placed. For example, the cooling system 100 may be used in a computing device. Such computing devices may include, but are not limited to, smartphones, tablet computers, laptop computers, tablet computers, two-in-one laptop computers, 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 that is capable of residing in a mobile computing device and / or other device with limited space in at least one dimension. For example, the total height h3 of the cooling system 100 (from the top of the heat generating 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 greater than 1.5 mm. In some embodiments, the total height is no greater than 1.1 mm. In some embodiments, the total height is no more than one millimeter. In some embodiments, the total height is no more than two hundred and fifty microns. Similarly, the distance y between the bottom of the orifice plate 130 and the top of the heat generating structure 102 may be small. In some embodiments, y is at least two hundred microns and no more than 1.2 millimeters. For example, y may be at least two hundred and fifty microns and no more than three hundred microns. In some embodiments, y is at least five hundred microns and no more than one millimeter. In some embodiments, y is at least two hundred microns and no more than three hundred microns. Therefore, the cooling system 100 can be used in a computing device and / or other device with limited space in at least one dimension. However, it is not prevented from using the cooling system 100 in a device with less space restrictions and / or for purposes other than cooling. Although one cooling system 100 (e.g., one cooling unit) is shown, multiple cooling systems 100 can be used in combination with the heat generating structure 102. For example, a one-dimensional or two-dimensional array of cooling units can be utilized.

[0026] The cooling system 100 is in communication with a fluid that is used to cool the heat generating structure 102. The fluid may be a gas or a liquid. For example, the fluid may be air. In some embodiments, the fluid includes fluid from outside the device in which the cooling system 100 resides (e.g., provided through an external vent in the device). In some embodiments, the fluid circulates within the device in which the cooling system 100 resides (e.g., in a closed device).

[0027] The cooling element 120 can be considered to divide the interior of the active MEMS cooling system 100 into a top chamber 140 and a bottom chamber 150. The top chamber 140 is formed by the cooling element 120, the side portions, and the top plate 110. The bottom chamber 150 is formed by the orifice plate 130, the side portions, the cooling element 120, and the anchor 160. The top chamber 140 and the bottom chamber 150 are connected at the periphery of the cooling element 120 and together form the chamber 140 / 150 (e.g., the interior chamber of the cooling system 100).

[0028] The size and configuration of the top chamber 140 can be a function of the size of the unit (cooling system 100), the frequency of movement and operation of the cooling element 120. The top chamber 140 has a height h1. The height of the top chamber 140 can be selected to provide sufficient pressure to drive the 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 high enough so that the cooling element 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 top chamber 140 has a height of at least two hundred and no more than three hundred microns.

[0029] 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 cooling element 120. Therefore, during normal operation, no part of the cooling element 120 contacts the orifice plate 130. The bottom chamber 150 is substantially smaller than the top chamber 140 and can help reduce the backflow of fluid into the orifice 132. In some embodiments, the height of the bottom chamber 150 is the maximum deflection of the cooling element 120 plus at least five microns and no more than ten microns. In some embodiments, the deflection z of the cooling element 120 (e.g., the deflection of the tip 121) has an amplitude of at least ten microns and no more than one hundred microns. In some such embodiments, the amplitude of the deflection of the cooling element 120 is at least ten microns and no more than sixty microns. However, the amplitude of the deflection of the cooling element 120 depends on factors such as the desired flow rate through the cooling system 100 and the configuration of the cooling system 100. Therefore, the height of the bottom chamber 150 depends substantially on the flow rate through the cooling system 100 and other components of the cooling system 100.

[0030] The top plate 110 includes a vent 112 through which fluid can be drawn into the cooling system 100. The top vent 112 may have a size selected based on the desired sound pressure in the chamber 140. For example, in some embodiments, the width w of the vent 112 is at least five hundred microns and no more than one thousand microns. In some embodiments, the width of the vent 112 is at least two hundred and fifty microns and no more than two thousand microns. In the illustrated embodiment, the vent 112 is a centrally located aperture 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 footprint of a circular, rectangular or other shape. Although a single vent 112 is shown, multiple vents may be used. For example, the vent may be offset toward the edge of the top chamber 140, or located on the side (one or more) of the top chamber 140. Although top plate 110 is shown as being substantially flat, in some embodiments, grooves and / or other structures may be provided in top plate 110 to modify the configuration of top chamber 140 and / or the region above top plate 110 .

[0031] The anchor (support structure) 160 supports the cooling element 120 at the central portion of the cooling element 120. Thus, at least a portion of the periphery of the cooling element 120 is unpinned and free to vibrate. In some embodiments, the anchor 160 is disposed along the central axis of the cooling element 120 (e.g., perpendicular to the Figures 1A-1F 121). In such embodiments, the portion of the cooling element 120 that vibrates (e.g., including the tip 121) moves in a cantilevered manner. Thus, the portion of the cooling element 120 that vibrates in a cantilevered manner may move in a manner similar to the wings of a butterfly (i.e., in phase) and / or in a manner similar to a seesaw (i.e., out of phase). Thus, in some embodiments, the portion of the cooling element 120 that vibrates in a cantilevered manner vibrates in phase, and in other embodiments vibrates out of phase. In some embodiments, the anchor 160 does not extend along the axis of the cooling element 120. In such embodiments, all portions of the periphery of the cooling element 120 are free to vibrate (e.g., similar to a jellyfish). In the illustrated embodiment, the anchor 160 supports the cooling element 120 from the bottom of the cooling element 120. In other embodiments, the anchor 160 may support the cooling element 120 in another manner. For example, the anchor 160 may support the cooling element 120 from the top (e.g., the cooling element 120 is suspended from the anchor 160). In some embodiments, the width a of the anchor 160 is at least 0.5 mm and not greater than 4 mm. In some embodiments, the width of the anchor 160 is at least two millimeters and no greater than 2.5 millimeters. The anchor 160 may occupy at least ten percent and no greater than fifty percent of the cooling element 120.

[0032] The cooling element 120 has a first side away from the heat generating structure 102 and a second side close to the heat generating structure 102. Figures 1A-1F In the embodiment shown in , the first side of the cooling element 120 is the top of the cooling element 120 (closer to the top plate 110), and the second side is the bottom of the cooling element 120 (closer to the orifice plate 130). Figures 1A-1F As shown in , the cooling element 120 is actuated to undergo a vibratory motion. The vibratory motion of the cooling element 120 drives the fluid from a first side of the cooling element 120 away from the heat generating structure 102 (e.g., from the top chamber 140) to a second side of the cooling element 120 near the heat generating structure 102 (e.g., to the bottom chamber 150). The vibratory motion of the cooling element 120 also draws the fluid through the vent 112 and into the top chamber 140; forces the fluid from the top chamber 140 to the bottom chamber 150; and drives the fluid from the bottom chamber 150 through the orifice 132 of the orifice plate 130. Therefore, the cooling element 120 can be considered an actuator. Although described in the context of a single continuous cooling element, in some embodiments, the cooling element 120 can be formed by two (or more) cooling elements. Each of the cooling elements is depicted as a pinned portion (e.g., supported by the support structure 160) and an unpinned opposite portion. Thus, a single centrally supported cooling element 120 may be formed from a combination of multiple cooling elements supported at the edges.

[0033] The cooling element 120 has a length L that depends on the frequency at which the cooling element 120 is desired to vibrate. In some embodiments, the length of the cooling element 120 is at least four millimeters and no greater than ten millimeters. In some such embodiments, the cooling element 120 has a length of at least six millimeters and no greater than eight millimeters. The depth (e.g., perpendicular to the Figures 1A-1F ) can vary from one quarter of L to two times of L. For example, the cooling element 120 can have a depth that is the same as the length. The thickness t of the cooling element 120 can vary based on the configuration of the cooling element 120 and / or the frequency at which the cooling element 120 is expected to be actuated. In some embodiments, for a cooling element 120 having a length of eight millimeters and driven at a frequency of at least twenty kilohertz and not more than twenty-five kilohertz, the cooling element thickness is at least two hundred microns and not more than three hundred and fifty microns. The length C of the chamber 140 / 150 is close to the length L of the cooling element 120. For example, in some embodiments, the distance d between the edge of the cooling element 120 and the wall of the chamber 140 / 150 is at least one hundred microns and not more than five hundred microns. In some embodiments, d is at least two hundred microns and not more than three hundred microns.

[0034] The cooling element 120 may be driven at or near a frequency that is both a resonant frequency for acoustic resonance of pressure waves of the fluid in the top chamber 140 and a resonant frequency for structural resonance of the cooling element 120. The portion of the cooling element 120 that undergoes vibratory motion is driven at or near the resonance of the cooling element 120 ("structural resonance"). In some embodiments, the portion of the cooling element 120 that undergoes vibration may be a cantilever section. The frequency of vibration for structural resonance is referred to as the structural resonance frequency. Using the structural resonance frequency in driving the cooling element 120 reduces the power consumption of the cooling system 100. The cooling element 120 and the top chamber 140 may also be configured such that the structural resonance frequency corresponds to a resonance in a pressure wave in the fluid driven through the top chamber 140 (acoustic resonance of the top chamber 140). The frequency of such a pressure wave is referred to as an acoustic resonance frequency. At 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 cooling element 120, and near the connection between the top chamber 140 and the bottom chamber 150). The distance between these two regions is C / 2. Therefore, C / 2=nλ / 4, where λ 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, C=λ / 2. Since the length of the chamber 140 (e.g., C) is close to the length of the cooling element 120, in some embodiments, L / 2=nλ / 4 is also approximately correct, where λ is the acoustic wavelength for the fluid, and n is an odd number. Therefore, the frequency v at which the cooling element 120 is driven is at or near the structural resonant frequency for the cooling element 120. The frequency v is also at or near the acoustic resonant frequency for at least the top chamber 140. The acoustic resonant frequency of the top chamber 140 generally varies less drastically with parameters such as temperature and size than the structural resonant frequency of the cooling element 120. Therefore, in some embodiments, the cooling element 120 may be driven at (or closer to) the structural resonant frequency rather than the acoustic resonant frequency.

[0035] The orifice plate 130 has an orifice 132 and a cavity 134 therein. Although a specific number and distribution of orifices 132 are shown, another number and / or another distribution may be used. The cavity 134 may be configured differently or may be omitted. A single orifice plate 130 is used for a single cooling system 100. In other embodiments, a plurality of cooling systems 100 may share an orifice plate. For example, a plurality of units 100 may be provided together in a desired configuration. In such embodiments, the units 100 may be of the same size and configuration, or of different (one or more) sizes and / or (one or more) configurations. The orifice 132 is shown as having an axis oriented perpendicular to the surface of the heat generating structure 102. In other embodiments, the axis of one or more orifices 132 may be at another angle. For example, the angle of the axis may be selected from a substantially zero degree and a non-zero acute angle. The orifice 132 also has a sidewall that is substantially parallel to the normal to the surface of the orifice plate 130. In some embodiments, the orifice may have sidewalls that are at a non-zero angle to the normal to the surface of the orifice plate 130. For example, the orifice 132 may be conical. In addition, although the orifice location 130 is shown as being substantially flat, in some embodiments, grooves and / or other structures may be provided in the orifice plate 130 to modify the configuration of the bottom chamber 150 and / or the region between the orifice plate 130 and the heat generating structure 102.

[0036] The size, distribution, and location of the orifices 132 are selected to control the flow rate of the fluid driven to the surface of the heat generating structure 102. The location and configuration of the orifices 132 can be configured to increase / maximize the flow of fluid from the bottom chamber 150 through the orifices 132 to the injection 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 orifices 132 can also be selected to reduce / minimize the suction flow (e.g., backflow) from the injection channel through the orifices 132. For example, it is desirable that the location of the orifices is far enough from the tip 121 to reduce the suction force that pulls the fluid through the orifices 132 into the bottom chamber 150 during the upward stroke of the cooling element 120 (the tip 121 moves away from the orifice plate 130). It is also desirable that the location of the orifices is close enough to the tip 121 so that the suction force in the upward stroke of the cooling element 120 also allows the higher pressure from the top chamber 140 to push the 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 to the flow rate from the jet channel through the orifice 132 in the upward stroke (the "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. In order to provide the desired pressure, flow rate, suction, and net flow ratio, it is desirable that the orifice 132 is at least r1 away from the tip 121 and no more than r2 away from the tip 121 of the cooling element 120. In some embodiments, r1 is at least one hundred microns (e.g., r1 ≥ 100 μm) and r2 is no more than one millimeter (e.g., r2 ≤ 1000 μm). In some embodiments, the orifice 132 is at least two hundred microns away from the tip 121 of the cooling element 120 (e.g., r1 ≥ 200 μm). In some such embodiments, the orifice 132 is at least three hundred microns away from the tip 121 of the cooling element 120 (e.g., r1 ≥ 300 μm). In some embodiments, the orifice 132 has a width o of at least one hundred microns and no more than five hundred microns. In some embodiments, the orifice 132 has a width o of at least two hundred microns and no more than three hundred microns. In some embodiments, the orifice spacing s is at least one hundred microns and no more than one millimeter. In some such embodiments, the orifice spacing is at least four hundred microns and no more than six hundred microns. In some embodiments, it is also desirable that the orifice 132 occupies a specific portion of the area of ​​the orifice plate 130. For example, the orifice 132 may cover at least five percent and no more than fifteen percent of the footprint of the orifice plate 130 to achieve the desired flow rate of the fluid passing through the orifice 132. In some embodiments, the orifice 132 covers at least eight percent and no more than twelve percent of the footprint of the orifice plate 130.

[0037] In some embodiments, a piezoelectric is used to actuate the cooling element 120. Thus, the cooling element 120 may be a piezoelectric cooling element. The cooling element 120 may be driven by a piezoelectric mounted on or integrated into the cooling element 120. In some embodiments, the cooling element 120 is driven in another manner including, but not limited to, providing a piezoelectric on another structure in the cooling system 100. The cooling element 120 and similar cooling elements are hereinafter referred to as piezoelectric cooling elements, but it is possible that mechanisms other than piezoelectrics may be used to drive the cooling elements. In some embodiments, the cooling element 120 includes a piezoelectric layer on a substrate. The substrate may include stainless steel, Ni alloy, Hastelloy, Al (e.g., Al alloy) and / or Ti (e.g., Ti alloy, such as Ti 6 Al-4V), or are composed of them. In some embodiments, the piezoelectric layer includes multiple sublayers formed as a thin film on a substrate. In other embodiments, the piezoelectric layer may be a main layer attached to the substrate. Such piezoelectric cooling element 120 also includes electrodes for activating the piezoelectric body. In some embodiments, the substrate is used as an electrode. In other embodiments, a bottom electrode may be provided between the substrate and the piezoelectric layer. Other layers may be included in the piezoelectric cooling element, including but not limited to a seed layer, a capping layer, a passivation layer or other layers. Therefore, a piezoelectric body can be used to actuate the cooling element 120.

[0038] In some embodiments, the cooling system 100 includes an air duct (not shown) or other conduits. Such conduits provide a path for the heated fluid to flow away from the heat generation structure 102. In some embodiments, the conduit returns the fluid to a side of the top plate 110 away from the heat generation structure 102. In some embodiments, the conduit may instead direct the fluid away from the heat generation structure 102 in a direction parallel to the heat generation structure 102 or perpendicular to the heat generation structure 102 but in an opposite direction (e.g., toward the bottom of the page). For devices in which fluids outside the device are used in the cooling system 100, the conduit may direct the heated fluid to the vent. In such embodiments, additional fluid may be provided from the inlet vent. In embodiments in which the device is closed, the conduit may provide a circuitous path back to a zone near the vent 112 and away from the heat generation structure 102. Such paths allow the fluid to dissipate heat before being reused to cool the heat generation structure 102. In other embodiments, the conduit may be omitted or constructed in another way. Therefore, the fluid is allowed to take away heat from the heat generation structure 102.

[0039] exist Figures 1A-1F Although described in the context of specific pressures, gap sizes, and flow times, the operation of the cooling system 100 is not dependent upon the explanations herein. Figure 1C-1DThe in-phase operation of the cooling system 100 is depicted. Figure 1C , the cooling element 120 has been actuated so that its tip 121 moves away from the top plate 110. Therefore, Figure 1C 14B. 14B may be considered to depict the end of the downward stroke of the cooling element 120. Due to the vibratory motion of the cooling element 120, the gap 152 with respect to the bottom chamber 150 has decreased in size and is shown as gap 152B. Conversely, the gap 142 with respect to the top chamber 140 has increased in size and is shown as gap 142B. During the downward stroke, when the cooling element 120 is in the neutral position, a lower (e.g., minimum) pressure is established at the periphery. As the downward stroke continues, as shown in FIG. Figure 1C As shown in , the bottom chamber 150 decreases in size and the top chamber 140 increases in size. Therefore, the fluid is driven away from the orifice 132 in a direction that is perpendicular or nearly perpendicular 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 orifice 132 toward the heat generating structure 102 at a high speed (e.g., in excess of thirty-five meters per second). 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 orifice 132. Also, on the downward stroke, the top chamber 140 increases in size, and a lower pressure exists in the top chamber 140. As a result, the fluid is drawn into the top chamber 140 through the vent 112. The movement of the fluid into the vent 112, through the orifice 132, and along the surface of the heat generating structure 102 is Figure 1C Indicated by unlabeled arrows.

[0040] The cooling element 120 is also actuated so that the tip 121 moves away from the heat generating structure 102 and toward the top plate 110. Figure 1D 14C. Gap 152 has increased in size and is shown as gap 152C. During the upstroke, when cooling element 120 is in the neutral position, a higher (e.g., maximum) pressure is formed at the periphery. As the upstroke continues, as shown in FIG. Figure 1D As shown in FIG. 1 , the bottom chamber 150 increases in size and the top chamber 140 decreases in size. Thus, fluid is driven from the top chamber 140 (e.g., the periphery of the chamber 140 / 150) to the bottom chamber 150. Thus, as the tip 121 of the cooling element 120 moves upward, the top chamber 140 acts as a nozzle for the incoming fluid to be accelerated and driven toward the bottom chamber 150. The movement of the fluid into the bottom chamber 150 is Figure 1D100. The positions and configurations of the cooling element 120 and the orifice 132 are selected to reduce suction forces and, therefore, reduce fluid backflow from the jet channel (between the heat generating structure 102 and the orifice plate 130) into the orifice 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 excessive backflow of heated fluid from the jet channel into the bottom chamber 150. Furthermore, the cooling system 100 is operable such that fluid is drawn in through the vent 112 and expelled through the orifice 132 without the cooling element 120 contacting the top plate 110 or the orifice plate 130. Thus, pressures are formed within the chambers 140 and 150 that effectively open and close the vent 112 and the orifice 132 so that fluid is driven through the cooling system 100 as described herein.

[0041] repeat Figure 1C and 1D Thus, the cooling element 120 undergoes Figures 1A-1D , drawing fluid from the distal side of the top plate 110 through the vent 112 into the top chamber 140; transferring fluid from the top chamber 140 to the bottom chamber 150; and pushing the fluid through the orifice 132 and toward the heat generating structure 102. As discussed above, the cooling element 120 is driven to vibrate at or near the structural resonant frequency of the cooling element 120. In addition, the structural resonant frequency of the cooling element 120 is configured to align with the acoustic resonance of the chamber 140 / 150. The structural resonant frequency and the acoustic resonant frequency are generally selected to be within the ultrasonic range. For example, the vibratory motion of the cooling element 120 may be at a frequency from 15kHz to 30kHz. In some embodiments, the cooling element 120 vibrates at one / more frequencies of at least 20kHz and not greater than 30kHz. The structural resonant frequency of the cooling element 120 is within ten percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the cooling element 120 is within five percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the cooling element 120 is within three percent of the acoustic resonant frequency of the cooling system 100. Thus, efficiency and flow rates may be improved. However, other frequencies may be used.

[0042] The fluid driven toward the heat generating structure 102 may move substantially orthogonally (perpendicularly) to the top surface of the heat generating structure 102. In some embodiments, the fluid motion may have a non-zero acute angle relative to the normal of the top surface of the heat generating structure 102. In either case, the fluid may be thinned and / or form pores in the fluid boundary layer at the heat generating structure 102. As a result, heat transfer from the heat generating structure 102 may be improved. The fluid deflects away from the heat generating structure 102 and travels 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. Therefore, heat from the heat generating structure 102 may be extracted by the fluid. The fluid may leave the area between the orifice plate 130 and the heat generating structure 102 at the edge of the cooling system 100. Airways or other conduits (not shown) at the edge of the cooling system 100 allow the fluid to be taken away from the heat generating structure 102. In other embodiments, the heated fluid may be further transferred from the heat generating structure 102 in another way. The fluid can exchange heat transferred from the heat generating structure 102 to another structure or to the surrounding environment. Therefore, the fluid at the distal side of the top plate 110 can remain relatively cool, allowing additional heat extraction. In some embodiments, the fluid is circulated so that it returns 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 cooling element 120. As a result, the heat generating structure 102 can be cooled.

[0043] Figure 1E-1F An embodiment of an active MEMS cooling system 100 including a centrally anchored cooling element 120 is depicted, wherein the cooling element is driven out of phase. More specifically, segments of the cooling element 120 on opposite sides of the anchor 160 (and therefore on opposite sides of the central region of the cooling element 120 supported by the anchor 160) are driven to vibrate out of phase. In some embodiments, the segments of the cooling element 120 on opposite sides of the anchor 160 are driven at or nearly one hundred and eighty degrees out of phase. Thus, one segment of the cooling element 120 vibrates toward the top plate 110, while another segment of the cooling element 120 vibrates toward the orifice plate 130 / heat generating structure 102. The movement of the segments of the cooling element 120 toward the top plate 110 (upward travel) drives the fluid in the top chamber 140 to the bottom chamber 150 on that side of the anchor 160. The movement of the segments of the cooling element 120 toward the orifice plate 130 drives the fluid through the orifices 132 and toward the heat generating structure 102. Thus, the fluid traveling at a high velocity (e.g., a velocity described relative to in-phase operation) is alternately driven away from the orifices 132 on opposite sides of the anchor 160. Because the fluid is driven through the orifices 132 at a high velocity, the cooling system 100 can be viewed as a MEMS ejector. The movement of the fluid at Figure 1E and 1FIndicated by unlabeled arrows. Figure 1E and 1F The movement between the positions shown in is repeated. Thus, the cooling element 120 undergoes Figure 1A , 1E and 1F, thereby alternately drawing fluid from the distal side of the top plate 110 through the vents 112 into the top chamber 140 on each side of the cooling element 120; transferring fluid from each side of the top chamber 140 to the corresponding side of the bottom chamber 150; and pushing the fluid through the orifices 132 on each side of the anchor 160 and toward the heat generating structure 102. As discussed above, the cooling element 120 is driven to vibrate at or near the structural resonant frequency of the cooling element 120. In addition, the structural resonant frequency of the cooling element 120 is configured to align with the acoustic resonance of the chambers 140 / 150. The structural resonant frequency and the acoustic resonant frequency are generally selected to be within the ultrasonic range. For example, the vibratory motion of the cooling element 120 may be at a frequency described for in-phase vibration. The structural resonant frequency of the cooling element 120 is within ten percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the cooling element 120 is within five percent of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the cooling element 120 is within three percent of the acoustic resonant frequency of the cooling system 100. Thus, efficiency and flow rates may be improved. However, other frequencies may be used.

[0044] The fluid driven toward the heat generating structure 102 for out-of-phase vibration can move substantially orthogonal (perpendicular) to the top surface of the heat generating structure 102 in a manner similar to that described above for in-phase operation. Similarly, airways or other conduits (not shown) at the edge of the cooling system 100 allow the fluid to be taken 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 way. The fluid can exchange heat transferred from the heat generating structure 102 to another structure or to the surrounding environment. Therefore, the fluid at the far side of the top plate 110 can remain relatively cold, thereby allowing additional heat extraction. In some embodiments, the fluid is circulated so as to return to the far side of the top plate 110 after cooling. In other embodiments, the heated fluid is taken away and replaced by new fluid at the far side of the cooling element 120. As a result, the heat generating structure 102 can be cooled.

[0045] Despite Figures 1A-1F Although shown in the context of a uniform cooling element, cooling system 100 may utilize cooling elements having different shapes. Figure 1GAn embodiment of a designed cooling element 120' is depicted that has a customized geometry and can be used in a cooling system such as cooling system 100. Cooling element 120' includes an anchoring region 122 and cantilevers 123. Anchoring region 122 is supported (e.g., held in place) by anchors 160 in cooling system 100. Cantilevers 123 undergo vibratory motion in response to cooling element 120' being actuated. Each cantilever 123 includes a step region 124, an extension region 126, and an outer region 128. In FIG. Figure 1G In the embodiment shown in , the anchoring region 122 is located in the center. The step region 124 extends outwardly from the anchoring region 122. The extension region 126 extends outwardly from the step region 124. The outer region 128 extends outwardly from the extension region 126. In other embodiments, the anchoring region 122 can be at one edge of the actuator, and the outer region 128 can be at the opposite edge. In such embodiments, the actuator is edge anchored.

[0046] The extension region 126 has a thickness (extended thickness) that is less than the thickness of the step region 124 (step thickness) and less than the thickness of the outer region 128 (outer thickness). Therefore, the extension region 126 can be regarded as concave. The extension region 126 can also be regarded as providing a larger bottom chamber 150. In some embodiments, the outer thickness of the outer region 128 is the same as the step thickness of the step region 124. In some embodiments, the outer thickness of the outer region 128 is different from the step thickness of the step region 124. In some embodiments, the outer region 128 and the step region 124 each have a thickness of at least three hundred and twenty microns and not more than three hundred and sixty microns. In some embodiments, the outer thickness is at least fifty microns thicker than the extension thickness and not more than two hundred microns. In other words, the step (the difference between the step thickness and the extension thickness) is at least fifty microns and not more than two hundred microns. In some embodiments, the outer step (the difference between the outer thickness and the extension thickness) is at least fifty microns and not more than two hundred microns. The outer region 128 may have a width o of at least one hundred microns and not more than three hundred microns. In some embodiments, the extension region 126 has a length e extending outwardly from the step region of at least 0.5 mm and no greater than 1.5 mm. In some embodiments, the outer region 128 has a higher mass per unit length in a direction from the anchoring region 122 than the extension region 126. This mass difference may be attributable to the larger size of the outer region 128, a density difference between portions of the cooling element 120, and / or another mechanism.

[0047] The use of the designed cooling element 120' can further improve the efficiency of the cooling system 100. The extension area 126 is thinner than the step area 124 and the outer area 128. This creates a cavity in the bottom of the cooling element 120' corresponding to the extension area 126. The presence of the cavity helps improve the efficiency of the cooling system 100. Each cantilever 123 vibrates toward the top plate 110 during the upward stroke and vibrates away from the top plate 110 during the downward stroke. When the cantilever 123 moves toward the top plate 110, the higher pressure fluid in the top chamber 140 resists the movement of the cantilever 123. In addition, the suction force in the bottom chamber 150 also resists the upward movement of the cantilever 123 during the upward stroke. In the downward stroke of the cantilever 123, the increased pressure in the bottom chamber 150 and the suction force in the top chamber 140 resist the downward movement of the cantilever 123. However, the presence of the cavity in the cantilever 123 corresponding to the extension area 126 relieves the suction force in the bottom chamber 150 during the upward stroke. The cavity also reduces the pressure increase in the bottom chamber 150 during the downward stroke. Since the suction and pressure increase are reduced in magnitude, the cantilever 123 can move through the fluid more easily. This can be achieved while substantially maintaining the higher pressure of the driving fluid in the top chamber 140 flowing through the cooling system 100. In addition, the presence of the external area 128 can improve the ability of the cantilever 123 to move through the fluid driven through the cooling system 100. The external area 128 has a higher mass per unit length and therefore has a higher momentum. Therefore, the external area 128 can improve the ability of the cantilever 123 to move through the fluid driven through the cooling system 100. The amplitude of the deflection of the cantilever 123 can also be increased. By using a thicker step area 124, these benefits can be achieved while maintaining the stiffness of the cantilever 123. In addition, the larger thickness of the external area 128 can help to pinch off the flow at the bottom of the downward stroke. Therefore, the ability of the cooling element 120' to provide a valve to prevent backflow through the orifice 132 can be improved. Therefore, the performance of cooling system 100 employing cooling element 120 ′ may be improved.

[0048] In addition, the cooling element used in the cooling system 100 is Figures 1A-1G The cooling element may have a different structure and / or be mounted differently than the cooling element depicted in . In some embodiments, the cooling element may have rounded corners and / or rounded ends, but still be anchored along a central axis so that the cantilever vibrates. The cooling element may be anchored only at its central region so that the region surrounding the anchor vibrates in a manner similar to the opening / closing of a jellyfish or umbrella. In some such embodiments, the cooling element may be circular or elliptical in shape. In some embodiments, the anchor may include pores through which a fluid can flow. Such anchors may be used to anchor the cooling element at its top (e.g., to a ceiling). Although Figures 1A-1G100 , but the piezoelectrics used to drive the cooling elements may have various locations and / or configurations. For example, the piezoelectrics may be embedded in the cooling element, attached to one side of the cooling element (or (one or more) cantilevers), may occupy some or all of the cantilever, and / or may have a location close to or far from the anchoring area. In some embodiments, cooling elements that are not centrally anchored may be used. For example, a pair of cooling elements having offset apertures, anchored at their ends (or all edges) and vibrating out of phase may be used. Thus, various additional configurations of cooling elements 120 and / or 120', anchors 160, and / or other portions of cooling system 100 may be used.

[0049] Using the cooling system 100 that is actuated to vibrate in phase or out of phase for cooling elements 120 and / or 120', the fluid drawn in through the vents 112 and driven through the orifices 132 can efficiently dissipate heat from the heat generating structure 102. Since 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 orthogonal to the heat generating structure, the fluid boundary layer at the heat generating structure can be thinned and / or partially removed. Therefore, the heat transfer between the heat generating structure 102 and the moving fluid is improved. Since the heat generating structure is cooled more efficiently, the corresponding integrated circuit can run at a higher speed and / or power for a longer time. For example, if the heat generating structure corresponds to a high-speed processor, such a processor can run for a longer time before throttling. Therefore, the performance of a device utilizing the cooling system 100 can be improved. In addition, the cooling system 100 can be a MEMS device. Therefore, the cooling system 100 may be suitable for use in smaller devices and / or mobile devices (such as smart phones, other mobile phones, virtual reality headsets, tablet computers, two-in-one computers, wearable devices, and handheld game consoles) where limited space is available. Therefore, the performance of such devices can be improved. Since the cooling element 120 / 120' may vibrate at a frequency of 15kHz or higher, the user may not hear any noise associated with the actuation of the cooling element. If driven at or near the structural resonant frequency and / or the acoustic resonant frequency, the power used in operating the cooling system can be significantly reduced. The cooling element 120 / 120' does not physically contact the top plate 110 or the orifice plate 130 during vibration. Therefore, the resonance of the cooling element 120 / 120' can be maintained more easily. More specifically, the physical contact between the cooling element 120 / 120' and other structures disturbs the resonance conditions for the cooling element 120 / 120'. Disturbing these conditions can drive the cooling element 120 / 120' to lose resonance. Therefore, it will be necessary to use additional power to maintain the actuation of the cooling element 120 / 120'. In addition, the fluid flow driven by the cooling element 120 / 120' can be reduced. As discussed above, these problems are avoided by the use of pressure differentials and fluid flows. The benefits of improved quiet cooling can be achieved with limited additional power. In addition, the out-of-phase vibration of the cooling element 120 / 120' allows the position of the center of mass of the cooling element 120 / 120' to remain more stable. Although torque is applied to the cooling element 120 / 120', the force caused by the movement of the center of mass is reduced or eliminated. As a result, the vibration caused by the movement of the cooling element 120 / 120' can be reduced. In addition, the efficiency of the cooling system 100 can be improved by the use of out-of-phase vibration motions on both sides of the cooling element 120 / 120'. Therefore, the performance of the device incorporating the cooling system 100 can be improved.Furthermore, the cooling system 100 may be used in other applications (eg, with or without the heat generating structure 102 ) where high fluid flow and / or velocity is desired.

[0050] Figure 2A-2B An embodiment of an active MEMS cooling system 200 including a top centrally anchored cooling element is depicted. Figure 2A A side view of cooling system 200 is depicted in a neutral position. Figure 2B A top view of cooling system 200 is depicted. Figure 2A-2B For simplicity, only a portion of the cooling system 200 is shown. Figure 2A-2B , cooling system 200 is similar to cooling system 100. Therefore, similar components have similar references. For example, cooling system 200 is used in conjunction with a heat generating structure 202 that is similar to heat generating structure 102.

[0051] The cooling system 200 includes a top plate 210 with vents 212, a cooling element 220 with a tip 221, an orifice plate 230 including an orifice 232, a top chamber 240 with a gap, a bottom chamber 250 with a gap, a flow chamber 240 / 250, and an anchor (i.e., a support structure) 260, which are similar to the top plate 110 with vents 112, the cooling element 120 with a tip 121, the orifice plate 130 including an orifice 132, the top chamber 140 with a gap 142, the bottom chamber 150 with a gap 152, the flow chamber 140 / 150, and the anchor (i.e., a support structure) 160, respectively. A base 290 similar to the base 190 is also shown. Thus, the cooling element 220 is centrally supported by the anchor 260 so that at least a portion of the periphery of the cooling element 220 is free to vibrate. In some embodiments, the anchor 260 extends along the axis of the cooling element 220. In other embodiments, the anchor 260 is located only near the central portion of the cooling element 220. Figure 2A and 2B 1 , but cooling element 220 includes an anchor region and a cantilever including a step region, an extension region, and an outer region, which are similar to the anchor region 122, cantilever 123, step region 124, extension region 126, and outer region 128 of cooling element 120'. In some embodiments, the cantilever of cooling element 220 is driven in phase. In some embodiments, the cantilever of cooling element 220 is driven out of phase. In some embodiments, a simple cooling element such as cooling element 120 can be used.

[0052] The anchor 260 supports the cooling element 220 from above. Thus, the cooling element 220 is suspended from the anchor 260. The anchor 260 is suspended from the top plate 210. The top plate 210 includes vents 213. The vents 212 on the sides of the anchor 260 provide a path for fluid to flow into the sides of the chamber 240.

[0053] As discussed above with respect to the cooling system 100, the cooling element 220 can be driven to vibrate at or near the structural resonant frequency of the cooling element 220. In addition, the structural resonant frequency of the cooling element 220 can be configured to align with the acoustic resonance of the chamber 240 / 250. The structural resonant frequency and the acoustic resonant frequency are generally selected to be in the ultrasonic range. For example, the vibratory motion of the cooling element 220 can be at the frequencies described with respect to the cooling system 100. As a result, efficiency and flow rate can be improved. However, other frequencies can be used.

[0054] The cooling system 200 operates in a similar manner to the cooling system 100. The cooling system 200 thus shares the benefits of the cooling system 100. Thus, the performance of an apparatus employing the cooling system 200 may be improved. Additionally, suspending the cooling element 220 from the anchor 260 may further improve performance. In particular, vibrations in the cooling system 200 that may affect other cooling units (not shown) may be reduced. For example, smaller vibrations may be induced in the top plate 210 due to the movement of the cooling element 220. Thus, crosstalk between the cooling system 200 and other cooling systems (e.g., other units) or other parts of an apparatus incorporating the cooling system 200 may be reduced. Thus, performance may be further improved.

[0055] Figures 3A-3E An embodiment of an active MEMS cooling system 300 is depicted that includes multiple cooling units configured as modules called tiles or arrays. Figure 3A depicts a perspective view, while Figure 3B-3E A side view is depicted. Figures 3A-3ENot drawn to scale. Cooling system 300 includes four cooling units 301A, 301B, 301C, and 301D (collectively or generally referred to as 301), which are similar to one or more cooling systems described herein. More specifically, cooling unit 301 is similar to cooling system 100 and / or 200. Thus, tile 300 includes four cooling units 301 (i.e., four MEMS ejectors). Although four cooling units 301 in a 2x2 configuration are shown, in some embodiments, another number and / or another configuration of cooling units 301 may be employed. In the illustrated embodiment, the cooling unit 301 includes a common top plate 310 having apertures 312, a cooling element 320, a common orifice plate 330 including apertures 332, a top chamber 340, a bottom chamber 350, an anchor (support structure) 360, and a base 390, which are similar to the top plate 110 having apertures 112, the cooling element 120, the orifice plate 130 having apertures 132, the top chamber 140, the bottom chamber 150, the anchor 160, and the base 190. In some embodiments, the cooling units 301 can be manufactured together and separated, for example, by cutting through the top plate 310, the side walls between the cooling units 301, and the orifice plate 330. Therefore, although described in the context of a common top plate 310 and a common orifice plate 330, the cooling units 301 can be separated after manufacturing. In some embodiments, tabs (not shown) and / or other structures (such as anchors 360) can connect the cooling units 301. Additionally, in the illustrated embodiment, the tile 300 includes a heat generating structure (hereinafter referred to as a heat sink) 302 (e.g., a heat sink, heat sink, and / or other structure) that also has side walls or enclosures. A cover plate 306 having apertures therein is also shown. The heat sink 302 and cover plate 306 can be part of the integrated tile 300 as shown, or can be separate from the tile 300 in other embodiments. The heat sink 302 and cover plate 306 can direct fluid flow away from the cooling unit 301, provide mechanical stability, and / or provide protection. Electrical connection to the cooling unit 301 is via a flexible connector 380 ( Figure 3B-5 E) is provided, the flexible connector 380 can accommodate the drive electronics 385. The cooling element 320 is driven out of phase (i.e., in a seesaw-like manner). In addition, as Figure 3B-3C and Figure 3D-3E As can be seen in FIG, the cooling element 320 in one unit is driven out of phase with the cooling element(s) 320 in(s) the adjacent unit(s). Figure 3B-3C , the rows of cooling elements 320 are driven out of phase. Thus, the cooling elements 320 in cell 301A are out of phase with the cooling elements 320 in cell 301B. Similarly, the cooling elements 320 in cell 301C are out of phase with the cooling elements 320 in cell 301D. Figure 3D-3E, the cooling elements 320 in a row are driven out of phase. Thus, the cooling elements 320 in unit 301A are out of phase with the cooling elements 320 in unit 301C. Similarly, the cooling elements 320 in unit 301B are out of phase with the cooling elements 320 in unit 301D. By driving the cooling elements 320 out of phase, vibrations in the cooling system 300 can be reduced. In some embodiments, the cooling elements 320 can be driven in another manner.

[0056] The cooling unit 301 of the cooling system 300 functions in a similar manner to the cooling system(s) 100, 200, and / or similar cooling systems. Therefore, the benefits described herein may be shared by the cooling system 300. Since the cooling elements in nearby units are driven out of phase, vibrations in the cooling system 300 may be reduced. Since multiple cooling units 301 are used, the cooling system 300 may enjoy increased cooling capacity. In addition, multiple individual cooling units 301 and / or cooling systems 300 may be combined in various ways to obtain the desired coverage area of ​​the cooling unit.

[0057] Figure 4 An embodiment of an active MEMS cooling system 400 for use in a watertight device is depicted. The MEMS cooling system 400 may also be considered a heat transfer system or a fluid transfer system. For example, the transfer of fluid by the cooling system 400 removes heat from a heat generating structure 402 and from a device (e.g., a processor and / or a battery) coupled to the heat generating structure 402. However, for simplicity, the system 400 is referred to as a cooling system. Figure 4 Not drawn to scale. For simplicity, only portions of cooling system 400 are shown. Cooling system 400 is similar to cooling system(s) 100, 200, and / or 300. Therefore, similar components have similar references. For example, cooling system 400 is used in conjunction with a heat generating structure 402, which is similar to heat generating structure(s) 102, 202, and 302. In the illustrated embodiment, heat generating structure 402 is a heat sink integrated into system 400. Heat sink 402 is thermally coupled to heat source(s), such as integrated circuit(s), battery(s), and / or component(s) for which cooling is desired.

[0058] Cooling system 400 includes a top plate 410 having vent(s) 412 (only one of which is shown), a cooling element 420 having a tip 421, an orifice plate 430 including an orifice 432 and a cavity 434, a top chamber 440 having a gap, a bottom chamber 450 having a gap, a flow chamber 440 / 450, and an anchor (i.e., support structure) 460, which are similar to top plate 110 having vent 112, cooling element 120 having tip 121, orifice plate 130 including an orifice 132 and a cavity 134, a top chamber 140 having a gap 142, a bottom chamber 150 having a gap 152, a flow chamber 140 / 150, and an anchor (i.e., support structure) 160, respectively. Also shown is a base 490 similar to base 190. Cooling element 420 is centrally supported by anchor 460 so that at least a portion of the periphery of cooling element 420 is free to vibrate. In some embodiments, the anchor 460 extends along the axis of the cooling element 220. In other embodiments, the anchor 460 is only located near the central portion of the cooling element 420. In some embodiments, the cooling element 420 is similar to the cooling element 120'. The cantilever of the cooling element 420 can be driven out of phase or in phase. In some embodiments, the cooling system 400 includes multiple cooling units similar to the cooling unit shown.

[0059] Cooling system 400 also includes cover 406 and film 470. Cover 406 is similar to cover 306 and may include multiple layers. For example, cover 406 may include an insulating layer separated by a thermally conductive layer (such as a graphite layer). The thermally conductive layer is both compliant and has a high in-plane electrical thermal conductivity. Cover 406 has pores therein. The pores allow fluid (e.g., a gas such as air) to flow into chambers 440 and 450 via vents 412. Film 470 reduces or prevents dust from entering chambers 440 and 450. In some embodiments, film 470 prevents at least ninety-nine percent of particles with a size of one micron or more from entering vents 412. Film 470 also reduces or prevents smaller particles from entering chambers 440 and 450. For example, film 470 may be or have characteristics corresponding to a MERV14 filter. In addition, it is desirable that film 470 is compliant and does not overly restrict the flow through cooling system 400. Thus, in some embodiments, the thickness of film 470 is no greater than three hundred microns. In some embodiments, the thickness of film 470 is at least one hundred microns and no greater than two hundred microns.

[0060] Flow chamber 471 has been formed in top plate 410. Flow chamber 471 has an inner wall, support member 472 resides on the inner wall and the flow chamber includes vent 412. The outer wall of flow chamber 471 includes opening 473. Cover 406 is located on the outer wall of flow chamber 471. Membrane 470 is supported by support member 472. In some embodiments, for top plate 410 with a thickness of five hundred microns, flow chamber 471 is at least three hundred microns and not more than four hundred microns in depth. It is desirable that the bottom of membrane 470 is away from the bottom (inner wall) of flow chamber 471. For example, in some embodiments, the bottom of membrane 470 is at least two hundred microns and not more than three hundred microns from the bottom of flow chamber 471.

[0061] Figure 4 Also depicted is a housing 480 of a device (e.g., a smart phone) in which the cooling system 400 is incorporated. Thus, the cooling system 400 is located in the interior of the housing 480. The housing 480 includes a pore 482 located therein, and a flow control device 484 coupled to and covering the pore 482. The flow control device 484 allows gas to flow through the pore 482, but does not allow liquid to flow into the interior of the housing 480 through the pore 482. In other words, the flow control device 484 is watertight and breathable. The flow control device 484 may be selected from a valve and a membrane. The flow control device 484 may be a valve that is closed in response to detection of water near the pore 482 (e.g., if the device is immersed in water). The flow control device 484 may be a one-way valve that is configured to only allow gas to flow out of the housing 480. In some embodiments, the flow control device 484 is a watertight and breathable membrane. For example, the flow control device 484 may be an IP68 membrane. For simplicity, the flow control device 484 is hereinafter referred to as a membrane 484. However, other structures having similar functions may also be used. When activated, the active cooling system 400 drives gas through such a membrane 484, but does not drive water through the membrane 484. Thus, gas can flow through the cooling system 400 and the device in which the cooling system 400 is incorporated, while liquid does not flow within the device.

[0062] The cooling system 400 operates in a similar manner to the cooling system 100. In some embodiments, heat from a portion of a device in which the system 400 is incorporated is transferred to the heat generating structure 402 (e.g., a heat sink) and other portions of the cooling system 400 via a heat conducting portion. The cooling element 420 is activated to undergo a vibrating motion (e.g., in a seesaw / out-of-phase configuration). The vibrating motion of the cooling element 420 draws a fluid (e.g., a gas such as air) into the vent 412, directs the gas through the flow chamber 440 / 450, and drives the gas out of the flow chamber 440 / 450 via the orifice 432. The gas travels through the cavity 434, impinges on the heat generating structure 402, and travels through the jet channel between the orifice plate 430 and the heat sink 402, and then exits the device via the aperture 482. The gas carries heat from the heat generating structure 402 and from other portions of the cooling system 400. Thus, the cooling system 400 can efficiently transfer cold to portions of the device.

[0063] To drive the gas through the system 400 and out of the pores 484, the vibrating motion of the cooling element 420 generates an oscillating pressure wave. Therefore, the gas driven by the cooling element 420 is at a high pressure. The gas also leaves the system 400 near the pores 482. As a result, the cooling system 400 drives the gas through the pores 482 even if there are obstacles to the flow, such as the membrane 484. The flow of gas through the membrane 484 is Figure 4 In other words, the cooling system 400 provides sufficient pressure to drive the gas through the membrane 484 (such as an IP68 membrane) to exit the device. In addition, the gas exiting the device through the pores 482 creates a suction force within the device. As a result, the gas is drawn through the inlet ( Figure 4 484). The gas drawn into the device may travel through another membrane or other flow control device similar to membrane 484. The entry of gas into the interior of housing 480 caused by the vibrating motion of cooling element 420 does not cause liquid to be drawn in through the corresponding watertight / breathable flow control device. In some embodiments, the inlet gas flows over other hot spots of the device before entering cooling system 400. This can improve the thermal diffusion coefficient of the device. Therefore, cooling system 400 can efficiently cool a watertight device.

[0064] The cooling system 400 shares the benefits of the cooling systems 100, 200 and / or 300. Thus, the fluid driven by the cooling system 400 efficiently cools the radiator 402, and thus cools the structure that is thermally coupled (e.g., via a conductive portion) to the radiator 402. The cooling system 400 performs this function in a watertight device. For example, the cooling system 400 provides a sufficiently high pressure airflow for the gas to leave through a watertight, gas-permeable (e.g., air) membrane 484. The gas leaving the device helps to draw additional gas into the device. The airflow can be maintained through the device when the cooling system 400 is activated. The airflow does not introduce liquid into the device. Therefore, active cooling of the watertight device can be facilitated. In addition, a portion of the cooling system 400 (e.g., the cover 406 and the radiator 402) extends to near the aperture 482. The gas leaves the cooling system 400 near the aperture 484. As a result, it is easier to guide the gas through the aperture 482. In addition to improving the gas flow, this can also result in less heat from the gas being accumulated on the portion of the device inside the housing 480. The cooling system 400 also allows for more efficient cooling of watertight devices. Thus, the performance of such devices may be improved.

[0065] Figure 5 An embodiment of an active MEMS cooling system 500 for use in a watertight device is depicted. MEMS cooling system 500 may also be considered a heat transfer system or a fluid transfer system. For example, the transfer of fluid by cooling system 500 removes heat from heat generating structure 502 and from devices (e.g., processors and / or batteries) coupled to heat generating structure 502. However, for simplicity, system 500 is referred to as a cooling system. Although Figure 5 Only a single cooling unit is shown in FIG, but multiple cooling units may also be present. Figure 5 Not drawn to scale. For simplicity, only portions of cooling system 500 are shown. Cooling system 500 is similar to cooling system(s) 100, 200, 300, and 400. Therefore, similar components have similar references. For example, cooling system 500 is used in conjunction with a heat generating structure 502, which is similar to heat generating structure(s) 102, 202, 302, and 402. In the illustrated embodiment, heat generating structure 502 is a heat sink integrated into system 500. Heat sink 502 is thermally coupled to heat source(s), such as integrated circuit(s), battery(s), and / or component(s) for which cooling is desired.

[0066] The cooling system 500 includes a top plate 510 having vent(s) 512 (only one of which is shown), a cooling element 520 having a tip 521, an orifice plate 530 including an orifice 532 and a cavity 534, a top chamber 540 having a gap, a bottom chamber 550 having a gap, a flow chamber 540 / 550, and an anchor (i.e., a support structure) 560, which are similar to the top plate 110 having vent 112, the cooling element 120 having a tip 121, the orifice plate 130 including an orifice 132 and a cavity 134, the top chamber 140 having a gap 142, the bottom chamber 150 having a gap 152, the flow chamber 140 / 150, and the anchor (i.e., a support structure) 160, respectively. A base 590 similar to the base 190 is also shown. The cooling element 520 is centrally supported by the anchor 560 so that at least a portion of the periphery of the cooling element 520 is free to vibrate. In some embodiments, the anchor 560 extends along the axis of the cooling element 220. In other embodiments, the anchor 560 is only located near the central portion of the cooling element 520. In some embodiments, the cooling element 520 is similar to the cooling element 120'. The cantilever of the cooling element 520 can be driven out of phase or in phase. In some embodiments, the cooling system 500 includes a plurality of cooling units similar to the cooling units shown. The cooling system 500 also includes a cover 506 similar to (one or more) covers 306 and 406. Although not depicted, the cooling system 500 may include a membrane, a flow chamber, and a support member similar to the membrane 470, the flow chamber 471, and the support member 472.

[0067] The cooling system 500 also includes a nozzle 561 having a top shell 562 and a bottom shell 564. In some embodiments, the top shell and the bottom shell are formed from a single piece. The nozzle 561 can be used to at least partially equalize the pressure waves generated by the vibrating motion of the cooling element 520. The nozzle 561 can also be used to direct the flow of gas. For example, the gas (at Figure 5 560) is depicted as traveling in a direction substantially perpendicular to the housing 580. In some embodiments, the nozzles 561 can be used to direct the airflow in different directions.

[0068] Figure 5Also depicted is a housing 580 of a device (e.g., a smart phone) in which the cooling system 500 is incorporated. Thus, the cooling system 500 is located in the interior of the housing 580. The housing 580 is similar to the housing 480. Thus, the housing 580 includes an aperture 582 and a flow control device 584, which is similar to the housing 480, the aperture 482, and the flow control device 484. Thus, the flow control device 584 may be a valve or a membrane. For simplicity, the flow control device 584 is generally referred to as a membrane 584 hereinafter. Thus, the membrane 584 is watertight but breathable. Thus, the device (e.g., housing 580) is watertight but breathable. Since the cooling system 500 is similar to the cooling system 400, the cooling system 500 drives the gas through the membrane 584, but does not drive the liquid through the membrane 584.

[0069] Also shown are an immersion sensor 592 and a splash shield 594. The immersion sensor 592 is shown as being located near the aperture 582 and on the outside of the housing 580. In some embodiments, the immersion sensor 592 may be located elsewhere. The immersion sensor 592 detects when the device is immersed in a liquid (e.g., water). In response to a determination by the immersion sensor 592 that the device is immersed in water, the cooling system 500 may be deactivated. Thus, if the device is immersed in liquid, the cooling system 500 does not operate to drive a fluid (e.g., gas) through the device. When the device is immersed in liquid, active cooling may be unnecessary and may damage the cooling system 500 or the device. The deactivation of the cooling system 500 when the device is immersed in liquid may extend the life of the cooling system 500 and / or the corresponding device. In addition, if the flow control device 584 is a valve, such a valve may be closed in response to a determination that the device is immersed in liquid. As a result, the device (i.e., the housing 580) may remain watertight.

[0070] The splash shield 594 allows gas to flow relatively freely from the aperture 582. The splash shield 594 also at least partially protects the aperture 582 and the membrane 584 from liquid splashed onto or around the aperture 582. If the device is immersed in liquid, the splash shield 594 may not protect the interior of the housing 580 from the liquid. Therefore, the splash shield 594 may have particular utility for a flow control device 584 that is a valve rather than a watertight, breathable membrane. In some embodiments, a non-watertight membrane (such as an IP64 membrane) may be used in conjunction with a valve at or near the aperture 582. Although a specific geometry of the splash shield 594 is shown, another geometry may also be used in some embodiments.

[0071] Cooling system 500 operates in a similar manner to cooling systems 100, 200, 300, and 400. Heat from a portion of a device in which system 500 is incorporated is transferred to heat generating structure 502 (e.g., a heat sink) and other portions of cooling system 500 via a heat conducting portion. Cooling element 520 is activated to undergo a vibrating motion. The vibrating motion of cooling element 520 draws fluid (e.g., a gas such as air) into vent 512, directs the gas through flow chamber 540 / 550, and drives the gas out of flow chamber 540 / 550 via aperture 532, through nozzle 561, and through aperture 582. The gas carries heat from heat generating structure 502 and from other portions of cooling system 500. Thus, cooling system 500 can efficiently transfer cold to portions of a device.

[0072] The vibrating motion of the cooling element 520 also generates pressure waves, causing the gas driven by the cooling element 520 to be under high pressure. The gas leaves the nozzle 561 near the aperture 582. Therefore, even if there are obstacles to the flow, such as the membrane 584, the cooling system 500 drives the gas through the aperture 582 while alleviating or preventing heat accumulation within the device. The nozzle 562 can also direct the airflow. For example, the gas can be pointed slightly downward so that it can flow more easily through the splash shield 594. In addition, the gas leaving the device through the aperture 582 creates a suction force within the device. As a result, the gas is sucked through the inlet ( Figure 5 The inlet gas is drawn into the device (i.e., into the housing 580) by the immersion sensor 592 (not shown). The gas drawn into the device may travel through another membrane or other flow control device similar to the membrane 584. The entry of the gas into the device is achieved without drawing liquid into the device. In some embodiments, the device is designed so that the inlet gas flows over other hot spots before entering the cooling system 500. This helps to improve the thermal diffusion coefficient. Therefore, the cooling system 500 can efficiently cool the watertight device. The immersion sensor 592 can not only help ensure that the flow control device 584 prevents liquid from flowing into the housing 580, but also help control the cooling system 500.

[0073] The cooling system 500 shares the benefits of the cooling systems 100, 200, 300 and / or 400. Thus, the fluid driven by the cooling system 500 efficiently cools the radiator 502 and, therefore, cools the structure that is thermally coupled (e.g., via conduction) to the radiator 502. The cooling system 500 performs this function in a watertight device. Thus, active cooling of a watertight device can be facilitated. In addition, the nozzles 561 allow for the direction of the airflow and alleviate heat buildup. The splash guard 594 helps ensure that the housing 580 remains watertight, particularly if a valve is used. The immersion sensor 592 can facilitate control of the valve and the cooling system 500. The cooling system 500 also allows for more efficient and more reliable cooling of watertight devices. Thus, the performance of such devices can be improved.

[0074] Fig. 6A -B depicts an embodiment of an active MEMS cooling system 600 used in a watertight computing device 605 and a thermal diagram of the device during use. Figure 6A-6B Not drawn to scale. Device 605 is a watertight smartphone. Device 605 includes housing 680, (one or more) integrated circuits (generally indicated) 686, camera 687 and battery 688. (One or more) integrated circuits 686 can be considered as circuit boards with (one or more) processors and / or (one or more) other integrated circuits attached thereto. Smartphone 605 includes other components, which are not explicitly depicted for clarity. Housing 680 includes pores 682A, 682B and 682C (collectively or generally referred to as (one or more) pores 682) and watertight breathable membranes 684A, 684B and 684C (collectively or generally referred to as membrane 684). Therefore, membrane 684 allows gas (e.g., air) to enter and exit housing 680 while ensuring that device 605 remains watertight. For example, membrane 684 can be an IP68 membrane. Although depicted as being located at the outer edge of device 605 , one or more of pores 682 and / or corresponding membranes 684 may be closer to a central portion of device 605 .

[0075] The cooling system 600 is similar to the cooling systems 100, 200, 300, 400 and / or 500. Therefore, the MEMS cooling system 600 can be considered as a heat transfer system or a fluid transfer system. The cooling system 600 includes a cooling unit 601 similar to the cooling unit 301. The cooling system 600 is thermally coupled to the (one or more) integrated circuits 686 via a heat sink (or vapor chamber) 683. The heat sink 683 is thermally connected to the (one or more) integrated circuits 686. In other embodiments, the cooling system 600 can be located on the (one or more) integrated circuits 686 or directly physically connected to the (one or more) integrated circuits 686 through a heat sink similar to the (one or more) heat sinks 402 and 502. Heat is transferred from the (one or more) integrated circuits 686 to the cooling system 600 via a thermally conductive portion.

[0076] The cooling system 600 operates in a similar manner to the cooling systems 100, 400, and 500. The vibrating motion of the cooling elements in the cooling unit 601 generates pressure waves that drive a fluid (i.e., a gas such as air) through the cooling system 600, through the membrane 684A, and out of the pores 682A. Heat from the integrated circuit (s) 686 is conducted to the heat sink 683, to the cooling system 600, and to the gas in the cooling system 600. The gas, and thus the transferred heat, is removed from the device 605 via the pores 682A. The airflow leaving the pores 682A can generate a low pressure area that draws the gas through the membrane (s) 684B and / or 684C and through the pores (s) 682B and / or 682C. This transfer of gas and heat via the pores 684 is achieved without the liquid flowing in or out of the pores 684.

[0077] Figure 6B is a thermal diagram depicting the transfer of heat from device 605. Figure 6B Device 605 is bright because of the heat generated by components (not labeled in FIG. 1 ). The surrounding environment is much cooler and therefore darker. Heat generated by integrated circuit(s) 686 (and / or other components) is conducted to cooling system 600. Cooling system 600 is also bright because it has heat transferred to it. Cooling system 600 transfers the heat to the gas and drives the gas through watertight, gas-permeable membrane 684A ( Figure 6B ) and leaves the corresponding aperture 682A ( Figure 6B The heated gas 607 is located outside the device 605 and is heated due to the heat carried by the gas. Figure 6B 600 can actively and efficiently cool a watertight device. Thus, cooling system 600 shares the benefits of cooling systems 100, 200, 300, 400, and / or 500.

[0078] Figure 7 700 is a graph indicating the performance of an active MEMS cooling system in a watertight device. Although the specific shapes and behaviors of various parameters are depicted, graph 700 is only for illustrative purposes. Therefore, graph 700 does not necessarily depict the behavior of a specific device. For clarity, graph 700 is described in the context of device 605.

[0079] Graph 700 includes curves 702, 704, 706, 708, 710, and 712. Line 714 depicts the surface temperature limit of device 605. For some devices, the surface temperature limit is forty-two degrees Celsius. Curve 702 indicates the power provided to integrated circuit 686 (e.g., system on chip) versus the time when cooling system 600 is disabled. Curve 704 indicates the power provided to integrated circuit 686 (e.g., system on chip integrated circuit) versus the time when cooling system 600 is activated. Comparison of curves 702 and 704 indicates that for the disabled cooling system 600, the power provided to integrated circuit 686 is throttled (i.e., reduced to below the maximum value) earlier in time. In addition, for the disabled cooling system 600, the power provided to integrated circuit 686 after throttling can be substantially lower. This is because device 605 has more robust cooling when the cooling system is activated. Therefore, for the activated cooling system 600, the performance of integrated circuit 686 can be improved by having high power for a longer time.

[0080] Curve 706 indicates the temperature of the back cover of device 605 versus the time when cooling system 600 is deactivated. Curve 708 indicates the temperature of the back cover of device 605 versus the time when cooling system 600 is activated. Curves 706 and 708 indicate that when power is provided to integrated circuit 686, the back cover temperature rises. However, a comparison of curves 706 and 708 indicates that for curve 708 where cooling system 600 is activated, the back cover temperature rises more slowly and reaches a lower temperature. Therefore, the use of cooling system 600 also mitigates the rise in the surface temperature of the back cover of device 605.

[0081] Curve 710 indicates the temperature of the display of device 605 versus the time when cooling system 600 is deactivated. Curve 712 indicates the temperature of the display of device 605 versus the time when cooling system 600 is activated. Curves 710 and 712 indicate that when more power is provided to integrated circuit 686, the display temperature increases. Shortly after the power of integrated circuit 686 is throttled, the temperature of the display of device 605 drops below the surface temperature limit indicated by line 714. Comparison of curves 710 and 712 indicates that for curve 712, where cooling system 600 is activated, the display temperature rises more slowly and peaks at a lower temperature. Therefore, the use of cooling system 600 also mitigates the surface temperature of the display of device 605. Therefore, the use of a cooling system (such as cooling system 600) in a watertight computing device can improve the performance and usability of the device.

[0082] Figure 8 An embodiment of an active MEMS cooling system 800 for use in a watertight device 805 is depicted. Figure 8Not drawn to scale. Device 805 is a watertight smart phone. Device 805 includes housing 880, various components 881, (one or more) integrated circuits (generally indicated) 886, camera 887, battery 888 and speaker 889. Component 881 may include a SIM card, a charger, an interface, a microphone and / or other components. (One or more) integrated circuits 886 may be considered as a circuit board with (one or more) processors and / or (one or more) other integrated circuits attached thereto. Smart phone 805 may include other and / or different components that are not explicitly depicted. Housing 880 includes pores 882A, 882B, 882C and 882D (collectively or generally referred to as (one or more) pores 882) and watertight breathable membranes 884A, 884B, 884C and 884D (collectively or generally referred to as membrane 884). Therefore, membrane 884 allows gas (e.g., air) to enter and exit housing 880 while ensuring that device 805 remains watertight. For example, membrane 884 may be an IP68 membrane. Although depicted as being located at the outer edge of device 805, one or more of apertures 882 and / or corresponding membranes 884 may be closer to a central portion of device 805. Device 805 also includes channel 885 in which cooling system 800 resides. Channel 885 is configured with an inlet at aperture 882A and an outlet at aperture 882B.

[0083] The cooling system 800 is similar to the cooling systems 100, 200, 300, 400, 500 and / or 600. Therefore, the MEMS cooling system 800 can be considered as a heat transfer system or a fluid transfer system. The cooling system 800 includes a cooling unit 801 similar to the cooling units 301 and 601. The cooling system 800 is thermally coupled to (one or more) integrated circuits 886 via a heat sink (or vapor chamber) 883. The heat sink 883 is thermally connected to (one or more) integrated circuits 886. In other embodiments, the cooling system 800 may be located on (one or more) integrated circuits 886 or directly physically connected to (one or more) integrated circuits 886 through a heat sink similar to (one or more) heat sinks 402 and 502. Heat is transferred from (one or more) integrated circuits 886 to the cooling system 800 via a thermally conductive portion.

[0084] The cooling system 800 operates in a similar manner to the cooling systems 100, 400, 500, and 600. The vibrating motion of the cooling elements in the cooling unit 801 generates pressure waves that drive a fluid (i.e., a gas such as air) through the cooling system 800, through the membrane 884A, and out of the pores 882A. Heat from the integrated circuit(s) 886 is conducted to the heat sink 883, to the cooling system 800, and to the gas in the cooling system 800. The gas, and therefore the transferred heat, is removed from the device 805 through the membrane 884A via the pores 882B. The airflow exiting the pores 882B can create a low pressure area that draws the gas through the membrane 884B and through the pore(s) 882B.

[0085] Cooling system 800 shares the benefits of cooling systems 100, 200, 300, 400, 500 and / or 600. In particular, cooling system 800 can efficiently cool a watertight device. In addition, the construction of device 805 including passage 885 allows gas to flow efficiently through device 800. The ability of cooling system 800 to transfer heat from device 805 can be further improved.

[0086] Various embodiments have been described herein. Features of the embodiments may be combined in ways not explicitly disclosed. For example, film (dust cover) 470 is described for cooling system 400. However, other cooling systems including but not limited to cooling systems 100, 200, 300, 500, 600, and / or 800 may include such films.

[0087] Fig. 9 An embodiment of a method 900 for using an active cooling system is depicted. The method 900 may include steps that are not depicted for simplicity. The method 900 is described in the context of the system 800. However, the method 900 may be used with other cooling systems, including but not limited to the systems and units described herein.

[0088] At 902, a drive signal at a frequency and input voltage corresponding to a resonant state of one or more cooling elements is provided to an active MEMS cooling system. In some embodiments, a drive signal having a frequency corresponding to a resonant frequency of a particular cooling element is provided to the cooling element. In some embodiments, the drive signal is provided to a plurality of cooling elements. In such embodiments, the frequency of the drive signal corresponds to a resonant state of the one or more cooling elements being driven, a statistical measure of resonance, and / or is within a threshold of resonance as discussed above.

[0089] At 904, when the (one or more) cooling elements are driven, the (one or more) characteristics of the MEMS cooling system are monitored to provide a feedback signal corresponding to the proximity of the resonant state of the (one or more) cooling elements. In some embodiments, the (one or more) characteristics of each individual cooling element are monitored to determine the deviation of the vibration frequency of the cooling element from the resonant frequency of the cooling element. In some embodiments, the (one or more) characteristics of multiple cooling elements are monitored at 904. The (one or more) characteristics monitored may be representative of resonance and / or deviation therefrom. For example, the voltage at the cooling element, the power drawn by the cooling element, the power output by the power supply, the peak-to-peak current output by the power supply, the peak voltage output by the power supply, the average current output by the power supply, the RMS current output by the power supply, the average voltage output by the power supply, the displacement amplitude of at least one cooling element, the RMS current through the cooling element, the peak voltage at the cooling element, the average current through the cooling element, the average voltage at at least one cooling element, and / or the peak current consumed by the cooling element may be monitored. Using the (one or more) characteristics monitored, the deviation from the resonant state of the cooling element (e.g., the deviation of the drive / vibration frequency from the resonant frequency) may be determined.

[0090] At 906, the frequency and / or input voltage are adjusted based on the feedback signal. More specifically, 906 includes updating the frequency and / or input voltage based on the feedback signal at 906 to correspond to the resonant state(s) of the(s) cooling element(s). For example, the frequency of the drive signal may be updated to more closely match the resonant frequency(s). In some embodiments, updating the frequency includes changing the frequency to correspond to a maximized power draw corresponding to a vibration of the(s) cooling element(s), a maximized voltage provided at the(s) cooling element(s), a minimized voltage across the(s) cooling element(s), and / or an amplitude of a minimized current drawn by at least one cooling element. In some embodiments, 906 includes determining whether the feedback signal indicates that a drift in the resonant frequency of the(s) cooling element(s) exceeds a threshold, and identifying a new frequency in response to determining that the drift exceeds the threshold. The new frequency takes into account the drift in the resonant frequency. The method also includes setting the new frequency to the frequency of the drive signal in response to identifying the new frequency.

[0091] For example, at 902, cooling elements similar to cooling element 420 in MEMS cooling system 800 are driven. Thus, the cooling elements are driven at a frequency that is at or near a resonance of one or more of the cooling elements.

[0092] At 904, characteristics of cooling elements within the MEMS cooling system 800 are monitored. Thus, a drift from resonance of the cooling element(s) may be determined. At 906, the frequency may be adjusted based on the monitoring of 904. Thus, the MEMS cooling system 800 may be maintained at or near resonance. Due to the vibratory motion induced in the cooling elements, gas may be driven out of the smartphone through a watertight, gas-permeable membrane or other flow control device and drawn into the smartphone.

[0093] Thus, using method 900, active cooling systems, such as cooling system(s) 100, 200, 300, 400, 500, 600, and / or 800, can be efficiently driven. These cooling systems are also constructed for improved consistency, symmetry, efficiency, and / or reliability. Thus, method 900 can be used to operate an active MEMS cooling system and achieve the benefits described herein.

[0094] Although the foregoing embodiments are described in some detail for the purpose of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways to implement the invention. The disclosed embodiments are exemplary and not restrictive.

Claims

1. A computing device, comprising: a shell having a plurality of pores therein; at least one of a plurality of membranes or a plurality of valves coupled to the plurality of apertures, each of the plurality of membranes being watertight and breathable, the plurality of valves being configured to prevent water from entering through the plurality of apertures; as well as An active cooling system in the housing, the active cooling system when activated drives gas through membranes of the plurality of membranes but does not drive the water through the membranes.

2. The computing device of claim 1, wherein the computing device is a smartphone.

3. The computing device according to claim 1, further comprising: A water sensor determines whether the computing device is immersed in water, the active cooling system being deactivated in response to a determination that the computing device is immersed in water. 4 . The computing device of claim 3 , wherein the computing system comprises a plurality of vents, and wherein the plurality of vents are closed in response to the determination that the computing device is submerged in water.

5. The computing device of claim 4, further comprising: A plurality of splash shields for the plurality of apertures.

6. A computing device according to claim 1, wherein the computing device includes the plurality of membranes, and wherein the active cooling system, when activated, draws the gas into the housing through an additional membrane among the plurality of membranes but does not draw water through the additional membrane, and drives the gas through the membrane and out of the housing.

7. The computing device of claim 6, wherein the housing has a first side and a second side opposite the first side, the membrane is coupled to a first aperture on the first side, and the additional membrane is coupled to a second aperture on the second side.

8. The computing device of claim 6, wherein the active cooling system comprises a flow outlet adjacent to the membrane.

9. The computing device of claim 8, wherein the active cooling system comprises a nozzle having the flow outlet, the nozzle coupled to the housing and terminating at the membrane.

10. The computing device of claim 6, wherein the active cooling system comprises at least one cooling element that undergoes a vibratory motion when the active cooling system is activated, the vibratory motion driving the gas.

11. The computing device of claim 10, wherein the active cooling system is thermally coupled to a heat generating structure of the computing device through a heat conductor.

12. A smart phone comprising: a shell having a plurality of pores therein; at least one of a plurality of membranes or a plurality of valves coupled to the plurality of apertures, each of the plurality of membranes being watertight and breathable, the plurality of valves being configured to prevent water from entering through the plurality of apertures, the housing being watertight; as well as An active cooling system in the housing, the active cooling system when activated drives gas through membranes of the plurality of membranes but does not drive the water through the membranes.

13. The smart phone of claim 12, further comprising: A water sensor determines whether the smartphone is immersed in water, the active cooling system being deactivated in response to a determination that the smartphone is immersed in water.

14. The smartphone of claim 12, wherein the smartphone comprises the plurality of valves, and wherein the plurality of vents are closed in response to the determination that the smartphone is submerged in water.

15. The smart phone of claim 14, further comprising: A plurality of splash shields for the plurality of apertures.

16. A smart phone according to claim 12, wherein the smart phone includes the plurality of membranes, and wherein the active cooling system, when activated, draws the gas into the housing through an additional membrane among the plurality of membranes but does not draw water through the additional membrane, and drives the gas through the membrane to leave the housing.

17. The smartphone of claim 16, wherein the housing has a first side and a second side opposite the first side, the membrane being coupled to a first aperture on the first side and the additional membrane being coupled to a second aperture on the second side.

18. The smartphone of claim 16, wherein the active cooling system comprises an outflow port adjacent to the membrane.

19. The smartphone of claim 16, wherein the active cooling system comprises at least one cooling element that undergoes a vibrating motion when the active cooling system is activated, the vibrating motion driving the gas.

20. A method comprising: driving at least one cooling element of the active cooling system to undergo a vibratory motion; Wherein, the active cooling system is located in a smart phone, which includes the active cooling system, a shell having a plurality of pores therein, and at least one of a plurality of membranes or a plurality of valves connected to the plurality of pores, each of the plurality of membranes being watertight and breathable, the plurality of valves being configured to prevent water from entering through the plurality of pores, and the vibration movement of the at least one cooling element when activated drives gas through a membrane among the plurality of membranes but does not drive the water through the membrane.

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