TWI836267B - Actuator, cooling system, and method of cooling a heat-generating structure - Google Patents

Abstract

An actuator usable in a cooling system is described. The actuator includes an anchored region and a cantilevered arm. The cantilevered arm extends outward from the anchored region. The cantilevered arm includes a step region, an extension region and an outer region. The step region extends outward from the anchored region and has a step thickness. The extension region extends outward from the step region and has an extension thickness less than the step thickness. The outer region extends outward from the extension region and has an outer thickness greater than the extension thickness.

Description

Actuator, cooling system and method of cooling heat-generating structure

As the speed and computing power of computing devices increases, the heat generated by the computing devices also increases. Various mechanisms have been proposed to address the generation of heat. Active devices (such as fans) may be used to drive air through large computing devices (such as laptops or desktop computers). Passive cooling devices (such as heat sinks) may be used for smaller, mobile computing devices such as smartphones, virtual reality devices, and tablet computers. However, these active and passive devices may not be able to adequately cool mobile devices (such as smartphones) and larger devices (such as laptops and desktop computers). Therefore, additional cooling solutions for computing devices are needed.

The present invention describes an actuator that can be used in a cooling system. The actuator includes an anchoring region and a cantilever. The cantilever extends outward from the anchoring region. The cantilever includes a step region, an extension region, and an outer region. The step region extends outward from the anchoring region and has a step thickness. The extension region extends outward from the step region and has an extension thickness less than the step thickness. The outer region extends outward from the extension region and has an outer thickness greater than the extension thickness. In some embodiments, the outer thickness is at least 50 microns thicker than the extension thickness but not more than 200 microns. The outer region may have a width of at least 100 microns but not more than 300 microns. In some embodiments, the extension region has a length extending outward from the step region of at least 0.5 mm but not more than 1.5 mm.

In some embodiments, the cantilever further includes an additional step region between the step region and the extension region. The additional step area has an additional step thickness less than the step thickness but greater than the extended thickness.

In some embodiments, at least one of the step region, the extension region, and the outer region of the actuator includes a recess (several) therein. The recess (s) includes a taper such that a width of the recess increases with distance from the anchor region. For example, the taper may be selected from a linear taper, a quadratic taper, and a cubic taper. Other tapers are possible. In some embodiments, the actuator includes a cover that is constructed such that the recess (s) are inside the actuator.

In some embodiments, the actuator includes an additional cantilever. The additional cantilever extends outward from the anchoring region opposite the cantilever. The additional cantilever includes an additional step, an extension region, and an external region. The additional step region has an additional step thickness. The additional extension region extends outward from the additional step region and has an additional extension thickness less than the additional step thickness. The additional external region extends outward from the additional extension region and has an additional external thickness greater than the additional extension thickness.

The actuator can be used as a cooling element in a cooling system. The cooling system includes an anchor and the actuator. The cooling element (ie the actuator) is fixed to the anchor at the anchoring area. The cooling element is configured to undergo oscillatory motion when actuated to drive a fluid toward a heat-generating structure. In some embodiments, the cooling system includes an orifice plate having orifices therein. The orifice plate is disposed between the cooling element and the heating structure. In some embodiments, the cooling system includes cell walls configured such that a top chamber is formed between a portion of the cell walls and the cooling element and between the cell walls, the aperture Mouth plate and the cooling element A bottom chamber is formed between them. The top chamber is in fluid communication with the bottom chamber. In some embodiments, a method for cooling a heat-generating structure is described. The method includes driving a cooling element to induce oscillating motion at a frequency. In some embodiments, the cooling element is the actuator described herein. In some embodiments, the cooling element is driven substantially at a structural resonance frequency of the cantilever. In some embodiments, the cooling element is driven at or near a fluid resonant frequency.

100: Cooling system

102: Heat generating structure

110: Top plate

112:Vent

120: Cooling element

121: hanging arms

122: Anchoring area

123: Cutting edge

124:Stair area

126:Extended area

128:External area

130: Orifice plate

132: Orifice

140: Top chamber

142: Gap

142B: Gap

142C: Gap

150: Bottom chamber

152: Gap

152B: Gap

152C: Gap

160:Anchor

200A: Curve Graph

200B: Curve graph

200C: Curve graph

200D: Curve graph

200E: Curve graph

202A:Curve

202B:Curve

204A:Curve

204B:Curve

223: Piezoelectric

300A: Cooling system

300B: Cooling system

300C: Cooling system

300D: Cooling system

320A: Cooling element

320B: Cooling element

320C: Cooling element

320D: Cooling element

323: Piezoelectric

360A:Anchor

360B:Anchor

360C: Anchor

360D: Anchor

363:hole

400: Cooling system

402: Heating structure

410: Top plate

412:Vent

413:Vent

420: Cooling element

430: Orifice plate

432:orifice

440: Top chamber

450: Bottom chamber

460: Anchor

500: Cooling element

520: Cooling element

521: hanging arms

522: Anchor area

524:Stair area

526:Extended area

528: External area

529: Additional step area

600: Cooling element

601: hanging arm

602: Anchor area

604: Step area

606:Recessed area

607: Taper

608: Top edge (or cover)

609: concave part

701: Overhanging Arms

704: Step area

706: Depression area

707: Taper

708: Bottom edge (or cover)

709: concave part

801: hanging arm

804: Stair area

806:Recessed area

807:Taper

808:Top edge

809: concave part

816: Additional recessed area

817:Taper

818: Bottom edge (or cover)

900: Cooling element

901: hanging arm

902: Anchoring area

904: Step area

906:Recessed area

916: Additional recessed area

1000: Cooling element

1001: hanging arm

1002: Anchor area

1004: Step area

1006: Depression area

1101: hanging arm

1102: Anchor area

1104: Step area

1106: Depression area

1107: Taper

1108: Dashed line

1109: concave part

1201: hanging arm

1202: Anchor area

1204: Step area

1206:Recessed area

1207: Taper

1208: dashed line

1209: Concave part

1301:Cantilever

1302: Anchor area

1304:Stair area

1306:Recessed area

1307:Taper

1308: Dashed line

1309: concave part

1400: Cooling element

1421:Cantilever

1422: Anchor area

1424:Stair area

1426:Extended area

1427: Taper

1428: External area

1429: concave part

1500: Cooling system

1501: Cooling unit

1510:top plate

1512: Kong

1520: Cooling element

1530: Orifice plate

1532: Orifice

1540:Top chamber

1550: Bottom chamber

1560: Anchor (support structure)

1600: Cooling system

1601: Cooling unit

1700:Method

1702: Actuating one or more cooling elements in a cooling system to vibrate

1704: Feedback from the piezoelectric cooling element is used to adjust the drive current

a:Width

C: Length

d: distance

e: length

h: height

h1: height

h2: height

L: Length

o:Width

P: pressure

r1: distance

r2: distance

s: hole spacing

t: thickness

w:width

y: deflection

z: deflection

Various embodiments of the present invention are disclosed in the following detailed description and accompanying drawings.

Figures 1A-1F depict one embodiment of an active cooling system including engineered actuators.

2A-2E depict performance metrics for embodiments of actuators that may be used in active cooling systems that include centrally anchored cooling elements.

3A-3D depict embodiments of actuators that may be used in active cooling systems that include centrally anchored cooling elements.

Figures 4A-4B depict one embodiment of an active cooling system including an engineered actuator.

Figure 5 depicts one embodiment of an engineered actuator.

Figures 6A-6B illustrate an embodiment of an engineered actuator.

Figures 7 to 13 illustrate an embodiment of an engineered actuator.

Figures 14A-14B illustrate an embodiment of an engineered actuator.

Figures 15A-15B depict an embodiment of an active cooling system including multiple cooling units configured as a microbrick and using engineered actuators.

FIG. 16 depicts an embodiment of an active cooling system comprising a plurality of cooling units.

FIG. 17 is a flow chart depicting an embodiment of a technique for driving an actuator.

The invention may be implemented in a variety of ways, including as a program; a device; 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 coupled to the processor. In this specification, these implementations or any other form in which the invention may be employed may be referred to as techniques. In general, the order of the steps of the disclosed procedures may be varied within the scope of the invention. Unless otherwise stated, a component (such as a processor or a memory) described as being configured to perform a task may be implemented as a general component that is temporarily configured to perform a task at a given time or as a specific component that is manufactured to perform a 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).

The following provides a detailed description of one or more embodiments of the present invention and drawings illustrating the principles of the present invention. The present invention is described in conjunction with these embodiments, but the present invention is not limited to any embodiment. The scope of the present invention is limited only by the scope of the patent application, and the present invention covers many alternatives, modifications and equivalents. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. These details are provided for the purpose of example and the present invention can be practiced according to the scope of the patent application without some or all of these specific details. For the sake of clarity, technical materials known in the technical field related to the present invention are not described in detail to avoid unnecessary confusion of the present invention.

As semiconductor devices become more powerful, the heat generated during operation also increases. For example, mobile devices (such as smartphones, tablets, laptops and virtual Processors in real-world devices can operate at high clock speeds but generate large amounts of heat. Due to the heat generated, the processor can run at full speed for only a relatively short period of time. After this time, throttling occurs (eg, reducing the processor's clock speed). While throttling can reduce heat generation, it also adversely affects processor speed and, therefore, the performance of devices using the processor. As technology develops beyond 5G, this problem is expected to intensify.

Larger devices, such as laptops or desktop computers, include electric fans with rotating blades. The fan may be energized in response to an increase in temperature of one of the internal components. The fan drives air through the larger unit to cool the internal components. However, these fans are often too large for mobile devices (such as smartphones) or thin devices (tablets). Fans may also have limited effectiveness due to the boundary layer of air that exists on the surface of the component, providing a limited air velocity for the airflow across the hot surface that needs to be cooled and may generate excessive noise. Passive cooling solutions may include components such as a radiator and a heat pipe or vapor chamber to transfer heat to a heat exchanger. Although a heat sink can mitigate temperature increases at hot spots to some extent, it may not adequately address the heat generated in current and future devices. Similarly, a heat pipe or steam chamber may provide insufficient heat transfer to remove excess heat generated. Therefore, there is a need for additional cooling solutions that can be used with smaller mobile devices as well as larger devices.

Although described in the context of a cooling system, the techniques and/or devices described herein may be used in other applications. For example, these actuators can be used in other applications. Additionally, these devices are described in the context of centrally anchored actuators (ie, cooling elements). However, in some embodiments, the actuator may be anchored along an edge. In some such embodiments, only a portion (eg, half) of the actuator may be utilized.

1A-IF are diagrams depicting an exemplary embodiment of a cooling system 100 that may be used with a heat-generating structure 102 and includes a centrally anchored cooling element 120. In some practical In one embodiment, cooling system 100 includes an active cooling system. For clarity, only specific components are shown. Figures 1A-1F are not drawn to scale. Although shown to be symmetrical, cooling system 100 need not be symmetrical. 1A and 1C-IF depict a cooling system using an actuator or cooling element 120. Figure 1B is a side view of the cooling element 120.

Cooling system 100 includes a top plate 110 having vents 112 therein, a cooling element 120 , an orifice plate 130 having apertures 132 therein, a support structure (or "anchor") 160 and cavities 140 and 150 (collectively, Chamber 140/150). The cooling element 120 is supported at its central area by an anchor 160 . A region of the cooling element 120 proximate to and including portions of the cooling element's perimeter, such as the tip 123, vibrates when actuated. In some embodiments, the tip 123 of the cooling element 120 includes a portion of the perimeter furthest from the anchor 160 and experiences the greatest deflection during actuation of the cooling element 120 . For the sake of clarity, only one tip 123 of the cooling element 120 is labeled in FIG. 1A .

Figure 1A depicts cooling system 100 in an intermediate position. Therefore, cooling element 120 is shown to be substantially flat. For in-phase operation, the cooling element 120 is driven to vibrate between the positions shown in Figures 1C and 1D. This vibrating motion draws fluid (eg, air) into vent 112 at high speed and/or flow rate, through chambers 140 and 150 and out of orifice 132 . For example, the speed at which the fluid impacts the heating structure 102 may be at least thirty meters per second. In some embodiments, fluid is driven by cooling element 120 toward heat-generating structure 102 at a speed of at least forty-five meters per second. In some embodiments, fluid is driven by cooling element 120 toward heat-generating structure 102 at a speed of at least sixty meters per second. In some embodiments, other speeds are possible. The cooling system 100 is also configured so that little or no fluid is drawn back into the chamber 140/150 through the orifice 132 by the vibrating motion of the cooling element 120.

The heat generating structure 102 needs to be cooled by the cooling system 100. In some embodiments, the heat generating structure 102 generates heat. For example, the heat generating structure can be an integrated circuit. In some embodiments, the heat generating structure 102 needs to be cooled but does not generate heat itself. The heat generating structure 102 can conduct heat (e.g., from a nearby object that generates heat). For example, the heat generating structure 102 can be a heat sink or a steam chamber. Thus, the heat dissipation structure 102 may include semiconductor component(s), including individual integrated circuit components, such as processors, other integrated circuit(s) and/or chip packages; sensor(s); optical devices; one or more batteries; other components of an electronic device, such as a computing device; heat sink; heat pipe; other electronic components and/or other devices that require cooling.

It is contemplated that devices in which cooling system 100 is used may also have limited space for placement of a cooling system. For example, cooling system 100 may be used in computing devices. Such computing devices may include, but are not limited to, smartphones, tablets, laptops, slates, 2-in-1 laptops, handheld gaming systems, digital cameras, virtual reality headsets, augmented reality headsets wearables, mixed reality headsets, and other thin devices. Cooling system 100 may be a microelectromechanical system (MEMS) cooling system that can be disposed within a mobile computing device and/or other device having a limited space of at least one dimension. For example, the total height of the cooling system 100 (from the top of the heating structure 102 to the top of the top plate 110) may be less than 2 millimeters. In some embodiments, the total height of cooling system 100 does not exceed 1.5 mm. In some embodiments, the total height does not exceed 250 microns. In some embodiments, this total height does not exceed 1.1 mm. In some embodiments, the overall height does not exceed 1 mm. Similarly, the distance y between the bottom of the orifice plate 130 and the top of the heating structure 102 may be small. In some embodiments, y is at least 200 microns but no more than 1 millimeter. In some embodiments, y is at least 200 microns but no more than 300 microns. Accordingly, cooling system 100 may be used in computing devices and/or other devices with at least one dimension of limited space. However, there is nothing to prevent the cooling system 100 from being used in installations that have less constraints on space and/or purposes other than cooling. Although one cooling system 100 (eg, one cooling unit) is shown, multiple cooling systems may be used. System 100 incorporates a heating structure 102 . For example, a one-dimensional or two-dimensional array of cooling units may be utilized.

The cooling system 100 is in fluid communication with one for cooling the heat generating structure 102 . The fluid can be a gas or a liquid. For example, the fluid can be air. In some embodiments, the fluid includes fluid from outside the device in which the cooling system 100 is located (eg, provided through an external vent in the device). In some embodiments, fluid is circulated within the device in which the cooling system is located (eg, in an enclosed device).

The cooling element 120 can be thought of as dividing the interior of the 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 sides and the top plate 110 . The bottom chamber 150 is formed by the aperture plate 130 , the sides, the cooling element 120 and the anchor 160 . Top chamber 140 and bottom chamber 150 are connected at the perimeter of cooling element 120 and together form chamber 140/150 (eg, an interior chamber of cooling system 100).

The size and configuration of the top chamber 140 can be a function of the size of the unit (cooling system 100), the motion of the cooling element 120, and the frequency of operation. 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 50 microns but not more than 500 microns. In some embodiments, the top chamber 140 has a height of at least 200 but not more than 300 microns.

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 typically smaller than the top chamber 140 and can help reduce fluid backflow 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 5 microns but not more than 10 microns. In some embodiments, the deflection z of the cooling element 120 (e.g., the deflection of the tip 123) has an amplitude of at least 10 microns but not more than 100 microns. In some of these embodiments, the amplitude of the deflection of the cooling element 120 is at least 10 microns but not more than 60 microns. However, the magnitude 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. Thus, the height of the bottom chamber 150 is generally dependent on the flow rate through the cooling system 100 and the flow rates of other components.

Top panel 110 includes vents 112 through which fluid can be drawn into cooling system 100 . Top vent 112 may have a size selected based on the desired sound pressure in chamber 140 . For example, in some embodiments, the width w of the vent 112 is at least 500 microns but no more than 1000 microns. In some embodiments, the width of vent 112 is at least 250 microns but no more than 2000 microns. In the embodiment shown, the vent 112 is a central opening in one of the top panels 110 . In other embodiments, vents 112 may be located elsewhere. For example, the vents 112 may be closer to one of the edges of the top panel 110 . The vent 112 may have a circular, rectangular or other shaped footprint. Although a single vent 112 is shown, multiple vents may be used. For example, the vents may be offset toward the edge of the top chamber 140 or located on the side(s) of the top chamber 140 . Although the top plate 110 is shown as being substantially flat, in some embodiments grooves and/or other structures may be provided in the top plate 110 to modify the top chamber 140 and/or the top plate 110 region above the configuration.

The cooling element 120 includes an anchoring area 122 and a cantilever 121 . Anchor region 122 is supported (eg, held in place) by anchor 160 in cooling system 100 . Cantilever 121 undergoes oscillatory motion in response to cooling element 120 being actuated. Each cantilever 121 includes a step area 124 , an extension area 126 and an outer area 128 . For clarity, the cantilever 121, step area 124, extension area 126 and outer area 128 are only labeled in Figure IB. The embodiment shown in Figures 1A to 1F , anchoring region 122 is located in the center. The step area 124 extends outwardly from the anchor area 122 . The extension area 126 extends outwardly from the step area 124 . The outer region 128 extends outwardly from the extension region 126 . In other embodiments, the anchoring region 122 may be on one edge of the actuator and the outer region 128 on the opposite edge. In these embodiments, the actuator is edge anchored.

The extended 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 extended region 126 can be considered as a depression. The extended region 126 can also be considered to provide 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. The outer thickness of the outer region 128 and the step thickness of the step region 124 are each at least 320 but not more than 360 microns. In other embodiments, other thicknesses are feasible. In some embodiments, the outer thickness is at least 50 microns thicker than the extended thickness but not more than 200 microns. In other words, the step (difference between the step thickness and the extension thickness) is at least 50 microns but not more than 200 microns. In some embodiments, the outer step (difference between the outer thickness and the extension thickness) is at least 50 microns but not more than 200 microns. The outer region 128 may have a width o of at least 100 microns but not more than 300 microns. In some embodiments, the extension region has a length e extending outward from the step region of at least 0.5 mm but not more than 1.5 mm. In some embodiments, the outer region 128 has a higher mass per unit length in the direction starting from the anchor region 122 than the extension region 126. This difference in mass may be due to the larger size of the outer region 128, a density difference between portions of the cooling element 120, and/or another mechanism.

Anchors (support structures) 160 support cooling element 120 at a central portion of cooling element 120. Thus, at least a portion of the periphery of cooling element 120 is unfixed and can vibrate freely. In some embodiments, anchors 160 extend along a central axis of cooling element 120 (e.g., perpendicular to the pages in FIGS. 1A to 1F ). In such embodiments, the vibrating portion of cooling element 120 (e.g., cantilever 121 including tip 123) moves in a cantilevered manner. Thus, cantilever 121 of cooling element 120 can move in a manner similar to the wings of a butterfly (i.e., in phase) and/or similar to a seesaw (i.e., out of phase). Thus, the cantilever 121 of the cooling element 120 vibrating in a cantilever manner vibrates in phase in some embodiments and out of phase in other embodiments. In some embodiments, the anchor 160 does not extend along an axis of the cooling element 120. In such embodiments, all portions of the periphery of the cooling element 120 vibrate freely (e.g., similar to a jellyfish). In the embodiment shown, the anchor 160 supports the cooling element 120 from the bottom of the cooling element 120. In other embodiments, the anchor 160 can support the cooling element 120 in another manner. For example, the anchor 160 can 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 but not more than 4 mm. In some embodiments, the width a of the anchor 160 is at least 2 mm but not more than 2.5 mm. The anchor 160 may occupy at least 10% but not more than 50% of the cooling element 120.

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. In the embodiment shown in Figures 1A to 1F, 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). The cooling element 120 is actuated to perform a vibrating motion as shown in Figures 1A and 1C to 1F. The vibration movement 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 close to the heat generating structure 102 (e.g., to the bottom chamber 150). The vibration movement of the cooling element 120 also draws the fluid into the top chamber 140 through the vent 112; 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.

The cooling element 120 has a length L that depends on the frequency at which the cooling element 120 is expected to vibrate. In some embodiments, the length of the cooling element 120 is at least 4 mm but not more than 10 mm. In some of these embodiments, the cooling element 120 has a length of at least 6 mm but not more than 8 mm. The depth of the cooling element 120 (e.g., perpendicular to the plane shown in Figures 1A to 1F) can vary from one quarter of L to two times 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 8 mm and driven at a frequency of at least 20 kHz but not more than 25 kHz, the cooling element thickness is at least 200 microns but not more than 350 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 100 microns but not more than 500 microns. In some embodiments, d is at least 200 microns but not more than 300 microns.

The cooling element 120 can be driven at a frequency at or near a resonant frequency of an acoustic resonance of a pressure wave of the fluid in the top chamber 140 and a resonant frequency of a structural resonance of the cooling element 120. The portion of the cooling element 120 that experiences the vibratory motion is driven at or near the resonance ("structural resonance") frequency of the cooling element 120. This portion of the cooling element 120 that experiences the vibration may be the cantilever 121 in some embodiments. The frequency of the vibration of the 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 can also be configured so that the structural resonant frequency corresponds to a resonance of a pressure wave in the fluid driven through the top chamber 140 (the acoustic resonance of the top chamber 140). The frequency of this pressure wave is called the acoustic resonance frequency. During the acoustic resonance, a pressure node occurs near the vent 112 and a pressure antinode occurs near the periphery of the cooling system 100 (e.g., near the tip 123 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. Because 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 of the fluid and n is an odd number. Therefore, the frequency v that drives the cooling element 120 is at or near the structural resonant frequency of the cooling element 120. The frequency v is also at or near the acoustic resonant frequency of at least the top chamber 140. The acoustic resonant frequency of the top chamber 140 does not vary much with changes in parameters (such as temperature and size) compared to the structural resonant frequency of the cooling element 120. Therefore, in some embodiments, the cooling element 120 can be driven at (or close to) a structural resonant frequency rather than an acoustic resonant frequency.

The orifice plate 130 has orifices 132 therein. Although a specific number and distribution of orifices 132 are shown, other numbers and/or other distributions may be used. A single orifice plate 130 is used for a single cooling system 100. In other embodiments, multiple cooling systems 100 may share an orifice plate. For example, multiple units may be provided together in a desired configuration. In these embodiments, the units may have the same size and configuration or different sizes and/or configurations. The orifice 132 is shown as having an axis oriented perpendicular to a 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 sharp angle. The orifice 132 also has side walls 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 tapered. Further, although the orifice plate 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 area between the orifice plate 130 and the heat generating structure 102.

100μm)且r2不超過1毫米(例如r2

1000μm)。在一些實施例中，孔口132距冷卻元件120之尖端123至少200微米(例如r1

200μm)。在一些此等實施例中，孔口132距冷卻元件120之尖端123至少300微米(例如r1

300μm)。在一些實施例中，孔口132具有至少100微米但不超過500微米之一寬度o。在一些實施例中，孔口132具有至少200微米但不超過300微米之一寬度。在一些實施例中，孔口間距s為至少100微米但不超過1毫米。在一些此等實施例中，孔口間距為至少400微米但不超過600微米。在一些實施例中，亦期望孔口132佔據孔口板130之面積之一特定部分。例如，孔口132可覆蓋孔口板130之覆蓋區之至少5%但不超過50%以達成通過孔口132之流體之一所需流速。在一些實施例中，孔口132覆蓋孔口板130之覆蓋區之至少8%但不 超過12%。 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 jet 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 jet channel through the orifices 132. For example, it is desirable that the location of the orifice be far enough from the tip 123 so that the suction force that pulls the fluid into the upper stroke of the cooling element 120 in the bottom chamber 150 (the tip 123 moves away from the orifice plate 130) is reduced. It is also desirable that the location of the orifice be close enough to the tip 123 so that the suction force during the upstroke of the cooling element 120 also allows a 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 during the upstroke (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. To provide the desired pressure, flow rate, suction, and net flow rate ratio, it is desirable that the orifice 132 is at least a distance r1 from the tip 123 and no more than a distance r2 from the tip 123 of the cooling element 120. In some embodiments, r1 is at least 100 microns (e.g., r1

100μm) and r2 does not exceed 1 mm (e.g. r2

In some embodiments, the orifice 132 is at least 200 microns (e.g., r1

In some of these embodiments, the orifice 132 is at least 300 microns (e.g., r1

300μm). In some embodiments, the orifice 132 has a width o of at least 100 microns but not more than 500 microns. In some embodiments, the orifice 132 has a width o of at least 200 microns but not more than 300 microns. In some embodiments, the orifice spacing s is at least 100 microns but not more than 1 mm. In some of these embodiments, the orifice spacing is at least 400 microns but not more than 600 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 5% but not more than 50% of the coverage area of the orifice plate 130 to achieve a desired flow rate of the fluid passing through the orifice 132. In some embodiments, the orifice 132 covers at least 8% but not more than 12% of the coverage area of the orifice plate 130.

In some embodiments, cooling element 120 is actuated using a piezoelectric. Therefore, the cooling element 120 can 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, cooling element 120 is actuated in another manner, including (but not limited to) providing a piezoelectric on another structure in cooling system 100 . Cooling element 120 and similar cooling elements are hereinafter referred to as piezoelectric cooling elements, although a mechanism other than a piezoelectric may be used to drive the cooling element. In some embodiments, cooling element 120 includes a piezoelectric layer on a substrate. The substrate may be a stainless steel, Ni alloy and/or Hastelloy substrate. In some embodiments, the piezoelectric layer includes multiple sub-layers formed as thin films on a substrate. In other embodiments, the piezoelectric layer may be a bulk layer affixed to the substrate. This piezoelectric cooling element 120 also includes electrodes for activating the piezoelectricity. In some embodiments, the substrate serves as an electrode. In other embodiments, a bottom electrode may be provided between the substrate and the piezoelectric layer. Other layers, including but not limited to seed layers, capping layers, passivation layers, or other layers, may be included in the piezoelectric cooling element. Therefore, a piezoelectric can be used to actuate the cooling element 120.

In some embodiments, cooling system 100 includes a chimney (not shown) or other ducting. This conduit provides a path for heated fluid to flow away from the heating structure 102 . In some embodiments, the conduits return fluid to the side of the top plate 110 away from the heat-generating structure 102 . In some embodiments, the conduits may instead direct fluid away from the heating structure 102 in one of the directions parallel to the heating structure 102 or perpendicular to the heating structure 102 but in the opposite direction (eg, toward the bottom of the page). For a device where fluid external to the device is used in the cooling system 100, ducting may direct the heated fluid to a vent. In such embodiments, additional fluid may be provided from an inlet vent. In embodiments where the device is enclosed, the duct may provide a circuitous path back to an area near the vent 112 and away from the heat-generating structure 102 . This path allows the fluid to be reused to dissipate heat before cooling the heat-generating structure 102 . In other embodiments, the ducts may be omitted or configured in another manner. Thus, the fluid is allowed to remove heat from the heating structure 102.

The operation of the cooling system 100 is described in the context of Figures 1A-1F. Although described in the context of specific pressures, gap sizes, and flow times, operation of the cooling system 100 is independent of the explanation herein. Figures 1C-1D depict in-phase operation of the cooling system 100. Referring to FIG. 1C , cooling element 120 has been actuated such that cantilever 121 and tip 123 move away from top plate 110 . Accordingly, FIG. 1C may be considered to depict the end of a downstroke of cooling element 120 . Due to the vibratory motion of the cooling element 120, the size of the gap 152 of the bottom chamber 150 has been reduced and is shown as gap 152B. Conversely, gap 142 of top chamber 140 has increased in size and is shown as gap 142B. During the downstroke, when the cooling element 120 is in the neutral position, a lower (eg, minimum) pressure is generated in the periphery. As the downstroke continues, the bottom chamber 150 decreases in size and the top chamber 140 increases in size, as shown in Figure 1C. Thus, fluid is driven out of the orifice 132 in a direction that is at or nearly perpendicular to the surface of the orifice plate 130 and/or the top surface of the heating structure 102 . The fluid is driven from the orifice 132 toward the heat-generating structure 102 at a high speed, such as in excess of 35 meters per second. In some embodiments, the fluid then travels along the surface of the heat-generating structure 102 and toward the perimeter of the heat-generating structure 102 , where the pressure is lower than the pressure near the orifice 132 . Also on the down stroke, the size of the top chamber 140 increases and a lower pressure exists in the top chamber 140 . As a result, fluid is drawn into top chamber 140 through vent 112 . The movement of fluid to the vents 112, through the orifices 132, and along the surface of the heating structure 102 is illustrated by the unlabeled arrows in Figure 1C.

The cooling element 120 is also actuated, causing the cantilever 121 and therefore the tip 123 to move away from the heat generating structure 102 and towards the top plate 110 . Therefore, FIG. 1D may be considered to depict the end of one upward stroke of cooling element 120. Due to the movement of cooling element 120, gap 142 decreases in size and appears as gap 142C. Gap 152 increases in size and is shown as gap 152C. during the upstroke During this time, when the cooling element 120 is in the neutral position, a higher (eg, maximum) pressure is generated in the periphery. As the upstroke continues, the bottom chamber 150 increases in size and the top chamber 140 decreases in size, as shown in Figure ID. Thus, fluid is driven from the top chamber 140 (eg, the perimeter of chambers 140/150) to the bottom chamber 150. Thus, the top chamber 140 acts as a nozzle for accelerating and driving the incoming fluid toward the bottom chamber 150 as the tip 123 of the cooling element 120 moves upward. The movement of fluid into the bottom chamber 150 is illustrated by the unlabeled arrow in Figure 1D. The location and configuration of the cooling element 120 and the orifice 132 are selected to reduce suction and therefore fluid backflow from the injection channel (between the heating structure 102 and the orifice plate 130) into the orifice 132 during the upstroke. Therefore, the cooling system 100 is able to drive fluid from the top chamber 140 to the bottom chamber 150 without excess heated fluid flowing back from the injection channel into the bottom chamber 150 .

The movement between the positions shown in FIG. 1C and FIG. 1D is repeated. Thus, the cooling element 120 undergoes the vibratory motion indicated in FIG. 1A and FIG. 1C to FIG. 1D , drawing fluid from the far side of the top plate 110 through the vent 112 into the top chamber 140; transferring the 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 some embodiments, this corresponds to the structural resonance of the cantilever 121. Further, the structural resonant frequency of the cooling element 120 is configured to be aligned with the acoustic resonant frequency of the chamber 140/150. The structural and acoustic resonant frequencies are typically selected to be in the ultrasonic range. For example, the frequency of the vibration motion of the cooling element 120 may be from 15kHz to 30kHz. In some embodiments, the cooling element 120 vibrates at a frequency/frequency of at least 20kHz but not more than 30kHz. The structural resonant frequency of the cooling element 120 is within 10% of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the cooling element 120 is within 5% of the acoustic resonant frequency of the cooling system 100. In some embodiments, the structural resonant frequency of the cooling element 120 is within 3% of the acoustic resonant frequency of the cooling system 100. Thus, efficiency and flow rate can be improved. However, other frequencies may be used.

The fluid driven toward the heat generating structure 102 may move substantially normal (perpendicular) to the top surface of the heat generating structure 102. In some embodiments, the fluid motion may have a non-zero sharp angle relative to normal to the top surface of the heat generating structure 102. In either case, the fluid may be rarefied and/or form holes in the fluid boundary layer at the heat generating structure 102. Thus, heat transfer from the heat generating structure 102 may be improved. The fluid is deflected away from the heat generating structure 102, traveling along the surface of the heat generating structure 102. In some embodiments, the fluid moves in a direction substantially parallel to the top of the heat generating structure 102. Thus, heat from the heat generating structure 102 may be extracted by the fluid. The fluid may exit the area between the orifice plate 130 and the heat generating structure 102 at the edge of the cooling system 100. Chimneys or other ducting (not shown) at the edge of the cooling system 100 allow the fluid to be carried 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 manner. The fluid may exchange heat transferred from the heat generating structure 102 to another structure or the surrounding environment. Thus, the fluid at the far side of the top plate 110 may remain relatively cool, allowing additional heat extraction. In some embodiments, the fluid is circulated and returned to the far side of the top plate 110 after cooling. In other embodiments, the heated fluid is carried away from the cooling element 120 and replaced by new fluid. Thus, the heat generating structure 102 can be cooled.

Figures IE-IF depict one embodiment of a cooling system 100 including centrally anchored cooling elements 120, wherein the cooling elements are driven out of phase. More specifically, the cantilevers 121 of the cooling element 120 on the opposite side of the anchor 160 (and thus on the opposite side of the central anchoring region 122 of the cooling element 120 supported by the anchor 160) are driven to vibrate out of phase. In some embodiments, the cantilevers 121 of the cooling element 120 on opposite sides of the anchor 160 are driven at or near 180 degrees out of phase. Therefore, one cantilever 121 of the cooling element 120 vibrates towards the top plate 110 and the other cantilever 121 of the cooling element 120 vibrates towards the orifice plate 130/heat-generating structure 102 . One of the cooling elements 120 Movement of the cantilever 121 toward the top plate 110 (an upstroke) drives fluid in the top chamber 140 to the bottom chamber 150 on that side of the anchor 160 . Movement of a portion of the cooling element 120 toward the orifice plate 130 drives fluid through the orifice 132 and toward the heat generating structure 102 . Thus, fluid traveling at high speeds (eg, as described with respect to in-phase operation) is alternately driven out of orifices 132 on opposite sides of anchor 160 . The movement of fluid is illustrated by the unlabeled arrows in Figures 1E and 1F.

Repeat the movement between the positions shown in Figures 1E and 1F. Therefore, the cooling element 120 undergoes the vibratory motion indicated in FIGS. 1A, 1E, and 1F, alternately drawing fluid from the far side of the top plate 110 through the vents 112 into the top chambers 140 on each side of the cooling element 120; Pass fluid from each side of the top chamber 140 to the corresponding side of the bottom chamber 150; and push the fluid through the apertures 132 on each side of the anchor 160 and toward the heating structure 102. As discussed above, cooling element 120 is driven to vibrate at or near the structural resonance frequency of cooling element 120 . Further, the structural resonance frequency of cooling element 120 is configured to align with the acoustic resonance of chamber 140/150. Structural and acoustic resonant frequencies are usually chosen in the ultrasonic range. For example, the vibrational motion of the cooling element 120 may be at the frequencies described for in-phase vibrations. The structural resonance frequency of the cooling element 120 is within 10% of the acoustic resonance frequency of the cooling system 100 . In some embodiments, the structural resonant frequency of cooling element 120 is within 5% of the acoustic resonant frequency of cooling system 100 . In some embodiments. In some embodiments, the structural resonant frequency of cooling element 120 is within 3% of the acoustic resonant frequency of cooling system 100 . Therefore, efficiency and flow rate can be improved. However, other frequencies can be used.

Fluid driven toward the heating structure 102 for out-of-phase vibration may move substantially normal (perpendicular) to the top surface of the heating structure 102 in a manner similar to the in-phase operation described above. Similarly, chimneys or other conduits (not shown) at the edges of the cooling system 100 allow fluid to be carried away from the heating structure 102 . In other embodiments, the heated fluid may be generated in another manner. The heating structure 102 is further transferred. The fluid may transfer heat from the self-heating 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, thus allowing additional heat extraction. In some embodiments, the fluid is circulated, returning to the distal side of the top plate 110 after cooling. In other embodiments, the heated fluid is carried away distal to the top plate 110 and replaced with new fluid. Accordingly, the heat-generating structure 102 may be cooled.

Using the cooling system 100 that is actuated for in-phase vibration or out-of-phase vibration, the fluid drawn in through the vent 112 and driven through the orifice 132 can effectively dissipate heat from the heat generating structure 102. Because the fluid hits the heat generating structure at a sufficient speed (e.g., at least 30 meters per second) and in some embodiments is substantially normal to the heat generating structure, the boundary layer of the fluid 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. Because the heat generating structure is cooled more effectively, 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 down. Therefore, the performance of a device utilizing the cooling system 100 can be improved. Further, the cooling system 100 may be a MEMS device. Thus, the cooling system 100 may be suitable for use in smaller and/or mobile devices where limited space is available, such as smartphones, other mobile phones, virtual reality headsets, tablets, two-in-one computers, wearable devices, and handheld games. The performance of such devices may therefore be improved. Because the cooling element 120 may vibrate at a frequency of 15 kHz or higher, the user will not hear any noise associated with the actuation of the cooling element. If driven at or near structural and/or acoustic resonant frequencies, the power used in the cooling system during operation may be significantly reduced. The cooling element 120 is not in physical contact with the top plate 110 or the orifice plate 130 during vibration. Thus, the resonance of the cooling element 120 can be maintained more easily. More specifically, physical contact between the cooling element 120 and other structures disturbs the resonant conditions of the cooling element 120. Disturbing these conditions can drive the cooling element 120 out of resonance. Therefore, additional power will need to be used to maintain the actuation of the cooling element 120. Further, the flow of the fluid driven by the cooling element 120 can be reduced. As discussed above, these problems are avoided by using pressure differentials and fluid flows. The benefits of improved, quiet cooling can be achieved with limited additional power. Further, the out-of-phase vibration of the cooling element 120 allows the position of the center of mass of the cooling element 120 to remain more stable. Although a torque is applied to the cooling element 120, the force due to the movement of the center of mass is reduced or eliminated. Therefore, the vibration due to the movement of the cooling element 120 can be reduced. In addition, the efficiency of the cooling system 100 can be improved by using out-of-phase vibration motion on both sides of the cooling element 120. For the out-of-phase vibration of the cantilever 121, the vibration through the cooling system 100 can also be reduced. Therefore, the performance of the device incorporated into the cooling system 100 can be improved. Furthermore, the cooling system 100 may be used in other applications where high fluid flow rates and/or velocities are required (e.g., with or without the heat generating structure 102).

The use of the engineered cooling element 120 can further improve the efficiency of the cooling system 100. The extended region 126 is thinner than the step region 124 and the outer region 128. This results in a cavity in the bottom of the cooling element 120 corresponding to the extended region 126. The presence of this cavity helps to improve the efficiency of the cooling system 100. As discussed with respect to Figures 1A and 1C to 1F, the cantilever 121 vibrates toward the top plate 110 in an upstroke and away from the top plate 110 in a downstroke. When a cantilever 121 moves toward the top plate 110, the high-pressure fluid in the top chamber 140 resists the movement of the cantilever 121. Additionally, during the upstroke, the suction in the bottom chamber 150 also resists the upward movement of the cantilever 121. During the downstroke of the cantilever 121, the increased pressure in the bottom chamber 150 and the suction in the top chamber 140 resist the downward movement of the cantilever 121. However, the presence of the cavity in the cantilever 121 corresponding to the extension area 126 reduces the suction in the bottom chamber 150 during an upstroke. The cavity also reduces the pressure increase in the bottom chamber 150 during a downstroke. Because the magnitude of the suction and pressure increase is reduced, the cantilever 121 can move more easily through the fluid. This can be achieved by substantially maintaining a higher pressure in one of the top chambers 140, which drives the fluid flow through the cooling system 100. Thus, efficiency can be improved.

Additionally, the presence of the outer region 128 may enhance the ability of the cantilever 121 to move through fluid driven through the cooling system 100 . The outer region 128 has a higher mass and therefore a higher momentum. Thus, outer region 128 may enhance the ability of cantilever 121 to move fluid driven through cooling system 100 . The deflection magnitude of the cantilever 121 can also be increased. By using a thicker step region 124, these benefits can be achieved while maintaining the stiffness of the cantilever 121. Therefore, the efficiency of the cooling system 100 can be improved again.

Improvements can also be understood as follows. Q can be considered a measure of the efficiency of the cooling element 120. The value of Q is at least partially determined by the interaction of the cooling element 120 with the surrounding fluid (i.e., a gas such as air or a liquid), structural losses within the cooling element 120, anchoring of the cooling element 120, and/or other characteristics. Q can be considered to be defined by δ _res =Q*δ _static , where δ _res is the deflection during resonance and δ _static is the corresponding static deflection. The higher the Q value, the greater the deflection during resonance, and the slower the deflection decays (i.e., the lower the damping). Due to the engineered configuration of the cooling element 120, the cooling element is able to move better through the surrounding fluid. Thus, a higher static deflection can be achieved, the deflection can be better amplified in resonance, the power consumed to drive the cooling element 120 can be reduced, and the deflection can die out more slowly (i.e. experience reduced damping). The Q of the cooling element 120 and thus the efficiency of the cooling system 100 can thus be improved by the configuration of the cooling element 120.

The use of the engineered cooling element 120 may also improve the reliability of the cooling system 100. Due to its reduced thickness, the stiffness of the extended region 126 may be lower than the outer region 128 and the step region 124. This reduction in stiffness reduces the stress on the cooling element 120 during vibration. The cooling element 120 will be less likely to fail. Thus, the reliability of the cooling system 100 may be improved.

For example, Figures 2A-2E depict exemplary embodiments of graphs 200A, 200B, 200C, 200D, and 200E relating to the performance of cooling element 200. Graphs 200A, 200B, 200C, 200D, and 200E are for illustrative purposes only and are not intended to represent the performance of all embodiments of cooling element 120 and/or cooling system 100. Graph 200A includes curves depicting deflection (y) (curve 204A) and pressure (P) (curve 202A) of a cooling element having uniform thickness in chambers 140 and 150. Graph 200B includes curves depicting pressure (P) in chambers 140 and 150 (curve 202B) and deflection (y) of cooling element 120 (curve 204B). The magnitude of the deflection of curves 204A and 204B is the same in the embodiment shown. In some embodiments, the magnitude of the deflection is 4 microns. Due to the presence of a cavity below extension region 126, pressure curve 202B indicates that the pressure generated in the chamber of cooling element 120 is less than the pressure indicated by pressure curve 202A of a uniform actuator. Cantilever 121 can therefore more easily and efficiently move fluid through cooling system 100. Efficiency can therefore be improved.

Similarly, graphs 200C, 200D, and 200E depict stress (σ) versus deflection (y) for a uniform cooling element (graph 200C) and two embodiments of cooling element 120 (graphs 200D and 200E). Graph 200C indicates a single high stress region near the edge of anchor 160. This is the location that experiences the highest stress as the uniform cooling element deflects. Graphs 200D and 200E indicate that stress for cooling element 120 is concentrated at two locations: near anchor 160 (i.e., where cooling element 120 is free to vibrate) and near the transition region between step region 124 and extension region 126. However, the configuration of the cooling element 120 reduces the amount of stress experienced by the cooling element 120 in such areas. Because the cooling element 120 is subjected to less stress, the cooling element 120 is less likely to fail. Therefore, reliability can be improved.

3A-3D depict plan views of embodiments of cooling systems 300A, 300B, 300C, and 300D similar to active cooling systems, such as cooling system 100. Figures 3A-3D are not drawn to scale. For simplicity, only parts of cooling elements 320A, 320B, 320C and 320D and anchors 360A, 360B, 360C and 360D are shown respectively. Cooling element 320A, 320B, 320C and 320D are similar to cooling element 120. Accordingly, the size and/or materials used for cooling elements 320A, 320B, 320C, and/or 320D may be similar to the size and/or materials used for cooling element 120. Anchors (support structures) 360A, 360B, 360C, and 360D are similar to anchor 160 and are indicated by dashed lines.

For cooling elements 320A and 320B, anchors 360A and 360B are centrally located and extend along one of the central axes of cooling elements 320A and 320B, respectively. Therefore, the suspended portions (ie, cantilevers) that are actuated to vibrate are located to the right and left of anchors 360A and 360B. In some embodiments, cooling elements 320A and/or 320B are continuous structures with two portions actuated (eg, depending portions outside anchors 360A and 360B). In some embodiments, cooling elements 320A and/or 320B include separate depending portions that are each attached and actuated to anchors 360A and 360B, respectively. The overhanging portions of cooling elements 320A and 320B can thus be configured to vibrate in a manner similar to a butterfly's wing (in phase) or a seesaw (out of phase). In Figures 3A and 3B, L is the length of the cooling element, similar to that depicted in Figures 1A-1F. Likewise, in Figures 3A and 3B, the depth P of cooling elements 320A and 320B is indicated.

Also shown by the dashed lines in Figures 3A-3B is piezoelectric 323. Piezoelectric 323 is used to actuate cooling elements 320A and 320B. Although described in a piezoelectric context, another mechanism for actuating cooling elements 320A and 320B may be utilized. These other mechanisms may be at the location of piezoelectric body 323 or may be located elsewhere. In cooling element 320A, piezoelectric 323 may be fixed to the overhang or may be integrated into cooling element 320A. Further, although piezoelectric 323 is shown in FIGS. 3A and 3B as having a specific shape and size, other configurations may be used.

In the embodiment shown in FIG. 3A , anchor 360A extends the entire depth of cooling element 320A. Thus, a portion of the periphery of cooling element 320A is fixed. The unfixed portion of the periphery of cooling element 320A is part of the suspended portion that undergoes the vibrating motion. In other embodiments, the anchor need not extend the entire length of the central axis. In such embodiments, the entire periphery of the cooling element is unfixed. However, such a cooling element still has a suspended portion that is configured to vibrate in a manner described herein. For example, in FIG. 3B , anchor 360B does not extend to the periphery of cooling element 320B. Thus, the periphery of cooling element 320B is unfixed. However, anchor 360B still extends along the central axis of cooling element 320B. The cooling element 320B is still actuated, causing the suspended portion to vibrate (e.g. similar to the wings of a butterfly).

Although the cooling element 320A is depicted as a rectangle, the cooling element may have another shape. In some embodiments, the corners of the cooling element 320A may be rounded. The cooling element 320B of FIG. 3B has a rounded overhang. Other shapes are also possible. In the embodiment shown in FIG. 3B , the anchor 360B is hollow and includes a hole 363. In some embodiments, the cooling element 320B has a hole in the region of the anchor 360B. In some embodiments, the cooling element 320B includes multiple portions such that the hole is present in the region of the anchor 360B. Therefore, the fluid may be pumped through the cooling element 320B and through the anchor 360B. Therefore, the cooling element 320B may be used in place of a top plate, such as the top plate 110. In such embodiments, the holes and holes 363 in cooling element 320B may function in a manner similar to vent 112. Further, although cooling elements 320A and 320B are depicted as supported in a central region, in some embodiments, a suspended portion of cooling elements 320A and/or 320B may be omitted. In such embodiments, cooling elements 320A and/or 320B may be considered to be supported or anchored at or near an edge, while at least a portion relative to the edge is free to undergo vibratory motion. In some such embodiments, cooling elements 320A and/or 320B may include a single suspended portion that undergoes vibratory motion.

3C-3D depict plan views of embodiments of cooling systems 300C and 300D similar to active cooling systems, such as cooling system 100. For simplicity, only cooling elements 320C and 320D and anchors 360C and 360D are shown respectively. Cooling elements 320C and 320D are similar to Cooling element 120. Accordingly, the size and/or materials used for cooling elements 320C and/or 320D may be similar to the size and/or materials used for cooling element 120 . Anchors 360C and 360D are similar to anchor 160 and are indicated by dashed lines.

For cooling elements 320C and 320D, anchors 360C and 360D are confined to a central region of cooling elements 320C and 320D, respectively. Thus, the region surrounding anchors 360C and 360D undergoes vibratory motion. Cooling elements 320C and 320D may thus be configured to vibrate in a manner similar to a jellyfish or similar to the opening/closing of an umbrella. In some embodiments, the entire periphery of cooling elements 320C and 320D vibrates in phase (e.g., all moving up or down together). In other embodiments, portions of the periphery of cooling elements 320C and 320D vibrate out of phase. In FIGS. 3C and 3D , L is the length (e.g., diameter) of the cooling element, similar to that depicted in FIGS. 1A to 1F . Although cooling elements 320C and 320D are depicted as being circular, the cooling elements may have another shape. Furthermore, a piezoelectric (not shown in FIGS. 3C-3D ) and/or other mechanisms may be used to drive the vibrational motion of cooling elements 320C and 320D.

In the embodiment shown in Figure 3D, anchor 360D is hollow and has hole 363. In some embodiments, cooling element 320D has holes in the area of anchor 360D. In some embodiments, cooling element 320D includes multiple portions such that holes are present in the area of anchor 360D. Accordingly, fluid may be drawn through cooling element 320D and through anchor 360D. Fluid can exit through hole 363. Therefore, cooling element 320D may be used in place of a top plate, such as top plate 110 . In such embodiments, the holes in cooling element 320D and holes 363 may function in a manner similar to vents 112 .

A cooling system, such as cooling system 100, may utilize cooling elements 320A, 320B, 320C, 320D, and/or similar cooling elements. These cooling systems may also share the benefits of cooling system 100. Cooling using cooling elements 320A, 320B, 320C, 320D and/or similar The component's cooling system can more efficiently drive fluid toward the heat-generating structure at high speeds. Thus, heat transfer between the heating structure and the moving fluid is improved. Because the heat-generating structure is cooled more efficiently, the corresponding device may exhibit improved operation, such as operating at higher speeds and/or power for longer periods of time. Cooling systems employing cooling elements 320A, 320B, 320C, 320D, and/or similar cooling elements may be suitable for smaller and/or mobile devices in which limited space is available. The performance of these devices can therefore be improved. Because cooling elements 320A, 320B, 320C, 320D, and/or similar cooling elements can vibrate at frequencies of 15 kHz or higher, the user will not hear any noise associated with actuation of the cooling elements. If driven at or near the acoustic and/or structural resonance frequencies of cooling elements 320A, 320B, 320C, 320D and/or similar cooling elements, the power used in the cooling system can be significantly reduced in operation. Cooling elements 320A, 320B, 320C, 320D, and/or similar cooling elements may not physically contact the plate during use, allowing resonance to be more easily maintained. Limited additional power can be used to achieve the benefits of improved, quiet cooling. Thus, the performance of devices incorporating cooling elements 320A, 320B, 320C, 320D, and/or similar cooling elements may be improved.

4A-4B depict an embodiment of a cooling system 400 including a top center-anchored cooling element. In some embodiments, the cooling system 400 comprises an active cooling system. FIG. 4A depicts a side view of the cooling system 400 in a mid-position. FIG. 4B depicts a top view of the cooling system 400. FIG. 4A-4B are not drawn to scale. For simplicity, only portions of the cooling system 400 are shown. Referring to FIG. 4A-4B , the cooling system 400 is similar to the cooling system 100. Therefore, similar components have similar labels. For example, the cooling system 400 is used in conjunction with a heat generating structure 402 similar to the heat generating structure 102.

Cooling system 400 includes a top plate 410 having vents 412, a cooling element 420, an orifice plate 430 including an orifice 432, a top chamber 440 having a gap, a bottom chamber 450 having a gap, and anchors (i.e., support structures) 460, etc. respectively similar to having vents 112 The top plate 110, the cooling element 120, the orifice plate 130 including the orifice 132, the top chamber 140 with the gap 142, the bottom chamber 150 with the gap 152 and the anchor (ie, support structure) 160. Thus, cooling element 420 is centrally supported by anchor 460 such that at least a portion of the perimeter of cooling element 420 is free to vibrate. In some embodiments, anchor 460 extends along the axis of cooling element 420 (eg, in a manner similar to anchors 360A and/or 360B). In other embodiments, anchor 460 is only proximate a central portion of cooling element 420 (eg, similar to anchors 360C and/or 360D). Although not explicitly labeled in FIGS. 4A and 4B , the cooling element 420 includes an anchoring region and a cantilever. The cantilever includes a step region, an extension region, and an outer region, which are similar to the anchoring region 122 , the cantilever 121 , and the step, respectively. Area 124, extension area 126 and outer area 128. In some embodiments, the cantilevers of cooling element 420 are driven in phase. In some embodiments, the cantilevers of cooling element 420 are driven out of phase.

Anchor 460 supports cooling element 420 from above. Therefore, the cooling element 420 is suspended from the anchor 460 . Anchors 460 are suspended from the top plate 410 . Top panel 410 contains vents 413 . Vents 412 on the side of anchor 460 provide a path for fluid to flow into the side of chamber 440.

As discussed above with respect to cooling system 100 , cooling element 420 may be driven to vibrate at or near the structural resonance frequency of cooling element 420 . Further, the structural resonance frequency of cooling element 420 may be configured to align with the acoustic resonance of chamber 440/450. Structural and acoustic resonant frequencies are usually chosen in the ultrasonic range. For example, the vibrational motion of cooling element 420 may be at a frequency described with respect to cooling system 100 . Therefore, efficiency and flow rate can be improved. However, other frequencies can be used.

The cooling system 400 operates in a manner similar to the cooling system 100. The cooling system 400 thus shares the benefits of the cooling system 100. As a result, the performance of a device employing the cooling system 400 may be improved. The use of a cooling element 420 configured in a manner similar to the cooling element 120 may improve efficiency and reliability. Additionally, suspending the cooling element 420 from the anchor 460 may further improve performance. Specifically, vibrations in the cooling system 400 that may affect other cooling units (not shown) may be reduced. For example, less vibration may be induced in the top plate 410 due to the movement of the cooling element 420. Therefore, crosstalk between the cooling system 400 and other cooling systems (e.g., other units) or other parts of an apparatus incorporating the cooling system 400 can be reduced. Thus, performance can be enhanced.

FIG. 5 depicts a side view of an embodiment of a cooling element 520 or actuator. FIG. 5 is not drawn to scale. The cooling element 520 is similar to the cooling element 120. Thus, the cooling element 520 includes an anchoring region 522 and a cantilever 521 similar to the anchoring region 122 and the cantilever 121. The anchoring region 522 is held in place in a cooling system (such as the cooling system 100 and/or 400) by an anchor (such as the anchor 160 and/or 460). The cantilever 521 undergoes vibratory motion in response to the cooling element 520 being driven. Each cantilever 521 includes a step region 524, an extension region 526, and an outer region 528, which are similar to the step region 124, the extension region 126, and the outer region 128, respectively. In the embodiment shown, the anchor region 522 is located in the center. The step region 524 extends outward from the anchor region 522. The extension region 526 extends outward from the step region 524. The outer region 528 extends outward from the extension region 526. In other embodiments, the anchor region 522 can be at one edge of the actuator and the outer region 528 at opposite edges. In these embodiments, the actuator is edge anchored. Extension region 526, step region 524, and outer region 528 may have dimensions similar to the dimensions of extension region 126, step region 124, and outer region 128, respectively. In addition, as described above with respect to outer region 128, outer region 528 has a higher mass per unit distance from anchor region 522 than extension region 526.

Each cantilever 521 also includes an additional step region 529. The additional step region 529 is between the step region 524 and the extension region 526. The thickness of the additional step region 529 is between the step thickness of the step region 524 and the extension thickness of the extension region 526. The thickness range of the additional step region can be modified based on the desired frequency of vibration of the cooling element 520.

Cooling element 500 operates in a cooling system (such as cooling systems 100 and/or 400 ) in a manner similar to cooling element 120 . Therefore, cooling systems incorporating cooling element 500 share the benefits of cooling system 100 . Therefore, the performance of a device using this cooling system can be improved. The use of cooling element 520 can further improve efficiency and reliability. Therefore, performance can be enhanced.

6A-6B depict an embodiment of an engineered actuator that can be used as, for example, a cooling element in cooling systems 100 and/or 400. Thus, the actuator is described as cooling element 600. FIGS. 6A-6B are not drawn to scale. FIG. 6A depicts a side view of cooling element 600 including anchoring region 602 and cantilever 601. FIG. 6B depicts a bottom perspective view of cantilever 601. Anchoring region 602 can be used to support or hold cooling element 600 in place in a cooling system (such as cooling system 100 and/or 400) by an anchor (such as anchor 160 and/or 460). The cantilever 601 undergoes vibratory motion in response to the cooling element 600 being driven. Each cantilever 601 includes a step region 604 and a recessed region 606. In the embodiment shown, the anchor region 602 is located in the center. The step region 604 extends outward from the anchor region 602. The recessed region 606 extends outward from the step region 604. In other embodiments, the anchor region 602 may be at one edge of the actuator and the recessed region 606 may terminate at the opposite edge. In these embodiments, the actuator is edge anchored. Further, other regions (not shown) may be included in the actuator.

The recessed region 606 includes a taper 607, a top edge (or lid) 608, and a recess 609. The recess 609 between the tapers 607 is a depression in the cooling element 600. Thus, if the cooling element 600 is used in a cooling system (such as the cooling system 100 and/or 400), the recess 609 provides a cavity that can be considered to increase the size of the bottom chamber. The taper 607 has a width that decreases as the distance from the anchoring region 602 increases. Similarly, the recess 609 has a recess width that increases as the distance from the anchoring region 602 increases. For example, the taper (i.e., the variation in width) may be selected from a linear taper, a quadratic taper, and a cubic taper. Other tapers are possible. In some embodiments, the taper 607 and the recess 609 may have a constant width (i.e., no taper).

In operation, the cooling element 600 functions in a manner similar to the cooling element 120. Thus, the cooling element 600 can be driven to undergo an oscillating motion. When used in a cooling system (such as the cooling system 100 and/or 400), the cooling element 600 can drive the fluid at the speed described herein. Thus, the cooling element 600 can be used to effectively cool a heat generating structure. In addition, the recess 609 can reduce the suction/pressure increase during the upstroke/downstroke of the cantilever 601 in a manner similar to the extended area 126 of the cooling element 120. Thus, efficiency can be further improved. Further, the taper 607 can reduce the stress experienced by the cantilever 601 during the oscillating motion. Therefore, the reliability of the cooling element 600 can be improved.

Figure 7 is a perspective view of an embodiment of a cantilever 701 that may be part of a cooling element, such as cooling element 600. Figure 7 is not drawn to scale. Cantilever 701 may be adjacent to an anchoring area (not shown) that may be used to support or retain a cooling element of which cantilever 701 is a part. In some embodiments, cantilever 701 may be part of a centrally anchored cooling element or part of an edge-anchored cooling element. Cantilever 701 undergoes oscillatory motion in response to this cooling element being driven. The cantilever 701 includes a stepped area 704 and a recessed area 706. Step region 704 extends outwardly from an anchor region (not shown). The recessed area 706 extends outwardly from the stepped area 704 . Other areas (not shown) may be included in cantilever 701 .

Recessed area 706 includes taper 707, bottom edge (or cover) 708, and recess 709. Taper 707 and recess 709 are similar to taper 607 and recess 609 respectively. If cantilever 701 is used in a cooling system (such as cooling systems 100 and/or 400), bottom edge 708 abuts a bottom chamber. Therefore, if cantilever 701 is used in a cooling system (such as cooling system 100 and/or 400), recess 709 provides a cavity that can be considered to increase the size of the top chamber. Taper 707 has a variable distance stage The distance of the step area 704 increases and the width decreases. For example, the taper (ie, the change in width) may be selected from a linear taper, a quadratic taper, and a cubic taper. Other taper systems are possible. In some embodiments, taper 707 and recess 709 may have a constant width (ie, no taper).

In operation, the cantilever 701 functions in a manner similar to the cantilever 601 of the cooling element 600 . Therefore, the cantilever 701 may be driven to undergo oscillatory motion. When used in a cooling system (such as cooling system 100 and/or 400), cantilever 701 can drive fluid at the speeds described herein. Therefore, cantilever 701 can be used to effectively cool heat-generating structures. Additionally, the recess 709 may reduce suction/pressure increase during the downstroke/upstroke of the boom 701 . Therefore, efficiency can be improved. Furthermore, taper 707 may reduce the stress experienced by cantilever 701 during vibratory motion. Therefore, the reliability of the cantilever 701 can be improved.

FIG. 8 is a perspective view of an embodiment of a cantilever 801, which may be part of a cooling element, such as cooling element 600. FIG. 8 is not drawn to scale. Cantilever 801 may be adjacent to an anchoring area (not shown) that may be used to support or hold the cooling element of which cantilever 801 is a part. In some embodiments, cantilever 801 may be part of a center-anchored cooling element or part of an edge-anchored cooling element. Cantilever 801 undergoes vibratory motion in response to such a cooling element being driven. Cantilever 801 includes step area 804 and recessed area 806. Step area 804 extends outward from an anchoring area (not shown). The cantilever 801 also includes an additional recessed area 816. The recessed area 806 extends outward from the additional recessed area 816. Other areas (not shown) may be included in the cantilever 801.

The recessed region 806 includes a taper 807, a top edge 808, and a recess 809 similar to the recessed region 606, taper 607, top edge 608, and recess 609 of the cooling element 600. The additional recessed region 816 includes a taper 817, a bottom edge (or lid) 818, a top edge 808, and a recess (not labeled in FIG. 8 ). The taper 817 and the recess are similar to the taper 807 and the recess 809, respectively. However, the taper 817 and the corresponding recess are surrounded by the bottom edge 818 and the top edge 808. In some embodiments, the sides of the additional recessed region 816 may also be surrounded. If the cantilever 801 is used in a cooling system (such as the cooling system 100 and/or 400), the top edge 808 is adjacent to a top chamber and the bottom edge 818 is adjacent to a bottom cavity. Therefore, if the cantilever 801 is used in a cooling system (such as the cooling system 100 and/or 400), the recess 809 provides a cavity that can be viewed as increasing the size of the bottom cavity. Therefore, the suction force in the bottom cavity during an upstroke of the cantilever 801 and the pressure increase during the downstroke of the cantilever 801 can be reduced. Therefore, the cantilever 801 can more efficiently move fluid through the chamber. However, due to the presence of the top edge 808 and the bottom edge 818, the additional recessed area 816 does not significantly affect the pressure in the surrounding chamber. Instead, the additional recessed area 816 reduces stress.

In operation, cantilever 801 functions in a manner similar to cantilever 601 of cooling element 600 . Therefore, the cantilever 801 may be driven to undergo oscillatory motion. When used in a cooling system (such as cooling system 100 and/or 400), cantilever 801 can drive fluid at the speeds described herein. Therefore, cantilever 801 can be used to effectively cool heat-generating structures. Additionally, the recess 809 may reduce suction/pressure increase during the up/down stroke of the boom 801. Therefore, efficiency can be improved. Furthermore, both taper 807 and taper 817 may reduce the stress experienced by cantilever 801 during vibratory motion. Therefore, the reliability of the cantilever 801 can be improved.

FIG. 9 depicts a side view of an embodiment of an actuator or cooling element 900. FIG. 9 is not drawn to scale. Cooling element 900 is similar to cooling element 600 and can be used in a cooling system (such as cooling system 100 and/or 400). Thus, cooling element 900 includes an anchoring region 902 and cantilever 901 similar to anchoring region 602 and cantilever 601. Anchoring region 602 is held in place in a cooling system (such as cooling system 100 and/or 400) by an anchor (such as anchor 160 and/or 460). Cantilever 901 undergoes vibratory motion in response to cooling element 900 being driven. In the embodiment shown, the anchoring region 902 is located in the center. In other embodiments, the anchoring region 902 may be at one edge of the actuator and the recessed region 906 may be at the opposite edge. In such embodiments, the actuator is edge-anchored.

Each cantilever 901 is similar to cantilevers 601, 701 and 801. Accordingly, each cantilever includes a stepped area 904, a recessed area 906, and an additional recessed area 916. Recessed area 906 and additional recessed area 916 include tapers (not expressly shown) and recesses (not expressly shown) similar to tapers 607 and recesses 609 . In the illustrated embodiment, recessed area 906 has a top cover and a bottom cover. Thus, recessed area 906 may reduce vibration-induced stresses in this portion of cantilever 901 without substantially changing the pressure in the surrounding chamber. The additional recessed area 916 both reduces stress and affects the pressure in the top chamber where the cooling element 900 is mounted.

Cooling element 900 functions in a manner similar to cooling element 600 . Therefore, the cantilever 901 may be driven to undergo oscillatory motion. When used in a cooling system (such as cooling system 100 and/or 400), cooling element 900 can drive fluid at the velocities described herein. Therefore, the cooling element can be utilized to effectively cool the heat-generating structure. Additionally, the recessed areas 906 and additional recessed areas 916 may reduce suction/pressure increases during the downstroke/upstroke of the boom 901 . Therefore, efficiency can be improved. Furthermore, both the recessed area 906 and the additional recessed area 916 may reduce the stress experienced by the cantilever 901 during vibratory motion. Therefore, the reliability of the cooling element 900 can be improved.

Figure 10 depicts a side view of an embodiment of an actuator or cooling element 1000. Figure 10 is not drawn to scale. Cooling element 1000 is similar to cooling element 600 and may be used in a cooling system (such as cooling systems 100 and/or 400). Thus, the cooling element 1000 includes an anchor region 1002 and a cantilever 1001 similar to the anchor region 602 and the cantilever 601 . Anchor region 1002 is held in place by an anchor (such as anchors 160 and/or 460) in a cooling system (such as cooling systems 100 and/or 400). The cantilever 1001 undergoes oscillatory motion in response to the cooling element 1000 being actuated. on display In an embodiment, anchor region 1002 is located in the center. In other embodiments, the anchor area 1002 can be at one edge of the actuator and the recessed area 1006 can be at the opposite edge. In these embodiments, the actuator is edge anchored.

Each cantilever 1001 is similar to cantilevers 601, 701 and 801. Therefore, each cantilever includes a stepped area 1004 and a recessed area 1006. Recessed area 1006 includes a taper (not expressly shown) and a recess (not expressly shown) similar to taper 607 and recess 609. In the illustrated embodiment, recessed area 1006 has a top cover and a bottom cover. Thus, recessed area 1006 may reduce vibration-induced stresses in this portion of cantilever 1001 without substantially changing the pressure in the surrounding chamber.

Cooling element 1000 functions in a manner similar to cooling element 600 . Therefore, the cantilever 1001 may be driven to undergo oscillatory motion. When used in a cooling system (such as cooling system 100 and/or 400), cooling element 1000 can drive fluid at the velocities described herein. Therefore, cooling element 1000 can be used to effectively cool heat-generating structures. Additionally, the recessed area 1006 may reduce the stress experienced by the cantilever 1001 during vibratory motion. Therefore, the reliability of the cooling element 1000 can be improved.

FIGS. 11-13 depict embodiments of cantilevers 1101, 1201, and 1301, which may be part of a cooling element, such as cooling element 600. FIGS. 11-13 are not drawn to scale. Cantilevers 1101, 1201, and/or 1301 may be adjacent to an anchoring region (not shown) that may be used to support or hold the cooling element of which cantilevers 1101, 1201, and/or 1301 are a part. In some embodiments, cantilevers 1101, 1201, and/or 1301 may be part of a center-anchored cooling element or part of an edge-anchored cooling element. Suspension arms 1101, 1201, and 1301 each undergo vibratory motion in response to a cooling element being driven. Suspension arm 1101 includes a step region 1104 and a recessed region 1106. Anchor region 1102 is also shown. Step region 1104 extends outward from anchor region 1102. Recessed region 1106 extends outward from step region 1104. Suspension arm 1201 includes a step region 1204 and a recessed region 1206. Anchor region 1202 is also shown. Step region 1204 extends outward from an anchor region 1202. Recessed region 1206 extends outward from step region 1204. Cantilever 1301 includes step region 1304 and recessed region 1306. Anchor region 1302 is also shown. Region 1304 extends outward from an anchor region 1302. Recessed region 1306 extends outward from step region 1304. Other regions (not shown) may be included in cantilever 1101, 1201 and/or 1301.

The recessed regions 1106, 1206, and 1306 each include a taper 1107, 1207, and 1307, respectively, and a recess 1109, 1209, and 1309, respectively. The cantilevers 1101, 1201, and 1301 indicate that changes in the tapers 1107, 1207, and 1307 can also be used to adjust the stiffness of the cantilevers 1101, 1201, and 1301, respectively. For example, the width of the tapers 1107, 1207, and 1307 can decrease as the square of the distance from the transition between the step regions 1104, 1204, and 1304, respectively, and the recessed regions 1106, 1206, and 1306, respectively. Dashed lines 1108, 1208, and 1308 indicate how the widths of the tapers 1107, 1207, and 1307 may decrease if the widths vary linearly with the distance from the transition between the respective step regions 1104, 1204, and 1304 and the respective recessed regions 1106, 1206, 1306. In addition, the widths of the tapers 1107, 1207, and 1307 decrease at different rates. The taper 1107 decreases the most in width at the edge (e.g., approximately 90%). The taper 1207 decreases a smaller portion (e.g., approximately 75%) at the opposite edge. The taper 1307 decreases by a minimum amount (e.g., approximately 50%) at opposite edges. Other variations of width (e.g., cubic) and other tapers may be used. By customizing the manner in which the taper changes width and/or the amount by which the width changes, the reduction in stiffness and stress of the cantilever may be modified.

Suspensions 1101, 1201, and 1301 function in a manner similar to suspension 601 of cooling element 600. Thus, suspensions 1101, 1201, and 1301 can be driven to undergo vibratory motion. When used in a cooling system (such as cooling system 100 and/or 400), suspensions 1101, 1201, and 1301 can drive fluid at the speeds described herein. Thus, suspensions 1101, 1201, and 1301 can be used to effectively cool heat generating structures. Furthermore, the recessed areas can be configured to reduce stress while maintaining stiffness. Thus, the reliability of suspensions 1101, 1201, and 1301 can be improved.

14A and 14B depict side and bottom views of an embodiment of an actuator or cooling element 1400. Figures 14A-14B are not drawn to scale. Cooling element 1400 is similar to cooling element 120 and cooling element 600 . Cooling element 1400 may be used in a cooling system (such as cooling systems 100 and/or 400). Thus, cooling element 1400 includes anchor regions 1422 and cantilevers 1421 similar to anchor regions 122 and 602 and cantilevers 121 and 601 . Anchor region 1422 is held in place by an anchor (such as anchors 160 and/or 460 ) in a cooling system (such as cooling systems 100 and/or 400 ). Cantilever 1421 undergoes vibratory motion in response to cooling element 1400 being actuated. In the illustrated embodiment, anchor region 1422 is centrally located. In other embodiments, anchoring area 1422 may be at one edge of the actuator.

Each cantilever 1421 is similar to cantilever 121 and cantilevers 601, 701, and 801. Accordingly, each cantilever includes a step region 1424 , an extension region 1426 , and an exterior region 1428 similar to the step region 124 , the extension region 126 , and the exterior region 128 . The cantilevers 1421 each include an extended region 1426 having a taper 1427 and a recess 1429 similar to the taper 607 and recess 609 . Therefore, portions of the extension area 1426 are also recessed. In some embodiments, step region 1424 and/or outer region 1428 may include recesses and/or tapers instead of or in addition to extension region 1426 . Therefore, the configuration of the cooling element 120 and the recesses and/or cantilevers 701, 801, 1101, 1201 and/or 1301 of the cooling elements 600, 900 and/or 1000 can be combined in various ways.

The cooling element 1400 functions in a manner similar to the cooling elements 120 and 600. Thus, the cantilever 1421 can be driven to undergo an oscillating motion. When used in a cooling system (such as the cooling system 100 and/or 400), the cooling element 1400 can drive the fluid at the speed described herein. Thus, the cooling element 1400 can be used to effectively cool a heat generating structure. In addition, the ability of the cantilever 1421 to move through the fluid can be increased and the stress experienced by the cantilever 1421 during the oscillating motion is reduced. Thus, the efficiency, performance, and reliability of the cooling element 1400 can be improved.

The various cooling elements 120, 420, 600, 900, 1000 and 1400 and the various cantilevers 701, 801, 1101, 1201 and 1301 have been described and specific features highlighted. The various features of the cooling elements 120, 420, 600, 900, 1000 and 1400 and the various cantilevers 701, 801, 1101, 1201 and 1301 may be combined in ways not expressly described herein.

FIGS. 15A-15B depict an embodiment of a cooling system 1500 comprising a plurality of cooling units configured as a tile. In some embodiments, the cooling system 1500 comprises an active cooling system. FIG. 15A depicts a top view, while FIG. 15B depicts a side view. FIGS. 15A-15B are not drawn to scale. The cooling system 1500 comprises four cooling units 1501, which are similar to one or more of the cooling systems described herein (e.g., cooling systems 100 and/or 400). Although four cooling units 1501 in a 2x2 configuration are shown, in some embodiments, another number and/or another configuration of cooling units 1501 may be employed. In the embodiment shown, the cooling unit 1501 includes a common top plate 1510 having a hole 1512, a cooling element 1520, a common orifice plate 1530 including an orifice 1532, a top chamber 1540, a bottom chamber 1550 and an anchor (support structure) 1560, which are similar to the top plate 110 having a vent 112, the cooling element 120, the orifice plate 130 having an orifice 132, the top chamber 140, the bottom chamber 150 and the anchor 160. Although described in the context of cooling elements 1520, any combination of cooling elements 120, 420, 600, 900, 1000, and 1400 and various cantilevers 701, 801, 1101, 1201, and 1301 may be used. Although bottom anchors 1560 are shown, top anchors may be used in other embodiments. In the embodiment shown, the cooling elements 1520 are driven out of phase (i.e., in a manner similar to a seesaw). Further, the cooling elements 1520 in one unit are driven out of phase with the cooling elements in an adjacent unit.

Cooling unit 1501 of cooling system 1500 functions in a manner similar to cooling systems 100 and/or 400 . Accordingly, the benefits described herein may be achieved by cooling system 1500 use. Because cooling elements in nearby units are driven out of phase, vibrations in cooling system 1500 may be reduced. Because multiple cooling units 1501 are used, the cooling system 1500 can enjoy enhanced cooling capabilities.

Figure 16 depicts a top view of an embodiment of a cooling system 1600 including a plurality of cooling units 1601. Figure 16 is not drawn to scale. Cooling unit 1601 is similar to one or more of the cooling systems described herein, such as cooling systems 100 and/or 400 . As indicated in cooling system 1600, cooling units 1601 may be configured in a two-dimensional array of desired sizes and configurations. In some embodiments, cooling system 1600 may be considered to be composed of a plurality of microbricks 160 . Therefore, the required cooling power and configuration can be achieved.

Figure 17 is a flowchart depicting an exemplary embodiment of a method 1700 for operating a cooling system. Method 1700 may include steps not depicted for simplicity. Method 1700 is described in the context of cooling system 100 . In some embodiments, cooling system 100 includes a piezoelectric cooling system. However, method 1700 may be used with other cooling systems including, but not limited to, the systems and units described herein.

At 1702, one or more cooling elements in a cooling system are actuated to vibrate. At 1702, an electrical signal with one of the desired frequencies is used to drive the cooling element. In some embodiments, the cooling element is driven at 1702 at or near structural and/or acoustic resonance frequencies. The driving frequency can be 15kHz or higher. If multiple cooling elements are driven at 1702, the cooling elements may be driven out of phase. In some embodiments, the cooling elements are driven substantially 180 degrees out of phase. Furthermore, in some embodiments, individual cooling elements are driven out of phase. For example, different parts of a cooling element can be driven to vibrate in opposite directions (ie, similar to a seesaw). In some embodiments, individual cooling elements may be driven in phase (i.e., similar to a butterfly). Additionally, the drive signal may be provided to the anchor, the cooling element, or both. Furthermore, the anchor can be driven to bend and/or Or pan.

At 1704, feedback from the piezoelectric cooling element is used to adjust the drive current. In some embodiments, adjustments are made to maintain the frequency at or near an acoustic and/or structural resonance frequency/frequency of the cooling element and/or cooling system. The resonant frequency of a particular cooling element may drift, for example due to temperature changes. The adjustment made at 1704 allows the drift of the resonant frequency to be taken into account.

For example, at 1702, the piezoelectric cooling element 120 can be driven at its structural resonant frequency/frequency. This resonant frequency can also be at or near the acoustic resonant frequency of the top chamber 140. This can be achieved by driving the piezoelectric layer in the anchor 160 (not shown in Figures 1A to 1F) and/or the piezoelectric layer in the cooling element 120. At 1704, feedback is used to maintain the cooling element 120 in resonance, and in embodiments where multiple cooling elements are driven, 180 degrees out of phase. Therefore, the efficiency of the cooling element 120 to drive the fluid through the cooling system 100 and onto the heat generating structure 102 can be maintained. In some embodiments, 1704 includes sampling the current through the cooling element 120 and/or the current through the anchor 160 and adjusting the current to maintain resonance and low input power.

Thus, cooling elements (such as cooling elements 120, 420, 600, 900, 1000, and 1400) and various cantilevers 701, 801, 1101, 1201, and 1301 can be operated as described above. Thus, method 1700 provides for the use of the piezoelectric cooling system described herein. Thus, the piezoelectric cooling system can cool semiconductor devices more efficiently and quietly with lower power.

Although the foregoing embodiments have been described in some detail for the purpose of clarity of understanding, the present invention is not limited to the details provided. There are many alternative ways of implementing the present invention. The disclosed embodiments are illustrative and not restrictive.

100: Cooling system

102: Heating structure

110:top plate

112: Ventilation vents

120: Cooling element

123:tip

130: Orifice plate

132: Orifice

140:Top chamber

142: Gap

150: Bottom chamber

152: Gap

160:Anchor

a:Width

C:Length

d: distance

h1: height

h2: height

L: length

o:Width

r1: distance

r2: distance

s: hole spacing

t: thickness

w:width

Claims (20)

An actuator comprising: an anchor area; and a cantilever extending outwardly from the anchoring area, wherein the cantilever includes a step area extending outward from the anchoring area and having a step thickness; an extended area extending outwardly from the step area and having an extended thickness less than the thickness of the step; and An outer region extends outward from the extended region and has an outer thickness greater than the extended thickness. The actuator of claim 1, wherein the cantilever further includes: An additional step area is located between the step area and the extension area, and the additional step area has an extra step thickness smaller than the step thickness and greater than the extension thickness. The actuator of claim 1, wherein the outer thickness is at least 50 microns but no more than 200 microns thicker than the extended thickness, wherein the outer region has a width of at least 100 microns but no more than 300 microns, and wherein the extended region has A length of at least 0.5 mm but not more than 1.5 mm extending outward from the step area. The actuator of claim 1, wherein at least one of the step area, the extension area and the outer area includes at least one recess therein. An actuator as claimed in claim 4, wherein the at least one recess comprises a taper such that a width of the at least one recess increases with the distance from the anchoring area. An actuator as claimed in claim 5, wherein the taper is selected from a linear taper, a quadratic taper and a cubic taper. The actuator of claim 4 further comprises: A cover configured so that the at least one recess is inside the actuator. The actuator of claim 1 further includes: an additional cantilever extending outwardly from the anchoring area opposite the cantilever, and wherein the additional cantilever includes an additional step region extending outwardly from the anchoring region and having an additional step thickness; an additional extension area extending outwardly from the additional step area and having an additional extension thickness that is less than the thickness of the additional step; and An additional outer region extends outwardly from the additional extended region and has an additional outer thickness greater than the additional extended thickness. A cooling system comprising: an anchor; and a cooling element comprising an anchor region and a cantilever, the anchor region being secured by the anchor, the cantilever extending outwardly from the anchor region, wherein the cantilever comprises a step region extending outwardly from the anchor region and having a step thickness; an extension region extending outwardly from the step region and having an extension thickness less than the step thickness; and an outer region extending outwardly from the extension region and having an outer thickness greater than the extension thickness; wherein the cooling element is configured to undergo a vibratory motion when actuated to push a fluid toward a heat generating structure. A cooling system as claimed in claim 9, wherein the cantilever further comprises: an additional step region between the step region and the extension region, the additional step region having an additional step thickness that is less than the step thickness and greater than the extension thickness. The cooling system of claim 9, wherein at least one of the step area, the extension area and the outer area includes at least one recess therein. A cooling system as claimed in claim 11, wherein the cooling element further comprises: a cover configured so that the at least one recess is inside the cooling element. The cooling system of claim 9, wherein the cooling element further includes: an additional cantilever extending outwardly from the anchoring area opposite the cantilever, and wherein the additional cantilever includes an additional step region extending outwardly from the anchoring region and having an additional step thickness; an additional extension area extending outwardly from the additional step area and having an additional extension thickness that is less than the thickness of the additional step; and An additional outer region extends outwardly from the additional extended region and has an additional outer thickness greater than the additional extended thickness. The cooling system of claim 13 further includes: An orifice plate has a plurality of orifices, and the orifice plate is arranged between the cooling element and the heating structure. The cooling system of claim 14 further comprises: A plurality of unit walls configured to form a top chamber between a portion of the plurality of unit walls and the cooling element, and a bottom chamber between the plurality of unit walls, the orifice plate and the cooling element, the top chamber being in fluid communication with the bottom chamber. A method for cooling a heat generating structure, comprising: Driving a cooling element to induce a vibration motion at a frequency, the cooling element comprising an anchoring region and a cantilever, the cantilever extending outward from the anchoring region, wherein the cantilever comprises a step region, an extension region and an outer region, the step region extending outward from the anchoring region has a step thickness, the extension region extending outward from the step region has an extension thickness less than the step thickness, the outer region extending outward from the extension region has an outer thickness greater than the extension thickness, the cooling element being configured to undergo vibration motion when actuated to push a fluid toward a heat generating structure. Such as the method of request item 16, wherein the driver further includes: The cooling element is driven substantially at a structural resonance frequency of the cantilever. As in the method of claim 17, the driving further comprises: Driving the cooling element substantially at a fluid resonant frequency. The method of claim 16, wherein the cooling element further includes an additional cantilever extending outwardly from the anchoring area opposite the cantilever, the additional cantilever including an additional step area, an additional extension area, and an additional outer area, The additional step region extends outwardly from the anchoring region and has an additional step thickness. The additional extension region extends outwardly from the additional step region and has an additional extension thickness less than the additional step thickness. The additional outer region extends from the additional step region. The additional extension region extends outwardly and has an additional outer thickness greater than the additional extension thickness, the method further comprising: The additional cantilever is driven at this frequency. The method of claim 19, wherein driving the frequency is substantially for at least one of an additional structural resonant frequency and a fluid resonant frequency of the additional cantilever.