Micro-cooling systems and devices with associated methods of fabrication and use

Abstract

This disclosure includes description of various micro-cooling devices, systems, and methods. An example micro-cooling device includes a first substrate, a second substrate coupled to the first substrate, and a microfluidic channel formed between the first substrate and the second substrate. The example micro-cooling device further includes a fluid contained within the microfluidic channel, and a set of one or more piezoelectric actuators positioned adjacent to the microfluidic channel and configured to govern flow of the fluid within the microfluidic channel. An example micro-cooling system includes one or more of the micro-cooling devices as well as one or more sensors and control circuitry coupled to the one or more sensors and configured to govern operation of the micro-cooling device(s) accordingly.

Description

Micro-Cooling Systems and Devices with Associated Methods of Fabrication and Use PRIORITY AND RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Serial No. 63 / 563,866, filed March 11, 2024, entitled “Microfluidic Refrigeration,” which is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0002] This application relates generally to cooling systems, including but not limited to, micro-cooling devices. BACKGROUND

[0003] The performance of compute systems may be limited by heating and power dissipation. Heating is a particular problem for smaller form factors, such as on mobile devices and systems. Conventional strategies of managing heating include reducing clock frequencies, separating heat-generating components to distribute heat, and reducing ambient temperatures of the devices and systems. However, these strategies can introduce latencies and adversely affect the form factors. Additional strategies include using heat sinks and other passive cooling components, cooling fans, liquid immersion, and air / liquid recirculation systems. However, these strategies may not be suitable or sufficient for smaller devices and form factors, such as mobile phones, handheld devices, wearable devices, battery packs, and AR / VR devices. SUMMARY

[0004] The present disclosure describes amongst other things, micro-cooling devices and systems that utilize microfluidic channels to provide cooling and refrigeration. These micro- cooling devices may provide sufficient thermal power dissipation (e.g., 10-20° Celsius (C)) within a small form factor, making them well-suited for small and mobile devices. Some of the micro-cooling devices and systems described herein use magnetic particles within the microfluidic channels to increase cooling (e.g., via magneto-caloric effects). For example, a micro-cooling device may include one or more magnetic components configured to align 124151-5038-WOspins / dipoles of the magnetic particles and then allow the spins / dipoles to fall out of alignment which involves absorbing heat from an environment. In this way, the magnetic particles may be used to provide additional thermal power dissipation.

[0005] In accordance with some embodiments, a micro-cooling device comprises (i) a first substrate; (ii) a second substrate coupled to the first substrate; (iii) a microfluidic channel formed between the first substrate and the second substrate; (iv) a fluid contained within the microfluidic channel; and (v) a set of one or more piezoelectric actuators positioned adjacent to the microfluidic channel and configured to govern flow of the fluid within the microfluidic channel.

[0006] In accordance with some embodiments, a method of micro-cooling comprises (i) attaching a micro-cooling device to a heat-generating component at a first portion, where the micro-cooling device comprises a fluid within a microfluidic channel; and (ii) causing the fluid to flow through the microfluidic channel from a second portion of the microfluidic channel toward the heat-generating component, whereby heat from the heat-generating component transfers to the fluid within the microfluidic channel.

[0007] In accordance with some embodiments, a micro-cooling system comprises (i) a set of micro-cooling devices thermally couplable to a heat-generating component, the set of micro- cooling devices comprising (a) a first substrate composed of a thermally-conductive material; (b) a second substrate coupled to the first substrate; (c) a microfluidic channel formed between the first substrate and the second substrate; and (d) a fluid contained within the microfluidic channel; (ii) one or more sensors; and (iii) control circuitry coupled to the set of micro-cooling devices and the one or more sensors.

[0008] In accordance with some embodiments, a method of micro-cooling comprises: (i) attaching a micro-cooling system to a heat-generating component, where the micro-cooling system comprises a set of micro-cooling devices having a microfluidic channel with a fluid contained within; (ii) monitoring a temperature of the heat-generating component; and (iii) providing cooling, based on the monitored temperature, to the heat-generating component by causing the fluid to flow through the microfluidic channel.

[0009] In accordance with some embodiments, a microfluidic flow-control system comprises: (i) a set of one or more microfluidic channels; (ii) a set of one or more flow-control elements configured to govern flow of a fluid within the set of one or more microfluidic channels, each flow-control element of the set of one or more flow-control element positioned 124151-5038-WOadjacent to a respective microfluidic channel of the set of one or more microfluidic channels; and (iii) a piezoelectric actuator coupled to the set of one or more flow-control elements, the piezoelectric actuator configured to provide power to the set of one or more flow-control elements.

[0010] In accordance with some embodiments, a microfluidic device comprises: (i) a microfluidic channel defined by a first substrate and a second substrate; (ii) a fluid contained within the microfluidic channel, the fluid comprising a plurality of magnetic particles; and (iii) a set of magnets arranged adjacent to the microfluidic channel and configured to apply a magnetic field to align spins of the plurality of magnetic particles.

[0011] In accordance with some embodiments, a method of constructing a micro-cooling system comprises constructing a microfluidic device by: (a) obtaining a first substrate comprising a thermally-conductive material; (b) defining a closed microfluidic system comprising a microfluidic channel by attaching a second substate to the first substrate; and (c) providing a fluid to the microfluidic channel.

[0012] Thus, devices and systems are disclosed with methods for providing cooling and refrigeration. Such methods, devices, and systems may complement or replace conventional methods, devices, and systems for providing cooling and refrigeration.

[0013] The features and advantages described in the specification are not necessarily all-inclusive and, in particular, some additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims provided in this disclosure. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes and has not necessarily been selected to delineate or circumscribe the subject matter described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] So that the present disclosure can be understood in greater detail, a more particular description can be had by reference to the features of various embodiments, some of which are illustrated in the appended drawings. The appended drawings, however, merely illustrate pertinent features of the present disclosure and are therefore not necessarily to be considered limiting, for the description can admit to other effective features as the person of skill in this art will appreciate upon reading this disclosure. 124151-5038-WO

[0015] Figure (“FIG.”) 1A illustrates a plane view of an example micro-cooling device in accordance with some embodiments.

[0016] Figure 1B illustrates a plane view of another example micro-cooling device in accordance with some embodiments.

[0017] Figure 2A illustrates a plane view of another example micro-cooling device in accordance with some embodiments.

[0018] Figure 2B illustrates a side view of the example micro-cooling device of Figure 2A in accordance with some embodiments.

[0019] Figure 2C illustrates another side view of the example micro-cooling device of Figure 2A in accordance with some embodiments.

[0020] Figure 2D illustrates a side view of another example micro-cooling device in accordance with some embodiments.

[0021] Figure 2E illustrates a plane view of another example micro-cooling device in accordance with some embodiments.

[0022] Figure 3A illustrates an example magnet component in accordance with some embodiments.

[0023] Figure 3B illustrates an example magnet configuration in accordance with some embodiments.

[0024] Figure 3C illustrates another example magnet component in accordance with some embodiments.

[0025] Figure 3D illustrates another example magnet component in accordance with some embodiments.

[0026] Figures 3E-3F illustrate example magnet configurations in accordance with some embodiments.

[0027] Figure 4A illustrates an example micro-cooling system in accordance with some embodiments.

[0028] Figures 4B-4C illustrate example operation of the micro-cooling system of Figure 4A in accordance with some embodiments.

[0029] Figure 4D illustrates another example micro-cooling system in accordance with some embodiments.

[0030] Figure 5 illustrates an example micro-cooling arrangement in accordance with some embodiments. 124151-5038-WO

[0031] Figures 6A-6B illustrate an example micro-cooling power source in accordance with some embodiments.

[0032] Figure 7 illustrates another example micro-cooling system in accordance with some embodiments.

[0033] Figures 8A-8B are flow diagrams illustrating example methods for providing cooling in accordance with some embodiments.

[0034] In accordance with common practice, the various features illustrated in the drawings are not necessarily drawn to scale, and like reference numerals can be used to denote like features throughout the specification and figures. DESCRIPTION OF EMBODIMENTS

[0035] As described in the Background section above, conventional cooling techniques may not be able to provide sufficient cooling for mobile devices, wearable devices, and other devices and systems requiring specific form factors. The micro-cooling devices and systems described herein can provide cooling for such devices while maintaining a small size and / or specific form factor. For example, in some embodiments, a micro-cooling device is configured to circulate a fluid through a microfluidic channel to transfer heat away from a heat-generating component. In some embodiments, the micro-cooling device includes magnetic component(s) (e.g., a set of one or more electromagnets) to align dipoles / spins of magnetic particles (e.g., magnetic beads) contained within the fluid in the microfluidic channel.

[0036] The magnetic particles may be composed of materials such as Gadolium, Gadolium Germanium alloy, Gadolium Silicon alloy, Gadolium Dysprosium alloy. In various embodiments, the magnetic particles are composed of Lavas phase compounds, La(Fe,Si)13- based compounds, Gd5(Si,Ge)4-based compounds, Manganese Perovskite Oxide, Heusler alloy, MnAs-based compounds, (Mn,Fe)2(P,As)-based compounds, FeRh-based compounds, and / or AlFe2B2-based compounds. Aligning the dipoles / spins of the magnetic particles removes heat from the particles and subsequently allowing the dipoles / spins to fall out of alignment enables heat to be absorbed by the particles. In this way, the particles can be used to transfer heat away from a heat-generating component (e.g., a processor). In some embodiments, the magnetic particles are selected based on a target operating temperature. For example, for consumer electronics the target operating temperature may be room temperature (e.g., 21° C). In some embodiments, the magnetic particles are selected / adapted to have a maximum 124151-5038-WOmagnetic moment at the target operating system (e.g., to prevent the particles from overcooling the system). As another example, the target operating temperature may be below a superconducting threshold temperature for a superconducting material of a superconducting- based quantum computing system. For such systems the target operating temperature may be near absolute zero (e.g., -270° C).

[0037] Figure 1A illustrates a plane view of a micro-cooling device 100 in accordance with some embodiments. The micro-cooling device 100 may also be referred to as a microfluidic device. The micro-cooling device 100 includes an inlet 106 and an outlet 108 with a microfluidic channel 102 coupling the inlet 106 and the outlet 108. In some embodiments, the microfluidic channel 102 is formed by coupling a first substrate with an indentation, recess, or notch with a second substrate so that the microfluidic channel 102 is defined between the first substrate and the second substrate. The locations and shapes of the inlet 106 and the outlet 108 shown in Figure 1A are mere examples.

[0038] In accordance with some embodiments, the micro-cooling device 100 includes the inlet 106 allowing a cooling fluid (e.g., with magnetic particles) to be provided to the microfluidic channel 102. In accordance with some embodiments, the micro-cooling device 100 includes the outlet 108 allowing the cooling fluid to be removed from (e.g., ejected from) the microfluidic channel 102. In this way, the cooling fluid may be supplemented and / or replaced during use. In some embodiments, the cooling fluid (sometimes referred to herein as simply a “fluid”) is comprised of water, glycol, ethanol, and / or other type of solvent (e.g., oil), such as an organic solvent.

[0039] In some embodiments, the length of the microfluidic channel 102 (e.g., measured from the inlet 106 to the outlet 108), is in the range of 1 millimeter (mm) to 50 mm. In some embodiments, a width W (e.g., which may be the narrowest portion) of the microfluidic channel 102 may be configured based on desired flow rate, fluidic volume, and / or size of particles within the microfluidic channel 102. In some embodiments, the width W of the microfluidicchannel 102 is in the range of 10 microns ( m) to 5 mm (e.g., 200 m). In some embodiments,a height of the microfluidic channel 102 is in the range of 200 m to 2 mm (e.g., 400 m). In some embodiments, the microfluidic channel 102 includes one or more portions that have a width different from the width W. For example, as shown in Figure 1A, the microfluidic channel 102 may include portions (e.g., portion 102-A) having (protruding) shapes such that widths of the portions are greater than the width W. Similarly, the microfluidic channel 102 124151-5038-WOmay include one or more portions with widths narrower than the width W. In some embodiments, the wider the microfluidic channel 102 is, the slower is the velocity of the particles flowing in the corresponding portion of the microfluidic channel 102 (e.g., when the microfluidic channel 102 has a uniform height).

[0040] In accordance with some embodiments, the micro-cooling device 100 includes a set of flow-control elements 104. In the example of Figure 1A, the set of flow-control elements 104 includes a flow-control element 104-1 at the inlet 106, a flow-control element 104-2 within the microfluidic channel 102, and a flow-control element 104-3 at the outlet 108. In some embodiments, the micro-cooling device 100 includes a subset of the flow-control elements 104 shown in Figure 1A (e.g., may not include the flow-control element 104-1). In some embodiments, the micro-cooling device 100 includes flow-control elements at different locations (e.g., may include two or more flow-control elements along the length of the microfluidic channel 102).

[0041] In some embodiments, a flow-control element 104 comprises a piezoelectric actuator. In some embodiments, the piezoelectric actuator is a piezo micro-electro-mechanical system (MEMS) actuator. In some embodiments, a flow-control element 104 includes two or more piezoelectric actuators. In some embodiments, a flow-control element 104 is a piezoelectric element. As an example, the piezoelectric element may have a length equal to 1 mm and a width equal to 0.5 mm. In some embodiments, the micro-cooling device 100 includes actuation circuitry electrically coupled to flow-control elements 104. In some embodiments, upon application of an electrical signal from the actuation circuitry, a flow-control element 104 generates oscillations that create displacement as well as acoustic waves, which controls localized inertial movement of the fluid / particles in the microfluidic channel 102, e.g., in the three-dimensional x, y and z planes with sub-micron level control. In some embodiments, the flow-control elements 104 are configured to induce a laminar flow from the inlet 106 toward the outlet 108. In some embodiments, the flow-control elements 104 have varying shapes and sizes, while in other embodiments the flow-control elements 104 have a same shape and size.

[0042] The micro-cooling device 100 also includes a thermal-coupling portion 110. In the example of Figure 1A, the thermal-coupling portion 110 is located in proximity to the outlet 108, however, in some embodiments, the thermal-coupling portion 110 is arranged at a different position of the micro-cooling device 100 (e.g., along the microfluidic channel 102). In some embodiments, the thermal-coupling portion 110 has a substrate composed of 124151-5038-WOthermally-conductive material such that a heat-generating component may be attached or thermally-coupled to the thermal-coupling portion 110. In some embodiments, the micro- cooling device 100 includes two or more thermal-coupling portions (e.g., at intervals along the microfluidic channel 102).

[0043] Figure 1B illustrates a plane view of a micro-cooling device 150 in accordance with some embodiments. The micro-cooling device 150 is similar to the micro-cooling device 100 except that the micro-cooling device 150 includes a closed-loop microfluidic channel 102 with a portion 102-1 and a portion 102-2 (e.g., to recirculate a fluid from the thermal-coupling portion 110). In accordance with some embodiments, each portion of the microfluidic channel 102 includes a respective flow-control element 104 (e.g., the flow-control element 104-2 and the flow-control element 104-4). In some embodiments, the micro-cooling device 150 includes an inlet (e.g., the inlet 106) and / or an outlet (e.g., the outlet 108). In some embodiments, the inlet is sealed after a fluid has been input (e.g., injected) into the microfluidic channel (e.g., during fabrication of the micro-cooling device 150).

[0044] Figure 2A illustrates a plane view of a micro-cooling device 200 in accordance with some embodiments. The micro-cooling device 200 is similar to the micro-cooling device 150, except that the micro-cooling device 200 has a different shape (e.g., is less rounded) and the micro-cooling device 200 includes magnet components 202 and magnetic particles 204. In some embodiments, the micro-cooling device 200 includes rounded corners and / or tapering, e.g., to promote laminar flow of the fluid in the microfluidic channel 102. In accordance with some embodiments, the micro-cooling device 200 includes the magnet components 202 at a first side and the thermal-coupling portion 110 at a second side, opposite the first side. In some embodiments, the magnet components 202 are positioned remote from the thermal-coupling portion 110 so that heat is transferred from a heat-generating component at the thermal- coupling portion 110 through the microfluidic channel 102 to the magnet components 202. In some embodiments, the first side with the magnet components 202 includes a heat sink or other cooling component to promote thermal dissipation from the microfluidic channel 102. In some embodiments, the magnet components 202 are configured to produce an electromagnetic field that aligns spins and / or dipoles of the magnetic particles 204 (e.g., as illustrated by the portion 204-1 of the magnetic particles 204). In some embodiments, outside of the electromagnetic field, the magnetic particles are able to move out of alignment (e.g., by absorbing heat) as illustrated by portion 204-2 of the magnetic particles 204. In some embodiments, the magnetic 124151-5038-WOparticles 204 comprise two distinct types of magnetic particles. For example, a first type of magnetic particle may be configured / adapted to apply a magneto-caloric effect (as described elsewhere in this disclosure). The first type of magnetic particle may be composed of any of the magnetic materials described previously. In some embodiments, the second type of magnetic particle may be configured / adapted to provide additional magnetic domains (e.g., to enhance the magneto-caloric effect). For example, the second type of magnetic particles may be composed of magnetite, hematite, and / or the other magnetic materials. In some embodiments, the magnetic particles 204 comprise three or more types of magnetic particles (e.g., two or more distinct types of particles for applying the magneto-caloric effect and / or two or more distinct types of particles for providing additional magnetic domains).

[0045] Figure 2B illustrates a side view along the a to a axis of the micro-cooling device200 of Figure 2A in accordance with some embodiments. Figure 2B shows the microfluidic channel 102 defined by a substrate 220, a substrate 222, and a bonding layer 224. In some embodiments, the substrate 220 and / or the substrate 222 is composed of a dielectric material.

[0046] In some embodiments, the micro-cooling device 200 includes the inlet 106 and / or the outlet 108. In some embodiments, the inlet 106 and / or the outlet 108 is defined in the substrate 220 or the substrate 222. In some embodiments, the inlet 106 and the outlet 108 are defined in the same substrate. In some embodiments, the inlet 106 and the outlet 108 are defined in different substrates. In some embodiments, the microfluidic channel 102 is defined by a recess in the substrate 220 or the substrate 222. In some embodiments, the substrate 220 is composed of a same material as the substrate 222. In some embodiments, the substrate 220 is composed of a different material than the substrate 222. In some embodiments, at least one of the substrates 220 and 222 is composed of a thermally-conductive material (e.g., copper, silver, or other thermally-conductive material). For example, the substrate 222 may be composed of a silicon-on-insulator (SOI) whereas the substrate 220 may be composed of copper. In some embodiments, the microfluidic channel 102 has a height between 10 m and 1 mm. In some embodiments, the substrate 220 has a thickness in the range of 50 m to 1 mm. In some embodiments, the substrate 222 has a thickness in the range of 50 m to 1 mm.

[0047] In some embodiments, the bonding layer 224 is positioned between the substrate 220 and the substrate 222. In some embodiments, the bonding layer 224 is composed of a polymer. In some embodiments, the bonding layer 224 is adapted and / or positioned to adhere the substrate 220 to the substrate 222. For example, if the bonding layer 224 is not included 124151-5038-WOthen the substrate 220 (e.g., copper) may not bond to the substrate 222 (e.g., silicon). In some embodiments, the bonding layer 224 is composed of a photo-imageable material. For example, imaging the bonding layer 224 may provide definition of the microfluidic channel 102, such as its width, height, and curvature. In some embodiments, the bonding layer 224 is adapted and / or positioned to provide stress relief for the substrate 220 and / or the substrate 222 (e.g., to prevent stress cracking when the chip is assembled in a package). In some embodiments, the bonding layer 224 is cured / hardened (e.g., submitted to multiple stages of curing / hardening). In some embodiments, the bonding layer 224 is submitted to a temperature that exceeds a transition temperature (e.g., 150° C) for the bonding layer, whereby the bonding layer cures and bonds the substrate 220 to the substrate 222. In some embodiments, the bonding layer 224 is composed of a liquid or a dry film. The bonding layer 224 may be a negative or positive photo- resist. In some embodiments, the bonding layer 224 is composed of an epoxy (e.g., bisphenol- A) and / or polyimides with photo initiators (e.g., added to drive cross linking based on the wavelength of light).

[0048] In some embodiments, each magnet component 202 includes one or more magnetic layers. In some embodiments, a magnet component 202 (e.g., the magnet component 202-1) includes a permanent magnet (e.g., a permanent magnet core). In some embodiments, a magnet component 202 (e.g., the magnet component 202-2) comprises an electromagnet (e.g., a magnetic core with one or more coils configured to provide an electrical current). In some embodiments, the magnet components 202 consist of a single magnet component that at least partially encircles the microfluidic channel 102. In some embodiments, the magnet components 202 comprise two components arranged on opposite sides of the microfluidic channel 102. In some embodiments, each magnet component 202 is arranged at a same distance from the microfluidic channel 102. In some embodiments, the magnet components 202 are arranged at differing distances from the microfluidic channel 102.

[0049] Figure 2B shows the micro-cooling device 200 further including a shielding layer 226 adjacent to the magnet component 202-1. In some embodiments, each magnet component 202 is coupled to a respective shielding layer 226. In some embodiments, one or more shielding layers 226 are arranged to separate the magnet components 202 from a heat-generating component coupled at the thermal-coupling portion 110. In some embodiments, one or more shielding layers 226 are arranged to separate the magnet components 202 from electronic components around the micro-cooling device 200 (e.g., including a heat-generating 124151-5038-WOcomponent). In some embodiments, the shielding layer 226 is composed of one or more metal layers. For example, the shielding layer 226 may be composed of aluminum and / or a mu-metal (e.g., nickel, iron, copper, chromium, molybdenum, and / or other type of metal). In some embodiments, the shielding layer 226 is composed of one or more aluminum layers and a mu- metal layer (e.g., the mu-metal layer positioned between two aluminum layers). In some embodiments, each layer may have a thickness in the range of 10 m to 40 m (e.g., 20 m). In some embodiments, a mu-metal layer has a thickness in the range of 100 m to 300 m (e.g., 200 m).

[0050] Figure 2C illustrates a side view along the b to b axis of the micro-cooling device200 of Figure 2A in accordance with some embodiments. Figure 2C shows the micro-cooling device 200 including the microfluidic channel 102 enclosed by a substrate 250, a substrate 252, and the bonding layer 224. In some embodiments, the substrate 250 is the same as the substrate 220 (e.g., the substrate 250 is a different portion of a same substrate as the substrate 220). In some embodiments, the substrate 252 is the same as the substrate 222 (e.g., the substrate 252 is a different portion of a same substrate as the substrate 222). In accordance with some embodiments, the substrate 250 corresponds to the thermal-coupling portion 110. In some embodiments, the substrate 250 is composed of a thermally-conductive material (e.g., copper or aluminum).

[0051] In accordance with some embodiments, the substrate 250 is coupled with a heat- generating component 256 via an interface 254. In some embodiments, the substrate 250 is connected to the heat-generating component 256 (e.g., without the interface 254). In some embodiments, the interface 254 comprises a thermally-conductive material (e.g., a thermal paste). In some embodiments, the heat-generating component 256 is coupled to a substrate 260 (e.g., a printed circuit board (PCB)).

[0052] Figure 2D illustrates a side view of a micro-cooling device 280 in accordance with some embodiments. The micro-cooling device 280 is similar to the micro-cooling device 200, but has a vertical fluidic loop arrangement. In accordance with some embodiments, the micro- cooling device 280 includes the microfluidic channel 102 defined in the substrate 250. In Figure 2D, an interior of the microfluidic channel loop is filled with a substrate 282. In some embodiments, the substrate 282 is the same as the substrate 250. In some embodiments, the substrate 282 is composed of a different material than the substrate 250. In some embodiments, the substrate 250 includes two or more layers of distinct materials. In accordance with some 124151-5038-WOembodiments, a heat-generating component 256 is coupled to a top side of the substrate 250. In various embodiments, the heat-generating component 256 may be coupled to the micro- cooling device 280 at different locations. The micro-cooling device 280 includes flow-control elements 284-1 and 284-2. In some embodiments, the flow-control elements 284 are the same as the flow-control elements 104. In some embodiments, the flow-control elements 284 comprise a set of piezoelectric actuators. For example, the flow-control elements 284 may be configured to generate oscillations that create displacement as well as acoustic waves which causes mixing and disassociation of particles in the microfluidic channel 102 and / or controls localized inertial movement of the particles, e.g., to induce a laminar flow in the microfluidic channel 102. The micro-cooling device 280 includes a magnet component 290. In some embodiments, the magnet component 290 is the same as the magnet component 202. For example, the magnet component 290 may comprise a permanent magnet and / or an electromagnet. In some embodiments, the magnet component 290 is configured to generate an electromagnetic field across the microfluidic channel 102 (e.g., an oscillating electromagnetic field).

[0053] Figure 2E illustrates a plane view of a micro-cooling device 297 in accordance with some embodiments. The micro-cooling device 297 is similar to the micro-cooling device 200, except that in the micro-cooling device 297, the magnetic particles 204 are contained within a reservoir 299. The reservoir 299 (also sometimes referred to as a bath) is positioned in proximity with the magnet component(s) 202 such that a magnetic field produced by the magnet component(s) 202 affects the magnetic particles 204 in the reservoir 299. The reservoir 299 is thermally coupled to the microfluidic channel 102 (e.g., is fluidically coupled to the microfluidic channel 102). In accordance with some embodiments, the magnet component(s) 202 are configured to generate an AC field that causes the magnetic particles 204 to align in alternating directions (in accordance with the rising and falling portions of AC field) which converts heat to magnetic entropy. For example, the magnetic particles 204 absorb heat from the fluid flowing through the microfluidic channel 102 to be converted to magnetic entropy. In this way, the fluid is cooled as it flows past the reservoir 299. In some embodiments, the reservoir 299 is separated from the microfluidic channel 102 by a grate or other physical barrier adapted to prevent the magnetic particles 204 from leaving the reservoir 299. In some embodiments, the magnetic particles 204 are affixed to the reservoir 299. In some 124151-5038-WOembodiments, the magnetic particles 204 are sized to prevent the magnetic particles 204 from leaving the reservoir 299 (e.g., are too large to flow through the microfluidic channel 102).

[0054] Figure 3A illustrates a magnet component 300 in accordance with some embodiments. In some embodiments, the magnet component 300 is an instance of the magnet component 202 or the magnet component 290. The magnet component 300 includes a magnetic core 302 (e.g., composed of a magnetic material) and a coil 304 (e.g., a copper wire or trace line). In accordance with some embodiments, the magnet component 300 includes magnetic shielding layers 310 (e.g., at least partially enclosing the magnetic core 302). In some embodiments, the magnetic core 302 has a thickness (diameter) in the range of 100 m to 400 m (e.g., 300 m). In some embodiments, the magnetic shielding layers 310 are the same as the shielding layer 226. In some embodiments, each magnetic shielding layer 310 (e.g., the magnetic shielding layer 310-1) comprises a plurality of layers (e.g., including one or more mu-metal layers). In the example of Figure 3A, the coil 304 is coupled to a power source 312 (e.g., a current source). In some embodiments, the power source 312 is configured to generate an alternating current (AC). In some embodiments, the power source 312 comprises a piezoelectric actuator coupled to an air flow (e.g., an exhaust air flow for a system in which the power source 312 is attached).

[0055] Figure 3B illustrates an example magnet components configuration in accordance with some embodiments. In the example of Figure 3B, magnet components 300 are arranged on opposite sides of the microfluidic channel 102. The magnet components 300 generate an electromagnetic field 320 across the microfluidic channel 102. The magnetic particles 204 within the microfluidic channel 102 are aligned (e.g., polarized and / or spin aligned) via the electromagnetic field 320. In some embodiments, the electromagnetic field 320 is configured to convert heat energy of the magnetic particles into magnetic entropy (e.g., by alternating directions of magnetic moments of the magnetic particles). In this way, heat absorbed by the magnetic particles (from a heat-generating component coupled to the microfluidic channel 102) is converted adiabatically to magnetic entropy, thereby allowing the temperature of the magnetic particles to reduce (and subsequently absorb more heat from the heat-generating component as the particles are recirculated in the microfluidic channel 102).

[0056] For example, as the AC field pulses, the magnetic particles align in a first direction (e.g., the direction of the magnetic field vector during a rising edge) then a second direction (e.g., the direction of the magnetic field vector during a fall edge). This realignment process 124151-5038-WOincreases the magnetic entropy of the magnetic particles and reduces lattice entropy (e.g., heat). Once the magnetic particles leave the magnetic field area, the magnetic entropy decreases and the lattice entropy increases (e.g., as the magnetic particles absorb heat from the environment (e.g., the fluid and / or the heat-generating component).

[0057] In some embodiments, the electromagnetic field 320 is adapted based on attributes of the magnetic particles 204 and / or the flow rate of the fluid in the microfluidic channel. For example, the frequency / period of the electromagnetic field 320 may vary with the flow rate of the fluid. In some embodiments, the frequency and / or duty cycle of the electromagnetic field 320 is adjusted based on the type of magnetic particles. For example, the electromagnetic field 320 may be adjusted to align the magnetic particles in alternating directions at a rate that maximizes the magnetic moments of the magnetic particles.

[0058] Figure 3C illustrates a magnet component 340 in accordance with some embodiments. In some embodiments, the magnet component 340 is an instance of the magnet component 202 or the magnet component 290. The magnet component 340 includes the magnetic core 302 (e.g., in a ring shape) and the coils 304-1 and 304-2. In the example of Figure 3C, each of the coils 304 is coupled to a respective power source 312. In some embodiments, the coils 304 are coupled to a same power source 312 (e.g., via respective phase shifters and / or delay elements). In the example of Figure 3C, the magnetic core 302 encircles the microfluidic channel 102. In some embodiments, the magnetic core 302 has a different shape (e.g., an oblong, rectangular, or non-geometric shape) that at least partially encircles the microfluidic channel 102 (e.g., encircling three of the four sides of the microfluidic channel). In some embodiments, the microfluidic channel 102 has a non-rectangular shape (e.g., an oval shape, rounded shape, or non-geometric shape).

[0059] Figure 3D illustrates a magnet component 360 in accordance with some embodiments. The magnetic component 360 is composed of a plurality of core layers 352 (e.g., composed of a ferrite material). As illustrated in Figure 3D, each of the core layers 352 may include a portion of coils 356. The different portions of the coils 356 may be connected to one another using conductive vias. For example, the coil portion 356-2 is connected to the coil portion 356-3 using the via 358. In some embodiments, the core layers 352 are composed of a flexible material (e.g., that may deform along with a substrate or component to which the magnet component 360 is attached). The magnet component 360 includes terminals 354-1 and 124151-5038-WO354-2 at opposite ends of the coils 356 (e.g., that allow the magnetic component 360 to be coupled to a power source 312).

[0060] Figures 3E-3F illustrate example magnet configurations in accordance with some embodiments. Figure 3E shows an example configuration in which the magnetic particles 204 are contained within the reservoir 299. In the example of Figure 3E, the magnet components 300-1 and 300-2 are adjacent to the reservoir 299 and configured to generate an AC field to control the spins of the magnetic particles 204. In some embodiments, the magnetic particles 204 are retained in a particular portion of the microfluidic channel 102 (e.g., without the reservoir 299). In some embodiments, the magnetic particles 204 are adjacent to the microfluidic channel 102 (e.g., and fluidically coupled to the microfluidic channel 102). Figure 3F shows an example configuration in which the magnet component 300 is positioned in, or adjacent to, the microfluidic channel 102. In the example of Figure 3F, the magnetic particles 204 are sized such that the magnetic particles 204 cannot flow through the microfluidic channel 102 (e.g., are too large to leave the vicinity of the magnet component 300). In some embodiments, the portion of the microfluidic channel 102 around the magnet component 300 is wider than other portions of the microfluidic channel 102 (e.g., such that the magnetic particles 204 fit within the portion of the microfluidic channel 102 around the magnet component 300 but not the other portions of the microfluidic channel 102).

[0061] Figure 4A illustrates a micro-cooling system 400 in accordance with some embodiments. The micro-cooling system 400 includes a plurality of micro-cooling devices 404 attached to a heat-generating component 402. The micro-cooling devices 404 may be instances of any of the micro-cooling devices described herein (e.g., the micro-cooling device 150 or the micro-cooling device 280). As shown in Figure 4A, each micro-cooling device 404 has a respective microfluidic channel 102. In the example of Figure 4A, each of the micro-cooling devices 404 is coupled to a respective flow-control element 406. The flow-control elements 406 may be instance of any of the flow-control elements 406 described herein (e.g., the flow- control elements 104). In accordance with some embodiments, the flow-control elements 406 are coupled to control circuitry 412 (e.g., a micro-controller, a controller, and / or other types of control circuitry). In some embodiments, each of the flow-control elements 406 includes a split and an actuator configured to selectively direct flow of a fluid in the microfluidic channel 102 to one branch or another of the split. For example, the flow-control elements 406 may be configured to selectively direct flow of a fluid in the microfluidic channel 102 to a subset of 124151-5038-WOthe micro-cooling devices 404 at any given time (e.g., based on temperature information for the heat-generating component 402). In accordance with some embodiments, a magnet component 410 is coupled to a portion 102-4 of the microfluidic channel 102. The magnet component 410 may be an instance of any of the magnet components described herein (e.g., the magnet components 202, 290, 300, 340, or 360).

[0062] Figures 4B-4C illustrate example operation of the micro-cooling system 400 of Figure 4A in accordance with some embodiments. In Figure 4B, a hot spot 450-1 is present in the heat-generating component 402 at a location corresponding to the micro-cooling device 404-2. In accordance with detecting the hot spot 450-1 (e.g., using one or more temperature sensors) the control circuitry 412 in Figure 4B directs flow of the fluid within the microfluidic channel 102 to the micro-cooling device 404-2 using the flow-control element 406-2. In Figure 4C, a hot spot 450-2 is present in the heat-generating component 402 at a location corresponding to the micro-cooling device 404-1. In accordance with detecting the hot spot 450-2 (e.g., using one or more temperature sensors) the control circuitry 412 in Figure 4C directs flow of the fluid within the microfluidic channel 102 to the micro-cooling device 404- 1 using the flow-control element 406-1. In this way, the micro-cooling system 400 may direct cooling to the hot (e.g., hottest) portions of the heat-generating component 402. In some embodiments, the heat-generating component has multiple hot spots 450 and the control circuitry 412 directs flow to multiple micro-cooling devices 404 simultaneously. In some embodiments, the control circuitry 412 receives temperature information from the heat- generating component 402 and adjusts operation based on the received temperature information. In some embodiments, the control circuitry 412 receives temperature information from one or more temperature sensors of the micro-cooling system 400 (and / or one or more temperature sensors communicatively coupled to the micro-cooling system 400) and adjusts operation based on the received temperature information. In some embodiments, a flow rate of the micro-cooling system 400 is adjusted (e.g., using the flow-control elements 406) based on a location and / or temperature of a hot spot 450. For example, a hot spot in a first location may require more rapid cooling than a hot spot in a second location.

[0063] Figure 4D illustrates a micro-cooling system 478 in accordance with some embodiments. The micro-cooling system 478 includes multiple micro-cooling devices 482 arranged in a stacked formation with multiple heat-generating components 480 (e.g., a Manhattan structure). The micro-cooling devices 482 may be instances of any of the micro- 124151-5038-WOcooling devices described herein. As shown in Figure 4D, heat 494 transfers (494-1) from a heat-generating component 480-1 to the micro-cooling device 482-1. In the example of Figure 4D, heat may transfer from the heat-generating component 480-2 to the micro-cooling device 482-1 (as illustrated by heat transfer 494-2) and / or the micro-cooling device 482-2 (as illustrated by heat transfer 494-3). Additionally, heat transfers (494-4) from the heat-generating component 480-3 to the micro-cooling device 482-2. In accordance with some embodiments, the micro-cooling devices 482 are thermally coupled to one another via a thermal-coupling component 496 (e.g., a set of one or more thermal vias). The thermal-coupling component 496 allows for heat transfer between micro-cooling devices 482 (e.g., can be used to allow multiple micro-cooling devices 482 to convert heat from a particular component to magnetic entropy). In accordance with some embodiments, each of the micro-cooling devices 482 includes a respective magnet component of the magnet components 498. The magnet components 498 may comprise instances of any of the magnet components described herein (e.g., the magnet component 300). In accordance with some embodiments, the magnet components 498 are electrically coupled to control circuitry 499 (e.g., comprising a magnet controller). In some embodiments, the control circuitry 499 is configured to selectively activate (e.g., provide power to) respective ones of the magnet components 498. For example, the control circuitry 499 may activate subsets of the magnet components 498 according to respective temperatures of the heat-generating components. As an example, if a temperature of a particular heat-generating component is below a threshold temperature value, the adjacent micro-cooling devices may be deactivated (e.g., power may not be supplied to the magnet component and / or flow control elements of the micro-cooling devices). In some embodiments, the micro-cooling devices may be activated to assist with cooling non-adjacent heat-generating components (e.g., using the thermal-coupling component 496). In some embodiments, the stacked formation shown in Figure 4D is combined with the array arrangement shown in Figure 4C (e.g., forming a three- dimensional array of micro-cooling devices).

[0064] Figure 5 illustrates an example micro-cooling arrangement in accordance with some embodiments. In the example of Figure 5, micro-cooling devices 502 are arranged in a two- dimensional array and attached to a heat-generating component 500. The micro-cooling devices 502 may be instances of any of the micro-cooling devices described herein (e.g., the micro-cooling devices 404). In the example of Figure 5, the micro-cooling devices are arranged in a 4x4 grid (e.g., comprising 16 micro-cooling devices). In other embodiments, the micro- 124151-5038-WOcooling devices are arranged in other grid patterns (e.g., shaped and / or sized based on a size of a heat-generating component to which the micro-cooling array is configured to attach). In some embodiments, the micro-cooling devices are fluidically coupled to one another. In some embodiments, the micro-cooling devices are not fluidically coupled, but are controlled by a same controller (or control circuitry).

[0065] Figures 6A-6B illustrate an example micro-cooling power source in accordance with some embodiments. Figure 6A shows a power source 608 coupled to a micro-cooling device 502. In some embodiments, the power source 608 is a component of the micro-cooling device 502. In some embodiments, the power source 608 is a component of a micro-cooling system that includes the micro-cooling device 502. The micro-cooling device 502 in Figure 6A includes one or more electromagnets 602 and one or more flow-control elements 604 that may be powered by the power source 608. In some embodiments, the power source 608 is configured to provide differing power levels (e.g., differing currents) to the different components of the micro-cooling device 502. In some embodiments, the power source 608 is coupled to multiple micro-cooling devices (e.g., is configured and coupled to power multiple flow-control elements). The power source 608 may include one or more actuators and one or more power converter components (e.g., current dividers, inverters, level shifters, and / or other frequency and / or magnitude adjustment components). In some embodiments, the one or more actuators comprise one or more piezoelectric actuators. In some embodiments, a piezoelectric actuator has a torus shape or a ring shape.

[0066] Figure 6B illustrates example components of the power source 608. In Figure 6B, the power source 608 includes a jet air component 610. In some embodiments, the jet air component 610 is coupled to a fan, an exhaust, or air flow component of a system in which the power source 608 is attached. The jet air component 610 includes an intake portion 611 with an intake comb structure 620, a channel portion with an input valve 612-1 and an output value 612-2, and an output portion 613. In some embodiments, the input value 612-1 comprises a piezoelectric valve. In some embodiments, the output valve 612-2 comprises a piezoelectric value. In accordance with some embodiments, the channel portion is narrower than the intake portion 611 and the output portion 613. The channel portion between the valves 612 includes a piezoelectric actuator 614. In some embodiments, the piezoelectric actuator 614 comprises a piezoelectric material on a membrane structure. In some embodiments, the piezoelectric 124151-5038-WOactuator 614 has a torus or ring shape with an aperture in the middle for jet air to flow through. In some embodiments, the jet air component 610 includes a plurality of piezoelectric actuators.

[0067] Figure 7 illustrates a micro-cooling system 700 in accordance with some embodiments. The micro-cooling system 700 may be an instance of any of the micro-cooling systems described herein (e.g., the micro-cooling system 400). The micro-cooling system 700 includes control circuitry 704, memory 702, sensor(s) 706, and micro-cooling device(s) 720. In some embodiments, the micro-cooling device(s) 720 are instances of any of the micro- cooling devices described herein. In accordance with some embodiments, the sensor(s) 706 include one or more temperature sensors 708 and one or more flow rate sensors 710. In some embodiments, the sensor(s) 706 include a subset of these sensors (e.g., does not include the flow rate sensors 710 or the temperature sensors 708). In some embodiments, the sensor(s) 706 include one or more additional types of sensors (e.g., pressure sensors, orientation sensors, current sensors, and / or other types of sensors). In the example of Figure 7, the control circuitry 704 includes one or more processor(s) 712 (e.g., microprocessors, CPUs, and / or other types of processors), a flow rate controller 714, a current rate controller 716, and a temperature controller 718. In some embodiments, the control circuitry 704 includes a subset of these components (e.g., includes a single controller that controls both flow rate and current rate). In some embodiments, the current rate controller 716 is configured to govern operation of an electromagnet (e.g., the electromagnet(s) 724). In some embodiments, the current rate controller 716 (also sometimes referred to a magnetic field controller or magnet controller) is configured to adjust a frequency and / or duty cycle of an AC field generated by the electromagnet based on a flow rate of a fluid in the corresponding microfluidic channel and / or properties of the magnetic particles in the microfluidic channel. In some embodiments, the control circuitry 704 includes one or more components not shown in Figure 7 (e.g., one or more drivers). The micro-cooling device(s) 720 in Figure 7 include flow-control element(s) 722, electromagnet(s) 724, and microfluidic channel 726. The flow-control element(s) 722 may be an instance of any of the flow-control elements described herein. The electromagnet(s) 724 may be an instance of any of the magnet components described herein. The microfluidic channel 726 may be an instance of any of the microfluidic channels described herein. In accordance with some embodiments, the micro-cooling device(s) 720 are coupled (e.g., thermally coupled) to one or more heat-generating components 742. In some embodiments, two or more micro-cooling device(s) 720 are coupled to a same heat-generating component. In 124151-5038-WOsome embodiments, a single micro-cooling device 720 is coupled to two or more heat- generating components. In the example of Figure 7, the micro-cooling system 700 (e.g., the control circuitry 704) is coupled to one or more external power sources 740. In some embodiments, the micro-cooling system 700 includes one or more power sources (e.g., the power source 608). In some embodiments, the components of the micro-cooling system 700 are electrically coupled to one another via one or more interconnects 730. In some embodiments, the interconnect(s) 730 comprise one or more wires, leads, traces, or other types of electrical paths. In accordance with some embodiments, the micro-cooling system 700 includes magnetic shielding 721 at least partially (e.g., fully) enclosing the micro-cooling device(s) 720. The magnetic shielding 721 may comprise any of the shielding layers described herein (e.g., the magnetic shielding layers 310). In some embodiments, the magnetic shielding 721 is configured and arranged to shield electronics (e.g., the control circuitry 704 and / or the heat-generating component(s) 742) from electromagnetic interference caused by the electromagnet(s) 724. In some embodiments, the magnetic shielding 721 is composed of one or more metal layers (e.g., aluminum layers) and one or more mu-metal layers.

[0068] The memory 702 may include high-speed random-access memory (such as DRAM, SRAM, DDR RAM, and / or other random access solid-state memory devices) and / or non- volatile memory (such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, and / or other non-volatile solid-state storage devices). The memory 702 optionally includes one or more storage devices remotely located from the control circuitry 704. In some embodiments, the memory 702 includes one or more buffers, flipflops, and / or other storage elements. The memory 702, or, alternatively, the non-volatile solid-state memory device(s) within the memory 702, includes a non-transitory computer-readable storage medium. In some embodiments, the memory 702, or the non-transitory computer-readable storage medium of the memory 702, stores programs, modules, instructions, and data structures for the control circuitry 704.

[0069] In some embodiments, the micro-cooling systems described herein (e.g., the micro- cooling system 700) are constructed by constructing a microfluidic device (e.g., a micro- cooling device described herein). Constructing the microfluidic device includes obtaining a first substrate (e.g., the substrate 220) comprising a thermally-conductive material, defining a closed microfluidic system comprising a microfluidic channel (e.g., the microfluidic channel 102) by attaching a second substrate (e.g., the substrate 222) to the first substrate, and providing 124151-5038-WOa fluid to the microfluidic channel. In some embodiments, the second substrate is attached to the first substrate using a bonding layer. In some embodiments, the fluid comprises a plurality of magnetic particles.

[0070] In some embodiments, constructing the micro-cooling system includes attaching a set of magnets to at least one of the first substrate and the second substrate, where the set of magnets are configured to apply a magnetic field to the microfluidic channel. In some embodiments, constructing the micro-cooling system includes applying one or more magnetic shielding layers to the set of magnets. For example, the magnetic shielding layer(s) may be deposited, adhered, grown, or otherwise applied to the set of magnets.

[0071] In some embodiments, the fluid is provided after attaching the second substrate to the first substrate. For example, the fluid is provided via an injection port that may be sealed after the fluid is inserted. In some embodiments, the fluid is provided before attaching the second substrate to the first substrate.

[0072] In some embodiments, constructing the micro-cooling system includes attaching the microfluidic device to a system substrate, and attaching one or more additional microfluidic devices to the system substrate. In some embodiments, the system substrate is composed of glass, silicon, and / or other materials (e.g., dielectric materials). In some embodiments, attaching the microfluidic device comprises embedding the microfluidic device in the system substrate. In some embodiments, the system substrate is configured to couple one or more heat- generating components (e.g., any type of heat-generating component described herein).

[0073] In some embodiments, constructing the micro-cooling system includes obtaining a stack of microfluidic devices by thermally coupling one or more additional microfluidic devices to the microfluidic device (e.g., such that multiple microfluidic devices may work in concert to remove heat from a single heat-generating component). In some embodiments, the first and second substrates are each composed of a thermally-conductive material (e.g., copper or aluminum). In some embodiments, the stack of microfluidic devices is configured to transfer heat between the respective microfluidic devices so as to transfer the heat away from the heat- generating component. In some embodiments, the stack of microfluidic devices are attached (e.g., embedded in) a system substrate. In some embodiments, the stack of microfluidic devices are enclosed in a cover layer (e.g., a dielectric material such as glass or silicon). In some embodiments, the stack of microfluidic devices are configured to transfer heat at respective first portions (e.g., that are coupled via thermally-conductive materials) and not transfer heat 124151-5038-WOat respective second portions (e.g., that are coupled via thermally-insulating materials). In some embodiments, the stack of microfluidic devices comprises a stack of three or more microfluidic devices. In some embodiments, the thermally-conductive materials are coupled to a wideband gap material that is tuned to absorb a far infrared (e.g., from 3-10 m) part of the spectrum. In some embodiments, the stack of microfluidic devices comprises one or more interposing layers between respective microfluidic devices. As an example, the stack of microfluidic devices may form a Manhattan structure (e.g., as illustrated in Figure 4D).

[0074] Figures 8A-8B are flow diagrams illustrating example methods for providing cooling in accordance with some embodiments. Figure 8A is a flow diagram illustrating a method 800 for operating a micro-cooling device in accordance with some embodiments.

[0075] The method 800 includes attaching (802) a micro-cooling device to a heat- generating component at a first portion, where the micro-cooling device comprises a fluid within a microfluidic channel. In various embodiments, the micro-cooling device includes any of the features described herein. For example, Figure 2D shows the micro-cooling device 280 attached to the heat-generating component 256. In some embodiments, the method comprises causing the fluid to recirculate between the first portion and the second portion of the microfluidic channel.

[0076] In some embodiments, the method 800 includes aligning (804) spins of a plurality of magnetic particles (e.g., the magnetic particles 204) within the fluid using a set of one or more electromagnets (e.g., the magnet components 202) adjacent to the second portion of the microfluidic channel. In some embodiments, electrical power is provided to the set of electromagnets by a piezoelectric actuator (e.g., the piezoelectric actuator 614). In some embodiments, the plurality of magnetic particles comprises a plurality of magnetic dipole particles, and aligning spins of the plurality of magnetic particles comprises aligning dipoles of the plurality of magnetic dipole particles according to an electromagnetic field generated by the set of one or more electromagnets. For example, the dipoles may be aligned with a rising or falling electromagnetic field. In some embodiments, the frequency of the magnetic field is in the range of 50 Hertz to 1,000 Hertz.

[0077] The method 800 includes causing (806) the fluid to flow through the microfluidic channel from a second portion of the microfluidic channel toward the heat-generating component, whereby heat from the heat-generating component transfers to the fluid within the microfluidic channel. 124151-5038-WO

[0078] In some embodiments, the method 800 includes providing (808) electrical power to the one or more flow-control elements to cause the one or more flow-control elements to displace the fluid contained within the microfluidic channel. In some embodiments, the electrical power is provided by a piezoelectric actuator. In some embodiments, the one or more flow-control elements comprise one or more piezoelectric actuators.

[0079] In some embodiments, the method further comprises identifying one or more hot spots for the heat-generating component, wherein causing the fluid to flow through the microfluidic channel comprises causing the fluid to flow toward the one or more hot spots. In some embodiments, the micro-cooling device comprises a plurality of microfluidic channels, and causing the fluid to flow toward the one or more hot spots comprises directing the flow to the microfluidic channel(s) that are most proximate to the hot spots. In some embodiments, the hot spots are identified using control circuitry of the micro-cooling device.

[0080] In some embodiments, the method further comprises (i) determining one or more target temperatures for the heat-generating component; and (ii) adjusting a flow rate of the fluid according to a comparison between one or more actual temperatures of the heat-generating component and the one or more target temperatures. In some embodiments, adjusting the flow rate comprises adjusting a duty cycle of a flow-control element (e.g., a piezoelectric actuator). In some embodiments, the target temperature(s) are obtained from the heat-generating component. In some embodiments, the target temperature(s) are stored at the micro-cooling device (e.g., are obtained during manufacturing and / or during a setup procedure for the micro- cooling device). In some embodiments, the target temperature(s) are obtained during an initialization or start-up procedure for the heat-generating component and / or the micro-cooling device.

[0081] Figure 8B is a flow diagram illustrating a method 900 for operating a micro-cooling system (e.g., the micro-cooling system 700) in accordance with some embodiments.

[0082] The method 900 includes attaching (902) a micro-cooling system to a heat- generating component, where the micro-cooling system comprises a set of micro-cooling devices having a microfluidic channel with a fluid contained within. In some embodiments, the fluid comprises a plurality of magnetic particles and a solvent.

[0083] The method 900 includes monitoring (904) a temperature of the heat-generating component. In some embodiments, the temperature of the heat-generating component is monitored using one or more temperature sensors of the micro-cooling system. In some 124151-5038-WOembodiments, monitoring the temperature of the heat-generating component comprises identifying one or more hot spots on the heat-generating component.

[0084] The method 900 includes providing (906) cooling, based on the monitored temperature, to the heat-generating component by causing the fluid to flow through the microfluidic channel.

[0085] In some embodiments, the method 900 includes adjusting (908) a flow of the fluid through the microfluidic channel using a set of piezoelectric actuators.

[0086] In some embodiments, the method further comprises providing electrical power to the set of piezoelectric actuators using a second piezoelectric actuator. In some embodiments, the method further comprises applying a magnetic field to the plurality of magnetic particles to align spins of the plurality of magnetic particles.

[0087] Although Figures 8A and 8B illustrate a number of logical stages in a particular order, stages which are not order dependent may be reordered and other stages may be combined or broken out. Some reordering or other groupings not specifically mentioned will be apparent to those of ordinary skill in the art, so the ordering and groupings presented herein are not exhaustive. Moreover, it should be recognized that the stages could be implemented in hardware, firmware, software, or any combination thereof.

[0088] In light of the above disclosure, certain embodiments are described below.

[0089] (A1) In one aspect, some embodiments include a micro-cooling device (e.g., the micro-cooling device 200) comprising: (i) a first substrate (e.g., the substrate 220); (ii) a second substrate (e.g., the substrate 222) coupled to the first substrate; (iii) a microfluidic channel (e.g., the microfluidic channel 102) formed between the first substrate and the second substrate; (iv) a fluid contained within the microfluidic channel; and (v) a set of one or more piezoelectric actuators (e.g., the flow-control elements 104) positioned adjacent to the microfluidic channel and configured to govern flow of the fluid within the microfluidic channel. In some embodiments, the second substrate is composed of a dielectric material (e.g., silicon, silicon- on-insulator, glass, or other dielectric materials). In some embodiments, the microfluidic channel comprises a closed fluidic loop in which the fluid contained within is recirculated. In some embodiments, the fluid comprises a gaseous and / or liquid fluid. In some embodiments, the microfluidic channel is at least partially filled with air and / or other gas.

[0090] In some embodiments, the set of one or more piezoelectric actuators (e.g., channel actuators) is fluidly connected to the microfluidic channel. In some embodiments, the set of 124151-5038-WOpiezoelectric actuators is positioned in a chamber that is fluidly coupled to the microfluidic channel (e.g., but not in the main channel of the microfluidic channel). In some embodiments, the set of piezoelectric actuators is positioned adjacent to the microfluidic channel (e.g., on adjacent or opposite sides). In some embodiments, the set of piezoelectric actuators is positioned to be lateral to the microfluidic channel during use (e.g., perpendicular to a direction of gravity). In some embodiments, the set of piezoelectric actuators comprises a piezoelectric membrane (e.g., having a circular or oblong shape). In some embodiments, the set of piezoelectric actuators comprises one or more microelectromechanical system (MEMS) membranes. In some embodiments, the one or more MEMS membranes are coupled to (or components of) the first substrate and / or the second substrate.

[0091] (A2) In some embodiments of A1, the first substrate is composed of a thermally- conductive material. In some embodiments, the thermally-conductive material comprises a metal (e.g., copper, silver, gold, and / or aluminum), a metal alloy, a ceramic (e.g., aluminum nitride and / or silicon carbide), or other type of thermally-conductive material. In some embodiments, the first substrate is thermally conductive and electrically insulating (e.g., copper, black copper and wide band gap material that can absorb far infrared heat efficiently like perovskite, graphite or carbide).

[0092] (A3) In some embodiments of A1 or A2, the micro-cooling device further comprising a bonding layer (e.g., the bonding layer 224) connecting the first substrate and the second substrate to define the microfluidic channel. In some embodiments, the bonding layer is adapted and positioned to adhere the first substrate portion to the second substrate portion. In some embodiments, the bonding layer is a polymer. In some embodiments, the bonding layer is composed of a photo-imageable material. In some embodiments, the bonding layer is cured / hardened.

[0093] (A4) In some embodiments of any of A1-A3, the fluid comprises at least one of water, glycol, and ethanol. In some embodiments, the fluid comprises a solvent (e.g., an organic solvent). In some embodiments, the fluid is composed of one or more alcohols. In some embodiments, the fluid comprises a gas (e.g., a gas and liquid mixture). In some embodiments, the microfluidic channel is at least partially filled with air, gas, and / or liquid (e.g., such that the fluid can circulate within the channel).

[0094] (A5) In some embodiments of any of A1-A4, the fluid comprises a plurality of magnetic particles (e.g., the magnetic particles 204). For example, the plurality of magnetic 124151-5038-WOparticles (e.g., magnetic beads) are composed of a high magnetic moment material (e.g., in the range of 100-250 emu / g) with a high magnetic transition temperature (e.g., 10-20° C, or greater) under a magnetic field. As an example, the plurality of magnetic particles may comprise a plurality of spherical beads. In some embodiments, the magnetic particles have a non-spherical shape (e.g., an oblong or irregular shape) with a largest diameter in the range of 0.1 mm to 1 mm. In some embodiments, the plurality of magnetic particles have a rounded shape (e.g., to promote flow through the microfluidic channel). In some embodiments, the plurality of magnetic particles is configured to undergo a thermal change of at least 10 Kelvin as the spins switch between aligned and free (misaligned).

[0095] (A6) In some embodiments of A5, the plurality of magnetic particles comprises a plurality of magnetic dipole particles.

[0096] (A7) In some embodiments of A5 or A6, the micro-cooling device further comprising an electromagnet (e.g., the magnet component 202) comprising a winding coil wound around a core, the electromagnet arranged adjacent to the microfluidic channel and configured to apply a magnetic field to spin align the plurality of magnetic particles. In some embodiments, the electromagnet is connected to the at least one of the first substrate and the second substrate. In some embodiments, a set of electromagnets is arranged on opposite sides of the microfluidic channel. In some embodiments, the set of electromagnets include a first electromagnet arranged on a top side of the microfluidic channel and a second electromagnet arranged on a bottom side of the microfluidic channel during use of the micro-cooling device (e.g., with respect to a direction of gravity). In some embodiments, the set of electromagnets are configured to polarize the plurality of magnetic particles. In some embodiments, the set of electromagnets are configured to align dipoles of the plurality of magnetic dipole particles. In some embodiments, a set of magnets (e.g., comprising electromagnets and / or permanent magnets) arranged adjacent to the microfluidic channel and configured to apply a magnetic field to spin align the plurality of magnetic particles.

[0097] In some embodiments, a set of magnets apply the magnetic field to the plurality of magnetic particles at a first portion, and heat from a heat-generating component is transferred to the plurality of magnetic particles at the second portion. In some embodiments, the first portion is configured to remove heat from the plurality of magnetic particles (e.g., as their spins are aligned by the set of magnets), and the second portion is configured to transfer heat from the heat-generating component to the plurality of magnetic particles (e.g., as the spins leave 124151-5038-WOalignment). In some embodiments, the set of magnets apply an oscillating (e.g., pulsating) magnetic field. For example, the magnetic field may be a sine wave, a square wave, or a sawtooth wave.

[0098] In some embodiments, the micro-cooling device comprises a magnetic shielding layer (e.g., the shielding layer 226) coupled to a magnet of the set of magnets. In some embodiments, the magnetic shielding layer is configured / adapted to inhibit or prevent the magnetic field from the set of magnets from interfering with other electronic components such as external electronic components that are in proximity to the microfluidic device (e.g., an electrical component thermally coupled to the first substrate). In some embodiments, the magnetic shielding layer is composed of at least one of aluminum, nickel, iron, copper, and chromium. In some embodiments, the magnetic shielding layer comprises a mu metal layer. In some embodiments, the magnetic shielding layer comprises at least one aluminum layer coupled to at least one mu metal layer. In some embodiments, the magnetic shielding layer is composed of a high magnetic permeability material (e.g., 5,000-20,000 DC permeability).

[0099] (A8) In some embodiments of A7, the magnetic field (e.g., the electromagnetic field 320) is generated by an alternating current (AC) passing through the winding coil wound around the core. In some embodiments, the magnetic field is an AC magnetic field.

[0100] (A9) In some embodiments of A7 or A8, the core comprises one or more magnetic films (e.g., the core layers 352). In some embodiments, electromagnet comprises one or more magnetic layers attached to at least one of the first substrate, the bonding layer, and the second substrate. In some embodiments, each magnetic film has a thickness in the range of 0.1 mm to 1 mm. In some embodiments, each magnetic film of the one or mor magnetic films has a corresponding magnetic strength in the range of 0.1-1 Tesla.

[0101] (A10) In some embodiments of any of A7-A9, the core comprises one or more permanent magnets. In some embodiments, the one or more permanent magnets are composed of a magnetic material such as ferrite. In some embodiments, the core comprises one or more layers of ferrite (or other magnetic) material.

[0102] (A11) In some embodiments of any of A7-A10, the electromagnet comprises a multilayer inductor. In some embodiments, the electromagnet comprises one or more magnetic layers applied to a flexible substrate. In some embodiments, the flexible substrate comprises a polymer. For example, the flexible substrate may comprise an organic polymer, such as organic polymers like polyethylene terephthalate (PET), polyethylene naphthalate (PEN), 124151-5038-WOpolyethersulphone (PES), polyimide (PI), and polydimethylsiloxane (PDMS). In some embodiments, the set of magnets are configured and / or adapted to stretch more than 0.01 mm (e.g., up to 0.02 mm). In some embodiments, the set of magnets are configured / adapted to bend more than 0.02 mm (e.g., up to 0.04 mm).

[0103] (A12) In some embodiments of any of A7-A11, the electromagnet is at least partially embedded in a bonding layer (e.g., the bonding layer 224) connecting the first substrate and the second substrate.

[0104] (A13) In some embodiments of any of A7-A12, the electromagnet is attached to at least one of the first substrate and the second substrate.

[0105] (A14) In some embodiments of any of A1-A13, the microfluidic channel comprises a closed loop, and the fluid is recirculated within the closed loop. In some embodiments, a plurality of magnetic particles is recirculated within the closed loop. In some embodiments, the closed loop includes a set of electromagnets at a first portion (e.g., to align spins of the plurality of magnetic particles) and a second portion adjacent to a heat-generating component (such that the magnetic particles may absorb heat from the heat-generating component). In some embodiments, the first substrate is configured to couple to a heat-generating component at a first portion, and the set of magnets (e.g., electromagnets) are arranged at a second portion of the first substrate, the second portion being different than the first portion. In some embodiments, the microfluidic channel is arranged as a closed fluidic system, and, during operation of the micro-cooling device, a plurality of magnetic particles flow in a loop between the second portion to the first portion.

[0106] (A15) In some embodiments of any of A1-A14, the first substrate is composed of a first material at the first portion (e.g., copper) and is composed of a different material at the second portion (e.g., silicon). In some embodiments, the second substrate is composed of a first material at the first portion and is composed of a different material at the second portion. In some embodiments, the different materials for the first / second substrates have a thermal impedance match (e.g., to reduce damage from warping / cracking due to temperature changes in the device).

[0107] (A16) In some embodiments of any of A1-A15, the micro-cooling device further comprises a second piezoelectric actuator (e.g., the piezoelectric actuator 614) coupled to the set of one or more piezoelectric actuators, the second piezoelectric actuator configured to provide power to the set of one or more piezoelectric actuators. For example, the second 124151-5038-WOpiezoelectric actuator may be referred to as a master piezoelectric element and the set of piezoelectric actuators may be referred to as a set of slave piezoelectric elements. In some embodiments, the second piezoelectric actuator is not fluidly coupled to the microfluidic channel. For example, the second piezoelectric actuator may be remote from the microfluidic channel, but electrically coupled to the set of piezoelectric actuators via one or more leads, wires, and / or traces. In some embodiments, the second piezoelectric actuator is configured to generate a voltage in a range of -50 volts (V) to 50 V (or -20 V to 20 V, or other similar voltage range). In some embodiments, the second piezoelectric actuator is arranged on a circuit board, chip, or other component that is distinct from the first substrate, the second substrate, and / or the micro-cooling device. In some embodiments, the second piezoelectric actuator is configured to power to one or more electromagnets (e.g., to provide an AC signal for a coil of an electromagnet.

[0108] In some embodiments, the micro-cooling device does not include an energy storage device (e.g., a battery). In some embodiments, the micro-cooling device does not receive power from an outside source (the magnets do not require an energy source and / or flow actuators use energy generated within the device). In some embodiments, the micro-cooling device comprises a microfluidic device, a magnetocaloric cooling device, a liquid cooling device, and / or a refrigeration device (e.g., a micro-magnetic refrigeration device).

[0109] (A17) In some embodiments of A16, the second piezoelectric actuator is coupled to the set of one or more piezoelectric actuators via an electrical circuit (e.g., the control circuitry 704). In some embodiments, the electrical circuit is configured to adjust one or more properties of the output of the second piezoelectric actuator (e.g., adjust a voltage level, a current level, a timing (e.g., a frequency or period), and / or other electrical property) prior to providing power to the set of one or more piezoelectric actuators. In some embodiments, the electrical circuit comprises an energy storage device (e.g., a battery or capacitor) configured to store power from the second piezoelectric actuator. In some embodiments, the electrical circuit comprises one or more conductive layers attached to the first substrate and / or second substrate (e.g., bonded to, deposited on, and / or grown on one of the substrates). In some embodiments, the second piezoelectric actuator is electrically coupled (e.g., electrically connected) to one or more coils of one or more micro-cooling devices.

[0110] (A18) In some embodiments of A16 or A17, the second piezoelectric actuator is couplable to an air flow component and configured to actuate in response to air flow from the 124151-5038-WOair flow component. In some embodiments, the air flow component is an air jet component. In some embodiments, the air flow causes the second piezoelectric actuator to vibrate, which in turn causes generation of electrical current (e.g., which is provided to power the set of piezoelectric actuators).

[0111] For example, the air flow component may comprise a fan used to cool an electronic component that is thermally coupled to the micro-cooling device (e.g., a system fan, a cooling fan, a case fan, or other type of fan). In some embodiments, the second piezoelectric actuator comprises a membrane, e.g., having a torus or doughnut shape. In some embodiments, the air flows through one or more apertures in the second piezoelectric actuator.

[0112] (A19) In some embodiments of A18 the micro-cooling device further comprises the air flow component (e.g., the jet air component 610), where the air flow component comprises an air channel, an inlet, and a first valve configured to regulate air flow from the inlet into an air channel. In some embodiments, the air channel is configured to allow air (e.g., jet vapor) to flow past the second piezoelectric actuator. In some embodiments, the inlet comprises a comb structure. In some embodiments, the first valve comprises a piezoelectric valve. In some embodiments, the second piezoelectric actuator comprises one or more piezoelectric valves. In some embodiments, the metal comb structure of the inlet is immersed in a fluid (e.g., an alcohol or ethanol bath). In some embodiments, the first piezoelectric valve has an orifice in the valve to create a solenoidal swirling pressurized air jet. In some embodiments, the first piezoelectric valve has an orifice to allow pressurized air to enter the expansion chamber. In some embodiments, the expansion chamber has a third piezoelectric valve to expel the cooled air out of the device.

[0113] (A20) In some embodiments of A19, the air flow component comprises an exhaust and a second valve configured to regulate air flow from the air channel to the exhaust. In some embodiments, the second valve comprises a piezoelectric valve. In some embodiments, the exhaust is coupled to a recursive component configured to direct air from the exhaust to the inlet.

[0114] (B1) In another aspect, some embodiments include a micro-cooling system (e.g., the micro-cooling system 700) that comprises (i) a set of micro-cooling devices (e.g., the micro- cooling device(s) 720) thermally couplable to a heat-generating component, the set of micro- cooling devices comprising: (a) a first substrate (e.g., the substrate 220) composed of a thermally-conductive material; (b) a second substrate (e.g., the substrate 222) coupled to the 124151-5038-WOfirst substrate; (c) a microfluidic channel (e.g., the microfluidic channel 102) formed between the first substrate and the second substrate; and (d) a fluid contained within the microfluidic channel; (ii) one or more sensors (e.g., the sensor(s) 706); and (iii) control circuitry (e.g., the control circuitry 704) coupled to the set of micro-cooling devices and the one or more sensors. In some embodiments, micro-cooling devices in the set of micro-cooling devices include respective, distinct substrates and microfluidic channels (e.g., that are fluidically coupled to one another in a closed fluidic system). In some embodiments, two or more micro-cooling devices share a substrate (e.g., are formed, attached, or defined in a same substrate). In some embodiments, the set of micro-cooling devices comprises instances of any of the micro-cooling devices described herein.

[0115] As an example, the heat-generating component may be a processor component, such as a central processing unit (CPU), graphics processing unit (GPU), micro processing unit (MCU), field-programmable gate array (FPGA), neural processing unit (NPU), or other type of processor component. In some embodiments, the heat-generating component comprises a memory or storage component. In some embodiments, the first substrate is configured to couple to a heat sink or other type of passive heat management component. In some embodiments, the first substrate is configured to couple to a clock component. In some embodiments, the heat- generating component comprises a system-on-a-chip (SoC). In some embodiments, the first substrate is coupled to the heat-generating component via a thermal paste, thermal adhesive, a contact, a via, or other thermal-coupling component.

[0116] (B2) In some embodiments of B1, the micro-cooling system is configured to identify a hot spot (e.g., the hot spot 450-1) of a first component coupled to the first substrate. In some embodiments, the control circuitry is configured to identify the hot spot (e.g., based on signals from the set of sensors and / or signals from the first component). In some embodiments, the control circuitry is electrically coupled to the first component (e.g., a system- on-chip (SoC)).

[0117] (B3) In some embodiments of B1 or B2, the fluid comprises a plurality of magnetic particles (e.g., the magnetic particles 204) and at least one of water, glycol, and ethanol as solvent.

[0118] (B4) In some embodiments of B3, the plurality of magnetic particles comprises a plurality of magnetic dipole particles. 124151-5038-WO

[0119] (B5) In some embodiments of B3 or B4, the micro-cooling system further comprises a set of electromagnets (e.g., the electromagnet(s) 724) arranged adjacent to the microfluidic channel and configured to apply a magnetic field to the fluid within the microfluidic channel. In some embodiments, the magnetic field is configured to align spins of the plurality of magnetic particles within the fluid.

[0120] (B6) In some embodiments of B5, the magnetic field is generated by an alternating current (AC) passing through the set of electromagnets.

[0121] (B7) In some embodiments of B6, the micro-cooling system further comprises a set of flow-control elements (e.g., the flow-control elements 104) configured to direct flow of the fluid toward the hot spot. In some embodiments, the set of piezoelectric actuators is configured to direct flow of the plurality of magnetic particles in the fluid toward the hot spot.

[0122] (B8) In some embodiments of any of B1-B7, the micro-cooling system further comprises a magnetic shielding layer (e.g., the shielding layer 226) coupled to the set of micro- cooling devices. In some embodiments, the magnetic shielding layer is arranged to separate the set of micro-cooling devices from one or more external electronic components.

[0123] (B9) In some embodiments of B8, the magnetic shielding layer is composed of at least one of aluminum, nickel, iron, copper, ferrite, and chromium.

[0124] (B10) In some embodiments of any of B1-B9, the micro-cooling system further comprises a set of flow-control elements (e.g., the flow-control elements 104) coupled to the set of micro-cooling devices and configured to govern flow the fluid contained within the microfluidic channel. In some embodiments, the set of flow-control elements comprises one or more actuators (e.g., piezoelectric actuators). In some embodiments, a set of piezoelectric actuators positioned adjacent to the microfluidic channel and configured to govern flow of the fluid within the microfluidic channel.

[0125] (B11) In some embodiments of B10, the control circuitry is electrically coupled to the set of one or more flow-control elements and configured to govern operation of the set of flow-control elements. For example, the control circuitry may be configured to adjust timing, magnitude, and / or other aspects of the operation of the flow-control elements.

[0126] (B12) In some embodiments of any of B1-B11, the control circuitry is configured to adjust flow of the fluid contained within the microfluidic channel based on a set of temperatures. For example, the controller is configured to direct flow toward channels that are in proximity to one or more hot spots. In some embodiments, the control circuitry receives 124151-5038-WOtemperature information from the set of sensors. In some embodiments, the set of temperatures corresponds to a heat-generating component that is thermally coupled to the micro-cooling system (e.g., via the first substate). In some embodiments, adjusting the flow of the fluid comprises adjusting a velocity, a flow path, and / or a density of the fluid.

[0127] (B13) In some embodiments of B12, the set of temperatures are obtained from the one or more sensors (e.g., the sensor(s) 706). In some embodiments, the one or more sensors comprise one or more temperature sensors. In some embodiments, the control circuitry is electrically coupled to an infrared heat sensor readout integrated circuit (IC).

[0128] (B14) In some embodiments of any of B1-B13, the set of micro-cooling devices further comprise a bonding layer (e.g., the bonding layer 224) connecting the first substrate and the second substrate to define the microfluidic channel.

[0129] (C1) In another aspect, some embodiments include a microfluidic flow-control system that includes (i) a set of one or more microfluidic channels (e.g., the microfluidic channel 102); (ii) a set of one or more flow-control elements (e.g., the flow-control elements 406) configured to govern flow of a fluid within the set of one or more microfluidic channels, each flow-control element of the set of one or more flow-control element positioned adjacent to a respective microfluidic channel of the set of one or more microfluidic channels; and (iii) a piezoelectric actuator (e.g., the piezoelectric actuator 614) coupled to the set of one or more flow-control elements, the piezoelectric actuator configured to provide power to the set of one or more flow-control elements. In various embodiments, the microfluidic flow-control system further includes any of the features described above with respect to the micro-cooling system. In some embodiments, the microfluidic flow-control system includes a first substrate thermally coupled to a first component, and a set of one or more piezoelectric actuators configured to direct flow of the fluid toward identified hot spots. For example, the first component may be an instance of any of the heat-generating components described herein. As an example, for use with a larger component, the microfluidic flow-control system may selectively direct the flow of the magnetic particles to the channel(s) closest to an identified hot spot. In some embodiments, the first component signals the location of the hot spot. In some embodiments, the microfluidic flow-control system comprises one or more thermal sensors configured to detect hot spots. In some embodiments, a plurality of microfluidic devices are fluidly coupled together, and a controller is used to direct flow within the plurality of microfluidic devices to target hot spots. In some embodiments, the first component has multiple thermal zones, and the 124151-5038-WOmicrofluidic flow-control system is configured (e.g., using a controller) to maintain the respective thermal zones at different target temperatures (e.g., with different target temperature ranges and / or below different target temperature thresholds).

[0130] (C2) In some embodiments of C1, the set of one or more flow-control elements comprises a set of one or more piezoelectric actuators.

[0131] (C3) In some embodiments of C2, the set of one or more piezoelectric actuators comprises a set of MEMS membranes. For example, each piezoelectric actuator may be instantiated as a MEMS membrane.

[0132] (C4) In some embodiments of any of C1-C3, the piezoelectric actuator is coupled to the set of one or more flow-control elements via one or more electrical lines. For example, the electrical lines may comprise traces, wires, leads, vias, and / or other conductive elements.

[0133] (C5) In some embodiments of any of C1-C4, the piezoelectric actuator is coupled to the set of one or more flow-control elements via an electrical circuit (e.g., the control circuitry 704). In some embodiments, the electrical circuit comprises control circuitry (e.g., one or more processors and / or controllers) configured to manage power supplied to the set of flow-control elements. In some embodiments, the control circuitry is configured to adjust timing (e.g., a frequency, a rise / fall time, and / or a period) for the flow-control elements. In some embodiments, the control circuitry is configured to adjust a magnitude (e.g., an oscillation magnitude) for the flow-control elements.

[0134] (C6) In some embodiments of any of C1-C5, the microfluidic flow-control system further comprises an air flow component (e.g., the jet air component 610), where the piezoelectric actuator is coupled to the air flow component and configured to actuate in response to air flow from the air flow component.

[0135] (D1) In another aspect, some embodiments include a microfluidic device that comprises: (i) a microfluidic channel (e.g., the microfluidic channel 102) defined by a first substrate (e.g., the substrate 220) and a second substrate (e.g., the substrate 222); (ii) a fluid contained within the microfluidic channel, the fluid comprising a plurality of magnetic particles (e.g., the magnetic particles 204); and (iii) a set of magnets (e.g., the magnet components 202) arranged adjacent to the microfluidic channel and configured to apply a magnetic field to align spins of the plurality of magnetic particles. In various embodiments, the microfluidic device further includes any of the features described above with respect to the micro-cooling system. 124151-5038-WO

[0136] (D2) Some embodiments include a micro-magnetic cooling system that includes a plurality of micro-magnetic cooling devices, each micro-magnetic cooling device comprising an instance of the microfluidic device of D1, where the plurality of micro-magnetic cooling devices are configured to thermally coupled to respective portions of a heat-generating component. In some embodiments, the heat-generating component comprises one or more SoCs, processors, FPGAs, memory devices, power generating and / or converting components, or other types of heat-generating elements. In various embodiments, the micro-magnetic cooling system further includes any of the features described above with respect to the micro- cooling system.

[0137] (D3) In some embodiments of D2, the micro-magnetic cooling system further comprises a set of one or more flow-control elements (e.g., the flow-control elements 104) coupled to the plurality of micro-magnetic cooling devices and configured to govern flow the fluid contained within the respective microfluidic channels. In some embodiments, the set of flow-control elements comprises one or more actuators (e.g., piezoelectric actuators).

[0138] (D4) In some embodiments of D3, the micro-magnetic cooling system further comprises control circuitry (e.g., the control circuitry 412) electrically coupled to the set of one or more flow-control elements and configured to govern operation of the set of one or more flow-control elements. For example, the control circuitry may be configured to adjust timing, magnitude, and / or other aspects of the operation of the flow-control elements.

[0139] (D5) In some embodiments of D4, the control circuitry comprises a controller (e.g., the flow rate controller 714) configured to adjust flow of the fluid contained within the respective microfluidic channels based on a set of temperatures for the heat-generating component. For example, the controller is configured to direct flow toward channels that are in proximity to one or more hot spots. In some embodiments, the control circuitry receives temperature information from the heat-generating component. In some embodiments, adjusting the flow of the fluid comprises adjusting a velocity, a flow path, and / or a density of the fluid. In some embodiments, the control circuitry receives instructions from a CPU / GPU and / or GPGPU that informs the control circuitry of the sequence and target of cooling zone and temperature aligned with the higher clock rates of the multiply-accumulate units of the CPU / GPU or GPGPU. In some embodiments, the flow rate controller is configured to adjust the flow rate based on cooling requirements of the heat-generating component (e.g., heat in a first location may need to be reduced more quickly than heat in a second location). As an 124151-5038-WOexample, the flow rate controller may need to activate additional micro-cooling devices if a hot spot is above a temperature threshold (e.g., obtained from the heat-generating component) to cool the hot spot more quickly.

[0140] (D6) In some embodiments of D5, the micro-magnetic cooling system further comprises one or more temperature sensors (e.g., the sensor(s) 706) communicatively coupled to the controller, where the controller is configured to adjust flow of the fluid contained within the respective microfluidic channels based data from the one or more temperature sensors. In some embodiments, the control circuitry is configured to identify respective temperature targets for different portions of the heat-generating component, and is configured to adjust flow of the fluid to maintain respective temperatures for the different portions at, or below, the respective temperature targets.

[0141] (D7) In some embodiments of D6, adjusting the flow of the fluid comprises adjusting a duty cycle of the set of one or more flow-control elements.

[0142] (D7) In some embodiments of any of D2-D7, the micro-magnetic cooling system further comprises a set of one or more magnetic shielding layers (e.g., the shielding layers 310) arranged to be between the heat-generating component and the respective sets of magnets. For example, the magnetic shielding layer(s) are configured to reduce / prevent the fields generated by the sets of magnets from interfering with operation of the heat-generating component.

[0143] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first array could be termed a second array, and, similarly, a second array could be termed a first array, without departing from the scope of the various described embodiments. The first array and the second array are both arrays, but they are not the same array. As used herein, a set may include one member or multiple members.

[0144] The terminology used in the description of the embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of claims. As used in the description and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and / or “comprising,” when used 124151-5038-WOin this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0145] Reference has been made to embodiments, examples of which are illustrated in the accompanying drawings. In the forgoing description, numerous specific details have been set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these particular details. In other instances, methods, procedures, components, and circuits that are well-known to those of ordinary skill in the art are not described in detail so as not to unnecessarily obscure aspects of the embodiments.

[0146] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the scope of claims to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the various described embodiments and their practical applications, to thereby enable others skilled in the art to best utilize the principles and the various described embodiments with various modifications as are suited to the particular use contemplated. 124151-5038-WO

Claims

What is claimed is:

1. A micro-cooling device, comprising: a first substrate; a second substrate coupled to the first substrate; a microfluidic channel formed between the first substrate and the second substrate; a fluid contained within the microfluidic channel; and a set of one or more piezoelectric actuators positioned adjacent to the microfluidic channel and configured to govern flow of the fluid within the microfluidic channel.

2. The micro-cooling device of claim 1, wherein the first substrate is composed of a thermally-conductive material.

3. The micro-cooling device of claim 1 or 2, further comprising a bonding layer connecting the first substrate and the second substrate to define the microfluidic channel.

4. The micro-cooling device of any of claims 1-3, wherein the fluid comprises at least one of water, glycol, and ethanol.

5. The micro-cooling device of any of claims 1-4, wherein the fluid comprises a plurality of magnetic particles.

6. The micro-cooling device of claim 5, wherein the plurality of magnetic particles comprises a plurality of magnetic dipole particles.

7. The micro-cooling device of claim 5 or 6, further comprising an electromagnet comprising a winding coil wound around a core, the electromagnet arranged adjacent to the microfluidic channel and configured to apply a magnetic field to spin align the plurality of magnetic particles.

8. The micro-cooling device of claim 7, wherein the magnetic field is generated by an alternating current (AC) passing through the winding coil wound around the core.

9. The micro-cooling device of claim 7 or 8, wherein the core comprises one or more magnetic films. 124151-5038-WO10. The micro-cooling device of any of claims 7-9, wherein the core comprises one or more permanent magnets.

11. The micro-cooling device of any of claims 7-10, wherein the electromagnet comprises a multilayer inductor.

12. The micro-cooling device of any of claims 7-11, wherein the electromagnet is at least partially embedded in a bonding layer connecting the first substrate and the second substrate.

13. The micro-cooling device of any of claims 7-12, wherein the electromagnet is attached to at least one of the first substrate and the second substrate.

14. The micro-cooling device of any of claims 1-13, wherein the microfluidic channel comprises a closed loop, and wherein the fluid is recirculated within the closed loop.

15. A method of micro-cooling, comprising: attaching a micro-cooling device to a heat-generating component at a first portion, wherein the micro-cooling device comprises a fluid within a microfluidic channel; and causing the fluid to flow through the microfluidic channel from a second portion of the microfluidic channel toward the heat-generating component, whereby heat from the heat- generating component transfers to the fluid within the microfluidic channel.

16. The method of claim 15, wherein the fluid comprises a plurality of magnetic particles, and wherein heat transfers from the heat-generating component to the plurality of magnetic particles as the spins of the plurality of magnetic particles leave a state of alignment.

17. The method of claim 16, further comprising aligning spins of the plurality of magnetic particles using a set of one or more electromagnets adjacent to the second portion of the microfluidic channel.

18. The method of claim 17, wherein plurality of magnetic particles comprises a plurality of magnetic dipole particles, and wherein aligning spins of the plurality of magnetic particles 124151-5038-WOcomprises aligning dipoles of the plurality of magnetic dipole particles according to an electromagnetic field generated by the set of one or more electromagnets.

19. The method of any of claims 15-18, wherein the fluid is caused to flow through the microfluidic channel using one or more flow-control elements.

20. The method of claim 19, further comprising providing electrical power to the one or more flow-control elements to cause the one or more flow-control elements to displace the fluid contained within the microfluidic channel. 124151-5038-WO

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