Abstract:
Surfaces for electromagnetic shielding, retaining electrostatic charge and indeed collecting ion current in EHD fluid mover designs may be formed as or on surfaces of other components and/or structures in an electronic device. In this way, dimensions may be reduced and packing densities increased. In some cases, electrostatically operative portions of an EHD fluid mover are formed as or on surfaces of an enclosure, an EMI shield, a circuit board and/or a heat pipe or spreader. Depending on the role of these electrostatically operative portions, dielectric, resistive and/or ozone robust or catalytic coatings or conditioning may be applied.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims the benefit of U.S. Provisional Application Nos. 61/348,716, filed May 26, 2010, and 61/478,312, filed Apr. 22, 2011, each of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present application relates to thermal management and, more particularly, to micro-scale cooling devices that generate ions and electrical fields to motivate flow of fluids, such as air, as part of a thermal management solution to dissipate heat. 
     2. Related Art 
     Devices built to exploit ionic movement of a fluid are variously referred to in the literature as ionic wind machines, electric wind machines, corona wind pumps, electro-fluid-dynamic (EFD) devices, electrohydrodynamic (EHD) thrusters, EHD gas pumps and EHD fluid or air movers. Some aspects of the technology have also been exploited in devices referred to as electrostatic air cleaners or electrostatic precipitators. 
     When employed as part of a thermal management solution, an ion flow fluid mover may result in improved cooling efficiency with reduced vibrations, power consumption, electronic device temperatures and/or noise generation. These attributes may reduce overall lifetime costs, device size or volume, and in some cases may improve system performance or user experience. 
     As electronic device designers drive to smaller and smaller form-factors, such as in the extremely thin handheld devices popularized by iPhone™ and iPad™ devices available from Apple, Inc., packing densities of components and subsystems create significant thermal management challenges. In some cases, active strategies to exhaust heat to the ambient environment may be required. In some cases, mass transport across a ventilation boundary may be unnecessary, but heat transport within the device may be necessary or desirable to reduce hotspots. 
     Ion flow fluid movers present an attractive technology component of thermal management solutions. Solutions are desired that allow ion flow fluid movers to be integrated in thin and/or densely packed electronic devices, often in volumes that provide as little as 2-3 mm of clearance in a critical dimension. In particular, solutions are desired that allow dense packing of high-voltage, ion-flux generating EHD components with electronic assemblies that may be otherwise sensitive to electrostatic discharge and or electromagnetic interference. In some cases, solutions are desired that manage or mitigate ozone byproducts of certain high intensity fields and/or discharges. 
     SUMMARY 
     It has been discovered that surfaces for electromagnetic shielding, retaining electrostatic charge and indeed collecting ion current in EHD fluid mover designs may be opportunistically formed as or on surfaces of other components and/or structures in an electronic device. In this way, dimensions may be reduced and packing densities increased. In some cases, electrostatically operative portions of an EHD fluid mover are formed as or on interior surfaces of an enclosure, an EMI shield, a circuit board and/or a heat pipe or spreader. Depending on the role of these electrostatically operative portions, dielectric, resistive and/or ozone robust or catalytic coatings or conditioning may be applied. 
     In some embodiments in accordance with the present invention(s), an electronic device includes an enclosure; at least one electronic assembly including one or more thermal sources disposed thereon; and an EHD fluid mover configured as part of a thermal management system for the electronic device, wherein at least one electrostatically operative portion of the EHD fluid mover is formed as, or on, an interior surface of the enclosure. In some cases, the electronic device has a thickness of less than about 10 mm and extent in one or more lateral dimensions that exceeds the thickness by at least a factor of 10::1. 
     In some embodiments, the EHD fluid mover includes at least one emitter electrode and at least one collector electrode, wherein the at least one electrostatically operative portion includes the collector electrode. In some embodiments, the at least one electrostatically operative portion includes a dielectric coated field shaping portion of the interior surface of the enclosure adjacent to the emitter electrode. In some cases, the dielectric is provided at least in part as a polyimide film or tape affixed, at least in part, on or over the interior surface. In some cases, the dielectric is resistant to degradation in an ozone containing fluid. In some cases, the dielectric coated field shaping portion of the interior surface extends about three (3) emitter electrode to collector electrode lengths upstream of the emitter electrode. 
     In some embodiments, the low profile device further includes a second electrostatically operative portion of the EHD fluid mover overlaying at least a portion of the electronic assembly. In some cases, the overlaid portion of the electronic assembly defines at least a portion of a high voltage power supply coupled to energize the EHD fluid mover. In some cases, the electronic assembly includes one or more of a circuit board and a display device. In some cases, the thermal sources include one or more of a processor; a radio frequency (RF) or optical transceiver; and illumination sources for a display device. 
     In some embodiments, the enclosure is substantially sealed such that fluid flow motivated by the EHD fluid mover is substantially contained within the enclosure. In some embodiments, the enclosure allows at least some fluid flow to transit a boundary between an interior volume therewithin and the exterior. In some cases, flux of fluid through the EHD fluid mover substantially exceeds, at least by a factor of two, that transiting the boundary. In some cases, the enclosure includes one or more ventilation portions of the boundary through which a substantial entirety of the fluid flux motivated by the EHD fluid mover is admitted and exhausted. 
     In some embodiments, the thermal sources are closely proximate, within about 3 mm, of an interior surface of the enclosure, and the thermal management system operable to spread heat evolved at the thermal sources over a substantial portion of the interior surface. 
     In some embodiments, the electronic device is configured as one or more of a handheld mobile phone or personal digital assistant; a laptop, netbook or pad-type computer; and a digital book reader, media player or gaming device. In some embodiments, the electronic device is configured as one or more of a display panel and a television. 
     In some embodiments in accordance with the present invention, an electronic device includes at least one electronic assembly including one or more thermal sources disposed thereon; an electromagnetic interference (EMI) shield of conductive material; and an EHD fluid mover configured as part of a thermal management system for the electronic device, wherein at least one electrostatically operative portion of the EHD fluid mover is formed as, or on, a surface of the EMI shield. 
     In some embodiments, the EMI shield at least partially overlays a portion of the electronic assembly. In some cases, the overlaid portion the electronic assembly includes at least a portion of a high voltage power supply coupled to energize the EHD fluid mover. In some cases, one or more conductive planes or traces of the electronic assembly provide the EMI shield. 
     In some embodiments, the electronic device has a thickness of less than about 10 mm, and extent in one or more lateral dimensions exceeds the thickness by at least a factor of 10::1. 
     In some embodiments, the EHD fluid mover includes at least one emitter electrode and at least one collector electrode, wherein the at least one electrostatically operative portion includes the collector electrode. In some embodiments, the at least one electrostatically operative portion includes a dielectric coated field shaping portion of the surface of the EMI shield adjacent to the emitter electrode. In some cases, the dielectric coated field shaping portion of the exposed surface extends about three (3) emitter electrode to collector electrode lengths upstream of the emitter electrode. In some cases, the dielectric coating is resistant to degradation in an ozone containing fluid. 
     In some embodiments, the electronic assembly includes one or more of a circuit board and a display device. In some embodiments, the thermal sources include one or more of a processor; a radio frequency (RF) or optical transceiver; and illumination sources for a display device. 
     In some embodiments, the electronic device further includes an enclosure substantially sealed such that fluid flow motivated by the EHD fluid mover is substantially contained within the enclosure. In some embodiments, the electronic device further includes an enclosure that allows at least some fluid flow to transit a boundary between an interior volume therewithin and the exterior. In some cases, flux of fluid through the EHD fluid mover substantially exceeds, at least by a factor of two, that transiting the boundary. In some cases, the enclosure includes one or more ventilation portions of the boundary through which a substantial entirety of the fluid flux motivated by the EHD fluid mover is admitted and exhausted. 
     In some embodiments, the electronic device further includes an enclosure, wherein the thermal sources are closely proximate, within about 3 mm, of an interior surface of the enclosure, the thermal management system being operable to spread heat evolved at the thermal sources over a substantial portion of the interior surface. 
     In some embodiments, the electronic device further includes an enclosure, wherein at least one other electrostatically operative portion of the EHD fluid mover is formed as, or on, an interior surface of the enclosure. 
     In some embodiments, the EMI shield also defines at least a portion of a thermally conductive pathway from the thermal sources to heat transfer surfaces in a flow path along which fluid flow is motivated by the EHD fluid mover when energized. 
     In some embodiments in accordance with the present invention, an electronic device includes a display; at least one circuit board, an electrohydrodynamic (EHD) fluid mover and an enclosure layered one atop another to define a total thickness of the electronic device at less than about 10 mm. The EHD fluid mover is configured as part of a thermal management system for the electronic device and including opposing planar dielectric surfaces, at least one emitter electrode and one or more collector electrodes, the emitter electrode positioned between the opposing planar dielectric surfaces and proximate to the collector electrode to, when energized, accelerate ions toward the collector electrode and thereby motivate fluid flow within the electronic device, wherein a first one of the opposing dielectric surfaces is at least partially formed as or on a surface of an EMI shield over the circuit board. 
     In some embodiments, the collector electrodes number at least two and a first one of the collector electrodes formed as or on an exposed metallization layer of the circuit board. In some embodiments, a second one of the collector electrodes is formed as or on an interior surface of the enclosure. In some embodiments, at least a portion of the EMI shield is formed as or on a dielectric coated metallization layer of the circuit board. 
     In some embodiments, the electronic device of further includes a thermal transfer pathway from one or more thermal sources disposed on the circuit board to heat transfer surfaces in a flow path along which fluid flow is motivated by the EHD fluid mover when energized. In some cases, at least a portion of the thermal transfer pathway provided by the EMI shield. 
     In some embodiments, the thermal sources are closely proximate, within about 3 mm, of an interior surface of the enclosure, and the thermal management system is operable to spread heat evolved at the thermal sources over a substantial portion of the interior surface. 
     In some embodiments, the enclosure substantially seals the electronic device such that fluid flow motivated by the EHD fluid mover is substantially contained therewithin. In some embodiments, the enclosure allows at least some fluid flow to transit a boundary between an interior volume therewithin and the exterior. In some embodiments, flux of fluid through the EHD fluid mover substantially exceeds, at least by a factor of two, that transiting the boundary. In some embodiments, the enclosure includes one or more ventilation portions of the boundary through which a substantial entirety of the fluid flux motivated by the EHD fluid mover is admitted and exhausted. 
     In some embodiments, the electronic device is configured as one or more of a handheld mobile phone or personal digital assistant; a laptop, netbook or pad-type computer; and a digital book reader, media player or gaming device. In some embodiments, the electronic device is configured as one or more of a display panel and a television. 
     In some embodiments, at least a portion of either or both of the circuit board and an interior surface of the enclosure are coated with a protective coating robust to ozone. In some embodiments, the protective coating robust to ozone includes a fluoropolymer of tetrafluoroethylene such as a Teflon® material. In some embodiments, at least a portion of either or both of the circuit board and an interior surface of the enclosure are coated with an ozone catalytic or reactive material. 
     In some embodiments in accordance with the present invention, an electronic device includes an electronic assembly having one or more thermal sources disposed thereon; and a thermal management system including an EHD fluid mover and a heat transfer pathway from the thermal sources to heat transfer surfaces in a flow path of fluid motivated by operation of the EHD fluid mover, the heat transfer pathway including surfaces coated with an ozone resistant dielectric. 
     In some embodiments, the heat transfer pathway includes either or both of a heat pipe and a head spreader. In some embodiments, at least a portion of the heat transfer pathway is coated with an ozone catalytic or reactive material. These and other embodiments will be understood with reference to the description herein, the drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. Drawings are not necessarily to scale; rather, emphasis has instead been placed upon illustrating the structural and fabrication principles of the described embodiments. 
         FIG. 1A  is a perspective view of an illustrative, pad-type, consumer electronics device in which, in accord with some embodiments of the present invention, an EHD fluid mover is accommodated within a total device thickness of typically less than about 10 mm, including the thickness of a display surface that covers a substantial entirety of a major surface thereof.  FIG. 1B  depicts (in general correspondence with an interior volume of the device of  FIG. 1A ) an illustrative ventilating air flow topology and placement of an EHD fluid mover relative to respective electronic assemblies.  FIG. 1C  illustrates another illustrative ventilating air flow topology and placement of an EHD fluid mover relative to respective electronic assemblies. 
         FIG. 2A  is a perspective view of an illustrative, pad-type, consumer electronics device, again in accord with some embodiments of the present invention, in which an EHD fluid mover is accommodated within a total device thickness of typically less than about 10 mm, including the thickness of a display surface that covers a substantial entirety of a major surface thereof.  FIG. 2B  depicts (in general correspondence with an interior volume of the device of  FIG. 2A ) an illustrative recirculating fluid flow topology and placement of an EHD fluid mover relative to respective electronic assemblies.  FIG. 2C  illustrates a variation in which the flow topology includes both a circulating flow component and some flow that enters and exits the device through ventilation boundaries. 
         FIGS. 3 ,  5  and  6  depict, in illustrative cross-sections, device configurations in which electrostatically operative portions of an EHD fluid mover are formed as, or on, respective surfaces of a device enclosure and/or Electromagnetic Interference (EMI) shield overlaying an electronic assembly.  FIGS. 5 and 6  depict illustrative cross-sections in which a display surface is part of the device stack that includes an EHD fluid mover.  FIG. 6  depicts an illustrative cross-section in which collector electrode surfaces are formed on a metallization of a printed circuit board. 
         FIG. 4  depicts an illustrative high voltage power supply configuration in which emitter and collector electrodes are energized to motivate fluid flow. 
         FIG. 7A  is a perspective view of an illustrative, laptop-style, consumer electronics device in which, in accord with some embodiments of the present invention, an EHD fluid mover is accommodated within a total device thickness of typically less than about 10 mm.  FIGS. 7B and 7C  depict (in respective plan views and generally in correspondence with a base portion the laptop-style device of  FIG. 7A ) illustrative positional relations between components and ventilating air flows.  FIG. 7C  depicts an interior view with illustrative positioning an EHD air mover, whereas  FIG. 7B  depicts a top surface view in which the keyboard (and its underlying electronic assembly) at least partially overlays the EHD air mover. 
         FIGS. 8A and 8C  depict, in illustrative cross-sections, a device configuration in which electrostatically operative surfaces of an EHD air mover are formed as, or on, respective surfaces of a device enclosure and/or Electromagnetic Interference (EMI) shield underlying an electronic assembly. In some realizations,  FIG. 8A  corresponds generally to a cross-section shown in  FIGS. 7B and 7C .  FIG. 8B  depicts a partial interior view of an electrostatically operative, air-flow-permeable surface of the EHD air mover illustrated in  FIG. 8A .  FIG. 8C  depicts an alternative cross-section wherein an exoskeletal structure of an EHD air mover subassembly facilitates relative positional fixation of collector and emitter electrodes with respect to each other, and wherein at least a portion of one of the electrostatically operative surfaces is formed over a portion of the exoskeletal structure.  FIG. 8D  is a perspective cutaway view corresponding to  FIG. 8C . 
         FIGS. 9A and 9B  depict, in further illustrative cross-sections, device configurations in which opposing electrostatically operative portions of an EHD fluid mover are formed as, or on, respective surfaces of Electromagnetic Interference (EMI) shields underlying (or overlaying) respective electronic assemblies. In some realizations,  FIGS. 9A and 9B  correspond to variations in which a circuit board-type electronic assembly is part of the device stack that includes the EHD fluid mover. 
         FIGS. 10A and 10B  are respective edge-on side and perspective views of an illustrative, flat panel display style, consumer electronics device in which, in accord with some embodiments of the present invention, an EHD fluid mover is accommodated within a total device depth typically less than about 10 mm. 
         FIG. 11A  is an interior view (generally in correspondence with flat panel display device of  FIGS. 10A and 10B ) illustrating positional relations between components and ventilating air flows.  FIGS. 11B and 11C  depict, in illustrative cross-sections of the flat panel display device, opposing electrostatically operative portions of respective EHD air movers formed as, or on, respective surfaces of a device enclosure and an Electromagnetic Interference (EMI) shield overlaying a display. 
     
    
    
     Use of the same reference symbols in different drawings indicates similar or identical items. 
     DETAILED DESCRIPTION 
     As will be appreciated, many of the designs and techniques described herein have particular applicability to the thermal management challenges of densely-packed devices and small form-factors typical of modern consumer electronics. Indeed, some of the EHD fluid/air mover designs and techniques described herein facilitate active thermal management in electronics whose thinness or industrial design precludes or limits the viability of mechanical air movers such as fans, blowers, etc. In some embodiments, such EHD fluid/air movers may be fully integrated in an operational system such as a pad-type or laptop computer, a projector or video display device, a set-top box, etc. In other embodiments, such EHD fluid/air movers may take the form of subassemblies or enclosures adapted for use in providing such systems with EHD motivated flows. 
     In general, a variety of scales, geometries and other design variations are envisioned for electrostatically operative surfaces that provide field shaping or that functionally constitute a collector electrode, together with a variety of positional interrelationships between such electrostatically operative surfaces and the emitter and/or collector electrodes of a given EHD device. For purposes of illustration, we focus on certain exemplary embodiments and certain surface profiles and positional interrelationships with other components. For example, in much of the description herein, opposing planar collector electrodes are formed on interior surfaces of an enclosure or on an exposed surface of an electromagnetic interference (EMI) shield or printed circuit board (PCB) and arranged as parallel surfaces proximate to a corona discharge-type emitter wire that is displaced from leading portions of the respective collector electrodes. Nonetheless, other embodiments may employ other electrostatically operative surface configurations or other ion generation techniques and will nonetheless be understood in the descriptive context provided herein. 
     In the present application, some aspects of embodiments illustrated and described herein are referred to as electrohydrodynamic fluid accelerator devices, also referred to as “EHD devices,” “EHD fluid accelerators,” “EHD fluid movers,” and the like. For purposes of illustration, some embodiments are described relative to particular EHD device configurations in which a corona discharge at or proximate to an emitter electrode operates to generate ions that are accelerated in the presence of electrical fields, thereby motivating fluid flow. While corona discharge-type devices provide a useful descriptive context, it will be understood (based on the present description) that other ion generation techniques may also be employed. For example, in some embodiments, techniques such as silent discharge, AC discharge, dielectric barrier discharge (DBD), or the like, may be used to generate ions that are in turn accelerated in the presence of electrical fields and motivate fluid flow. 
     Using heat transfer surfaces that, in some embodiments, take the form of heat transfer fins, heat dissipated by electronics (e.g., microprocessors, graphics units, etc.) and/or other components can be transferred to the EHD motivated fluid flow and exhausted from an enclosure through a ventilation boundary. Typically, when a thermal management system is integrated into an operational environment, heat transfer paths (often implemented as heat pipes or using other technologies) are provided to transfer heat from where it is dissipated (or generated) to a location (or locations) within the enclosure where air flow motivated by an EHD device (or devices) flows over heat transfer surfaces. 
     For illustration, heat transfer fins are depicted with respect to various exemplary embodiments. However, as will be appreciated based on the description herein, in some embodiments, conventional arrays of heat sink fins need not be provided and EHD motivated fluid flow over exposed interior surfaces, whether proximate a heat generating device (such as a processor, memory, RF section, optoelectronics or illumination source) or removed therefrom, may provide sufficient heat transfer. In each case, provision of ozone catalytic or reactive surfaces/materials on heat transfer surfaces may be desirable. Typically, heat transfer surfaces, field shaping surfaces and dominant ion collecting surfaces of a collector electrode present differing design challenges and, relative to some embodiments, may be provided using different structures or with different surface conditioning. However, in some embodiments, a single structure may be both electrostatically operative (e.g., to shape fields or collect ions) and provide heat transfer into an EHD motivated fluid flow. 
     Note that, in some unventilated embodiments, EHD motivated fluid flow may be circulated within an enclosure, which in turn, may radiatively or convectively transfer heat to the ambient environment. In this way, hotspots on the exterior surface of the enclosure can be eliminated or at least mitigated even without significant airflow through a ventilation boundary. Of course, in some embodiments, EHD motivated flow(s) may be employed both to manage localized hotspots and to exhaust heat by forced convective heat transfer to an air flow that transits a ventilation boundary. 
     Electrohydrodynamic (EHD) Fluid Acceleration, Generally 
     Basic principles of electrohydrodynamic (EHD) fluid flow are well understood in the art and, in this regard, an article by Jewell-Larsen, N. et al., entitled “Modeling of corona-induced electrohydrodynamic flow with COMSOL multiphysics” (in the  Proceedings of the ESA Annual Meeting on Electrostatics  2008) (hereafter, “the Jewell-Larsen Modeling article”), provides a useful summary. Likewise, U.S. Pat. No. 6,504,308, filed Oct. 14, 1999, naming Krichtafovitch et al. and entitled “Electrostatic Fluid Accelerator” describes certain electrode and high voltage power supply configurations useful in some EHD devices. U.S. Pat. No. 6,504,308, together with sections I (Introduction), II (Background), and III (Numerical Modeling) of the Jewell-Larsen Modeling article are hereby incorporated by reference herein for all that they teach. 
     EHD fluid mover designs described herein can include one or more corona discharge-type emitter electrodes. In general, such corona discharge electrodes include a portion (or portions) that exhibit(s) a small radius of curvature and may take the form of a wire, rod, edge or point(s). Other shapes for the corona discharge electrode are also possible; for example, the corona discharge electrode may take the shape of barbed wire, wide metallic strips, and serrated plates or non-serrated plates having sharp or thin parts that facilitate ion production at the portion of the electrode with the small radius of curvature when high voltage is applied. In general, corona discharge electrodes may be fabricated in a wide range of materials. For example, in some embodiments, compositions such as described in U.S. Pat. No. 7,157,704, filed Dec. 2, 2003, entitled “Corona Discharge Electrode and Method of Operating the Same” and naming Krichtafovitch et al. as inventors may be employed. U.S. Pat. No. 7,157,704 is incorporated herein for the limited purpose of describing materials for some emitter electrodes that may be employed in some corona discharge-type embodiments. In general, a high voltage power supply creates the electric field between corona discharge electrodes and collector electrodes. 
     EHD fluid mover designs described herein include ion collection surfaces positioned downstream of one or more corona discharge electrodes. Often, ion collection surfaces of an EHD fluid mover portion include leading surfaces of generally planar collector electrodes extending downstream of the corona discharge electrode(s). In some cases, a collector electrode may do double-duty as heat transfer surfaces. In some cases, a fluid permeable ion collection surface may be provided. 
     In general, collector electrode surfaces may be fabricated of any suitable conductive material, such as aluminum or copper. Alternatively, as disclosed in U.S. Pat. No. 6,919,698 to Krichtafovitch, collector electrodes (referred to therein as “accelerating” electrodes) may be formed of a body of high resistivity material that readily conducts a corona current, but for which a result voltage drop along current paths through the body of high resistivity collector electrode material provides a reduction of surface potential, thereby damping or limiting an incipient sparking event. Examples of such relatively high resistance materials include carbon filled plastic, silicon, gallium arsenide, indium phosphide, boron nitride, silicon carbide, and cadmium selenide. U.S. Pat. No. 6,919,698 is incorporated herein for the limited purpose of describing materials for some collector electrodes that may be employed in some embodiments. Note that in some embodiments described herein, a surface conditioning or coating of high resistivity material (as contrasted with bulk high resistivity) may be employed. 
     Thin, Low-Profile or High-Aspect-Ratio Devices, Generally 
       FIG. 1A  is perspective view of an illustrative, pad-type, consumer electronics device  100  with total thickness d of less than about 10 mm and in which a display surface  101  covers substantially an entire major surface thereof.  FIG. 1A  illustrates exemplary air flows  102  that may be motivated through the consumer electronics device by an EHD air mover  110  designed and packed within the limited interior in accord with some inventive concepts of the present inventions. In some implementations, available interior volumes and/or assemblies may allow only 5 mm or less of the total thickness d for EHD air mover  110 . Of course, positions illustrated for inflow(s), outflow(s) and heat transfer surfaces  120  are purely exemplary and, more generally, ventilation boundaries may be dictated by interior placement of components, thermal challenges of a particular device configuration and/or industrial design factors. 
       FIG. 1B  illustrates (in top plan view with the display surface removed) an air flow topology and placement of EHD air mover  110  relative to an illustrative design in which respective electronic assemblies  130 ,  140  (or circuit boards) for processors (e.g., CPU, GPU, etc.) and/or radio frequency (RF) sections (e.g., WiFi, WiMax, 3G/4G voice/data, GPS, etc.) are positioned toward an upper edge of device  100  and in which certain edge-positioned ventilation boundaries (e.g., inlet  151  and outlet  152 ) are provided.  FIG. 1C  illustrates another illustrative ventilating air flow topology and placement of an EHD air mover  110  relative to respective electronic assemblies and heat transfer surfaces  120 . As before, positioning of inlet and outlet ventilation boundaries ( 151  and  152 ) is purely exemplary and, more generally, ventilation boundaries may be dictated by interior placement of components, thermal challenges of a particular device configuration and/or industrial design factors. 
       FIG. 2A  is perspective view of another illustrative low-profile, pad-type, consumer electronics device  200  with total thickness d of less than about 10 mm and in which a display surface  101  covers substantially an entire major surface thereof, but in which thermal management is facilitated by a circulating air (or other fluid) flow  202  within the device enclosure, and in which the motivated flow need not transit a ventilation boundary.  FIG. 2A  illustrates exemplary fluid flows that may be motivated within the consumer electronics device by an EHD fluid mover  210  designed and packed within the limited interior in accord with some inventive concepts of the present inventions. As before, in some implementations, available interior volumes and/or assemblies may allow only 5 mm or less of the total thickness d for EHD fluid mover  210 . 
       FIG. 2B  illustrates (again in top plan view with the display surface removed) an air flow topology contained substantially within the device and an illustrative placement of EHD fluid mover  210  relative to respective electronic assemblies  230 ,  240  (or circuit boards) for processors and/or radio frequency (RF) sections are positioned toward an upper edge of device  200 . Of course, the illustrated flow topology is purely exemplary and, more generally, may be dictated by interior placement of components, thermal challenges of a particular device configuration and/or industrial design factors.  FIG. 2C  illustrates a variation in which the flow topology include both a circulating flow component  202 A and some flow  202 B that enters and exits the device through ventilation boundaries  251  and  252 . 
     Other thin, low-profile or high-aspect-ratio devices are also contemplated. For example,  FIG. 7A  is a perspective view of an illustrative, laptop-style, consumer electronics device  700  in which, in accord with some embodiments of the present invention, an EHD fluid mover is accommodated within a body portion  701 A having a total thickness d of less than about 10 mm.  FIG. 7A  illustrates exemplary inflows  702  and outflows  703  that may be motivated through the consumer electronics device by an EHD air mover  710  designed and packed within the limited interior in accord with some inventive concepts of the present inventions. In some implementations, available interior volumes and/or assemblies may allow only 5 mm or less of the total thickness d for EHD air mover  710 . Of course, positions illustrated for inflow(s), outflow(s) and heat transfer surfaces  720  are purely exemplary and, more generally, ventilation boundaries may be dictated by interior placement of components, thermal challenges of a particular device configuration and/or industrial design factors. 
       FIGS. 7B and 7C  illustrate (in top plan view) air flow topologies and placement of an EHD air mover  710  relative to an illustrative design in which respective electronic assemblies, such as a keyboard assembly  740  and a circuit board  730  for processors (e.g., CPU, GPU, etc.) and/or radio frequency (RF) sections (e.g., WiFi, WiMax, 3G/4G voice/data, GPS, etc.) are positioned toward an upper edge of body portion  701 A and in which certain edge-positioned ventilation boundaries (e.g., inlets  751  and outlet  752 ) are provided. In the views of  FIGS. 7B and 7C , display portion  701 B has been eliminated for clarity. In the view of  FIG. 7C , keyboard assembly  740  and an upper surface of body portion  701 A are also removed to reveal an illustrative interior layout and illustrative internal air flows motivated (i.e., forced or drawn) by EHD air mover  710  over circuit board  730  and/or heat transfer surfaces  720 . Heat pipe (or spreader)  721  provides a heat transfer path from selected thermal sources on circuit board  730  (e.g., CPU  731  and graphics unit  732 ) to heat transfer surfaces  720 , while air flows drawn over circuit board  730  by EHD air mover  710  provide additional cooling. 
     Turning to still another type of devices contemplated,  FIGS. 10A and 10B  are respective edge-on side and perspective views of an illustrative, flat panel display style, consumer electronics device  1000  in which, in accord with some embodiments of the present invention, an EHD fluid mover is accommodated within a body portion  701 A having total thickness d of less than about 10 mm.  FIG. 10A  illustrates exemplary inflows  1002  and outflows  1003  that may be motivated through the consumer electronics device by EHD air movers  1010  designed and packed within the limited interior in accord with some inventive concepts of the present inventions. In some implementations, available interior volumes and/or assemblies may allow only 5 mm or less of the total thickness d for EHD air mover  1010 . 
     Of course, positions illustrated for inflow(s), outflow(s) and heat transfer surfaces  1020  are purely exemplary and, more generally, ventilation boundaries may be dictated by interior placement of components, thermal challenges of a particular device configuration and/or industrial design factors.  FIG. 11A  depicts one embodiment generally in accord with  FIGS. 10A and 10B , in which elongate, edge-positioned arrays of illumination sources (LED illuminators  1150 ) generate heat which, during operation, is convectively transferred by way of heat transfer surfaces  1020  into air flows ( 1002 ,  1003 ) motivated by EHD air movers  1010 A,  1010 B. In the illustrated configuration, bottom-mounted EHD air mover instances ( 1010 A) force air into the enclosure at the bottom of consumer electronics device  1000 , while top-mounted EHD air mover instances ( 1010 B) exhaust air from the top. 
     The pad-type, laptop-style and television-style consumer electronics device embodiments described above are merely illustrative. Indeed, based on the present description, persons of ordinary skill in the art will appreciate these and other device exploitations of inventive concepts of the present inventions including variations and/or adaptations appropriate for particular form factors, electronic assembly types and placements, thermal challenges and/or industrial design factors that pertain to a given design. In view of the foregoing, we now turn to EHD air mover designs suitable for integration within the limited thicknesses of the illustrated consumer electronics device. 
     EHD Air Mover Designs 
     Pad-Type Device Embodiments 
     Referring back generally to  FIG. 1A  and the illustrative pad-type, consumer electronics device  100  depicted therein, we now illustrate (in cross-section) by way of  FIGS. 3 ,  5  and  6 , several EHD fluid (or air) mover configurations in which electrostatically operative portions of the design are formed as, or on, a surface within the device enclosure. In some cases, at least one of the electrostatically operative portions is formed as, or on, an interior surface of the enclosure itself. In some cases, at least one of the electrostatically operative portions is formed as, or on, a surface of an EMI shield that overlays an electronics assembly such as a circuit board or display device. In each case, by forming electrostatically operative portions as, or on, such surfaces, EHD fluid/air movers can be accommodated within very limited interior spaces. 
     For example, in thin, low-profile or high-aspect-ratio consumer electronics devices such as illustrated in  FIGS. 3 ,  5  and  6 , total thickness d may preferably be less than about 10 mm, with printed circuit board (PCB) mounted integrated circuits, discretes, connectors, etc. occupying a substantial portion of the available interior space. Examples of PCB mounted integrated circuits include central processor units (CPUs), graphics processor units (GPUs), communications processors and transceivers, memory, etc., which can often generate a substantial portion of the devices heat load and which, in some embodiments, are cooled by the very EHD fluid/air movers that can be accommodated closely proximate to the heat sources (or thermally coupled fins/spreaders). 
     In some cases, such as illustrated in  FIG. 3 , it is desirable to accommodate (i) a display  301 , (ii) a double-sided PCB  361  (with its affixed integrated circuits [ 362 ,  363 ,  364 ], discretes  365  and connectors  366 ) and (iii) an EHD air mover  310  all within a device stack and volume at least partially bounded by enclosure  309 . Although available interior volumes and tolerances are, in general, implementation and design dependent, it should be clear from the illustrations and description herein that a consumer electronics device may afford 5 mm or less of its total thickness d for EHD air mover  310 . In some embodiments, heat transfer (HT) fins  320  are also dimensioned to fit within the limited thickness provided. 
       FIG. 4  depicts (in schematic form) an illustrative configuration in which a high voltage power supply  491  is coupled between an emitter electrode  491  and collector electrodes  492  to generate an electric field and in some cases ions that motivate fluid flow  499  in a generally downstream direction. In the illustration, emitter electrode  491  is coupled to a positive high voltage terminal of power supply  491  (illustratively +3.5 KV, although specific voltages and, indeed, any supply voltage waveforms may be matters of design choice) and collector electrodes  492  are coupled to a local ground. See previously incorporated U.S. Pat. No. 6,508,308 for a description of suitable designs for power supply  491 . Given the substantial voltage differential and short distances involved (perhaps 1 mm or less) between emitter electrode  491  and leading surfaces of collector electrodes  492 , strong electrical fields are developed which impose a net downstream motive force on positively charged ions (or particles) in the fluid. Field lines illustrate (generally) spatial aspects of the resulting electric field and spacing of the illustrated field lines is indicative of intensity. 
     As will be understood by persons of ordinary skill in the art, corona discharge principles may be employed to generate ions in the intense electric field closely proximate the surface of a corona-discharge type emitter electrode. Thus, in corona discharge type embodiments in accord with  FIG. 4 , fluid molecules (such as surrounding air molecules) near emitter electrode  491  become ionized and the resulting positively charged ions are accelerated in the electric field toward collector electrodes  492 , colliding with neutral fluid molecules in the process. As a result of these collisions, momentum is transferred from the ions to neutral fluid molecules, inducing a corresponding movement of fluid molecules in a net downstream direction. While the positively charged ions are attracted to, and neutralized by, collector electrodes  492 , the neutral fluid molecules move past collector electrodes  492  at an imparted velocity (as indicated by fluid flow  499 ). The movement of fluid produced by corona discharge principles has been variously referred to as “electric,” “corona” or “ionic” wind and has generally been defined as the movement of gas induced by the movement of ions from the vicinity of a high voltage discharge electrode. 
     Notwithstanding the descriptive focus on corona discharge type emitter electrode configurations, persons of ordinary skill in the art will appreciate that ions may be generated by other techniques such as silent discharge, AC discharge, dielectric barrier discharge (DBD), or the like, and once generated, may, in turn, be accelerated in the presence of electrical fields to motivate fluid flow as described herein. For avoidance of doubt, emitter electrodes need not be of a corona discharge type in all embodiments. Also for avoidance of doubt, power supply voltage magnitudes, polarities and waveforms (if any) described with respect to particular embodiments are purely illustrative and may differ for other embodiments. 
     Some embodiments described herein will be further understood in light of certain surfaces provided upstream of emitter electrode  491  to shape the electric previously described electric field and/or to provide a barrier to upstream migration of ions. For example, relative to the illustration of  FIG. 4 , dielectric surfaces  493  are provided on which positively charge (such as from ions generated at a corona discharge type instance of emitter electrode  491  or elsewhere) tends to accumulate. Because dielectric surfaces  493  do not provide an attractive path to ground, a net positive charge tends to accumulate and thereafter operate electrostatically to repel like charges. As a result, dielectric surfaces  493  are electrostatically operative as a barrier to upstream ion migration. Upstream dielectric surfaces  493  also tend to electrostatically mask any otherwise attractive paths to ground, thereby shaping the previously described electric field in the primarily downstream direction toward collector electrodes  492 . To improve performance, an air gap may be provided between leading edges of collector electrodes  492  and adjacent portions of dielectric surfaces  493 . For example, in some embodiments, an air gap may be provided in the form of a shallow trench formed in dielectric surfaces  493  as illustrated in  FIG. 4 . Optionally, in some embodiments, one or more conductive paths  494  to ground may be provided further upstream of dielectric surfaces  493  to capture ions that may nonetheless migrate upstream. In some ventilated device embodiments, such a conductive path  494  to ground may be provided proximate an inlet vent. 
     Building on the preceding description, but now referring back to  FIG. 3 , it has been discovered that, given the very limited thickness that may be available to a thermal management solution within the interior of commercially desirable form factors, designs in which electrostatically operative surfaces such as a collector electrode or a field shaping, charge collecting surface are formed as, or on, an exposed surface tend to save precious millimeters of thickness that would otherwise be squandered in a more conventional design in which electrodes might be packaged within the walls of an EHD air mover subassembly. In this regard,  FIG. 3  illustrates a design in which a pair of generally planar collector electrodes  392  is formed on opposing surfaces to establish, with emitter electrodes  391  and when energized with a high voltage power supply as previously described with reference to  FIG. 4 , a generally downstream EHD motivated air flow. 
     In the illustrated configuration, a first, lower, instance of collector electrode  392  is formed on or as part of an interior surface of enclosure  309 . For example, in some embodiments, a conductive (e.g., metallic) tape or strip may be affixed to the interior surface of a generally non-conductive case or surface thereof and coupled to ground to define the first collector electrode instance. In general, the conductive tape or strip may be cut to a shape and extent desired for collector electrode  392 . Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) layer or region may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode  392 . In some cases, the grounded conductive layer or region may be, or may be formed integrally with, enclosure  309 . 
     A second, upper, instance of collector electrode  392  is likewise formed on or as part of an EMI shield  308  that isolates EHD air mover  310  from the integrated circuits ( 362 ,  363 ,  364 ), discretes  365  and/or connectors  366  affixed to double-sided PCB  361 . A conductive (e.g., metallic) tape or strip may be affixed to an otherwise non-conductive exposed surface of EMI shield  308  and coupled to ground to define the second collector electrode instance. As before, the conductive tape or strip may be cut to a shape and extent desired for collector electrode  392 . Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) interior layer or region of EMI shield  308  may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode  392 . 
     As with collector electrodes  392 , respective upper and lower instances of dielectric surfaces  393  are provided on, or as part of, a surface of EMI shield  308  or enclosure  309 . As previously described with reference to  FIG. 4 , such dielectric surfaces are electrostatically operative and contribute to field shaping in the EHD fluid mover while also providing a barrier to ion migration upstream. In particular, during operation of EHD fluid mover  310 , dielectric surfaces  393  accumulate charge (such as from positive ions generated at a corona discharge type instance of emitter electrode  391  or elsewhere). Because dielectric surfaces  393  do not provide an attractive path to ground, a net charge tends to accumulate and thereafter operate electrostatically to repel like charges. As a result, dielectric surfaces  393  are electrostatically operative as a barrier to upstream ion migration. Upstream dielectric surfaces  393  also tend to electrostatically mask any otherwise attractive paths to ground, such as may be provided by traces formed on PCB  361 , components affixed thereto, battery  367 , enclosure  309  or other electronic components not specifically shown, thereby shaping the previously described electric field in the primarily downstream direction toward collector electrodes  492 . 
     As with the collector electrodes  392 , dielectric surfaces  393  may be formed on the aforementioned surfaces or integrally therewith. In each case, by forming the electrostatically operative surfaces that define collector electrodes  392  and dielectric surfaces  393  as, or on, the aforementioned surfaces, EHD air mover  310  can be included within very limited interior spaces such as illustrated in  FIG. 3 . In some embodiments, one or more of the illustrated dielectric surfaces are provided as a polyimide film or tape, such as marketed by E. I. du Pont de Nemours and Company under the KAPTON trademark, affixed over respective portions of an EMI shield or an enclosure. 
     Note that, in some embodiments, at least a portion of the surface  308  on, or over, which the second, upper, instances of collector electrode  392  and dielectric field shaping surface  393  are formed may be configured to act as a heat spreader as well as an EMI shield. In some cases, such a heat spreader may optionally be provided with heat transfer fins  320  as depicted in  FIG. 3 . In such cases and depending on dimensional clearances, it may be desirable to provide a thermal buffer  307  (e.g., of closed-cell foam or other thermally insulative material) to avoid hot spotting on the exterior of enclosure  309  and to guide the EHD motivated fluid flow through heat transfer fins  320 . For generality, both ventilating and recirculating fluid flow paths are depicted, although based on the description herein, persons of ordinary skill in the art will appreciate that one, the other, or both of ventilating and recirculating flow paths may be provided in any given design. 
       FIGS. 5 and 6  depict cross-sectional views of additional variations on the described device configurations in which electrostatically operative portions of an EHD fluid mover are formed as, or on, respective surfaces of a device enclosure and/or Electromagnetic Interference (EMI) shield overlaying an electronic assembly. Whereas  FIG. 3  depicted a display surface as part of the device stack that includes an EHD fluid mover,  FIG. 5  depicts an alternative in which the dimension-setting device stack includes a PCB electronic assembly, with components affixed thereto, and EHD fluid mover positioned between opposing walls of enclosure  509 .  FIG. 6  depicts a further alternative configuration in one of the collector electrodes of the EHD fluid mover is provided using a trace formed on the PCB of an electronic assembly included within enclosure  609 . For ease of understanding, like features are depicted using reference numerals already described with reference to  FIGS. 3 and 4 . Based on that preceding description, persons of ordinary skill in the art will appreciate the variations depicted in  FIGS. 5 and 6 . 
     Laptop-Style Embodiments 
     Referring back generally to  FIGS. 7A ,  7 B and  7 C and the illustrative laptop-style, consumer electronics device  700  (and body portion  701 A) depicted therein, we now illustrate (in cross-section) by way of  FIGS. 8A ,  8 C,  9 A and  9 B, EHD air mover configurations in which electrostatically operative portions of the design are formed as, or on, a surface within the device enclosure. In some cases, at least one of the electrostatically operative portions is formed as, or on, an interior surface of the enclosure itself. In some cases, at least one of the electrostatically operative portions is formed as, or on, a surface of an EMI shield that overlays an electronics assembly such as a keyboard assembly or circuit board. In each case, by forming electrostatically operative portions as, or on, such surfaces, EHD fluid/air movers can be accommodated within very limited interior spaces. 
     For example, in consumer electronics devices such as illustrated in the  FIGS. 8A and 8C  cross-sections of body portion  701 A, total thickness d may be less than about 10 mm, with keyboard assembly  740  occupying a portion of the available vertical section. Recalling the plan view layout of  FIG. 7C , the illustrated cross-sections of  FIGS. 8A and 8C  allow the substantial entirety of the interior vertical section to accommodate EHD air mover  710 . On the other hand, analogous, but more tightly packed, vertical sections illustrated in  FIGS. 9A and 9B  accommodate EHD air mover  710  as well as printed circuit board (PCB) mounted integrated circuits, discretes, connectors, etc. occupying a substantial portion of the available interior space. As before, examples of PCB mounted integrated circuits include central processor units (CPUs), graphics processor units (GPUs), communications processors and transceivers, memory, etc., which can often generate a substantial portion of the devices heat load and which, in some embodiments, are cooled by the very EHD fluid/air movers that can be accommodated closely proximate to the heat sources (or thermally coupled fins/spreaders). 
     Turning first to the  FIG. 8A  cross-section, a pair of generally planar collector electrodes  792  is formed as, or on, opposing interior surfaces of base portion  701 A. More specifically, a first, lower instance of collector electrode  792  is formed on or as part of an interior surface of enclosure  709 . As before, in some embodiments, a conductive (e.g., metallic) tape or strip may be affixed to the interior surface of a generally non-conductive case or surface thereof and coupled to ground to define the first collector electrode instance. In general, the conductive tape or strip may be cut to a shape and extent desired for collector electrode  792 . Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) layer or region may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode  792 . In some cases, the grounded conductive layer or region may be, or may be formed integrally with, enclosure  709 . 
     A second, upper, instance of collector electrode  792  is likewise formed on or as part of an EMI shield  708  that isolates EHD air mover  710  from keyboard assembly  740 . A conductive (e.g., metallic) tape or strip may be affixed to an otherwise non-conductive exposed surface of EMI shield  708  and coupled to ground to define the second collector electrode instance. As before, the conductive tape or strip may be cut to a shape and extent desired for collector electrode  792 . Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) interior layer or region of EMI shield  708  may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode  792 . 
     Collector electrodes  792  and emitter electrode  791  are coupled between terminals of a high voltage power supply (not specifically shown, but as generally explained relative to  FIG. 4 ) to generate an electric field (and in corona discharge-type embodiments such as illustrated, the ions) that motivate air flow in a generally downstream direction. By way of example, emitter electrode  791  may, in some embodiments, be coupled to a positive high voltage terminal of a power supply (illustratively +3.5 KV, although specific voltages and, indeed, any supply voltage waveforms may be matters of design choice) while collector electrodes  792  are coupled to a local ground. Operation of EHD air mover  710  is substantially as described with reference to  FIG. 4 . 
     As with the collector electrodes, respective upper and lower instances of dielectric surfaces  793  are provided on, or as part of, a surface of EMI shield  708  or enclosure  709 . These dielectric surfaces are electrostatically operative and contribute to field shaping in the EHD fluid mover while also providing a barrier to ion migration upstream. In particular, during operation of EHD fluid mover  710 , dielectric surfaces  793  accumulate charge (such as from positive ions generated at a corona discharge type instance of emitter electrode  791  or elsewhere). As a result, dielectric surfaces  793  are electrostatically operative as a barrier to upstream ion migration. Upstream dielectric surfaces  793  also tend to electrostatically mask any otherwise attractive paths to ground, such as may be part of keyboard assembly  740 , battery  767 , enclosure  709  itself or other electronic components not specifically shown. In this way, dielectric surfaces  793  shape electric field established by EHD air mover  710  in the primarily downstream direction toward collector electrodes  792 . 
     Note that in the illustration of  FIG. 8A , a ventilating inflow  702  of air is drawn through apertures in keyboard assembly  740 .  FIG. 8B  depicts a partial underside view (from within the interior of EHD air mover  710 ) of apertures  796  in upper dielectric surface  793 . Although an exemplary array of circular apertures is illustrated, persons of ordinary skill in the art will appreciate that any of a variety of penetrations (and patterns thereof) through upper dielectric surface  793  may be provided to facilitate ventilating inflow  702 . It will also be appreciated that the above-described electrostatically operative accumulation of charge on dielectric surface  793  provides a barrier to migration of ions from EHD air mover  710  though the illustrated apertures and into keyboard assembly  740 . 
     In some embodiments, additional ion migration barriers may be provided. For example, in the illustration of  FIG. 8A , an additional ion repelling barrier  795  is introduced as a dielectric mesh, grid, grate or other air permeable curtain across a substantial upstream cross-section of the EHD motivated flow. As before, barrier  795  accumulates charge (such as from positive ions generated at a corona discharge type instance of emitter electrode  791 ) and operates as an electrostatic barrier to upstream ion migration. In the configuration illustrated, conductive paths  794  to ground are provided to capture ions that may nonetheless migrate upstream past barrier  795 . 
     In some embodiments, subassembly structure (not specifically illustrated in  FIG. 8A ) may be provided (e.g., to fix position of emitter electrode  791  and collector electrodes  792  with respect to each other).  FIG. 8C  provides an illustrative view of a cross-section through an illustrative exoskeletal structure  811  (e.g., a partial subassembly enclosure) that provides relative positional fixation of collector electrodes  792  and emitter electrode  791  with respect to each other. Note that fix points (e.g.,  812 ) for respective ends of emitter electrode  791  are necessarily out of view in the illustrated cross-section, but will be better appreciated based on the corresponding perspective cutaway view of  FIG. 8D . As before, electrostatically operative upper and lower dielectric surfaces  793  contribute to field shaping in the EHD fluid mover while also providing a barrier to ion migration upstream. However, in the variation of  FIG. 8C , these dielectric surfaces  793  lap over a portion of the illustrated exoskeletal structure  811  and conformably extend in an upstream direction where they (as before) are provided on, or as part of, an exposed surface of EMI shield  708  or enclosure  709 , respectively. Note that, in the perspective cutaway view of  FIG. 8D , only the lower one of the lapped-over electrostatically operative field shaping dielectric surfaces  793  is illustrated. In some embodiments, one or more of the illustrated dielectric surfaces are provided as a polyimide film or tape, such as marketed by E. I. du Pont de Nemours and Company under the KAPTON trademark, affixed over respective portions of an exoskeletal structure of an EHD subassembly, an EMI shield and/or an enclosure. 
     In the embodiments of  FIGS. 8A and 8C  and as before, given the very limited thickness that may be available to a thermal management solution within the interior of commercially desirable form factors, designs in which electrostatically operative surfaces such as a collector electrode or a field shaping, charge collecting surface are formed as, or on, an exposed surface tend to save precious millimeters of thickness that would otherwise be squandered in a more conventional design in which electrodes might be packaged within the walls of an EHD air mover subassembly. In this regard,  FIGS. 9A and 9B  illustrate variations on the designs just described in which (i) keyboard assembly  740 , (ii) EHD air mover  910  and (iii) a double-sided PCB  761  (with its affixed integrated circuits [multiprocessor  762 , memory  763 ], discretes  765  and connectors  766 ) are all accommodated within a device stack and volume at least partially bounded by enclosure  909 . 
     Although available interior volumes and tolerances are, in general, implementation and design dependent, it should be clear from the illustrations and description herein that a consumer electronics device may afford 5 mm or less of its total thickness d for EHD air mover  910 . In some embodiments (such as illustrated in  FIG. 9A ), heat transfer fins  920  are dimensioned to fit within the limited thickness provided. In some embodiments (such as illustrated in  FIG. 9B ), air flow paths may accommodate larger instances of heat transfer fins  920 . In each case, by forming the electrostatically operative surfaces that define collector electrodes  792  and/or dielectric surfaces  793  as, or on, the aforementioned surfaces, EHD air mover  910  can be included within very limited interior spaces as illustrated in  FIGS. 9A and 9B , respectively. 
     As before, and though omitted for simplicity of illustration, an exoskeletal structure (e.g., a partial subassembly enclosure) may provide relative positional fixation of collector electrodes  792  and emitter electrode  791  with respect to each other. In such cases, dielectric surfaces  793  (e.g., polyimide film or tape) may lap over a portion of the exoskeletal structure (not specifically shown, but recall  FIGS. 8C and 8D ) and conformably extend in an upstream direction where they are provided on, or as part of, a surface of an EMI shield  908 . 
     Television or Display Device Embodiments 
     Referring back generally to  FIGS. 10A ,  10 B and  11 A and the illustrative flat panel display device  1000  depicted therein, we now illustrate (in cross-section) by way of  FIGS. 11B and 11C , EHD air mover configurations for lower and upper portions of the display device in which electrostatically operative portions of the design are formed as, or on, surfaces within the device enclosure. In some cases, at least one of the electrostatically operative portions is formed as, or on, an interior surface of the enclosure itself. In some cases, at least one of the electrostatically operative portions is formed as, or on, a surface of an EMI shield that overlays an electronics assembly such as a display. In each case, by forming electrostatically operative portions as, or on, such surfaces, EHD fluid/air movers can be accommodated within very limited interior spaces. 
     For example, in flat panel display device  1000 , total depth d of cross-sections  11 B and  11 C, may be less than about 10 mm. Recalling the perspective view of  FIG. 11A  and the upper and lower instances of EHD air movers depicted therein,  FIG. 11B  illustrates cross-section  11 B in which a substantial entirety of the interior depth accommodates an instance of lower EHD air mover  1010 A.  FIG. 11C  likewise illustrates cross-section  11 C in which display surface  1001  and an instance of upper EHD air mover  1010 B are both accommodated within the depth of flat panel display device  1000 . In the illustrated bottom-to-top air flow, instances of upper EHD air mover  1010 B are accommodated in a volume behind display surface  1001  and, accordingly, electrostatically operative features thereof are more tightly packed than analogous features of lower EHD air mover  1010 A. Nonetheless, design and operation of the respective air movers are largely analogous. 
     In the case of EHD air mover  1010 A (see  FIG. 11B ), electrostatically operative surfaces may be formed (at least partially) over subassembly structure. As previously explained, an exoskeletal structure (e.g., a partial subassembly enclosure) may provide relative positional fixation of collector electrodes  1192  and emitter electrode  1191  with respect to each other. In such cases, dielectric surfaces  1193  (e.g., polyimide film or tape) may lap over a portion of the exoskeletal structure  1111  and conformably extend in an upstream direction where they are provided on, or as part of, a surface of an EMI shield  1109 . Alternatively (though not specifically shown in  FIG. 11B ) planar collector electrodes  1192  may be formed as, or more directly on, opposing interior surfaces of enclosure  1109 . 
     As with certain collector electrodes designs described herein for pad-type and laptop style devices, in some embodiments of flat panel display  1000 , a conductive (e.g., metallic) tape or strip may be affixed to the interior surface of a generally non-conductive case or surface thereof and coupled to ground to define each of the collector electrodes  1192 . In general, the conductive tape or strip may be cut to a shape and extent desired for collector electrode  1192 . Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) layer or region may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode  1192 . In some cases, the grounded conductive layer or region may be, or may be formed integrally with, enclosure  1109 . 
     For EHD air mover  1010 B (see  FIG. 11C ), a first instance of collector electrode  1192  is formed in any of the manners just described, while the second instance of collector electrode  1192  is formed on or as part of an EMI shield  1108  that isolates EHD air mover  1010 B from display surface  1001 . Exoskeletal structure of an EHD subassembly (though provided in some embodiments) is omitted for simplicity of illustration. As before, a conductive (e.g., metallic) tape or strip may be affixed to an otherwise non-conductive exposed surface of EMI shield  1108  and coupled to ground to define the second collector electrode instance. Also as before, the conductive tape or strip may be cut to a shape and extent desired for collector electrode  1192 . Alternatively, a non-conductive (e.g., dielectric) layer otherwise overlaying a grounded conductive (e.g., metallic) interior layer or region of EMI shield  1108  may be etched or otherwise selectively removed to expose a surface of the shape and extent desired for collector electrode  1192 . 
     For both EHD air mover  1010 A and EHD air mover  1010 B, respective instances of collector electrodes  1192  and emitter electrode  1191  are coupled between terminals of a high voltage power supply (not specifically shown, but as generally explained relative to  FIG. 4 ) to generate an electric field and (in corona discharge-type embodiment such as illustrated) the ions that motivate air flow in a generally upward downstream direction as illustrated. As in previously described pad-type and laptop-style designs, emitter electrode  1191  instances may, in some embodiments, be coupled to a positive high voltage terminal of a power supply (illustratively +3.5 KV, although specific voltages and, indeed, any supply voltage waveforms may be matters of design choice) while collector electrodes  1192  instances are coupled to a local ground. Operation of EHD air movers  1010 A and  1010 B is substantially as described with reference to  FIG. 4 . 
     As with the collector electrodes, opposing instances of dielectric surfaces  1193  are provided on, or as part of, an exposed surface of EMI shield  1108  or enclosure  1109 . These dielectric surfaces are electrostatically operative and contribute to field shaping in the respective EHD fluid mover while also providing a barrier to ion migration upstream. In particular, during operation of EHD air movers  1010 A and  1010 B, respective dielectric surfaces  1193  accumulate charge (such as from positive ions generated at a corona discharge type instance of emitter electrode  1191 ). As a result, dielectric surfaces  1193  are electrostatically operative as a barrier to upstream ion migration and tend to electrostatically mask any otherwise attractive paths to ground, such as enclosure  1109  itself or (particularly in the case of EHD air mover  1010 A) parts of display  1001  or other electronic components not specifically shown. In this way, respective dielectric surfaces  1193  shape the electric fields established by EHD air movers  1010 A and  1010 B in the primarily downstream direction (upward in  FIGS. 11A and 11B ) toward respective instances of collector electrodes  1192 . 
     Additional ion migration barriers may be provided. For example, in the illustrations of  FIGS. 11B and 11C , an additional ion repelling barrier  1195  is introduced as a dielectric mesh, grid, grate or other air permeable curtain across a substantial upstream cross-section of the EHD motivated flow. As before, barrier  1195  accumulates charge (again from positive ions generated at corona discharge type instances of emitter electrode  1191  or elsewhere) and operates as an electrostatic barrier to upstream ion migration. In the configuration illustrated, conductive paths  1194  to ground are provided to capture ions that may nonetheless migrate upstream past barrier  1195 . 
     Although available interior volumes and tolerances are, in general, implementation and design dependent, it should be clear from the illustrations and description herein that a thin flat panel display device may afford 5 mm or less of its total depth d for EHD air mover  1010 B or  1010 A. 
     In the configurations depicted, a unidirectional air flow entering ( 1002 ) at the bottom of flat panel display  1001  and exiting ( 1003 ) at the top thereof is provided and EHD air movers instances are positioned to motivate air flow for respective positions upstream of heat transfer fins  1120  thermally coupled to elongate edge positioned arrays of illumination sources (LED illuminators  1150 ) that generate a substantial portion of heat to be exhausted from enclosure  1109 . Although such flow and such positioning places EHD air mover  1010 B in the more tightly constrained depth behind display  1001 , it allows ozone reducing materials (e.g., ozone reducing catalyst or reactive material) to be placed downstream of both air movers on surfaces, such as the heat transfer fins  1120  themselves (or heat spreaders, LED illuminator assemblies, etc.) whose heated surfaces tend to increase efficacy of the ozone reduction. 
     Other Embodiments 
     While the techniques and implementations of the EHD devices discussed herein have been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the appended claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. Therefore, the particular embodiments, implementations and techniques disclosed herein, some of which indicate the best mode contemplated for carrying out these embodiments, implementations and techniques, are not intended to limit the scope of the appended claims.