Particle Sensors

Abstract

To solve challenges of the present disclosure.SOLUTION: According to an example aspect of the present invention, there is provided an apparatus comprising a microelectromechanical (MEMS) capacitor comprising two plates and a gap between the plates, a gas conveyor configured to cause a gas to flow through the gap, and readout circuitry configured to measure capacitance of the MEMS capacitor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to capacitance-based particle detection. [Background technology]

[0002] Poor air quality due to chemical and particulate pollutants is a major health risk in urban areas. According to the World Health Organization (WHO), exposure to air pollutants contributed to 7 million deaths in 2012, one-eighth of the total deaths worldwide. In addition to the effects of air pollutants on the human respiratory system, strong associations have been found between exposure to air pollution and cardiovascular disease and cancer, among other diseases.

[0003] The adverse health effects of airborne pollutants are manifold and depend on their composition and state (e.g., gaseous or solid). Therefore, monitoring of the various air pollutants, their concentrations and spatiotemporal distributions, not only on a global scale but also more locally on local and regional scales, is important to identify the location of pollution sources and the geographic extent of pollution. To measure the transport of pollutants and to predict the evolution of the spread of pollution, measurements may be performed frequently and preferably on a dense spatial grid.

[0004] Filter-based air pollutant monitoring involves using a filter that is selective for a particle size of interest. To estimate the concentration of particles in the air (or, more generally, gas), the filter may be evaluated for particulate matter trapped on the filter after exposure to air that traverses the filter.

[0005] Particulate contaminants come in a range of sizes. For example, smog particles may be considered to be in the range of 0.01-1 micrometers, fly ash 1-100 micrometers, pollen particles 10-100 micrometers, heavy dust 100-1000 micrometers, and cat allergens 0.01-3 micrometers. Thus, when using filters, it is possible to obtain an estimate of the distribution of particles of multiple particle sizes in a gas (e.g., air) by using a set of filters of different selectivity. The particle size distribution may include multiple estimates of particle concentrations of particular particle sizes in the gas. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the problems in the conventional techniques described above. [Means for solving the problem]

[0007] According to some aspects, the contrast of the independent claims is provided. Some embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided an apparatus including a micro-electro-mechanical (MEMS) capacitor including two plates and a gap between the plates, a gas transporter configured to induce a flow of gas through the gap, and a readout circuit configured to measure a capacitance of the MEMS capacitor.

[0009] Various embodiments of the first aspect may include at least one of the features in the following bulleted list: The gas conveyor includes at least one of a mechanism for generating a pressure differential across the gap and a thermophoresis device configured to generate a temperature gradient across the gap. A readout circuit is configured to detect a change in capacitance of the MEMS capacitor caused by a particle flowing through the gap with the gas. The MEMS capacitor contains multiple gaps connected in parallel, each with its own readout electronics. -Gap width is adjustable. The width of the gap can be adjusted by applying a voltage between the plates, generating an electrostatic force that causes movement of at least one of the plates. The gap width is 0.05 to 2.00 micrometers.

[0010] According to a second aspect of the present invention, there is provided an apparatus including at least one processing core and at least one memory including computer program code, the at least one memory and the computer program code configured, together with the at least one processing core, to cause the apparatus to at least: instruct a gas conveyor configured to cause a flow of gas through a gap between plates of a micro-electromechanical (MEMS) capacitor to convey gas through the gap; receive input from a readout circuit configured to measure a capacitance of the MEMS capacitor; and derive a particle concentration in the gas from the input.

[0011] Various embodiments of the second aspect may include at least one of the features in the following bulleted list: The gas conveyor includes at least one of a mechanism for generating a pressure differential across the gap and a thermophoresis device configured to generate a temperature gradient across the gap. The apparatus is further configured to allow the width of the gap to be adjusted. The apparatus is configured such that the width of the gap is adjusted by applying an adjustable voltage to the plates. The apparatus is configured to sequentially use a plurality of gap widths to obtain a particle size distribution of particles in the gas.

[0012] According to a third aspect of the present invention, there is provided a method comprising the steps of instructing a gas conveyor to cause a flow of gas through a gap between plates of a micro-electro-mechanical (MEMS) capacitor, receiving an input from a readout circuit configured to measure a capacitance of the MEMS capacitor, and deriving a particle concentration in the gas from the input.

[0013] Various embodiments of the third aspect may include at least one feature that corresponds to the features in the bulleted list above presented in relation to the second aspect.

[0014] According to a fourth aspect of the present invention, there is provided an apparatus comprising: means for instructing a gas conveyor configured to cause a flow of gas through a gap between plates of a micro-electro-mechanical (MEMS) capacitor to convey gas through the gap; means for receiving an input from a readout circuit configured to measure a capacitance of the MEMS capacitor; and means for deriving a particle concentration in the gas from the input.

[0015] According to a fifth aspect of the present invention, there is provided a non-transitory computer readable medium storing a set of computer readable instructions which, when executed by at least one processor, cause an apparatus to at least: direct a gas conveyor configured to induce a flow of gas through a gap between plates of a micro-electro-mechanical (MEMS) capacitor to convey gas through the gap; receive input from a readout circuit configured to measure a capacitance of the MEMS capacitor; and derive a particle concentration in the gas from the input.

[0016] According to a sixth aspect of the present invention there is provided a computer program arranged to cause the method according to the third aspect to be carried out. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 illustrates an example of a system in accordance with at least some embodiments of the present invention. [Diagram 2] FIG. 1 includes two plots in accordance with at least some embodiments of the present invention. [Diagram 3] FIG. 1 illustrates an example of a device capable of supporting at least some embodiments of the present invention. [Figure 4] FIG. 2 illustrates signaling in accordance with at least some embodiments of the present invention. [Diagram 5] 1 is a flow graph of a method in accordance with at least some embodiments of the present invention. [Figure 6] FIG. 1 illustrates a concept in accordance with at least some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A microelectromechanical (MEMS) capacitor may be used to detect particles in a gas flowing between the plates of the capacitor: a particle flowing through the gap between the plates of the capacitor causes a transient change in the capacitance of the capacitor, which can be detected by appropriate readout circuitry.

[0019] The thickness of the gap in the MEMS capacitance can be adjusted, which allows selectivity regarding the particle size that can pass through the gap. Specifically, particles with a diameter larger than the gap width cannot get through. By adjusting the gap thickness, the particle size distribution can be determined.

[0020] FIG. 1 illustrates an example of a system in accordance with at least some embodiments of the present invention. A MEMS capacitor 100 includes two plates 110, 120, which may be made of or coated with, for example, a metallic material. The plates 110, 120 are shown in FIG. 1 with a simple shape for the sake of brevity and clarity of the drawing, but need not be so simple. The MEMS capacitor 100 includes a housing 130 on which other elements of the MEMS capacitor 100 are mounted. The plate 120 is mounted to the housing 130 by a spring mount 140, which allows the spacing between the plates 110 and 120 to be adjusted, for example, by applying selectable bias voltages to the plates 110 and 120 to generate an electrostatic attractive force of selectable strength. The spring mount 140 is shown in FIG. 1 diagrammatically, and various mechanical spring mechanisms may be employed, or other manners may be employed to allow the spacing between the plates 110 and 120 to be adjusted, in addition or alternatively. The distance between plates 110 and 120 defines the width of the gap.

[0021] Although discussed primarily herein in terms of one gap and two plates, in general, MEMS capacitor 100 may include multiple gaps connected in parallel, each with its own dedicated readout electronics, and each gap sandwiched between two plates, and thus in this general form the number of plates may be three or more.

[0022] A readout circuit 150 is configured to measure the capacitance of the MEMS capacitor 100. The readout circuit 150 is capable of detecting relatively rapid changes in capacitance, as described later in this specification. The readout circuit 150 is operatively coupled to a controller 160 via a connection 156. In some embodiments, the connection 156 traverses the housing 130. The readout circuit 160 may be configured to measure the capacitance of the MEMS capacitor 100 by measuring the response of the MEMS capacitor 100 to a square wave or, for example, by resonance measurements as known in the art.

[0023] The controller 160 may be configured to record the capacitance measurement signal from the readout circuit 150. The controller 160 may further be configured to vary the gap width between the plates (e.g., by varying the bias voltage). The controller 160 may be configured to perform a series of measurements using the MEMS capacitor 100, the series of measurements including a number of measurements with different gap widths. The connection 161 may connect the controller 160 to another node, for example to the Internet of Things or a sensor network via the Internet. The connection 161 may be wired or at least partially wireless.

[0024] A gas conveyor 170 is configured to pass gas (e.g., atmospheric air) through the gap between the plates 110 and 120. For example, the gas conveyor may be configured to generate a pressure gradient across the length of the gap. The pressure gradient may be generated by at least one attached fan to create a lower pressure between the gas conveyor 170 and the gap and / or a higher pressure between the gas conveyor 170 and the gap as shown in FIG. 1.

[0025] Another possibility is to use thermophoretic forces, also called thermal diffusion, which create a temperature gradient across the length of the gap, causing the gas to flow through the gap. The width of the gap is the separation between plates 110 and 120, but the length of the gap is perpendicular to the separation, and as the gas flows along the length of the gap, it flows from one side of MEMS capacitor 100 to the other, passing through the gap separating plates 110 and 120. A temperature gradient may be created across the length of the gap, which may be done, for example, using a heatable grid or plate.

[0026] Existing particle detection schemes are generally bulky (i.e., non-portable) and expensive, with their price range in the tens of thousands of euros, whereas on-chip solutions offer several advantages over existing solutions, such as small size, low cost, and low power consumption. The key to realizing a sensor network for air quality monitoring is a small particle sensor platform that can be formed by embedding sensors in the basic infrastructure or even mobile devices. Air quality data can be collected along with pressure information and reported to (for example) a cloud service for forecasting and / or monitoring air quality. The forecast can further enable an early warning system for air pollution levels. Mobile particle sensors can also act as personal dosimeters to measure the cumulative exposure of particulate hazards. Such a sensor network would have a large social and economic impact by reducing mortality and healthcare costs. For example, a user would respond to an alarm about particle pollution by wearing a protective mask.

[0027] In use, the gas transporter 170 pushes or pulls the gas 102 (e.g., air) into or out of the gap between the plates 110 and 120 while the readout circuitry 150 measures the capacitance of the MEMS capacitor 100. When a particle is transported through the gap, the capacitance of the MEMS capacitor 100 changes. In other words, the capacitance of the MEMS capacitor 100 is different depending on whether there is only gas or gas and particles in the gap. The transient change in capacitance may be seen as a particle passing through the gap. In fact, when a particle is between the plates, the capacitance transiently increases. This is because the dielectric constant of the particle is generally greater than that of the air.

[0028] The readout circuitry 150 or controller 160 may be configured to assign an estimated size to a particle passing through the gap based on the magnitude of the transient effect on the capacitance. The width of the gap defines an upper limit on the diameter of a passing particle. A mapping from the magnitude of the transient change in capacitance to an estimate of particle size may be prepared. This mapping may be prepared experimentally or from first principles before measurements are performed. Since the gap in a real MEMS capacitor 100 may be relatively narrow (on the order of 0.1 to a few micrometers), the probability of two particles being in the gap at the same time is considered to be relatively low, thereby making the counting of individual particles more reliable.

[0029] During the measurements, the controller 160 can compile statistics on the number and size of particles passing through the gap. As mentioned above, an estimate of the size of each particle may be made based on the gap width and the magnitude of the change in capacitance.

[0030] The controller 160 may be configured to perform a series of measurements at various gap widths, for example starting with a narrow gap and then widening the gap width, or starting with a wide gap and then narrowing the gap width, etc. This type of measurement may be useful in deriving a particle size distribution of particles present in a gas (which may be air, for example) since the gap width acts as a natural cutoff for particle size.

[0031] To perform a series of measurements, controller 160 may first cause the gap between plates 110 and 120 to be an initial width and then collect measurements sufficient to characterize the concentration in the gas of particles that manage to pass through the gap when the gap is at the initial width. Controller 160 may then cause the gap to be a second width (e.g., wider than the initial width) and collect measurements sufficient to characterize the concentration in the gas of particles that manage to pass through the gap when the gap is at the second width.

[0032] Increasing the gap width will make it possible to identify transient changes in capacitance caused by particles that were too large to be present in the earlier measurements made when the gap was narrow. This is because the larger the particle, the larger the change in capacitance. Thus, particles that have already been accounted for in measurements using a narrow gap width can be removed from the statistics when using a wide gap width, which can help derive a size distribution of the particles.

[0033] The controller 160 may be configured to dynamically determine when to terminate a measurement using a particular gap width. For example, the controller 160 may determine that sufficient data has been collected to characterize particles at a particular gap width when a preset number of particles are detected to have passed through the gap. The gap width may then be changed, or the series of measurements may be terminated if the series only involves one measurement at one gap width. For example, 40-80 particles may be sufficient. Alternatively or additionally, the measurement may be terminated after a preset time during which the measurement is valid. For example, if there are no or very few particles in the gas, it may be difficult or even impossible to detect the preset number of particles.

[0034] To calculate the particle concentration, the controller 160 may have an estimate of the amount of gas passing through the gap, which may be known in advance from a table of gas flow rates as a function of gap width when using a gas conveyor 170.

[0035] FIG. 2 includes two plots according to at least some embodiments of the present invention. In the top plot, the relative change in capacitance is plotted against particle size. The vertical axis is the relative change in diameter and the horizontal axis is particle size. The width (G) of the gap between the plates is 1 micrometer. The height (H) of the plates is 2 micrometers and the width (W) of the plates is 10 micrometers. Both axes are logarithmic. For example, the relative change in capacitance caused by a 0.2 micrometer diameter particle is 1...4×10 -4 while the relative change in capacitance caused by a 0.9 micrometer particle is 3×10 -2 …1×10 -1 It is.

[0036] In the plot below, particle frequency is plotted against particle concentration. The vertical axis shows frequency on a logarithmic scale, while the horizontal axis shows particle concentration in micrograms per square meter, also on a logarithmic scale. The top curve represents 0.1 micrometer diameter particles, the middle curve represents 0.5 micrometer diameter particles, and the bottom curve represents 1 micrometer diameter particles. The plate and gap dimensions are the same as in the plot above, and the gas velocity is 1 meter / second. As the plot shows, the expected particle count is mostly less than one particle per second, with only the smallest particles reaching about five particles per second at the highest concentration. Considering the size of the MEMS capacitor and the gas velocity of 1 m / second, it is expected that even under these conditions, it would be rare for two particles to be present in the gap at the same time.

[0037] FIG. 3 illustrates an example of a device that can support at least some embodiments of the present invention. Device 300 is shown, which may include, for example, controller 160 of FIG. 1. Device 300 includes processor 310, which may include, for example, a single-core processor or a multi-core processor, where a single-core processor includes one processing core and a multi-core processor includes two or more processing cores. Processor 310 may generally include a controller. Processor 310 may include two or more processors. Processor 310 may be a controller. The processing core may include, for example, a Cortex-A8 processing core manufactured by ARM Holdings, or a Steamroller processing core manufactured by Advanced Micro Devices Corporation. Processor 310 may include at least one Snapdragon processor manufactured by Qualcomm and / or an Atom processor manufactured by Intel. Processor 310 may include at least one application specific integrated circuit (ASIC). The processor 310 may include at least one field programmable gate array (FPGA). The processor 310 may be a means for performing method steps in the apparatus 300. The processor 310 may be configured to perform actions, at least in part, by computer instructions.

[0038] The device 300 may include a memory 320. The memory 320 may include a random access memory and / or a permanent memory. The memory 320 may include at least one RAM chip. The memory 320 may include, for example, a semiconductor memory, a magnetic memory, an optical memory, and / or a holographic memory. The memory 320 may be at least partially accessible to the processor 310. The memory 320 may be at least partially included in the processor 310. The memory 320 may be a means for storing information. The memory 320 may include computer instructions that the processor 310 is configured to execute. If computer instructions configured to cause the processor 310 to perform a particular action are stored in the memory 320 and the entire device 300 is configured to operate at the direction of the processor 310 using the computer instructions from the memory 320, the processor 310 and / or at least one of its processing cores may be considered to be configured to perform said particular action. The memory 320 may be at least partially included in the processor 310. The memory 320 may be at least partially external to the device 300 while still being accessible to the device 300 .

[0039] The apparatus 300 may include a transmitter 330. The apparatus 300 may include a receiver 340. The transmitter 330 and the receiver 340 may be configured to transmit and receive information, respectively, according to at least one cellular or non-cellular standard. The transmitter 330 may include two or more transmitters. The receiver 340 may include two or more receivers. The transmitter 330 and / or the receiver 340 may be, for example, It may be configured to operate in accordance with Global System for Mobile Communications (GSM), Wideband Code Division Multiple Access (WCDMA), 5G, Long Term Evolution (LTE), IS-95, Wireless Local Area Network (WLAN), Ethernet, and / or Worldwide Interoperability for Microwave Access (WiMAX) standards.

[0040] The device 300 may include a user interface (UI) 360. The UI 360 may include at least one of a display, a keyboard, a touch screen, a vibrator configured to cue a user by vibrating the device 300, a speaker, and a microphone. A user may be able to operate the device 300 from the UI 360, for example, to configure a particle detection measurement.

[0041] The processor 310 may comprise a transmitter configured to output information from the processor 310 via electrical conductors in the device 300 to other devices included in the device 300. Such a transmitter may comprise a serial bus transmitter configured to output information to the memory 320 via at least one electrical conductor, for example, for storage in the memory 320. Instead of a serial bus, the transmitter may comprise a parallel bus transmitter. Similarly, the processor 310 may comprise a receiver configured to receive information from other devices included in the device 300 at the processor 310 via electrical conductors in the device 300. Such a receiver may comprise a serial bus receiver configured to receive information from the receiver 340 via at least one electrical conductor, for example, for processing in the processor 310. Instead of a serial bus, the receiver may comprise a parallel bus receiver.

[0042] The device 300 may further include devices not shown in FIG. 3. For example, if the device 300 includes a smartphone, the device 300 may include at least one digital camera. Some devices 300 may include a rear camera and a front camera, where the rear camera may be for digital photography and the front camera may be for video calling. The device 300 may include a fingerprint sensor, where the fingerprint sensor is configured, at least in part, to authenticate a user of the device 300. In some embodiments, the device 300 lacks at least one of the above-mentioned devices.

[0043] The processor 310, memory 320, transmitter 330, receiver 340, and / or UI 360 may be interconnected in various ways by electrical conductors within the device 300. For example, each of the above-mentioned devices may be individually connected to a master bus within the device 300, which allows for information exchange between the devices. However, as will be appreciated by those skilled in the art, this is merely an example, and embodiments may choose to interconnect at least two of the above-mentioned devices in various ways without departing from the scope of the present invention.

[0044] 4 illustrates signaling according to at least some embodiments of the present invention. On the vertical axis, on the left side, there is the MEMS capacitor 100 of FIG. 1, in the middle, there is the control device 160 of FIG. 1, and on the right side, there is an independent control authority CTRL, which may correspond to, for example, the meteorological agency or the civil defense control center. Time progresses from top to bottom.

[0045] In phase 410, the control authority CTRL requests measurements from the control device 160. Phase 410 may include issuing instructions to the control device 160 for a series of measurements of the requested type. In response, the control device 160 commands the MEMS capacitor 100 to perform measurements with a first gap width between the plates 110 and 120. The gap width may be identified in phase 420. Alternatively, phase 420 may include the control device 160 controlling the MEMS capacitor 100 to achieve a desired gap width between the capacitor plates. Phase 430 includes the MEMS capacitor 100 performing the measurements requested in phase 420. Once the measurement results with the first gap width are obtained, the MEMS capacitor 100 returns the results to the control device 160 (phase 440). Then, in phase 450, the control device 160 commands the MEMS capacitor 100 to perform measurements with a second gap width between the plates 110 and 120. Phase 460 includes MEMS capacitor 100 performing the measurements requested in phase 450. Once the measurement results for the second gap width are obtained, MEMS capacitor 100 returns the results to control device 160 (phase 470). Although two measurements are shown in FIG. 4, three or more measurements may be requested and performed. Once the results of the series of measurements are obtained, control device 160 reports them to management authority CTRL (phase 480).

[0046] 5 is a flow graph of a method according to at least some embodiments of the present invention. Each phase of the illustrated method may be implemented in device 110, an auxiliary device, or a personal computer (for example), or may be implemented in a controller configured to control the functions thereof when installed therein.

[0047] Phase 510 includes instructing a gas conveyor to induce a flow of gas through a gap between the plates of a microelectromechanical (MEMS) capacitor. Phase 520 includes receiving an input from a readout circuit configured to measure a capacitance of the MEMS capacitor. Finally, phase 530 includes deriving a particle concentration in the gas from the input.

[0048] Regarding air gap capacitance:

[0049] The detector in Figure 6 consists of two electrodes with air (or another gas) blown into the gap between them. The top of the figure shows a perspective view of the detector without a particle in the gap, and the bottom of the figure shows a diagram of the detector with a particle of size d in the gap. A particle in the gap changes the capacitance, which is calculated for a cubic particle in the device of Figure 6. The particle dielectric constant ε γ The model is particularly accurate when is close to 1 and the gap G is narrow.

[0050]

number

[0051] This is plotted in the upper diagram of Figure 2. The magnitude of the capacitance change, ΔC, is roughly proportional to d 3…4 Since the capacitance change is proportional to , it is a measure of particle size. If the relative resolution of the capacitance change is ΔC / C0 = 100 ppm, the minimum detectable particle size d is approximately 0.1 μm.

[0052] Air gap detectors are characterized by their slow operation: the average frequency of particle transport through the channel is

[0053]

number

[0054] where v is the gas flow velocity, p is the mass density of the particles, dV / dt=vWG is the volumetric flow rate of air, m is the mass concentration of the particles, and M=pd 3 is the mass of the particle, and N=m / M is the particle number density. This is plotted in the lower panel of Figure 2, where p=2000kg / m 3 , dV / dt=10 -11 m 3 The condition / s may apply.

[0055] One way to increase the frequency of the signal pulses is to increase the pressure difference across the detector. This will increase the gas velocity but also shorten the signal pulses. For the conditions in the lower diagram of Figure 2, the pulse duration is τ = H / v = 2 μs, which benefits from a faster performance for the measurement electronics.

[0056] Because the particle-induced pulses are relatively short, a wide bandwidth is used: modest values ​​of U=10V, T=300K, B=1MHz (center drive frequency 10MHz), C=0.09fF, and Q=1000 limit the noise to ΔC=0.00048 aF or ΔC / C=5.5ppm.

[0057] If several gaps are connected in parallel, the total capacitance becomes large, which reduces the relative capacitance resolution. To ensure the relative resolution, every gap may be provided with its own dedicated readout electronics. This can be achieved, for example, by integrated readout electronics.

[0058] It is to be understood that the disclosed embodiments of the invention are not limited to the particular structures, process steps, or materials disclosed herein, but extend to equivalents thereof as would be recognized by one of ordinary skill in the art. It is also to be understood that the terminology used herein is used only for the purpose of describing particular embodiments, and is not intended to be limiting.

[0059] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment. For example, when a numerical value is referenced using a phrase such as about or substantially, the exact numerical value is also disclosed.

[0060] As used herein, a number of items, structural elements, compositional elements, and / or materials may be present in common lists for convenience. However, these lists should be construed as if each element of the list were individually identified as a separate and unique element. Thus, the individual elements of such lists should be construed as de facto equivalents of any other elements of the same list solely based on their presence in a common grouping, unless otherwise indicated. Furthermore, various embodiments and examples of the invention may be referenced herein in conjunction with alternatives with respect to their various components. It should be understood that such embodiments, examples, and alternatives should not be construed as de facto equivalents of each other, but should be considered as separate and independent manifestations of the invention.

[0061] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the above description, various specific details are set forth, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the present invention. However, one of ordinary skill in the art will recognize that the present invention may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring aspects of the present invention.

[0062] While the above-described embodiments illustrate the principles of the present invention in one or more specific applications, it will be apparent to those skilled in the art that various changes in form, usage, and details of the embodiments may be made without the exercise of the inventive faculty and without departing from the principles and concepts of the present invention. Accordingly, the present invention is not intended to be limited except as by the claims that follow.

[0063] In this document, the verbs "to comprise" and "to include" are used as open limitations that do not exclude or require the presence of unrecited features. Features recited in the dependent claims may be freely combined with each other, unless expressly stated otherwise. Furthermore, it is to be understood that the use of "a" or "an", i.e. the singular, does not exclude a plurality throughout this document. [Appendix 1] a microelectromechanical (MEMS) capacitor including two plates and a gap between the plates; a gas conveyor configured to induce a flow of gas through the gap; a readout circuit configured to measure a capacitance of the MEMS capacitor; An apparatus comprising: [Appendix 2] 2. The apparatus of claim 1, wherein the gas conveyor includes at least one of a mechanism for generating a pressure differential across the gap and a thermophoresis device configured to generate a temperature gradient across the gap. [Appendix 3] 3. The apparatus of claim 1 or 2, wherein the readout circuitry is configured to detect a change in capacitance of the MEMS capacitor caused by particles flowing through the gap with the gas. [Appendix 4] 4. The apparatus of any one of claims 1 to 3, wherein the MEMS capacitor comprises multiple gaps connected in parallel, each gap having dedicated readout electronics. [Appendix 5] 5. The apparatus of any one of claims 1 to 4, wherein the width of the gap is adjustable. [Appendix 6] 6. The apparatus of claim 5, wherein the width of the gap is adjustable by applying a voltage between the plates to generate an electrostatic force causing movement of at least one of the plates. [Appendix 7] 7. The apparatus according to any one of claims 1 to 6, wherein the gap has a width of 0.05 to 2.00 micrometers. [Appendix 8] 1. An apparatus comprising at least one processing core and at least one memory containing computer program code, the at least one memory and the computer program code acting in conjunction with the at least one processing core to perform at least: directing a gas conveyor configured to induce a flow of gas through a gap between plates of a microelectromechanical (MEMS) capacitor to convey the gas through the gap; receiving an input from a readout circuit configured to measure a capacitance of the MEMS capacitor; deriving a particle concentration in the gas from the input; and and causing the device to: Device. [Appendix 9] 9. The apparatus of claim 8, wherein the gas conveyor includes at least one of a mechanism for generating a pressure differential across the gap and a thermophoresis device configured to generate a temperature gradient across the gap. [Appendix 10] 10. The apparatus of claim 8 or 9, further configured to allow a width of the gap to be adjusted. [Appendix 11] 11. The apparatus of claim 10, configured to adjust the width of the gap by applying an adjustable voltage to the plates. [Appendix 12] 12. The apparatus of any one of claims 8 to 11, configured to sequentially use a plurality of gap widths to obtain a particle size distribution of particles in the gas. [Appendix 13] directing a gas conveyor to induce a flow of gas through a gap between the plates of a microelectromechanical (MEMS) capacitor; receiving an input from a readout circuit configured to measure a capacitance of the MEMS capacitor; deriving a particle concentration in the gas from the input; The method includes: [Appendix 14] 14. The method of claim 13, wherein the gas conveyor includes at least one of a mechanism for generating a pressure differential across the gap and a thermophoresis device configured to generate a temperature gradient across the gap. [Appendix 15] 15. The method of claim 13 or 14, further comprising the step of causing a width of the gap to be adjusted. [Appendix 16] 16. The method of claim 15, wherein the step of causing the width of the gap to be adjusted includes causing an adjustable voltage to be applied to the plates. [Appendix 17] 17. The method of any one of claims 13 to 16, further comprising the step of sequentially using a plurality of gap widths to obtain a particle size distribution of particles in the gas. [Appendix 18] means for directing a gas conveyor configured to induce a flow of gas through a gap between plates of a microelectromechanical (MEMS) capacitor to convey the gas through the gap; means for receiving an input from a readout circuit configured to measure a capacitance of the MEMS capacitor; means for deriving a particle concentration in the gas from the input; An apparatus comprising: [Appendix 19] When executed on at least one processor, at least directing a gas conveyor configured to induce a flow of gas through a gap between plates of a microelectromechanical (MEMS) capacitor to convey the gas through the gap; receiving an input from a readout circuit configured to measure a capacitance of the MEMS capacitor; deriving a particle concentration in the gas from the input; and A non-transitory computer-readable medium storing a set of computer-readable instructions that cause an apparatus to perform the steps of: [Appendix 20] A computer program configured to perform the method according to at least one of claims 13 to 17. [Industrial Applicability]

[0064] At least some embodiments of the present invention have industrial application in particle detection. List of Acronyms MEMS microelectromechanical Reference Code List 100 MEMS Capacitors 110, 120 Plate of MEMS capacitor 100 130 Housing 140 Spring mount 150 Readout circuit 160 Control device 156, 161 Connection 170 Gas conveyor 102 Gas 300~360 Components of the device in Figure 3 410-480 Phases of the method in Fig. 4 510-530 Phases of the method in Fig. 5

Claims

1. A microelectromechanical (MEMS) capacitor (100) including two plates (110, 120) and a gap between the plates (110, 120); a gas conveyor (170) configured to induce a flow of gas through the gap; a readout circuit (150) configured to measure the capacitance of the MEMS capacitor (100); the readout circuit (150) is configured to detect a change in capacitance of the MEMS capacitor (100) caused by particles flowing through the gap with the gas; The width of the gap is adjustable. Device.

2. The apparatus of claim 1 , wherein the gas conveyor (170) includes at least one of a mechanism for generating a pressure differential across the gap and a thermophoresis device configured to generate a temperature gradient across the gap.

3. The apparatus of claim 1 or 2, wherein the gap width is between 0.05 and 2.00 micrometers.

4. directing (510) a gas conveyor to induce a flow of gas through a gap between the plates of a microelectromechanical (MEMS) capacitor; receiving (520) an input from a readout circuit configured to measure a capacitance of the MEMS capacitor, the change in capacitance of the MEMS capacitor being caused by particles flowing through the gap with the gas; and deriving (530) a particle concentration in the gas from the inputs; The width of the gap is adjustable. method.

5. The method of claim 4 , wherein the gas conveyor includes at least one of a mechanism for generating a pressure differential across the gap and a thermophoresis device configured to generate a temperature gradient across the gap.

6. The method of claim 4 or 5, further comprising the step of: cycling through a plurality of gap widths to obtain a particle size distribution of particles in the gas.

7. A computer program arranged to cause the method according to claim 4 or 5 to be carried out.

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