WO2021053410A1

WO2021053410A1 - Gas monitoring device

Info

Publication number: WO2021053410A1
Application number: PCT/IB2020/056597
Authority: WO
Inventors: Vladimir Stavrov
Original assignee: Amg Technology Ltd
Priority date: 2019-09-17
Filing date: 2020-07-14
Publication date: 2021-03-25
Also published as: BG112997A

Abstract

The invention relates to a device for simultaneous determining the physical parameters, chemical composition and concentrations of the components of a gas flow and will find application in industry and everyday life, e.g. in HVAC systems to determine air quality or monitor other gas mixtures. By means of the device of the invention, more efficient monitoring of gases is carried out and comfort and safety are ensured. The device (1) consists of a body (3) in which a measuring chamber (11) is formed in which the sensors (12) are placed, having microcantilevers (13) with particular selectivity and sensitivity. It contains means for said simultaneous determination, each of which comprises selected microcantilevers (13) and at least one actuating element (14, 17), arranged in the common measuring chamber (11).

Description

GAS MONITORING DEVICE Description

Field of the Invention

This invention relates to a device for determining the physical parameters and chemical composition of a gas by means of measuring the flow of that gas. It will find application in industry and everyday life, e.g. HVAC systems to determine air quality or to monitor other gas mixtures. By means of the device from the invention, more efficient monitoring of gases is carried out, ensuring comfort and safety.

Background of the Invention

When monitoring air quality or gases in general, physical parameters, such as: pressure, gas flow, temperature, viscosity, thermal conductivity, particulates, etc., as well as the composition and concentrations of individual gas components are determined. Typically, each gas parameter is measured with a dedicated highly selective sensor. Thus, a measurement or monitoring system contains at least as many different sensors as the number of specified parameters. Individual sensors use different operating principles and different sensory elements. In addition, various technical means for detecting and processing sensory signals are used, thus complicating the calibration and measurement of multiple quantities necessary to obtain correct results. It is therefore natural, to seek to reduce the number of implemented measurement principles, preferably to a single one.

Specifically, for gas monitoring sensors, a gas flow supply is required. For this purpose, additional elements for a reproducible gas flow and supply to the sensors are exploited. As it is preferable to use minimal flows, thus small size sensors with high sensitivity are required. In addition, each of the specialized sensors are housed separately, and because of the presence of many such housings, additional volume is required, and the individual sensors measure the corresponding parameter in different spatial areas (points of measurement). Therefore, measures are to be taken to homogenize the measured flows or to use additional calculations to account for the spatial correlations between the signals that are measured individually. Therefore, those skilled in the art prefer to use sensor systems that ensure automatically coherence of the sensor signals and measure all parameters in a sufficiently small spatial area. Besides, correct determination of the chemical composition of a gas containing a large number of components with varying concentrations, is particularly challenging. There are various chemical sensors that provide the desired and/or required selectivity and sensitivity but they are slow to respond or saturate during prolonged operation. Such sensors are one way disposables or need to be periodically regenerated. This impacts negatively their applicability for monitoring and makes them more expensive.

In addition, the usage of specialized sensors requires prior knowledge of the chemical composition of the gases. In practice, the use of specialized sensors leads either to an uncertainty that all components will be measured and recorded, or to an unnecessary cost increase of the relevant systems when sensors for substances not contained in the gas under investigation are pre-included.

Therefore, although many alternative sensory methods exist for determining the chemical composition of a gas, only optical spectroscopy provides sufficiently high selectivity, sensitivity and accuracy. However, this method is relatively complex, expensive and unsuitable for continuous monitoring.

In practice, microcantilever sensors that operate in static mode are known as specialized gas monitoring sensors - their flexible elements bend or torsion as a result of the interaction with the measured gas, which generates an aperiodic sensor signal with a varying amplitude. Also known are microcantilever sensors that operate in a dynamic mode of oscillation, where their flexible elements are bent or torsion periodically, depending on the oscillation mode, while generating periodic sensor signals. The parameters of said oscillation, such as: phase, amplitude, resonant frequency and/or quality factor, named Q-factor, change as a result of the interaction of the flexible elements with the gas flow. Therefore, micro cantilever sensors are among the potential candidates for a universal sensor approach for the simultaneous determination of a manifold of physical and chemical parameters of gases.

Particular microcantilever sensors being used to measure various gas parameters, are known from the state of the art. These are disclosed, for example: in a dew point determination patent N° US6, 126,311 ; in a patent for a temperature measuring device US 7,928,343 B2; devices for detecting the presence of selected substances are disclosed in: patent EP2032976A1, patent application W02004083802A2, patent application US2006 / 0191320A1, patent US 8,481,335 B2 and others.

Despite its very high sensitivity and speed (usually <1 sec) for measuring a selected parameter or component of the gas composition, a significant disadvantage of a microcantilever sensor is the drift of the sensor signals associated with the dependence of the magnitude of said signal on multiple parameters, such as: temperature, humidity, pressure, electromagnetic fields, saturation of the sensor element etc. All these drawbacks limit their usability and increase the cost of measuring and monitoring of air or gas parameters by existing specialized microcantilever sensors. This applies respectively to the devices disclosed in the patents described above and the patent applications, which detect and measure a single parameter or are compensated for a single unmeasured (background) parameter of air or gas.

Therefore, it is preferable that the number of sensor signals is equal to, or greater than the number of parameters that determine the behavior of a microcantilever, and that the indivi dual signals are received from sensors with dissimilar selectivity for each of the parameters. Also known in the art are microcantilever sensors that are used as microphones, to record acoustic waves caused for instance, by selective light absorption. Examples of such sensors are the acoustic-optical sensors disclosed, in patents such as: US5,753,797 and US5, 933, 245, as well as patent applications: US2015/0101395A1 and US2018/0164215A1. The devices described in these documents are intended only to determine the chemical composition of gases, but the documents do not disclose how sensory signals distinguish the influence of other (e.g. physical) gas parameters.

Despite the availability of said sensors, there is still a need to create: sensors to determine different physical and chemical parameters using a common principle of operation with identical sensor elements, where each sensor must be able to respond selectively to one of the plurality of parameters. The sensors need to be small enough, fast (reaction time 1 - 10 sec) and to be located in the same small spatial area, to ensure both spatial coherence and correlation of signals in a system, while using minimum gas volume flows. It is preferable for the sensors to have a modular construction, allowing quick and easy configuration depending on the specific application and to contain elements to provide the transport of the gas flow and the processing of the sensor signals, without the need for regeneration.

Summary of the Invention

The present invention relates to a gas monitoring device, which consists of a body equipped with gas monitoring sensors, inlet and outlet elements for providing a gas flow. A measuring chamber is formed in the body in which the sensors are placed, having microcantilevers with particular selectivity and sensitivity. For activating the microcantilevers at least one actuating element is provided, and optionally microfluidic elements are formed in the sensors for modifying the gas flow. The device is combined to simultaneously determine the physical parameters and the chemical components of which the gas is composed and their concentration.

In one embodiment of the device from the invention, the total number of microcantilevers is equal to, or greater than the number of simultaneously determined parameters and components, and the microcantilevers have built-in piezoresistors connected into one or more identical or varied measuring configurations.

In another embodiment of the invention, the number of sensors in the device corresponds to the number of groups of parameters, the chemical components of the gas and their concentrations to be determined.

In another embodiment of the device of the invention, the actuating elements driving the microcantilevers are at least two, with at least one actuating element is designated to determine the physical parameters of the gas and is selected from electrothermal, piezo acoustic, electromagnetic element, and the other actuating element is an infrared beam to determine the chemical components and their concentration in the gas.

In a further embodiment, the means for determining the chemical components and their concentration in the gas consist of one or more microcantilevers and an actuating element an infrared beam, consisting of one or more monochromatic sub-beams with wavelengths corresponding to the absorption lines of each of the gas components A_k. The intensity of each sub-beam is modulated at a frequency equal to the resonant frequency of one of the dedicated microcantilevers, designed to simultaneously determine the respective components A_k. In another embodiment, the monochromatic beams are switched one by one in the actuating element infrared beam, with the microcantilever being only one.

In another embodiment, in the means for determining the physical parameters of the gas, the activating element for actuating the microcantilever is electrothermal and is formed as heating metal tracks on the microcantilever; or the actuating element is a piezo acoustic resonator. In an additional embodiment, at least one permanent magnet is set and accordingly oriented towards the metal tracks. In addition to this embodiment, the metal tracks on the microcantilevers are at least one pair and are arranged orthogonally to each other, and the attached permanent magnet is located at an angle a to one of the microcantilevers, in order to provide a predetermined ratio of sensor signals from the two selected orthogonal microcantilevers. In a subsequent embodiment, the means for simultaneously determining the physical parameters of the gas comprise of microcantilevers and at least two actuating elements selected from: an electrothermal actuator with heated metal tracks, a piezo acoustic resonator and metal tracks together with a permanent magnet. Short description of the figures

Fig. 1 shows a cross section of an embodiment of a device of the present invention;

Fig. 2a is a top view of an active carrier; Fig. 2b shows a top view of a spacer insert;

Fig. 2c shows a side view of an alternating active carrier and spacer inserts with a connector for sensor signals; Fig. 3a shows a top view of a conventional microcantilever sensor consisting of a rigid body and two active built-in piezoresistors;

Fig. 3b shows a top view of a sensor with a rigid body and four microcantilevers, with the piezoresistors connected in a measuring bridge configuration;

Fig. 3c shows a cross section of a sensor comprising a rigid body and a microcantilever; Fig. 4a shows a top view of a sensor with a frame-shaped rigid body comprising a microcantilever; Fig. 4b shows a top view of a sensor with a frame-shaped rigid body comprising two microcantilevers with resistors connected in a full bridge configuration;

Fig. 4c shows a longitudinal cross section of a sensor with a built-in micro fluidic element;

In Fig. 5 another cross-sectional view of the microfluidic element of a sensor mounted on a carrier is shown;

In Fig. 6, a cross section of a device of the invention consisting four micro cantilever sensors each with electrothermal actuation, is shown;

In Fig. 7, a cross section of a device of the invention consisting a single microcantilever sensor with electrothermal actuation is shown;

In Fig. 8a, a device of the invention comprising two microcantilevers sensors with a piezo acoustic resonator actuating element is shown;

In Fig. 8b, a top view of an active carrier with a piezo acoustic resonator mounted is shown; Fig. 8c is a top view of a spacer insert with an opening for a piezo acoustic resonator;

Fig. 9a is a view of a micro cantilever with a metal track in a longitudinal magnetic field;

Fig. 9b shows a microcantilever with a metal track in a transverse magnetic field;

Fig. 10a shows a longitudinal cross section of a device with two microcantilever sensors and a permanent magnet as an actuating element;

Fig. 10b is a top view of a spacer insert with various openings for permanent magnets;

Fig. 10c shows a top view of a spacer insert with openings for placing permanent magnets at an angle a;

Fig. 11 shows a cross section of an invention device comprising of three microcantilever sensors and two actuating elements: a piezo acoustic resonator and a permanent magnet.

Description of the Invention

The gas monitoring devices from the present invention are designed to simultaneously determine the physical parameters of gases and their chemical composition, as well as the concentration of the individual components. For this purpose, microsensors containing microcantilevers are used in the devices in the present invention. The use of microcantilever sensors in the invention results in the fact that the determination of certain physical parameters with the device from the invention, e.g. temperature, flow rate and the like, can be accomplished directly by measuring the signals provided by the microcantilevers of the sensors. To determine a different group of physical parameters or chemical composition of the gas, it is necessary to activate the microcantilevers of the sensors, e.g. by static or dynamic bending or torsion by an at least one actuating element. The devices of the present invention use in particular microcantilever sensors, and in terms of the required functions, each device is provided with two separate types of gas monitoring means: means for determining the physical parameters and means for determining the chemical composition and concentrations of the individual gas components. These means contain microcantilevers and actuating elements, through the optimal combination of which, the two complementary functions of the device are performed.

When a microcantilever sensor is used, and since a single sensor signal does not have absolute full selectivity for a selected gas parameter (as the sensor responds to many gas parameters simultaneously), it is necessary to measure simultaneously a sufficient number of independent sensor signals, while the values of all monitored parameters, including the value of the selected parameter are determined by calculation. The number and type of the said sufficient number of signals from a single device varies for each particular application and is determined by the preliminary information on the nature of the gas and the acceptable noise level.

In this invention, the gas monitoring device in each specific implementation can be considered as a superposition of multiple sensors, where each sensor provides sufficient sensor signals for autonomous determination of a preselected number and type of gas parameters with the desired accuracy.

In this sense, the devices of the present invention are combined. This is explained in further details in the examples which follow, and which are intended to illustrate the invention without limiting it.

In the present disclosure, the terms "sensor" and "microsensor" are used interchangeably. Examples

Example 1

This invention relates to a device 1 , for determining parameters and monitoring of a gas flow

2, as shown in Fig. 1 which shows a cross-sectional side view of device 1. After the measurement, the gas flow 2' is discharged from device 1 , which consists a body 3 equipped with an input element 4 and an output element 4', an insulated input connection 5 and/or an output connection 5'. By means of the connections 5 and/or 5’ and an additional external device, e.g. pump or fan (not shown in the Figure), a controlled gas flow 2 through device 1 is supplied.

In Example 1, body 3 comprises three flat active carriers 6.i (i = 1, 2, 3), each with one or more formed openings 7.i. In addition, body 3 also contains four spacer inserts 8 j (j = 1 , 2,

3, 4), which alternate with active carriers, each with a formed opening 9.j. The openings 7.i and 9.j may be of the same or different shape or of the same or different size. The outer size of each of the carriers and spacer inserts is in the range from 6 mm to 20 mm, preferably from 10 mm to 15 mm, in this example 12 mm The carrier’s thickness varies from 0.2 mm to about 5 mm, preferably from 0.5 mm to 1.5 mm, in this example it is 1.0 mm The input/output elements (4, 4') and the flat elements 6.i and 8.j are detachably connected, forming the body 3, e.g. with screws of suitable length and nuts 10 or in another manner known to those skilled in the art. Said elements: 4, 4', as well as the openings 7.i and 9.j together form a cavity - a common measuring chamber 11 , with a variable cross-section, the side walls of which are impermeable to the gas. The gas flow 2 passes through the chamber 11 , and the gas speed and pressure can be varied along its length, which can be used to achieve a local modulation in the gas flow mode (e.g. laminar-non-laminar, homogeneous- inhomogeneous, stationary, nonstationary) and accordingly, to locally modify the sensor sensitivity and selectivity.

The means for determining the physical parameters and chemical composition of the gas 2 include microsensors 12, and as in Example 1, one or more piezoresistive microcantilever sensors 12.m (m = 1, 2) mounted on the active carriers 6.i are the most preferred. Each of said sensors 12 comprises one or more microcantilevers 13.

In the present example, shown in Fig. 1, the said means for determining the physical parameters include microcantilevers 13.p located on two sensors 12.1 and 12.2, mounted on active carriers 6.1 and 6.3. When it is necessary to actuate the microcantilever 13.p, the means also include an actuating element 14, mounted on carrier 6.2, with the element being located in a specific opening 15 of a spacer insert 8.3. Since opening 15 is connected to opening 9.3, the actuating element 14 may also be located in the common measuring chamber 11. In this example, the actuating element 14 may be selected as any of: electrothermal, piezo acoustic etc., for example electrothermal, as explained in detail later in this description.

Separately, the means for determining the chemical composition of the gas 2 in Example 1 include: input/output elements 16 and 16', an infrared (IR) actuating element representing IR beam 17 and one or more microcantilevers 13.k of the sensor 12.1. The optically transparent input/output elements 16 and 16' allow infrared beam 17, provided by an external device (not shown in the Figure), to pass through the chamber 11. Typically, the intensity of beam 17 is modulated with frequency f) and provides actuation of the selected microcantilevers 13.k, as further explained in the example.

A top view of an embodiment of active carrier 6.i is shown in Fig. 2a. It is flat, with a square shape, and has a shaped periphery, which provides a multiple galvanically isolated contact terminals (pins) 18. The only opening 7.i is formed in the geometric center of the carrier, and around it is a mounting pad 19 for sensor 12.m or an actuating element 14 with electrical power supply and/or control pads, which usually are being metallized. The terminals of the sensor 12 are wire bonded to contact pads 20, which in turn are galvanically connected to contact pins 18 located on the periphery of the active carrier 6.i. Through them, each sensor signal is uniquely related to corresponding microcantilever 13 p/13 k which generates it, and all received sensor signals are fed to a corresponding device for processing, as it is common for the field.

Openings 21 are located in the four comers of the carrier and are used to configure the sensor body 3 of the device 1.

When the value determined by sensor 12 such as: transfer of substance or heat, dust particles, etc. is related to the vector of the gas flow 2, it is preferred that the sensor be positioned with an overlap relative to aperture 7.i. When the determined quantity is scalar or isotropic, such as: temperature, static pressure and the like, it is preferable for the sensor to be located in a way not overlapping the opening 7.i.

Fig. 2b shows a top view of the spacer insert 8.j (j = 1,2) embodiment, square shaped as well, with an opening 9.j formed in its geometric center. The size of opening 9.j may vary, being selected to accommodate the non-planar elements of a mounted sensor 12 or actuating element 14, on an adjacent active carrier 6.i. Said elements are usually arranged in an area ranging from 1 mm to about 5 mm, preferably from 1.5 mm to 4.0 mm, in the example 3.5 mm. The thickness of inserts 8.j exceeds the height of said non-planar elements and may vary in the range from 0.2 mm to 2 mm, preferably from 0.5 mm to 1 mm, for example 0.8 mm Optionally, concentric to the opening 9.j, an additional mounting element 22 is formed, for instance as a ring of conductive metal layer, a seal of elastic or a similar material. In the four comers of the insert 8.j coaxially openings 23 are formed, preferably with identical pitch to openings 21 of active carrier 6.i, which serve to assemble body 3.

Fig. 2c shows a cross section side view of an embodiment of an active carrier 6.i and two spacers 8.j. The sensor signals are transmitted by an electrical connector 24, the contact pins 24.1 of which provide a galvanic connection between the respective pins 18 of carrier 6.i and the flexible multicore cable 24.2. Thus, the electrical signals from sensor 12 are fed to an external system for processing (not shown in the Figures).

It is apparent to those skilled in the art, that more than one sensor 12.m can be mounted on an active carrier 6.i on which the openings 7.i are more than one. In addition, the dimensions and shape of the openings 9.j of the adjacent spacer insert 8j are such, that they can accommodate all non-planar elements of the sensors. Therefore, this example and the following examples do not limit the number of the sensors 12. m mounted on a single 6.i carrier.

A top view of a conventional piezoresistive single-cantilever sensor 12.m used in this embodiment of the invention is shown schematically in Fig. 3 a. The microcantilever sensor 12.m consists of a solid rigid body 25 with a rectangular shape and a single thin flexible microcantilever 13, which can be used both for monitoring the physical parameters and for determining the chemical components and their concentration in a gas flow 2. The microcantilever 13 has a thickness from 0.5 pm to about 10 pm, preferably from 1.5 pm to 6.0 pm, for example 4 pm. At its fixed end sensor elements piezoresistors 26 are built-in and they change the value of their resistance depending on the bending of the microcantilever 13. Typically, the piezoresistors 26 are connected by conductive tracks 27 in a differential bridge configuration, optionally together with other sensor or passive elements 26'. Also, optionally, an additional metal tracks 28 may be arranged on the surface of microcantilever 13, which are formed together with the conductive tracks 27 or separately from them. Tracks 28 can be used for various purposes, such as making a galvanic connection with a selected local area of the microcantilever 13.

The power supply and terminals of the bridge, as well as the metal tracks 28 are galvanically connected by means of additional wires (not shown in the Figure) to contact pads 20.

A top view of another example of this embodiment of the invention, when a microcantilever sensor with a solid rigid rectangular body 25 and four microcantilevers 13.1 - 13.N (N = 4) with varying dimensions is used, is shown in Fig. 3b. One piezoresistor 26 is built-in on each microcantilever, and the piezoresistors are connected in a bridge configuration by conductive tracks 27. Optionally, a metal track 28 can be additionally formed on selected microcantilevers.

Where necessary, the number of microcantilevers may be greater than four, the measuring bridge configurations may be varied. Accordingly, carrier 6.i is provided with contact pads 20, with their number providing independent connection of said differential bridge configurations and metal tracks.

In the present invention, the total number of microcantilevers 13.p and 13.k in device 1 is greater than or equal to the number of gas flow 2 parameters desired to be determined simultaneously.

Side view of a longitudinal cross section of the sensors of Fig. 3a and Fig. 3b, is depicted in Fig. 3c. When sensor 12. m is constructed as shown, the microcantilever 13 can be exposed to the flow 2 of the measured gas, without orientation restrictions, as illustrated schematically in Fig. 3c with the two opposite arrows. Additionally, the location of microcantilever 13 relative to the opening 7.i and including its slope, can be varied so as to optimize its selectivity and/or sensitivity.

In the most preferred embodiment of the invention, body 25 of the microcantilever sensor 12. m is in the shape of a rectangular frame, as shown in Fig. 4a, top view. In one aspect of this embodiment the microcantilever sensor 12.m consists of a rigid body 25 with a rectangular opening 29 formed in its upper surface, in which a thin flexible microcantilever 13 is located. Dimensions and thickness are similar to the previous embodiment, with piezoresistors 26 as sensor elements being built-in in an identical manner. Optionally, an additional metal track 28 can be placed on microcantilever 13.

A top view of another embodiment of device 1 of Example 1 is shown in Fig. 4b. The microcantilever sensor 12.m with a body 25 contains two microcantilevers 13.1 and 13.2 of different lengths located in the opening 29, in each microcantilever 13 two separate piezoresistors 26 are integrated, and the piezoresistors are connected in a differential bridge configuration with conductive tracks 27, and a common additional metal track 28 is provided.

Optionally, the number of microcantilevers and the number of piezoresistors in each of them may be varied, as well as the configuration of piezoresistors 26 into measuring differential bridges.

Each of so described microcantilevers 13 in sensors 12.m, can be used to obtain a sensor signal with an increased selectivity towards a physical parameter of gas flow 2, such as: temperature, flow, presence of dust particles, viscosity, thermal conductivity or similar parameters, or towards a component characterizing the chemical composition of the gas.

In order to achieve sensor signal selectivity towards different parameters of gas flow 2, in the present invention for each microcantilever 13 following characteristics can be varied: the shape of body 25 where it is located, shape, number and/or dimensions of the microcantilever itself, the location of built-in piezoresistors 26 and/or the way they are connected in a bridge configuration with conductive tracks 27, the morphology and/or the properties of additive and/or subtractive local structures on each of the two surfaces of the microcantilever, the location of microcantilever 13 in opening 29, as well as the implementation of other approaches to ensure the selectivity and sensitivity of the individual microcantilever 13, in response to a specific parameter of the gas flow 2.

Accordingly, the carrier 6.i is equipped with contact pads 20, with their number providing independent measurement of a sufficient number of sensor signals.

A longitudinal side view of a similar sensor is shown in Fig. 4c. In addition, on the rear surface of body 25 of the microcantilever sensor 12.m is located an additional opening 30, which in depth of the body is connected to the opening 29. Thus, unexpectedly and unplanned it turned out that when body 25 is in the form of a frame, in sensor 12.m, an additional microfluidic element 30 may be formed, which is usually of trapezoidal or rectangular cross- section, as shown in Fig. 5. When the element 30 is formed of single crystal silicon with orientation (100), the shape, as is known to those skilled in the art, is usually a truncated four- walled pyramid.

By varying the dimensions of microfluidic element 30, the dimensions of opening 9.j on spacer insert 8.j and opening 7.i on active carrier 6.i can be aligned with opening 29, where microcantilevers 13 are located. This particular embodiment of the invention is preferred, when it is desired to determine one or more parameters of the gas in vector dependence on gas flow 2, when it is necessary to obtain a specific distribution of said flow, or when this leads to improved specific sensitivity and/or selectivity. Microfluidic element 30, in addition to matching size, can be used to further change gas velocity and pressure in the area of a selected microcantilever 13. When desired, the location of a selected microcantilever 13 in the opening 29 may be varied as to optimize said selectivity and/or sensitivity, especially when the gas flow 2 is inhomogeneous. Preferably, by changing the orientation of the active carrier 6.i, the respective microcantilever sensor 12.m to be oriented relative to the flow of measured gas 2, as shown by the arrow in Fig. 4c - from the bottom to the top of the sensor. Due to the anisotropic properties of the monocrystal silicon material, microcantilevers 13 with integrated piezoresistors 26 can be oriented only in the direction shown in Fig. 3a, Fig. 3b, Fig. 4a and Fig. 4b or perpendicular to it. The sensors 12 can operate in static mode, with flexible microcantilevers 13 bending or torsion as a result of the interaction with gas flow 2, whereby a multiple aperiodic sensor signals with varying amplitude are generated. These sensor signals can be used to further amplify or compensate for the response of selected 12.m sensors in device 1 , thereby improving their selectivity and sensitivity.

Also, the sensors 12 can be actuated to operate in a dynamic mode when the flexible microcantilevers 13 oscillate in bending or torsion modes, whereby generating multiple periodic sensor signals.

Regardless of the implementation, when a plurality of micro cantilevers 13 whose piezoresistors 26 connected in a differential bridge are bent in phase, the bridge remains balanced and the sensor signal level is equal to "zero", usually equal to the background noise level. When microcantilever 13 resonates, its oscillation amplitude and phase change and therefore in dynamic mode, the bridge sensor signal differs from "zero", only at the resonance of a microcantilever.

To determine the chemical composition of a gas 2 with combined device 1 of the invention, the infrared actuating element - IR beam 17 is passed through chamber 11 through the two optically transparent elements: inlet 16 and outlet 16'. The beam 17 may be composed of one or more monochromatic sub-beams 17.k. Each sub-beam 17.k has a wavelength lk-, which corresponds to the absorption line of a certain gas 2 component A_k, such as: nitrogen, water, oxygen, carbon dioxide, various organic or inorganic components and the like.

When a monochromatic IR sub-beam 17.k with a wavelength passes through volume 11 between optical elements 16 and 16', part of the sub-beam 17.k is absorbed when the gas contains a component A_k which has a line of absorption identical to the wavelength X . This causes a local increase in temperature and pressure, and when modulating the intensity of the sub-beam 17.k with frequency f, an acoustic oscillation with the same frequency is generated in the gas. When the said frequency f corresponds to the resonant frequency / of a selected microcantilever 13.k, its oscillation amplitude is amplified, and a sensor signal is generated. Thus, an amplified signal amplitude from a microcantilever 13.k is an indication of the presence in the chamber volume 11 of a component yfr whose absorption line is equal to the wavelength _/.l of sub-beam 17.k with modulated intensity and frequency f =f . In all cases, the microcantilever oscillation amplitude is a measure of the concentration of substance A_k, which selectively absorbs light with a wavelength Thus, it unexpectedly turned out, that it is preferable for the surfaces of said microcantilevers 13.k to be passivated, in order not to interact with the gas components A_/ during measurement. In the described embodiment of the invention, the function of device 1 for determining the chemical composition and concentration of components, can be provided by means of including an IR beam 17 and microcantilevers 13.k, which respond to the acoustic waves in the gas 2 without interacting with its individual components. This allows the continuous operation of device 1, without regeneration, which is a decisive practical advantage.

Another advantage of the invention is, that microcantilevers 13 are located entirely within the volume of the common chamber 11 , thus automatically ensuring the spatial coherence of the multitude of sensor signals, while the body 3 acts as a housing, protecting the fragile microcantilever 13 throughout operation.

An unexpected advantage of the devices of the present invention is the established opportunity to (pre)determine the selectivity and sensitivity of each microcantilever 13 used in the device towards a particular parameter by selecting and matching characteristics of microcantilevers and of the elements of the device 1, such as: location of the active carrier 6 in body 3; number, shape and dimensions of the openings 7 in carrier 6; shape and size of the opening 9 of spacer insert 8; shape and dimensions of body 25 of sensor 12 and the dimensions of opening 29; shape and dimensions of microfluidic element 30; shape, dimensions, orientation and location of microcantilever 13 relative to the measured gas flow 2; global or local modification of the properties of each of the surfaces of the microcantilever, including its morphology; selection of the number, location and configuration of the built-in piezoresistors 26 and/or auxiliary resistors 26' in the differential measuring bridge; selection of the gas flow mode through the local vicinity of the microcantilever 13 placement; selection of the operating mode (static or dynamic) and oscillation mode in dynamic mode of microcantilever 13; presence of additional functional elements: heaters, contact pads, current measuring electrodes, etc.

The availability of various approaches to vary the selectivity and sensitivity of a microcantilever sensor 12 by modifying its design and location in device 1 allows such a device 1 to acquire a sufficient number of independent sensor signals, needed to accurately determine physical parameters, chemical composition and gas concentrations.

Example 2

In another preferred embodiment of this invention, shown in Fig. 6, device 1 for determining the parameters and monitoring of gas flow 2, contains four active carriers 6.i, each with a mounted sensor 12.1 - 12.4, as well as optical elements 16 and 16' for passing IR beam 17 through the measuring chamber 11.

Unlike device 1 as described in Example 1, beam 17 is composed of a plurality of monochromatic sub-beams 17.k, each with a distinct intensity modulation, and beam 17 is formed, for example, by using fiber optics and a mixer for the individual sub-beams 17.k. This embodiment makes it possible with device 1 to determine simultaneously components Ak of the gas flow 2. For this purpose, the number of monochromatic sub-beams used must be not less than the number of gas flow 2 components, with a microcantilever 13.k provided for each of them. Thus, the number of microcantilevers 13.k, which are simultaneously in resonance, is an indication of the number of gas components Ak, with their amplitudes corresponding to their concentration. Preferably, the micro cantilevers 13.k in a single sensor 12 device 1 are selected with different resonant frequencies f_Ck.

As in the embodiment described in Example 1, the means for determining the physical parameters of the gas flow 2 include at least as many microcantilevers 13.p as the desired number of simultaneously determined parameters. Additional metal tracks 28 are placed on microcantilevers 13.p, which in the present example perform the function of an actuating element 14 for bending or torsion those microcantilevers. The metal tracks 28 shown in detail in Fig. 3a, Fig. 3b, Fig. 4a and Fig. 4b, in this case are designed to be heated by an electric current. The thickness of the heated metal tracks 28 is between 0.1 and 5 pm, preferably in the range from 0.2 to 1 pm, depending on their composition. Preferably, the material of these elements is selected to have the highest possible coefficient of linear thermal expansion, such as: aluminum (Al), copper (Cu), gold (Au) etc. In this example, the metal is an 0.8 pm thick aluminum. Typically, the width of the elements is between 4 pm and 30 pm, preferably between 6 pm and 15 pm - and in this case 12 pm. Preferably, the heated metal tracks 28 are formed simultaneously with some of the other electrical connection elements 27. Similarly, the metal tracks 28 in Example 1 can also be used as heaters.

When an electric current flow through a heated metal track 28, the corresponding thin microcantilever 13.p bends caused by the difference of its coefficient of linear thermal expansion and the coefficient of the material of the metal track 28. When a periodic current of frequency f_e flows through the respective microcantilevers 13.p with an integrated heating metal track 28, they bend periodically at a said frequency. Accordingly, when a periodic current of varying frequency f_e flows, the microcantilevers bend at a frequency equal to or twice the instantaneous value of the frequency / of the flowing current. When the current also contains a non-periodic component, the double-frequency actuation can be eliminated. This phenomenon is well known to those skilled in the art and allows microcantilevers 13.p to be bent or torsion in a desired manner. Such actuation of microcantilevers is called electrothermal (ET).

It is also known, that when the frequency f_e of the pulse current through a heated metal track 28 is close to the resonant frequency f_cp of microcantilever 13.p, its bending amplitude increases by a value corresponding to its Q-factor. Therefore, the increased bending amplitude of microcantilever 13.p in a gas, observed for example as a disturbed voltage balance of a measuring bridge, is an indication that the actuating pulse current frequency f_e and the resonant frequency f_cp are close by value. Therefore, frequency / at which the maximum bending amplitude of a microcantilever 13.p is measured, observed as the maximum signal of a bridge balanced at rest, corresponds to its resonant frequency f_cp.

Upon interaction with gas 2 flowing through openings 7.i and 9.j and microfluidic element 30 towards microcantilevers 13.p, their bending and torsion change. Since the magnitude of the changes corresponds to the parameters of gas flow 2 in a specific way, these parameters can be determined.

In another embodiment of this invention, when the actuating pulse current f. is a sum of two or more currents with different frequencies f_ei, f , etc., microcantilevers 13.p with different resonant frequencies can be oscillated simultaneously with an increased amplitude. Accordingly, changes in the abovementioned oscillation parameters of more than one of microcantilevers 13.p can be determined simultaneously during their interaction with gas flow 2.

In addition, when the electric current has a non-periodic (including constant) component, the current can be used to fine-tune the parameters of the sensor signal from a selected microcantilever, such as setting the off-set voltage or achieving analog signal compensation when determining two or more different parameters of the gas flow 2 using two or more microcantilevers 13.p. Therefore, preferably, in the present invention, an additional metal track (a microheater) 28 is placed on each microcantilever 13.

Thus, in the device 1 shown in Fig. 6, the means for determining the physical parameters contain only microcantilevers 13.p with a heated metal track 28, which are suitable for both static and dynamic simultaneous determination of multiple parameters of the gas flow 2, the maximum number of which is equal to the number of said microcantilevers. Examples of such parameters are, like: flow of substances or heat, temperature, pressure, viscosity, thermal conductivity, humidity, presence and concentration of selected chemicals, etc.

In this embodiment, the surfaces of all microcantilevers can be modified so that the microcantilevers 13.k and 13.p do not adsorb any component of the gas flow 2.

In another preferred aspect of the same embodiment, the IR actuating element beam 17 is longitudinal to body 3, with input/output elements 4 and 4' being used as optical input/output 16 and 16'. In this embodiment, individual microcantilevers 13.k are located outside the optical path of beam 17. For this purpose, suitable shapes and sizes of openings 7.i and 9.j are selected, as it is customary in the field.

In the most preferred aspect of this embodiment, beam 17 is formed by a plurality of sub beams 17.k from narrow-spectrum solid-state or gas lasers with a fixed wavelength and beam 17 is formed through a separate modulator, e.g. using fiber optics.

Thus, it was unexpectedly found that device 1 shown in Fig. 6, comprising means for determining the chemical composition of gas 2, said device includes optical input 16 and output 16' for passing IR light beam 17, which is an IR actuating element composed of a discrete plurality of monochromatic sub-beams 17.k, each with a different wavelength and modulated intensity, is suitable for the simultaneous detection of multiple gas components A_/c. The number of microcantilevers 13.k corresponds to the number of said monochromatic laser sub-beams, the amplitudes of which are modulated with frequencies f_k, equal of the resonant frequencies f± of the respective microcantilevers 13.k.

This embodiment of the invention does not limit the number of microcantilevers 13.k and their orientation and in the XY plane.

In another particularly preferred embodiment of the present invention, the means for determining the chemical composition of gas flow 2 include at least two optically transparent elements - inlet 16 and outlet 16', an IR actuating element - an IR light beam 17, as illustrated in the example of Fig. 7, and a single microcantilever 13.k of the plurality of microcantilevers 13 located on a single microsensor 12.1. When the wavelength of beam 17 changes over time and its intensity is modulated with the frequency f, upon reaching the absorption line of component A_j of the gas, it absorbs light and causes acoustic oscillations. The oscillations can be measured with the said single microcantilever 13.k, provided that beam 17 is modulated with a frequency f corresponding to the resonant frequency f of the said single microcantilever.

When the wavelength l, of the beam changes with time and the amplitude of the beam is modulated with a frequency corresponding to the resonant frequency / of the selected microcantilever 13.k, the amplified amplitude of the sensor signal from microcantilever 13.k is an indication of the presence of component A, with an absorption line corresponding to the instantaneous value of the wavelength l,. Thus, this embodiment of the device 1 is suitable for sequential detection of numerous components A_h A, _/, ... of the gas flow 2.

In the most preferred embodiment of this invention, shown in Fig. 7, beam 17 is monochromatic, its wavelength (t) changes with time according to a known rule l /.((), and the means for determining the chemical composition contain a single microcantilever 13.k, wherein the intensity of the beam 17 is modulated with a frequency f corresponding to the resonant frequency f_cn of the said single microcantilever 13.k. Thus, when the wavelength /.(!) changes, multiple components A, of gas 2 can be registered sequentially.

In another embodiment of this invention, the monochromatic beam 17 is composed of a plurality of sub-beams 17.k from narrow-spectrum solid-state or gas lasers, each with a fixed wavelength l,. The beam is formed using fiber optics, a switch for selecting one of the lasers and a common intensity modulator of said lasers with a frequency f corresponding to the resonant frequency f_cn of single microcantilever 13.k, intended to determine the chemical composition of the gas 2.

In yet another embodiment of the invention, monochromatic beam 17 is obtained from a broad-spectrum source, e.g. a semiconductor laser and laser-coupled monochromator as known to those skilled in the art.

In the described embodiment of the invention, while the means for determining the chemical composition of gas flow 2 comprises only a single micro cantilever 13.k, the means for determining the physical parameters of the gas 2 may include a plurality of microcantilevers 13.p with microheaters 28, placed on the same microsensor 12.1. Such an instrument is suitable for sequential detection of multiple components A_/ of gases with a high degree of time and spatial coherence of the simultaneously measured sensor signals to determine the physical parameters, required to precise determination of each of the gas parameters. Example 3

In another embodiment of the invention shown in Fig. 8a, the microcantilever sensors 12.m are two: 12.1. and 12.2 and are mounted on two active carriers 6.1 and 6.3, with four spacer inserts 8.1 - 8.4. In addition, the microcantilevers of sensor 12.1 are part of the means for monitoring the chemical composition and for determining common physical parameters of gas flow 2, such as temperature, pressure and the like, and the microcantilevers of sensor 12.2 are part of the means for determining and monitoring specific physical parameters of the gas flow 2, e.g. viscosity, heat capacity and the like. A piezo acoustic (PA) resonator 31 is mounted on carrier 6.2, which used as an actuating element 14 for dynamic bending or torsion the micro cantilevers 13.p for determining the physical parameters, and an opening 32 is shaped on the spacer insert 8.3. for placing said resonator 31.

All microcantilevers 13 of sensor 12.1, not indicated in the figure, except one selected microcantilever 13.k, are designed to determine a common set of physical parameters of gas flow 2, while said 13.k, like in the previous example, is designed to determine chemical components of the gas flow 2 and their concentrations. The remaining microcantilevers 13.p (p ¹ k) of sensors 12.1 and 12.2 can be oscillated through acoustic oscillations of the gas 2 in chamber 11. The oscillations are created by an additional element 31, e.g. PA resonator 31 or other device with a similar function. For this purpose, a PA or other resonator 31 is mounted on the modified active carrier 6.2, as shown in Fig. 8b. Resonator 31 is partially mounted above the opening 7 and at a suitable voltage supply, it generates acoustic waves in the volume of the chamber 11. For this purpose, an additional opening 32 is formed on the spacer insert 8.3, which is connected to the opening 9 and whose overall dimensions are such, that the PA resonator 31 is housed without contact with the walls of the opening 32. Since the opening 32 is connected to the opening 9.3 of the insert 8.3, the resonator 31 is housed entirely in the common chamber 11 with a small volume, which increases the efficiency of acoustic oscillation of the gas.

Microcantilevers 13.p respond to acoustic waves by bending or torsion, and when the waves have a frequency f_a corresponding to the resonant frequency f_cp of any microcantilever 13.p, the related actuation amplitude is increased. However, there are no additional requirements for the spatial orientation of said microcantilevers to be imposed by the usage of PA resonator

31. Thus, by changing the frequency f_a of the generated acoustic waves, changes in the characteristics of the oscillation of each of the flexible microcantilevers 13.p can be determined, such as: resonance frequency, oscillation amplitude and phase, quality factor, with those changes being a result of the interaction of microcantilever 13.p with gas flow 2. Accordingly, changes in said characteristics can be determined through the interaction of microcantilever 13.p with components of the gas 2, which allows their use for their exact characterization.

It will be apparent to those skilled in the art, that when a PA resonator 31 is appropriately selected, it can provide acoustic oscillations in a desired frequency range. Preferably, a disk resonator with a minimum size and a central opening, is mounted symmetrically to opening 9.j. Including, the resonance frequency of microcantilever 13.k intended for determining the chemical components and the frequency range of resonator 31 can be selected so, that the resonator 31 optionally actuates or does not actuate microcantilever 13.k with a resonant amplitude. It is also clear, that when more than one resonator 31 are used, they simultaneously act on gas 2 in chamber 11 , frequency scanning can be accelerated and/or the acoustic actuation efficiency can be increased.

The location of one or more modified active carriers 6.i with PA resonators 31 in device 1 can be selected such as to further ensure maximum efficiency of their operation. Thus, a device 1 shown in Fig. 8a, comprising at least one modified carrier 6.i with a mounted PA resonator 31 or other source of acoustic oscillations and one or more spacer 8.j inserts with additional openings 32 for accommodating the resonator 31 , is suitable for actuating multiple, randomly oriented microcantilever 13.p. The small volume of the measuring chamber 11 provides increased efficiency of the acoustic energy transfer from resonators 31 to microcantilevers 13.p, as well as the time and spatial coherence of the sensor signals. Example 4

In another preferred embodiment of gas monitoring device 1 of the invention, the means for determining the physical parameters include a selected plurality of microcantilevers 13.p on which metal tracks 28 are formed for actuation through an external magnetic field B. In this example the metal tracks, together with the source of the magnetic field B , perform the function of actuating element 14 for actuating microcantilevers 13.p, in a manner independent of the composition of gas flow 2. Such microcantilevers are shown in Fig. 9a and Fig. 9b. The magnetic field B is created by e.g. a permanent magnet not shown in the figures. In order to actuate the microcantilevers, metal tracks 28 are shaped such that a current flow in them is in the range from 0.01 mA to 10 mA, preferably from 0.05 mA to 5 mA, without substantially heating the microcantilevers. It is common to call such microcantilevers actuation electromagnetic (EM).

When the current I(f_e) is aperiodic, including with a constant value, the bending of the microcantilever is aperiodic in a phase with the current. When the current I(f_e) is periodic with frequency f_e, and as shown in Fig. 9a or Fig. 9b, a microcantilever 13 p is located in a constant magnetic field ( B = const), it is exposed to periodic electromagnetic forces F(f_e) with frequency f_e, the direction and strength of which depend on the direction of the magnetic field B and the magnitude of the current I(f_e) .

In the example shown in Fig. 9a, when the magnetic field B lines are oriented longitudinally to the microcantilever 13.p, a Lorentz force F_c(f_e) perpendicular to the surface of the microcantilever is generated, which acts only on the area where the direction of metal track 28 is orthogonal to the direction of the magnetic field B lines. Accordingly, when the pulse current frequency I(f_e) changes, the microcantilever can be bent under the action of the said force F_c(f_e), the bending being of increased amplitude when the current frequency I(f_e) corresponds to the resonant bending frequency /±.

Alternatively, in the example shown in Fig. 9b, when the magnetic field lines are oriented transversely to microcantilever 13.p, a pair of Lorentz forces F_c(f_e) perpendicular to its surface are generated, both acting on the sections in which metal track 28 is oriented in a direction different from the direction of the magnetic field B. Such a pair of forces torsions microcantilever 13.p around its longitudinal axis. Accordingly, when the pulse current frequency I(f_e) changes, microcantilever 13.p is torsion periodically under the action of said force pair F_c(f_e), and when the current frequency / corresponds to the torsional resonance frequency / , the oscillation is with increased amplitude.

Thus, it was unexpectedly established, that the actuation efficiency of a microcantilever 13.p can be modulated by choosing its orientation relative to the magnetic field B. When it is desired to use bending modes, the most effective is a field oriented longitudinally to the selected microcantilever. When the goal is to use torsion modes - most effective is a field oriented perpendicularly (transversely) to microcantilever 13.p.

Accordingly, the use of an external magnetic field B allows the actuation of microcantilevers 13.p in different oscillation modes when the frequency of the pulse current I(f_e) is in correspondence to the resonant frequencies f_ck of bending or torsion.

Another important advantage of EM actuation of sensors 12 is, that the same oscillation amplitude can be achieved with an electric current I(f_e), with a value at EM actuation, depending on the value of the magnetic field B , being from 10 to above 30 times less than the current required for an ET actuation, reducing the undesired heating of microcantilevers 13.p and sensors 12 hundred or more times.

An embodiment of device 1 with EM actuation is shown in Fig. 10a. There are two active carriers, each of which is equipped with a sensor 12.m (m = 1, 2). The permanent magnetic field B is generated by a permanent magnet 33 located in an opening 34 formed in the spacer insert 8.3. A top view of such a spacer insert 8j is shown in Fig. 10b. In this case, the width w of opening 34 and the thickness d of the spacer insert are chosen to correspond to the dimensions of permanent magnet 33. Preferably, w ~ d, and the permanent magnet is designed in a cylindrical shape with a diameter approximately equal to and smaller than mentioned sizes w and d.

The openings 34 may be more than one and can be oriented in different directions, relative to the orientation of microcantilevers 13.p. When one opening 34 is oriented relative to two mutually perpendicular microcantilevers at an angle a other than 0° or 90° (with 0° < a < 90°), the corresponding permanent magnet 33 can be used to simultaneously actuate said microcantilevers, at the expense of reduced actuation force F_k(f_e). Thus, it was unexpectedly found that for every two orthogonal microcantilevers 13.p, oriented e.g. in the X and Y directions, even when it is desired to oscillate them with the same modes or bend them in static mode under the same current flow I(f_e), an angle a of an arrangement of magnet 33 with respect to the X direction can be determined, as shown schematically in Fig. 10c, such that the respective sensor signals have a selected ratio, including the same or different. This allows, for example, analog compensation of the amplitudes of the sensor signals from two or more microcantilevers 13.p when they selectively measure different parameters of gas flow 2. Alternatively, and where possible, such compensation can be provided also by changing the magnitudes of the currents I(f_e) through metal tracks 28.

Thus, device 1 shown in Fig. 10a, including a spacer insert 8.j with an opening 34 for accommodating a permanent magnet 33 is suitable both for actuating a multiple differently oriented microcantilevers 13.p with metal tracks 28 as well as for achieving desired ratios of sensor signals from them with multiply (> 100 times) reduced heating of the microcantilevers compared to the case when ET actuation was used. The location in the device 1 and the orientation of a modified spacer insert 8.j with mounted permanent magnets 33 in it, can be designed to provide a desired ratio of sensor signals from pre-selected EM-actuated microcantilevers.

When a DC with I_{e =} const flows through metal track 28, the corresponding microcantilever 13.p can be used for static measurement. When a periodic current I_e with frequency f. flows through a metal track 28, the corresponding microcantilever 13.p can be used to dynamically measure a gas flow 2 parameter. In this case, the actuation energy of microcantilevers 13.p can be reduced more than 100 times compared to ET actuation with a similar amplitude. All micro cantilevers 13 except one selected, e.g. 13.1 of sensor 12.1, are designed to determine common gas 2 parameters. Microcantilever 13.1 can be actuated using an IR actuating element - monochromatic IR beam 17 with a modulated intensity and a frequency f corresponding to its resonance frequency f_ci. Analogously to Examples 2 and 3, when the volume of chamber 11 contains a gas component yfr with an absorption line corresponding to wavelength of the beam 17, an amplified oscillation amplitude of microcantilever 13.1 is an indication of the presence of component A_k in gas 2. Thus, with a microcantilever 13.1, the concentrations of the specific chemical components of gas flow 2 can be determined sequentially, component-by-component, without direct microcantilever interaction. Therefore, such a sensor is suitable for continuous operation without regeneration. Example 5

Another embodiment of the present invention is shown in Fig. 11, where two different modes of actuating the microcantilevers 13 intended for determining the physical parameters of the gas 2 are used. Device 1 contains four active carriers 6.1 - 6.4 and six spacer inserts 8.1 - 8.6. Sensors 12.1., 12. 2 and 12.3 are mounted on active carriers 6.1., 6.3 and 6.4 respectively. A PA resonator 31 is mounted on carrier 6.2 and is placed in an opening 32 formed in insert 8.3. A permanent magnet 33 is mounted in opening 34 of the spacer insert 8.5.

When a constant electric current flows through the metal track 28 of microcantilevers 13, which are designed to be EM actuated, the current value can be selected such as to achieve the desired static values of sensor signals of the selected individual microcantilevers. Optionally, this adjustment is performed in the presence or absence of a gas flow 2.

At the same time, in the volume of chamber 11 the piezo acoustic resonator 31 generated acoustic waves with frequency f_a, and when alternating current with frequency f_e flows through metal tracks 28, microcantilevers 13 in addition are vibrated with this frequency. When said frequencies f_a and f_e have close or significantly different values, additional external elements may be used for heterodyne mixing and/or phase detection of said dissimilar frequencies, as is known to those skilled in the art. Thus, signal analysis with increased accuracy can be achieved, e.g. to precisely determine the amplitude, phase and oscillation frequency of a selected micro cantilever 13. Since device 1 contains two independent actuating elements, between which a beating can be generated or the phase difference between the acoustic wave and the EM oscillation of the microcantilever 13 can be determined, the oscillation characteristics of each microcantilever 13 can be determined with additionally increased accuracy.

It is apparent to those skilled in the art that said heterodyne mixing and/or phase detection with an actuating element 14 may also be applied to microcantilevers 13.k, which are actuated by an infrared beam 17 in Examples 1 to 4, without limitation.

The 12.m microsensors are multi cantilever ones, with each sensor providing signals for determining different groups of quantities. For example, optionally, the microcantilevers of sensor 12.1 and the PA resonator 31 can be designed such, that the sensor signals from this sensor alone are sufficient to determine a common set of physical parameters of gas flow 2 with the desired accuracy, regardless of the presence of a magnetic field. The microcantilevers of sensors 12.3 and the orientation of permanent magnet 33 can be selected such that their static and/or dynamic signals serve to accurately determine another set of specific physical gas parameters. Finally, a subset of microcantilevers 13.k of sensor 12.2 are prearranged to determine the chemical gas composition and the concentration of its components by actuation with an infrared beam 17. The other microcantilevers 13.p of sensor 122 are prearranged to determine specific physical parameters, such as: viscosity, thermal conductivity and alike, as necessary to further increase the accuracy of determination the said concentrations of gas 2 components. It will be apparent to those skilled in the art, that elements of each of the described embodiments of the invention may be freely combined into one sensor device 1. Preferably, each of the individual sensors 12.m comprises a plurality of microcantilevers 13, with the number and sensing elements providing the determination of a specific set of physical parameters and/or gas composition common to a field in industry or everyday life. This allows both quick and easy assembly of the device 1 for a specific application, as well as time and spatial coherence of a sufficient number of sensor signals, required for the accurate determination of gas parameters. A key advantage is the use of microcantilever sensors, that do not require regeneration and can operate continuously.

It is clear to those skilled in the art, that to determine the gas parameters, each of the described options for actuating microcantilevers - ET, PA and EM, can be used together with the IR beam or alone in arbitrary combinations.

Claims

1. A gas monitoring device, consisting of a body equipped with gas monitoring sensors, inlet and outlet elements for providing a gas flow, characterized in that a measuring chamber (11 ) is formed in the body (3), in which the sensors (12) are placed, having micro cantilevers

(13) with particular selectivity and sensitivity, whereby for activating the microcantilevers (13) at least one actuating element (14, 17) is provided, and optionally in the sensors (12) microfluidic elements (30) are formed for modifying the gas flow, wherein the device (1) is combined to simultaneously determine the physical parameters, the chemical components of which the gas is composed and their concentrations.

2. The device according to claim 1, characterized in that the total number of microcantilevers (13) is equal to, or greater than the number of simultaneously determined gas parameters and components, where microcantilevers (13) have built-in piezoresistors (26) connected in a single or several identical or varied measuring configurations. 3. The device according to claim 2, characterized in that the number of sensors (12) included in a device (1) corresponds to the groups of parameters and the chemical gas components and their concentrations, that are determined.

4. The device according to claim 3, characterized in that actuating elements (14, 17) for activating microcantilevers (13) are at least two, with at least one actuating element (14) being intended for determining physical gas parameters and is designated as an electrothermal, piezo acoustic or electromagnetic element, with the other actuating element being an infrared beam (17) for determining the chemical gas components and their concentration.

5. The device according to claim 4, characterized in that the means for determining the chemical gas components and their concentration consist of one or more microcantilevers

(13.k) with an actuating element being an infrared beam (17) consisting of one or more monochromatic sub-beams (17.k) with wavelengths lk- corresponding to the absorption lines of each of the gas components A_k, the intensity of each sub-beam (17.k) being modulated with a frequency equal to the resonant frequency of one of above mentioned microcantilevers

28 (13.k), designed for the simultaneous determination of the respective components A_k.

6. The device according to claim 5, characterized in that the monochromatic beams (17.k) are switched sequentially into the actuating element infrared beam (17), while the microcantilever 13.k is a single one. 7. The device according to any one of the preceding claims, characterized in that the means for determining the physical gas parameters comprise electrothermal actuating elements (14) for activating microcantilevers (13), being formed as metal tracks (28) on microcantilevers (13).

8. The device according to claim 6, characterized in that in the means for determining the physical gas parameters, the actuating element (14) comprises at least one piezo acoustic resonator (31) mounted in the body (3).

9. The device according to claim 6, characterized in that the means for determining the physical gas parameters incorporate an electromagnetic actuating element (14), which comprises metal tracks (28) on the microcantilevers (13) and at least one permanent magnet (33) mounted in the body (3 ) .

10. The device according to claim 9, characterized in that it contains at least one pair of microcantilevers (13) arranged orthogonally to each other, with a permanent magnet (33) arranged at an angle a with respect to one of said microcantilevers (13), all provided with metal tracks (28) for electromagnetic actuation to deliver a predetermined ratio of sensor signals from the selected orthogonal pairs of microcantilevers (13).

11. The device according to any one of the preceding claims, characterized in that the means for simultaneously determining the physical gas parameters incorporate microcantilevers (13) and at least two actuating elements (14) selected from: an electrothermal actuator heated metal tracks (28), a piezo acoustic resonator (31) and metal tracks (28) together with a permanent magnet (33).

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