JP2012220454A - Detection sensor and substance detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection sensor and a substance detection system detecting a substance at a high detection efficiency.SOLUTION: A sensitive film 42 is cooled in order to adsorb component molecules onto the sensitive film 42 while the sensitive film 42 is heated in order to desorb the component molecules from the sensitive film 42. When the component molecules are adsorbed onto the sensitive film 42 of an oscillator 41, the oscillation frequency of the oscillator 41 varies and, in a control unit 54, a variation amount of its sensor signal is continuously measured. When this variation amount falls below a predetermined threshold value, it is determined that detection reaches a saturated state. Then, a preset heater voltage is applied to a heater 90 incorporated in the oscillator 41 to cause the component molecules adsorbed onto the sensitive film 42 to be desorbed therefrom.

Description

  The present invention relates to a detection sensor and a substance detection system capable of detecting a substance such as VOC (Volatile Organic Compounds).

  Conventionally, there are sensors for detecting the presence of various substances and odors in the air, or their quantitative concentrations. In this sensor, the presence or absence of a specific substance or the concentration thereof is detected by adsorbing a specific type of molecule contained in the gas and detecting the presence or absence or the amount of adsorption.

A sensor element that detects molecules floating in the air by their minute molecular mass vibrates the vibrator in a gas containing these molecules, and the mass change of the vibrator when molecules are attached or adsorbed to the vibrator surface Is detected as a change in the vibration characteristics of the vibrator.
As a vibrator that performs mass detection in this way, there is a cantilever type vibrator that utilizes the vibration of a cantilever (see, for example, Patent Document 1). Such a cantilever type vibrator is manufactured in a micrometer (micrometer) unit area by using a technology called MEMS (Micro Electro Mechanical Systems) that precisely processes a silicon thin film or the like by photographic technology (photolithography). It has become possible to do. By reducing the size of the vibrator, the mass of the vibrator is greatly reduced, and the detection sensitivity for the attached mass is improved.

  A vibrator made of a silicon material uses the piezoresistive effect to detect a change in the frequency of the vibrator by detecting a voltage change in a piezoresistive layer provided on the surface of the vibrator (for example, Patent Documents 1 and 2) reference.). There is also a method for detecting the mass of a substance attached to the surface of the vibrator using a change in the resonance frequency of the vibrator (see, for example, Patent Document 3).

  By the way, the mass sensor using the cantilever type vibrator only detects the mass of molecules attached to the vibrator, and does not have a function of analyzing and discriminating the attached substance. Therefore, the function of identifying the adhering substance is to detect the change in the vibration frequency of the vibrator when the substance (molecule) is adsorbed to the detection film by using the adsorption selectivity of the detection film applied on the surface.

JP 2001-56278 A JP 2009-133772 A JP 2005-148062 A

By the way, in order to repeat the measurement, it is necessary to repeatedly perform the adsorption of the molecule on the detection film and the desorption of the molecule adsorbed on the detection film. In order to increase the measurement efficiency, it is preferable to perform adsorption and desorption in as short a time as possible.
When molecules are adsorbed on the detection film, the adsorption efficiency varies depending on the temperature.
In addition, for desorption of molecules adsorbed on the detection film, a method of flowing a clean gas such as nitrogen gas or air is used as a standard method for using and evaluating chemical sensors. It takes time to release.
The present invention has been made based on such a technical problem, and an object thereof is to provide a detection sensor and a substance detection system with high detection efficiency for detecting a substance.

The present invention based on such an object includes a vibrator having a beam shape in which one end portion or both end portions are fixed to a substrate and whose vibration characteristics are changed by attaching or adsorbing a substance having a mass to a sensitive film. A cooling unit that cools the sensitive film, a strain sensor that detects vibration of the vibrator, a heating part that heats the sensitive film, a piezoelectric element that vibrates the vibrator, an element package that applies a voltage to the piezoelectric element, A cooling unit and a control unit for controlling the heating unit, and the control unit cools the sensitive film by the cooling unit when the component molecules contained in the gas are adsorbed to the sensitive film, and the component molecules adsorbed on the sensitive film are removed. Control is performed so that the sensitive film is heated by the heating unit when desorbing from the sensitive film.
In this way, when desorbing the component molecules from the sensitive membrane, the sensitive membrane can be heated for desorption in a short time. Further, when the component molecules are adsorbed on the sensitive film, the adsorption can be efficiently performed by cooling the sensitive film in the cooling section. Furthermore, the sensitive film heated at the time of desorption can be cooled.

By the way, when molecules are adsorbed by the detection film, the optimum temperature for adsorption varies depending on the type of molecule, the type of detection film, and the like. Also, the time required to adsorb molecules can vary as well. The technique described in the above-mentioned patent document is only at an experimental level, and as described above, the optimum adsorption temperature and adsorption time are not grasped, and the practicality is poor.
Furthermore, in addition to detecting the presence or absence of specific types of molecules, when trying to detect the presence or amount of various molecules, multiple cantilever-type vibrators are provided, and multiple types of detection films are installed. Each cantilever type vibrator is applied, and the difference in adsorption selectivity between the detection films provided on the respective vibrators is used. In such a case, there is a possibility that the optimum adsorption temperature and adsorption time differ for each type of detection film. As a matter of course, it takes time to obtain the optimum adsorption temperature and time in advance for each type of detection film. In addition, when a detection sensor is configured by appropriately combining a plurality of types of detection films, the optimal adsorption temperature and time are programmed in advance in the controller that controls the operation of the detection sensor according to the type of detection film provided in the detection sensor. It is necessary and this is troublesome.
Therefore, it further includes a detection unit that detects the vibration frequency of the vibrator detected by the strain sensor,
The control unit may be characterized in that when the amount of change in the vibration frequency per unit time of the vibrator detected by the detection unit becomes equal to or less than a predetermined threshold value, the heating unit heats the sensitive film.
As described above, when the amount of change in the vibration frequency per unit time of the vibrator detected by the detection unit becomes equal to or less than a predetermined threshold value, the sensitive film is heated by the heater to desorb the component molecules from the sensitive film. I did it. That is, the adsorption is stopped and the desorption is started when the adsorption of the component molecules to the sensitive film is almost saturated. As a result, detection is possible not only with the type of sensitive film but also with an optimum adsorption temperature and time.

  The detection unit can detect at least one of the type and concentration of the substance obtained based on the change timing of the vibration frequency of the vibrator.

A storage unit that stores cooling characteristics and heating characteristics for each type of sensitive film is further provided, and the control unit corresponds to the type of sensitive film based on the cooling characteristics and heating characteristics of the sensitive film stored in the storage unit. The cooling of the sensitive film by the cooling unit and the heating of the sensitive film by the heating unit can be controlled.
Thus, for each type of sensitive film, the cooling characteristics such as the cooling temperature and the heating temperature, and the heating characteristics can be preset in the storage unit.

Here, it is preferable to use any one of porous metal complex (MOF), polybutadiene (PBD), polyacrylonitrile-butadiene (PAB), polyisoprene (PIP), and styrene-butadiene copolymer (PSB) as the sensitive film. .
To increase the sensitivity of the detection sensor,
1) A material having excellent adsorption characteristics (that is, a large K factor) is used.
2) Use under conditions that maximize adsorption characteristics (eg temperature).
3) Increase efficiency using sensor materials with fast adsorption / desorption response.
4) Increase sample gas volume.
5) Reduce short-time fluctuations in frequency.
However, 3) is limited in measurement conditions, and 3) or 4) is determined by electrical or physical limits of the detection period. Therefore, the detection sensor of the present invention uses a material having excellent adsorption characteristics (i.e., a large K factor) of 1). In particular, as a material having particularly excellent adsorption characteristics, it is preferable to form a porous metal complex on the cantilever surface and use it as a sensitive film. This MOF has high adsorption ability at low temperatures, but has poor desorption properties.
Therefore, when the sensitive film is made of a porous metal complex, the controller heats the sensitive film to 60 ° C. or higher for MOF and 40 ° C. or higher for the MOF when the component molecules are desorbed from the sensitive film. preferable.
When the sensitive film is made of a porous metal complex, the control unit preferably keeps the temperature of the sensitive film at 10 to 25 ° C. by the cooling unit during detection.
In addition, PAB and PBD have a high adsorption ability at a relatively low temperature such as 0 to 20 ° C. and good response characteristics. Therefore, in order to provide selectivity for various gases, when a plurality of cantilever type vibrators are used, MOF, PBD, PAB or the like is applied to the plurality of vibrators. In the combination of these materials and gas selectivity, the temperature of the sensitive film at the time of detection is preferably set to an optimum temperature from 0 to 25 ° C.
In this way, the vibrator can be used under conditions that maximize the adsorption characteristics.

  The strain sensor uses a piezoresistance effect of a resistance element, and the heater is preferably formed using the same constant resistance as the strain sensor. Thereby, a strain sensor and a heater can be formed in the same process.

  Here, by incorporating a heater composed of a P-type semiconductor resistor into a cantilever type vibrator, the temperature of the vibrator can be increased by 30 to 50 ° C. above room temperature. This makes it possible to adsorb at a low temperature and accelerate the desorption by instantaneously raising the surface of the vibrator at the time of desorption.

  Alternatively, a piezoelectric element may be bonded to one surface side of the element package, a substrate having a vibrator may be stacked and bonded to the piezoelectric element, and a cooling unit may be provided on the other surface side of the element package. .

In the present invention, two or more vibrators may be provided, and the two or more vibrators may be provided with sensitive films made of different materials.
At this time, the detection unit detects the response characteristics of the sensor with respect to the frequency change of the vibrator with the temperature at the time of detection being two or more conditions, and based on the difference in frequency change at the temperature of two or more conditions, One can also be estimated.

  The present invention is a substance detection system that detects at least one of the type and concentration of a specific substance contained in a gas to be detected, and introduces the gas to be detected into the system and transports the introduced gas in the system. Pump, an adsorption part for adsorbing a specific substance contained in the gas introduced into the system by the pump, a first heater for desorbing the specific substance adsorbed by the adsorption part from the adsorption part, and one or both ends A vibrator having a beam-shaped portion fixed to a substrate, having a sensitive film that adsorbs or adheres to a specific substance desorbed from the adsorbing part, and a vibration frequency that is changed by adsorbing or adhering the specific substance to the sensitive film; A strain sensor that detects vibration of the vibrator, a cooling unit that cools the sensitive film, a second heater that is provided in the vibrator and heats the sensitive film, a piezoelectric element that vibrates the vibrator, and a piezoelectric element The device package that applies voltage to the strain sensor, the heater, and the cooling unit are controlled, and when the component molecules contained in the gas are adsorbed to the sensitive film, the sensitive film is cooled by the cooling unit, and the component molecules adsorbed to the sensitive film are removed. When detaching from the sensitive film, a control unit that heats the sensitive film with a heater, and a change in the vibration frequency of the vibrator is detected from the vibration of the vibrator detected by the strain sensor, and the change timing of the vibration frequency of the vibrator A detection unit that detects at least one of the type of the specific substance obtained based on the above and the concentration of the specific substance obtained based on the amount of change in the vibration frequency, and the control unit includes a transducer that is detected by the detection unit. When the amount of change in vibration frequency per unit time falls below a predetermined threshold, the sensitive membrane is heated by a heater to desorb component molecules from the sensitive membrane. It may be a material detection system.

  Here, the vibrator is preferably provided in a chamber into which the specific substance desorbed from the adsorption unit is sent by a pump.

  According to the present invention, when the component molecules are adsorbed to the sensitive film, the sensitive film is cooled in the cooling unit, and when the component molecules are desorbed from the sensitive film, the sensitive film is heated to shorten the time. Can efficiently adsorb and desorb component molecules. Thereby, the detection efficiency for detecting the substance can be increased.

It is a figure which shows the structure of the substance detection system in this Embodiment. It is a figure which shows the structure of a detection sensor. It is a figure which shows the structure of a metal organic structure. It is sectional drawing and a perspective view which show the drive and cooling mechanism of a vibrator | oscillator. It is a figure which shows the flow of a detection. It is a photograph which shows a metal organic structure. It is a figure which shows the X-ray-diffraction measurement result of a metal organic structure thin film and powder. It is a figure which shows the concentration dependence of the frequency change in the sensitive film | membrane which consists of a metal organic structure and PBD. It is a figure which shows the adsorption | suction characteristic with respect to various substances of a metal organic structure. It is a figure which shows the vibration frequency variation | change_quantity according to the temperature of a metal organic structure. It is a photograph which shows the metal organic structure thin film formed on the cantilever type vibrator. It is a SEM image of the metal organic structure thin film formed on the cantilever type vibrator. It is the figure which showed the adsorption capacity with respect to acetone, toluene, octane, and ethanol of PAB, PBD, PSB, and PS as a function of temperature. (A) is a figure which shows the voltage-current characteristic of the heater incorporated in the cantilever type | mold vibrator, (b) is a figure which shows the shift of the resonant frequency by heater heating. It is a figure which shows the temperature profile of the heater of a concentration tube. It is a figure which shows a frequency change when propanol, toluene, and xylene are detected with the sensitive film | membrane.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a diagram for explaining the overall configuration of a substance detection system 10 in the present embodiment.
The substance detection system 10 shown in FIG. 1 adsorbs specific types of molecules to be detected, thereby detecting the presence or absence (occurrence) of the gas itself or a plurality of types of specific substances or odors contained in the gas, or The concentration is detected.
The substance detection system 10 sucks in a gas to be detected contained in a sample container 15 and generates a gas flow in the system, an adsorption unit 30 that adsorbs the gas sucked in the pump 20, and an adsorption Based on the detection sensor 40 that adsorbs a specific type of molecule contained in the gas component from the gas adsorbed by the unit 30 and outputs a detection signal corresponding to the adsorption of the molecule, And a measurement processing unit (detection unit) 50 that measures the presence or absence of the species of molecules or the amount thereof.

The adsorbing unit 30 is filled with, for example, carbon fiber as an adsorbing body inside a cylindrical cylindrical body 31 made of stainless steel, for example. Of course, other adsorbents can be used as appropriate. The gas discharged from the pump 20 is sent into the cylinder 31 and comes into contact with the adsorbent so that the component molecules in the gas are adsorbed to the adsorbent by physical adsorption with low selectivity.
A sheath heater 34 is wound around the outer peripheral surface of the cylindrical body 31. By applying a voltage to the sheath heater 34, the component molecules adsorbed on the adsorbent are desorbed, and the component molecules are conveyed to the detection sensor 40 by the flow generated by the pump 20.

As shown in FIG. 2, the detection sensor 40 includes a vibrator 41 that generates mechanical vibrations, and a sensitive film 42 that is formed on the surface of the vibrator 41 and adsorbs the molecules desorbed by the adsorption unit 30.
The vibrator 41 is a cantilever type having a width of 20 to 400 μm, a length of 100 to 1000 μm, a base end portion fixed, and the other end portion being a free end.
The vibrator 41 uses, for example, a piezoelectric drive system using a piezoelectric element as a drive source, and vibrates the vibrator 41 at a predetermined frequency. The vibrator 41 includes a vibration detection unit 44 for detecting a change in its own vibration state (vibration frequency) as an electric signal. The vibration detector 44 can be realized by, for example, a P-type semiconductor piezoresistive element.

The vibrator 41 is provided with a heater (heating unit) 90 using a thin film resistor. The heater 90 is formed by a resistor using a P-type semiconductor that is created at the same time that the piezoresistive element that constitutes the vibration detection unit 44 is created.
The sensitive film 42 is formed on the heater 90. And the temperature of the sensitive film | membrane 42 is adjusted automatically by controlling the electricity supply to the heater 90 by the control part 54 so that the characteristic of the sensitive film | membrane 42 may be drawn out best.

  The sensitive film 42 has a property of adhering or adsorbing a gas to be detected, but is a metal organic structure (MOF), polybutadiene (PBD), polyacrylonitrile-butadiene (PAB), polyisoprene (PIP), polystyrene (PS). ) Has a selectivity for selectively adhering or adsorbing a specific gas, which has been clarified by studies by the present inventors. In addition, examples of materials that can be employed as the sensitive film 42 include metal complexes such as phthalocyanine derivatives and porphyrin derivatives, conductive polymers such as polythiophene and polyaniline, and inorganic materials such as a titanium oxide porous film.

  Polyacrylonitrile-butadiene (PAB) has selectivity for gases such as octane and propanol. Polybutadiene (PBD) and polyisoprene (PIP) have selectivity for toluene. Polystyrene (PS) has selectivity for n-propanol and ethanol.

Metal-organic structures (Metal-Organic Frameworks, hereinafter abbreviated as MOF) are materials having a three-dimensional structure formed by bonding organic ligands and metal ions.
FIG. 3 is a diagram schematically showing an example of the structure of the MOF. In FIG. 3, 1 is a metal ion, 2 is an organic ligand, and 3 is a MOF formed by combining them. The MOF 3 has a hexahedral shape having a hollow portion 4 with a vertex having the metal ion 1 as a component and a side having the organic ligand 2 as a component as a framework. The gas to be measured adheres to or adsorbs to the hollow portion 4, but since it has such a hollow structure, the MOF 3 has a large specific surface area, and the reaction surface during sensing increases.

  Since the length of the side of the organic ligand 3 constituting the side is changed by changing the length of the chain, the size of the hollow portion of the MOF 3 can be adjusted. Further, by selecting the type of the organic ligand 3, it becomes possible to impart selectivity. As the organic ligand, it is preferable to use compounds represented by chemical formulas of Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, Chemical Formula 4, and Chemical Formula 5, trimesic acid, and the like.

As the metal ion, it is preferable to use at least one metal ion selected from Cu ²⁺ , Zn ^{2+ and the} like. When selecting Zn ²⁺ as the metal ion, an inorganic aggregate such as Zn ₄ O can be used as a raw material. In the case of selecting Cu ²⁺ as the metal ion, copper nitrate trihydrate (CuNO ₃ .3H ₂ O) or the like can be used as a raw material.

Although the hexahedral MOF using Zn ²⁺ has been described as an example of the MOF, the invention is not limited to this, and it goes without saying that other polyhedral shapes such as a tetrahedron and an octahedron may be formed.

Since MOF has a precise structure, it has high stability and can be used even in a high temperature environment. The present inventors have examined the temperature dependence of MOF, and as a result, the adsorption rate at which the gas to be measured is adsorbed on the MOF and the desorption rate at which the adsorbed gas is desorbed from the MOF are the rates for the temperature change. We found that the change was not constant.
Cu ₃ (BTC) ₂ H ₂ O composed of copper ions and trimesic acid (1,3,5-benzentricarboxylate: hereinafter sometimes abbreviated as BTC) and having an octahedral shape is measured at 10 ° C. or higher. It is preferable to adsorb the target gas and desorb the target gas at a temperature of 40 ° C. or higher. The reason for this will be described in detail in Examples below, but Cu ₃ (BTC) ₂ H ₂ O is constant in the adsorption rate in the temperature range of 20 ° C. to 60 ° C., whereas the gas desorption rate. Is about 4 times higher at 40 ° C. or higher than when the temperature is lower than 30 ° C., so that a good response can be obtained as a sensor.

  In order to use MOF as the sensitive film 42 of the cantilever type vibrator, a self-assembled monomolecular film (hereinafter abbreviated as SAM film) having a terminal carboxylic acid is formed on a gold film, and the carboxylic acid of the SAM film is formed. It is preferable to form a thin film made of MOF on the surface.

A method for forming a film of Cu ₃ (BTC) ₂ H ₂ O as an example of MOF will be described. By preparing a dimethyl sulfoxide solution in which copper nitrate trihydrate (CuNO ₃ .3H ₂ O) and trimesic acid are dissolved and contacting with a SAM film having a terminal carboxyl group, the terminal carboxyl group is used as a starting point. A crystal of Cu ₃ (BTC) ₂ H ₂ O is precipitated. At this time, since crystal growth is performed under DMSO vapor, it is preferable to set the temperature within a range of 100 ° C to 150 ° C.

  The vibrator 41 on which the sensitive film 42 as described above is formed is provided in a chamber having a predetermined volume (for example, 0.1 to 0.5 cc). In the chamber, a plurality of vibrators 41 each having the sensitive film 42 as described above are installed. Different sensitive films 42 are formed on the plurality of vibrators 41.

Now, a driving structure of the vibrator 41 of the detection sensor 40 in the substance detection system 10 as described above will be described.
As shown in FIG. 4, the vibrator 41 is formed on a vibrator chip (substrate) 100 made of a silicon-based material. The vibrator 41 is formed by patterning the vibrator chip 100 by a photolithography method or the like, and removing unnecessary portions by etching or the like, and has a fixed end with a base end portion fixed to the substrate body 101. The end is a free end that overhangs. A vibration detection unit 44 is disposed at the base end of the vibrator 41, and the vibration detection unit 44 detects the vibration displacement of the vibrator 41 as an electrical signal.

  Such a transducer chip 100 is supported on a base substrate 110 serving as a base of the detection sensor 40 via a chip package (element package) 120 and a PZT plate (piezoelectric element) 130.

  An opening 111 is formed in the base substrate 110. The chip package 120 is provided on one surface side of the base substrate 110 with an outer peripheral portion fixed by a fixing member 112 so as to close the opening 111. The chip package 120 can mount an IC chip and has a wiring pattern that is electrically connected to each electrode of the IC chip. As such a chip package 120, DIP (Dual Inline Package) or QFP (Quad Flat Package) can be used.

The PZT plate 130 is a plate-like body made of a PZT material, and is bonded to one surface side of the chip package 120 via an adhesive 200.
The PZT plate 130 is arranged with the positive electrode on the chip package 120 side and the negative electrode on the vibrator chip 100 side. Each electrode of the PZT plate 130 is electrically connected to the wiring portion of the chip package 120 by a wiring 140 by wire bonding. The PZT plate 130 generates vibration at a predetermined frequency by a voltage applied from the chip package 120 in accordance with a control signal from an external drive circuit.

In the resonator chip 100, the substrate body 101 is bonded to the other surface side of the PZT plate 130 with an adhesive 210.
Further, in order to efficiently transmit the vibration generated in the PZT plate 130 to the vibrator chip 100, the PZT board 130 and the vibrator chip 100 have a high hardness (rigidity) after being hardened to the adhesive 210, for example, an epoxy system, for example. It is preferable to use an adhesive or the like to firmly integrate. The adhesive 210 can suppress the vibration transmitted from the PZT plate 130 to the transducer chip 100 from being attenuated.

  The detection sensor 40 is provided with a cooling mechanism (cooling unit) 150. The cooling mechanism 150 cools the transducer chip 100 on which the transducer 41 is formed. When the vibrator 41 having the sensitive film 42 is cooled, the sensor sensitivity by gas adsorption is improved. This is because the sensitivity is improved when the sensitive film 42 is cooled. Therefore, it is preferable to control the temperature of the vibrator 41 and the sensitive film 42 to a constant temperature within the range of −10 to 25 ° C., more desirably −5 to 15 ° C., by the cooling mechanism 150.

The cooling mechanism 150 may have any configuration as long as it can satisfy such a purpose. For example, the following configuration can be adopted.
That is, the cooling mechanism 150 is provided on the other surface side of the base substrate 110, and the cooling element 152 provided on the other surface side of the chip package 120 exposed to the opening 111 via the heat sink 151, and the heat dissipation. It consists of fins 153 and heat dissipation fans 154.
The heat sink 151 is made of, for example, Cu, and takes heat from the chip package 120 by being cooled by the cooling element 152.
Any element may be used as the cooling element 152, but a Peltier element is preferably used from the viewpoint of responsiveness. The operation of the cooling element 152 is controlled by the control unit 54.
The heat radiation fins 153 and the heat radiation fan 154 radiate the heat of the cooling element 152. Here, the heat radiation fin 153 is preferably joined to the surface of the cooling element 152 with a material having high thermal conductivity and low conductivity (for example, a silicone paste containing a metal oxide).

  In such a cooling mechanism 150, the control unit 54 operates the cooling element 152 based on the temperature of the detection sensor 40 detected by the sensor 155 at an appropriate position (in this embodiment, the heat sink 151). -The vibrator 41 and the sensitive film 42 are cooled by cooling the vibrator chip 100 via the package 120 and the PZT plate 130. Thereby, the detection sensitivity in the vibrator 41 and the sensitive film 42 can be improved, and the substance detection sensitivity in the substance detection system 10 can be improved.

The measurement processing unit 50 includes a drive circuit 51 for driving the vibrator 41 as described above and a detection circuit 52 for detecting an electrical signal from the vibration detection unit 44.
Under the control of the control unit 54, a detection target such as a molecule having a mass in the sensitive film 42 is obtained in a state where the vibrator 41 of the detection sensor 40 is driven by an electric signal from the drive circuit 51 and vibrated at a predetermined frequency. When attached, the vibration frequency of the vibrator 41 changes. The detection circuit 52 of the measurement processing unit 50 receives the electric signal output from the vibration detection unit 44 and detects the change in the electric signal to detect whether or not a specific type of molecule is adsorbed on the sensitive film 42 or its amount. Measure.
The measurement result in the measurement processing unit 50 can be output on the display unit 53 by ON / OFF of lamps, buzzers, etc., display of measured values, measurement levels, display of detection substance name / concentration (amount), and the like. preferable.

In this way, the substance contained in the gas can be identified and its concentration can be measured. At this time, the discriminating ability is enhanced by making the material of the sensitive film 42 different. Further, by detecting the desorption timing when the substance is desorbed from the adsorbent by the heating of the sheath heater 34 with the detection sensor 40 and the measurement processing unit 50, the ability to identify the type of the substance is enhanced.
In addition, by compressing and feeding the gas in the pump 20, it becomes possible to perform highly sensitive detection even with a small amount of gas, and the substance detection system 10 should be equipped with highly sensitive detection performance that is unprecedented in spite of its small size. Can do. Such a substance detection system 10 can be easily manufactured except for the vibrator 41 manufactured by a microfabrication technique such as a MEMS (Micro Electro Mechanical Systems) technique, thereby reducing the cost. Become.

  After measuring the type and amount (concentration) of the component molecules adsorbed on the sensitive film 42 as described above, the adsorbed component molecules are removed from the sensitive film 42 by heating the sensitive film 42 with the heater 90. Detach.

In the substance detection system 10 shown in FIG. 1, the control unit 54 operates the pump 20, heats the energization of the sheath heater 34, drives and detects the vibrator 41, operates the heater 90, and performs measurement processing in the measurement processing unit 50. To control.
FIG. 5 shows the flow.
First, at the start of the operation of the substance detection system 10, the transducer chip 100 including the transducer 41 is cooled to a low temperature where the sensitivity of the detection sensor 40 is increased, and the temperature is kept low (step S101). This temperature is determined by the type of the sensitive film 42 mounted on the vibrator 41. In the case of PAB or PBD, about 0 to 10 ° C. is preferable. Although the sensitivity increases at lower temperatures, there arises a problem that the difference in selectivity is eliminated depending on the type of the sensitive membrane 42.

Thereafter, the gas is sucked and concentrated by the pump 20 for a predetermined time, and the molecules contained in the gas are adsorbed by the adsorption unit 30 (step S102). After the elapse of the predetermined time, the suction of gas from the pump 20 is stopped while the pump 20 is operated.
Air or an inert gas prepared separately is supplied from the pump 20 at a preset flow rate, and the sheath heater 34 is energized to heat the adsorption unit 30 and desorb component molecules adsorbed by the adsorption unit 30 (step S103).

The desorbed component molecules are transferred to the detection sensor 40, and measurement by the detection sensor 40 is started (step S104).
The component molecules are adsorbed on the sensitive film 42 of the vibrator 41. As a result, the vibration frequency of the vibrator 41 changes. At this time, when detection starts, the sensor signal gradually increases. The control unit 54 constantly measures the change amount of the sensor signal (step S105), and when the change amount falls below a predetermined threshold, it is determined that the detection has reached a saturation state (step S106).

When determining that the detection has reached the saturation state, the control unit 54 applies a preset heater voltage to the heater 90 incorporated in the vibrator 41 (step S107). The application time at this time is also set to a predetermined set value.
At this time, the surface of the cantilever-type vibrator 41 reaches the set temperature in a very short time (0.1 to several seconds). Then, the component molecules adsorbed on the sensitive film 42 are desorbed (step S108). Since the temperature of the vibrator 41 also rises at the time of desorption, the control unit 54 ignores the change in the detection frequency at that time.

  When the voltage application to the heater 90 is stopped after a predetermined application time has passed (step S109), the temperature returns to a constant temperature in 0.1 to 3 seconds. (This is called stabilization hold; step S110).

Thereby, a series of detection processing is completed.
In the substance detection system 10, real-time substance detection can also be performed by repeating the above-described series of detection processing cycles at regular time intervals. In that case, the detection sensor 40 shifts to the next cycle after the stabilization suspension in step S110 ends, and starts measurement in the detection sensor 40 in step S104. Therefore, it is preferable to desorb the component molecules adsorbed by the adsorption unit 30 in Step S103 after the stabilization suspension in Step S110 is completed.

Here, it is preferable to perform the detection as described above a plurality of times by changing the temperature at the time of detection to two or more conditions. Under each temperature condition, the frequency change of the vibrator 41 can be detected, and at least one of the gas component and the concentration can be estimated based on the difference in the frequency change in the temperature condition of these two or more conditions.
This estimation method is shown below. If the sensitivity S1a at the temperature T1 of the sensor 1 coated with the sensitive film is S1a (T1), the frequency change amount of the sensor 1 is S1a (T1) Ca as the product of the sample concentration Ca. If the sensitivity S2a at the temperature T1 of the sensor 2 coated with another sensitive film is S2a (T1), the frequency change amount of the sensor 2 is S21a (T1) Ca as the product of the sample concentration Ca.
Next, when the sensor is driven at the second temperature T2, if the sensitivity S1a at the temperature T2 of the sensor 1 coated with the sensitive film is S1a (T2), the frequency change amount of the sensor 1 is the product of the sample concentration Ca. Becomes S1a (T2) Ca. If the sensitivity S2a at the temperature T2 of the sensor 2 coated with another sensitive film is S2a (T2), the frequency change amount of the sensor 2 is S21a (T2) Ca as the product of the sample concentration Ca.
Solving these four simultaneous equations makes it possible to estimate the gas component and concentration.

In the substance detection system 10 described above, when the component molecules are adsorbed to the sensitive film 42, the sensitive film 42 is cooled, and when the component molecules are desorbed from the sensitive film 42, the sensitive film 42 is heated. Adsorption and desorption of component molecules can be performed efficiently in a short time. Thereby, the detection efficiency for detecting the substance can be increased.
When the component molecules are adsorbed on the sensitive film 42 of the vibrator 41, the vibration frequency of the vibrator 41 changes, and the controller 54 constantly measures the change in the sensor signal. Then, when the amount of change falls below a predetermined threshold, it is determined that the detection has reached a saturation state, and a preset heater voltage is applied to the heater 90 incorporated in the vibrator 41 and is adsorbed to the sensitive film 42. The component molecules were desorbed. Thereby, not only the kind of the sensitive film | membrane 42 but detection can be performed by optimal adsorption temperature and time, without setting adsorption temperature and adsorption time beforehand.

The substance detection system 10 described above may further include a storage unit 54M (see FIG. 2) such as a memory for storing the cooling characteristics such as the cooling temperature and the heating temperature and the heating characteristics for each type of the sensitive film 42. it can.
In that case, the control unit 54 corresponds to the type of the sensitive film 42 provided in the vibrator 41, and based on the cooling characteristics and heating characteristics of the sensitive film 42 stored in the storage unit, the sensitive film by the cooling mechanism 150. The cooling of 42 and the heating of the sensitive film 42 by the heater 90 are controlled.
Thus, by storing the cooling characteristics such as the cooling temperature and the heating temperature and the heating characteristics for each type of the sensitive film 42, the adsorption and desorption of the component molecules can be efficiently performed in a short time. Thereby, the detection efficiency for detecting the substance can be increased.

[Example 1]
Here, since the configuration shown above was verified, the results are shown below.
As the vibrator 41 of the detection sensor 40, a cantilever type was prepared.
The cantilever-type vibrator 41 was formed from an SOI (Silicon on Insulator) substrate using a MEMS process. First, an oxide layer is formed on a 5 μm-thick active layer of an N-type SOI substrate, a pattern is formed by photolithography, and boron P-type diffusion is performed to form a Si piezoresistive layer as a detection circuit. After that, a vibrator 41 having a length of 500 μm and a width of 100 μm was formed by RIE (Reactive Ion Etching) etching method. Thereafter, in order to reduce attenuation due to air damping, the silicon of the support layer was removed from the back surface by a Deep-RIE etching method.
One or two Si piezoresistors (about 2K ohms) as a detection circuit are arranged at the base of the vibrator 41, and a Wheatstone bridge is formed together with other reference piezoresistors. Further, a gold film of about 100 nm was formed on the surface of the vibrator 41 through a silicon oxide film and an adhesive layer Cr.

Then, MOF was formed as a sensitive film material. Here, a self-assembled monolayer (SAM) having a terminal carboxylic acid was formed on the gold electrode surface on the QCM, and MOF growth from the carboxylic acid surface was attempted. Various MOFs are adjusted by the combination of organic ligands and metal ion species. Among them, Cu ₃ (BTC) ₂ (H ₂ O) ₃ composed of copper ions and trimesic acid is used for gas sensors. The crystal was grown on a gold electrode that was selected as a recognition material and modified with a SAM film. Furthermore, the adsorption / desorption process by the exposure of VOCs was examined using these MOF thin films.

"Evaluation of sensitive membrane"
First, before film formation on a cantilever type vibrator, evaluation was performed by forming a film on an upper part of a QCM capable of evaluating film thickness and gas adsorption by a simple method. The production method is shown below.
First, 16-mercaptohexadecanoic acid was added to a mixed solution of ethanol and acetic acid to prepare a reaction solution. The washed QCM was immersed overnight and allowed to stand. After immersion, the QCM was taken out of the solution, washed with methanol and dried. This formed a SAM having a terminal carboxylic acid on the QCM.
Next, the substrate on which the SAM was formed was placed in a dimethylsulfoxide (DMSO) solution of copper nitrate trihydrate (CuNO ₃ 3H ₂ O) and trimesic acid (1,3,5-benzentricarboxylate: BTC) at a constant temperature and constant temperature. By making contact for a time, a crystalline thin film of Cu ₃ (BTC) ₂ (H ₂ O) ₃ was formed starting from SAM. Crystal growth was performed under DMSO vapor, and a blue-green MOF crystal was successfully grown only on the gold electrode portion.
At this time, using a DMSO solution containing 5.0 mM CuNO ₂ .3H ₂ O and 2.8 mM BTC, the weight of MOF grown at 123 ° C. for 6 hours was estimated from the change in frequency of QCM. 63 μg of Cu ₃ (BTC) ₂ (H ₂ O) ₃ crystalline thin film was formed on the substrate. The formed MOF was evaluated by SEM observation, FT-IR, and X-ray diffraction measurement.

(MOF observation with a scanning electron microscope)
The formed MOF was observed using a scanning electron microscope (SEM). The results are shown in FIG.
As shown in FIG. 6, the obtained thin film had a quadrangular pyramid shape, and a thin film was formed by a large number of crystals concentrated. The average crystal size was confirmed to be about 4 μm.

(XRD measurement)
X-ray diffraction measurement (XRD) was performed on the MOF thin film on the produced QCM and powdered Cu ₃ (BTC) ₂ (H ₂ 0). The results are shown in FIG.
From FIG. 7, in the powder sample (Powder Sample in the figure), a plurality of reflection peaks attributed to the three-dimensional network of Cu ₃ (BTC) ₂ (H ₂ 0) were obtained. In contrast, in the XRD of a thin film obtained by growing Cu ₃ (BTC) ₂ (H ₂ 0) from a SAM film having a carboxylic acid surface (SAM-COOH in the figure), it is derived from the (200) and (400) planes. A strong reflection peak was obtained.

(VOCs adsorption measurement)
Adsorption measurement of VOCs was performed using an apparatus capable of measuring the amount of adsorption of VOCs by flowing a gas having a constant flow rate and a constant concentration into the chamber. For the measurement, a QCM sensor, which is a technique for measuring a minute change in mass, was used. In the QCM sensor, a mass change due to adsorption / desorption of VOCs is detected as a frequency change, and a resonance frequency change Δf [Hz] is generated by the mass change Δm [ng] on the electrode surface. Is detected.
Δf = −2f0 ² Δm / [A (μq · ρq)] ^1/2 . . . . . . . . . . (1)
Here, f0 is the fundamental frequency, A is the electrode area, μq is the shear stress (rigidity) of the crystal, and ρq is the density of the crystal. Since the used QCM has a fundamental frequency of 9 MHz and an electrode area of 0.196 cm ² , the mass change Δm and Δf on the electrode can be expressed by the following relationship.
Δm = −1.07 [Hz / ng] × Δf. . . . . . . . . . . . . . (2)

  As shown in the above equation, the QCM can measure the mass of VOCs molecules adsorbed on the order of nanograms from the change in frequency. The frequency change of this QCM was measured, and the VOCs adsorption measurement was performed in a temperature-controlled chamber. In this measurement, VOCs adsorption measurement was performed using toluene with an aromatic ring similar to the organic ligand used for MOF formation, and changes in adsorption / desorption amount due to concentration change and changes in adsorption amount with other substances were considered. did. Further, as a pretreatment for measuring VOCs adsorption, it was heated on a hot plate at 120 ° C. for 20 minutes and used after sufficiently flowing 200 sccm of nitrogen gas. Based on the above calculation, the mass of MOF formed from the frequency change and the adsorption amount of VOCs to the MOF thin film were calculated.

  The adsorption of toluene was measured using the prepared 500 nm MOF thin film. The amount of adsorption was measured by changing the measured concentration in the range of 100 to 1000 ppm. Further, measurement was performed under the same conditions using Poly (butadiene) (PBD) as a substance for comparing the amount of adsorption with the prepared MOF thin film. PBD is one of organic polymers that are also used in mass detection sensors, and several reports have been made.

As a result of the measurement, the concentration dependence of the frequency change as shown in FIG. 8 was observed. In the PBD film, the adsorption amount is proportional to the concentration in the range of 100 ppm to 1000 ppm, but it is estimated that the MOF thin film is close to a saturated state.
Under the condition of 1000 ppm, the VCMs using MOF adsorbed 30 times more VOCs than the QCM sensor using PBD. Furthermore, at 100 ppm, 300 times or more adsorption of toluene molecules was observed. It was suggested that the material is very sensitive in the low concentration range.

  FIGS. 9A and 9B show the difference in adsorption characteristics when the components of toluene, xylene, octane, acetone, ethanol and VOC are changed by the same method. This MOF material was found to be highly sensitive to acetone and ethanol.

(Adsorption and desorption changes with temperature)
Next, the toluene adsorption / desorption response in a QCM sensor using MOF with the measurement temperature adjusted was evaluated. The results are as shown in FIG.
When the chamber temperature was changed from 20 ° C to 60 ° C, it was confirmed that the adsorption rate did not change under any temperature conditions, but the desorption rate increased as the chamber temperature increased. did. When measured at 60 ° C., it took about 15 minutes for all the toluene in the adsorbed film to desorb, whereas when measured at 40 ° C., it took about 1 hour. Further, at 20 ° C. and 30 ° C., toluene could not be completely eliminated even after 3 hours.
From the above, it was suggested that a temperature setting of 40 ° C. or higher is necessary in order to obtain a good responsiveness by using the MOF thin film produced this time for the sensor. Development of a highly sensitive molecular size recognition membrane can be realized by clarifying the correlation between molecules in gas adsorption / desorption and the pore space in the MOF.

"Evaluation of cantilever type vibrator"
FIG. 11 shows an example in which this MOF film is formed on a cantilever type vibrator. On the cantilever type vibrator, a gold thin film is formed in advance in a region where a sensitive film is to be formed, so that MOF is formed only on that portion. Film formation is performed by the same method as in the case of QCM.
FIG. 12 shows an enlarged view of the MOF on the cantilever type vibrator. As shown in the figure, the obtained material has observed pyramid-shaped crystal grains, and a thin film was formed by a large number of crystals concentrated. Moreover, it confirmed that average crystal size was about 2-10 micrometers similarly to QCM.

  Further, on the upper surface of the cantilever type vibrator 41, as another sensitive film 42, films made of 980 nm PAB, PBD, PSB and PS having excellent adsorption characteristics in toluene and xylene are respectively formed using a dispenser. Created by drying.

FIG. 13 shows the ability of PAB, PBD, PSB and PS to adsorb acetone, toluene, octane and ethanol as a function of temperature.
Here, the K-factor was used so that the adsorption ability can be used with either a QCM or a cantilever type vibrator. The K-factor can be expressed as the ratio of the unit volume concentration in the gas to the material when the material is exposed to a predetermined concentration of VOC in equilibrium. Here, the concentration of VOC is 1000 ppm. In any case, the K-factor increases with lower temperatures. Highly sensitive conditions for acetone and alcohol can be achieved by using PAB at 0 degrees. In this case, the K factor was PAB with respect to acetone, K = 1200 at 0 ° C., and 2000 with ethanol. Here, PS also has a large factor, but because the response of adsorption and desorption is poor, it is not suitable for this chemical sensor system having a concentration tube and an analysis function.

Here, a sensitive film such as MOF, PBD, PAB, PSB, etc. was applied on one or more cantilever type vibrators, incorporated in a sensor module, and operated at an optimum temperature for each sensitive film.
(In case of MOF)
As shown in FIG. 10, MOF has a large adsorption ability at room temperature, but there is a problem that the desorption response is extremely bad. However, the response characteristic becomes very fast by raising the temperature to 60 degrees. When the responsiveness is fast, the sensor correctly responds to the desorption response from the concentrator, and correct detection and analysis are possible.
(PBD, PAB, PSB)
As shown in FIG. 13, with these materials, the sensitivity can be increased to 2 to 3 times the room temperature while maintaining the response characteristics by cooling to around 0 to 10 ° C.

Here, looking at the characteristics of the MOF in FIG. 10, the adsorption capacity is large near room temperature and the response during adsorption is fast, but the desorption time is extremely slow. Only when the temperature was raised to about 60 ° C., the tendency for the desorption characteristics to improve was observed. Therefore, an optimum sensor drive can be obtained by setting the temperature low during adsorption and high temperature during desorption.
However, a temperature change of 10 degrees takes 10-20 seconds to heat and cool the package containing the sensor. Since the change in frequency is very sensitive to temperature, even a slight change in temperature can change the frequency.

Therefore, a cantilever type vibrator used as a mass sensor was manufactured from an SOI wafer having an active layer having a thickness of 5 μm. The active layer is an n-type having an impurity concentration of 1 × 10 ¹⁵ / cm ³ , and a cantilever-type vibrator structure having a width of 50 μm or 100 μm and a length of 200 to 500 μm is formed using Deep Reactive Ion Etching (DRIE).
In order to suppress air damping of the cantilever type vibrator, the substrate was removed from the back surface by DRIE. The BOX layer on the back surface of the cantilever type vibrator was finally removed by BHF etching.

On the front side of the cantilever type vibrator, a piezoresistive element for vibration detection was formed at the base, and a Cr (10 nm) / Au (100 nm) film for coating a detection film was formed on the other main body. The piezoresistor is manufactured by the impurity implantation technique of B, and has a p-type impurity concentration of 1 × 10 ¹⁵ / cm ³ and a depth of about 1 μm.
In order to make ohmic contact with the metal wiring, the contact portion is doped with high-concentration p-type impurities (1 × 10 ¹⁹ / cm ³ , depth of about 0.3 μm).
An Al—Si—Cu wiring is formed through a passivation oxide film having a thickness of 500 nm.
A P-type semiconductor used as a heater uses an n-type region of an SOI substrate and a p-type region made by the same process as a piezoresistor. In order to keep the resistance of the p-type region stable, it is necessary to increase the potential of the p-type diffusion region and the surrounding n-type region so that the pn junction is not in the forward direction (in this case, 5 V). That is, since it is necessary to make ohmic contact also in the n-type region, the n-type contact portion is doped with a high-concentration n-type impurity (1 × 10 ¹⁹ / cm ³ , depth of about 0.3 μm).
A piezoresistive element and a heater can be manufactured by the same impurity diffusion / wiring process, and there is almost no increase in process cost for adding a heater.

  The basic characteristic evaluation of the sensor was performed by mounting the sensor chip in a ceramic package and then placing it in a thermostatic chamber. A PZT plate is bonded to the back surface of the ceramic package, and vibration can be applied to the cantilever type vibrator.

  A semiconductor parameter analyzer (Agilent 4155C) was used for measuring the voltage-current characteristics. For the measurement of the vibration characteristics, a network analyzer (Agilent 4395A) was used, and the input / output characteristics were measured using the PZT plate drive as the input and the piezoresistive bridge voltage as the output. The piezoresistive bridge is supplied with a DC voltage from another power source.

FIG. 14 shows data for confirming the temperature rise by the heater. Since it is difficult to directly measure the temperature of the cantilever type vibrator, the temperature was estimated using the change in the resonance frequency.
The change in the resonance frequency when a voltage of 20 V was applied to the heater was 400 Hz in HT500. Since the temperature coefficient of the resonance frequency is measured to be 35 ppm / ° C. using a separate thermostatic chamber, a change of 400 Hz corresponds to 43 ° C. This temperature rise increases instantaneously because the heat capacity of the cantilever type vibrator is small. Thus, the heater created in the cantilever type vibrator can instantaneously change from 27 ° C. to 70 ° C. by a 43 ° C. increase.

FIG. 15 shows a temperature profile of the concentrating device mounted on the chemical sensor system.
The temperature is raised from room temperature to 520 ° C. at a rate of 1.3 ° C. per second.

FIG. 16 shows that the material applied to the cantilever-type vibrator is PAB, the film thickness is 890 nm, and the mixed gas 10 L of propanol 0.5 ppm, toluene 0.69 ppm and xylene 0.5 ppm when the vibration of the fourth order mode is about 800 kHz. The response characteristics of the change in the frequency when concentration is detected.
Peaks corresponding to propanol, toluene and xylene appear, indicating that analysis is possible. Here, it takes typically 25 seconds to reach the peak when the frequency change corresponding to each component is started. Therefore, after reaching this peak, the gas adsorbed on the sensitive film can be desorbed by instantaneously raising the temperature with a heater mounted on the cantilever type vibrator within a few seconds to 10 seconds. Even a sensitive membrane that cannot be sufficiently detached unless it is 60 degrees or more, such as MOF, can be used effectively.

  The configuration described in the above embodiment is merely an example, and the configuration described in the above embodiment may be selected or changed to another configuration as long as it does not depart from the gist of the present invention. Is possible.

DESCRIPTION OF SYMBOLS 10 Substance detection system 15 Sample container 20 Pump 30 Adsorption part 31 Cylindrical body 34 Sheath heater 40 Detection sensor 41 Vibrator 42 Sensitive film 44 Vibration detection part 50 Measurement processing part 51 Drive circuit 52 Detection circuit 53 Display part 54 Control part 90 Heater (heating) Part)
100 vibrator chip 120 chip package 130 PZT plate 150 cooling mechanism (cooling section)
151 Heat Sink 152 Cooling Element 153 Heat Dissipation Fin 154 Heat Dissipation Fan 155 Sensor 200 Adhesive 210 Adhesive

Claims (14)

A vibrator whose one end or both ends are fixed to a substrate and whose vibration characteristics are changed by attaching or adsorbing a substance having mass to the sensitive film;
A cooling section for cooling the sensitive film;
A strain sensor for detecting vibration of the vibrator;
A heating section for heating the sensitive film;
A piezoelectric element that vibrates the vibrator;
An element package for applying a voltage to the piezoelectric element;
A control unit for controlling the cooling unit and the heating unit;
With
The control unit cools the sensitive film by the cooling unit when adsorbing the component molecules contained in the gas to the sensitive film, and desorbs the component molecules adsorbed on the sensitive film from the sensitive film. Further, the detection sensor is controlled to heat the sensitive film by the heating unit. A detector for detecting a vibration frequency of the vibrator detected by the strain sensor;
The control unit heats the sensitive film by the heating unit when an amount of change in the vibration frequency per unit time of the vibrator detected by the detection unit becomes a predetermined threshold value or less. The detection sensor according to claim 1.   The detection sensor according to claim 2, wherein the detection unit detects at least one of a type and a concentration of the substance obtained based on a change timing of a vibration frequency of the vibrator. A storage unit for storing cooling characteristics and heating characteristics for each type of the sensitive film;
The controller controls the cooling of the sensitive film by the cooling unit and the sensitive by the heating unit based on the cooling characteristics and heating characteristics of the sensitive film stored in the storage unit corresponding to the type of the sensitive film. The detection sensor according to any one of claims 1 to 3, wherein heating of the film is controlled.   The sensitive film is any one of a porous metal complex (MOF), polybutadiene (PBD), polyacrylonitrile-butadiene (PAB), polyisoprene (PIP), and styrene-butadiene copolymer (PSB). The detection sensor according to any one of claims 1 to 4.   6. The sensitive film is made of a porous metal complex, and the controller heats the sensitive film to 60 degrees or more by the heater when desorbing the component molecules from the sensitive film. The detection sensor described in 1.   The sensitive film is made of a porous metal complex, and the control unit uses the cooling unit during detection. The detection sensor according to claim 5 or 6, wherein the temperature of the sensitive film is maintained at 10 to 25 ° C.   8. The strain sensor according to claim 1, wherein the strain sensor uses a piezoresistive effect of a resistance element, and the heater is formed using the same constant resistance as the strain sensor. The detection sensor described in 1. The piezoelectric element is bonded to one surface side of the element package, and the substrate having the vibrator is laminated and bonded to the piezoelectric element,
The detection sensor according to claim 1, wherein the cooling unit is provided on the other surface side of the element package.   The two or more vibrators are provided, and the two or more vibrators are provided with the sensitive film made of the materials different from each other. Detection sensor.   The detection unit detects a response characteristic of the sensor with respect to a change in frequency of the vibrator by setting a temperature at the time of detection to two or more conditions, and based on a difference in the frequency change at the temperature of the two or more conditions, The detection sensor according to claim 10, wherein at least one of the concentrations is estimated. A substance detection system that detects at least one of the type and concentration of a specific substance contained in a gas to be detected,
A pump for introducing the gas to be detected into the system, and for transporting the introduced gas in the system;
An adsorbing part for adsorbing the specific substance contained in the gas introduced into the system by the pump;
A first heater for desorbing the specific substance adsorbed by the adsorption unit from the adsorption unit;
One end or both ends of the beam are fixed to a substrate and include a sensitive film that adsorbs or adheres the specific substance desorbed from the adsorbing part, and vibrates due to the specific substance adsorbing or adhering to the sensitive film. A vibrator whose frequency changes;
A strain sensor for detecting vibration of the vibrator;
A cooling section for cooling the sensitive film;
A heater provided on the vibrator for heating the sensitive film;
A piezoelectric element that vibrates the vibrator;
An element package for applying a voltage to the piezoelectric element;
The heater and the cooling unit are controlled, and when the component molecules contained in the gas are adsorbed on the sensitive film, the sensitive film is cooled by the cooling unit, and the component molecules adsorbed on the sensitive film are removed from the sensitive film. A controller that heats the sensitive film by the heater when desorbing;
A change in the vibration frequency of the vibrator is detected from the vibration of the vibrator detected by the strain sensor, and the type of the specific substance obtained based on the change timing of the vibration frequency of the vibrator, and the vibration frequency A detection unit that detects at least one of the concentrations of the specific substance obtained based on the amount of change,
The control unit heats the sensitive film by the heater to change the component molecules when the change amount of the vibration frequency per unit time of the vibrator detected by the detection unit is equal to or less than a predetermined threshold. A substance detection system, wherein the substance is desorbed from the sensitive film.   The sensitive film is any one of a porous metal complex (MOF), polybutadiene (PBD), polyacrylonitrile-butadiene (PAB), polyisoprene (PIP), and styrene-butadiene copolymer (PSB). The substance detection system according to claim 12.   14. The substance detection system according to claim 12, wherein the vibrator is provided in a chamber into which the specific substance desorbed from the adsorption unit is sent by the pump.