CN114994144A - Flexible humidity sensor based on MoOx nano particle assembly material and assembly method and application thereof - Google Patents

Abstract

The invention discloses a flexible humidity sensor based on MoOx nano particle assembly material, an assembly method and application thereof, wherein the sensor comprises a flexible substrate and MoO _x The nano particle lattice, the metal microelectrode and the conductance measurement external circuit; wherein the metal microelectrode is arranged on the surface of the flexible substrate, and the MoO _x The nano particle lattice is deposited on the metal microelectrode, and the conductance measuring external circuit is electrically connected with the metal microelectrode. The nano particles are generated by cluster beam deposition equipment by adopting a gas phase aggregation deposition method. MoO-based obtained by the method of the invention _x The humidity sensing material and the flexible device of the nano particles can realize sensitive detection of humidity at room temperature, the response time is 2s, and the nano particle humidity sensing material and the flexible device have the characteristics of working at room temperature, high sensitivity and quick response time. The impedance of the nano particle lattice is in the megaohm magnitude, and the power consumption is extremely low; can be produced and packaged in large area.

Description

Flexible humidity sensor based on MoOx nanoparticle assembly material and its assembly method and application

technical field

The invention belongs to the field of sensors and detection instruments, and in particular relates to a flexible humidity sensor based on MoOx nanoparticle assembly material, an assembly method and application thereof.

Background technique

Humidity detection is closely related to human life and is one of the most important issues in agriculture, industrial production, environmental monitoring, aerospace and other application fields. With the development of society and the advancement of technology, people are paying more and more attention to flexible wearable electronic devices. Electronic smart textiles have huge development potential and broad market prospects. Smart textiles are widely used in human physiological signal monitoring, pressure, temperature and humidity detection, energy storage, gas sensors, and biosensors. It is particularly important to develop moisture sensing materials and devices suitable for flexible devices. Finding flexible sensing materials that enable high-performance humidity sensing is the key.

The invention proposes to couple the flexible substrate and the _MoOx nanoparticle assembly material to realize the high-performance humidity sensing technology. In this material, MoO _x nanoparticles play a humidity-sensitive role. The flexible substrate and planar thin-film electrode structure endow the device with flexibility. The device has the advantages of high sensitivity and fast response. The response time is less than 2s, and the humidity of the device is low. The response value is above 800, the power consumption of the device can be controlled in the sub-milliwatt level, and the flexible bending action can be controlled in the sub-milliwatt level without interference to the measurement, and the flexible bending action has no interference with the measurement.

SUMMARY OF THE INVENTION

Aiming at the problems of long response time and recovery time, poor response performance and inability to realize flexible sensing of traditional humidity sensing materials at present, the purpose of the present invention is to provide a flexible humidity sensor based on MoOx nanoparticle assembly material and its assembly method and application. The present invention Taking advantage of the ultra-high specific surface area of nanoparticles, it is proposed to prepare _MoOx nanoparticle assembly materials on the surface of flexible substrates by cluster beam deposition technology to realize flexible humidity sensing.

The technical scheme adopted in the present invention is:

A flexible humidity sensor based on MoO _x nanoparticle assembly material, the sensor includes a flexible substrate, a MoO _x nanoparticle lattice, a metal micro-electrode and an external conductivity measurement circuit; wherein, the metal micro-electrode is arranged on the surface of the flexible substrate, and the MoO _x The nanoparticle lattice is deposited on the metal micro-electrode, and the conductance measurement external circuit is electrically connected with the metal micro-electrode.

Further, the flexible substrate is a flexible material, and its material includes mica, polyimide, silicone rubber, fluorine rubber, polydimethylsiloxane or polyethylene terephthalate.

Further, the metal microelectrodes are interdigitated electrodes, made of gold or silver, the thickness of the electrodes is 100-300 nm, and the width between the two electrodes is 4-300 µm.

Further, the acquisition frequency of the conductance measurement external circuit is 1-2000 Hz, and is connected with the metal microelectrode through an enameled wire with a diameter of 10-100 µm.

The assembly method of the flexible humidity sensor based on MoOx nanoparticle assembly material of the present invention comprises the following steps:

1) Select a flexible substrate with a smooth and clean surface and no obvious scratches;

2) Print metal micro-electrodes on the surface of flexible substrates, and use masks to cover printing, electroplating or evaporation processes;

3) Deposition of MoOx nanoparticle lattices on metal microelectrodes is produced by using Mo as the target material and using a magnetron plasma gas cluster source to form nanoparticle beams deposited on metal microelectrodes by differential vacuuming. Aged in air to form MoOx nanoparticle lattice;

4) After the MoOx nanoparticle lattice deposition is completed, the enameled wire is used to connect the metal microelectrode and the external circuit for conductance measurement;

5) The flexible substrate is placed in different humidity environments, and the current changes of the sample nanoparticle lattices under different humidity environments are measured, and the humidity response curve (that is, the relationship between current responsivity and ambient humidity) is drawn.

Further, the metal microelectrodes are interdigitated electrodes, and the specific process of depositing MoOx nanoparticle lattices on the metal microelectrodes is: placing the high-purity Mo target on the sputtering gun of the cluster beam deposition equipment, and placing the MoOx nanoparticle lattice on the metal microelectrode. The interdigital electrode of the flexible substrate is placed in the deposition chamber of the cluster beam deposition system, and the whole device is evacuated. And pass the voltage to partially vaporize the Mo target into gaseous molecules or atoms, and then the buffer gas collides with it to form nanoparticles, and the nanoparticle beam is formed by the method of differential pumping, and then the beam is directed to the cluster beam. The deposition chamber of the flow deposition equipment is deposited on the surface of the interdigital electrode, and aged in the air at room temperature for more than 24 hours, so that the Mo nanoparticles are oxidized to molybdenum oxide _MoOx in the air, thereby obtaining the MoOx nanoparticle lattice.

Further, the air pressure in the sputtering chamber was maintained at 50-150Pa, the sputtering power of the Mo target was set to 12-18W, the sputtering current was 0.03-0.0375A, the sputtering voltage was 400-480 V, and the sputtering time was is 200~250 s.

The flexible humidity sensor based on the MoOx nanoparticle assembly material provided by the present invention can be well applied in detecting environmental humidity.

Compared with the prior art, the beneficial effect obtained by the present invention is that the nanoparticles in the present invention are produced by the cluster beam deposition equipment adopting the vapor-phase aggregation deposition method. The humidity sensing material and flexible device based on MoO _x nanoparticles obtained by the method of the present invention can realize sensitive detection of humidity at room temperature, the response time is as low as 2s, and has the characteristics of working at room temperature, high sensitivity and fast response time . The impedance of the nanoparticle lattice is in the order of megohms, and the power consumption is extremely small; it can be produced and packaged in a large area.

Description of drawings

Fig. 1 is the structural schematic diagram of the flexible humidity sensor of _MoOx nanoparticle assembly material of the present invention;

In Figure 1: 1 is a flexible substrate, 2 is a MoO _x nanoparticle lattice, 3 is a metal microelectrode, and 4 is an external circuit for conductance measurement;

Fig. 2 is the humidity response curve of the sensor of the present invention;

Fig. 3 is the humidity hysteresis curve of the sensor of the present invention;

Fig. 4 is the response curve of the sensor of the present invention under different breathing states of the human body;

FIG. 5 is the humidity response curve of the sensor according to the present invention in a bent state and a flat state.

Detailed ways

The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

Example 1:

The schematic structural diagram of the flexible humidity sensor based on the _MoOx nanoparticle assembly material of the present invention is shown in FIG. 1, including a flexible substrate 1, a _MoOx nanoparticle lattice 2, a metal microelectrode 3 and an external conductance measurement circuit 4; wherein, The metal micro-electrode 3 is arranged on the surface of the flexible substrate 1 , the MoO _x nanoparticle lattice 2 is deposited on the metal micro-electrode 3 , and the conductance measurement external circuit 4 is electrically connected to the metal micro-electrode 3 .

The preparation of the flexible humidity sensor based on the MoOx nanoparticle assembly material of the present invention includes the following steps:

1) Choose a flexible substrate insulating film that is clean and has a smooth surface without scratches. In this example, polyamide is used, and the thickness of the film is selected to be 0.1 mm;

2) The interdigitated electrodes are printed on the surface of the flexible substrate, and the interdigitated silver electrodes are prepared by mask evaporation in a vacuum. The thickness of the electrode metal layer is about 100 nm, and the width of the gap between the positive and negative electrodes of the electrode is 100 µm. ;

3) Place the high-purity Mo target on the sputtering gun of the cluster beam deposition equipment, place the interdigital electrode with the flexible substrate in the deposition chamber of the cluster beam deposition equipment, and take a pumping method for the whole device. Vacuum to bring the deposition chamber vacuum to 2×10 ^-4 Pa.

4) Pour 60 sccm of sputtering gas into the sputtering gun equipped with the Mo target, and 80 sccm of buffer gas into the sputtering chamber (both the sputtering gas and the buffer gas use high-purity argon gas of more than 99.5%) ), the air pressure in the sputtering chamber is 100 Pa at this time, and then the power of 15 W is applied to the sputtering gun equipped with the Mo target. At this time, the sputtering current is 0.036 A and the sputtering voltage is 416 V. The sputtering time was 220 s. Turn off sputter gas and power. After being taken out, it is aged in air for more than 24 hours at room temperature, thereby obtaining the MoOx nanoparticle lattice deposited on the interdigitated electrode.

5) After the MoOx nanoparticle lattice deposition is completed, an enameled wire (100 μm in diameter) is used to connect the positive and negative electrodes of the interdigital electrode to the external circuit for conductance measurement to obtain a flexible humidity sensor.

A performance test was performed on the flexible humidity sensor prepared in Example 1 (the voltage of the external circuit for conductance measurement was 1V, and the collection frequency was 1000 Hz):

The prepared sensors were placed in bottles with different saturated salt solutions, namely saturated aqueous K2CO3 _{( 43} % RH), saturated aqueous NaBr (57% RH), saturated aqueous NaCl (75% RH), and saturated aqueous solutions of NaCl (75% RH). Aqueous KCl (85% RH), saturated aqueous _KNO3 (95% RH). That is, the interdigital electrode with flexible substrate is placed above the closed bottle, and the bottom of the bottle is filled with saturated salt solution. Taking saturated K ₂ CO ₃ aqueous solution (43%RH) as an example, it refers to the environment of the space above the bottle. The relative humidity is 43% RH at room temperature. The changes of the current under different humidity recorded by the external circuit are shown in Figure 2 (43%, 57%, 75%, 85% and 95% in Figure 2 represent relative humidity, respectively).

The prepared sensor is tested for hysteresis: the specific method is to test the response current (that is, the current change under the rising humidity) under the relative humidity of 0%, 43%, 57%, 75%, 85% and 95% successively, and then successively. The response current (that is, the current change under the humidity drop) was tested at relative humidity of 95%, 85%, 75%, 57%, 43% and 0%. The test results are shown in Figure 3. It can be seen from FIG. 3 that the sensor of the present invention has good hysteresis.

The prepared sensor was tested for humidity responsiveness: the flexible substrate of the sensor was attached to the inside of the mask, and the sensors were tested for normal breathing (15-20 times/min), first-level rapid breathing (30-40 times/min), and second-level The response current curve was tested under fast breathing (50-60 times/min), and the results are shown in Figure 4. It can be seen from FIG. 4 that the sensor of the present invention has good sensitivity and fast response speed.

The prepared sensor was tested for bending resistance: the flexible substrate of the first sensor was in a flat state, the flexible substrate of the second sensor was bent to about 45°, and they were placed in a saturated KCl aqueous solution ( 85% RH) bottle, that is, the interdigital electrode with flexible substrate is placed inside the upper part of the closed bottle, and the lower part of the bottle is filled with saturated KCl aqueous solution (85% RH). The changes of the current in different states are recorded by the external circuit, as shown in FIG. 5 . The sensor of the present invention has very good response performance against bending and humidity.

The content described in this specification is only an enumeration of the realization forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms stated in the embodiments.

Claims (8)

1. A flexible humidity sensor based on _MoOx nanoparticle assembly material, characterized in that the sensor comprises a flexible substrate (1), a _MoOx nanoparticle lattice (2), a metal microelectrode (3) and an external circuit for conductance measurement ( 4); wherein, the metal microelectrode (3) is arranged on the surface of the flexible substrate (1), the _MoOx nanoparticle lattice (2) is deposited on the metal microelectrode (3), and the conductance measurement external circuit (4) is connected to the metal microelectrode. Electrodes (3) are electrically connected. 2. The flexible humidity sensor based on _MoOx nanoparticle assembly material according to claim 1, characterized in that the flexible substrate (1) is a flexible material, and its material comprises mica, polyimide, silicone rubber, fluorine rubber, Dimethicone or polyethylene terephthalate. 3. The flexible humidity sensor based on _MoOx nanoparticle assembly material according to claim 1, characterized in that the metal microelectrode (3) is an interdigital electrode, the material is gold or silver, and the electrode thickness is 100-300 nm , the width between the poles is 4-300µm. 4. The flexible humidity sensor based on _MoOx nanoparticle assembly material as claimed in claim 1, characterized in that the collection frequency of the conductance measurement external circuit (4) is 1-2000 Hz, and is connected with the metal microelectrode (3) through the diameter of For 10-100µm enameled wire connections. 5. the assembly method of the flexible humidity sensor based on MoOx nanoparticle assembly material described in any one of claim 1-4, is characterized in that comprising the following steps: 1) Select a flexible substrate with a smooth and clean surface and no obvious scratches (1) 2) Printing metal microelectrodes (3) on the surface of the flexible substrate (1), and using a mask to cover the process of printing, electroplating or evaporation; 3) Deposition of MoOx nanoparticle lattice (2) on the metal microelectrode (3), which is produced by using Mo as the target material and using a magnetron plasma gas cluster source to form a nanoparticle beam deposition by differential vacuuming. on the metal microelectrode (3), and then ageing in the air to form a MoOx nanoparticle lattice (2); 4) After the MoOx nanoparticle lattice (2) is deposited, enameled wires are used to connect the metal micro-electrode (3) and the conductance measurement external circuit (4); 5) The flexible substrate (1) is placed in different humidity environments, and the current changes of the sample nanoparticle lattices under different humidity environments are measured, and the humidity response curve is drawn. 6. The method for assembling a flexible humidity sensor based on MoOx nanoparticle assembly material as claimed in claim 5, wherein in step 3), the specific process of depositing MoOx nanoparticle lattice on the metal microelectrode is: The Mo target was placed on the sputtering gun of the cluster beam deposition equipment, the interdigital electrodes with flexible substrates were placed in the deposition chamber of the cluster beam deposition equipment, and the whole device was evacuated until the vacuum degree reached After standardization, pass high-purity argon gas into the sputtering gun as the sputtering gas, pass the high-purity argon gas into the sputtering chamber as the buffer gas, and pass in the voltage to partially vaporize the Mo target into gaseous molecules or atoms. , and then the buffer gas collides with it to form nanoparticles, and the nanoparticle beam is formed by the differential pumping method, and then the beam is directed to the deposition chamber of the cluster beam deposition equipment, and deposited on the surface of the metal microelectrode at room temperature. Aged in the air for more than 24 hours, the Mo nanoparticles are oxidized to molybdenum oxide _MoOx in the air, thereby obtaining the MoOx nanoparticle lattices deposited on the metal microelectrode. 7. The assembling method of the flexible humidity sensor based on MoOx nanoparticle assembly material as claimed in claim 6, wherein the air pressure in the sputtering chamber is maintained at 50～150Pa, and the sputtering power of the Mo target is set to 12～18W , the sputtering current is 0.03~0.0375A, the sputtering voltage is 400~480 V, and the sputtering time is 200~250 s. 8. Application of the flexible humidity sensor based on MoOx nanoparticle assembly material according to any one of claims 1-4 in detecting ambient humidity.

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