A material identification sensor and a method for identifying material properties using the same

Abstract

The present invention relates to a material identification sensor and a method for identifying material properties using the same. The material identification sensor comprises, from top to bottom, an encapsulation layer, a temperature measurement layer, and a base layer connected in sequence. The temperature measurement layer comprises a circular heat source and a circular temperature sensor, wherein the circular heat source is disposed within the circular temperature sensor. The material identification sensor of the present invention utilizes a specific structure comprising a central ring heat source and an outer ring temperature measurement, enabling effective differentiation between materials with similar thermal properties. The method of the present invention places a fixed volume of material to be tested on the material identification sensor, generates constant power from the heat source, and measures the resistance change of the circular temperature sensor. Materials with different densities and specific heat capacities exhibit different resistance-time curves, which simultaneously satisfy a logarithmic relationship. Eigenvalues are obtained by fitting the resistance-time curves, and material properties are identified based on the eigenvalues.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a material identification sensor and a method for identifying material properties using the same. Background Art

[0002] With the rapid development of the Internet of Things and 5G, there is an increasing demand for devices capable of sensing acoustic, optical, electrical, thermal, and magnetic fields in the environment. In recent years, researchers have conducted extensive research in temperature, pressure, and humidity sensing, achieving significant progress in device miniaturization and flexibility. However, research on devices capable of identifying object materials is relatively limited. To date, the majority of material identification devices reported in the literature are simplified versions of the transient planar heat source method, which measures the thermal conductivity of materials. These devices use a thin metal disk ring structure as both a planar heat source and a temperature sensor. During testing, the object to be tested is placed on the sensor, and a voltage is applied to the metal thermistor to increase its temperature. The change in resistance is used to characterize the thermal conductivity, allowing the identification of different materials. For example, see (Adv. Mater. 2017, 29, 1606151; Sci. Robot. 2020, 5, eabc8134).

[0003] CN108548844 A discloses a thermal property sensor that uses a circular heating excitation center point for temperature measurement. By separating the heater and temperature sensor, the influence of contact thermal resistance is avoided, enabling fast and efficient measurement of thermal conductivity and thermal diffusivity. This sensor can accurately and quickly measure the thermal properties of materials, thereby enabling material differentiation. However, this type of detection technology cannot effectively distinguish materials with similar thermal properties. Therefore, there is an urgent need to develop sensors and methods based on other properties for identification.

[0004] In view of the above reasons, the present invention is particularly highlighted. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a material identification sensor and a method for identifying material properties using the same. The sensor of the present invention identifies properties based on the density and specific heat capacity of the object to be measured. The method of the present invention distinguishes and identifies materials by fitting the corresponding characteristic values through the resistance and time change curves of materials with different properties.

[0006] The first purpose of the present invention is to provide a material identification sensor, which includes a packaging layer, a temperature measuring layer and a base layer connected in sequence from top to bottom. The temperature measuring layer includes a circular heat source and a circular temperature sensor. The circular heat source is arranged inside the circular temperature sensor.

[0007] Furthermore, the annular heat source is laser-induced graphene obtained by laser irradiation of the substrate layer, the annular temperature sensor is a thermistor, and the annular temperature sensor is fixed on the substrate layer by thermal evaporation or magnetron sputtering.

[0008] Furthermore, the two ends of the circular heat source are respectively connected to a first electrode and a second electrode, and the first electrode and the second electrode are connected to a power supply. The two ends of the circular temperature sensor are respectively connected to a third electrode and a fourth electrode, and the third electrode and the fourth electrode are connected to a resistance tester.

[0009] Furthermore, the first electrode, the second electrode, the third electrode and the fourth electrode are all on the same plane.

[0010] Furthermore, the encapsulation layer is made of electrically insulating material.

[0011] Preferably, the electrical insulating material is polydimethylsiloxane (PDMS), which is spin-coated on the temperature measuring layer and the base layer and cured by heat treatment.

[0012] Furthermore, the base layer is made of polyimide.

[0013] A second object of the present invention is to provide a method for identifying material properties using the sensor, the method comprising the following steps:

[0014] (1) Placing multiple materials with different known properties on the packaging layer, recording the change of resistance over time on a resistance tester connected to the annular temperature sensor, and obtaining multiple resistance-time change curves;

[0015] (2) intercepting the resistance-time variation curve of each material with known properties within 10-60s, fitting the intercepted resistance-time variation curve according to the formula y = A1·е^(-x / t1)+y0, and obtaining different characteristic values t1 for different materials. A database of materials with known properties and characteristic values t1 is established;

[0016] (3) Place the unknown material on the packaging layer of the sensor, and calculate the characteristic value t2 of the unknown material according to the method of steps (1) and (2).

[0017] (4) Compare the characteristic value t2 of the unknown material with the characteristic value t1 in the database established in step (2) to determine the material of the unknown material.

[0018] The present invention adopts orgin software to perform fitting according to the formula y=A1·е^(-x / t1)+y0.

[0019] Furthermore, the multiple materials with different known properties described in step (1) include silicone rubber, glass, stainless steel, aluminum nitride, brass, copper and plastic.

[0020] Furthermore, in the multiple resistance-time variation curves in step (1), the time is 0-70s, and the volumes of the multiple materials with different known properties and the materials with unknown properties are the same.

[0021] Furthermore, in step (4), if the characteristic value t2 = 0.95t1 to 1.05t1, the unknown attribute material is determined to be the known attribute material corresponding to the t1 value.

[0022] Furthermore, the material with unknown properties is one of the multiple materials with different known properties.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The material identification sensor of the present invention, with its unique structure of a central ring heat source and an outer ring temperature measurement, can effectively distinguish materials with similar thermal properties. The material identification sensor identifies the material based on the sealing and specific heat capacity of the object to be tested.

[0025] (2) The method of the present invention places a fixed volume of the material to be tested on the material identification sensor, generates a constant power from the heat source, and tests the resistance change of the annular temperature sensor. Materials with different densities and specific heat capacities will show different resistance-time curves, and the two satisfy a logarithmic relationship. The characteristic value is obtained by fitting the resistance-time curve, and the material properties are identified based on the characteristic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a structural diagram of a material identification sensor of the present invention;

[0028] Figure 2 This is a structural diagram of a material identification sensor of the present invention;

[0029] Figure 3 This is the simulation result of the effect of thermal conductivity on the temperature-time curve at the probe in the present invention;

[0030] Figure 4 is the simulation result of the effect of density on the temperature-time curve at the probe in the present invention;

[0031] Figure 5 is the simulation result of the influence of specific heat capacity on the temperature-time curve at the probe in the present invention;

[0032] Figure 6 This is a graph showing the temperature variation of the annular heat source under different voltages of the material identification sensor of the present invention;

[0033] Figure 7 This is a graph showing the resistance change of the annular temperature sensor in the material identification sensor of the present invention at different temperatures;

[0034] Figure 8 It is the actual test curve and fitting curve of silicone rubber;

[0035] Figure 9 It is the actual test curve and fitting curve of the glass;

[0036] Figure 10 It is the actual test curve and fitting curve of stainless steel;

[0037] Figure 11 It is the actual test curve and fitting curve of aluminum nitride;

[0038] Figure 12 It is the actual test curve and fitting curve of brass;

[0039] Figure 13 It is the actual test curve and fitting curve of copper;

[0040] Figure 14 It is the actual test curve and fitting curve diagram of plastic.

[0041] Reference numerals

[0042] 1- packaging layer, 2- annular heat source, 21- third electrode, 22- fourth electrode, 3- annular temperature sensor, 31- first electrode, 32- second electrode, 4- base layer, 5- material to be tested. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] like Figure 1 and 2As shown, a material identification sensor of this embodiment includes a packaging layer 1, a temperature measuring layer and a base layer 4 connected in sequence from top to bottom. The temperature measuring layer includes a circular heat source 2 and a circular temperature sensor 3. The circular heat source 2 is arranged inside the circular temperature sensor 3. The packaging layer 1 is made of polydimethylsiloxane material, and the base layer 2 is made of polyimide.

[0046] In a further embodiment, the annular heat source 2 is laser-induced graphene obtained by laser irradiation of the substrate layer 4, the annular temperature sensor 2 is a thermistor, and the annular temperature sensor 3 is fixed to the substrate layer 4 by magnetron sputtering. The annular heat source 2 is connected to a first electrode 31 and a second electrode 32 at both ends, respectively. The first electrode 31 and the second electrode 32 are connected to a DC adjustable power supply. The annular temperature sensor 3 is connected to a third electrode 21 and a fourth electrode 22 at both ends, respectively. The third electrode 21 and the fourth electrode 22 are connected to a resistance tester. The first electrode 31, the second electrode 32, the third electrode 21, and the fourth electrode 22 are all on the same plane.

[0047] In this embodiment, the outer radius of the annular heat source 2 is 3-8 mm, the width is 1-5 mm, and the thickness is less than 10 μm. The outer radius of the annular temperature sensor 3 is 10-20 mm, and the width is 40-100 μm. The material 5 to be tested is placed on the packaging layer 1 of the material identification sensor for testing.

[0048] Example 2

[0049] This embodiment is a method for identifying material properties using the material identification sensor prepared in Example 1. The method is based on the following theory:

[0050] Simulation and physical model building:

[0051] According to the structure, size and material of the sensor described in Example 1, a model was constructed in Comsol for simulation. The ambient temperature was set to 20°C and the heat source power was given. A probe was placed at the temperature sensor to simulate the effect of the properties of the placed material (thermal conductivity, density and specific heat capacity) on the change of the "temperature-time" curve at the probe. The simulation results are shown in Figure 2. Figure 3-5 As shown, from Figure 3 It can be seen that as the thermal conductivity of the material changes from 0.0381W / (m·K) to 38100W / (m·K), the "temperature-time" curve at the probe has almost no change, which shows that the change in thermal conductivity of the material does not affect the test results; Figure 4 and 5It can be seen that when the density and specific heat capacity of the material change, the "temperature-time" relationship will change accordingly. The temperature change of the circular heat source under different voltages of the material identification sensor of the present invention is as follows: Figure 6 As shown, the resistance change of the annular temperature sensor at different temperatures in the material identification sensor of the present invention is as follows: Figure 7 shown.

[0052] The above simulation model shows that density and specific heat capacity are two factors that affect the shape of the curve. The simulation results show that the heat absorption process leads to temperature changes at the probe, and the heat absorbed by the material (E) is equal to the heat generation power (W) of graphene minus the heat dissipation in the air. The following formula can be obtained:

[0053]

[0054] Where α is the convective heat transfer coefficient, ρ is the density of the test material, C is the specific heat capacity of the material, V is the volume of the material, T is the temperature of the material, T A is the ambient temperature, and t is the time. After transformation, the formula can be obtained:

[0055]

[0056] From the above formula, we can see that under the condition of fixed test material volume, the temperature at the probe is in a logarithmic relationship with time, and the coefficient of t (α / Cρ) affects the shape of the curve. Materials with different densities and specific heat capacities have different coefficients, which can be used to calibrate and identify different materials. Since the temperature and resistance of the circular temperature sensor used are linearly related, such as Figure 7 Therefore, the change in resistance is also logarithmically related to time. Therefore, the present invention adopts the formula y=A1·е^(-x / t1)+y0 for fitting.

[0057] The material attribute identification method of this embodiment is as follows:

[0058] (1) Aluminum nitride, stainless steel, brass, copper, glass, plastic, and silicone rubber are placed on the packaging layer 1 of the sensor respectively, and the change of resistance over time on the resistance tester connected to the annular temperature sensor is recorded to obtain multiple resistance-time change curves, and the test time is 0-70s; (2) The resistance-time change curve of each known property material within 10-60s is intercepted, and the intercepted resistance-time change curve is fitted in the origin software according to the formula y=A1·е^(-x / t1)+y0. Different materials obtain different characteristic values t1, and a database of known property materials and characteristic values t1 is established; wherein, Figure 8 It is the actual test curve and fitting curve of silicone rubber. Figure 9 It is the actual test curve and fitting curve of the glass. Figure 10 It is the actual test curve and fitting curve of stainless steel. Figure 11 This is the actual test curve and fitting curve of aluminum nitride. Figure 12 This is the actual test curve and fitting curve of brass. Figure 13 It is the actual test curve and fitting curve of copper. Figure 14 The actual test curve and fitting curve of plastic are shown in Table 1. The t1 values of different materials obtained by formula fitting are shown in Table 1.

[0059] Table 1

[0060] Material Aluminum nitride Stainless steel brass copper Glass plastic silicone rubber <![CDATA[t1]]> 36.6 67.7 54.1 53.6 -88.9 -50.6 -42.6

[0061] (3) Place the unknown material on the packaging layer of the sensor, and calculate the characteristic value t2 of the unknown material according to the method of steps (1) and (2).

[0062] (4) Compare the characteristic value t2 of the unknown attribute material with the characteristic value t1 in the database established in step (2). If the characteristic value t2 = 0.95t1 ~ 1.05t1, the unknown attribute material is determined to be the known attribute material corresponding to the t1 value. Otherwise, the type of the unknown attribute material cannot be determined.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for identifying material properties, characterized in that: The method uses a material identification sensor to determine the material of an unknown material. The sensor includes, from top to bottom, a packaging layer, a temperature measurement layer, and a base layer connected in sequence. The temperature measurement layer includes a circular heat source and a circular temperature sensor. The circular heat source is disposed inside the circular temperature sensor. The method comprises the following steps: (1) Placing multiple materials with different known properties on the packaging layer, recording the change of resistance over time on a resistance tester connected to the annular temperature sensor, and obtaining multiple resistance-time change curves; (2) intercepting the resistance-time variation curve of each material with known properties within 10-60s, fitting the intercepted resistance-time variation curve according to the formula y = A1·е^(-x / t1)+y0, and obtaining different characteristic values t1 for different materials. A database of materials with known properties and characteristic values t1 is established; (3) Place the unknown material on the packaging layer of the sensor, and calculate the characteristic value t2 of the unknown material according to the method of steps (1) and (2). (4) Compare the characteristic value t2 of the unknown material with the characteristic value t1 in the database established in step (2) to determine the material of the unknown material.

2. The method for identifying material properties according to claim 1, characterized in that: The multiple materials with different known properties described in step (1) include silicone rubber, glass, stainless steel, aluminum nitride, brass, copper and plastic, and the time in the multiple resistance-time change curves is 0-70s.

3. The method for identifying material properties according to claim 1, characterized in that: In step (4), if the characteristic value t2 = 0.95t1 ~ 1.05t1, the unknown attribute material is determined to be the known attribute material corresponding to the t1 value; otherwise, the type of the unknown attribute material cannot be determined.

4. The method for identifying material properties according to claim 1, wherein: The material of unknown property is one of the multiple materials of different known properties, and the multiple materials of different known properties and the material of unknown property have the same volume.

5. The method for identifying material properties according to claim 1, characterized in that: The annular heat source is laser-induced graphene obtained by laser irradiation of a substrate layer, the annular temperature sensor is a thermistor, and the annular temperature sensor is fixed on the substrate layer by thermal evaporation or magnetron sputtering.

6. The method for identifying material properties according to claim 1 or 2, characterized in that: The two ends of the annular heat source are respectively connected to a first electrode and a second electrode, and the first electrode and the second electrode are connected to a power supply. The two ends of the annular temperature sensor are respectively connected to a third electrode and a fourth electrode, and the third electrode and the fourth electrode are connected to a resistance tester.

7. The method for identifying material properties according to claim 6, characterized in that: The first electrode, the second electrode, the third electrode and the fourth electrode are all on the same plane.

8. The method for identifying material properties according to claim 1, characterized in that: The packaging layer is made of electrically insulating material.

9. The method for identifying material properties according to claim 1, characterized in that: The base layer is made of polyimide.

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