A method, sensor and system for fast contact measurement of thermal conductivity of an object based on early transient thermal response

Abstract

The application discloses a kind of object thermal conductivity contact type fast measurement method, sensor and system based on early transient thermal response, belong to flexible sensor and thermophysical property detection technical field.The application is measured unit with pre-calibrated resistance-temperature relationship thin film thermistor, after being contacted with measured object, obtains initial temperature of contact interface under low self-heating readout condition;Short pulse thermal excitation is applied to the same measurement unit, current and voltage signals are collected in early time window after pulse start, resistance-time and temperature-time response are obtained;Combined with early transient thermal response characteristics, contact interface initial temperature and substrate and packaging layer thermal parameters, the thermal conductivity of measured object is calculated.The application can complete thermal conductivity measurement in millisecond without waiting for second-level heat diffusion or heat balance, and has simple structure, fast measurement, small thermal load, and is easy to integrate with flexible electronic skin and robot tactile interface.

Description

Technical Field

[0001] This invention belongs to the field of flexible sensor and thermal property detection technology, specifically relating to a contact-based rapid measurement method, sensor and system for thermal conductivity of objects based on early transient thermal response. Background Technology

[0002] Thermal conductivity is an important thermophysical property parameter characterizing a material's heat transfer capability. In scenarios such as tactile perception in biomimetic robots, flexible electronic skin, human-computer interaction, rapid material identification, thermal detection of irregular curved surfaces, and monitoring of biological contact interfaces, tactile interfaces not only need to sense mechanical information such as force, displacement, and texture, but also need to quickly obtain the thermal characteristics of the object being contacted. Among these, the thermal conductivity of the object being measured reflects its heat absorption, dissipation, and heat diffusion capabilities, making it a key parameter in material property judgment and contact safety assessment.

[0003] Traditional methods for measuring thermal conductivity include the transient planar heat source method (TPS), the hot-wire method, and the 3-Omega method. These methods typically utilize electrical heating to induce a temperature response, and then inversely derive thermal parameters based on the temperature change over time. While these methods are valuable for standard material testing and laboratory thermophysical property measurement, they usually rely on large sensing structures, relatively sufficient heat diffusion processes, or long timescale model fitting. Measurement times often range from several seconds to several minutes or even longer, making it difficult to meet the requirements of miniaturization, flexibility, low thermal load, and rapid contact detection in flexible electronic skin and robotic tactile arrays.

[0004] Some existing tactile thermal sensing solutions employ separate heating and temperature measurement zones, or combine them with pressure detection units to improve measurement consistency. These solutions can achieve a certain degree of thermal property measurement, but their structural complexity is high, and array integration is difficult. At the same time, if they rely on thermal diffusion processes and temperature curve fitting over a long timescale, they are not conducive to quickly determining the thermal properties of the object being measured in the early stages of a single touch.

[0005] Thin-film thermistors possess characteristics such as low thermal capacity, fast response, miniaturization, and flexible integration. Thin-film conductive materials with calibrable resistance-temperature relationships, such as platinum, gold, nickel, chromium, titanium, indium tin oxide, metal oxides, carbon-based conductive materials, metal nanowires, conductive polymers, or their composites, can all exhibit a resistance-temperature response under electrical excitation. Platinum thin films, for example, possess good chemical stability, a linear temperature coefficient of resistance, and process compatibility, making them a preferred material for thin-film thermistors.

[0006] Therefore, there is still a need to provide a contact-based rapid measurement method and sensor for thermal conductivity of flexible contact interfaces, which can utilize the transient thermal response of thin-film thermistors in the early stage of short-pulse thermal excitation to quickly invert the thermal conductivity of the measured object without waiting for long-term thermal diffusion or thermal equilibrium, and can adjust the short-pulse thermal excitation parameters according to the response amplitude or the range of thermal conductivity of the measured object. Summary of the Invention

[0007] The first technical problem this invention aims to solve is to provide a contact-based rapid measurement method for the thermal conductivity of objects based on early transient thermal response. This method utilizes the transient thermal response of a thin-film thermistor in the early stage of short-pulse thermal excitation to rapidly invert the thermal conductivity of the measured object within a millisecond-level early time window without waiting for long-term thermal diffusion or thermal equilibrium. The second technical problem this invention aims to solve is to provide a contact-based rapid measurement sensor for the thermal conductivity of objects based on early transient thermal response. This sensor is adaptable to various thermistor conductive materials and thin-film fabrication processes, meeting the integration requirements of flexible electronic skin and robotic tactile interfaces. The third technical problem this invention aims to solve is to provide a contact-based rapid measurement system for the thermal conductivity of the measured object. This system can automatically complete low self-heating initial temperature readout, graded adaptive short-pulse thermal excitation, early transient response acquisition, and rapid thermal conductivity inversion, and supports contact state monitoring and pressure compensation, significantly improving the consistency, repeatability, and measurement efficiency under different contact conditions.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A rapid contact measurement method for the thermal conductivity of an object based on early transient thermal response includes the following steps:

[0010] 1) A thin-film thermistor measurement unit with a pre-calibrated resistance-temperature relationship is used to form a thermal conduction interface with the object being measured, and the initial temperature of the contact interface is obtained under low self-heating readout conditions.

[0011] 2) Apply a short pulse thermal excitation to the same thin-film thermistor measurement unit, and collect current and voltage signals in the early time window after the pulse starts to obtain the resistance-time and temperature-time responses;

[0012] 3) The thermal conductivity of the object under test is calculated by combining the early transient thermal response characteristics, the initial temperature of the contact interface, and the thermal parameters of the substrate and the encapsulation layer; wherein the early time window does not exceed 100 ms, and the measurement process does not require waiting for second-level thermal diffusion or thermal equilibrium.

[0013] Furthermore, the low self-heating readout condition is that the Joule heating generated by the applied readout voltage, current, or short pulse causes the temperature rise of the thin-film thermistor measurement unit to be less than 0.1 ℃, and the collected initial resistance only reflects the initial temperature of the contact interface.

[0014] Furthermore, the short-pulse thermal excitation is a voltage pulse, current pulse, or power pulse, and a graded adaptive excitation method is adopted: first, a low-energy probe pulse is applied, and when the response amplitude is lower than a preset threshold, the pulse amplitude or width is gradually increased to adapt to the test objects with different thermal conductivity.

[0015] Furthermore, the early transient thermal response characteristics include one or more combinations of temperature rise at a fixed time point, initial temperature rise slope, early temperature rise integral, temperature rise peak, peak arrival time, and cooling slope.

[0016] Furthermore, by limiting the contact state through contact pressure detection, force control execution, or contact displacement control, the contact pressure is used as a compensation variable input into the thermal conductivity inversion model to improve measurement consistency.

[0017] A contact-based rapid measurement sensor for object thermal conductivity based on early transient thermal response includes a flexible support layer, a thin-film thermistor measurement unit, a conductive lead-out area, and an insulating encapsulation layer. The thin-film thermistor measurement unit is a continuous conductive area that combines low self-heating temperature readout with short-pulse transient self-heating functionality. The conductive lead-out area has a low-resistance conductive structure to reduce lead contact resistance. The insulating encapsulation layer covers the surfaces of the measurement unit and the conductive lead-out area.

[0018] Furthermore, the flexible support layer is selected from one of polyimide, polyethylene terephthalate, polyethylene naphthalate, polydimethylsiloxane, polyurethane, silicone rubber, thin glass, ultrathin silicon wafer or flexible composite film.

[0019] Furthermore, the insulating encapsulation layer is selected from one or more of PDMS, phenelzine, polyimide, polyurethane, and epoxy resin.

[0020] Furthermore, the material of the thin-film thermistor measurement unit is one of platinum, gold, nickel, chromium, titanium, indium tin oxide, metal oxide, carbon-based material, metal nanowire, or conductive polymer.

[0021] A contact-based rapid measurement system for the thermal conductivity of an object under test includes a sensor, an excitation acquisition module, and a data processing module. The excitation acquisition module is used to output graded short-pulse thermal excitation and acquire early electrical signals. The data processing module is used for resistance-temperature conversion, transient feature extraction, and thermal conductivity inversion.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The present invention uses the early transient thermal response after the start of short pulse thermal excitation to determine the thermal conductivity of the object under test. There is no need to wait for the second-level thermal diffusion or long thermal equilibrium process. The effective measurement time of a single measurement can not exceed 100 ms, and preferably the effective features for thermal conductivity inversion can be obtained within 20 ms.

[0024] (2) The present invention uses the same continuous thin film thermistor measurement area to complete the low self-heating resistance readout and short pulse transient self-heating. The structure is simple and is conducive to miniaturization, flexibility and array integration.

[0025] (3) The present invention allows the use of one or more short pulse thermal excitations, and the subsequent pulse parameters can be adjusted according to the response amplitude, temperature rise amplitude, signal-to-noise ratio or preset temperature rise threshold, thereby taking into account the measurement discrimination of objects with low thermal conductivity and high thermal conductivity.

[0026] (4) The thin film thermistor measuring unit in this invention can be prepared using a variety of thermistor conductive materials with calibrable resistance-temperature relationship. The excitation method can be selected as voltage pulse, current pulse or power pulse. The preparation process can be sputtering, evaporation, printing, transfer or photolithography patterning.

[0027] (5) The present invention can use the thermal parameters of the substrate and the packaging layer as known or pre-calibrated parameters, and can introduce pressure sensors, force control actuators, contact displacement control or pressure threshold screening mechanisms to control the contact state, thereby improving the consistency of thermal conductivity inversion under different contact conditions. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the sensor structure of this application;

[0029] Figure 2 The graph shows the resistance response of the flexible sensor of this application at different temperatures;

[0030] Figure 3 This is a test graph showing the response time of the flexible sensor in this application when it comes into contact with objects at different temperatures;

[0031] Figure 4 This is a thermal image of the sensing area of ​​the flexible sensor in this application after pulse excitation;

[0032] Figure 5 This is a graph showing the resistance change of the flexible sensor in this application when it comes into contact with samples of different thermal conductivity.

[0033] Figure 6 This is a resistance response diagram within an early time window when the flexible sensor of this application comes into contact with samples of different thermal conductivity.

[0034] Figure 7 This is a schematic diagram of the sensor structure with a contact pressure detection unit according to this application;

[0035] Figure 8 This is a graph showing the repeatability data of the flexible sensor in this application during multiple no-load tests;

[0036] The components are: 1. High-resistivity sensing area; 2. Low-resistivity conductive area; 3. Pyrelin encapsulation layer; 4. Polydimethylsiloxane (PDMS) protective layer; 5. Silver paste lead area; 6. Polyimide (PI) flexible support layer.

[0037] 7. Thermistor electrode; 8. Platinum sputtered layer; 9. Pyrelin protective layer; 10. PI flexible support layer; 11. Pressure-sensitive electrode; 12. Velostat pressure-sensitive layer; 13. PDMS. Detailed Implementation

[0038] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0039] In the following examples, the polyamic acid type polyimide precursor solution, high-purity platinum target, anhydrous ethanol, conductive silver paste, enameled wire, polydimethylsiloxane, and phenelzine F are all commercially available products and do not require special preparation.

[0040] The detection principle of the following embodiments:

[0041] This application utilizes the early transient thermal response of a thin-film thermistor measurement unit under short-pulse thermal excitation to achieve rapid contact measurement of the thermal conductivity of the object under test. The thin-film thermistor measurement unit has a pre-calibrated resistance-temperature relationship and simultaneously features resistance-type temperature readout and Joule self-heating function within the same continuous conductive region.

[0042] During the measurement process, the thin-film thermistor measurement unit is first brought into contact with the object under test to form a thermally conductive interface. Before applying a short thermal excitation pulse, the initial resistance response of the thin-film thermistor measurement unit is acquired under low self-heating readout conditions, and the initial temperature of the contact interface is obtained according to a pre-calibrated resistance-temperature relationship. The low self-heating readout condition means that the Joule heat generated by the applied readout voltage, current, or short pulse is insufficient to cause a temperature rise exceeding a preset threshold, so that the obtained resistance response mainly reflects the initial temperature of the contact interface.

[0043] Subsequently, one or more short-pulse thermal excitations are applied to the same thin-film thermistor measurement unit, causing a transient temperature rise within a millisecond to sub-second timescale. Part of the heat generated by the thin-film thermistor measurement unit diffuses to the substrate and encapsulation layer, while the other part is conducted to the object under test via the contact interface. Since the thermal parameters of the substrate, encapsulation layer, and thin-film thermistor measurement unit can be predetermined or calibrated, under the same device structure and contact conditions, the thermal conductivity of the object under test becomes a crucial factor affecting the early temperature response of the thin-film thermistor measurement unit.

[0044] When the measured object has a high thermal conductivity, it can dissipate the heat generated by the thin-film thermistor measurement unit more quickly, resulting in a lower temperature rise amplitude, a smaller early temperature rise slope, or a faster cooling process. Conversely, when the measured object has a low thermal conductivity, heat diffuses more slowly, leading to a higher temperature rise amplitude or a slower thermal diffusion process. Therefore, measured objects with different thermal conductivity will exhibit distinguishable transient thermal response differences within the early time window after the start of short-pulse thermal excitation.

[0045] By frequently acquiring the current and / or voltage responses of the thin-film thermistor measurement unit during and / or after short-pulse thermal excitation, the resistance-time curve of the thin-film thermistor measurement unit can be calculated, and the temperature-time curve can be obtained further based on the resistance-temperature calibration relationship. Subsequently, temperature response characteristics are extracted within the early time window, such as temperature rise at a fixed time point, initial temperature rise slope, early temperature rise integral, temperature rise peak, peak arrival time, cooling slope, normalized temperature response curve shape, or combinations thereof. The thermal conductivity of the measured object is then calculated based on analytical heat conduction models, equivalent thermal resistance-heat capacity models, finite element models, standard sample calibration mapping relationships, or data-driven models.

[0046] The early time window can be no more than 100 ms after the start of the short-pulse thermal excitation. Since this invention utilizes the transient thermal response characteristics of the early stage of short-pulse thermal excitation, there is no need to wait for a long thermal diffusion process or thermal equilibrium process, and the thermal conductivity of the object under test can be rapidly measured in the early stage of a single contact.

[0047] First, a short-pulse thermal excitation with low energy is applied for exploratory measurements. When the obtained resistance change, temperature rise amplitude, early response slope, or signal-to-noise ratio is lower than a preset threshold, a short-pulse thermal excitation with higher energy is applied to improve the response differentiation between measured objects with different thermal conductivities. Therefore, this application is not limited to single-power or dual-power pulse modes, and can employ single-shot, graded, or adaptive short-pulse thermal excitation methods.

[0048] The contact state between the thin-film thermistor measurement unit and the object under test can also be controlled by a contact pressure detection unit, an external force control mechanism, or a contact state screening algorithm, so that the measurement is carried out within a preset contact force range, or the contact pressure can be used as a compensation variable to input into the thermal conductivity inversion model to improve the consistency and repeatability of rapid contact thermal conductivity measurement.

[0049] Example 1

[0050] Sensor fabrication method:

[0051] (1) Preparation of flexible polyimide substrate: A flat glass plate was selected as the carrier. The glass plate was ultrasonically cleaned in anhydrous ethanol for 3 min, then dried in an 80 ℃ oven for 10 min and cooled to room temperature for later use. The polyamic acid type polyimide precursor solution was dropped or poured onto the surface of the glass plate and a uniform liquid film was formed by spin coating. The spin coating parameters could be set to 800 r / min and the spin coating time was 30 s. Then the glass plate coated with the precursor liquid film was placed in an oven for gradient heating thermal imidization. The heating program was: 100 ℃ for 20 min, 150 ℃ for 20 min, 200 ℃ for 20 min, and 280 ℃ for 20 min. After curing, the plate was cooled to room temperature in the oven and the formed polyimide film was peeled off from the glass plate to obtain a flexible polyimide substrate with a thickness of about 0.025 mm.

[0052] (2) Fabrication of the thin-film thermistor measurement unit: A flexible polyimide substrate was fixed on the sample stage of a magnetron sputtering device. After evacuation, a high-purity platinum target was used for sputtering deposition. The sputtering parameters were set to a sputtering power of 200 W, a substrate rotation speed of 8 r / min, and a sputtering time of 90 s to form a platinum thin film on the surface of the flexible polyimide substrate. Subsequently, the platinum thin film was patterned by laser etching to form the thin-film thermistor measurement area and the conductive lead-out area. The laser etching parameters were set to a processing speed of 1000 mm / s and a laser frequency of 30 kHz.

[0053] (3) Lead connection and encapsulation: The stripped end of the enameled wire is placed on the surface of the conductive lead-out area and fixed with conductive silver paste, then cured at 90 ℃ for 1 h to form a stable electrical connection. Next, polydimethylsiloxane adhesive and curing agent (Dow Corning Sylgard 184) are mixed at a mass ratio of 10:1, thoroughly stirred and degassed, and then coated or spin-coated onto the measurement area of ​​the thin-film thermistor, followed by curing at 80 ℃ for 1 h to form a flexible protective layer. Finally, a Parylene F encapsulation layer is formed on the surface of the functional area by chemical vapor deposition to obtain a flexible sensor for rapid contact measurement of thermal conductivity.

[0054] The sensor structure includes a flexible substrate, a thin-film thermistor measurement unit disposed on the flexible substrate, a conductive lead-out area, and an insulating encapsulation layer covering it. For example... Figure 1 As shown, the flexible sensor includes a polyimide (PI) flexible support layer 6, a silver paste lead area 5 disposed on the upper surface of the polyimide (PI) flexible support layer 6, and a patterned platinum functional layer. The patterned platinum functional layer includes a high-resistance sensing area 1 and a low-resistance conductive area 2; the upper surfaces of the high-resistance sensing area 1, the low-resistance conductive area 2, and the silver paste lead area 5 are sequentially covered with a PDMS protective layer 4 and a Pyrelin encapsulation layer 3. The high-resistance sensing area 1 is a thin-film thermistor measurement unit, which has both low self-heating resistance readout and short-pulse transient self-heating functions within the same continuous conductive area; the low-resistance conductive area 2 serves as the electrode lead-out area, reducing lead contact resistance and ensuring the stability of power supply and signal acquisition.

[0055] The sensor prepared in Example 1 was subjected to performance testing.

[0056] 1. Resistance-temperature relationship calibration

[0057] The sensor prepared in Example 1 was placed in a constant temperature and humidity chamber at different known temperatures (30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃) and stabilized for 15 min. The resistance value of the thin-film thermistor measuring unit was measured using a digital source meter or an equivalent excitation and acquisition circuit under low self-heating readout conditions (applied 10 μA constant current readout signal). Low self-heating readout conditions refer to conditions where the Joule heat generated by the applied readout voltage, current, or short pulse is insufficient to cause a temperature rise exceeding a preset threshold (less than 0.1 ℃), so that the measured resistance primarily reflects the temperature of the interface where the thin-film thermistor measuring unit is located.

[0058] Resistance was collected at various temperature points and linear fitting was performed to establish a resistance-temperature calibration relationship.

[0059] R = R0[1 + α(T - T0)]

[0060] Where R is the resistance value at temperature T, R0 is the resistance value at reference temperature T0 (the reference temperature can be 25 ℃), and α is the temperature coefficient of resistance.

[0061] By obtaining the linear relationship between resistance and temperature through calibration, the resistance-time curve during the measurement process can be converted into a temperature-time curve. The results are shown below. Figure 2 .

[0062] Figure 2The resistance response of the thin-film thermistor unit at different temperatures was measured. It was found that, relying on the extremely low heat capacity of the Pt thin-film sensing unit, the sensor can quickly reach thermal equilibrium with samples at different initial temperatures (e.g., ΔT = 20 ℃). Testing showed a temperature response time of up to 100 ms, meeting real-time detection requirements. Using 25 ℃ as a reference temperature, the reference resistance of the sensor and the real-time resistance after contact with the sample were acquired using a digital source meter. Based on the excellent linear resistance-temperature characteristics of the Pt thin film, a temperature conversion function was established to inversely calculate the temperature of the sample. After calibration, the temperature detection result of the sensor deviated from the actual temperature of the standard temperature range sample by ≤ ±0.5 ℃, demonstrating excellent resistance-temperature linearity and outstanding long-term detection stability and reliability.

[0063] 2. Low self-heating readout to obtain the initial temperature of the contact interface

[0064] The thin-film thermistor measurement unit is brought into contact with the object under test to form a thermal conduction interface. A low self-heating readout signal (10 μA constant current signal) is applied to the thin-film thermistor measurement unit. The Joule heat generated by this signal causes the unit to self-heat and rise in temperature by less than 0.1 ℃. Under low self-heating readout conditions, the initial resistance value of the thin-film thermistor measurement unit is acquired. The initial resistance value is then substituted into a pre-calibrated resistance-temperature linear relationship to calculate the initial temperature of the contact interface. The results are shown below. Figure 3 .

[0065] Depend on Figure 3 It can be seen that the sensor can complete the initial temperature acquisition of the contact interface within ≤100 ms, and the temperature detection result deviates from the actual temperature of the standard temperature level sample by ≤±0.5 ℃. The low self-heating readout will not interfere with subsequent thermal excitation measurements, and the initial temperature can be used as a reliable initial boundary condition for thermal conductivity inversion.

[0066] 3. Acquisition of short-pulse thermal excitation and early transient response

[0067] After initial temperature acquisition at the contact interface, graded adaptive short-pulse thermal excitation was applied to the same thin-film thermistor measurement unit. The first round applied a 20 V, 20 ms voltage pulse as an exploratory thermal excitation. During and after the pulse excitation, the current and voltage signals of the thin-film thermistor measurement unit were synchronously acquired in a high-frequency sampling mode. The resistance-time curve was calculated from the acquired electrical signals, and then converted into a temperature-time curve based on the resistance-temperature calibration relationship. If the temperature rise amplitude and response slope under the first pulse were lower than a preset threshold, the pulse parameters were gradually increased to 40 V, 40 ms until a resolvable early transient thermal response was obtained. Temperature response data within the early time window of 0–20 ms after the short-pulse thermal excitation was initiated were extracted. Results are shown below. Figure 4-5 .

[0068] Depend on Figure 4-5It is evident that the thin-film thermistor measurement unit can complete self-heating and temperature response acquisition within the same area, eliminating the need for separate heating / temperature measurement zones. The graded pulse strategy is adaptable to samples with a full range of thermal conductivity, from low to high, ensuring a high signal-to-noise ratio and high discrimination. The early transient thermal response can stably characterize the thermal conductivity difference of the measured object within 20 ms, without waiting for a long period of thermal diffusion. The temperature-time curve clearly reflects the rate of thermal conduction of the object and can be directly used for subsequent thermal conductivity inversion calculations.

[0069] 4. Early time window feature extraction and thermal conductivity inversion

[0070] The temperature-time curve within the early time window of 0-20 ms after the short-pulse thermal excitation is used as the data source for analysis. Characteristic parameters such as temperature rise at fixed time points, initial temperature rise slope, early temperature rise integral, peak arrival time, and cooling slope are extracted from the curve. Using standard samples with known thermal conductivity (quartz glass, PP, stainless steel, brass, wood products, and cast iron), tests are conducted under the same contact conditions and pulse excitation conditions. A calibration mapping relationship between characteristic parameters and thermal conductivity is established, forming a standard inversion model. The early characteristic parameters of the tested object with unknown thermal conductivity are substituted into the model to calculate the thermal conductivity of the tested object. The average relative error of the inversion results is calculated based on the nominal thermal conductivity of the standard sample. Results are shown below. Figure 5-6 .

[0071] Depend on Figure 5-6 It is evident that the method effectively distinguishes objects with different thermal conductivity levels using only the early transient response within 0–20 ms, without requiring a wait of seconds for thermal equilibrium. The average relative error between the retrieved thermal conductivity and the nominal value of the standard sample is 1.4%, demonstrating high measurement accuracy. Even when the time window is extended to 50 ms and 100 ms, the inversion error remains less than 1.5%, exhibiting excellent stability and reliability of early data. This method can rapidly and stably perform thermal conductivity inversion, making it suitable for rapid detection scenarios such as flexible interfaces and robotic tactile sensing.

[0072] 5. Standard sample verification

[0073] Standard samples with known thermal conductivity were selected, including solid materials with different thermal conductivity such as polymers, glass, ceramics, and metals. The sensor was brought into close contact with each standard sample, with consistent contact force. Temperature response curves were acquired within time windows of 20 ms, 40 ms, 50 ms, and 100 ms after a short pulse start-up. Feature parameters were extracted according to the corresponding time windows and substituted into the inversion model to calculate the thermal conductivity. The inverted thermal conductivity was compared with the nominal thermal conductivity of the standard samples, and the average relative error was calculated. The results are shown below. Figure 6 .

[0074] Depend on Figure 6It can be seen that the first 20 ms of the time window is sufficient to clearly distinguish standard samples with different thermal conductivity. The average relative error between the inverted thermal conductivity and the nominal thermal conductivity is 1.4%, indicating high measurement accuracy. The inversion results within the 20 ms to 100 ms time window show good consistency, indicating that the early time window already contains effective information that can be used for thermal conductivity inversion. This method has been validated on standard samples and can be used for the rapid detection of the thermal conductivity of unknown objects.

[0075] Example 2

[0076] Early transient response under different short-pulse thermal excitation parameters

[0077] The sensor prepared in Example 1 was brought into contact with standard samples of known thermal conductivity. Short-pulse thermal excitation with different parameters was applied sequentially: voltage amplitude: 20 V, 30 V, 40 V; pulse width: 20 ms, 30 ms, 40 ms, 50 ms. Current and voltage signals from the thin-film thermistor measurement unit were simultaneously acquired. Resistance-time curves were calculated from the electrical signals and converted to temperature-time curves according to calibration. The temperature rise amplitude, early response slope, and signal-to-noise ratio under different pulse parameters were recorded, and the response discrimination of samples with different thermal conductivity under each pulse level was compared. The results are shown in […]. Figure 5-6 .

[0078] Depend on Figure 5-6 It is known that for samples with a thermal conductivity <5 W / (m·K), a 20 V, 20 ms pulse is sufficient to produce a resolvable response. For samples with higher thermal conductivity, increasing the pulse amplitude or pulse width is beneficial to further improve the response signal-to-noise ratio. Graded adaptive pulses can cover the entire thermal conductivity range, ensuring measurement discrimination and stability. When thermal conductivity is low, heat dissipation is difficult, so low-voltage, short pulses can produce different responses. However, for objects with high thermal conductivity, heat dissipation is rapid, requiring high-voltage, long pulses to make the sensor response show significant differences. This method is not limited to a single pulse and can automatically match the optimal excitation parameters according to the sample.

[0079] Example 3

[0080] The influence of early time window length on thermal conductivity inversion results

[0081] A standard sample with known thermal conductivity was selected. The sensor was stably placed in contact with the sample, and the contact force was controlled at 5 N. A short pulse thermal excitation with fixed parameters of 20 V and 20 ms was applied. Temperature response curves were captured within time windows of 5 ms, 10 ms, 20 ms, 50 ms, and 100 ms after the pulse start. The temperature rise, initial temperature rise slope, temperature rise integral, and normalized curve shape features at fixed time points were extracted. Inversion models were established using the features of each time window, and the thermal conductivity was calculated. The results were compared with the nominal thermal conductivity of the standard sample, and the average relative error was calculated. The results are shown in […]. Figure 6 .

[0082] Depend on Figure 6 It can be seen that the first 20 ms time window is sufficient to effectively distinguish samples with different thermal conductivity. The inversion error in the first 50 ms and 100 ms time windows is less than 1.5%, and the accuracy is stable. The early transient response already contains sufficient thermal conductivity information, and there is no need for long-term thermal diffusion. The choice of time window has little impact on the final inversion result, and the measurement is robust.

[0083] Example 4

[0084] The impact of contact condition control on the consistency of thermal conductivity measurements

[0085] The sensor prepared in Example 1 was brought into contact with the same standard sample, and the same short-pulse thermal excitation was applied under different normal contact force conditions to collect the early transient thermal response of the thin-film thermistor measurement unit. The contact force changes the actual contact area and contact thermal resistance of the interface, causing deviations in the temperature time-series response curves under different pressures, ultimately affecting the thermal conductivity inversion results.

[0086] This application can control the contact state in two ways: first, by using an external force control platform to stabilize the contact force measured each time within a preset range; second, by integrating a pressure detection unit in the thin-film thermistor measurement unit area, with the corresponding structure as shown in the figure. Figure 7 As shown, a PI flexible support layer 10 serves as a common substrate. A platinum sputtered layer 8 and a thermistor electrode 7 are sequentially arranged on the upper side of the substrate to form an integrated thin-film thermistor measurement unit. An external paraffin protective layer 9 serves as an insulating and thermally conductive interface in contact with the object being measured. A pressure-sensitive layer electrode 11 and a Velostat pressure-sensitive layer 12 form a pressure sensing module on the lower side of the substrate. The module is further protected by a PDMS 13 buffer. Electrically, the thermistor electrode 7 has an independent lead connected to the excitation and acquisition module to achieve initial temperature reading and graded pulse excitation and thermal response signal acquisition. The pressure-sensitive layer electrode 11 has a separate pressure detection line that synchronously transmits contact pressure data to the back-end data processing module. The heat conduction path is that the heat generated by the platinum sputtered layer 8 diffuses bidirectionally to the object being measured and the PI substrate via the paraffin protective layer 9. The back pressure sensing unit only monitors the interface pressing state and does not interfere with millisecond-level early transient heat transfer. The pressure data can be used as a compensation parameter in thermal conductivity inversion calculations, achieving integrated thermal conductivity detection and real-time contact pressure compensation. This pressure detection unit can monitor the contact status in real time. It will only start pulse excitation and signal acquisition when the contact pressure meets the standard. It can also use the measured contact pressure as a compensation parameter to import into the thermal conductivity inversion model to correct the measurement results.

[0087] Example 5

[0088] Sensor flexibility and reusability

[0089] The sensor from Example 1 was fixed on a bending test platform, and the bending conditions were set as follows: radius of curvature ≤ 5 mm, and repeated bending 1000 times. During the bending process, the room temperature resistance of the thin-film thermistor measurement unit was measured periodically. After bending, short-pulse thermal conductivity measurements were repeated using a standard sample. The impedance change rate, response amplitude change rate, and relative change rate of thermal conductivity inversion were calculated. The encapsulation layer, electrodes, and leads were checked for cracks, detachment, or poor contact. Results are shown below. Figure 8 .

[0090] Depend on Figure 8 It is known that the sensor can withstand repeated bending with a curvature radius ≤5 mm, exhibiting excellent flexibility. After 1000 bending cycles, the impedance change rate of the platinum sensing area is <3%, and the relative change rate of the thermal response amplitude and the inversion result is <5%, demonstrating stable performance. There are no issues such as encapsulation cracking, electrode detachment, or lead wire defects, and the reliability meets the requirements for use in flexible scenarios.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A rapid contact-based measurement method for the thermal conductivity of an object based on early transient thermal response, characterized in that, Includes the following steps: 1) A thin-film thermistor measurement unit with a pre-calibrated resistance-temperature relationship is used to form a thermal conduction interface with the object being measured, and the initial temperature of the contact interface is obtained under low self-heating readout conditions. 2) Apply a short pulse thermal excitation to the same thin-film thermistor measurement unit, and collect current and voltage signals in the early time window after the pulse starts to obtain the resistance-time and temperature-time responses; 3) The thermal conductivity of the object under test is calculated by combining the early transient thermal response characteristics, the initial temperature of the contact interface, and the thermal parameters of the substrate and the encapsulation layer; wherein the early time window does not exceed 100 ms, and the measurement process does not require waiting for second-level thermal diffusion or thermal equilibrium.

2. The contact-based rapid measurement method for thermal conductivity of an object based on early transient thermal response as described in claim 1, characterized in that: The low self-heating readout condition is that the Joule heating generated by the applied readout voltage, current, or short pulse causes the temperature rise of the thin-film thermistor measurement unit to be less than 0.1 ℃, and the collected initial resistance only reflects the initial temperature of the contact interface.

3. The contact-based rapid measurement method for thermal conductivity of an object based on early transient thermal response as described in claim 1, characterized in that: The short-pulse thermal excitation is a voltage pulse, current pulse, or power pulse, and a graded adaptive excitation method is adopted: first, a low-energy probe pulse is applied, and when the response amplitude is lower than a preset threshold, the pulse amplitude or width is gradually increased to adapt to the test objects with different thermal conductivity.

4. The contact-based rapid measurement method for thermal conductivity of an object based on early transient thermal response as described in claim 1, characterized in that: The early transient thermal response characteristics include one or more combinations of temperature rise at a fixed time point, initial temperature rise slope, early temperature rise integral, peak temperature rise, peak arrival time, and cooling slope.

5. The contact-based rapid measurement method for thermal conductivity of an object based on early transient thermal response according to claim 1, characterized in that: By limiting the contact state through contact pressure detection, force control execution, or contact displacement control, and using contact pressure as a compensation variable input into the thermal conductivity inversion model, measurement consistency is improved.

6. A contact-based rapid measurement sensor for the thermal conductivity of an object based on early transient thermal response, characterized in that, It includes a flexible support layer, a thin-film thermistor measurement unit, a conductive lead-out area, and an insulating encapsulation layer; the thin-film thermistor measurement unit is a continuous conductive area, which has both low self-heating temperature readout and short-pulse transient self-heating functions; the conductive lead-out area is a low-resistance conductive structure, which is used to reduce the contact resistance of the lead wires; the insulating encapsulation layer covers the surface of the measurement unit and the conductive lead-out area.

7. The sensor according to claim 6, characterized in that: The flexible support layer is selected from one of polyimide, polyethylene terephthalate, polyethylene naphthalate, polydimethylsiloxane, polyurethane, silicone rubber, thin glass, ultrathin silicon wafer, or flexible composite film.

8. The sensor according to claim 6, characterized in that: The insulating encapsulation layer is selected from one or more of PDMS, phenelzine, polyimide, polyurethane, and epoxy resin.

9. The sensor according to claim 6, characterized in that: The material of the thin-film thermistor measurement unit is one of platinum, gold, nickel, chromium, titanium, indium tin oxide, metal oxide, carbon-based material, metal nanowire, or conductive polymer.

10. A contact-type rapid measurement system for the thermal conductivity of an object being measured, characterized in that, The sensor, including any one of claims 6 to 9, further includes an excitation acquisition module and a data processing module; the excitation acquisition module is used to output graded short-pulse thermal excitation and acquire early electrical signals; the data processing module is used for resistance-temperature conversion, transient feature extraction and thermal conductivity inversion.

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