A high selectivity gas sensitive coating composition for humanoid robot electronic nose chip

Abstract

The present application relates to the technical field of coating compositions, and discloses a high-selectivity gas-sensitive coating composition for an electronic nose chip of a humanoid robot, which comprises 40-60 parts of a film-forming base selected from polyvinylidene fluoride or fluorovinyl-vinyl ether alternating copolymer; 15-25 parts of a gas-sensitive filler selected from metal organic framework ZIF-8; 2-5 parts of a conductive agent selected from unmodified multi-walled carbon nanotubes; 1-3 parts of a compatibility regulator selected from perfluorooctyl triethoxysilane; and a binary solvent system composed of a good solvent for dissolving the film-forming base and a non-solvent for dispersing the gas-sensitive filler but not dissolving the film-forming base. The present application utilizes the difference in volatilization rate of the good solvent and the non-solvent and the difference in surface energy between components to induce phase separation, so that the conductive agent is directionally distributed at the phase interface between the gas-sensitive filler and the film-forming base, a heterogeneous conductive network coated with a hydrophobic matrix is constructed, the mechanical strength of the coating is maintained, the exponential resistance response to trace gases is realized, and the interference of high-humidity environment is eliminated.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-selectivity gas-sensitive coating composition for an electronic nose chip of a humanoid robot, belonging to the technical field of coating compositions. BACKGROUND

[0002] In the current field of intelligent sensing technology, an electronic nose chip utilizes a gas-sensitive coating attached to the surface of an electrode to identify and monitor the environmental atmosphere. Such a coating is typically composed of a film-forming resin matrix, a conductive agent, and a high-specific-surface-area gas-sensitive filler. The film-forming resin is used to fix the functional filler to the surface of the electrode, providing mechanical support and meeting the long-term operation requirements of humanoid robots in complex dynamic environments. The industry generally uses fluorocarbon resin, which has excellent chemical stability and strong weather resistance, as the main binder of the coating, and introduces carbon nanomaterials and metal-organic framework functional components through physical blending processes to construct a composite coating system that combines mechanical strength and gas-sensitive response. The coating is applied to humanoid robots in household service or industrial inspection scenarios, which face complex physical and chemical challenges. The environmental humidity fluctuates dramatically in the working space, and the robot's movement applies continuous mechanical stress. Under these conditions, the existing technology exposes defects in the traditional coating preparation process. Conventional processes pursue mechanical uniformity and appearance quality of the coating. Through high-shear dispersion or a strong polar solvent system, the filler is uniformly dispersed at the molecular level in the resin matrix. Excessive pursuit of thermodynamic stability leads to complete coverage of the conductive agent and gas-sensitive particles by the flexible polymer resin chain segments. A dense insulating shielding layer is formed at the microscopic interface, which cuts off the electron transfer contact between the gas-sensitive material and the conductive path, blocks the weak energy level change modulation of the conductive network resistance after the gas-sensitive material adsorbs gas, and causes a significant decrease in sensor sensitivity.

[0003] The prior art is more focused on using automated mechanical devices to improve the overall uniformity of coating application and production efficiency to solve the problem of coating quality consistency. For example, a Chinese invention patent with publication number CN115213036A discloses a coating device for robot chip manufacturing. This scheme integrates liquid storage bins, precision pumping components, and multi-nozzle linkage structures, and cooperates with heating and transmission mechanisms to solve the problems of manual dependence and physical damage in the chip coating process, and establishes an automated coating process. However, this technical route essentially stays at the physical coverage level, and simply relying on external mechanical force or conventional heating methods can ensure the overall surface flatness and thickness uniformity of the coating, but cannot intervene in the microscopic dynamics of the wet film to dry film transformation process of the internal components of the coating. When dealing with high-viscosity fluorocarbon resin systems commonly used in this field, conventional homogeneous spraying and forced drying processes can easily lead to the resin matrix wrapping the conductive agent and gas-sensitive filler without distinction due to the flexible chain segments, forming a dense insulating shielding layer that cuts off the electron transition contact between the gas-sensitive material and the conductive path, resulting in a significant decrease in sensor sensitivity. To compensate for the loss of sensitivity, the industry has tried to increase the load of conductive agents or gas-sensitive fillers to build a forced conduction network, or to use surface hydrophobic modification to shield humidity interference. However, such linear improvement methods do not solve the fundamental contradiction: high filler content leads to a decrease in the cohesive force of the coating and a deterioration of the interfacial bonding force, resulting in microcracks or even peeling under the high-frequency vibration of the robot; simple surface hydrophobic covering easily blocks the micropore channels of the gas-sensitive material, leading to delayed or ineffective response to target gases.

[0004] Therefore, how to break through the limitations of traditional blended coatings in homogeneous structure without sacrificing the mechanical strength of the coating, and through the microstructure regulation of the coating drying film formation process, to build a heterogeneous composite coating system that not only shields environmental humidity interference but also maintains efficient electron communication at the gas-sensitive interface, has become a technical problem to be solved by the present invention. SUMMARY

[0005] To solve the problems raised in the background art, the technical solution of the present invention is as follows: a high-selectivity gas-sensitive coating composition for a humanoid robot electronic nose chip, the composition comprising the following components by weight:

[0006] Film-forming matrix: 40 to 60 parts, selected from polyvinylidene fluoride or fluorovinyl-ethylene-vinyl ether alternating copolymer;

[0007] Gas-sensitive filler: 15 to 25 parts, selected from metal-organic framework ZIF-8;

[0008] Conductive agent: 2 to 5 parts, selected from unmodified multi-walled carbon nanotubes;

[0009] Compatibility modifier: 1 to 3 parts, selected from perfluorooctyltriethoxysilane;

[0010] and a binary solvent system; wherein the binary solvent system is composed of a first solvent and a second solvent, the first solvent is a good solvent for the film-forming matrix, the second solvent is a non-solvent that can disperse the gas-sensitive filler but does not dissolve the film-forming matrix, and the boiling point of the second solvent is lower than that of the first solvent; the mass ratio of the gas-sensitive filler to the conductive agent is 4:1 to 8:1; during the curing process of the composition, phase separation occurs based on the difference in volatilization rates of the first solvent and the second solvent and the difference in surface energy between the components, so that the conductive agent is distributed at the phase interface of the gas-sensitive filler and the film-forming matrix, forming a heterogeneous conductive network covered by the film-forming matrix.

[0011] Preferably, the first solvent is N-methyl pyrrolidone, with a boiling point of 202-204°C; the second solvent is butyl acetate, with a boiling point of 125-127°C; the solubility of the film-forming matrix in the second solvent is less than 0.1 g / 100 g; the second solvent is preferentially volatilized over the first solvent, inducing the conductive agent to aggregate on the surface of the gas-sensitive filler before the film-forming matrix solidifies.

[0012] Preferably, the particle size distribution D50 of the gas-sensitive filler is 150-250 nm, and the specific surface area is greater than 1200 m2 / g; the surface of the gas-sensitive filler is treated with a compatibility modifier, and the conductive agent is attached to the surface of the gas-sensitive filler through the compatibility modifier, forming a composite agglomerate of the gas-sensitive filler and the conductive agent.

[0013] Preferably, the melt index of the film-forming matrix is 2.0-5.0 g / 10 min at 230°C under a load of 5 kg; after the composition is cured, the film-forming matrix forms a continuous phase, filling and isolating the conductive nodes composed of the gas-sensitive filler and the conductive agent in the pore structure of the continuous phase, and using the hydrophobic properties of the film-forming matrix to block the penetration of water molecules.

[0014] Preferably, the conductive agent is a multi-walled carbon nanotube with an aspect ratio greater than 1000; the difference in solubility parameters between the surface of the multi-walled carbon nanotube and the film-forming matrix, and the concentration change during the volatilization of the binary solvent system, drive the multi-walled carbon nanotube to precipitate from the film-forming matrix phase and adsorb on the surface of the gas-sensitive filler.

[0015] Preferably, the amount of the compatibility modifier is such that the surface of the gas-sensitive filler has a fluorine element atomic percentage concentration of 5-10%; this surface fluorination treatment is used to improve the repellency of the gas-sensitive filler to water molecules, while retaining the adsorption channel for volatile organic compounds or hydrogen.

[0016] Preferably, the elongation at break of the coating after the composition is cured is not less than 150%, and after 1000 bending tests at a radius of curvature of 5 mm, the resistance change rate of the coating is less than 5%; a chemical bonding effect exists between the film-forming matrix and the compatibility modifier, to enhance the interfacial bonding strength of the coating.

[0017] Preferably, the second solvent has a mass percentage of 25% to 35% in the binary solvent system; the ratio is used to pre-disperse and contact the conductive agent and the gas-sensitive filler in the second solvent-rich area during the preparation process, preventing the conductive agent from being completely isolated by the film-forming matrix during the mixing process.

[0018] Preferably, the coating composition is used for detecting volatile organic compounds or hydrogen; when the gas-sensitive filler adsorbs gas molecules to produce volume expansion or dielectric constant change, the contact resistance between the conductive agent distributed at the phase interface changes nonlinearly; the hydrophobic structure of the film-forming matrix is used to shield the environmental water vapor in the relative humidity range of 30% to 90%.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] 1. In the electronic nose chip of the humanoid robot, the boiling point difference and the volatilization rate gradient of the good solvent and the latent non-solvent are used to introduce controlled micro-phase separation in the dynamic process of the wet film to dry film transition of the coating, and the dispersed conductive bridging agent is depleted and flocculated under the driving of the surface energy level difference, and is precipitated from the film-forming matrix and is directionally enriched on the grain boundary surface of the gas-sensitive filler. This process induces a heterogeneous self-assembly structure to avoid the unordered wrapping and isolation of the conductive filler by the high molecular resin chain segment in traditional physical blending, establishes a direct electron transition channel between the conductive network and the gas-sensitive interface, and realizes an exponential electrical signal response of the coating to the trace gas adsorption behavior without increasing the amount of conductive agent under the premise that the gas-sensitive filler adsorbs the target gas to produce a small crystal lattice deformation or dielectric constant disturbance.

[0021] 2. Relying on the micro-inlaid structure induced by phase separation, the continuous and dense honeycomb-like skeleton formed by the cured fluorocarbon resin matrix with extremely low surface energy physically encapsulates the conductive nodes with high hygroscopicity and the gas-sensitive interface inside the micropore cavities. The liquid water or water molecule clusters in the environment cannot wet and penetrate the dense hydrophobic continuous phase interface due to the size effect and surface tension limitation. The target small molecule gas freely penetrates to the internal conductive junction through the intrinsic micropore channel of the gas-sensitive filler according to the gas diffusion principle. This structure uses the difference in intrinsic wettability and steric hindrance effect to physically construct a barrier to water molecules and a permeation channel for target gas, realizes the decoupling of the gas-sensitive response and the humidity-sensitive response mechanism, and eliminates the non-specific adsorption of water molecules leading to sensor baseline drift under complex humidity conditions.

[0022] 3. By limiting the specific mass ratio range of gas-sensitive filler and conductive bridging agent, and with the help of compatibility modifier, chemical bonding is established between heterogeneous interfaces. This results in the formation of a subpercolation interpenetrating network within the coating, which is located in the electron tunneling-dominant region. The specific ratio maintains the non-contact, close-proximity distribution of the conductive bridging agent among the gas-sensitive filler particles, avoiding short-circuit dead zones caused by excessive accumulation and preventing open-circuit failure due to excessive spacing. The fluorosilane coupling agent provides chemical anchoring force to enhance the interfacial bonding strength between the inorganic filler and the organic matrix. This allows the cured coating to transmit and dissipate high-frequency mechanical vibrations and thermal expansion and contraction stresses generated during the humanoid robot's movement, preventing signal-to-noise ratio attenuation caused by micro-interface peeling or microcrack propagation during long-term service. Attached Figure Description

[0023] Fig. 1 This is a schematic diagram of the process flow for the directional assembly of the gradient evaporation-induced heterogeneous conductive network of the present invention.

[0024] Fig. 2 This is a comparison chart of the coating resistance response stability and fatigue resistance performance under dynamic bending cycles of the present invention;

[0025] Fig. 3 This is a diagram showing the relationship between the technical elements and the enhancement mechanism of the highly selective gas-sensitive coating composition of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot. The composition comprises a film-forming matrix, a gas-sensitive filler, a conductive bridging agent, a compatibility modifier, and a binary solvent system. After curing, the composition induces a heterogeneous embedded structure through a specific process, where a hydrophobic insulating matrix encapsulates a conductive percolation network. This structure utilizes the continuous phase of fluorocarbon resin to provide mechanical support and moisture shielding, and the conductive bridging agent enriched at the gas-sensitive filler interface to construct an electron tunneling pathway sensitive to gas volume changes, thereby achieving physical separation of gas-sensitive and moisture-sensitive responses. To ensure the reproducibility of the technical solution, the specifications of the raw materials required for preparing the highly selective gas-sensitive coating composition are defined precisely. Regarding the film-forming matrix, fluorocarbon resin is selected as the continuous phase framework for the coating, specifically polyvinylidene fluoride (PVDF). To ensure that the coating possesses mechanical toughness and impact resistance suitable for the humanoid robot's motion conditions after curing, the selected PVDF should have a high molecular weight, with a melt index of 230 according to ASTM D1238 standard. and 5kg load conditions, need to be controlled in 2.0g / 10min to 5.0g / 10min, this melt index range establishes the rheological properties of the matrix resin in the solvent, ensures that it can form a dense physical entanglement network in the film forming process, prevents the relaxation of the conductive network due to the swelling of the matrix in a high humidity environment.

[0028] Regarding the gas-sensitive filler, metal-organic framework material ZIF-8 nanoparticles are selected, ZIF-8 has an intrinsic microporous structure, and the pore size is about 3.4 angstroms, which allows hydrogen, carbon monoxide and small molecule gas alkanes to quickly penetrate, while generating steric hindrance effect to large size water molecule clusters, in order to optimize the packing density of the particles in the coating and provide sufficient gas adsorption sites, the average particle size D50 of ZIF-8 needs to be controlled between 150nm and 250nm, and its specific surface area needs to be greater than 1200m2 / g according to the BET method; regarding the conductive bridging agent, multi-walled carbon nanotubes, i.e. MWCNTs, which are not subjected to carboxylation or hydroxylation surface treatment, are selected, the intrinsic hydrophobicity and chemical inertness of the surface of the carbon nanotubes are maintained, aiming to utilize the difference in surface energy between the carbon nanotubes and the polar matrix resin as the kinetic driving force for subsequent induced phase separation, the tube diameter of the multi-walled carbon nanotubes is 10nm to 20nm, the length is 10μm to 30μm, and the carbon purity is greater than 98%, the selection of this aspect ratio is based on the percolation theory of electrical conduction, to ensure that an effective electron tunneling path can be established between the gas-sensitive filler particles at a lower filling amount; regarding the compatibility regulator, a fluorine-containing silane coupling agent is selected, specifically 1H,1H,2H,2H-perfluorooctyltriethoxysilane, the role of this additive is to adjust the interfacial tension between the inorganic filler and the organic matrix, and induce the directional migration of the conductive agent at the microscale; regarding the solvent system, a binary solvent system composed of a first solvent and a second solvent is constructed, the first solvent is N-methyl pyrrolidone, i.e. NMP, with a standard boiling point of 202 to 204 , as a good solvent for PVDF, used to construct the continuous phase substrate of the coating, the second solvent is selected as butyl acetate, with a standard boiling point of 126 ±1 , butyl acetate is a non-solvent for PVDF resin, and the solubility of PVDF in it is less than 0.1g / 100g at 25 , butyl acetate has good wetting and dispersing ability for ZIF-8 and MWCNTs treated with fluorosilane, and the boiling point difference and solubility difference of the two are the key process basis for realizing the self-assembly of the coating microstructure.

[0029] For the above components, the application formulates a standardized preparation procedure based on latent non-solvent gradient volatilization induced interfacial assembly, which comprises the following time sequence steps: Step one is the pre-assembly of heterogeneous filler clusters. Based on the conventional physical blending process, the conductive agent is easily wrapped by excess insulating resin, resulting in a gas-sensitive dead zone. This step is set to construct a conductive network prototype in an environment without a film-forming matrix. The weighed gas-sensitive filler ZIF-8, conductive bridging agent MWCNTs, and compatibility regulator are put into a dispersion tank containing the second solvent butyl acetate. The ultrasonic dispersion device is turned on, the working frequency is set to 40 kHz, the power density is set to 100 watts per liter, and the system temperature is maintained at 25 ±2 for 30 minutes. During this process, since butyl acetate does not dissolve PVDF and PVDF is added later, the hydrolysis and condensation reaction of fluorosilane preferentially occurs between the metal sites on the surface of ZIF-8 particles and the defect sites of the tube wall of MWCNTs. This pretreatment in a low-viscosity non-solvent environment tightly anchors MWCNTs on the surface of ZIF-8 particles through the dual action of physical winding and chemical bonding, forming ZIF-CNT-silane core-shell structure microcapsules; Step two is the modulation of metastable glue liquid. The weighed film-forming matrix PVDF is completely dissolved in the first solvent NMP to prepare a uniform matrix glue liquid with a solid content of 10% to 15%. The stirring speed is set to 800 rpm to 1200 rpm in low shear mode. The suspension prepared in step one is slowly added to the PVDF matrix glue liquid, and the mixing time is controlled to 20 minutes to 30 minutes. At this time, a solvent gradient is formed in the system: the pre-assembled filler clusters are still mainly wrapped by the butyl acetate solvent shell and dispersed in the NMP-rich PVDF continuous phase in the form of a suspension phase.

[0030] Step three is gradient volatilization induced directional phase separation film forming. The above metastable coating composition is coated on the electrode substrate by spin coating or spraying, and placed in a blast oven for curing. The curing temperature is set to 80 to 90 Within this temperature interval, the vapor pressure of the second solvent butyl acetate is higher than the first solvent NMP, resulting in butyl acetate preferentially volatilizing from the wet film surface, as the butyl acetate solvent shell dissipates, the ZIF-CNT filler clusters originally wrapped by it are exposed to the surrounding incompatible PVDF-NMP phase, based on the depletion flocculation principle in polymer physics, to reduce the total Gibbs free energy of the system, the desolvated filler clusters are forced to undergo secondary densification aggregation at the microscale, further extruding and locking the conductive MWCNTs into the intergranular gap between adjacent ZIF-8 particles, as the high-boiling-point solvent NMP slowly volatilizes, the PVDF molecular chains crystallize and solidify outside the filler clusters, finally physically encapsulating this grape cluster-shaped high- connectivity conductive network inside the dense hydrophobic resin skeleton; The mass ratio of the gas-sensitive filler and the conductive bridging agent is limited to the interval of 4:1 to 8:1. This ratio is not arbitrarily chosen, but is the result of engineering optimization based on percolation theory and electron tunneling mechanism. When the mass ratio is less than 4:1, excessive MWCNTs will form rigid conductive paths that directly overlap inside the coating. At this time, even if the ZIF-8 adsorbs gas and expands in volume, it cannot effectively cut off or stretch these rigid paths, resulting in a very low change rate of the coating resistance, i.e. insufficient sensitivity. When the mass ratio is higher than 8:1, sparse MWCNTs cannot build a continuous tunneling network between ZIF-8 particles, and the coating is in an insulating state, i.e. a short circuit occurs. Only within the specific window of 4:1 to 8:1, MWCNTs are in a sub-percolation state, and their conductivity mainly depends on electron tunneling transitions between the surfaces of ZIF-8 particles. At this time, a small lattice deformation or dielectric constant change of ZIF-8 will cause an exponential change in the tunneling barrier, thereby enhancing the high sensitivity response of the coating to trace gases.

[0031] To fully verify the environmental adaptability of the coating in a wide humidity range, a dynamic humidity gradient environment with a relative humidity linearly increasing from 30% to 90% is constructed in a standard test chamber. During the test, the temperature in the chamber is kept at 25 Constant, and the response curve of the coating resistance with humidity is recorded. Experimental data show that during the whole process of gradually increasing the relative humidity from 30% to 90%, the change rate of the baseline resistance of the coating always remains within a small fluctuation range of ±5%, and the exponential resistance drop commonly seen in traditional hydrophilic coatings does not occur. This result shows that the continuous hydrophobic network constructed by high-crystallinity PVDF matrix effectively truncates the capillary condensation path of water molecules inside the coating at the microscale. Even in a high-humidity environment, water molecules can only exist in an adsorbed state on the outermost surface layer of the coating and cannot penetrate to the internal ZIF-CNT conductive skeleton region, thereby achieving effective shielding of environmental water vapor interference in a wide range of 30% to 90% in a physical mechanism.

[0032] and a standardized incoming physical and chemical index calibration procedure is introduced for the gas-sensitive filler and the conductive agent, and the degree of graphitization of the unmodified multi-walled carbon nanotube conductive agent is characterized by Raman spectroscopy, and the intensity ratio of D peak to G peak is controlled less than 0.15, and the surface oxygen atom percentage content is less than 1.0% confirmed by X-ray photoelectron spectroscopy analysis, and the unmodified surface chemical inertness and hydrophobic characteristics are defined by quantitative indicators to ensure that the spontaneous repulsion behavior in the good solvent phase meets the thermodynamic expectation, and the ZIF-8 gas-sensitive filler is vacuum heat-activated before dispersion, and the relative pressure is 0.05, and the adsorption amount is greater than 300 standard cubic centimeters per gram to determine that the micropore channel is in an open state, and the filler is ultrasonically dispersed in a binary solvent system to ensure that the specific surface area active site of the filler is at a normalized level before liquid assembly; a solidification end point determination mechanism based on the differential curve of the solvent evaporation rate is established, and after the wet film of the coating enters the oven, the online micro-thermogravimetric sensor is used to monitor the mass loss rate of the wet film in real time, and the peak rate of the second solvent butyl acetate is defined as , the peak rate of the first solvent N-methyl pyrrolidone is , and the process control logic is set to maintain the current temperature constant for 10 minutes when the real-time mass loss rate falls from to and does not enter the main evaporation zone, giving the conductive agent a sufficient distribution and rearrangement time at the phase interface, and the temperature is increased to 10°C below the boiling point of the first solvent, and the matrix is solidified until the total volatile organic compound residue is less than 500 ppm, and based on the volatile kinetics characteristics rather than the simple time-temperature closed loop control logic, the environmental humidity or air flow disturbance caused by the solvent evaporation deviation is automatically compensated.

[0033] Example 1: In the application scenario of a humanoid robot involving inspection of petroleum chemical facilities, the electronic nose chip needs to be directly exposed to complex working conditions accompanied by intermittent high-temperature steam leakage and high-frequency mechanical vibration of large compressor units, which requires the gas-sensitive coating to maintain stable detection capability for alkanes dangerous gas under severe humidity fluctuations and continuous shear stress. To address this application challenge, the preparation procedure determined in the foregoing specific embodiments is used, and the second solvent butyl acetate and the first solvent N-methyl pyrrolidone in the binary solvent system are used and 202 The difference in boiling points, the introduction of controlled thermodynamic instability in the solidification stage after the coating is applied to the electrode surface by spin coating, the dynamic shift of the polarity of the solvent environment in the system as the low-boiling latent non-solvent butyl acetate preferentially gradient volatilizes, the microscale depletion flocculation of ZIF-CNT heterogeneous filler clusters modified by a compatibility regulator, perfluorooctyltriethoxysilane, inside the wet film, the directional precipitation of the conductive bridging agent, multi-walled carbon nanotubes, from the good solvent phase rich in polyvinylidene fluoride and the close locking in the grain boundary gap of the gas-sensitive filler ZIF-8, and finally the construction of a grape cluster-shaped electronic tunneling network physically wrapped by a dense hydrophobic continuous phase before the polyvinylidene fluoride matrix is completely crystallized and solidified, this heterogeneous inlaid structure uses the high crystallinity and low surface energy characteristics of the polyvinylidene fluoride matrix to construct a physical shielding layer for environmental water molecule clusters, uses the 3.4 angstrom intrinsic microporous channel of the ZIF-8 material as a diffusion path for target alkane gas molecules, and dissipates external mechanical vibration energy through the chemical bonding effect between the heterogeneous interfaces, thereby eliminating the coupling interference between the humidity-sensitive response and the gas-sensitive response as a whole. The measured data shows that under the steam shock condition that the relative humidity instantaneously jumps from 40% to 90%, the baseline drift rate of the coating output resistance is controlled within 5%, and under the mechanical vibration environment with a superimposed frequency of 50 Hz, the response sensitivity to 10 ppm isobutane gas does not decay.

[0034] Example 2: To systematically verify the comprehensive performance of the high-selectivity gas-sensitive coating composition of the application and the influence law of key process parameters on the final technical effect, this example constructs a standardized test process containing multiple-dimension control groups. This test aims to objectively evaluate the gas-sensitive response characteristics, anti-wet interference ability and effectiveness of the microstructure of the coating in the simulated real application scenario. The test platform uses a customized gas-sensitive element dynamic test system composed of a precision mass flow controller gas supply unit, a sealed test chamber equipped with heating and temperature and humidity control functions, and a data acquisition terminal equipped with a source measurement unit (SMU, Keithley 2400). All gas-sensitive data are obtained at a standard room temperature of 25 ±1 , by alternately introducing the target detection gas and the background air into the test chamber, and recording the change curve of the coating resistance over time. The gas-sensitive sensitivity S of the coating is defined as the ratio of the steady-state resistance value Rg after the target gas is introduced to the steady-state resistance value Ra when the background air is introduced, that is, S = Rg / Ra, and the inverse for reducing gas.

[0035] The test design of the present embodiment includes two groups of core control systems. The first group is a synergistic effect verification control group, which aims to demonstrate the non-obviousness of the technical solution of the present application through feature deletion experiments. Specifically, control group A (deletion of compatibility regulator): the preparation process is exactly the same as that of Example 1, but 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane is removed from the formula to investigate the contribution of interfacial chemical anchoring to the microstructure and stability. Control group B (deletion of gradient solvent process): the formula is exactly the same as that of Example 1, but the solvent system only uses a single solvent NMP without adding the second solvent butyl acetate, and is prepared by conventional physical blending to verify the key role of the binary solvent gradient volatilization induced phase separation mechanism. The sample group of the present application: the coating is prepared by using the formula and process of Example 1; the second group is a key parameter boundary verification control group, which aims to confirm the reasonableness of the mass ratio of ZIF-8 to MWCNTs (4:1 to 8:1). Specifically, control group C (lower limit of the range): the mass ratio of ZIF-8 to MWCNTs is set to 2:1 to simulate the state of excessive accumulation of conductive agent, and control group D (upper limit of the range): the mass ratio of ZIF-8 to MWCNTs is set to 12:1 to simulate the sparse state of the conductive network.

[0036] The test is for the first group of control systems to test the gas sensitivity performance. Each group of coatings is placed in a test environment containing 10 ppm isobutane gas, and a humidity disturbance is applied by instantaneously increasing the relative humidity from 40% to 90% during the test. The test results show that: the coating of control group A shows a certain response to isobutane at the initial stage, but after experiencing three humidity cycles, its sensitivity S decays by more than 40%, and the baseline resistance irreversibly drifts. The scanning electron microscopy results show that due to the lack of interfacial coupling of fluorosilane, microcracks occur between ZIF-8 particles and the PVDF matrix, leading to the invasion of water molecules along the interfacial defects. The initial resistance of the coating of control group B is extremely low, and the sensitivity S to 10 ppm isobutane is only 1.2, almost no obvious response. This is because in a single good solvent system, the PVDF molecular chain fully stretches and tightly wraps most of the MWCNTs, forming an insulating shielding layer, cutting off the effective contact between the gas molecules and the conductive channel, and a typical dead zone effect occurs. In contrast, the sensitivity S of the sample group of the present application to 10 ppm isobutane is stably maintained at more than 15.0 under the same conditions, and the baseline resistance fluctuation amplitude is less than 5% under 90% high humidity impact. Micro-morphology characterization confirms that the expected heterogeneous inlaid structure is constructed in this sample group, and MWCNTs are selectively enriched at the ZIF-8 grain boundaries to form a highly sensitive tunneling network to gas volume expansion.

[0037] Table 1: Comparison of key data of synergistic effect verification test

[0038]

[0039] To further confirm the chemical bond effect between the heterogeneous interfaces constructed by the compatibility regulator from the molecular level, the cured coating sample was subjected to X-ray photoelectron spectroscopy (XPS) depth profiling in this embodiment, and the test results showed that, on the side of the C1s main peak with a binding energy of 284.8 electron volts, a new characteristic peak with a binding energy of 286.5 electron volts appeared, which belonged to the binding energy of C-O-Si bond. In the Si2p spectrum, a characteristic peak with a binding energy of 102.3 electron volts was observed, which corresponded to the formation of Si-O-C bond. Through difference spectrum analysis with the control group without adding the compatibility regulator, the relative intensity of the above characteristic peak was enhanced. This microscopic spectroscopic evidence confirmed that the hydrolyzed groups of perfluorooctyltriethoxysilane had undergone chemical condensation reaction with the hydroxyl groups on the surface of ZIF-8 and the active sites on the PVDF molecular chain.

[0040] And the electrical property test was carried out on the second group of control systems, and the test results showed that the initial resistance of control group C was only a few hundred ohms, showing a metal-like conductivity, and when the target gas was introduced, the resistance change rate was less than 1%, which indicated that the excess MWCNTs formed a rigid conductive path directly connected, and the micro deformation of ZIF-8 could not effectively modulate the resistance of the path, which was in the short-circuit region above the percolation threshold. The initial resistance of control group D was as high as hundreds of megohms, close to an insulator, and no effective current signal could be detected under normal voltage, which indicated that the sparse MWCNTs spacing was too large to form a continuous electron tunneling path, and was in the open-circuit region. Only the sample group (mass ratio 5.7:1) of the present application, whose initial resistance was in the semiconductor region of kilo-ohms to mega-ohms, was just in the sub-percolation state. In this region, electron transport mainly depended on the quantum tunneling effect between particles, which was extremely sensitive to spacing changes, thereby achieving exponential response to trace gas adsorption behavior.

[0041] Table 2: Comparison of key data of parameter boundary verification test

[0042]

[0043] In summary, through multi-dimensional control tests, the effectiveness and creativity of the technical solution of the present application are confirmed. The data show that only when the specific binary solvent gradient volatilization process and the specific component ratio (especially the filler ratio of 4:1 to 8:1) are used at the same time, can a structure-activity locked heterogeneous microstructure be constructed inside the coating. Not only does it overcome the sensitivity bottleneck caused by the insulating wrapping of the resin in traditional physical blending, but it also effectively solves the baseline drift problem in high humidity environments, achieving simultaneous improvement of gas sensing performance and anti-interference ability.

[0044] Example 3: This embodiment combines Figs. 1 to 3 to explain a high-selectivity gas-sensitive coating composition for a humanoid robot electronic nose chip, like Fig. 1As shown, 40 to 60 parts of a film-forming matrix selected from polyvinylidene fluoride or alternating copolymers of vinyl fluoride and vinyl ether, 15 to 25 parts of a gas-sensitive filler selected from metal-organic framework ZIF-8, 2 to 5 parts of a conductive agent selected from unmodified multi-walled carbon nanotubes, 1 to 3 parts of a compatibility modifier selected from perfluorooctyltriethoxysilane, and a binary solvent system composed of a good solvent and a non-solvent with a difference in boiling point are selected as raw materials. The above components are prepared into a mixed dispersion and curing precursor to form a thermodynamically metastable wet film. During the curing process, the gradient evaporation induced by the difference in solvent evaporation rate and surface energy is used to drive the directional assembly process to construct a heterogeneous conductive network structure in which the conductive agent is directionally distributed at the interface between the gas-sensitive filler and the matrix. Finally, the functional characteristics of hydrophobic matrix coating to eliminate high humidity interference and exponential resistance response are achieved.

[0045] like Fig. 2 As shown in the graph, this chart illustrates the relationship between the number of bending tests and the percentage change in resistance. The horizontal axis represents 100, 300, 500, 800, and 1000 bending cycles, and the vertical axis represents the percentage change in resistance. The legend distinguishes the coating of this invention from conventional coatings. As the number of bending tests increases, the percentage change in resistance of the conventional coating rises and exceeds 30% at 1000 cycles, while the coating of this invention, after undergoing the same number of bending cycles, maintains a percentage change in resistance below 5%. Fig. 3 As shown, this fishbone diagram focuses on highly selective gas-sensitive coating compositions, breaking them down into four dimensions: core component formulation, microstructure characteristics, key preparation processes, and response enhancement mechanisms. The core component formulation dimension encompasses a PVDF film-forming matrix providing a hydrophobic continuous phase framework, ZIF-8 gas-sensitive fillers with specific particle size and specific surface area, and a binary solvent system containing both a good solvent and a latent non-solvent. The microstructure characteristics dimension showcases a heterogeneous mosaic structure encapsulated by a hydrophobic matrix, a subpercolation conductive network with specific mass ratios of 4:1 to 8:1, and a chemically bonded interface based on the action of a compatibility modifier. The key preparation processes dimension elucidates interfacial self-assembly through the directional enrichment of conductive agents, microphase separation induction under a depletion flocculation mechanism, and gradient volatilization control driven by boiling point differences. The response enhancement mechanism dimension reveals mechanical stress dissipation to adapt to dynamic robot operating conditions, physical shielding of water molecules to address baseline drift in high humidity, and an electron tunneling effect that generates exponential resistance changes.

[0046] Example 4: This embodiment provides a set of integrated targeted repair technology solutions, which establishes a standardized engineering calibration procedure for precisely calibrating the solvent system ratio, and by constructing a microstructure-electrical property correlation model, the physical root of the nonlinear response interval is transparently explained at the mechanism level, thereby forming a closed-loop structure-property self-verification logic chain. First stage: Engineering calibration procedure for binary solvent system ratio is to determine the optimal mass ratio of N-methyl pyrrolidone (NMP) and butyl acetate. The following gradient experiment is designed and performed. Formulation design: keep the amount of PVDF matrix, ZIF-8 filler, MWCNTs conductive agent and fluorosilane coupling agent consistent with Example 1, only change the mass ratio of NMP and butyl acetate in the solvent system, set five gradient groups, the ratio is 90:10, 80:20, 70:30, 60:40 and 50:50 respectively. Dispersion stability test: the prepared slurry is left for 24 hours, and the sedimentation volume ratio is measured. When the butyl acetate content exceeds 40%, i.e. 60:40 and 50:50 groups, due to the decrease of PVDF solubility, the system shows obvious overall layering and flocculation, the sedimentation volume ratio is less than 0.8, which is judged as unqualified. Film microstructure characterization: the remaining three groups (90:10, 80:20, 70:30) slurry is spin-coated into film and solidified, the cross-section of the coating is observed by scanning electron microscope (SEM). 90:10 group: the cross-section shows that the conductive agent is evenly distributed and no obvious enrichment network is formed, indicating that the phase separation driving force is insufficient. 80:20 group: local conductive agent aggregation is observed, but the connectivity is not high, showing island-like distribution. 70:30 group: clear grape string-like ZIF-CNT enrichment phase is presented, which is continuous and penetrates through the thickness direction of the coating, and is tightly wrapped by PVDF matrix. Conclusion determination: based on the dispersion stability and microstructure forming quality, the optimal mass ratio window of NMP and butyl acetate is determined to be 75:25 to 65:35, and the 70:30 used in Example 1 is preferably selected. This procedure establishes the basis for setting the solvent ratio, which is not arbitrary.

[0047] Second stage: Parameterization of the final coating preparation process After determining the optimal solvent ratio, the following standardized final product preparation process is performed: substrate pretreatment: interdigital electrodes are selected as the substrate, which are ultrasonically cleaned with acetone, ethanol and deionized water for 10 minutes respectively, and dried at 80 ℃ for standby; precision spin coating: the spin coating program is started after the metastable coating composition prepared in Example 1 is added to the center of the electrode. The first stage is 500 rpm for 5 seconds to spread the glue liquid. The second stage is 2000 rpm for 30 seconds to control the wet film thickness to be 50±5 microns. Step drying-curing program: phase separation induction stage: the wet film is placed in a 60 In a constant-temperature forced-air drying oven, maintain the temperature for 30 minutes. During this stage, the temperature is below the boiling point of butyl acetate to control its evaporation rate, ensuring sufficient microphase separation and orderly assembly of the conductive network. Substrate curing stage: heat to 120°C. Hold for 60 minutes. This stage aims to rapidly remove NMP solvent and promote the crystallization and densification of the PVDF matrix, locking in the formed microstructure. Post-treatment: naturally cool to room temperature. This process specification clearly defines the key heat treatment parameters in the transition from wet film to dry film, ensuring the reproducibility of the technical solution.

[0048] Phase 3: Mechanism Elucidation and Model Verification of the Nonlinear Response Range. To reveal the underlying mechanism of controlling the ZIF-8 to MWCNTs mass ratio within the range of 4:1 to 8:1, a resistance response model based on percolation theory is constructed. Within this range, the total resistance of the coating... This can be approximated as: in, Where is the contact resistance constant. The coefficient is related to the electron tunneling barrier. The average spacing between adjacent MWCNTs is the lattice expansion caused by the adsorption of target gas molecules by ZIF-8, resulting in an increase in spacing. A small increment occurred Low ratio region (<4:1): At this point, the MWCNT content is high, forming physical contact conductivity. The resistance is mainly determined by Ohm's law and is not related to the spacing. A linear relationship ( ), tiny It only causes a slight linear change in resistance, resulting in extremely low sensitivity; in the high ratio region (>8:1): the MWCNT content is too low, and the spacing... Far exceeding the electron tunneling distance, with an insulating coating; target range (4:1-8:1): at this point, the conductive network is in a subpercolation state dominated by tunneling, with low resistance. Spacing The changes show an exponential dependence, and small changes... This can trigger resistance Dramatic changes ( ).

[0049] Example 5: Addressing the potential risk of insufficient disclosure regarding the coating microstructure assembly process and long-term stability of the gas-sensitive response in the aforementioned examples, this example further discloses a standardized offline calibration and data filling procedure. This procedure sets out calibration steps for the volatilization kinetics of the binary solvent system. Under standard atmospheric pressure, a precision thermogravimetric analyzer (TGA) is used at 60°C. Under isothermal conditions, isothermal weight loss tests were performed on mixed solvents with different NMP / butyl acetate ratios, and the differential signal (DTG) of the weight loss curves was recorded. By analyzing the half-peak width and peak time of the main volatile peak of butyl acetate on the DTG curve, a quantitative relationship library between solvent evaporation rate and ratio was established. Before actual preparation, the heating rate of the oven was fine-tuned according to the measured evaporation characteristics of the solvent in each batch to ensure that the microphase separation process is fully carried out within a controlled time window.

[0050] Secondly, to address the baseline drift issue of the sensor under different temperature and humidity environments, this embodiment constructs a pre-deployment calibration procedure. This procedure does not rely on general environmental compensation algorithms but is based on the physical response characteristics of the coating itself. Upon initial power-on of the sensor or a change in the deployment environment, a self-calibration process is initiated: the system controls the heating electrodes to rapidly heat the coating to 150°C. It is held for 60 seconds to remove water molecules and impurity gases that may be adsorbed on the coating surface and in the pores using the principle of high temperature desorption, so that the sensor resistance is restored to the dry state reference value. The system automatically collects the steady-state resistance value under the current environment and uses it as the new zero-point baseline.

[0051] Example 6: In the manufacturing of optical sensor components for precision vision systems in humanoid robots, it is necessary to ensure that the coating maintains constant photoelectric performance and mechanical adhesion under different substrate surfaces and complex curing conditions. To address the potential risk of process parameter fluctuations during coating curing, this example constructs a standardized process parameter optimization and verification procedure. To determine the optimal curing temperature and time window, an orthogonal experiment is designed with coating crosslinking degree and adhesion as the core indicators. Under the premise of fixed coating components and ratios, an 80°C curing temperature and time window are selected. 100 120 140 Four temperature gradients and three time gradients (30 minutes, 60 minutes, and 90 minutes) were combined for curing. The glass transition temperature of each coating group was determined using differential scanning calorimetry (DSC). This was used to characterize the degree of cross-linking; simultaneously, adhesion was tested using the cross-linking method according to ASTM D3359 standard. Experimental data showed that when the curing temperature was below 100°C... hour, A value lower than the theoretical value indicates incomplete cross-linking reaction; when the temperature is above 120°C... Furthermore, when the time exceeded 60 minutes, the coating showed slight yellowing, indicating that the substrate underwent thermal oxidative degradation. Comprehensive analysis determined that 120... ±5 Furthermore, maintaining a curing time of 60 minutes is considered the optimal curing process parameter that balances crosslinking efficiency and material stability.

[0052] Second, to eliminate the influence of coating thickness fluctuation on the consistency of gas sensitive response, a calibration process of wet film thickness-resistance response correlation was established. A series of coating samples with wet film thickness from 20 microns to 100 microns were prepared on standard electrodes by the blade coating method and cured under the optimal process determined above. The sensitivity response of each sample to 10 ppm standard gas was tested. The results show that when the wet film thickness is less than 30 microns, the resistance dispersion between samples exceeds 15% due to the statistical fluctuation of the conductive network path. When the thickness exceeds 80 microns, the response time (T90) increases due to the lengthening of the gas diffusion path. It is clear that 50±5 microns is the target wet film thickness to balance the consistency of sensor performance and response speed, and the rotation speed and time parameters of the spin coating process are set accordingly.

[0053] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application.

[0054] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application.​

Claims

1. A highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot, characterized in that, The composition consists of the following components in parts by weight: Film-forming matrix: 40 to 60 parts, selected from polyvinylidene fluoride or alternating copolymers of vinyl fluoride and vinyl ether; Gas-sensitive filler: 15 to 25 parts, selected from metal-organic framework ZIF-8; Conductive agent: 2 to 5 parts, selected from unmodified multi-walled carbon nanotubes; Compatibility modifier: 1 to 3 parts, selected from perfluorooctyltriethoxysilane; And a binary solvent system; wherein the binary solvent system consists of a first solvent and a second solvent, the first solvent being a good solvent for dissolving the film-forming matrix, and the second solvent being a non-solvent capable of dispersing the gas-sensitive filler but not dissolving the film-forming matrix, and the boiling point of the second solvent being lower than that of the first solvent; the mass ratio of the gas-sensitive filler to the conductive agent is 4:1 to 8:1; during the curing and film-forming process, phase separation occurs based on the difference in evaporation rates between the first solvent and the second solvent and the difference in surface energy between the components, causing the conductive agent to be distributed at the phase interface between the gas-sensitive filler and the film-forming matrix, forming a heterogeneous conductive network coated by the film-forming matrix; The first solvent is N-methylpyrrolidone, with a boiling point of 202°C to 204°C; the second solvent is butyl acetate, with a boiling point of 125°C to 127°C; the solubility of the film-forming matrix in the second solvent is less than 0.1 g / 100 g; the conductive agent is induced to accumulate on the surface of the gas-sensitive filler before the film-forming matrix is ​​cured by the preferential evaporation of the second solvent over the first solvent. The second solvent has a mass percentage of 25% to 35% in the binary solvent system; this ratio is used to pre-disperse and contact the conductive agent and the gas-sensitive filler in the second solvent enrichment region during the preparation process.

2. The highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot according to claim 1, characterized in that, The particle size distribution D50 of the gas-sensitive filler is 150 nm to 250 nm, and the specific surface area is greater than 1200 m² / g. The surface of the gas-sensitive filler is treated with a compatibility modifier, and the conductive agent is attached to the surface of the gas-sensitive filler through the compatibility modifier, forming a composite agglomerate of gas-sensitive filler and conductive agent.

3. The highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot according to claim 1, characterized in that, The melt index of the film-forming matrix is ​​2.0 g / 10 min to 5.0 g / 10 min at 230 °C and 5 kg load. After the composition is cured, the film-forming matrix forms a continuous phase, filling and isolating the conductive nodes composed of gas-sensitive filler and conductive agent in the pore structure of the continuous phase, and using the hydrophobic properties of the film-forming matrix to block the penetration of water molecules.

4. The highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot according to claim 1, characterized in that, The conductive agent is a multi-walled carbon nanotube with an aspect ratio greater than 1000. By utilizing the difference in solubility parameters between the surface of the multi-walled carbon nanotube and the film-forming matrix, as well as the concentration change during the evaporation process of the binary solvent system, the multi-walled carbon nanotube is driven to precipitate from the film-forming matrix phase and adsorb onto the surface of the gas-sensitive filler.

5. The highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot according to claim 1, characterized in that, The amount of compatibility modifier used makes the atomic percentage concentration of fluorine on the surface of the gas-sensitive packing 5% to 10%; this surface fluorination treatment is used to improve the gas-sensitive packing's ability to repel water molecules, while retaining adsorption channels for volatile organic compounds or hydrogen.

6. The highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot according to claim 1, characterized in that, The elongation at break of the cured coating is not less than 150%, and the change in resistivity of the coating is less than 5% after 1000 bending tests under a radius of curvature of 5 mm. There is a chemical bond between the film-forming matrix and the compatibility modifier.

7. The highly selective gas-sensitive coating composition for an electronic nose chip in a humanoid robot according to claim 1, characterized in that, This coating composition is used to detect volatile organic compounds or hydrogen; when the gas-sensitive filler adsorbs gas molecules and causes volume expansion or changes in dielectric constant, the contact resistance between the conductive agents distributed at the phase interface changes nonlinearly; the hydrophobic structure of the film-forming substrate is used to shield environmental water vapor interference in the relative humidity range of 30% to 90%.

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