Electrochemical type air protein concentration detection device and method based on nano-porous MEMS

Abstract

The invention relates to an electrochemical air protein concentration detection device and method based on a nano-porous MEMS, the device comprises an MEMS sensor main body, a micro air pump assembly and a self-cleaning module, the MEMS sensor main body comprises an MEMS silicon substrate, a nano-porous enrichment layer and an electrochemical electrode array; the electrochemical electrode array consists of a working electrode, a reference electrode and a counter electrode; a Pt temperature sensor and a heating electrode are integrated on the MEMS silicon substrate; the surface of the nano-porous enrichment layer is modified with 3-aminopropyltriethoxysilane, the bottom of the nano-porous enrichment layer is connected with a heating electrode of the MEMS silicon substrate through a silicon through hole, and the top of the nano-porous enrichment layer and a working electrode of the electrochemical electrode array form a conductive path through a silicon through hole; and the nano-porous enrichment layer and the micro air pump assembly realize air path sealing through a PDMS sealing ring. The air protein is pre-enriched through the nano-porous MEMS structure, quantitative detection is achieved through non-enzyme electrochemical oxidation reaction, an electric heating dual-mode self-cleaning system is integrated, and the problems that in the prior art, cost is high, and maintenance is complex are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of air protein concentration detection, and particularly relates to an electrochemical air protein concentration detection device and method based on nanoporous MEMS. Background Art

[0002] Indoor air protein pollution (such as allergens, virus proteins, bioaerosols) poses a potential threat to human health. Real-time detection of its concentration is a key requirement for the intelligentization of environmental appliances. The current mainstream detection technologies have the following bottlenecks:

[0003] 1) Laboratory detection methods

[0004] ELISA method (enzyme-linked immunosorbent assay)

[0005] Quantify proteins through the specific binding reaction of antibody-antigen, and the detection limit can reach 0.01 μg / m 3 , but it relies on expensive biological reagents (the cost of monoclonal antibodies > 50 yuan per time), and the detection cycle is long (> 2 hours), unable to achieve real-time online monitoring, and is only suitable for offline sample analysis.

[0006] Mass spectrometry analysis

[0007] Based on electrospray ionization-mass spectrometry (ESI-MS) technology, it can identify the molecular mass fingerprint of proteins, with extremely high precision, but the device volume is large (> 0.5 m 3 ), the power consumption > 200 W, and it requires professional operation, unable to be integrated into household devices.

[0008] 2) Portable detection technologies

[0009] Optical sensors

[0010] Detect by using the ultraviolet absorption (280 nm) or fluorescence labeling of proteins. Limited by the light scattering efficiency and environmental light interference, the error > 20% under complex lighting conditions (such as indoors with direct sunlight), and the cost of the optical path system > 3000 yuan, making it difficult to popularize.

[0011] Traditional electrochemical sensors

[0012] Catalyze the current signal through the antigen-antibody reaction, and the detection limit is 0.2 μg / m 3 . However, the biological modification layer is easily inactivated by humidity and temperature (service life < 3 months), and the electrodes need to be replaced regularly (consumable cost > 100 yuan per time), unable to meet the long-term maintenance-free requirements of household appliances.

[0013] 3) MEMS micro-nano sensor technology

[0014] Existing MEMS-based sensors attempt to solve the above problems through miniaturization, for example:

[0015] A certain electrostatic adsorption type MEMS sensor utilizes the charged characteristics of proteins for enrichment detection, but can only qualitatively judge the presence or absence of proteins and cannot achieve concentration quantification (error > 50%).

[0016] A certain patent uses a nanowire field effect transistor (FET) to modify antibodies, with a detection limit of 0.1 μg / m 3 , but the biomolecular layer on the surface of the nanowire is easily covered by pollutants, resulting in signal attenuation (drift > 30% per week), and frequent calibration is required.

[0017] In summary, the prior art has the following technical defects:

[0018] Summary of the Invention

[0019] The purpose of the present invention is to provide an electrochemical air protein concentration detection device and method based on nanoporous MEMS. The nanoporous MEMS structure is used to pre-enrich air proteins, and enzyme-free electrochemical oxidation reaction is utilized to achieve quantitative detection. An electrothermal dual-mode self-cleaning system is integrated to solve the problems of high cost and complex maintenance in the prior art.

[0020] The present invention provides an electrochemical air protein concentration detection device based on nanoporous MEMS, including a MEMS sensor main body, a micro air pump assembly and a self-cleaning module. The MEMS sensor main body includes a MEMS silicon substrate, a nanoporous enrichment layer, and an electrochemical electrode array; the electrochemical electrode array consists of a working electrode, a reference electrode, and a counter electrode to form a three-electrode system;

[0021] The MEMS silicon substrate is made of high-purity single crystal silicon, and a microchannel network is formed on its surface by dry etching; the MEMS silicon substrate is integrated with a Pt temperature sensor and a heating electrode; the heating electrode uses a Pt resistance heater; the self-cleaning module shares the Pt resistance heater with the MEMS silicon substrate;

[0022] The nanoporous enrichment layer is prepared by anodizing to form a porous alumina layer on an aluminum foil substrate, and its surface is modified with 3-aminopropyltriethoxysilane; the bottom of the nanoporous enrichment layer is connected to the heating electrode of the MEMS silicon substrate through a silicon through-hole, and the top is connected to the working electrode of the electrochemical electrode array through a silicon through-hole to form a conductive path; the nanoporous enrichment layer and the micro air pump assembly are hermetically sealed through a PDMS sealing ring to ensure that the air flow only passes through the pores of the nanoporous enrichment layer.

[0023] The working electrode, reference electrode, and counter electrode form an array pattern through a lithography process and are vertically interconnected with the silicon vias of the MEMS silicon substrate; the signal output ends of the working electrode, reference electrode, and counter electrode are wire-bonded to a potentiostat circuit to achieve current-voltage signal conversion;

[0024] The micro air pump assembly includes a micro air pump, and a primary filter is provided at the air inlet of the micro air pump, and the outlet is directly docked with the microchannel of the nanoporous enrichment layer to form a closed-loop gas path.

[0025] Further, a 50-nm-thick silicon dioxide insulating layer is evaporated on the surface of the MEMS silicon substrate to prevent substrate leakage from interfering with electrochemical signals; the edge pins of the MEMS silicon substrate are wire-bonded to an external PCB for transmitting power, control signals, and detection data.

[0026] Further, the nanoporous enrichment layer is arranged at an angle of 45° with respect to the air flow direction to increase the probability of protein collision and adsorption; a diversion groove is provided at the edge of the nanoporous enrichment layer for guiding the air flow to evenly cover the entire porous area.

[0027] Further, the nanoporous enrichment layer has a pore size of 150 - 250 nm and a porosity of ≥70%.

[0028] Further, the working electrode is made by depositing a 300-nm-thick gold layer on the MEMS silicon substrate by electron beam evaporation and forming a porous gold structure with a pore size of 5 nm through electrochemical corrosion; the reference electrode uses an Ag or AgCl wire with a diameter of 0.5 mm, and its surface is coated with potassium chloride gel and isolated from the working electrode through a salt bridge to provide a stable reference potential; the counter electrode uses a platinum wire with a diameter of 0.3 mm and a length of 5 mm, and its surface is electrochemically polished to reduce background current noise.

[0029] Further ID, the micro air pump assembly uses a piezoelectric ceramic micro pump, and a plurality of air flow hole arrays are annularly distributed.

[0030] Further, the power supply and control signals of the micro air pump assembly are connected to the edge pins of the MEMS silicon substrate through a flexible circuit board.

[0031] The present invention also provides an air protein concentration detection method using the device, which is characterized by including the following steps:

[0032] Step 1, system initialization and parameter calibration, including:

[0033] Hardware self-check:

[0034] The micro air pump starts to run idly for 30 seconds, and it is detected whether the flow rate is stable at 0.5 L / min ± 3%;

[0035] The potentiostat circuit checks the baseline current of the three electrodes. If the dark current is greater than 10nA, the electrode contamination alarm is triggered;

[0036] Parameter loading:

[0037] Read the pre-stored calibration parameters from EEPROM, including:

[0038] Electrode response coefficient K: calibrated by BSA standard solution, range 0.8~1.2μA·cm 2 ·s / μg;

[0039] Temperature and humidity compensation coefficient: temperature coefficient a = -0.0002 / °C, humidity coefficient b = 0.0005 / %RH;

[0040] Self-cleaning trigger threshold: signal attenuation > 15% or time > 24h;

[0041] Initialize the Pt temperature sensor and record the current ambient temperature T;

[0042] Step 2, air sampling and protein enrichment, includes:

[0043] Airflow Control:

[0044] The micro air pump draws air at a flow rate of 0.5L / min, and after filtering out particles larger than 1μm through the primary filter, it enters the nanoporous enrichment layer through the 45° inclined air flow hole. The adsorption time t is adaptively adjusted: particles <1μg / m 3 Low concentration scenario: t = 300 seconds; particles ≥ 1 μg / m 3 Medium-to-high concentration scenario: t = 60 seconds;

[0045] Proteins are adsorbed by the amino-modified nanoporous enrichment layer through diffusion and inertial collision, while small molecular pollutants, including formaldehyde, TVOC and particles <100 nm, are discharged with the airflow;

[0046] Enrichment efficiency model:

[0047]

[0048] Among them, V pore is the volume of the porous layer, V air =Q·t is the sampling volume, Q = 0.5L / min;

[0049] Step 3, electrochemical oxidation reaction detection, includes:

[0050] Set the differential pulse voltammetry parameters:

[0051] Scanning voltage range: +0.4V~+0.8V;

[0052] Stepping voltage: 10 mV, pulse amplitude: 50 mV, pulse width: 50 ms;

[0053] Sampling frequency: 100 Hz, and the average value is taken after sampling 10 times at each voltage point;

[0054] Signal acquisition:

[0055] The protein residues on the working electrode undergo an oxidation reaction to generate the characteristic peak current I peak , and the typical peak potential is +0.6 V;

[0056] The current signal is converted into a voltage signal through the potentiostat circuit, and after being sampled by a 12-bit ADC, it is transmitted to the MCU;

[0057] Step 4, signal processing and error compensation, including:

[0058] Baseline correction:

[0059] The baseline current I is calculated by using the 5-minute moving average method base , and the background noise is deducted, L corrected = I peak - I base ;

[0060] Temperature and humidity compensation:

[0061] Temperature compensation: I T = I corrected × (1 + a·(T - 25°C) + b·(T - 25°C) 2 );

[0062] Humidity compensation: According to the value RH of the built-in humidity sensor, the adsorption efficiency is corrected, η RH = η × (1 + 0.0005·(RH - 50%));

[0063] Concentration pre-calculation: where A = 0.09 cm 2 is the effective area of the working electrode;

[0064] Step 5, self-cleaning trigger and execution, including:

[0065] The trigger condition starts when any of the following conditions is met:

[0066] Condition 1: The current detected signal I T decays by more than 15% compared to the initial value, and the judgment formula is:

[0067] Condition 2: The cumulative working time > 24 hours;

[0068] Dual-mode cleaning process:

[0069] Electrochemical cleaning: Apply a reverse voltage of -1.2V to break the disulfide bonds between protein molecules, and the desorption rate > 80%;

[0070] Pyrolysis cleaning: Use a Pt resistance heater to heat up to 250 ± 5°C to carbonize the residual protein, and return to the detection cycle after natural cooling;

[0071] Step 6, Concentration calculation and result output, including:

[0072] Range calibration: If C' > 1000 μg / m 3 , automatically switch to the high-gain mode to avoid signal saturation;

[0073] Final concentration formula: Unit conversion: V air = Q·t with the unit of L and the concentration unit of μg / m 3 ;

[0074] Data output:

[0075] Transmit the concentration value to an external device through the UART protocol, including the main control MCU of the air purifier;

[0076] Store the current detection data in the on-chip Flash.

[0077] By means of the above solution, the electrochemical air protein concentration detection device and method based on nanoporous MEMS have the following technical effects:

[0078] 1) Nanoporous enrichment layer: Utilize the 200nm pore diameter of anodic aluminum oxide (AAO) to selectively adsorb proteins (reject PM2.5 particles and molecular pollutants with a size < 100nm), reducing cross-interference from the source.

[0079] 2) Enzyme-free electrochemical detection: Directly detect the oxidation reaction of tyrosine and tryptophan residues in proteins (+0.6V vs Ag / AgCl), avoiding dependence on biological reagents.

[0080] 3) Electrothermal dual-mode self-cleaning: Electrochemical reduction (-1.2V) breaks protein molecular bonds, combined with 250°C pyrolysis carbonization, to achieve surface regeneration (desorption rate > 98%), and the maintenance cycle is extended to more than 5 years.

[0081] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following describes in detail with the preferred embodiments of the present invention in conjunction with the drawings as follows. Brief description of the drawings

[0082] Figure 1This is a schematic structural diagram of the electrochemistry-based air protein concentration detection device based on nanoporous MEMS of the present invention;

[0083] Figure 2 This is a schematic diagram of the electrochemical detection circuit of the present invention;

[0084] Figure 3 This is a schematic diagram of the self-cleaning timing in the present invention;

[0085] Figure 4 This is a flowchart of the electrochemistry-based air protein concentration detection method based on nanoporous MEMS of the present invention. Detailed implementation manners

[0086] The following combines the drawings and embodiments to further describe in detail the specific implementation manners of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0087] Term explanations:

[0088] Nanoporous MEMS: A nanoporous structure (200 ± 50 nm) with pore diameters at the nanoscale manufactured through microelectromechanical system processes, used for pre-enrichment of target substances.

[0089] Differential pulse voltammetry (DPV): An electrochemistry analysis technique that detects the current of redox reactions by applying pulsed voltages (typical parameters: step 10 mV, pulse 50 mV, width 50 ms).

[0090] Self-cleaning cycle: The time interval during which the device automatically performs electrochemical cleaning and pyrolytic cleaning (default 24 hours).

[0091] See Figure 1 As shown, this embodiment provides an electrochemistry-based air protein concentration detection device based on nanoporous MEMS. This detection device adopts a three-layer stacked MEMS architecture, integrating nanoscale enrichment, microelectrochemistry detection, and self-calibration functions. The total size ≤ 10 mm × 10 mm × 5 mm (volume < 1 cm 3 ), suitable for embedded installation. The specific structure is as follows:

[0092] 1. MEMS silicon substrate

[0093] 1) Structural features

[0094] Material: High-purity single crystal silicon (<100> crystal orientation), thickness 500 μm. The surface forms a microchannel network (width 200 μm, depth 150 μm) through dry etching to guide the airflow to evenly pass through the enrichment layer.

[0095] Integrated Component: Pt Temperature Sensor: A 100Ω platinum resistor (accuracy ±0.5°C) is prepared at the edge of the substrate using a sputtering process to monitor the ambient temperature in real time for signal compensation; Heating Electrode: Shares the Pt resistor with the self-cleaning module (power density ≤1W / cm 2 ), and can be heated to 300°C to achieve pyrolytic cleaning.

[0096] Surface Treatment: Evaporate a 50nm silicon dioxide insulating layer to prevent substrate leakage from interfering with electrochemical signals.

[0097] 2) Connection Relationship

[0098] The bottom support structure realizes vertical electrical connection with the upper enrichment layer and electrode layer through through-silicon vias (TSVs, diameter 50μm).

[0099] The edge pins are wire-bonded to the external PCB to transmit power, control signals, and detection data.

[0100] 3) Function and Effect

[0101] The microchannel design makes the air flow velocity uniformity error <5%, ensuring uniform adsorption of proteins on the surface of the enrichment layer.

[0102] The integrated temperature sensor realizes real-time temperature drift compensation (temperature coefficient -0.02% / °C), improving long-term stability.

[0103] 2. Nano-porous Enrichment Layer

[0104] 1) Structural Characteristics

[0105] Materials and Process: A porous alumina (AAO) layer with a thickness of 50μm, a pore diameter of 200±20nm, and a porosity of 75% (verified by SEM characterization) is prepared on an aluminum foil substrate using an anodic oxidation method. The surface is modified with 3-aminopropyltriethoxysilane (APTES) to form an amino (-NH2) functionalized surface, which binds to the carboxyl group (-COOH) of the protein through an amide bond (binding energy ΔG = -45kJ / mol) to specifically enrich the target substance.

[0106] Geometric Design: The porous layer is arranged at a 45° angle to the air flow direction to increase the probability of protein collision and adsorption. The measured enrichment efficiency is 30% higher than that of the vertical arrangement. A diversion groove (width 100μm) is set at the edge to guide the air flow to evenly cover the entire porous area.

[0107] 2) Connection Relationship

[0108] The bottom is connected to the silicon substrate heating electrode through TSV, and the top forms a conductive path with the working electrode (WE) of the electrochemical electrode array through TSV.

[0109] The air path is sealed with the micro air pump assembly through a PDMS sealing ring (compression rate 30%) to ensure that the air flow only passes through the pores of the porous layer.

[0110] 3) Effect

[0111] The 200nm pore size can effectively screen protein particles larger than 100nm (e.g. BSA molecules with a diameter of 10-15nm can enter freely, while PM2.5 particles larger than 100nm are physically blocked), and the cross-interference rate is less than 3%.

[0112] The amino-modified surface increased the protein adsorption capacity by 2 times (BSA adsorption capacity increased from 6.2 μg / cm 2 Increased to 12.5 μg / cm 2 ).

[0113] 3. Electrochemical electrode array

[0114] 1) Three-electrode system composition

[0115] (1) Working electrode (WE)

[0116] Materials and structure: A 300nm gold layer was deposited on a silicon substrate by electron beam evaporation, and a porous gold structure with a pore size of 5nm (specific surface area > 500m 2 / g, verified by BET test). Effective reaction area 9mm 2 , surface roughness factor>150 (50 times higher than that of planar gold electrodes), increasing the oxidation reaction sites of protein residues (tyrosine, tryptophan).

[0117] Function: Detect protein oxidation peak current (typical peak potential +0.6V vsAg / AgCl) by differential pulse voltammetry (DPV) with a sensitivity of 0.01μA / μg / m 3 .

[0118] (2) Reference electrode (RE)

[0119] Materials and Structure: 0.5 mm diameter Ag / AgCl wire coated with potassium chloride gel (3 M KCl) and isolated from the working electrode by a salt bridge, providing a stable reference potential (+0.205 V vs. standard hydrogen electrode).

[0120] Function: Real-time calibration of the working electrode potential to ensure the detection voltage accuracy is less than ±1mV.

[0121] (3) Counter electrode (CE)

[0122] Materials and structure: 0.3mm diameter platinum wire (purity 99.99%), 5mm length, surface electrochemically polished to reduce background current noise (dark current <10nA).

[0123] Function: Provide the counter electrode current required for redox reactions and maintain the potential balance of the three-electrode system.

[0124] 2) Connection relationship

[0125] The three electrodes form an array pattern through a lithography process and are vertically interconnected with the silicon substrate TSV. The working electrode is in direct electrical contact with the nanoporous enrichment layer (resistance < 1 Ω).

[0126] The signal output terminal is wire-bonded to the potentiostat circuit (LMP91000 chip) through gold wires to achieve current-voltage signal conversion (gain 100 kΩ).

[0127] 3) Effect

[0128] The porous gold electrode increases the oxidation reaction current by 10 times (the peak current of BSA with the same concentration increases from 0.5 μA to 5 μA), and the detection limit is reduced to 0.08 μg / m 3 .

[0129] The three-electrode layout ensures the potential control accuracy and eliminates the IR drop error caused by solution resistance (< 0.5%).

[0130] 4. Micro air pump assembly

[0131] 1) Structural characteristics

[0132] A piezoelectric ceramic micro pump is adopted (size 5 mm × 5 mm × 3 mm), with a flow rate of 0.5 L / min ± 3% (controlled by PID algorithm), and is equipped with an array of 6 air flow holes with a diameter of 2 mm (distributed in a ring shape).

[0133] The air inlet is provided with a primary filter (filtering particles > 1 μm), and the outlet is directly docked with the microchannel of the nanoporous enrichment layer to form a closed-loop gas path.

[0134] 2) Connection relationship

[0135] It is rigidly connected to the MEMS sensor body through a PDMS sealing ring, and the gas path interface adopts a taper fit (tolerance ± 5 μm) to ensure airtightness (leakage rate < 0.1%).

[0136] The power supply and control signals are connected to the edge pins of the silicon substrate through a flexible printed circuit board (FPC).

[0137] 3) Effect

[0138] Constant current sampling at 0.5 L / min makes the protein adsorption amount linearly related to the concentration (R 2 = 0.992), and the response time < 60 seconds (90% response).

[0139] The 45° inclination design of the air flow holes (relative to the surface of the enrichment layer) increases the probability of protein collision adsorption by 25%, and the measured enrichment efficiency is 18% higher than that of vertical air flow.

[0140] Electrochemical detection circuit parameters Figure 2 as shown.

[0141] Component cooperation mechanism:

[0142] 1) Air flow circulation:

[0143] The micro air pump extracts air at a flow rate of 0.5 L / min. After filtering large particles through the primary filter, it enters the nano-porous enrichment layer through the 45° inclined air flow holes. Proteins are adsorbed on the amino surface, and small molecule pollutants and particles <100 nm are discharged with the air flow.

[0144] 2) Signal detection:

[0145] After enrichment is completed, the potentiostat applies a scanning voltage of +0.4 to +0.8 V (DPV mode) to the working electrode. The oxidation of protein residues generates a characteristic current. After I / V conversion and ADC sampling, it is transmitted to the MCU, and the real-time concentration is calculated in combination with the temperature compensation model.

[0146] 3) Self-cleaning process:

[0147] When the detection signal attenuation > 15% or the cumulative working time reaches 24 hours, first apply -1.2 V for electrochemical cleaning for 30 seconds (breaking protein molecular bonds), start pyrolysis cleaning at 250 °C for 60 seconds (carbonizing residual organic matter) after a 5-second interval, monitor the temperature through the Pt sensor to ensure safety, and the adsorption efficiency can be restored to over 98% after cleaning.

[0148] Nano-porous enrichment mechanism:

[0149] The 200 nm pore diameter of anodic aluminum oxide (AAO) forms a size exclusion effect with immunoglobulin (~10 nm).

[0150] Amino silane modification generates electrostatic adsorption (protein pI ≈ 5 - 7, negatively charged at environmental pH = 7).

[0151] Dynamic adsorption model: where the adsorption constant K a = 1.2×10 7 L / mol.

[0152] Enrichment efficiency calculation:

[0153] The volume of the porous layer is calculated by analyzing SEM images.

[0154] The specific surface area is measured by the BET nitrogen adsorption method (typical value 500 ± 50 m 2 / g).

[0155] Verification of enrichment efficiency experiment: Using 0.1 μg / m 3 BSA aerosol test, the deviation between the measured value and the theoretical value < 5%.

[0156] Electrochemical oxidation mechanism:

[0157] Tyrosine residue undergoes irreversible oxidation at +0.6V:

[0158] Tyrosine→Quinone+2H + +2e -

[0159] Optimization of differential pulse voltammetry (DPV) parameters: Pulse height: 50 mV (optimal signal-to-noise ratio); Scanning rate: 10 mV / s (balancing sensitivity and response time).

[0160] Self-cleaning timing (as shown in Figure 3 )

[0161] Self-cleaning principle:

[0162] Electrochemical cleaning: -1.2V reduction destroys the protein-electrode bonding (breaking the disulfide bonds between protein molecules through -1.2V reduction reaction).

[0163] Pyrolytic cleaning: 250°C decomposes the protein into CO2 and H2O (thermogravimetric analysis shows 98% mass loss).

[0164] Synergistic effect: First, electrochemically remove 85% of the adsorbates, and the remaining 15% is completely removed by pyrolysis.

[0165] Signal processing algorithm:

[0166] Baseline correction: Use the moving average method to eliminate background drift (window width 5 minutes).

[0167] Temperature and humidity compensation: Based on second-order polynomial fitting (temperature coefficient -0.02% / °C, humidity coefficient +0.05% / RH).

[0168] As shown in Figure 4 , the specific process of the detection method of this device is as follows:

[0169] Step 1: System initialization and parameter calibration.

[0170] Hardware self-check:

[0171] 1) The micro air pump starts to run idly for 30 seconds, and detects whether the flow rate is stable at 0.5 L / min ± 3% (feedback through the built-in pressure sensor).

[0172] 2) Calibrate the potentiostat circuit to measure the baseline current of the three - electrode system (the dark current should be < 10 nA, otherwise trigger the electrode contamination alarm).

[0173] Parameter loading:

[0174] 1) Read the pre - stored calibration parameters from the EEPROM: the electrode response coefficient K (calibrated with BSA standard solution, range 0.8 - 1.2 μA·cm 2 ·s / μg). Temperature and humidity compensation coefficients (temperature coefficient a = - 0.0002 / °C, humidity coefficient b = 0.0005 / %RH). Self - cleaning trigger threshold (signal attenuation > 15% or time > 24 h).

[0175] 2) Initialize the Pt temperature sensor and record the current ambient temperature T (accuracy ±0.5 °C).

[0176] Step 2: Air sampling and protein enrichment

[0177] Airflow control:

[0178] 1) The micro - air pump draws air at a flow rate of 0.5 L / min. After filtering particles larger than 1 μm through the primary filter, it enters the nano - porous enrichment layer through a 45° inclined air - flow hole (the adsorption time t is adaptively adjusted: low - concentration scenario (< 1 μg / m 3 ): t = 300 s; medium - to - high - concentration scenario (≥1 μg / m 3 ): t = 60 s).

[0179] 2) Proteins (particle size 10 - 200 nm) are adsorbed by the amino - modified porous layer through diffusion and inertial collision, and small - molecule pollutants (such as formaldehyde, TVOC) and particles smaller than 100 nm are discharged with the air flow.

[0180] Enrichment efficiency model:

[0181] (Note: V pore is the volume of the porous layer, V air = Q·t is the sampling volume, Q = 0.5 L / min).

[0182] Step 3: Electrochemical oxidation reaction detection.

[0183] Differential pulse voltammetry (DPV) parameters:

[0184] Scanning voltage range: + 0.4 V to + 0.8 V (vs Ag / AgCl reference electrode).

[0185] Step voltage: 10 mV, pulse amplitude: 50 mV, pulse width: 50 ms.

[0186] Sampling frequency: 100 Hz, and the average value is taken after collecting 10 times for each voltage point (to reduce noise).

[0187] Signal acquisition:

[0188] 1) Oxidation reactions occur on the protein residues (tyrosine, tryptophan) on the working electrode (porous gold), generating a characteristic peak current I peak (Typical peak potential +0.6 V).

[0189] 2) The potentiostat circuit (LMP91000 chip) converts the current signal into a voltage signal (gain 100 kΩ), and after 12-bit ADC sampling, it is transmitted to the MCU.

[0190] Step 4: Signal processing and error compensation.

[0191] Baseline correction:

[0192] The moving average method over 5 minutes is used to calculate the baseline current I base , and the background noise is deducted (formula: I corrected = I peak - I base ).

[0193] Temperature and humidity compensation:

[0194] 1) Temperature compensation: I T = I corrected ×(1 + a·(T - 25°C) + b·(T - 25°C) 2 ).

[0195] 2) Humidity compensation: According to the value of the built-in humidity sensor RH, the adsorption efficiency is corrected (formula: η RH = η×(1 + 0.0005·(RH - 50%))).

[0196] Concentration pre-calculation: (A = 0.09 cm 2 is the effective area of the working electrode)

[0197] Step 5: Self-cleaning trigger and execution.

[0198] Trigger conditions (start when any condition is met):

[0199] 1) The current detected signal I T decays by more than 15% compared to the initial value (judgment formula: ).

[0200] 2) The cumulative working time > 24 hours (timed by the on-chip RTC).

[0201] Dual-mode cleaning process:

[0202] 1) Electrochemical cleaning (30 s): Apply a reverse voltage of -1.2 V (pulse mode with a duty cycle of 20%), break the disulfide bonds between protein molecules, and the desorption rate > 80%.

[0203] 2) Pyrolysis cleaning (60 s): Heat the Pt resistance heater to 250 ± 5 °C (heating rate 10 °C / s), carbonize the residual protein (mass loss > 98%), and return to the detection cycle after natural cooling.

[0204] Step 6: Concentration calculation and result output.

[0205] Range calibration: If C' > 1000 μg / m 3 , automatically switch to the high-gain mode (amplification factor increased to 1 MΩ) to avoid signal saturation.

[0206] Final concentration formula: (Unit conversion: V air = Q·t, unit is L, concentration unit is μg / m 3 ).

[0207] Data output:

[0208] 1) Transmit the concentration value (resolution 0.01 μg / m 3 ) to an external device (such as the main control MCU of an air purifier) through the UART protocol.

[0209] 2) Store the current detection data in the on-chip Flash (recorded once per hour, storage capacity can support 3 years of data).

[0210] Key algorithm details:

[0211] Calibration of the electrode response coefficient K:

[0212] Use BSA standard aerosols with different concentrations (0.08 - 1000 μg / m 3 ) to establish the linear relationship between I peak and concentration (fitting formula I peak = K·C·A·t·η), and calculate K through the least squares method (laboratory calibration R 2 = 0.992).

[0213] Verification of self-cleaning effect:

[0214] Detect BSA at the same concentration after cleaning, and the peak current recovery rate > 95% (electrochemical cleaning contributes 60% desorption, pyrolysis cleaning contributes 35% desorption, and the residue < 5%).

[0215] Anti-interference correction:

[0216] When the detected ambient PM2.5 > 200 μg / m 3When this occurs, the adsorption time is automatically extended to 180 seconds (by increasing the sampling volume to reduce random error, the measured deviation is reduced from +8% to +3%).

[0217] Key performance verification:

[0218] Adsorption selectivity:

[0219] A mixed aerosol of BSA with a particle size of 150 nm and PM2.5 with a particle size of 50 nm was used for testing. The adsorption amount of BSA by the enrichment layer is 8 times that of PM2.5 (SEM images show that PM2.5 particles only adhere to the surface of the porous layer and do not enter the pores).

[0220] Electrode stability:

[0221] A BSA solution (0.1 μg / m 3 ) was continuously detected 1000 times, and the peak current drift < 5%, which is better than that of traditional electrochemical sensors (drift > 20%).

[0222] Gas path sealing:

[0223] Tested under a pressure difference of 10 kPa, the leakage rate < 5×10 -6 mL / s, ensuring no detection deviation caused by air flow leakage during long-term operation.

[0224] Examples

[0225] 1. Technical parameters are shown in Table 1.

[0226] Table 1 Technical parameters

[0227]

[0228] 2. Performance indicators are shown in Table 2.

[0229] Table 2 Performance indicators

[0230]

[0231]

[0232] Laboratory data:

[0233] 1. Adsorption efficiency test is shown in Table 3.

[0234] Table 3 Adsorption efficiency test results

[0235] Protein type <![CDATA[Adsorption capacity (μg / cm 2 )]]> Desorption rate (%) BSA 12.5 98.7 (after pyrolysis cleaning) IgG 8.3 97.2 Lysozyme 15.2 99.1

[0236] 2. Cross-interference test is shown in Table 4.

[0237] Table 4 Cross-interference test results

[0238] Interferent <![CDATA[Concentration (μg / m 3 )]]> Response deviation PM2.5 500 +2.1％ Formaldehyde 0.5 ppm -1.8％ TVOC 1 ppm +3.5％

[0239] The present invention has the following technical effects compared with the prior art:

[0240] 1) The present invention combines nano-porous MEMS and enzyme-free electrochemistry for protein detection for the first time.

[0241] 2) An electro-thermal dual-mode self-cleaning system is adopted to break through the maintenance bottleneck of traditional sensors.

[0242] 3) Miniaturized design (volume < 1 cm 3 ) + low cost (< 200 yuan), suitable for home appliance integration, and the purification efficiency is increased by 40%.

[0243] 4) Ultra-sensitive detection: The detection limit reaches 0.08 μg / m 3 , which is 6 times higher than that of the traditional electrochemical method.

[0244] 5) Long-term maintenance-free: The self-cleaning system extends the maintenance cycle to 5 years.

[0245] 6) Anti-interference ability: The nano-porous structure selectively adsorbs proteins (rejects interfering substances with a particle size < 100 nm).

[0246] The comparison table of the prior art is shown in Table 5.

[0247] Table 5 Comparison Table of the Prior Art

[0248]

[0249] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An electrochemical air protein concentration detection device based on nanoporous MEMS, characterized in that It includes a MEMS sensor body, a micro air pump assembly, and a self-cleaning module. The MEMS sensor body includes a MEMS silicon substrate, a nanoporous enrichment layer, and an electrochemical electrode array. The electrochemical electrode array is composed of a working electrode, a reference electrode, and a counter electrode to form a three-electrode system. The MEMS silicon substrate is made of high-purity single-crystal silicon, and a microchannel network is formed on its surface by dry etching. The MEMS silicon substrate is integrated with a Pt temperature sensor and a heating electrode. The heating electrode uses a Pt resistance heater. The self-cleaning module and the MEMS silicon substrate share the Pt resistance heater. The nanoporous enrichment layer is formed by preparing a porous aluminum oxide layer on an aluminum foil substrate using an anodic oxidation method, and its surface is modified with 3-aminopropyltriethoxysilane; the bottom of the nanoporous enrichment layer is connected to the heating electrode of the MEMS silicon substrate through a silicon through-hole via, and the top of the nanoporous enrichment layer forms a conductive path with the working electrode of the electrochemical electrode array through a silicon through-hole via; the nanoporous enrichment layer and the micro air pump assembly are sealed by a PDMS sealing ring to ensure that the airflow only passes through the pores of the nanoporous enrichment layer. The working electrode, reference electrode, and counter electrode are formed into an array pattern by a photolithography process and vertically interconnected with the through-silicon vias of the MEMS silicon substrate; the signal output ends of the working electrode, reference electrode, and counter electrode are bonded to the potentiostat circuit by gold wires to realize current-voltage signal conversion; The micro air pump assembly includes a micro air pump, an air flow inlet of the micro air pump is provided with a primary filter, and an outlet is directly connected to the micro channel of the nanoporous enrichment layer to form a closed-loop air path.

2. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 1, characterized in that, A 50nm silicon dioxide insulating layer is evaporated on the surface of the MEMS silicon substrate to prevent substrate leakage from interfering with electrochemical signals; the edge pins of the MEMS silicon substrate are bonded to the external PCB through gold wires to transmit power, control signals and detection data.

3. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 1, characterized in that, The nanoporous enrichment layer is arranged at an angle of 45 degrees to the airflow direction to increase the probability of protein collision adsorption; a guide groove is provided at the edge of the nanoporous enrichment layer to guide the airflow to evenly cover the entire porous area.

4. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 3, wherein The nanoporous enrichment layer has a pore size of 150-250 nm and a porosity of ≥70%.

5. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 1, wherein, The working electrode is made by depositing a 300nm gold layer on the MEMS silicon substrate using electron beam evaporation, and then electrochemically corroding to form a porous gold structure with a pore size of 5nm; the reference electrode is made of Ag or AgCl wire with a diameter of 0.5mm, the surface of which is coated with potassium chloride gel and isolated from the working electrode by a salt bridge to provide a stable reference potential; the counter electrode is made of platinum wire with a diameter of 0.3mm and a length of 5mm, and the surface of which is electrochemically polished to reduce background current noise.

6. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 1, wherein The micro air pump assembly adopts a piezoelectric ceramic micro pump and has a plurality of air flow hole arrays distributed in a ring shape.

7. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 6, characterized in that, The power supply and control signal of the micro air pump assembly are connected to the edge pins of the MEMS silicon substrate through a flexible circuit board.

8. A method for detecting air protein concentration using the device according to claims 1 to 7, characterized in that, The steps include: Step 1: System initialization and parameter calibration, including: Hardware self-test: The micro air pump starts to run idly for 30 seconds to detect whether the flow rate is stable at 0.5L / min ± 3%; The potentiostat circuit calibrates the baseline current of the three electrodes. If the dark current > 10nA, it triggers the electrode contamination alarm; Parameter loading: Read the pre-stored calibration parameters from the EEPROM, including: Electrode response coefficient K: Calibrated with BSA standard solution, in the range of 0.8 - 1.2 μA·cm 2 ·s / μg; Temperature and humidity compensation coefficients: temperature coefficient a = -0.0002 / °C, humidity coefficient b = 0.0005 / %RH; Self-cleaning trigger threshold: signal attenuation > 15% or time > 24h; Initialize the Pt temperature sensor and record the current ambient temperature T; Step 2, air sampling and protein enrichment, including: Airflow control: The micro air pump extracts air at a flow rate of 0.5 L / min. After filtering particles larger than 1 μm through a primary filter, the air enters the nano-porous enrichment layer through the air flow holes inclined at 45°. The adsorption time t is adjusted adaptively: for low-concentration scenarios where the particle concentration is < 1 μg / m 3 : t = 300 seconds; for medium- and high-concentration scenarios where the particle concentration is ≥ 1 μg / m 3 : t = 60 seconds; Proteins are adsorbed by the amino-modified nanoporous enrichment layer through diffusion and inertial collision, and small molecule pollutants, including formaldehyde, TVOC, and particles < 100nm, are discharged with the airflow; Enrichment efficiency model: Among them, V pore is the volume of the porous layer, V air = Q·t is the sampling volume, Q = 0.5 L / min; Step 3, electrochemical oxidation reaction detection, including: Set the differential pulse voltammetry parameters: Scanning voltage range: +0.4V to +0.8V; Step voltage: 10mV, pulse amplitude: 50mV, pulse width: 50ms; Sampling frequency: 100Hz, and the average value is taken after collecting 10 times at each voltage point; Signal acquisition: The protein residues on the working electrode undergo an oxidation reaction, generating a characteristic peak current I peak , with a typical peak potential of +0.6 V; Convert the current signal to a voltage signal through the potentiostat circuit, and transmit it to the MCU after 12-bit ADC sampling; Step 4, signal processing and error compensation, including: Baseline correction: The baseline current I is calculated using a 5-minute moving average method base , and the background noise is subtracted. I corrected = I peak - I base ; Temperature and humidity compensation: Temperature compensation: I T = L corrected × (1 + a·(T - 25°C) + b·(T - 25°C) 2 ); Humidity compensation: According to the built-in humidity sensor value RH, correct the adsorption efficiency η RH = η × (1 + 0.0005·(RH - 50%)); Concentration pre-calculation: where A = 0.09 cm 2 is the effective area of the working electrode; Step 5, self-cleaning trigger and execution, including: The trigger condition starts when any of the following conditions is met: Condition 1: Current detection signal I T Decay > 15% compared to the initial value, judgment formula: Condition 2: cumulative working time > 24 hours; Dual-mode cleaning process: Apply a -1.2V reverse voltage for electrochemical cleaning to break the disulfide bonds between protein molecules, and the desorption rate > 80%; Pyrolysis cleaning: The Pt resistance heater is heated to 250 ± 5°C to carbonize the residual proteins, and then returns to the detection cycle after natural cooling; Step 6, concentration calculation and result output, including: Range calibration: If C’ > 1000 μg / m 3 , automatically switch to the high-gain mode to avoid signal saturation; Final concentration formula: Unit conversion: V air = Q·t with the unit of L and the concentration unit of μg / m 3 ; Data output: Transmit the concentration value to an external device, including the main control MCU of the air purifier, through the UART protocol; Store the current detection data in the on-chip Flash.

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