A nanoporous mems-based electrochemical air protein concentration detection device and method

Abstract

This invention relates to an electrochemical air protein concentration detection device and method based on nanoporous MEMS. The device 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 consists of a working electrode, a reference electrode, and a counter electrode. The MEMS silicon substrate integrates a Pt temperature sensor and a heating electrode. The surface of the nanoporous enrichment layer is modified with 3-aminopropyltriethoxysilane. The bottom of the layer is connected to the heating electrode of the MEMS silicon substrate through through-silicon vias, and the top of the layer forms a conductive path with the working electrode of the electrochemical electrode array through through-silicon vias. The nanoporous enrichment layer and the micro air pump assembly are sealed together by a PDMS sealing ring. This invention pre-enriches air proteins using a nanoporous MEMS structure, achieves quantitative detection using an enzyme-free electrochemical oxidation reaction, and integrates an electrothermal dual-mode self-cleaning system, solving the problems of high cost and complex maintenance in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of air protein concentration detection technology, and particularly relates to an electrochemical air protein concentration detection device and method based on nanoporous MEMS. Background Technology

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

[0003] 1) Laboratory testing methods

[0004] ELISA (Enzyme-Linked Immunosorbent Assay)

[0005] Proteins can be quantified using antibody-antigen specific binding reactions, with a detection limit as low as 0.01 μg / m³. 3 However, it relies on expensive biological reagents (monoclonal antibody cost > 50 yuan / test), and the detection cycle is long (> 2 hours), making real-time online monitoring impossible and only suitable for offline sample analysis.

[0006] Mass spectrometry

[0007] Based on electrospray ionization-mass spectrometry (ESI-MS) technology, it can identify the molecular weight fingerprint of proteins with extremely high accuracy, but the equipment is bulky (>0.5m). 3 It has a power consumption of over 200W and requires professional operation, making it unsuitable for integration into home appliances.

[0008] 2) Portable detection technology

[0009] Optical sensors

[0010] Detection is achieved using ultraviolet absorption (280nm) or fluorescent labeling of proteins. However, due to limitations in light scattering efficiency and ambient light interference, the error is >20% under complex lighting conditions (such as indoors under direct sunlight), and the cost of the optical system is >3000 yuan, making it difficult to popularize.

[0011] Traditional electrochemical sensors

[0012] The detection limit is 0.2 μg / m² based on the catalytic current signal of the antigen-antibody reaction. 3 However, the bio-modified layer is susceptible to deactivation due to humidity and temperature (lifespan < 3 months), and the electrodes need to be replaced regularly (consumable cost > 100 yuan / time), which cannot meet the long-term maintenance-free requirements of home appliances.

[0013] 3) MEMS micro / nano sensor technology

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

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

[0016] A certain patent uses nanowire field-effect transistors (FETs) to modify antibodies, with a detection limit of 0.1 μg / m 3 However, the biomolecular layer on the surface of nanowires is easily covered by contaminants, leading to signal attenuation (drift >30% per week) and requiring frequent calibration.

[0017] In summary, the existing technology has the following technical defects:

[0018] Summary of the Invention

[0019] The purpose of this invention is to provide an electrochemical air protein concentration detection device and method based on nanoporous MEMS. The device pre-enriches air proteins through a nanoporous MEMS structure, achieves quantitative detection using an enzyme-free electrochemical oxidation reaction, and integrates an electrothermal dual-mode self-cleaning system, thus solving the problems of high cost and complex maintenance in existing technologies.

[0020] This invention provides an electrochemical air protein concentration detection device based on nanoporous MEMS, comprising 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 consists of a working electrode, a reference electrode, and a counter electrode, forming a three-electrode system.

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

[0022] The nanoporous enrichment layer is formed by anodic oxidation of 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 through-silicon vias, and the top is connected to the working electrode of the electrochemical electrode array through through-silicon vias to form a conductive path. The nanoporous enrichment layer and the micro air pump assembly are sealed with a PDMS sealing ring to ensure that the airflow only passes through the pores of the nanoporous enrichment layer.

[0023] The working electrode, reference electrode, and counter electrode are formed into an array pattern through photolithography and are vertically interconnected with the through-silicon vias of the MEMS silicon substrate; the signal output terminals of the working electrode, reference electrode, and counter electrode are bonded to a potentiostat circuit through gold wire bonding to realize current-to-voltage signal conversion.

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

[0025] Furthermore, a 50nm silicon dioxide insulating layer is deposited 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 an external PCB via gold wire bonding for transmitting power, control signals, and detection data.

[0026] Furthermore, the nanoporous enrichment layer is arranged at a 45° angle to the airflow direction to increase the probability of protein collision and adsorption; the edge of the nanoporous enrichment layer is provided with a flow guide groove to guide the airflow to uniformly cover the entire porous area.

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

[0028] Furthermore, the working electrode is fabricated by depositing a 300nm gold layer on the MEMS silicon substrate using electron beam evaporation, followed by electrochemical etching 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, 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 its surface is electrochemically polished to reduce background current noise.

[0029] Further, the micro air pump assembly is a piezoelectric ceramic micro pump with multiple airflow holes arranged in a ring.

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

[0031] The present invention also provides a method for detecting air protein concentration using the aforementioned device, characterized by comprising the following steps:

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

[0033] Hardware self-test:

[0034] The miniature air pump is started and idled for 30 seconds to check if the flow rate is stable at 0.5L / min ± 3%.

[0035] The potentiostat circuit verifies the baseline current of the three electrodes. If the dark current is >10nA, an electrode contamination alarm is triggered.

[0036] Parameter loading:

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

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

[0039] Temperature and humidity compensation coefficients: Temperature coefficient a = -0.0002 / ℃, 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] A miniature air pump draws air at a flow rate of 0.5 L / min. After passing through a pre-filter to remove particles >1 μm, the air enters the nanoporous enrichment layer through 45° inclined airflow holes. The adsorption time t is adaptively adjusted for particles <1 μg / m². 3 Low concentration scenario: t = 300 seconds; particles ≥ 1 μg / m³ 3 Medium to high concentration scenarios: t = 60 seconds;

[0045] Proteins are adsorbed by amino-modified nanoporous enrichment layers through diffusion and inertial collisions, while small molecule pollutants, including formaldehyde, TVOC and particles <100nm, are discharged with the airflow.

[0046] Enrichment efficiency model:

[0047]

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

[0049] Step 3, detection of electrochemical oxidation reaction, including:

[0050] Setting parameters for differential pulse voltammetry:

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

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

[0053] Sampling frequency: 100Hz, 10 samples are collected for each voltage point and the average value is taken;

[0054] Signal acquisition:

[0055] The protein residues on the working electrode undergo oxidation, generating a characteristic peak current I. peak Typical peak potential +0.6V;

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

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

[0058] Baseline correction:

[0059] Baseline current I was calculated using the 5-minute moving average method. base After removing background noise, L corrected =I peak -I base ;

[0060] Temperature and humidity compensation:

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

[0062] Humidity compensation: Corrects adsorption efficiency (η) based on the RH value from the built-in humidity sensor. RH =η×(1+0.0005·(RH-50%));

[0063] Preliminary concentration calculation: Where A = 0.09cm 2 The effective area of ​​the working electrode;

[0064] Step 5, self-cleaning triggering and execution, includes:

[0065] The system will start if any of the following conditions are met:

[0066] Condition 1: Current detection signal I T If the attenuation from the initial value is greater than 15%, the judgment formula is:

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

[0068] Dual-mode cleaning process:

[0069] Electrochemical cleaning: Applying a reverse voltage of -1.2V breaks the disulfide bonds between protein molecules, with a desorption rate >80%;

[0070] Pyrolysis cleaning: The Pt resistance heater heats the temperature to 250±5℃ to carbonize the residual protein, and after natural cooling, it is returned to the detection cycle;

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

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

[0073] Final concentration formula: Unit conversion: V air =Q·t, where the unit is L, and the concentration unit is μg / m³. 3 ;

[0074] Data output:

[0075] The concentration value is transmitted to external devices, including the air purifier's main control MCU, via the UART protocol;

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

[0077] By employing the above-described scheme, the electrochemical air protein concentration detection device and method based on nanoporous MEMS achieves the following technical effects:

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

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

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

[0081] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

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

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

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

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

[0086] The following combines the accompanying drawings and embodiments to further describe in detail the detailed 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 nanopore-sized porous structure (200 ± 50 nm) fabricated through microelectromechanical system processes, used for pre-concentration of target substances.

[0089] Differential pulse voltammetry (DPV): An electrochemistry analysis technique that detects redox reaction currents 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 electrochemistry cleaning and pyrolysis cleaning (default 24 hours).

[0091] Refer Figure 1 As shown, this embodiment provides an electrochemistry-based air protein concentration detection device using nanoporous MEMS. This detection device adopts a three-layer stacked MEMS architecture, integrating nano-level enrichment, micro-electrochemistry 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 air flow to evenly pass through the enrichment layer.

[0095] Integrated components: Pt temperature sensor: A 100Ω platinum resistance thermometer (accuracy ±0.5℃) is fabricated on the substrate edge using a sputtering process to monitor ambient temperature in real time for signal compensation; Heating electrode: A shared Pt resistor (power density ≤1W / cm²) with the self-cleaning module. 2 It can be heated to 300℃ to achieve pyrolysis cleaning.

[0096] Surface treatment: A 50nm silicon dioxide insulating layer is vapor-deposited to prevent substrate leakage from interfering with electrochemical signals.

[0097] 2) Connection relationship

[0098] The bottom support structure is vertically electrically connected to the upper enrichment layer and electrode layer through through silicon vias (TSVs, 50μm in diameter).

[0099] Edge pins are bonded to an external PCB via gold wire bonding to transmit power, control signals, and detection data.

[0100] 3) Effects

[0101] The microchannel design ensures that the airflow velocity uniformity error is less than 5%, guaranteeing that proteins are uniformly adsorbed on the enrichment layer surface.

[0102] An integrated temperature sensor enables real-time temperature drift compensation (temperature coefficient -0.02% / ℃), improving long-term stability.

[0103] 2. Nanoporous enrichment layer

[0104] 1) Structural features

[0105] Materials and Processes: A porous alumina (AAO) layer with a thickness of 50 μm, a pore size of 200 ± 20 nm, and a porosity of 75% was prepared on an aluminum foil substrate using anodizing. The surface was then modified with 3-aminopropyltriethoxysilane (APTES) to form an amino (-NH2) functionalized surface, which binds to the protein carboxyl groups (-COOH) via amide bonds (binding energy ΔG = -45 kJ / mol), specifically enriching the target analytes.

[0106] Geometric design: The porous layer is arranged at a 45° angle to the airflow direction, increasing the probability of protein collision and adsorption. The measured enrichment efficiency is 30% higher than that of vertical arrangement. The edge is set with a guide groove (100μm wide) to guide the airflow to uniformly cover the entire porous area.

[0107] 2) Connection relationship

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

[0109] The air path is sealed with the micro air pump assembly through a PDMS sealing ring (30% compression ratio), ensuring that the airflow passes only through the pores of the porous layer.

[0110] 3) Effects

[0111] The 200nm pore size effectively filters protein particles larger than 100nm (such as BSA molecules with a diameter of 10-15nm, which can freely enter, while PM2.5 particles larger than 100nm are physically blocked), with a cross-interference rate of <3%.

[0112] Amino-modified surfaces increased protein adsorption capacity by 2 times (BSA adsorption capacity increased from 6.2 μg / cm³ under the same conditions). 2 Increased to 12.5 μg / cm 2 ).

[0113] 3. Electrochemical electrode array

[0114] 1) Three-electrode system configuration

[0115] (1) Working electrode (WE)

[0116] Materials and Structure: A 300 nm gold layer was deposited on a silicon substrate using electron beam evaporation, followed by electrochemical etching to form a porous gold structure with a pore size of 5 nm (specific surface area > 500 m²). 2 / g (verified by BET test). Effective reaction area: 9mm² 2 The surface roughness factor is >150 (50 times higher than that of planar gold electrodes), increasing the oxidation reaction sites of protein residues (tyrosine, tryptophan).

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

[0118] (2) Reference electrode (RE)

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

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

[0121] (3) Counter electrode (CE)

[0122] Materials and Structure: Platinum wire with a diameter of 0.3 mm (99.99% purity), 5 mm in length, with electrochemical polishing treatment to reduce background current noise (dark current <10 nA).

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

[0124] 2) Connection relationship

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

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

[0127] 3) Effects

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

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

[0130] 4. Miniature air pump assembly

[0131] 1) Structural features

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

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

[0134] 2) Connection relationship

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

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

[0137] 3) Effects

[0138] Constant current sampling at 0.5 L / min resulted in a linear relationship between protein adsorption and concentration (R0). 2 =0.992), and the response time is <60 seconds (90% response).

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

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

[0141] Component collaborative working mechanism:

[0142] 1) Airflow circulation:

[0143] The micro air pump draws in air at a flow rate of 0.5L / min. After large particles are filtered by the primary filter, the air enters the nanoporous enrichment layer through the 45° inclined airflow holes. Proteins are adsorbed on the amino surface, while small molecule pollutants and particles <100nm are discharged with the airflow.

[0144] 2) Signal detection:

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

[0146] 3) Self-cleaning process:

[0147] When the detection signal decays by more than 15% or the cumulative working time is 24 hours, apply -1.2V electrochemical cleaning for 30 seconds (breaks protein molecular bonds), and after a 5-second interval, start 250℃ pyrolysis cleaning for 60 seconds (carbonizes residual organic matter). The temperature is monitored by a Pt sensor to ensure safety. After cleaning, the adsorption efficiency is restored to more than 98%.

[0148] Nanoporous enrichment mechanism:

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

[0150] Aminosilane modification produces electrostatic adsorption (protein pI≈5-7, negatively charged at ambient 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 was calculated through SEM image analysis.

[0154] Specific surface area was determined by BET nitrogen adsorption method (typical value 500±50 m²). 2 / g).

[0155] Enrichment efficiency experimental verification: Using 0.1 μg / m 3 BSA aerosol test, the deviation between the measured value and the theoretical value is < 5%.

[0156] Electrochemical oxidation mechanism:

[0157] Tyrosine residues undergo irreversible oxidation at +0.6V:

[0158] Tyrosine→Quinone+2H + +2e -

[0159] Differential pulse voltammetry (DPV) parameter optimization: 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 the -1.2V reduction reaction).

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

[0164] Synergistic effect: First, 85% of the adsorbed substances are removed electrochemically, and the remaining 15% are completely removed by pyrolysis.

[0165] Signal processing algorithm:

[0166] Baseline correction: Using 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 checks whether the flow rate is stable at 0.5 L / min ± 3% (feedback through the built-in pressure sensor).

[0172] 2) Verify the baseline current of the three electrodes using the potentiostat circuit (the dark current should be <10nA, otherwise an electrode contamination alarm will be triggered).

[0173] Parameter loading:

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

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

[0176] Step 2: Air sampling and protein enrichment

[0177] Airflow control:

[0178] 1) A micro air pump draws air at a flow rate of 0.5 L / min. After filtering particles >1 μm through a pre-filter, the air enters the nanoporous enrichment layer through 45° inclined airflow holes (adsorption time t is adaptively adjusted: for low concentration scenarios (<1 μg / m³)). 3 ): t = 300 seconds; medium to high concentration scenarios (≥1 μg / m³) 3 ): t = 60 seconds.

[0179] 2) Proteins (particle size 10-200nm) are adsorbed by amino-modified porous layers through diffusion and inertial collisions, while small molecule pollutants (such as formaldehyde and TVOC) and particles <100nm are discharged with the airflow.

[0180] Enrichment efficiency model:

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

[0182] Step 3: Detection of electrochemical oxidation reaction.

[0183] Differential pulse voltammetry (DPV) parameters:

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

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

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

[0187] Signal acquisition:

[0188] 1) The protein residues (tyrosine, tryptophan) on the working electrode (porous gold) undergo an oxidation reaction, generating a characteristic peak current I. peak (Typical peak potential +0.6V).

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

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

[0191] Baseline correction:

[0192] Baseline current I was calculated using the 5-minute moving average method. base Background noise is subtracted (formula: I) corrected =I peak -I base ).

[0193] Temperature and humidity compensation:

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

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

[0196] Preliminary concentration calculation: (A=0.09cm 2 (Effective area of ​​the working electrode)

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

[0198] Triggering conditions (starts when any one condition is met):

[0199] 1) Current detection signal I T Attenuation from initial value > 15% (judgment formula: ).

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

[0201] Dual-mode cleaning process:

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

[0203] 2) Pyrolysis cleaning (60 seconds): The Pt resistance heater heats the material to 250±5℃ (heating rate 10℃ / s) to carbonize the residual protein (mass loss >98%). After natural cooling, the material is returned to the detection cycle.

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

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

[0206] Final concentration formula: (Unit conversion: V) air =Q·t, where the unit is L, and the concentration unit is μg / m³. 3 ).

[0207] Data output:

[0208] 1) The concentration value (resolution 0.01 μg / m³) is transmitted via UART protocol. 3 Transmitted to external devices (such as the main control MCU of an air purifier).

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

[0210] Key algorithm details:

[0211] Electrode response coefficient K calibration:

[0212] Using BSA standard aerosols of different concentrations (0.08-1000 μg / m³) 3 ), establish I peak Linear relationship with concentration (fitting formula I) peak =K·C·A·t·η), K is calculated using the least squares method (laboratory calibration R). 2 =0.992).

[0213] Self-cleaning effect verification:

[0214] After cleaning, the peak current recovery rate of the same concentration of BSA was >95% (electrochemical cleaning contributed 60% of desorption, pyrolysis cleaning contributed 35% of desorption, and residue <5%).

[0215] Anti-interference correction:

[0216] When the ambient PM2.5 concentration is greater than 200 μg / m³ 3At that time, the adsorption time was automatically extended to 180 seconds (by increasing the sampling volume to reduce random error, the measured deviation was reduced from +8% to +3%).

[0217] Key performance verification:

[0218] Adsorption selectivity:

[0219] The mixture of BSA (150 nm) and PM2.5 (50 nm) aerosols was tested. The adsorption capacity of the enrichment layer for BSA was 8 times that for PM2.5 (SEM images showed that PM2.5 particles only adhered to the surface of the porous layer and did not enter the pores).

[0220] Electrode stability:

[0221] Continuous testing of BSA solution (0.1 μg / m) 1000 times 3 The peak current drift is <5%, which is better than that of traditional electrochemical sensors (drift >20%).

[0222] Gas circuit sealing:

[0223] Tested under a pressure difference of 10 kPa, the leakage rate was <5 × 10⁻⁶. -6 mL / s ensures that there are no detection deviations caused by airflow leakage during long-term operation.

[0224] Example

[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, see Table 3.

[0234] Table 3 Adsorption efficiency test results

[0235] Protein types <![CDATA[Adsorption amount (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, see Table 4.

[0237] Table 4 Cross-interference test results

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

[0239] Compared with the prior art, the present invention has the following technical effects:

[0240] 1) This invention is the first to combine nanoporous MEMS with enzyme-free electrochemistry for protein detection.

[0241] 2) The system adopts a dual-mode self-cleaning system of electrothermal heating, breaking through the bottleneck of traditional sensor maintenance.

[0242] 3) Adopts miniaturized design (volume < 1cm) 3 Low cost (<200 yuan), suitable for home appliance integration, and improves purification efficiency by 40%.

[0243] 4) Ultrasensitive detection: Detection limit down to 0.08 μg / m 3 It is 6 times more efficient than 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 nanoporous structure selectively adsorbs proteins (repelling interfering substances with a particle size <100nm).

[0246] The comparison table of existing technologies is shown in Table 5.

[0247] Table 5 Comparison of Existing Technologies

[0248]

[0249] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrochemical air protein concentration detection device based on nanoporous MEMS, characterized in that, The device 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 consists of a working electrode, a reference electrode, and a counter electrode, forming a three-electrode system. The MEMS silicon substrate is made of high-purity single-crystal silicon, and its surface is formed into a microfluidic network by dry etching; the MEMS silicon substrate integrates a Pt temperature sensor and a heating electrode; the heating electrode is a Pt resistance heater; the self-cleaning module shares the Pt resistance heater with the MEMS silicon substrate; The nanoporous enrichment layer is formed by anodic oxidation of 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 through-silicon vias, and the top of the nanoporous enrichment layer is connected to the working electrode of the electrochemical electrode array through through-silicon vias to form a conductive path. The nanoporous enrichment layer and the micro air pump assembly are sealed with 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 through photolithography and are vertically interconnected with the through-silicon vias of the MEMS silicon substrate; the signal output terminals of the working electrode, reference electrode, and counter electrode are bonded to a potentiostat circuit through gold wire bonding to realize current-to-voltage signal conversion. The micro air pump assembly includes a micro air pump, the air inlet of which is equipped with a primary filter, and the outlet is directly connected to the microchannel 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 deposited 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 an external PCB via gold wire bonding for transmitting 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 a 45° angle to the airflow direction to increase the probability of protein collision and adsorption; the edge of the nanoporous enrichment layer is provided with a flow guide groove to guide the airflow to uniformly cover the entire porous area.

4. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 3, characterized in that, 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, characterized in that, The working electrode is fabricated by depositing a 300nm gold layer on the MEMS silicon substrate using electron beam evaporation, followed by electrochemical etching 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, 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 its surface is electrochemically polished to reduce background current noise.

6. The electrochemical air protein concentration detection device based on nanoporous MEMS according to claim 1, characterized in that, The micro air pump assembly uses a piezoelectric ceramic micro pump and has multiple air passages arranged in a ring.

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

8. A method for detecting air protein concentration using the device described in claim 3, characterized in that, Includes the following steps: Step 1, System Initialization and Parameter Calibration, includes: Hardware self-test: The miniature air pump is started and idled for 30 seconds to check if the flow rate is stable at 0.5L / min ± 3%. The potentiostat circuit verifies the baseline current of the three electrodes. If the dark current is >10nA, an electrode contamination alarm is triggered. Parameter loading: Read the pre-stored calibration parameters from the EEPROM, including: Electrode response coefficient K: calibrated using BSA standard solution, range 0.8–1.2 μA·cm. 2 ·s / μg; Temperature and humidity compensation coefficients: Temperature coefficient a = -0.0002 / ℃, 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, includes: Airflow control: A miniature air pump draws air at a flow rate of 0.5 L / min. After passing through a pre-filter to remove particles >1 μm, the air enters the nanoporous enrichment layer through 45° inclined airflow holes. The adsorption time t is adaptively adjusted for particles <1 μg / m². 3 Low concentration scenario: t = 300 seconds; particles ≥ 1 μg / m³ 3 Medium to high concentration scenarios: t = 60 seconds; Proteins are adsorbed by amino-modified nanoporous enrichment layers through diffusion and inertial collisions, while small molecule pollutants are discharged with the airflow. Enrichment efficiency model: Among them, V pore V is the volume of the porous layer. air =Q·t is the sampling volume, Q = 0.5 L / min; Step 3, detection of electrochemical oxidation reaction, including: Setting parameters for differential pulse voltammetry: Scanning voltage range: +0.4V to +0.8V; Step voltage: 10mV, pulse amplitude: 50mV, pulse width: 50ms; Sampling frequency: 100Hz, 10 samples are collected for each voltage point and the average value is taken; Signal acquisition: The protein residues on the working electrode undergo oxidation, generating a characteristic peak current I. peak Typical peak potential +0.6V; The current signal is converted into a voltage signal by a potentiostat circuit, and then transmitted to the MCU after being sampled by a 12-bit ADC. Step 4, signal processing and error compensation, includes: Baseline correction: Baseline current I was calculated using the 5-minute moving average method. base After removing background noise, I corrected =I peak -I base ; Temperature and humidity compensation: Temperature compensation: I T =I corrected ×(1+a·(T-25℃)+b·(T-25℃) 2 ); Humidity compensation: Corrects adsorption efficiency based on the RH value from the built-in humidity sensor. or RH =η×(1+0.0005·(RH-50%)); Preliminary concentration calculation: Where A = 0.09cm 2 The effective area of ​​the working electrode; Step 5, self-cleaning triggering and execution, includes: The system will start if any of the following conditions are met: Condition 1: Current detection signal I T If the attenuation from the initial value is greater than 15%, the judgment formula is: Condition 2: Cumulative working time > 24 hours; Dual-mode cleaning process: Electrochemical cleaning: Applying a reverse voltage of -1.2V causes the disulfide bonds between protein molecules to break, with a desorption rate of >80%; Pyrolysis cleaning: The Pt resistance heater heats the temperature to 250±5℃ to carbonize the residual protein, and after natural cooling, it is returned to the detection cycle; Step 6, concentration calculation and result output, including: Range calibration: If C'>1000μg / m 3 It automatically switches to high-gain mode to avoid signal saturation; Final concentration formula: Unit conversion: V air =Q·t, where the unit is L, and the concentration unit is μg / m³. 3 ; Data output: The concentration value is transmitted to external devices, including the air purifier's main control MCU, via the UART protocol; Store the current detection data to the on-chip Flash.

Images