CN-121988250-A - Carbon quantum dot hydrothermal synthesis system and method based on microfluidic thermal field balance

CN121988250ACN 121988250 ACN121988250 ACN 121988250ACN-121988250-A

Abstract

The invention relates to the technical field of microfluidics, in particular to a carbon quantum dot hydrothermal synthesis system and method based on microfluidic thermal field equalization, comprising a thermal field sensing module, an equalization analysis module, a thermal field coupling module, an equalization regulation and control module and a closed loop execution module, wherein the thermal field sensing module is used for acquiring array temperature of the surface of a microfluidic chip and fluid pressure data in a flow channel, and reconstructing three-dimensional temperature distribution in a micro channel through a multi-physical field coupling algorithm to obtain a real-time thermal field state matrix. According to the invention, by constructing a multi-physical field coupling algorithm of the thermocouple array-flow resistance model-conjugate heat transfer equation, the three-dimensional temperature distribution of fluid in the micro-channel can be reconstructed by inversion by utilizing surface temperature and pressure data, so that a control system can directly sense radial temperature gradient and axial heat distortion in the fluid through a chip matrix, hysteresis and error of sensor measurement are eliminated, and a real physical basis is provided for accurate temperature control.

Inventors

WANG RUI
CHEN HUIPING
DU JINFENG
CUI QIUSHENG
Yue Ruicheng
CHEN TAO

Assignees

海南科技职业大学

Dates

Publication Date: 20260508
Application Date: 20260304

Claims (9)

1. The carbon quantum dot hydrothermal synthesis system based on micro-fluidic thermal field equalization is characterized by comprising the following components: The thermal field sensing module is used for acquiring array temperature of the surface of the microfluidic chip and fluid pressure data in the flow channel, reconstructing three-dimensional temperature distribution in the micro channel through a multi-physical field coupling algorithm, and obtaining a real-time thermal field state matrix; The equilibrium analysis module is used for carrying out gradient discrete calculation on the real-time thermal field state matrix, identifying a local thermal distortion area and extracting thermal field gradient deviation vectors representing thermal field spatial uniformity; the thermal field coupling module is used for acquiring online fluorescence spectrum data of a product at the microfluidic outlet, establishing a mapping relation between the fluorescence spectrum data and the thermal field gradient deviation vector, and resolving a reaction kinetic response index; The balance regulation and control module is used for carrying out weighted correction on the thermal field gradient deviation vector according to the reaction kinetic response index to generate power compensation strategies and fluid pulsation flow rate regulation and control schemes aiming at different heating partitions of the microfluidic chip; The closed loop execution module is used for driving the array heating unit and the micro-fluid pump group according to the power compensation strategy and the fluid pulsation flow rate regulation scheme, eliminating thermal field distortion, feeding regulated thermal field data back to the thermal field sensing module, and realizing thermal field dynamic balance in the carbon quantum dot synthesis process.
2. The carbon quantum dot hydrothermal synthesis system based on micro-fluidic thermal field equalization of claim 1, wherein the method for acquiring array temperature of the surface of the micro-fluidic chip and fluid pressure data in the flow channel, reconstructing three-dimensional temperature distribution in the micro-channel by a multi-physical field coupling algorithm to obtain a real-time thermal field state matrix comprises the following steps: acquiring voltage signals fed back by a thermocouple array distributed on the heating surface of the microfluidic chip and pressure difference signals of an inlet and an outlet of the flow channel, and respectively analyzing to obtain chip surface array temperature and flow channel fluid pressure data after analog-to-digital conversion and calibration; inputting the flow channel fluid pressure data into a micro-channel flow resistance model, and calculating laminar flow velocity distribution in a micro-channel by combining the geometric topological feature of the flow channel of the micro-fluidic chip to generate a flow velocity vector field in the channel; taking the chip surface array temperature as a thermal boundary condition of a solid-liquid interface, taking the flow velocity vector field in the channel as a convection heat transfer item to be input, deducing a heat transfer path of a fluid center by using a conjugate heat transfer equation, and calculating to obtain a three-dimensional fluid temperature field in the micro channel; performing voxel grid discretization on the three-dimensional fluid temperature field in the micro-channel, extracting a temperature value of the center of each voxel grid, and constructing a three-dimensional voxel temperature dataset; And tensor recombination is carried out on the three-dimensional voxel temperature data set according to the space extending direction of the microfluidic flow channel, so that a real-time thermal field state matrix containing the fluid flow direction and the section thermal gradient is generated.
3. The microfluidic thermal field equalization-based carbon quantum dot hydrothermal synthesis system according to claim 2, wherein the chip surface array temperature is used as a thermal boundary condition of a solid-liquid interface, the in-channel flow velocity vector field is used as a convective heat transfer item to be input, a heat transfer path of a fluid center is deduced by using a conjugate heat transfer equation, and a three-dimensional fluid temperature field inside a microchannel is obtained by calculation, and the method comprises the following steps: extracting the matrix heat conductivity coefficient and the physical thickness of the microfluidic chip, performing solid-state heat conduction attenuation calculation on the array temperature on the surface of the chip, and carrying out normal mapping correction on the surface temperature of the chip to obtain the interface temperature data of the inner wall of the flow channel; Extracting a flow velocity vector field in the channel, calculating the local Reynolds number of the fluid micro-element, matching the Knoop number, calculating the thermal resistance characteristics of the fluid boundary layer at each position of the flow channel, and generating a local convective heat transfer coefficient matrix; Coupling the temperature data of the interface of the inner wall of the runner with the local convection heat transfer coefficient matrix, and calculating the real-time temperature difference and the heat exchange rate of the solid-liquid interface to obtain heat flux data of the solid-liquid interface; And taking the solid-liquid interface heat flux data as a boundary energy source item, carrying out discrete solution on a fluid energy conservation equation by combining the convection transportation effect of the flow velocity vector field in the channel, and calculating the enthalpy change of fluid infinitesimal to obtain the three-dimensional fluid temperature field in the microchannel.
4. The microfluidic thermal field equalization-based carbon quantum dot hydrothermal synthesis system according to claim 3, wherein the solid-liquid interface thermal flux data is used as a boundary energy source item, the convective transport function of the flow velocity vector field in the channel is combined, the discrete solution is performed on a fluid energy conservation equation, the change of enthalpy values of fluid microelements is calculated, and a three-dimensional fluid temperature field in the microchannel is obtained, and the method comprises the following steps: Dividing a fluid calculation domain into a plurality of fluid control body units which are not overlapped with each other according to the geometric boundary of the microfluidic flow channel, and extracting grid node coordinates of each control body unit; mapping the flow velocity vector field in the channel to an interface of the fluid control body unit, calculating mass exchange rate between adjacent control body units, and generating an inter-grid convection transfer matrix; identifying boundary nodes positioned on the inner wall of the runner according to the grid node coordinates, distributing the solid-liquid interface heat flux data to the corresponding boundary nodes, and generating boundary node heat source vectors; Constructing a discretization energy conservation equation set comprising the inter-grid convection transfer matrix and the boundary node heat source vector, and solving the equation set by adopting an iterative algorithm to obtain a converged temperature value of each grid node; And continuously reconstructing the temperature values of the grid nodes by using a spatial interpolation algorithm to obtain a three-dimensional fluid temperature field in the micro-channel covering the full flow channel.
5. The microfluidic thermal field equalization-based carbon quantum dot hydrothermal synthesis system according to claim 2, wherein performing gradient discrete calculation on the real-time thermal field state matrix, identifying a local thermal distortion region, extracting a thermal field gradient deviation vector representing thermal field spatial uniformity, comprises: performing differential operation on the real-time thermal field state matrix along the axial direction and the radial direction of the micro-channel, calculating the temperature change rate of the fluid in the flowing direction and the cross section direction, and constructing a global thermal gradient tensor; calculating an arithmetic average value of all elements in the global thermal gradient tensor, setting the arithmetic average value as a thermal field gradient reference value, and setting a non-uniformity tolerance threshold according to standard deviation of tensor elements; Calculating absolute deviation values of all elements in the global thermal gradient tensor and the thermal field gradient reference value, screening out elements with the absolute deviation values larger than the non-uniformity tolerance threshold, and marking the elements as thermal distortion characteristic points; Generating a plurality of local heat distortion areas by adopting a spatial density clustering algorithm according to the three-dimensional coordinates of the heat distortion characteristic points in the micro-channel, and calculating the difference value between the average temperature gradient in each area and the thermal field gradient reference value to obtain an area distortion intensity value; And performing associated coding on the spatial position coordinates of the local heat distortion region and the corresponding region distortion intensity value to generate a thermal field gradient deviation vector containing a position index and intensity weight.
6. The microfluidic thermal field equalization-based carbon quantum dot hydrothermal synthesis system according to claim 5, wherein generating a plurality of local thermal distortion areas by adopting a spatial density clustering algorithm according to the three-dimensional coordinates of the thermal distortion feature points in the micro-channel comprises: Calculating Euclidean distances among all the heat distortion characteristic points, and constructing a characteristic point distance matrix; Setting a cluster searching radius and a minimum neighborhood point threshold value, traversing the characteristic point distance matrix, counting the number of neighbors of each characteristic point in the searching radius, and marking the points with the number exceeding the minimum neighborhood point threshold value as density core points; Merging the density core points of the shared neighborhood and boundary points in the neighborhood thereof according to the connectivity of the density core points to generate a plurality of independent disjoint distortion point sets; Extracting three-dimensional coordinate extremum of all points in each independent distortion point set, and constructing a minimum circumscribed cuboid enveloping the point set as a space boundary of the region; Calculating the arithmetic mean value of the coordinates of all points in the independent distortion point set to obtain the geometric centroid coordinates of the area; and combining the minimum circumscribed cuboid with the geometric centroid coordinate to define a local heat distortion area.
7. The microfluidic thermal field equalization-based carbon quantum dot hydrothermal synthesis system according to claim 1, wherein obtaining product online fluorescence spectrum data at a microfluidic outlet, establishing a mapping relationship between the fluorescence spectrum data and the thermal field gradient deviation vector, and calculating a reaction kinetic response index, comprises: Performing peak optimization and integral calculation on the collected online fluorescence spectrum data, extracting the center wavelength of an emission peak of the carbon quantum dot and the fluorescence integral intensity, and combining the center wavelength and the fluorescence integral intensity into a current product quality feature vector; Acquiring real-time fluid flow velocity data of a microfluidic system, calculating an equivalent average flow velocity through time domain integration, calculating hydraulic retention time of fluid passing through a heating area by combining the effective volume of a flow channel, and extracting a historical thermal field gradient deviation vector corresponding to time lag existing at the current moment from a preset data storage unit according to the hydraulic retention time; calculating Euclidean distance between the current product quality feature vector and a preset standard product spectrum feature to obtain a spectrum quality deviation value representing the deviation degree of the synthetic quality; calculating the modular length of the gradient deviation vector of the historical thermal field to obtain a thermal field unbalanced intensity value; And establishing a ratio relation between the spectrum quality deviation value and the unbalanced intensity value of the thermal field, introducing symbol correction by combining the drift direction of the central wavelength of the emission peak, and calculating to obtain a response dynamic response index for representing the sensitivity of the reaction to thermal field distortion.
8. The microfluidic thermal field equalization-based carbon quantum dot hydrothermal synthesis system according to claim 1, wherein the thermal field gradient deviation vector is subjected to weighted correction according to the reaction kinetic response index to generate power compensation strategies and fluid pulsation flow rate regulation schemes for different heating partitions of a microfluidic chip, and the method comprises the following steps: Using the response index of the reaction kinetics as a self-adaptive gain coefficient, performing scalar multiplication operation on the area distortion intensity value contained in the thermal field gradient deviation vector, and amplifying or attenuating the amplitude of a thermal distortion signal to obtain a dynamics weighted thermal distortion vector showing the reaction sensitivity; Invoking a preset heating array-runner space mapping matrix, mapping a position index in the dynamic weighted heat distortion vector to a physical heating partition corresponding to the microfluidic chip, and calculating compensatory heat flux required by each partition for eliminating the thermal gradient according to the weighted intensity value to generate a partition power compensation instruction; And calculating the integral modular length of the dynamic weighted thermal distortion vector, inputting the integral modular length into a pulsation flow control model, solving pulsation frequency and amplitude parameters for enhancing radial mixing of fluid through nonlinear mapping, and constructing a fluid pulsation flow velocity regulation scheme comprising waveform time sequence definition.
9. The carbon quantum dot hydrothermal synthesis method based on micro-fluidic thermal field equalization, which is applicable to the carbon quantum dot hydrothermal synthesis system based on micro-fluidic thermal field equalization as claimed in any one of claims 1 to 8, is characterized by comprising the following steps: S1, acquiring array temperature of the surface of a microfluidic chip and fluid pressure data in a flow channel, and reconstructing three-dimensional temperature distribution in a micro channel through a multi-physical field coupling algorithm to obtain a real-time thermal field state matrix; S2, carrying out gradient discrete calculation on the real-time thermal field state matrix, identifying a local thermal distortion area, and extracting a thermal field gradient deviation vector representing thermal field spatial uniformity; s3, acquiring online fluorescence spectrum data of a product at a microfluidic outlet, establishing a mapping relation between the fluorescence spectrum data and the thermal field gradient deviation vector, and calculating a reaction kinetic response index; s4, carrying out weighted correction on the thermal field gradient deviation vector according to the reaction dynamics response index to generate power compensation strategies and fluid pulsation flow rate regulation schemes aiming at different heating areas of the microfluidic chip; And S5, driving the array heating unit and the micro-fluid pump set according to the power compensation strategy and the fluid pulsation flow rate regulation scheme to eliminate thermal field distortion, and feeding regulated thermal field data back to the step S1 to realize thermal field dynamic balance in the carbon quantum dot synthesis process.

Description

Carbon quantum dot hydrothermal synthesis system and method based on microfluidic thermal field balance Technical Field The invention relates to the technical field of microfluidics, in particular to a carbon quantum dot hydrothermal synthesis system and method based on microfluidic thermal field equalization. Background The carbon quantum dot is used as a novel zero-dimensional carbon nano material, has huge application potential in the fields of biological imaging, photocatalysis, sensing detection, photoelectric devices and the like due to excellent fluorescence performance, good biocompatibility and low toxicity, and at present, the preparation method of the carbon quantum dot mainly comprises an arc discharge method, a laser pin etching method, a microwave digestion method and a hydrothermal/solvothermal method, wherein the hydrothermal synthesis method is a main stream method for preparing the carbon quantum dot at present due to simple equipment, wide sources of reaction precursors and easy surface functionalization. In recent years, a microfluidic technology is introduced into the synthesis of carbon quantum dots, and the microfluidic synthesis can remarkably improve the heat and mass transfer efficiency by utilizing the extremely large specific surface area of a microchannel and precise fluid control, so that continuous production is realized. However, in the actual microfluidic hydrothermal synthesis process, a plurality of unresolved key technical problems still exist, and stable preparation of high-quality carbon quantum dots is limited. The existing microfluidic synthesis system is mostly dependent on a sensor on the surface of a chip for temperature monitoring, and the surface temperature is often delayed and deviates from the actual fluid temperature in a flow channel due to the existence of matrix thermal resistance and fluid convection. Meanwhile, the typical laminar flow characteristic of microfluid causes radial mixing difficulty, obvious temperature gradient is easy to form on the flow channel section, the prior art cannot reconstruct and sense the internal three-dimensional thermal field distribution in real time, so that the control system cannot sense local overheating or supercooling in the fluid in time, and the consistent growth of crystal nucleus is difficult to ensure. Disclosure of Invention In order to achieve the purpose, the invention provides the following technical scheme that the carbon quantum dot hydrothermal synthesis system based on micro-fluidic thermal field equalization comprises: The thermal field sensing module is used for acquiring array temperature of the surface of the microfluidic chip and fluid pressure data in the flow channel, reconstructing three-dimensional temperature distribution in the micro channel through a multi-physical field coupling algorithm, and obtaining a real-time thermal field state matrix; The equilibrium analysis module is used for carrying out gradient discrete calculation on the real-time thermal field state matrix, identifying a local thermal distortion area and extracting thermal field gradient deviation vectors representing thermal field spatial uniformity; the thermal field coupling module is used for acquiring online fluorescence spectrum data of a product at the microfluidic outlet, establishing a mapping relation between the fluorescence spectrum data and the thermal field gradient deviation vector, and resolving a reaction kinetic response index; The balance regulation and control module is used for carrying out weighted correction on the thermal field gradient deviation vector according to the reaction kinetic response index to generate power compensation strategies and fluid pulsation flow rate regulation and control schemes aiming at different heating partitions of the microfluidic chip; The closed loop execution module is used for driving the array heating unit and the micro-fluid pump group according to the power compensation strategy and the fluid pulsation flow rate regulation scheme, eliminating thermal field distortion, feeding regulated thermal field data back to the thermal field sensing module, and realizing thermal field dynamic balance in the carbon quantum dot synthesis process. Preferably, the method for acquiring array temperature of the surface of a microfluidic chip and fluid pressure data in a flow channel, reconstructing three-dimensional temperature distribution in a micro channel through a multi-physical field coupling algorithm to obtain a real-time thermal field state matrix comprises the following steps: acquiring voltage signals fed back by a thermocouple array distributed on the heating surface of the microfluidic chip and pressure difference signals of an inlet and an outlet of the flow channel, and respectively analyzing to obtain chip surface array temperature and flow channel fluid pressure data after analog-to-digital conversion and calibration; inputting the flow channel fluid pressure data into