An aerosol single droplet optical tweezers detection device and method based on LED light source

Abstract

The present invention relates to an aerosol single droplet optical tweezers detection device and method based on LED light source, belonging to the field of optical capture and particle detection technology, and solving the problems of high cost and high energy consumption of the light source used in the existing optical tweezers technology, and large stray signal interference in signal detection. The optical coupling system includes an LED light source module, a collimating lens, a beam shaping component, a focusing lens component and a semi-transparent and semi-reflective mirror component arranged in sequence. The optical tweezers detection system includes the above-mentioned beam coupling system, as well as a single droplet suspension system, a gas atmosphere control system, a droplet pumping system, a signal detection system and a droplet detection device.

Description

Technical Field

[0001] The present invention relates to the technical field of optical capture and particle detection, and in particular to an aerosol single droplet optical tweezers detection device and method based on an LED light source. Background Art

[0002] Optical trapping technology for aerosol particles has a wide range of applications in biological, environmental, and chemical research. Optical tweezers rely on the gradient force and scattering force of optical traps to manipulate tiny particles, achieving contactless and precise manipulation. Existing optical tweezers devices usually rely on high light intensity and collimated beams generated by laser light sources to provide sufficient light trap gradient force and scattering force to capture and suspend particles. However, the high cost, high power consumption, and single wavelength of laser light sources have limitations in certain applications, especially in application scenarios that require high economy and light source controllability, laser light sources cannot fully meet the needs.

[0003] In recent years, LED light sources have gradually emerged in the field of optical manipulation due to their advantages such as low cost, wide spectral range, and adjustable power. However, LED light sources have a large divergence angle and a lower power density than lasers, and do not have sufficient optical gradient force, which limits their application in optical tweezers technology. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide an aerosol single droplet optical tweezers detection device and method based on LED light source, which can solve at least one of the following technical problems: (1) The existing optical tweezers technology uses a laser light source, which leads to high cost and high energy consumption; (2) The existing optical tweezers technology has large stray signal interference in signal detection, which affects the stable capture and accurate detection of single droplets.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides an optical coupling system for improving the optical gradient force of an LED light source, comprising an LED light source module, a collimating lens, a beam shaping component, a focusing lens component and a semi-transparent and semi-reflective mirror component arranged in sequence;

[0007] The LED light source module is used to provide light for detection; the collimating lens is used to collimate the light beam emitted by the LED light source module to reduce the divergence angle; the beam shaping component is used to uniform the light intensity distribution of the collimated light and optimize the shape of the light beam to obtain a high-quality parallel light beam; the focusing lens component is used to expand the high-quality parallel light beam; the semi-transparent and semi-reflective mirror component is used to split the expanded light beam.

[0008] Optionally, the beam shaping component is a microlens array or an aspherical lens.

[0009] Optionally, the beam shaping component is an axicon component.

[0010] Optionally, the focusing lens assembly includes two focusing lenses arranged opposite to each other.

[0011] Optionally, the semi-transparent and semi-reflective mirror assembly includes two semi-transparent and semi-reflective mirrors arranged opposite to each other and in parallel.

[0012] In a second aspect, the present invention provides an aerosol single droplet optical tweezers detection system based on an LED light source, comprising the above-mentioned beam coupling system, as well as a single droplet suspension system, a gas atmosphere control system, a droplet pumping system, a signal detection system and a droplet detection device;

[0013] The gas atmosphere control system is connected to the single droplet suspension system, the droplet pumping system is connected to the single droplet suspension system, and the beam coupling system is connected to the single droplet suspension system, the signal detection system and the droplet detection device respectively.

[0014] Optionally, the single droplet suspension system comprises a sample pool, the sample pool comprises a concentric outer annular wall and an inner annular wall, and a connecting portion is provided between the outer annular wall and the inner annular wall.

[0015] Optionally, the gas atmosphere control system includes a dry gas control device and a wet gas control device; the dry gas control device and the wet gas control device both include a gas storage tank and a flow meter.

[0016] Optionally, the wet gas control device also includes a humidifying container.

[0017] In a third aspect, the present invention further provides an aerosol single droplet optical tweezers detection method based on an LED light source, which is completed using the above-mentioned detection system and includes the following steps:

[0018] Step 1: The droplet pumping system pumps the aerosol into the sample pool of the single droplet suspension system in the form of a single droplet;

[0019] Step 2: The LED light emitted by the beam coupling system is used as the reaction beam to capture a single droplet in the sample pool and suspend it using the optical tweezers technique;

[0020] Step 3: introducing gas into the sample cell through a gas atmosphere control system;

[0021] Step 4: The scattered light signal of the single droplet is input into the signal detection system and the droplet detection device respectively, and the change in the radius of the single droplet before and after the single droplet reaction is analyzed based on the light signal data.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] 1. The present invention can improve the optical gradient force of the LED light source by setting up an optical coupling system, so that the LED light source can be used as a light source in the optical tweezers technology to grab micro droplets. Since the resonance peak signal generated by the LED light source through stimulated elastic scattering has a higher signal-to-noise ratio and less stray signals than the stimulated Raman scattering signal of the laser light source, the accuracy and sensitivity of the detection can be significantly improved.

[0024] 2. The LED light source of the present invention is low-cost and low-power, which reduces the overall cost of the device and the interference of heat output on the experimental environment, thereby improving the economy and operational stability of the equipment. In addition, the LED light source provides multiple wavelength options from 365 nm to 650 nm, and the wavelength can be flexibly adjusted according to the different scattering characteristics of aerosol particles, so that the device can achieve multi-wavelength testing in a single system, which is particularly suitable for diversified environmental monitoring and biological particle detection. The LED light source module adopts a modular design, which is convenient for the maintenance of the light source and the replacement of LED light sources of different power and wavelength, extending the service life of the device, and can be quickly configured under different experimental requirements, enhancing the adaptability of the equipment. In addition, the small size and low energy consumption of the LED light source enable the device of the present invention to be designed as a portable device, expanding the scope of application, and can be applied to field detection applications outside the laboratory to meet the actual environmental monitoring and rapid response requirements.

[0025] 3. The sample pool of the present invention comprises an outer ring wall and an inner ring wall, a single droplet inlet penetrating the outer ring wall and the inner ring wall is arranged at the connection of the outer ring wall and the inner ring wall, a plurality of gas inlets and gas outlets penetrating the ring wall and arranged at intervals are arranged on the outer ring wall and the inner ring wall, the gas inlet and gas outlet on the outer ring wall are staggered with the gas inlet and gas outlet on the inner ring wall, this structure can make the gas enter and discharge the sample pool uniformly, and ensure the stability of the air pressure in the sample pool, so as to make the optical tweezers stably suspend the single droplet; in addition, the uniform entry and discharge of gas into the sample pool can avoid excessively high or low local air pressure, reduce the uneven distribution of droplets when entering the sample pool due to uneven air pressure, and effectively solve the problem that uneven air pressure may cause droplets to deposit on the wall of the device; moreover, the stable air pressure in the sample pool helps to maintain the suspension state of the single droplet and reduce the contact between the droplet and the wall caused by air pressure fluctuations;

[0026] The diameter of the gas inlet and the diameter of the gas outlet are both smaller than the diameter of the single droplet inlet. When a single droplet is pumped into the sample pool from the single droplet inlet, the turbulence effect of the aerosol droplets in the sample pool can be generated and enhanced. The turbulence can enhance the mixing and movement of the droplets in the sample pool and reduce the probability and possibility of the droplets depositing on the inner wall. The rapid and swirling airflow does not simply go from the inlet to the outlet, but approaches the center of the sample pool (i.e., the focusing center of the LED light) by means of turbulence. At the same time, the swirling effect can also increase the probability of the airflow outside the focusing center returning to the focus, thereby increasing its capture efficiency and reducing the probability of aerosol droplets depositing on the inner wall of the sample pool.

[0027] 4. A quartz glass sheet coated with an anionic surfactant is disposed at the bottom of the sample pool of the present invention. The anionic surfactant reduces the surface tension of the spherical droplets and causes the droplets at the bottom of the sample pool to no longer be deposited in a spherical form, but to spread directly on the bottom of the sample pool, thereby avoiding measurement errors caused by the curved surface pressure brought about by the curved surface structure of the droplets containing volatile chemical components at the bottom of the sample pool.

[0028] 5. The present invention provides a droplet beam device in the droplet pumping system. When the aerosol droplets pass through the droplet beam device, the droplet beam device changes the droplets from an aggregated state into a monodisperse single string of droplets that enter the sample pool one by one.

[0029] 6. A stop valve is arranged between the aerosol generator and the droplet beam device of the present invention. When the droplets enter the droplet beam device, the stop valve can be closed and the environmental background gas can be introduced into the droplet beam device to dilute the droplets in the droplet beam device, thereby further promoting the droplet beam device to change the droplets from an aggregated state into a monodisperse single string of droplets that enter the sample pool one by one.

[0030] 7. In the method of the present invention, after the single droplet is suspended by the optical tweezers technique, dry gas and / or wet gas is introduced into the sample pool through the gas atmosphere control system to reduce the humidity in the sample pool to below the weathering point humidity of the chemical components in the droplet, so that the droplets on the inner wall of the sample pool are weathered and crystallized, and then the humidity in the sample pool is adjusted to the humidity required for the reaction. During the weathering and crystallization process, the volatile components in the droplets deposited on the wall have volatilized. When the ambient humidity rises to the reaction humidity, the crystals on the wall adsorb water molecules in the environment to form a solid-liquid mixture. The liquid phase in the solid-liquid mixture is only the adsorbed water molecules, and no longer has the volatile organic components in the aerosol droplets. In this process, the volatile components in the single droplet suspended by the optical tweezers remain unchanged, thereby effectively avoiding the influence of the volatile components in the droplets deposited on the wall on the measurement of the single droplet suspended by the optical tweezers.

[0031] 8. The device and method of the present invention are applicable to a variety of aerosol and particle experiments, and are particularly applicable to particle manipulation in environmental monitoring and biological research, providing a more flexible and economical solution for the application of optical capture technology.

[0032] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description or be understood by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0034] Figure 1 The aerosol single droplet optical tweezers detection device based on LED light source of the present invention;

[0035] Figure 2 It is a schematic diagram of the sample pool structure of the present invention;

[0036] FIG3 (a) is a structural discrete diagram of the droplet beam device of the present invention;

[0037] FIG3( b ) shows apertures of different diameters according to the present invention;

[0038] Figure 3 (c) shows washers of different diameters according to the present invention;

[0039] Figure 4 is a cross-sectional view of the droplet beam device of the present invention;

[0040] Figure 5 It is a schematic diagram of the monodisperse action principle of the droplet beam device of the present invention;

[0041] Figure 6 A spectrum showing the change of the resonance peak position over time obtained by using the detection device (LED light source grasping and measuring) of the present invention to detect a single droplet using the optical tweezers technique;

[0042] Figure 7 A spectrum showing the change of the resonance peak position over time obtained by using the existing detection device (laser light source grabbing and measuring) to detect a single droplet using the optical tweezers technique;

[0043] Figure 8 is a schematic diagram of a light beam passing through a microlens array;

[0044] Fig. 9 Schematic diagram of a light beam passing through an axicon component.

[0045] Reference numerals:

[0046] 1- single droplet suspension system; 101- sample pool; 102- illumination light source; 1021- outer ring wall; 1022- inner ring wall; 1023- single droplet inlet; 1024- gas inlet; 1025- gas outlet; 2- gas atmosphere control system; 201- gas storage tank; 202- flow meter; 203- humidification container; 3- droplet pumping system; 301- aerosol generator; 3031- pipeline; 3032- aperture; 3033- gasket; 3034- clamp; 3035- threaded cover; 4- beam coupling system; 401- LED light source; 402- focusing lens; 403- semi-transparent and semi-reflective mirror; 404- total reflection mirror; 405- collimating lens; 406- beam shaping component; 407- microscope objective lens; 5- signal detection system; 501- optical imaging camera; 502- spectrometer; 503- data processing unit; 6- droplet detection device. DETAILED DESCRIPTION

[0047] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0048] The inventors found in their research that existing aerosol single droplet detection devices usually rely on laser light sources, but laser light sources have some significant limitations. First, laser light sources are expensive and consume a lot of power, which makes the overall cost and energy efficiency of the device poor, limiting its application in low-cost, low-power and compact designs.

[0049] In addition, the signal generated by the laser light source is easily interfered by stray light, resulting in poor signal quality. The narrow spectrum bandwidth of the laser makes its stimulated Raman scattering signal weaker and the signal-to-noise ratio lower, which affects the accurate detection of aerosol particles. The high energy output of the laser light source will also increase the interference of scattered light, resulting in an increase in stray signals, further reducing the clarity and reliability of the signal.

[0050] In contrast, LED light sources have the advantages of low cost, wide spectral range, adjustable power, low power consumption, etc., and the resonance peak signal generated by stimulated elastic scattering has a higher signal-to-noise ratio and fewer stray signals than the stimulated Raman scattering signal of the laser light source, which can significantly improve the accuracy and sensitivity of detection. However, the divergence angle of LED light sources is large, and the power density is relatively low compared to lasers, and there is no sufficient optical gradient force, which makes it impossible to use LED light sources to capture and suspend particles in optical tweezers technology.

[0051] The present invention develops an aerosol single droplet optical tweezers detection device based on LED light source. By optimizing the optical system structure, the LED light source is equipped with sufficient optical gradient force to realize the capture and detection of aerosol particles, providing a more flexible and economical solution for the application of optical tweezers technology.

[0052] In a first aspect, the present invention provides an aerosol single droplet optical tweezers detection device based on an LED light source, such as Figure 1 As shown, the device includes a single droplet suspension system 1, a gas atmosphere control system 2, a droplet pumping system 3, a beam coupling system 4, a signal detection system 5 and a droplet detection device 6.

[0053] Among them, the gas atmosphere control system 2 is connected to the single droplet suspension system 1, the droplet pumping system 3 is connected to the single droplet suspension system 1, and the beam coupling system 4 is connected to the single droplet optical tweezers suspension system 1, the signal detection system 5 and the droplet detection device 6 respectively.

[0054] During implementation, the droplet pumping system 3 pumps the aerosol into the sample pool 101 of the single droplet suspension system 1 in the form of a single droplet; the LED light emitted by the beam coupling system 4 is used as a reaction beam to capture a single droplet in the sample pool 101 and suspend it through the optical tweezers technology; the required gas is introduced into the sample pool 101 through the gas atmosphere control system 2; the scattered light signal of the single droplet is respectively input into the signal detection system 5 and the droplet detection device 6, and the change in the single droplet radius value before and after the single droplet reaction is analyzed based on the optical signal data.

[0055] The single droplet suspension system 1 comprises a sample pool 101, such as Figure 2 As shown, the sample pool 101 includes a concentric outer annular wall 1021 and an inner annular wall 1022, and a connecting portion is provided between the outer annular wall 1021 and the inner annular wall 1022, and the connecting portion is used to connect partial side walls of the outer annular wall 1021 and the inner annular wall 1022, and a single droplet inlet 1023 penetrating the outer annular wall 1021 and the inner annular wall 1022 is provided on the connecting portion; the outer annular wall 1021 and the inner annular wall 1022 are each provided with a plurality of gas inlets 1024 and gas outlets 1025 penetrating the annular walls and arranged at intervals, and the gas inlet 1024 and gas outlet 1025 on the outer annular wall 1021 are staggered with the gas inlet 1024 and gas outlet 1025 on the inner annular wall 1022.

[0056] Specifically, the single droplet inlet 1023 , the gas inlet 1024 and the gas outlet 1025 are all arranged radially. Moreover, the diameters of the gas inlet 1024 and the gas outlet 1025 are both smaller than the diameter of the single droplet inlet 1023 , and the diameter of the gas inlet 1024 is smaller than the diameter of the gas outlet 1025 .

[0057] Exemplarily, the diameter of the single droplet inlet 1023 is 3-4 times the diameter of the gas inlet 1024, and the diameter of the single droplet inlet 1023 is 2-2.5 times the diameter of the gas outlet 1025. For example, the diameter of the single droplet inlet 1023 is 3 mm, the diameter of the gas inlet 1024 is 1.0 mm, and the diameter of the gas outlet 1025 is 1.5 mm.

[0058] It should be noted that the outer annular wall 1021 is coaxially arranged with the inner annular wall 1022 and shares a bottom surface with the sample pool. In addition, the distance between the outer annular wall 1021 and the inner annular wall 1022 is 2-3 mm.

[0059] Exemplarily, the distance between the outer annular wall 1021 and the inner annular wall 1022 is 2-3 mm.

[0060] In a preferred embodiment, a quartz glass sheet (not shown) is disposed at the bottom of the sample pool 101, and an anionic surfactant layer is disposed on the quartz glass sheet. The anionic surfactant reduces the surface tension of the spherical droplets, and makes the droplets at the bottom of the sample pool no longer deposit in a spherical form, but directly spread on the bottom of the sample pool, thereby avoiding the measurement error caused by the curved surface pressure caused by the curved surface structure of the droplets containing volatile chemical components at the bottom of the sample pool.

[0061] Exemplarily, the anionic surfactant layer has a thickness of 0.1-0.2 mm.

[0062] Exemplarily, the anionic surfactant is sodium fatty alcohol ether sulfate and / or sodium dodecyl sulfate.

[0063] It should be noted that the droplets deposited on the inner wall of the sample pool cannot be solved directly by applying anionic surfactants. This is because, in addition to the single droplet inlet 1023, the structure of the sample pool 101 of the present invention also has a gas inlet 1024 and a gas outlet 1025. If the anionic surfactant is applied to the inner wall surface, when the humidity in the sample pool 101 increases, water molecules and the anionic surfactant will be emulsified on the inner wall of the sample pool 101 to produce foam, which may cause pore blockage, and when the foam collides and accumulates to a certain weight, it will not be able to hang on the wall and will slide to the quartz glass sheet at the bottom of the sample pool. If it slides to the vicinity of the focusing position, it will cause a macroscopic morphological effect of suspended droplet imaging. If it slides to the focusing center of the microscope objective 407, it will affect the refraction effect and cause the suspended droplets to fall.

[0064] Compared with the prior art, the sample pool structure of the present invention can make the gas enter and discharge the sample pool evenly, and ensure the stability of the gas pressure in the sample pool, thereby stabilizing the optical tweezers to suspend a single droplet, and reducing the contact between the droplet and the wall, thereby reducing the wall effect; and the diameter of the gas inlet and the diameter of the gas outlet are both smaller than the diameter of the single droplet inlet. When a single droplet is pumped into the sample pool from the single droplet inlet, the turbulent effect of the aerosol droplets in the sample pool can be generated and enhanced. The rapid and swirling airflow does not simply go from the inlet to the outlet, but approaches the center of the sample pool (i.e., the laser focusing center) by means of turbulent action. At the same time, the swirling effect can also increase the probability of the airflow outside the focusing center returning to the focus, thereby increasing its capture efficiency, and reducing the probability of aerosol droplets depositing on the inner wall of the sample pool, reducing the error influence of the wall effect on the measurement result.

[0065] The single droplet optical tweezers suspension system 1 further comprises an illumination light source 102, which is disposed above the sample pool 101. When the ambient light is weak, a bright field is provided for detection, so that the droplet detection device 6 can clearly see the image of the droplet.

[0066] The optical coupling system 4 comprises an LED light source module, a collimating lens 405, a beam shaping component 406, a focusing lens component and a semi-transparent and semi-reflective mirror component which are arranged in sequence.

[0067] The LED light source module is used to provide light for detection; the collimating lens is used to collimate the light beam emitted by the LED light source module to reduce the divergence angle; the beam shaping component is used to uniform the light intensity distribution of the collimated light and optimize the shape of the light beam to obtain a high-quality parallel light beam; the focusing lens component is used to expand the high-quality parallel light beam; the semi-transparent and semi-reflective mirror component is used to split the expanded light beam.

[0068] The focusing lens assembly includes two focusing lenses 402 that are arranged opposite to each other, and the semi-transparent and semi-reflective mirror assembly includes two semi-transparent and semi-reflective mirrors 403 that are arranged opposite to each other and in parallel.

[0069] The detection device of the present invention further includes a total reflection mirror 404 and a microscope objective lens 407. The microscope objective lens 407 is used to introduce a light beam into the sample pool 101 for optical tweezers, and is disposed between the first semi-transparent and semi-reflective mirror 403 and the single droplet optical tweezers suspension system 1. The total reflection mirror 404 is used to reflect the optical signal to the droplet detection device 6, and is disposed between the second semi-transparent and semi-reflective mirror 403 and the droplet detection device 6.

[0070] The LED light source module includes an LED light source 401, a light source and a thermal management system. The light source is an adjustable light source, and the light intensity can be controlled by adjusting the current to meet the capture requirements of different particle sizes and properties.

[0071] The thermal management system includes a heat sink or air cooling system to maintain a stable output of the light source and avoid power attenuation.

[0072] The light beam emitted by the LED light source 401 is first collimated by the collimating lens 405 to reduce the divergence angle. The collimated light beam passes through the beam shaping component 406 to even out the light intensity distribution and optimize the shape of the light beam to obtain a high-quality parallel light beam. After the light beam is expanded by a group of focusing lenses 402, it is split by a group of semi-transparent and semi-reflective mirrors 403 and guided to the single droplet optical tweezers suspension system 1, the beam coupling system 4 and the signal detection system 5 respectively. The light beam split to the single droplet optical tweezers suspension device 1 is sent to the microscope objective 407, and the laser is focused above the focal plane to capture the single droplet in the sample pool 101 and suspend it. The scattered light signal of the single droplet is input into the signal detection system 5 and the droplet detection device 6 respectively, and the light signal can be processed by the filter before entering the signal detection system 5.

[0073] A focusing lens 402 is provided between the second semi-transparent and semi-reflective mirror 403 and the signal detection system 5 , and is used to focus the optical signal from the second semi-transparent and semi-reflective mirror 403 and transmit it to the signal detection system 5 .

[0074] The light beam distributed to the single droplet suspension system 1 passes through the microscope objective 407, focusing the light of the LED light source above the focal plane, forming a stable light field gradient in the sample pool 101 to capture and suspend a single droplet. By collimating and shaping the LED light beam, the system achieves a more uniform light field distribution, improving the capture efficiency and signal detection sensitivity. The scattered light signal of the single droplet is input into the signal detection system 5 and the droplet detection device 6 respectively, and the light signal can be processed by the filter before entering the signal detection system 5.

[0075] Specifically, the beam shaping component 406 is a microlens array or an aspherical lens.

[0076] When the beam shaping component 406 is a microlens array, such as Figure 8 As shown, it is illustrated in a rectangular package form, and a number of micro lens units are evenly arranged inside. Each micro lens is in the shape of a convex lens, and the convex lens can be a spherical lens or an aspherical lens according to factors such as the required focal length or aberration correction.

[0077] In a specific embodiment, the array as a whole is usually arranged in a square (row × column) grid, and the lens spacing between each row and each column is equal, which is conducive to achieving uniform light in the subsequent optical path, reducing hot spots, or splitting / focusing the divergent light beam to a specific position.

[0078] In the beam shaping stage, microlens arrays have the following advantages:

[0079] Light homogenization: The array can shape the originally uneven LED light distribution into a more uniform multi-beam or flat-top light field, and then obtain a stable single captured light spot after focusing by downstream optical elements;

[0080] Reduce aberration: It can reduce spherical aberration, coma, etc., so that the subsequent converged main light spot has higher light intensity and less stray light in the working area;

[0081] Spatial flexibility: Although most microlens units are not directly involved in "single droplet capture", their presence can effectively utilize the luminous flux of the LED and improve the overall light energy utilization rate; if it is necessary to expand to multi-point capture or parallel detection in the future, the array design can also be quickly adapted.

[0082] Figure 8 The red arrows indicate the incident and exiting directions of the light beam. The light beam shaping component 406 of the present invention adopts a microlens array, which can improve the light field quality and system stability while maintaining the single droplet capture function.

[0083] In addition, the present invention also includes an optical path scheme based on an axicon-lens system. Specifically, the beam shaping component 406 is an axicon component, and the light beam of the LED light source 401 passes through the collimating lens 405 and then generates a Bessel beam through an axicon component. The Bessel beam has a non-diffraction characteristic and can maintain a stable light intensity distribution over a long distance. Afterwards, the Bessel beam is focused by the focusing lens 402 to form a local hollow beam at the focal plane. The local hollow beam forms a dark area in the sample pool 101, and a high light intensity gradient is formed around the dark area to enhance the capture ability and stability of particles. The introduction of this scheme not only reduces the cost of the system, but also improves the uniformity of the light field and the efficiency of capture, and is particularly suitable for the stable suspension and precise control of single droplets or particles.

[0084] like Fig. 9 As shown in the figure, the core component of the axicon assembly is the axicon. The axicon is composed of one or more pieces of optical materials in the shape of a cone or a cone lens. Fig. 9 The triangular cross section is shown in FIG.

[0085] The Axicon components are arranged as follows:

[0086] Single Axicon: The most common form, i.e. Fig. 9 The one-piece axicon shown in , with the vertex aligned with the optical axis, can produce an annular or Bessel beam on the output side.

[0087] Double Axicons: Two Axicons with different vertex angles or refractive indices are connected in series to more accurately control the inner and outer radius of the annular beam or adjust the focal depth.

[0088] Axicon array: If you need to generate multiple annular beams in parallel over a larger area, you can arrange multiple small-aperture axicon units on the same substrate. This design is more complex and suitable for multi-point capture or parallel operation scenarios.

[0089] The axicon assembly of the present invention functions as follows:

[0090] Generate annular (Bessel) beams: When a collimated or nearly collimated beam is refracted through the conical surface of an axicon, a ring-shaped light field can be formed on the output side; if the light source has a certain degree of coherence, an intensity profile similar to the Bessel distribution can be obtained, which has the characteristics of long focal depth and self-healing.

[0091] Constructing hollow light spots / dark areas: Further combined with focusing lenses or apertures, a local hollow light beam can be formed in the focal plane for the capture, manipulation and positioning of micro-nanoparticles or droplets.

[0092] Simplify the system and reduce costs: Compared with relying on high-power lasers, the use of low-coherence light sources such as LEDs combined with axicons can significantly reduce system costs and safety risks while ensuring a certain optical capture capability.

[0093] In summary, the axicon component plays a key role in shaping the incident light into a ring or Bessel beam in this system. Combined with subsequent optical units (such as focusing lenses, sample cells, etc.), it can achieve stable capture of single or a small number of particles. This component has significant advantages for scenes that require a long focal depth or a strong gradient force field.

[0094] The droplet pumping system 3 includes an aerosol generator 301 , a stop valve (not shown in the figure) and a droplet beam device (not shown in the figure) which are connected in sequence, and the droplet beam device is connected to the sample pool 101 .

[0095] Exemplarily, as shown in FIG. 3( a ), the droplet beam device 303 includes a plurality of pipes 3031 with different inner diameters connected in sequence, and the inner diameters of the plurality of pipes 3031 gradually decrease along the aerosol flow direction.

[0096] Furthermore, as shown in Figure 3(b) and Figure 4 As shown, a plurality of apertures 3032 with different inner diameters are arranged inside the pipeline 3031, and the inner diameters of the plurality of apertures 3032 gradually decrease along the aerosol flow direction.

[0097] For example, Figure 4 As shown, along the flow direction of the aerosol droplets, three apertures with gradually decreasing inner diameters are sequentially arranged in the first pipeline, an aperture with a smaller inner diameter than the inner diameter of the second pipeline is arranged at the outlet of the second pipeline, and an aperture with a smaller inner diameter than the inner diameter of the third pipeline is arranged at the outlet of the third pipeline. This embodiment can gradually arrange the gathered droplets into a string and discharge them from the outlet, as shown in FIG. Figure 5 shown.

[0098] For example, the inner diameter of the aperture at the outlet of the third pipeline is greater than or equal to the diameter of a single droplet and less than the diameter of the single droplet × 2. In other words, the aperture at the outlet of the third pipeline can only pass a single droplet at a time. Figure 5 shown.

[0099] Exemplarily, the aperture is coaxially arranged with the pipeline, and a gasket 3033 is arranged between the aperture and the inner wall of the pipeline ( FIG. 3( c )).

[0100] Exemplarily, a clamp 3034 is provided at the inlet end of the first tube for fixing the tube and adjusting the tube so that it is aligned with the light capture point in the sample pool 101 .

[0101] Exemplarily, a threaded cap 3035 with a central hole is provided at the outlet of the third pipeline. The threaded cap 3035 is used to protect the outlet of the third pipeline.

[0102] The gas atmosphere control system 2 includes a dry gas control device and a wet gas control device. The dry gas control device and the wet gas control device each include a gas storage tank 201 and a flow meter 202. The wet gas control device also includes a humidifying container 203 for increasing the humidity of the gas coming out of the gas storage tank.

[0103] The functions of the gas atmosphere control system 2 include: first, to introduce ambient gas into the sample pool 101; second, to dilute the aerosol droplets in the droplet beam device; third, to pass dry gas and / or wet gas to adjust the ambient humidity in the sample pool; fourth, by replacing the gas storage tank, reactive gas can be introduced into the sample pool 101.

[0104] The signal detection system 5 includes an optical imaging camera 501, a spectrometer 502 and a data processing unit 503. The spectral imaging of the droplet is performed on the optical imaging camera EMCCD 501 through the grating in the Raman spectrometer 502 to obtain the spectral information and stimulated elastic scattering spectrum of different pixel elements; based on the whispering gallery mode of the spherical droplet, the radius of the droplet is inverted according to the Mie scattering theory; the stimulated elastic scattering spectrum and resonance signal of the suspended single droplet are obtained through the optical imaging camera 501 and the spectrometer 502; and the spectrum information is converted into radius, refractive index and peak position information through the data processing unit 503. According to the displacement of the stimulated elastic scattering signal on the Rayleigh scattering peak of the droplet, the droplet radius change rate dr / dt can be inverted to analyze the chemical composition of the droplet and the change of components.

[0105] The droplet detection device 6 is used to monitor the macroscopic morphology of the droplets when they are suspended. Specifically, the droplet detection device 6 is a microscopic imaging camera.

[0106] In a second aspect, the present invention also provides an LED-based aerosol single droplet optical tweezers detection method, using the above-mentioned device, the method comprises the following steps:

[0107] Step 1: The droplet pumping system pumps the aerosol into the sample pool of the single droplet suspension system in the form of a single droplet;

[0108] Step 2: The LED light emitted by the beam coupling system is used as the reaction beam to capture a single droplet in the sample pool and suspend it using the optical tweezers technique;

[0109] Step 3: introducing gas into the sample cell through a gas atmosphere control system;

[0110] Step 4: The scattered light signal of the single droplet is input into the signal detection system and the droplet detection device respectively, and the change in the radius of the single droplet before and after the single droplet reaction is analyzed based on the light signal data.

[0111] Furthermore, in step 1, the droplets are arranged into a string by the droplet beam device 303 of the droplet pumping system 3 to form an aerosol droplet beam, so that the aerosol droplets enter the sample pool 101 one by one as a monodisperse single string of droplets. In this way, it is effectively avoided that the aggregated aerosol droplets enter the sample pool at the same time and are easily deposited on the wall to produce the wall effect.

[0112] Further, as required, the gas introduced in step 3 is ambient gas, background gas, reaction gas, dry gas and / or wet gas.

[0113] The purpose of introducing ambient gas is to provide radiation pressure, that is, the light beam exerts radiation pressure on the droplets, thereby achieving manipulation of the droplets.

[0114] The purpose of introducing background gas is to dilute the droplets in the droplet beam device 303, and further promote the droplet beam device 303 to transform the droplets from an aggregated state into a monodispersed single string of droplets that enter the sample pool one by one.

[0115] The purpose of introducing the reaction gas is to provide reaction gas.

[0116] The purpose of introducing dry gas and / or wet gas is to reduce the humidity in the sample pool 101 to below the weathering point humidity of the volatile chemical components in the droplets, so that the droplets on the inner wall of the sample pool 101 weather and crystallize, and then adjust the humidity in the sample pool 101 to the humidity required for the reaction.

[0117] Specifically, in step 3, the humidity in the sample pool 101 is adjusted to a relative humidity of 30%-40% RH, for example, 30% RH, 35% RH, 40% RH, so that the droplets on the inner wall of the sample pool 101 are weathered and crystallized, and then the relative humidity in the sample pool 101 is adjusted to above 80% RH, for example, 80% RH, 85% RH, 90% RH.

[0118] Humidity can be adjusted by the mass flow ratio of dry gas and wet gas. For example, the dry gas reading range is 0.05-0.15 SLPM and the wet gas reading is 0.15-0.05 SLPM. The humidity of dry and wet gas can be adjusted by adjusting the readings of dry gas and wet gas, that is, adjusting the ratio of dry gas and wet gas. The larger the dry gas / wet gas ratio, the lower the humidity; the smaller the dry gas / wet gas ratio, the higher the humidity.

[0119] The present invention reduces the humidity to below the weathering point humidity, so that the droplets attached to the wall are weathered and crystallized first compared to the droplets suspended by the optical tweezers. The solid after weathering and crystallization no longer has the curvature radius of the liquid phase, and the curvature radius of the droplet determines the surface pressure, which is also the key value on which the saturated vapor pressure of the droplet depends. Therefore, by reducing the humidity to first weather and crystallize the droplets on the wall, the influence of the surface pressure and saturated vapor pressure is eliminated, and then the humidity is raised to the humidity conditions required for the reaction, thereby accurately obtaining the saturated vapor pressure value of the single droplet of the optical tweezers.

[0120] It should be noted that the reasons why the droplets attached to the vessel wall weather and crystallize before the droplets tweezed by the optical tweezers are: (1) The temperature of the vessel wall is usually lower than that of the center of the sample pool because the heat exchange between the vessel wall and the surrounding environment is more direct. This temperature difference makes it easier for the droplets on the vessel wall to reach the conditions for weathering and crystallization; (2) The optical tweezers technique can precisely control the position of a single droplet, keeping it in the center of the sample pool and away from the vessel wall, which reduces the chance of the central droplet contacting the vessel wall, while the droplets on the vessel wall are more easily affected by environmental conditions.

[0121] By lowering the humidity to below the weathering point, the droplets attached to the vessel wall weather and crystallize before the droplets being tweezed, thereby reducing the influence of the vessel wall effect on the saturated vapor pressure of a single droplet. The principle is as follows: (1) When the humidity is lowered to below the weathering point, the droplets on the inner wall of the sample pool will begin to weather due to the decrease in ambient humidity, that is, the water in the droplets gradually evaporates, causing the solute concentration in the droplets to increase, eventually reaching a saturated state and beginning to crystallize. This process reduces the content of volatile organic components in the droplets; (2) Since volatile organic components are more likely to evaporate in a low humidity environment, these components will be removed during the weathering and crystallization process, thereby reducing their potential impact on subsequent experiments. At this time, the saturated vapor pressure of the solid-liquid mixture is determined by the adsorbed water molecules, rather than the original volatile organic components; (3) When the humidity in the sample pool is readjusted to the humidity required for the reaction, the crystals on the vessel wall will adsorb water molecules in the environment to form a solid-liquid mixture. At this time, the liquid phase in the solid-liquid mixture is composed only of adsorbed water molecules and no longer contains the original volatile organic components; (4) The Kelvin effect shows that the smaller the radius of curvature, the greater its saturated vapor pressure.

[0122] In summary, the droplets attached to the bottom of the sample pool all reduce their radius of curvature to avoid the error of the saturated vapor pressure of the volatile components. The droplets on the inner wall are first dehumidified to below the weathering point of the volatile component droplets by first dehumidifying and then rehumidifying, so that the water molecules inside the droplets evaporate and the droplets become smaller and the radius of curvature increases, causing the droplets on the wall to weather and crystallize before the droplets suspended by the optical tweezers; when the humidity rises, the saturated vapor pressure of the solid-liquid mixture is determined by the adsorbed water molecules, rather than the original volatile organic components.

[0123] Compared with the droplets on the inner wall, the droplets suspended by optical tweezers do not show weathering and crystallization for the following reasons: the single droplet suspended by optical tweezers always maintains a spherical shape and always has a radius of curvature. From the perspective of avoiding the vessel wall effect: (1) The optical tweezers technology can accurately control the position of the droplets to keep them in the center of the sample pool. The temperature and humidity conditions in this area may be relatively stable and not easily affected by changes in the external environment. (2) The optical tweezers manipulate the droplets by focusing the radiation pressure generated by the LED light beam. This manipulation method can isolate the direct heat exchange between the droplets and the vessel wall to a certain extent, reducing the drop in surface temperature and evaporation of the droplets caused by the cooling of the vessel wall. (3) The humidity in the vessel wall area decreases first, prompting the weathering and crystallization of the droplets on the vessel wall, while the humidity change in the central area is slower than that of the vessel wall, so the vessel wall first experiences weathering and crystallization. (3) The aerosol droplets suspended by the optical tweezers are already in a supersaturated state and have a small particle size. The surface properties are different from those of the droplets deposited on the vessel wall. The differences in the surface and interface colloidal properties of the aerosol itself may also be the reason why the evaporation rate and weathering and crystallization of the vessel wall droplets take precedence over the droplets suspended by the optical tweezers.

[0124] The detection method of the present invention is described in detail below in conjunction with specific embodiments.

[0125] Example 1

[0126] Taking ammonium sulfate as an example, an aerosol containing ammonium sulfate components is first prepared by an aerosol generator (301) and pumped into the sample pool (101) of the single droplet optical tweezers suspension system (1) to form a single droplet. At this time, the light beam emitted by the LED light source 401 in the beam coupling system 4 is shaped by the collimating lens 405 and the beam shaping component 406 (microlens array), and then expanded by the focusing lens component and focused by the microscope objective 407 to construct an optical potential well above the focal plane of the sample pool 101. The single droplet of the ammonium sulfate aerosol is stably captured and kept in suspension by the optical gradient force.

[0127] On this basis, the gas atmosphere control system 2 accurately controls the ratio of dry gas, wet gas and trace reaction gas through the pressure reducing valve and flow meter, thereby simulating the humidity and composition of the real atmospheric environment (the relative humidity in the sample pool 101 is 80%RH). As the mixed gas continues to flow through the sample pool 101, the external field environment of the single droplet will change accordingly, thereby causing dynamic changes in characteristic parameters such as droplet particle size and refractive index.

[0128] The single droplet scattered light signal is coupled to the signal detection system 5 and the droplet detection device 6 respectively, to realize the visualization imaging and optical recording of the single droplet. Finally, by analyzing the spectral peak shift or light intensity distribution generated by stimulated elastic scattering and combining it with the Mie scattering theory, the refractive index and radius changes of the suspended droplets under different reaction processes can be inverted. This allows in-depth research on the mass transfer and phase change characteristics of ammonium sulfate aerosol in different humidity and chemical environments.

[0129] Example 2

[0130] This embodiment is substantially the same as the embodiment 1, except that the beam shaping component 406 is an axicon component, and the relative humidity in the sample cell 101 is 90% RH.

[0131] Figure 6 This is a spectrum diagram showing the change of the resonance peak position over time obtained by detecting a single droplet in Example 1 of the present invention; Figure 7 This is a spectrum diagram showing the change of the resonance peak position over time obtained by using the existing detection device (laser light source grasping and measurement) to detect a single droplet using optical tweezers technology.

[0132] Figure 6 The peak position shift can be clearly seen in Figure 7 Although there is a continuous linear change trend, a large number of noise points are still identified, which will lead to the subsequent numerical judgment of the droplet radius and refractive index after Mie scattering inversion, and the inability to accurately calculate dr / dt and the droplet radius value. Therefore, the detection device (LED light source capture and measurement) of the present invention is less affected by noise signals than the existing detection device (laser light source capture and measurement) for single droplet detection, and is more conducive to accurate detection, thereby improving the accuracy and sensitivity of detection.

[0133] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An aerosol single droplet optical tweezers detection system based on LED light source, characterized in that: It includes a beam coupling system, a single droplet suspension system, a gas atmosphere control system, a droplet pumping system, a signal detection system and a droplet detection device; The gas atmosphere control system is connected to the single droplet suspension system, the droplet pumping system is connected to the single droplet suspension system, and the beam coupling system is connected to the single droplet suspension system, the signal detection system and the droplet detection device respectively; The beam coupling system is used to improve the optical gradient force of the LED light source, and is composed of an LED light source module, a collimating lens, a beam shaping component, a focusing lens component and a semi-transparent and semi-reflective mirror component arranged in sequence; The LED light source module is used to provide light for detection; the collimating lens is used to collimate the light beam emitted by the LED light source module to reduce the divergence angle; the beam shaping component is used to even out the light intensity distribution of the collimated light and optimize the shape of the light beam to obtain a high-quality parallel light beam; the focusing lens component is used to expand the high-quality parallel light beam; the semi-transparent and semi-reflective mirror component is used to split the expanded light beam; The LED light source module includes an LED light source, and the LED light source provides light with a wavelength of 365-650 nm.

2. The detection system according to claim 1, characterized in that: The beam shaping component is a microlens array or an aspherical lens.

3. The detection system according to claim 1, characterized in that: The beam shaping component is an axicon component.

4. The detection system according to claim 1, characterized in that: The focusing lens assembly includes two focusing lenses arranged opposite to each other.

5. The detection system according to claim 1, characterized in that: The semi-transparent and semi-reflective mirror assembly comprises two semi-transparent and semi-reflective mirrors arranged oppositely and in parallel.

6. The detection system according to claim 1, characterized in that: The single droplet suspension system comprises a sample pool, which comprises a concentric outer annular wall and an inner annular wall, wherein a connecting portion is provided between the outer annular wall and the inner annular wall.

7. The detection system according to claim 1, characterized in that: The gas atmosphere control system comprises a dry gas control device and a wet gas control device; the dry gas control device and the wet gas control device both comprise a gas storage tank and a flow meter.

8. The detection system according to claim 7, characterized in that: The wet gas control device further includes a humidifying container.

9. An aerosol single droplet optical tweezers detection method based on LED light source, characterized in that: The detection system according to any one of claims 1 to 8 is used to complete the process, comprising the following steps: Step 1: The droplet pumping system pumps the aerosol into the sample pool of the single droplet suspension system in the form of a single droplet; Step 2: The LED light emitted by the beam coupling system is used as the reaction beam to capture a single droplet in the sample pool and suspend it using the optical tweezers technique; Step 3: introducing gas into the sample cell through a gas atmosphere control system; Step 4: The scattered light signal of the single droplet is input into the signal detection system and the droplet detection device respectively, and the change in the radius of the single droplet before and after the single droplet reaction is analyzed based on the light signal data.

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