Method for sorting particles in liquid based on thermoelectric optical tweezers

Abstract

The invention discloses a method for sorting particles in liquid based on thermoelectric optical tweezers. The method comprises the steps that 1, the particles to be sorted and a surfactant hexadecyl trimethyl ammonium chloride solution are mixed to form a sample solution, and the sample solution is dropwise added into a sample pool; 2, controlling the emergent power by adjusting a neutral density filter, focusing a light beam through an objective lens, then capturing particles above the graphene layer, and observing the captured particles in real time through the imaging module; and 3, the speed of the electric linear displacement table is adjusted through an open-loop controller till space separation is generated among the captured particles, and particle separation is achieved. According to the method, the problem that potential thermal damage exists in the sample due to the fact that the laser power in traditional optical sorting is too high is solved. The sorting of various types of particles is realized by changing the speed of the displacement table, which is of great significance to the application of the optical tweezers technology in the fields of cell sorting, transportation and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical tweezers, relates to an optical tweezers capturing and sorting method, and specifically relates to a method for sorting particles in liquid based on thermoelectric optical tweezers. Background Art

[0002] Microparticle sorting is typically performed using traditional optical tweezers, a tool that uses the radiation pressure of light to manipulate objects. Unlike traditional mechanical tweezers, optical tweezers offer non-contact, non-destructive manipulation. They are widely used in the manipulation of microparticles, particularly biomolecules and living cells.

[0003] However, due to the limitations of traditional optical tweezers for sorting tiny particles, on the one hand, the shape-induced optical force difference between Rayleigh and Mie particles in traditional optical tweezers systems is very small, resulting in less than ideal results for shape-based bacterial sorting. On the other hand, the increase in capture force of traditional optical tweezers relies on the gradient force provided by a high-power, tightly focused laser, which inevitably causes thermal damage to biological particles and exacerbates Brownian motion, reducing the stability of capture.

[0004] In summary, there is an urgent need to research a low-power and highly adaptable particle sorting technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for sorting particles in liquid based on thermoelectric optical tweezers, so as to solve the problems of high power and low sorting adaptability when using traditional optical tweezers to sort tiny particles in the prior art.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A method for sorting particles in a liquid based on thermoelectric optical tweezers, the method employing a device for sorting particles in a liquid based on thermoelectric optical tweezers to perform particle sorting; the device comprises a laser, a filter, a beam expansion module, a dichroic mirror, an objective lens, an illumination and imaging module, and a capture and sorting module; the illumination and imaging module, the objective lens, and the dichroic mirror are located on the same optical axis; the capture and sorting module comprises a sample pool and an electric displacement module, the sample pool and the electric displacement module being fixed by a connecting rod; the sample pool is located at a working distance of the objective lens; the sample pool comprises a top glass sheet with a central opening and a bottom glass sheet of the same size and coated with a graphene film at the center; the electric displacement module comprises an electric linear translation stage and an open-loop controller; the continuous laser light emitted by the laser changes its output power through the filter, is expanded by the beam expansion module, and is reflected and coupled by the dichroic mirror into the objective lens, whereupon the laser light focused by the objective lens acts on the sample pool;

[0008] The method specifically includes the following steps:

[0009] Step 1: Mix the particles to be sorted with a surfactant cetyltrimethylammonium chloride solution to form a sample solution, and dropwise add the solution into a sample cell;

[0010] Step 2: controlling the output power by adjusting the neutral density filter, focusing the light beam through the objective lens to capture particles above the graphene layer, and observing the captured particles in real time through the imaging module;

[0011] Step 3: Adjust the speed of the electric linear translation stage through the open-loop controller until spatial separation occurs between the captured particles, thereby achieving particle sorting.

[0012] Furthermore, in step 2, the power is adjusted by rotating the adjustable neutral density filter until the power after the objective lens is 2.5 mW.

[0013] Furthermore, in step 3, the speed of the electric linear translation stage, that is, the moving speed of the sample cell, is set by an open-loop controller. When the laser power is 2.5 mW, the speed is set to 0.8 μm / s.

[0014] Furthermore, the laser is a 532nm semiconductor continuous laser.

[0015] Furthermore, the filter is an adjustable neutral density filter, and the power of the laser emitted by the laser is adjusted through the neutral density filter.

[0016] Furthermore, the beam expansion module includes a first lens and a second lens; the distance between the first lens and the second lens is the sum of the focal lengths of the two lenses; the laser passing through the filter is expanded by the first lens and the second lens and then reflected by the dichroic mirror into the objective lens.

[0017] Furthermore, the lighting and imaging module includes a light-emitting diode and an imaging device; the illumination light passes through the sample cell and then is transmitted through the objective lens and the dichroic mirror into the imaging device.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The method of the present invention is based on thermoelectric optical tweezers to achieve particle capture, using laser-induced thermoelectric effect in solution to generate thermoelectric power on particles, thus solving the high power problem of traditional optical tweezers capture.

[0020] (2) The method of the present invention is based on the difference in capture stiffness between sorted particles. It achieves the sorting of various types of particles by controlling the speed of the electric linear translation stage, which solves the problem of low adaptability of optical sorting methods and is of great significance for the practical application of optical tweezers.

[0021] (3) The separation device used in the method of the present invention is easy to implement, easy to operate, low in cost, and easy to promote.

[0022] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 This is a scanning electron microscope experimental image of the sorted particles of the present invention;

[0025] Figure 3 This is an experimental diagram showing the variation of capture stiffness of the particles being sorted according to the present invention with laser power;

[0026] Figure 4 Experiments for sorting different particles for the present invention;

[0027] The meaning of each number in the figure: 1-laser, 2-filter, 3-beam expansion module, 4-dichroic mirror, 5-objective lens, 6-illumination and imaging module, 7-capture and sorting module;

[0028] 301-first lens, 302-second lens;

[0029] 601-light emitting diode, 602-imaging module.

[0030] 701-sample cell, 702-electric displacement module.

[0031] 7011-top glass sheet, 7012-bottom glass sheet.

[0032] 7021-Motorized linear translation stage, 7022-Open-loop controller.

[0033] The specific contents of the present invention are further explained in detail below with reference to the embodiments. DETAILED DESCRIPTION

[0034] It should be noted that the mechanism of the present invention for sorting particles in liquids based on thermoelectric optical tweezers is the difference in forces acting on different particles in the thermoelectric optical tweezers system. The laser light emitted by the laser is focused by the objective lens onto the graphene film at the bottom of the sample cell, forming a temperature gradient in the sample solution. The surfactant hexadecyltrimethylammonium chloride in the sample solution, on the one hand, adheres to the surface of the particles to regulate the surface potential of the particles; on the other hand, the surfactant hexadecyltrimethylammonium chloride molecules form a local electric field under the action of the thermal gradient. The electric field E T It can be expressed as:

[0035]

[0036] Where i represents the ion species, i.e., hexadecyltrimethylammonium chloride micellar ion or Cl - , T is the ambient temperature, e is the elementary charge. i , n i , S Ti They represent the charge number, concentration and Soret coefficient of ion i respectively. T Pointing to the center of the laser beam, this will cause the particles wrapped by the hexadecyltrimethylammonium chloride molecules to be subjected to a thermal electric force f toward the center of the laser e Thermal power f e It can be obtained by numerically integrating the electric field and the effective charge q, and the expression is:

[0037]

[0038] The capture stiffness of a particle describes the ability of the particle to be constrained by the capture potential well in the capture system. By collecting the position distribution of the particle after stable capture, the position fluctuation variance σ of the particle after capture can be fitted using a Gaussian distribution. The capture stiffness k can be calculated as:

[0039] k=k B T / σ 2 (3)

[0040] It should be noted that by calibrating the capture stiffness between particles, we can achieve particle sorting based on the difference in capture stiffness. When the sample moves in the pool, it is subject to the viscous resistance f of the solution. d =6πηRu. Increasing the movement speed can increase the viscous resistance of the particles as they move with the potential well. Therefore, when the movement speed of the sample cell reaches the threshold, the particle with the lower capture stiffness will no longer move with the capture potential well and will escape the well, resulting in the separation of particles with the higher capture stiffness.

[0041] It should be noted that, unless otherwise specified, all components in the device used in the method of the present invention are components known in the art.

[0042] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0043] Example:

[0044] This embodiment provides a method for sorting particles in liquid based on thermoelectric optical tweezers, wherein the method uses a device for sorting particles in liquid based on thermoelectric optical tweezers to sort particles; Figure 1 As shown, it includes a laser 1, a filter 2, a beam expansion module 3, a dichroic mirror 4, an objective lens 5, an illumination and imaging module 6, and a capture and sorting module 7.

[0045] Laser 1 is a 532nm semiconductor continuous laser.

[0046] Filter 2 is an adjustable neutral density filter. The power of the laser emitted by the laser can be adjusted through the neutral density filter.

[0047] The beam expansion module 3 includes a first lens 301 and a second lens 302. The focal length of the first lens 301 is 100 mm, and the focal length of the second lens 302 is 200 mm. The laser beam is expanded to the same size as the incident hole of the objective lens.

[0048] The dichroic mirror 4 is a dichroic mirror that reflects 532 nm laser light and transmits 633 nm laser light, and couples the expanded 532 nm laser light into the objective lens through reflection, while transmitting the illumination light generated by the light emitting diode 601 into the imaging device 602 .

[0049] Objective lens 5 is a semi-apochromatic oil immersion objective lens with a magnification of 100x and a numerical aperture of 1.3. It is mainly used to focus the 532 nm laser on the sample cell and serves as an observation objective lens for the imaging device 602.

[0050] The lighting and imaging module 6 includes a light emitting diode 601 and an imaging device 602 . The light emitting diode 601 emits white light with a wavelength of 440 nm to 670 nm. The imaging device 602 is located in a coaxial system with the dichroic mirror 4 and the objective lens 5 .

[0051] The capture and sorting module 7 includes a sample pool 701 and an electric displacement module 702. The sample pool 701 is primarily used to hold the sample to be sorted. Figure (2) shows a scanning electron microscope image of the sorted particles. Figure (3) shows the variation of capture stiffness with laser power for different particles at a hexadecyltrimethylammonium chloride concentration of 3 mM.

[0052] The electric sorting module 702 includes an electric linear displacement stage 7021 and an open-loop controller 7022. The electric displacement stage and the sample cell 701 are fixed by a connecting rod. The speed of the electric linear displacement stage 7021, which is also the movement speed of the sample cell 701, is set by the open-loop controller 7022. When the laser power is 2.5mW and the speed is set to 0.8μm / s, the images of the two particles in the illumination and imaging module 6 are as follows: Figure 4 As shown in Figure 2, it can be seen that as the sample pool moves, 500 nm PS particles are successfully sorted.

[0053] The method of this embodiment specifically includes the following steps:

[0054] A continuous 532 nm laser beam is obtained from the laser 1, and the output power is adjusted by rotating the adjustable neutral density filter 2. The first lens 301 and the second lens 302 are used to expand the laser beam, and the distance between the two lenses is 300 mm.

[0055] After beam expansion, the laser beam is reflected by the dichroic mirror 4 and enters the entrance aperture of the objective lens 5. After being focused, it acts on the graphene thin layer on the bottom glass sheet 7012 of the sample cell 601. The particles to be sorted are mixed with the surfactant hexadecyltrimethylammonium chloride solution and placed in the sample cell 601.

[0056] The power of the objective lens is adjusted to 2.5 mW by rotating the adjustable neutral density filter 2. The light emitting diode 601 provides illumination light, which is collected by the imaging device 602 after passing through the sample cell 601, the objective lens 5 and the dichroic mirror 4.

[0057] The captured images are used to observe the capture status of the particles in real time. After successfully capturing two types of particles, the speed of the electric linear translation stage 7021 is controlled by the open-loop controller 7022. Finally, when the speed reaches a threshold, the two particles will be successfully sorted.

Claims

1. A method for sorting particles in liquid based on thermoelectric optical tweezers, characterized in that: The method adopts a device for sorting particles in liquid based on thermoelectric optical tweezers to sort particles; the device comprises a laser (1), a filter (2), a beam expansion module (3), a dichroic mirror (4), an objective lens (5), an illumination and imaging module (6), and a capture and sorting module (7); the illumination and imaging module (6), the objective lens (5), and the dichroic mirror (4) are located on the same optical axis; the capture and sorting module (7) comprises a sample pool (701) and an electric displacement module (702), the sample pool (701) and the electric displacement module (702) being fixed by a connecting rod; the sample pool (701) is located on the objective lens. The sample pool (701) comprises a top glass sheet (7011) with a central opening and a bottom glass sheet (7012) of the same size and covered with a graphene film in the center; the electric displacement module (702) comprises an electric linear displacement stage (7021) and an open-loop controller (7022); the continuous laser light emitted by the laser (1) changes the output power through the filter (2), is expanded by the beam expansion module (3), and is then reflected and coupled by the dichroic mirror (4) into the objective lens (5); the laser light focused by the objective lens (5) acts on the sample pool (701); The method specifically includes the following steps: Step 1: mixing the particles to be sorted with a surfactant cetyltrimethylammonium chloride solution to form a sample solution, and dripping the solution into a sample cell (701); Step 2, controlling the output power by adjusting the neutral density filter (2), focusing the light beam through the objective lens (5) to achieve particle capture above the graphene layer, and observing the captured particles in real time through the imaging module (6); Step 3: Adjust the speed of the electric linear translation stage (7022) through the open-loop controller (7021) until spatial separation occurs between the captured particles, thereby achieving particle sorting.

2. The method for sorting particles in liquid using thermoelectric optical tweezers according to claim 1, wherein: In the step 2, the power is adjusted to 2.5 mW after the objective lens by rotating the adjustable neutral density filter (2).

3. The method for sorting particles in liquid using thermoelectric optical tweezers according to claim 2, wherein: In step 3, the speed of the electric linear translation stage (7021), that is, the moving speed of the sample cell (701), is set by the open-loop controller (7022). When the laser power is 2.5 mW, the speed is set to 0.8 μm / s.

4. The method for sorting particles in liquid using thermoelectric optical tweezers according to claim 1, wherein: The laser (1) is a 532nm semiconductor continuous laser.

5. The method for sorting particles in liquid using thermoelectric optical tweezers according to claim 1, wherein: The filter (2) is an adjustable neutral density filter, and the power of the laser light emitted by the laser (1) is adjusted through the neutral density filter.

6. The method for sorting particles in liquid using thermoelectric optical tweezers according to claim 1, wherein: The beam expansion module (3) comprises a first lens (301) and a second lens (302); the distance between the first lens (301) and the second lens (302) is the sum of the focal lengths of the two lenses; the laser light passing through the filter (2) is expanded by the first lens (301) and the second lens (302) and then reflected by the dichroic mirror (4) into the objective lens (5).

7. The method for sorting particles in liquid using thermoelectric optical tweezers according to claim 1, wherein: The lighting and imaging module (6) comprises a light-emitting diode (601) and an imaging device (602); the illumination light passes through the sample pool (701) and then passes through the objective lens (5) and the dichroic mirror (4) to enter the imaging device (602).

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