Photo-thermal tweezers control system and method based on multiple layers of MXene

Abstract

The invention discloses a photo-thermal tweezers control system based on multilayer MXene. The photo-thermal tweezers control system comprises a single-mode fiber laser, a plurality of lenses and reflectors, a dichroscope, an oil-immersed objective lens, an MXene photo-thermal response substrate, a halogen lamp, a band-pass filter and a CMOS camera. The invention further discloses a photothermal tweezers control method based on the multiple layers of MXene, the single-mode fiber laser emits linear polarized light, the linear polarized light is focused on the surface of the MXene substrate through the high-power objective lens, the MXene photothermal response substrate generates a local temperature gradient field under excitation of the linear polarized focused light, and PEG molecules can generate thermophoresis and migrate from a hot area to a cold area, so that the photothermal tweezers are formed. And then the micro-nano particles are driven to move towards a hot area, so that the control assembly of the micro-nano particles is realized. According to the invention, the cost is low, the functions are integrated, the biocompatibility is good, and the capture control of a single micro-nano particle, the close-packed assembly of a plurality of micro-nano particles and the in-vivo control of microorganisms such as bacteria and yeast cells can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of photothermal tweezers, and in particular to a photothermal tweezers manipulation system based on multilayer MXene and a method thereof. Background Art

[0002] Since Arthur Ashkin invented the optical tweezers technology, it has made outstanding contributions to single-particle manipulation and deepened human understanding of the nanoworld. He won the Nobel Prize in Physics in 2018. The precise non-contact manipulation capability of optical tweezers has greatly promoted the development of biomedical photonics applications. In traditional optical trapping systems, strong optical gradient forces are required to overcome scattering forces, which usually require relatively high incident laser power density, and the spatial resolution is limited by the diffraction limit, which inevitably produces strong thermal effects in the focal area, leading to two major problems: first, biological samples may be damaged by light and heat, and second, higher laser energy will lead to stronger Brownian motion, thereby reducing the accuracy of particle capture, especially for some nanoscale particles. In order to overcome the application difficulties of traditional optical tweezers, researchers have developed photothermal tweezers. By using optically induced thermal power, nanoparticles can be manipulated on a large scale with sub-wavelength precision. The laser power density required for photothermal tweezers is three orders of magnitude lower than that of traditional optical tweezers. In addition, the photoinduced temperature field optical tweezers adopt a temperature field-dominated manipulation method, which reduces the requirements for the numerical aperture of the manipulation objective lens, and is easier to manipulate particles with a scale smaller than the diffraction limit. It has become an important research tool in the biomedical field.

[0003] Substrate materials play a vital role in photothermal manipulation, such as gold film, gold particles, etc. Traditional photothermal tweezers usually rely on 5 nm gold film. However, due to the limitations of the absorption spectrum range and preparation technology of 5 nm thick gold film, there are certain limitations in the applicable range of incident wavelength and the uniformity of the film; and the reuse rate of micro-nano processed metal substrates is low, resulting in higher cost investment.

[0004] Therefore, there is an urgent need to provide a new type of photothermal tweezers manipulation system and method to solve the above problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a multi-layer MXene-based photothermal tweezers manipulation system and method with low cost, integrated functions and good biocompatibility, which can realize the capture and manipulation of single micro-nano particles and the close-packed assembly of multiple micro-nano particles, as well as the living manipulation of microorganisms such as bacteria and yeast cells.

[0006] In order to solve the above technical problems, a technical solution adopted by the present invention is: providing a photothermal tweezers manipulation system based on multilayer MXene, including a single-mode fiber laser, a plurality of lenses and reflectors, a dichroic mirror, an oil-immersion objective lens, a sample cell, a MXene photothermal response substrate, a halogen lamp, a bandpass filter, a tube lens, and a CMOS camera; The laser emitted by the single-mode fiber laser is collimated and expanded by a number of reflectors and lenses to form parallel light, which is reflected to the rear pupil of the oil-immersed objective lens by a dichroic mirror and focused to the surface of the MXene photothermal response substrate deposited in the sample pool on the sample stage. The halogen lamp located above the sample stage is used as a lighting device to observe the capture status of the photothermal tweezers and sample information in the bright field. The bandpass filter is used to filter out the laser spot to facilitate the observation of the capture status in the bright field. The tube lens is used to focus the filtered light beam carrying the sample information to the center of the camera target surface.

[0007] In a preferred embodiment of the present invention, the MXene photothermal responsive substrate is composed of a glass substrate, a multilayer MXene two-dimensional material, a cover glass, and a PEG solution. The MXene two-dimensional material is deposited on the glass substrate by a wet transfer method, and the sample to be observed is diluted with a PEG solution and then dropped on the glass substrate on which the MXene two-dimensional material is deposited.

[0008] Furthermore, the sample to be observed is PS microspheres or Escherichia coli or yeast cells.

[0009] Furthermore, the mass fraction of the PEG solution is 5-20%.

[0010] In a preferred embodiment of the present invention, the wavelength range of the single-mode fiber laser is 532nm~1064nm.

[0011] In a preferred embodiment of the present invention, the central wavelength of the bandpass filter is 605 nm and the bandwidth is 60 nm.

[0012] In order to solve the above technical problems, another technical solution adopted by the present invention is: to provide a manipulation method of the photothermal tweezers manipulation system based on multilayer MXene as described in any of the above items, wherein the single-mode fiber laser emits linearly polarized light which is focused onto the surface of the MXene substrate through a high-power objective lens, and the MXene photothermal response substrate generates a local temperature gradient field under the excitation of the linearly polarized focused light, and the PEG molecules undergo thermophoresis and migrate from the hot area to the cold area, thereby driving the micro-nanoparticles to move to the hot area, thereby realizing the manipulation and assembly of the micro-nanoparticles.

[0013] In a preferred embodiment of the present invention, the capture and manipulation of a single micro-nano particle and the aggregation and assembly of multiple nanoparticles can be achieved simultaneously under different laser powers and operation times.

[0014] In a preferred embodiment of the present invention, by adjusting the laser power and the focus position of the light spot, different assembly modes of multiple nanoparticles can be switched, including hexagonal close-packed assembly, boundary assembly, and ring-shaped assembly.

[0015] In a preferred embodiment of the present invention, when the sample to be observed is a biological sample, living manipulation of microorganisms can also be achieved.

[0016] The beneficial effects of the present invention are: (1) The system described in the present invention is easy to build, has a simple structure and low cost. A new type of photothermal tweezers based on a MXene substrate is proposed. The photothermal response substrate is a MXene two-dimensional material with excellent photothermal conversion efficiency and high thermal conductivity. By utilizing the photothermal effect of MXene under the excitation of linearly polarized focused light, the capture and manipulation of single micro-nanoparticles and the close-packed assembly of multiple micro-nanoparticles can be achieved, as well as the live manipulation of microorganisms such as bacteria and yeast cells. (2) The system of the present invention uses thermal diffusion to capture biological cells such as Escherichia coli and yeast cells. Compared with traditional optical tweezers, it does not require high-power incident lasers and can achieve stable capture at extremely low laser powers, thereby reducing light damage to cells and stably maintaining cell activity. (3) MXene has excellent photothermal conversion efficiency, high thermal conductivity, light absorption and chemical stability. By replacing the traditional photothermal response substrate with a MXene material with a higher thermal response coefficient, the method of the present invention can achieve more efficient photothermal tweezers manipulation. At lower laser power, stable manipulation of single nanoparticles and large-scale assembly of multiple micro-nanoparticles can be achieved, and different assembly modes can be switched by adjusting the laser power. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the three-dimensional structure of a preferred embodiment of the photothermal tweezers manipulation system based on multilayer MXene of the present invention; Figure 2 It is a diagram of the capture and manipulation of single micro-nanoparticles and the multi-mode assembly of multiple micro-nanoparticles.

[0018] The components in the accompanying drawings are marked as follows: 1. MXene photothermal response substrate, 2. micro-nanoparticles, 3. PEG molecules, 4. sample cell, 5. single-mode fiber laser, 6. reflector, 7. lens, 8. dichroic mirror, 9. oil immersion objective lens, 10. sample stage, 11. halogen lamp, 12. bandpass filter, 13. CMOS camera, 14. tube lens. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0020] See also Figure 1 , the embodiment of the present invention includes: A photothermal tweezers manipulation system based on multilayer MXene includes a single-mode fiber laser 5, a plurality of lenses 7 and reflectors 6, a dichroic mirror 8, an oil-immersed objective lens 9, a sample pool 4, a MXene photothermal response substrate 1, a halogen lamp 11, a bandpass filter 12, a tube lens 14, and a CMOS camera 13. The laser emitted by the single-mode fiber laser 5 is expanded and collimated by a plurality of reflectors 6 and a lens 7 to form parallel light, which is reflected to the rear pupil of the oil-immersed objective lens 9 by the dichroic mirror 8 and focused to the surface of the MXene photothermal response substrate 1 deposited in the sample pool 4 on the sample stage 10. The halogen lamp 11 located above the sample stage 10 is used as an illumination device to observe the capture situation and sample information of the photothermal tweezers in a bright field. The bandpass filter 12 is used to filter out the laser spot to facilitate the observation of the capture state in a bright field. The tube lens 14 is used to focus the filtered light beam carrying the sample information to the center of the target surface of the CMOS camera 13.

[0021] The wavelength range of the single-mode fiber laser 5 is 532 nm to 1064 nm. In this example, the single-mode fiber laser 5 uses a 671 nm laser. The central wavelength of the bandpass filter is 605 nm and the bandwidth is 60 nm.

[0022] The MXene photothermal response substrate 1 is composed of a glass substrate, a multilayer MXene two-dimensional material, a cover glass, and a PEG solution (Polyethylene Glycol, abbreviated as PEG). The MXene two-dimensional material is deposited on the glass substrate by a wet transfer method, and the sample to be observed is diluted with the PEG solution and then dropped on the glass substrate on which the MXene two-dimensional material is deposited.

[0023] In this example, the sample to be observed is PS microspheres or Escherichia coli or yeast cells. Furthermore, the PS microspheres are 500 nm polystyrene (PS) microspheres.

[0024] The mass fraction of the PEG solution is 5-20%. In this example, the mass fraction of the PEG solution is 10%. PEG is a water-soluble nonionic biocompatible polymer that can be used as a surfactant. When the laser heats the MXene substrate, the PEG molecules will undergo thermophoresis and migrate from the hot area to the cold area.

[0025] Specifically, the 671 nm laser emits a 671 nm laser which is reflected by the reflector 6 in turn, then expanded and collimated by two lenses 7 to form parallel light, and expanded by 5 times, and then incident on the dichroic mirror 8 after passing through the two reflectors 6, and then reflected by the dichroic mirror 8 to the rear pupil of the oil-immersed objective lens 9, and the laser is tightly focused to the surface of the MXene photothermal response substrate 1 through the oil-immersed objective lens 9. The illumination device of the optical path is a halogen lamp 11 above the sample stage, which is used to observe the capture situation and sample information of the photothermal tweezers in the bright field. A bandpass filter 12 is provided in front of the CMOS camera 13 to filter out the excitation light, so as to facilitate the real-time observation of the manipulation of the photothermal tweezers.

[0026] Since MXene has excellent photothermal conversion efficiency, high thermal conductivity, light absorption and chemical stability, replacing the traditional photothermal response substrate with a MXene material with a higher thermal response coefficient can achieve more efficient photothermal tweezers manipulation. Therefore, the present invention also provides a manipulation method using a photothermal tweezers manipulation system based on multilayer MXene as described above, wherein the 671 nm single-mode fiber laser emits 671 nm linearly polarized light and is focused onto the surface of the MXene substrate through a high-power objective lens 9. The MXene photothermal response substrate 1 generates a local temperature gradient field under the excitation of the linearly polarized focused light. When the sample to be tested is a PS microsphere, the PEG molecule 3 will undergo thermophoresis and migrate from the hot area to the cold area, thereby driving the micro-nanoparticles 2 to move to the hot area, thereby achieving the manipulation and assembly of the micro-nanoparticles 2.

[0027] At extremely low laser power, the stable capture and manipulation of a single micro-nano particle can be achieved. In addition to single-particle manipulation, the range of thermal diffusion and swimming force is about 4μm, which is much larger than the manipulation range of traditional optical tweezers. Therefore, as time goes by, the aggregation and assembly of multiple nanoparticles can be achieved. At the same time, by adjusting the laser power and the focus position of the light spot, different assembly modes of multiple nanoparticles can be switched, including hexagonal close-packed assembly, boundary assembly, and ring assembly.

[0028] In addition to the manipulation of micro-nanoparticles, the method can also achieve living manipulation of microorganisms such as bacteria and yeast cells, further expanding its application scope in the field of life sciences.

[0029] The system of the present invention captures biological cells such as Escherichia coli and yeast cells by utilizing thermal diffusion swimming force. Compared with traditional optical tweezers, it does not require high-power incident laser and can achieve stable capture at extremely low laser power, thereby reducing light damage to cells, stably maintaining cell activity, and having good biocompatibility.

[0030] Figure 2The system shows the capture and manipulation of a single micro-nanoparticle and the multi-mode assembly of multiple micro-nanoparticles, as shown in Figure (a): Before the laser is turned on, the colloidal particles perform irregular Brownian motion. When the laser is turned on, MXene can absorb laser radiation and effectively convert it into heat. Due to the high photothermal conversion efficiency and low thermal conductivity of MXene, a local temperature field will be generated. Under the uneven temperature gradient, PEG molecules migrate from the hot zone to the cold zone under the action of the positive thermophoretic force, resulting in a concentration gradient and spatial depletion. Therefore, the generated diffusion force can push the suspended colloidal particles or biological cells to the central laser heating point. The colloidal particles are stably captured in the center of the light trap. When the laser beam focus moves from right to left on the substrate, the colloidal particles are still trapped and move dynamically along the laser direction. As the laser is turned off, the colloidal particles are released and resume Brownian motion. This process fully proves that the constructed photothermal tweezers system has the function of stably capturing and manipulating single micro-nanoparticles. The laser incident power is 0.6 mW, the mass fraction of the PEG solution is 10%, and the diameter of the polystyrene microspheres is 500 nm. Since the diffusion force is a long-range attraction, the self-assembly of dielectric particles can be controlled by particle concentration and laser irradiation dose. As shown in Figure (b): Under the same experimental conditions, by adjusting the laser power and the focus position of the spot, different assembly modes can be switched, including hexagonal close-packed assembly, boundary assembly, and ring-shaped assembly. Specifically, when the laser power is 0.6 mW and the laser is focused on the entire MXene nanosheet, a uniform temperature gradient field is formed, radially pointing to the center of the beam. Theoretical analysis shows that the direction of the diffusion force is consistent with the temperature gradient, with a range of about 10 μm, directly pointing to the local heat source with the highest temperature. The experimental results show that multiple colloidal particles can spontaneously form a stable and reversible hexagonal close-packed assembly. When the laser power is increased to 2.3 mW, the particles are rapidly pulled toward the substrate surface under the action of the laser. However, due to the repulsive force generated at the center of the beam (indicated by the red cross), the particles cannot be stably trapped, resulting in a ring-shaped assembly of the particles. When the laser power is 0.6 mW and the laser is focused on the edge of the MXene nanosheet, the particles are boundary assembled along the edge of the MXene. In addition to colloidal particles, Figure 2 (b) The last picture also shows the capture of living biological particles such as E. coli, further broadening its application in life science research.

[0031] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A photothermal tweezers manipulation system based on multilayer MXene, characterized in that: Including single-mode fiber laser, several lenses and reflectors, dichroic mirror, oil immersion objective, sample cell, MXene photothermal response substrate, halogen lamp, bandpass filter, tube lens, CMOS camera; The laser emitted by the single-mode fiber laser is collimated and expanded by a number of reflectors and lenses to form parallel light, which is reflected to the rear pupil of the oil-immersed objective lens by a dichroic mirror and focused to the surface of the MXene photothermal response substrate deposited in the sample pool on the sample stage. The halogen lamp located above the sample stage is used as a lighting device to observe the capture status of the photothermal tweezers and sample information in the bright field. The bandpass filter is used to filter out the laser spot to facilitate the observation of the capture status in the bright field. The tube lens is used to focus the filtered light beam carrying the sample information to the center of the camera target surface.

2. The photothermal tweezers manipulation system based on multilayer MXene according to claim 1, characterized in that: The MXene photothermal response substrate consists of a glass substrate, a multilayer MXene two-dimensional material, a cover glass, and a PEG solution. The MXene two-dimensional material is deposited on the glass substrate by a wet transfer method, and the sample to be observed is diluted with a PEG solution and then dropped on the glass substrate where the MXene two-dimensional material is deposited.

3. The photothermal tweezers manipulation system based on multilayer MXene according to claim 2, characterized in that: The sample to be observed is PS microspheres or Escherichia coli or yeast cells.

4. The photothermal tweezers manipulation system based on multilayer MXene according to claim 2, characterized in that: The mass fraction of the PEG solution is 5-20%.

5. The photothermal tweezers manipulation system based on multilayer MXene according to claim 1, characterized in that: The wavelength range of the single-mode fiber laser is 532nm~1064nm.

6. The photothermal tweezers manipulation system based on multilayer MXene according to claim 1, characterized in that: The central wavelength of the bandpass filter is 605 nm and the bandwidth is 60 nm.

7. A control method using the photothermal tweezers control system based on multilayer MXene according to any one of claims 1 to 6, characterized in that: The single-mode fiber laser emits linearly polarized light which is focused onto the surface of the MXene substrate through a high-power objective lens. The MXene photothermal response substrate generates a local temperature gradient field under the excitation of the linearly polarized focused light. The PEG molecules undergo thermophoresis and migrate from the hot area to the cold area, thereby driving the micro-nanoparticles to move to the hot area, thereby realizing the controlled assembly of the micro-nanoparticles.

8. The photothermal tweezers manipulation method based on multilayer MXene according to claim 7, characterized in that: Under different laser powers and operation times, the capture and manipulation of single micro-nanoparticles and the aggregation and assembly of multiple nanoparticles can be achieved simultaneously.

9. The photothermal tweezers manipulation method based on multilayer MXene according to claim 7, characterized in that: By adjusting the laser power and the focus position of the light spot, it is possible to switch between different assembly modes of multiple nanoparticles, including hexagonal close-packed assembly, boundary assembly, and circular assembly.

10. The photothermal tweezers manipulation method based on multilayer MXene according to claim 7, characterized in that: When the sample to be observed is a biological sample, living manipulation of microorganisms can also be achieved.

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