A controllable transport device for inert particles and its usage method

Abstract

This invention provides a controllable transport device and method for inert particles, including a light spot projection structure, a sample stage, a particle carrier, and a camera. The particle carrier is placed on the sample stage, and the light spot projection structure is located below the sample stage, projecting a light spot onto the particle carrier. The camera is located above the sample stage. The particle carrier includes a photocatalytic film, a cover glass, and a gasket. The gasket is disposed between the photocatalytic film and the cover glass, and a cavity is provided in the center of the gasket. The cavity contains a mixed aqueous solution including fuel liquid and inert colloidal particles. This invention does not require the assistance of an external electric field; it only requires modification of the external excitation light source to enable it to generate microscale light spots through a solid mask or a micro-projector device. The device has a simple structure, is easy to operate, low in cost, and has good controllability.

Description

Technical Field

[0001] This invention belongs to the field of intelligent control technology, and in particular relates to a controllable transport device for inert particles and its usage method. Background Technology

[0002] At the microscale, technologies for transporting colloidal particles can be used for targeted delivery within the body or the controlled assembly of micro / nano structures in complex environments. Currently, the capture, directional assembly, and transport of inert colloidal particles are mainly achieved through optical tweezers, photoelectric tweezers, and acoustic tweezers. However, each of these methods has its limitations. For example, optical tweezers require the use of powerful lasers for excitation, photoelectric tweezers require specially designed optical guide substrates to form a special sandwich structure, increasing the difficulty of manipulation, while acoustic tweezers require complex acoustic design and precise control to generate a stable sound field. Summary of the Invention

[0003] The purpose of this invention is to provide a controllable transport device and method for inert particles, aiming to develop a low-cost, simple-to-operate particle manipulation and assembly technology applicable to multiple scenarios.

[0004] This invention is implemented as follows: a controllable transport device for inert particles includes a light spot projection structure, a sample stage, a particle carrier, and a camera. The particle carrier is placed on the sample stage, the light spot projection structure is located below the sample stage, and the light spot projection structure projects a light spot onto the particle carrier. The camera is located above the sample stage. The particle carrier includes a photocatalytic film, a cover glass, and a gasket. The gasket is disposed between the photocatalytic film and the cover glass, and a cavity is provided in the middle of the gasket. The cavity contains a mixed aqueous solution including fuel liquid and inert colloidal particles.

[0005] A further technical solution of the present invention is: the light spot projection structure includes a light spot projector, a first reflecting mirror and a first objective lens, the first objective lens, the first reflecting mirror and the sample stage are located on the same straight line, the first objective lens is disposed between the first reflecting mirror and the sample stage, the light spot projector is vertically disposed with respect to the first reflecting mirror, and the light spot emitted by the light spot projector is reflected to the sample stage by the first reflecting mirror.

[0006] A further technical solution of the present invention is that the wavelength of the light spot projected by the light spot projector is 365nm or 405nm.

[0007] A further technical solution of the present invention is that the parameters of the light spot include light intensity, shape of the light spot and moving speed of the light spot.

[0008] A further technical solution of the present invention is: the front end of the camera device is provided with a filter for filtering ultraviolet light, and a second objective lens is provided between the filter and the sample stage, and the camera device, the filter, the second objective lens and the sample stage are located on the same straight line.

[0009] A further technical solution of the present invention is as follows: the fuel liquid is selected from hydroquinone, ferrocene hydroxyl, triethanolamine, 2,2,6,6-tetramethylpiperidine nitrogen oxide, or hydrogen peroxide; when hydroquinone is selected as the fuel liquid, the concentration range of hydroquinone is 50-200 mM; when ferrocene hydroxyl is selected as the fuel liquid, the concentration range of ferrocene hydroxyl is 0.1-20 mM; when triethanolamine is selected as the fuel liquid, the concentration range of triethanolamine is 0.1-50 mM; when 2,2,6,6-tetramethylpiperidine nitrogen oxide is selected as the fuel liquid, the concentration range of 2,2,6,6-tetramethylpiperidine nitrogen oxide is 1-250 mM; when hydrogen peroxide is selected as the fuel liquid, the concentration range of hydrogen peroxide is 100-300 mM.

[0010] A further technical solution of the present invention is that the inert colloidal particles are silica particles or polystyrene particles.

[0011] A further technical solution of the present invention is: the photocatalytic thin film includes a glass slide, a substrate and a metal layer, the substrate is disposed on the top of the glass slide, the metal layer is disposed on the top of the substrate, the material of the substrate is titanium dioxide, and the material of the metal layer is platinum.

[0012] A further technical solution of the present invention is: it also includes a background light source and a second reflector, the second reflector and the first reflector are located on the same straight line, the second reflector is located below the first reflector, the background light source and the second reflector are vertically arranged, and the light from the background light source is reflected by the second reflector to the first reflector.

[0013] Another objective of this invention is to provide a method for using a controllable transport device for inert particles. A light spot projector projects light spots with different parameters. The light spots are focused onto the surface of the sample stage by a first objective lens. In the illuminated area, the titanium dioxide of the substrate is activated to generate photogenerated electrons and holes. Electrons migrate to the metal layer. The illuminated area induces the oxidation of hydroquinone by holes to generate hydrogen ions. On one side of the metal layer, electrons reduce benzoquinone, consuming hydrogen ions and generating an electric field from the illuminated area to the non-illuminated area. Under the action of this electric field, charged colloidal particles undergo electrophoresis. If the charged particles exhibit negative charge, they will migrate to the high potential area and the illuminated area; if the charged particles exhibit positive charge, they will migrate to the low potential area and the non-illuminated area.

[0014] The beneficial effects of this invention are as follows: Using the technical solution of this invention, based on the photosensitivity of the photocatalytic thin film, the structured assembly and directional transport of inert particles such as SiO2 particles are achieved using static and dynamic light spots. The transport efficiency and path can be controlled by changing the parameters of the dynamic light spot. Furthermore, it can also achieve controlled patterned assembly and real-time changes of colloidal particles. This invention does not require the assistance of other external electric fields, nor does it require the presence of other active particles in the solution. It only requires modifying the external excitation light source to generate microscale light spots through a physical mask or a micro-projector device, enabling the capture, directional transport, and patterned assembly of micro and nanoparticles. The device has a simple structure, is easy to operate, low in cost, and has good controllability; it can manipulate particles of multiple sizes to achieve structured assembly and transport; it can transport a large number of particles; in principle, multiple transport tasks can be performed simultaneously on particles at any position within the system. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the synthesis process of the TiO2 / Pt photocatalytic thin film according to an embodiment of the present invention;

[0016] Figure 2 These are morphology characterization data of the TiO2 / Pt photocatalytic thin film in an embodiment of the present invention;

[0017] Figure 3 These are characterization data of the composition and light absorption properties of the TiO2 / Pt photocatalytic thin film in an embodiment of the present invention.

[0018] Figure 4 This is a schematic diagram of the particle carrier according to an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of the physical mask and virtual light spot according to an embodiment of the present invention;

[0020] Figure 6 This is a schematic diagram of the virtual light spot generating device according to an embodiment of the present invention;

[0021] Figure 7 This is a schematic diagram of the interaction mechanism between the photocatalytic thin film and SiO2 particles in an embodiment of the present invention;

[0022] Figure 8 This is a schematic diagram of the photocatalytic thin film induced to assemble SiO2 particles under irradiation by static light spots of different sizes according to an embodiment of the present invention;

[0023] Figure 9 These are data on the change in the migration speed of colloidal particles with light intensity according to embodiments of the present invention;

[0024] Figure 10 These are data on the change in the migration velocity of colloidal particles with the fuel concentration in the solution according to an embodiment of the present invention;

[0025] Figure 11 These are data on the transport rate as a function of salt concentration in the solution, according to embodiments of the present invention.

[0026] Figure 12 This is data from an embodiment of the present invention for controlling the rate changes of particles of different materials;

[0027] Figure 13 This is data from an embodiment of the present invention for controlling the variation of the transport rate of SiO2 particles of different sizes;

[0028] Figure 14 These are the kinetic process data of the assembly of customized patterned SiO2 particles to form customized patterns according to embodiments of the present invention;

[0029] Figure 15 The customized font pattern SiO2 particles are assembled to form customized font data at the microscale in this embodiment of the invention;

[0030] Figure 16 This invention relates to a batch array pattern that induces the assembly of SiO2 particles to form a batch array structure at the microscale.

[0031] Figure 17 The data results of the directional transport of SiO2 particles induced by the dynamic light spot in the embodiment of the present invention are shown in Figure a, where Figure a is the trajectory of the dynamic light spot and Figure b is the enrichment result of SiO2 during the transport process at different times.

[0032] Figure 18 This is the movement path of the arc-shaped dynamic light spot in the embodiment of the present invention during the patterned assembly and real-time changes of SiO2 particles induced by high particle density.

[0033] Figure 19 This is a diagram showing the real-time changes in the patterned assembly of SiO2 particles at different times during the process of patterned assembly and real-time changes of the arc-shaped dynamic light spot induced by high particle density in an embodiment of the present invention.

[0034] Figure 20 This is the process by which a static hexagonal light spot constructed using a solid mask in an embodiment of the present invention induces 1μm PS particles to accumulate within the light spot;

[0035] Figure 21 This is an embodiment of the present invention showing the process of virtual static hexagonal light spot inducing 1μm PS particles to assemble into a patterned assembly and real-time changes, with the PS particle assembly patterned and changing in real-time at different times.

[0036] Figure descriptions: 1-Sample stage, 2-Light spot projector, 3-First reflecting mirror, 4-First objective lens, 5-Imaging equipment, 6-Filter, 7-Second objective lens, 8-Particle carrier, 9-Background light source, 10-Second reflecting mirror, 80-Photocatalytic thin film, 81-Cover glass, 82-Washer, 83-Cavity, 801-Slide, 802-Substrate, 803-Metal layer. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, and the terms "bottom surface," "top surface," "inner," and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0038] The present invention provides a controllable transport device for inert particles, comprising a light spot projection structure, a sample stage 1, a particle carrier 8, and a camera device 5. The particle carrier 8 is placed on the sample stage 1, the light spot projection structure is located below the sample stage 1 and projects a light spot onto the particle carrier 8, and the camera device 5 is located above the sample stage 1. The particle carrier 8 includes a photocatalytic film 80, a cover glass 81, and a gasket 82. The gasket 82 is disposed between the photocatalytic film 80 and the cover glass 81, and a cavity 83 is provided in the middle of the gasket 82. The cavity 83 contains a mixed aqueous solution including fuel liquid and inert colloidal particles.

[0039] Preferably, the light spot projection structure includes a light spot projector 2, a first reflecting mirror 3, and a first objective lens 4. The first objective lens 4, the first reflecting mirror 3, and the sample stage 1 are located on the same straight line. The first objective lens 4 is disposed between the first reflecting mirror 3 and the sample stage 1. The light spot projector 2 and the first reflecting mirror 3 are vertically arranged. The light spot emitted by the light spot projector 2 is reflected by the first reflecting mirror 3 to the sample stage 1.

[0040] Preferably, the wavelength of the light spot projected by the light spot projector 2 is 365nm or 405nm.

[0041] Prior to this, the parameters of the light spot include light intensity, light spot shape, and light spot movement speed.

[0042] Preferably, the front end of the camera device 5 is provided with a filter 6 for filtering ultraviolet light, and a second objective lens 7 is provided between the filter 6 and the sample stage 1. The camera device 5, the filter 6, the second objective lens 7 and the sample stage 1 are located on the same straight line.

[0043] Preferably, the fuel liquid is selected from one of hydroquinone, ferrocene hydroxyl, triethanolamine, 2,2,6,6-tetramethylpiperidine nitrogen oxide, or hydrogen peroxide; when hydroquinone is selected, the concentration range of hydroquinone is 50-200 mM; when ferrocene hydroxyl is selected, the concentration range of ferrocene hydroxyl is 0.1-20 mM; when triethanolamine is selected, the concentration range of triethanolamine is 0.1-50 mM; when 2,2,6,6-tetramethylpiperidine nitrogen oxide is selected, the concentration range of 2,2,6,6-tetramethylpiperidine nitrogen oxide is 1-250 mM; when hydrogen peroxide is selected, the concentration range of hydrogen peroxide is 100-300 mM.

[0044] Preferably, the inert colloidal particles are silica particles or polystyrene particles.

[0045] Preferably, the photocatalytic thin film 80 includes a glass slide 801, a substrate 802, and a metal layer 803. The substrate 802 is disposed on top of the glass slide 801, and the metal layer 803 is disposed on top of the substrate 802. The material of the substrate 802 is titanium dioxide, and the material of the metal layer 803 is platinum.

[0046] Preferably, it also includes a background light source 9 and a second reflector 10, the second reflector 10 and the first reflector 3 are located on the same straight line, the second reflector 10 is located below the first reflector 3, the background light source 9 and the second reflector 10 are vertically arranged, and the light from the background light source 9 is reflected by the second reflector 10 to the first reflector 3.

[0047] Another objective of this invention is to provide a method for using a controllable transport device for inert particles. A light spot projector 2 projects light spots with different parameters. The light spots are focused onto the surface of the sample stage 1 through a first objective lens 4. In the illuminated area, the titanium dioxide of the substrate 802 is activated to generate photogenerated electrons and holes. Electrons migrate to the metal layer 803. The illuminated area induces the oxidation of hydroquinone by holes to generate hydrogen ions. On one side of the metal layer 803, electrons reduce benzoquinone, consuming hydrogen ions and generating an electric field from the illuminated area to the non-illuminated area. Under the action of this electric field, charged colloidal particles undergo electrophoresis. If the charged particles exhibit negative charge, they will migrate to the high potential area and the illuminated area; if the charged particles exhibit positive charge, they will migrate to the low potential area and the non-illuminated area.

[0048] Example 1: The particle carrier 8 described in this example is as follows Figure 1 As shown, first cut 22*22cm 2Square glass slides were ultrasonically cleaned alternately with deionized water and anhydrous ethanol for 20 minutes, then dried in an oven for later use. The cleaned glass slide 801 was then placed at the bottom of the electron beam-deposited substrate 802, and an 80 nm thick layer of titanium was sputtered onto the surface of the substrate 802. Finally, the titanium-sputtered substrate 802 was annealed at 500 degrees Celsius for 2 hours in a muffle furnace to obtain a transparent light pink silica substrate 802. To improve the photocatalytic activity of the silica film, a layer of approximately 1 nm thick platinum was physically sputtered onto the surface of the heat-treated film. Because the sputtering amount was relatively low, the color of the film did not change significantly from a macroscopic perspective. Finally, a photocatalytic film 80 with a uniform surface and no obvious wrinkles was obtained. A gasket 82, made of silicone, was then bonded to the photocatalytic film 80 to form an experimental cavity with a diameter of 5 mm. A mixed aqueous solution containing different materials, such as polystyrene (PS) and silica (SiO2), or charged colloidal particles of different sizes (1, 2, 3, 4, 5, 10 μm) and hydroquinone (50-200 mM), is injected into the cavity 83. The cavity is then sealed by covering it with the coverslip 81.

[0049] The prepared particle carrier 8 is transferred to an inverted microscope or a sample stage 1 equipped with a structured light generation device. The light projection structure can project static or dynamic two-dimensional light spots of arbitrary shapes. Its core component is the light projector 2, which emits a single LED light source of 365nm or 405nm. This wavelength of light can activate the photocatalytic film 80 to undergo a photocatalytic reaction. By connecting the light projector 2 to a computer, the light projector 2 can be controlled to project light spots with different parameters. The light spots are focused onto the surface of the sample stage 1 by the first objective lens 4 below the sample stage 1. The light intensity of the illuminated area can be adjusted by built-in software or the RGB values ​​of the projected image. To clearly observe the sample stage 1 area, a background light source 9 is also installed in the optical path. The background light source 9 is a 660nm red LED light source; red light will not cause a reaction in the laser-catalyzed film 80. A second objective lens 7 and the camera device 5 are installed above the sample stage 1 to observe and record the motion behavior observed on the sample stage 1. Since strong violet light is required to activate the reaction in the experiment, the filter 6 is installed in front of the camera device 5 to filter out violet light and allow red light to pass through in order to prevent overexposure of violet light.

[0050] This embodiment uses SiO2 inert particles as an example to illustrate the mechanism of inert particle assembly and transport in the TiO2 / Pt photocatalytic film 80. First, it is necessary to explain the photocatalytic reaction process that occurs on the TiO2 / Pt surface under an excitation light source. If a stable patterned light spot is generated by structured light, the photocatalytic film 80 is not activated when the excitation light source is not turned on; only the platinum metal has a catalytic effect, but no effective reaction occurs. After the ultraviolet light spot is turned on, the titanium dioxide in the illuminated area is activated, generating photogenerated electrons and holes. Electrons easily migrate to the platinum metal. Therefore, in this process, the illuminated area induces the oxidation of hydroquinone by holes to produce hydrogen ions, while on the platinum side, electrons reduce benzoquinone, consuming hydrogen ions. This generates an electric field pointing from the illuminated area to the unilluminated area. Under the action of this electric field, charged colloidal particles undergo electrophoresis. If the charged particles exhibit negative charge, they migrate to the high potential region and the illuminated area; if the charged particles exhibit positive charge, they migrate to the low potential region and the unilluminated area. The separation efficiency of electrons and holes is highest and the reaction is most intense at the boundary between light spots, resulting in the largest electric field strength at the boundary. Figure 7 As shown.

[0051] Using the above-mentioned apparatus, the following experiment demonstrates the structured assembly of SiO2 inert microspheres through static light spot irradiation:

[0052] like Figure 14 As shown, SiO2 particles (tracer spheres) with a diameter of 1 μm are dispersed in an aqueous solution of hydroquinone. Subsequently, under continuous irradiation by a static light spot, it can be observed that more and more colloidal particles accumulate at the boundary of the irradiated area. After about one minute of irradiation, the colloidal particle assembly structure of the specified light spot will be revealed.

[0053] Furthermore, the moving speed and assembly result of the particles can be controlled by changing the parameters of the static light spot.

[0054] Adjusting the spot size to gradually increase it yields the following results: Figure 8 As shown, it can be seen that as the light spot becomes larger, the particles become more and more obviously concentrated at the edge of the light spot.

[0055] Adjusting the light intensity and gradually increasing it yields the following results: Figure 9 As shown, it can be seen that as the light intensity increases, the particles move into the light spot faster.

[0056] The concentration of hydroquinone in the solution was adjusted and gradually increased, and the results were as follows. Figure 10 As shown, the speed at which particles move into the light spot will first increase and then decrease.

[0057] Adjusting the ionic strength of the solution to gradually increase it, the results are as follows: Figure 11As shown, the speed at which particles move into the light spot gradually decreases.

[0058] The state of the light spot is adjusted from a static light spot to a dynamic light spot, causing it to move directionally at a certain speed. The result is as follows: Figure 17 and Figure 18 As shown, the particles exhibit directional movement and accumulation following the direction of the light spot's movement. Figure 17 and Figure 18 It is the result of the assembly of 3μm microspheres.

[0059] The particle density of the inert particles inside the cavity was adjusted to gradually increase, and the result was as follows. Figure 19 As shown, when the particle density is low, the colloidal particles will move directionally along the direction of the light spot; when the particle density is high, the colloidal particles will aggregate and assemble in situ as the light spot moves, thereby achieving real-time display of the pattern. Figure 19 It is the result of the assembly of 3μm SiO2 particles.

[0060] Furthermore, for the photocatalytic thin film 80, parameters such as the shape, size, and movement speed of the light spot are controlled to induce the regional combination and patterned display of inert particles, such as... Figure 14 As shown, under a customized light spot, the photocatalytic film 80 can combine with the patterned light spot to induce inert particles to exhibit customized colloidal assembly.

[0061] Example 2: Based on Example 1, this example uses inert colloidal particles, specifically PS particles. A static light spot can induce the PS colloidal particles to move into the light spot. Figure 20 As shown, comparing before and after illumination, after 1 minute, the relative density of PS particles within the light spot increases compared to before illumination, which can also induce particle assembly to form customized patterns, such as... Figure 21 visible.

[0062] The fuel liquid can be composed of various solutions such as hydroquinone, ferrocene hydroxyl, triethanolamine, 2,2,6,6-tetramethylpiperidine nitrogen oxides, or hydrogen peroxide. The concentration range varies depending on the specific solution component. For example, when hydroquinone is used, the concentration range is 50-200 mM; when ferrocene hydroxyl is used, the concentration range is 0.1-20 mM; when triethanolamine is used, the concentration range is 0.1-50 mM; and when 2,2,6,6-tetramethylpiperidine nitrogen oxides is used, the concentration range is 1-250 mM. Finally, hydrogen peroxide solution can also be used, with a specific concentration range of 100-300 mM. The current implementation plan indicates that various solution systems can be used in this experimental system, demonstrating broad applicability.

[0063] Based on the experimental results of the above embodiments, this technology can be used to assist in biological detection. For example, it can be used to manipulate and enrich analytes at low concentrations in a sample to enhance the detection signal. It can also be used to manufacture a microfluidic device for the controllable assembly of colloids to obtain functional materials with different optical and mechanical properties. Examples include the preparation of structures with structural colors and the fabrication of gratings.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A controllable transport device for inert particles, characterized in that, The device includes a light projection structure, a sample stage, a particle carrier, and a camera. The particle carrier is placed on the sample stage, and the light projection structure is located below the sample stage, projecting a light spot onto the particle carrier. The camera is located above the sample stage. The particle carrier includes a photocatalytic film, a cover glass, and a gasket. The gasket is disposed between the photocatalytic film and the cover glass, and has a cavity in its center containing a mixed aqueous solution comprising fuel liquid and inert colloidal particles. The inert colloidal particles are silica particles or polystyrene particles. The photocatalytic film includes a glass slide, a substrate, and a metal layer. The substrate is disposed on top of the glass slide, and the metal layer is disposed on top of the substrate. The substrate is made of titanium dioxide, and the metal layer is made of platinum.

2. The controllable transport device for inert particles according to claim 1, characterized in that, The light spot projection structure includes a light spot projector, a first reflecting mirror, and a first objective lens. The first objective lens, the first reflecting mirror, and the sample stage are located on the same straight line. The first objective lens is disposed between the first reflecting mirror and the sample stage. The light spot projector is vertically disposed with respect to the first reflecting mirror. The light spot emitted by the light spot projector is reflected by the first reflecting mirror to the sample stage.

3. The controllable transport device for inert particles according to claim 2, characterized in that, The wavelength of the light spot projector is 365nm or 405nm.

4. The controllable transport device for inert particles according to claim 2, characterized in that, The parameters of the light spot include light intensity, shape of the light spot, and movement speed of the light spot.

5. The controllable transport device for inert particles according to claim 1, characterized in that, The front end of the camera device is equipped with a filter for filtering ultraviolet light, and a second objective lens is provided between the filter and the sample stage. The camera device, the filter, the second objective lens and the sample stage are located on the same straight line.

6. The controllable transport device for inert particles according to claim 1, characterized in that, The fuel liquid is selected from one of hydroquinone, ferrocene hydroxyl, triethanolamine, 2,2,6,6-tetramethylpiperidine nitrogen oxide, or hydrogen peroxide; when hydroquinone is selected, the concentration range of hydroquinone is 50-200 mM; when ferrocene hydroxyl is selected, the concentration range of ferrocene hydroxyl is 0.1-20 mM; when triethanolamine is selected, the concentration range of triethanolamine is 0.1-50 mM; when 2,2,6,6-tetramethylpiperidine nitrogen oxide is selected, the concentration range of 2,2,6,6-tetramethylpiperidine nitrogen oxide is 1-250 mM; when hydrogen peroxide is selected, the concentration range of hydrogen peroxide is 100-300 mM.

7. The controllable transport device for inert particles according to claim 2, characterized in that, It also includes a background light source and a second reflector. The second reflector is located on the same line as the first reflector and is located below the first reflector. The background light source and the second reflector are vertically arranged. The light from the background light source is reflected by the second reflector to the first reflector.

8. A method of using the controllable transport device for inert particles according to any one of claims 1-7, characterized in that, A light spot projector projects light spots with different parameters. The light spots are focused onto the sample stage surface through a first objective lens. In the illuminated area, the titanium dioxide of the substrate is activated to generate photogenerated electrons and holes. Electrons migrate to the metal layer, and the illuminated area induces the oxidation of hydroquinone by holes to generate hydrogen ions. On the metal layer side, electrons reduce benzoquinone, consuming hydrogen ions and generating an electric field from the illuminated area to the non-illuminated area. Under the action of this electric field, charged colloidal particles undergo electrophoresis. If the charged particles exhibit negative charge, they will migrate to the high potential area and the illuminated area; if the charged particles exhibit positive charge, they will migrate to the low potential area and the non-illuminated area.

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