Light-driven automatic centering rotary micro-nano motor on solid interface

Abstract

The invention relates to a light-driven automatic centering rotary micro-nano motor on a solid interface, which is in a sheet shape with a center rotationally symmetrical and a non-rotating-shaft radially symmetrical structure, and is formed by laser processing of a metal nano material. Normal capturing force pointing to the center of the structure and tangential force in the parallel cantilever direction are accumulated in the pulse duration time, and then rotating torque is output for automatic centering rotation. And a strong output torque (more than 1nN. M) is generated, and the torque is more than 2 orders of magnitude higher than that of a common electrostatic motor in the MEMS at present. Due to the characteristic of small size, the torque density is up to 0.1 N.m / mm < 3 >, and the torque mass ratio is up to 100N.m / kg. By changing parameters such as laser power, repetition frequency, light spot shape and size and the like, accurate rotation control of the micro-nano motor can be realized. The optical tweezer has the advantages of being simple in structure, suitable for working conditions of a solid interface, free of thermal damage and the like, can achieve automatic centering rotation of the micro-nano motor on the solid interface, is used for driving other nano parts and operating target objects, is highly matched and compatible with existing optical tweezer equipment, and is wide in application range.

Description

Technical Field

[0001] The invention relates to the technical field of nano-electronic machinery, and in particular to an optically driven automatic centering rotating micro-nano motor on a solid interface. Background Art

[0002] In recent years, with the rapid development of current technology, academia and industry have shown great interest in the design and construction of micro-machines and nano-machines. In the new generation of nano-electromechanical systems, rotary motors that have been widely used at the macroscopic scale have become important basic components and building elements. However, the current challenges in design and manufacturing limit the expansion of existing micro-electromechanical systems to nano-electromechanical systems. More importantly, at the nanoscale, cubic dimension forces (such as inertial forces, piconewtons) are much smaller than square dimension forces (surface friction and adhesion, micronewtons), so overcoming the motion resistance dominated by square dimension forces has become the key to realizing rotary micro-nanomotors. Traditional technologies that overcome cubic dimension forces to drive objects, such as electrostatic and electromagnetic motors, have limited output capacity and small output torque, usually only in the order of pNm, and the structural size is generally tens of microns to hundreds of microns. In addition, these technologies require a large driving voltage and are not stable enough. At the nanoscale, as the adhesion force increases, they can no longer provide sufficient output to overcome the interface resistance. In addition, although piezoelectric actuators can achieve precise control at the nanoscale, their size is usually not nanoscale, but still has a macroscopic size.

[0003] In comparison, optical manipulation methods such as optical tweezers have strong driving capabilities at the nanoscale, and are non-contact and precisely controlled, which can solve the problems of low power and motion control at the same time. Unlike traditional mechanical designs with rotors and stators, traditional optical rotors rely on angular momentum exchange (including orbits or spins) as the source of driving force, and their output force is only in the order of piconewtons, which cannot meet the needs of overcoming surface resistance (micronewtons) and stably outputting strong torque. In 2010, an optical motor based on surface plasmon mode was reported and attracted widespread attention. However, it has a strong selectivity for the wavelength of excitation light, and the output torque is only 140pN·nm, which is far from overcoming the solid interface resistance and achieving rotation. In addition, traditional optical rotors also require multi-point capture and guidance to achieve motion control, which makes the system extremely complex. In contrast, static light spots have become a better choice of driving source. Summary of the invention

[0004] In view of the problems of current micro-nanoscale rotary motors such as limited working environment, small output torque, high rotation speed and difficulty in achieving precise small-angle control, a light-driven automatic centering rotary micro-nano motor on a solid interface is proposed. It is based on the underlying innovative principle of photothermal tweezers, that is, by breaking the symmetry of simple nanostructures, it achieves automatic centering rotation of the nanostructure under static pulsed light.

[0005] The technical solution of the present invention is: a light-driven automatic centering rotating micro-nano motor on a solid interface, comprising a control unit and a micro-nano motor, wherein the control unit comprises a host computer, a laser module and an image recognition module;

[0006] The host computer sets the control parameters of each component of the laser module to control the output of the laser pulse;

[0007] The laser module generates a control laser pulse, which is incident on the control platform to form a capture spot to control the micro-nano motor;

[0008] The micro-nano motor has a sheet-like structure with central rotational symmetry and non-rotational radial symmetry, and is made of metal nanomaterials processed by laser. During the pulse duration, it accumulates a normal capture force pointing to the center of the structure and a tangential force parallel to the cantilever direction, thereby outputting a rotational torque to automatically rotate in a centered manner.

[0009] The image recognition module performs real-time imaging, obtains the image of the micro-nano motor, obtains the current rotation angle of the micro-nano motor through edge detection image recognition, and feeds back to the host computer to achieve real-time modulation of the parameters of the laser module.

[0010] Preferably, the laser used in the laser module is a pulsed light laser, which is modulated by a host computer to output a short pulse laser control signal with a period and pulse width, and the output wavelength, repetition frequency, pulse width and power are all controlled in real time by the host computer.

[0011] Preferably, the output wavelength of the laser module is determined according to the absorption band of the micro-nano motor material, the repetition frequency range is ≤400kHz, and the pulse width range is 50fs-500μs.

[0012] Preferably, the laser module outputs laser pulse repetition frequency, spot size and average power to achieve rotation speed control of the micro-nano motor.

[0013] Preferably, the metal nanomaterial of the micro-nano motor is a metal material with high photothermal absorption and thermal expansion properties.

[0014] Preferably, the micro-nano motor is in the shape of a windmill structure that satisfies automatic centering rotation.

[0015] Preferably, the size of the micro-nano motor is controlled to be less than 1 mm, and the thickness is controlled to be less than 5 μm.

[0016] Preferably, the capture light spot uses a spatial light modulator to select its shape and intensity distribution according to the structure and size of the micro-nano motor to drive the micro-nano motor.

[0017] Preferably, the solid interface is a gas-solid interface, a liquid-solid interface or a solid interface under a vacuum environment.

[0018] Preferably, the solid interface is a solid substrate, which is any one of quartz, fused quartz, magnesium fluoride, glass, oxide layer silicon wafer, mica, lithium niobate film, sapphire, silicon nitride, optical fiber end face, and integrated waveguide end face.

[0019] The beneficial effects of the present invention are as follows: the light-driven self-centering rotating micro-nano motor on the solid interface of the present invention has flexible material selection, and metal materials (such as gold, silver, palladium, copper, aluminum, etc.) can all be used to construct the light-driven self-centering rotating micro-nano motor based on the principle of photothermal tweezers. The structural processing method is not limited to laser processing, and a variety of micro-nano processing technologies such as electron beam exposure, ion beam etching, and traditional photolithography technology can also be applied. The preparation method is highly versatile and easy to operate; the micro-nano motor has rich shape designs, and micro-nano structures with rotationally symmetric and non-axisymmetric shapes can achieve the goal; the control system has a simple structure, is easy to build, and is highly compatible with the existing optical tweezers system. Compared with traditional systems, the present invention also has the advantages of low excitation power, low and easy to adjust rotation speed, high precision, no thermal damage, high repeatability, stable rotation, and applicability to solid-state interfaces; it can overcome the friction resistance generated by direct contact between the micro-nano motor and the contact surface, and use the asymmetry of its structure to generate a powerful output torque, which can complete its own rotation or drive other micro-nano objects to rotate. Therefore, the present invention expands the application scenarios of traditional motors and has greater flexibility and development potential; it can realize computer feedback control through image recognition to ensure control accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural block diagram of the light-driven self-centering rotating micro-nano motor on the solid interface of the present invention;

[0021] Figure 2 Dark field optical images of micro-nanomotors of different structural shapes of the present invention;

[0022] Figure 3 The optical images of the micro-nano motor of the present invention before and after the centering rotation on the end face of the optical fiber;

[0023] Figure 4 A schematic diagram of measuring angle and angular velocity by image recognition of the present invention;

[0024] Figure 5 It is a structural schematic diagram of the feedback part of the image recognition module of the present invention;

[0025] Figure 6 Optical sequential photos of the centering rotation and moving rotation of the micro-nano motor of the present invention. Specific embodiments

[0026] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives the detailed implementation manner and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0027] The underlying innovative principle of the photo-thermal tweezer of the present invention is: utilizing the photo-thermal effect of micro-nano objects, under the excitation of pulsed laser, converting light energy into heat energy, causing rapid thermal expansion inside it, and the transient thermal expansion generates a rapid impact load on the inside of the object. For micro-nano structures with central rotational symmetry and non-radial symmetry about the rotation axis (such as the "卍" shape), during the pulse duration, a sufficiently large normal capture force pointing to the center of the structure and a tangential force parallel to the cantilever direction will be accumulated, and then a rotational torque will be output, enabling the micro-nano structure to automatically center and rotate under the capture of the center of the light spot. By changing the position of the light spot or the substrate, further control of the combined movement of the micro-nano object moving and rotating on the solid interface can be achieved.

[0028] As Figure 1 shown in the structural block diagram of the optically driven automatic centering rotation micro-nano motor on the solid interface, which includes a control unit and a micro-nano motor 3. The control unit includes a host computer 1, a laser module 2, and an image recognition module 4;

[0029] The host computer 1 is used to set the control parameters (including wavelength, repetition frequency, pulse width, and power) of each component of the laser module 2 to achieve the control of the output of the laser pulse;

[0030] The laser module 2 is used to generate a control laser pulse, which is incident on the control platform to form a capture light spot to control the micro-nano motor 3;

[0031] The micro-nano motor 3 is made of metal nano materials (such as gold, silver, palladium, copper, aluminum, etc.) through laser processing;

[0032] The image recognition module 4 is used for real-time imaging, acquiring images and obtaining the current rotation angle of the micro-nano motor through edge detection image recognition, and feeding it back to the host computer 1 to realize the real-time modulation of the parameters of the laser module 2.

[0033] The laser selected by the laser module 2 is a pulsed light laser, which is modulated by the host computer 1 to output a short-pulse laser control signal with a specific period and pulse width (the user can choose different periods and pulse widths and set specific values ​​according to their different requirements for speed, accuracy, etc.), and the output wavelength, repetition frequency, pulse width and power are all controlled in real time by the host computer 1. In some embodiments, the wavelength of the laser module 2 is 532nm, the repetition frequency is 12kHz, and the pulse width is 15ns, but not limited to this. The output wavelength is determined according to the absorption band of the micro-nano motor material, the laser wavelength range is 300nm-2μm, the repetition frequency range is ≤400kHz, and the pulse width range is 50fs-500μs. In some embodiments, the speed control of the micro-nano motor can be achieved by adjusting the repetition frequency, spot size and average power of the laser pulse in the laser module 2.

[0034] The micro-nano motor 3 is in the shape of a sheet with central rotational symmetry and non-rotational radial symmetry, and is made of metal material, such as Figure 2 Dark field optical images of micro-nano motors with different structural shapes are shown. The micro-nano motor structure can be processed by laser. Figure 2 The size of the motor is 10 μm and the thickness is 100 nm. However, it is not limited to this. Structures of other sizes and thicknesses (size controlled below 1 mm and thickness controlled below 5 μm) can also achieve the goal. In some embodiments, the material of the micro-nano motor 3 is gold, but it is not limited to this. Other metal materials with good light and heat absorption and thermal expansion properties (such as silver, palladium, copper, aluminum, etc.) can meet the material requirements for constructing micro-nano motors. In some embodiments, the micro-nano motor 3 is in the shape of a swastika, but it is not limited to this. Other micro-nano structures with central rotational symmetry and non-rotational axis radial symmetry, such as windmill-shaped structures, can also meet the control requirements of automatic centering rotation.

[0035] The diameter of the capture light spot in the specific embodiment is in the range of 5-15 μm, and is a circular Gaussian light spot, but is not limited thereto. Light spots of other shapes and intensity distributions can be selected for driving using a spatial light modulator according to the specific motor structure and size.

[0036] In the specific embodiments, the solid interface is the interface between air and substrate, but it is not limited thereto. Other gas-solid interfaces, liquid-solid interfaces or solid interfaces in a vacuum environment can also achieve the same goal.

[0037] The solid substrate is quartz and fused quartz in the specific embodiment, but is not limited thereto. Common solid substrates such as magnesium fluoride, glass, oxide layer silicon wafer, mica, lithium niobate film, sapphire, silicon nitride, optical fiber end face, integrated waveguide end face and the like can also achieve the same goal. Figure 3Optical image of the micro-nano motor on the fiber end face shown. The size of the motor is 10 μm and the thickness is 100 nm. The left figure is the optical photo of the micro-nano motor on the fiber end face. The red dashed line indicates the area of the fiber core. The middle and right figures are the optical images of the micro-nano motor before and after centering rotation respectively.

[0038] The image recognition module 4 is used for angle recognition, such as Figure 4 Schematic diagram of the image recognition for measuring the angle and angular velocity shown. An image is acquired and the current rotation angle of the micro-nano motor is roughly measured through edge detection image recognition. The edge of the motor structure in the acquired image is directed to a high-precision recognition area rotated to about 45°, which can further improve the accuracy of the measured angle.

[0039] The image recognition module 4 is used for real-time imaging, such as Figure 5 Schematic diagram of the structure of the feedback part of the image recognition module shown. An image of the micro-nano motor is acquired and the current rotation angle of the micro-nano motor 3 is obtained through edge detection image recognition. The rotation speed can be obtained by multiple step measurements. Whether to stop the loop is selected by comparing the current angle with the target angle. The ratio of the difference value to the rotation speed is fed back to the host computer 1 to adjust the parameters of the laser module 2, so that the angle of the micro-nano motor 3 gradually approaches the target angle until the target angle is reached and the loop ends. Specific embodiment 1:

[0041] Method for the in-situ rotation of the optically-driven auto-centering rotating micro-nano motor on a solid interface:

[0042] Such as Figure 6 As shown in the left figure, the卍micro-nano motors are dispersed on the operation platform. Due to the adsorption effect between the micro-nano motors and the substrate, they are static on the substrate surface. Through the host computer module, the laser module is modulated to output a pulsed laser signal with a wavelength of 532 nm, a repetition frequency of 6 kHz, a pulse width of 10 ns, and an average power of 120 μW. Then the laser beam is focused into a spot with a diameter of 9 μm through an objective lens. When the spot acts on the geometric center of the micro-nano motor with a side length of 8 μm, the motor will automatically center and rotate clockwise ( Figure 5 The white dots in the figure mark the endpoints of the same rotating arm of the micro-nano motor), until the driving laser is turned off. Under the continuous action of the laser, the micro-nano motor will continue to rotate. The current angle can be obtained through image recognition by taking a screenshot after turning off the laser, and it is fed back to the host computer by comparing with the target angle. The above step rotation steps are continuously repeated until the target angle is reached. Specific embodiment 2:

[0044] Method for the moving rotation of the optically-driven auto-centering rotating micro-nano motor on a solid interface:

[0045] Such as Figure 6As shown in the right figure, the sample in Example 1 is dispersed on the operating platform and readjusted to the focal plane. A pulsed laser signal of 532nm, repetition frequency of 6kHz, pulse width of 10ns, and average power of 120μW is focused into a spot with a diameter of 9μm through the objective lens and applied to the center of the micro-nano motor. The operating platform is moved, and the micro-nano motor will automatically rotate while capturing.

[0046] The above-mentioned implementation modes are preferred cases of the present invention and should not be understood as limiting the scope of the patent application. As long as they do not violate the concept of the present invention (the underlying principle of photothermal tweezers innovation), all technical inventions that are the same or similar to the present invention shall fall within the protection scope of the present invention.

[0047] The micro-nano motor is prepared by vapor deposition and processed into a specific shape by laser. Metal micro-nano materials (such as gold, silver, palladium, copper, aluminum, etc.) grown by other methods (such as liquid phase growth) or processed by other methods (such as electron beam exposure, ion beam etching, traditional photolithography technology, etc.) with central rotational symmetry and non-rotational axis radial symmetry can also meet the needs of constructing micro-nano motors.

[0048] The laser module in the control system outputs light pulses which are regulated by electrical control (such as a signal generator), and the excitation light pulses may also be regulated by other means, such as a chopper.

[0049] The proposed light-driven self-centering rotary micro-nano motor on a solid interface has a low speed and is easy to control. It can generate a strong output torque (more than 1nN·m), which is far higher than all types of micro-nano motors reported so far, and is more than 2 orders of magnitude higher than the torque of the electrostatic motor commonly used in MEMS. Due to its small size, its torque density is as high as 0.1N·m / mm 3 , the torque-to-mass ratio is as high as 100N·m / kg. Further, by changing the parameters such as laser power, repetition frequency, spot shape and size, precise rotation control of the micro-nano motor can be achieved. The light-driven automatic centering rotation micro-nano motor described in the present invention has the advantages of large output torque, low and easy adjustable speed, fine angle control, suitable for working conditions of solid-state interface and no thermal damage. It can realize the self-centering rotation of the micro-nano motor on the solid interface and be used to drive other nano components and operate target objects. It is highly matched and compatible with existing optical tweezers equipment and has a wide range of applications.

[0050] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A light-driven self-centering rotary micro-nano motor on a solid interface, characterized in that: It includes a control unit and a micro-nano motor. The control unit includes a host computer, a laser module and an image recognition module. The host computer sets the control parameters of each component of the laser module to control the output of the laser pulse; The laser module generates a control laser pulse, which is incident on the control platform to form a capture spot to control the micro-nano motor; The micro-nano motor has a sheet-like structure with central rotational symmetry and non-rotational radial symmetry, and is made of metal nanomaterials processed by laser. During the pulse duration, it accumulates a normal capture force pointing to the center of the structure and a tangential force parallel to the cantilever direction, thereby outputting a rotational torque to automatically rotate in a centered manner. The image recognition module performs real-time imaging, obtains the image of the micro-nano motor, obtains the current rotation angle of the micro-nano motor through edge detection image recognition, and feeds back to the host computer to achieve real-time modulation of the parameters of the laser module.

2. The light-driven self-centering rotary micro-nano motor on a solid interface according to claim 1, characterized in that: The laser used in the laser module is a pulsed light laser, which is modulated by a host computer to output a short pulse laser control signal with a period and pulse width, and the output wavelength, repetition frequency, pulse width and power are all controlled in real time by the host computer.

3. The light-driven self-centering rotary micro-nano motor on a solid interface according to claim 2, characterized in that: The output wavelength of the laser module is determined according to the absorption band of the micro-nano motor material, the repetition frequency range is ≤400kHz, and the pulse width range is 50fs-500μs.

4. The self-centering rotating micro-nano motor driven by light on a solid interface according to claim 2 or 3, characterized in that: The laser module outputs the repetition frequency, spot size and average power of the laser pulse to achieve the rotation speed control of the micro-nano motor.

5. The light-driven self-centering rotary micro-nano motor on a solid interface according to claim 4, characterized in that: The metal nanomaterial of the micro-nano motor is a metal material with high light-heat absorption and thermal expansion performance.

6. The light-driven self-centering rotary micro-nano motor on a solid interface according to claim 5, characterized in that: The micro-nano motor is in the shape of a windmill structure capable of automatically centering rotation.

7. The light-driven self-centering rotary micro-nano motor on a solid interface according to claim 6, characterized in that: The size of the micro-nano motor is controlled to be less than 1 mm, and the thickness is controlled to be less than 5 μm.

8. The light-driven self-centering rotary micro-nano motor on a solid interface according to claim 7, characterized in that: The capture light spot uses a spatial light modulator to select its shape and intensity distribution according to the structure and size of the micro-nano motor to drive the micro-nano motor.

9. The self-centering rotating micro-nano motor driven by light on a solid interface according to any one of claims 5 to 8, characterized in that: The solid interface is a gas-solid interface, a liquid-solid interface or a solid interface under a vacuum environment.

10. The light-driven self-centering rotary micro-nano motor on a solid interface according to claim 9, characterized in that: The solid interface is a solid substrate, which is any one of quartz, fused quartz, magnesium fluoride, glass, oxide layer silicon wafer, mica, lithium niobate film, sapphire, silicon nitride, optical fiber end face, and integrated waveguide end face.

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