Optical fiber end surface light-driven micro-gripper and preparation method thereof

Abstract

The invention discloses an optical fiber end surface light-driven micro-gripper and a preparation method thereof. The optical fiber end surface light-driven micro-gripper comprises an optical fiber flexible driving structure and a rigid skeleton structure; the optical fiber comprises a core and a cladding; the flexible driving structure comprises metal nanoparticles with light-heat conversion capability and a thermal responsive hydrogel structure, wherein the metal nanoparticles are embedded in the thermal responsive hydrogel structure; the rigid skeleton structure comprises a clamping structure and a supporting structure; when the optically driven micro-gripper is in a water environment below a critical response temperature, the micro-gripper opens when no light is passed through, and the micro-gripper closes after the optical fiber is passed through.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano devices and laser manufacturing, and relates to an optical fiber end surface light-driven micro-clamp and a preparation method thereof. Background Art

[0002] Optical fiber can achieve long-distance lossless transmission of light energy and optical signals. In addition, its slender and soft appearance and structure as well as its convenient and mature manufacturing process have shown great application value in medical detection and imaging in recent years. With the help of internal cavities of the human body (such as the intestines and blood vessels), optical fiber-based medical devices can help to implement interventional and minimally invasive surgeries, reducing the pain of patients during the operation. In order to make optical fiber have more functions, such as imaging, detection, and operation, it is often necessary to integrate a variety of micro devices at the far end of the optical fiber, that is, the end face of the optical fiber. However, due to the constraints of processing size and end face morphology, there are still many difficulties to overcome in the miniaturization, multi-functionalization, and industrialization of various functional components.

[0003] The cross-section of the fiber end face is a circular structure with a diameter of hundreds of microns, and the overall aspect ratio can reach more than 1000:1. Traditional micro-nano manufacturing processes require a closed processing space (such as electron beam etching EBL) or a flat processing substrate (such as micro-nano lithography), which is difficult to apply to the precise integration and micro-nano manufacturing of the fiber end face. The small size of the device and the optical fiber makes the subsequent alignment and integration also full of challenges. In particular, for complex devices such as the clamp with a driving structure and a supporting skeleton, the existing processing technology makes it difficult to achieve the manufacture of micro-nano devices with multiple materials and coexisting rigid and flexible structures. Summary of the invention

[0004] In view of this, the present invention discloses an optical fiber end-face light-driven micro-gripper and a preparation method thereof, which belongs to the field of micro-machining and includes the following steps: 1) preparation of two-photon processable hydrogel; 2) optical fiber end-face processing; 3) 3D two-photon laser printing of temperature-responsive driving structure; 4) 3D two-photon laser printing of three-dimensional skeleton structure; 5) in-situ laser single-photon reduction of metal particles to obtain a multi-material remote optically driven micro-gripper. The present invention combines two-photon processing with optical fiber in-situ reduction of metal particles to prepare a micro-gripper that can be remotely operated by light. The micro-gripper prepared by the present invention has extremely high biocompatibility and can be used in the direction of biomedicine.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] An optical fiber end surface light-driven micro-gripper, comprising:

[0007] A flexible driving structure, wherein the flexible driving structure comprises metal nanoparticles having light-heat conversion capability and a thermally responsive hydrogel structure, wherein the metal nanoparticles are embedded in the thermally responsive hydrogel structure;

[0008] A rigid skeleton structure, comprising a clamping structure and a supporting structure;

[0009] The flexible driving structure is coaxially connected to the core of the optical fiber at the cross section;

[0010] The rigid skeleton structure is connected to the flexible driving structure;

[0011] The flexible driving structure is stimulated by the photothermal effect, the metal nanoparticles absorb light energy, the temperature of the flexible driving structure rises, the water molecules in the thermal responsive hydrogel structure escape from the hydrogel, the volume of the flexible hydrogel driving structure decreases, and the clamping structure presents a closed state;

[0012] After the stimulation of the photothermal effect on the flexible driving structure disappears, the temperature of the flexible driving structure drops to the ambient temperature, water molecules re-enter the hydrogel, the volume of the flexible hydrogel driving structure expands, and the clamping structure end is in an open state.

[0013] The optical fiber end-face light-driven micro-gripper further comprises an optical fiber, and the optical fiber comprises a core and a cladding.

[0014] The optical fiber is used for light transmission; the thermal responsive hydrogel structure can undergo reversible expansion and contraction in response to temperature stimulation; the rigid skeleton structure does not respond to external stimulation and can cooperate with the driving structure to realize the grasping and releasing of objects.

[0015] When the light-driven micro-gripper is in a water environment below the critical response temperature, the micro-gripper opens when no light is passed through it, and the micro-gripper closes when the optical fiber passes through it.

[0016] The flexible driving structure is coaxially connected to the optical fiber core at the cross section.

[0017] The metal nanoparticles include Au and / or Ag.

[0018] The wavelength of the driving light source of the light-driven micro-gripper is determined by the absorption spectrum of the metal particles.

[0019] The present invention also provides a method for preparing an optical fiber end surface light-driven micro-gripper, comprising the following steps:

[0020] 1) dissolving N-isopropylacrylamide, a crosslinking agent, and a photoinitiator in a solvent to prepare a hydrogel solution;

[0021] 2) Surface treatment of the optical fiber end face;

[0022] 3) Laser printing of a thermally responsive hydrogel structure: dripping the hydrogel solution prepared in step 1) onto a substrate, suspending an optical fiber above the substrate and immersing the end face of the optical fiber in the hydrogel solution; adjusting the laser focus to locate the interface between the optical fiber and the hydrogel, importing the drawn model file into the software, adjusting the printing parameters, controlling the laser scanning path to print the hydrogel structure with the end face of the optical fiber as the base, and obtaining an optical fiber with a thermally responsive hydrogel structure on the end face;

[0023] 4) Printing a rigid skeleton structure: dripping photoresist on the substrate, suspending the optical fiber with a thermal responsive hydrogel structure on the end face prepared in step 3 above the substrate and immersing the end face of the optical fiber in the photoresist; adjusting the laser focus to locate the interface between the optical fiber and the hydrogel, importing the drawn model file into the software, adjusting the printing parameters, and obtaining an optical fiber with a thermal responsive hydrogel structure and a rigid skeleton structure on the end face;

[0024] 5) The optical fiber with the end face having the thermal responsive hydrogel structure and the rigid skeleton structure prepared in step 4) is immersed in a metal salt solution. After 10-20 minutes, a laser with a central wavelength in the range of 400-550 nm is introduced into the metal salt solution from the optical fiber. The laser power is 2.0-6.0 mW. After 1-10 seconds, the laser is turned off. The laser emitted from the fiber core is irradiated on the thermal responsive hydrogel structure. The metal ions absorb the light energy and are reduced to metal nanoparticles under the action of the reducing agent, which are evenly distributed in the thermal responsive hydrogel structure.

[0025] In step 5), the metal salt solution is an Au solution or an Ag solution.

[0026] The laser printing in step 3) and step 4) adopts 3D two-photon laser printing.

[0027] In step 1), the crosslinking agent is N,N-methylenebisacrylamide; and the photoinitiator is phenyllithium (2,4,6-trimethylbenzoyl) phosphonate.

[0028] In step 1), in the hydrogel solution, the mass percentage of N-isopropylacrylamide is 45-45wt%, the mass percentage of cross-linking agent N,N-methylenebisacrylamide is 4.0-8.4wt%, and the mass percentage of photoinitiator phenyllithium (2,4,6-trimethylbenzoyl) phosphonate is 0.5-2wt%.

[0029] The surface treatment process in step 2) is to cut the optical fiber into a flat end face, immerse it in a toluene solution of 3-(trimethoxysilyl)propyl methacrylate, and then rinse it with acetone and deionized water.

[0030] In step 4), the photoresist includes any one or more of IP-L780, IP-S, IP-Dip, and SU-8 photoresists.

[0031] The application of optical fiber end-face light-driven micro-gripper in the biomedical field also falls within the protection scope of the present invention.

[0032] The key point of the present invention is to provide a micro-gripper that can remotely and actively manipulate micron-sized target objects. The micro-gripper has the characteristics of a complex structure of multiple materials. The synergistic effect of intelligent response materials and metal particles enables the micro-gripper to be actively driven, and then integrated with flexible optical fibers to achieve remote driving; it is different from the compliant driving method of the prior art, which requires external force to realize the gripping function of the gripper and the operating range is restricted, such as the passive driving method of applying external force with side wall constraints or probes. The gripper in the present invention can be remotely actively optically driven; the key point of active driving is to process the intelligent material into a driving structure.

[0033] The present invention realizes the integrated manufacturing of a micro-gripper with a multi-material system on the end face of an optical fiber; through a composite manufacturing method of femtosecond laser two-photon three-dimensional integration and optical fiber end face single-photon reduction, the precise integration of micro-devices at the far end of the optical fiber is realized, thereby realizing the multifunctionality of the optical fiber.

[0034] The above-mentioned composite processing method is different from processing technologies such as photolithography and electron beam etching. These processing technologies are only applicable to the manufacture of large-area microstructures on a flat surface. It is difficult to achieve precise positioning and three-dimensional secondary integration for the processing of small-sized, non-planar substrates such as optical fiber end faces. Femtosecond laser two-photon processing technology uses the nonlinear absorption of materials to achieve three-dimensional molding of micro-nano structures. At the same time, the flexible positioning capability of the femtosecond laser focus can achieve secondary conformal processing of non-planar substrates.

[0035] In the above composite processing method, if the single-photon reduction generated by the optical fiber is changed to external irradiation, it is difficult to achieve the in-situ integration of nanoparticles inside the device. Nanoparticles exist inside the hydrogel material, and the hydrogel material exists inside the rigid support structure. Due to the complex configuration of the micro-gripper itself, it is difficult to achieve secondary integration of the internal materials by external irradiation. However, in the present invention, optical fiber is used to directly transmit light energy to the hydrogel flexible driving material at the end face of the fiber core, so as to achieve the in-situ reduction of metal nanoparticles without affecting the external skeleton structure.

[0036] Furthermore, by comparing the present invention with optical fiber end face manufacturing processes such as discharge, ablation, melting and the like, it is found that only the composite manufacturing method of the present invention of femtosecond laser two-photon three-dimensional integration and optical fiber end face single-photon reduction can achieve the manufacturing effect of complex three-dimensional micro-nano devices of multi-material systems.

[0037] In summary, the present invention has the following beneficial effects:

[0038] 1. The present invention solves the problem of functionalization of the far end of the optical fiber by adopting an additive manufacturing method of the optical fiber end face, and achieves the beneficial effect of light-driven micro-clamping precision operation;

[0039] 2. By adopting the single-double photon composite processing method of femtosecond laser and in-situ laser reduction, the preparation problem of multi-material three-dimensional microstructures was solved, and the integrated processing of micron-level multi-material three-dimensional devices was realized;

[0040] 3. By adopting the femtosecond laser manufacturing method, the technical problem of precise integration of micro-nano devices with special morphology of optical fiber end faces was solved, and beneficial effects were achieved in the field of optical fiber end face micro-grippers;

[0041] 3. The present invention realizes the in-situ reduction of metal nanoparticles inside the flexible driving structure surrounded by the micro-nano three-dimensional rigid skeleton structure through the optical fiber in-situ reduction method, thus solving the problem of secondary integration of materials inside the three-dimensional complex structure;

[0042] 4. The present invention adopts responsive smart materials as the driving structure to realize remote controllable optical active control technology, solving the problem of poor operability of compliant micro-grippers;

[0043] 5. The present invention relies on the optical fiber body to carry out the structural design, processing and control of the end face micro-gripper. With the help of the good flexibility of the optical fiber and the long-distance lossless transmission of light energy, the remote-driven end face functional micro-gripper operation is realized, which is expected to solve the micro-scale operation of small cavities in the body. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0045] Figure 1 is a schematic diagram of the opening of the optical control micro-gripper at the end face of the optical fiber;

[0046] Figure 2 is a schematic diagram of the closure of the optically controlled micro-gripper at the end face of the optical fiber;

[0047] Figure 3 is a scanning electron micrograph of silver nanoparticles on a thermally responsive actuated structure;

[0048] Figure 4 It is a performance characterization diagram of the optical fiber end-face light-driven micro-gripper manipulating a small ball and the repeatability of opening and closing. DETAILED DESCRIPTION

[0049] The present invention is described in detail below in conjunction with embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, some adjustments and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0050] Example 1

[0051] This embodiment 1 provides a fiber end surface light driven micro-gripper, such as Figure 1 shown.

[0052] The micro-gripper comprises:

[0053] An optical fiber, comprising a core and a cladding;

[0054] A flexible driving structure, wherein the flexible driving structure comprises two functional components, namely metal nanoparticles having light-heat conversion capability and a thermally responsive hydrogel structure, wherein the metal nanoparticles are embedded in the thermally responsive hydrogel structure;

[0055] A rigid skeleton structure comprises a clamping structure and a supporting structure.

[0056] The flexible driving structure is tightly connected coaxially with the optical fiber core at the cross section. The light source can be accurately irradiated at the end face of the core through the optical fiber to act on the flexible driving structure. The metal nanoparticles absorb the light energy at the outlet of the core and convert it into heat energy. The thermally responsive hydrogel structure is deformed due to the temperature increase caused by the metal nanoparticles. The water molecules in the hydrogel escape from the hydrogel network structure when the temperature rises, causing the volume of the flexible hydrogel driving structure to shrink.

[0057] The rigid skeleton structure is closely connected to the flexible driving structure. When the flexible driving structure changes shape due to the photothermal effect, it will pull the rigid structure to deviate and appear in a closed state on the extended clamping structure. On the contrary, when the light source is turned off, the photothermal nanoparticles no longer generate heat, the flexible driving structure returns to room temperature, and the water molecules re-enter the hydrogel, causing the volume to expand and appear in an open state at the end of the clamping structure. Based on this principle, the opening / closing of the optical fiber end micro-gripper can be realized by remote optical control. Figure 2 shown.

[0058] Example 2

[0059] This embodiment provides a method for preparing the optical fiber end surface micro-gripper described in Embodiment 1.

[0060] The optical fiber end surface micro-gripper is prepared by a femtosecond laser single-double photon integrated manufacturing method, and the specific steps are as follows:

[0061] 1. Fiber end face processing

[0062] A multimode optical fiber with a diameter of 250 μm was selected. After stripping the coating layer, the diameter was 125 μm. A fiber cleaver was used to cut a smooth end face. The cut fiber end face was immersed in a 1 mM toluene solution of 3-(trimethoxysilyl)propyl methacrylate. After one hour, it was rinsed with acetone and deionized water. After treatment, the adhesion between the fiber end face and the hydrogel can be improved.

[0063] 2. Femtosecond laser two-photon processing of hydrogel-driven microstructures

[0064] 1) Preparation of hydrogel solution

[0065] The reagents used include N-isopropyl acrylamide, a crosslinking agent, a photoinitiator and ethylene glycol, wherein the crosslinking agent is N,N-methylenebisacrylamide, and the photoinitiator is phenyl lithium (2,4,6-trimethylbenzoyl) phosphonate.

[0066] 400 mg of N-isopropylacrylamide, 40 mg of cross-linking agent N,N-methylenebisacrylamide, and 10 mg of photoinitiator phenyllithium (2,4,6-trimethylbenzoyl) phosphonate were dissolved in 450 μL of ethylene glycol, and ultrasonically dissolved in a 60°C water bath for 30 to 60 min. The solution was taken out and manually shaken every 5 to 10 minutes to allow it to be evenly dispersed to assist dissolution, thereby obtaining a hydrogel solution that can be used for femtosecond laser processing.

[0067] 2) Thermally responsive hydrogel structure A 780nm wavelength femtosecond laser is used as a light source to print a thermally responsive hydrogel structure. The hydrogel solution prepared in step 1) is dripped onto the substrate, and the optical fiber is suspended above the substrate using a clamp and the end face of the optical fiber is immersed in the hydrogel solution prepared in step 1). The laser focus is adjusted to the interface between the optical fiber and the hydrogel, and the drawn model file is imported into the software. The printing parameters are adjusted to control the scanning path of the laser to print the hydrogel structure with the end face of the optical fiber as the substrate, and an optical fiber with a thermally responsive hydrogel structure on the end face is obtained. In this embodiment, a 25x objective lens is used for processing, and the poly N-isopropylacrylamide (PNIPAM) hydrogel uses a laser power of 85mW and a scanning speed of 30mm / s. After printing, the end face of the optical fiber is immersed in deionized water for 10min for development, and the next step of printing is performed after drying;

[0068] 3. Femtosecond laser two-photon integrated three-dimensional rigid skeleton structure

[0069] Still using 780nm wavelength femtosecond laser as the light source, and selecting commercial photoresist IP-S, a three-dimensional rigid skeleton structure is integrated on the end face of the optical fiber with a thermal responsive hydrogel structure.

[0070] Drop photoresist on the substrate, suspend the optical fiber processed in step 2 above the substrate using a fixture and immerse the end face of the optical fiber in commercial photoresist IP-S to ensure that the end face of the optical fiber is between the hydrogel and the substrate, adjust the laser focus to the interface between the optical fiber and the hydrogel, import the drawn model file into the software, adjust the printing parameters, and obtain an optical fiber with a thermal responsive hydrogel structure and a rigid skeleton structure on the end face;

[0071] A 25x objective lens was used for processing, the IP-S used a laser power of 29mW, and a scanning speed of 100mm / s. After printing, the entire structure was immersed in propylene glycol methyl ether acetate (PGMEA) for 30min, and then immersed in isopropyl alcohol (IPA) for 2min for development;

[0072] 4. In-situ single-photon reduction of metal nanoparticles using optical fiber

[0073] Prepare a metal salt solution, dissolve 0.017g of AgNO3 solid in 1mL of deionized water, add ammonia water to titrate until the solution is just clear, then add 0.017g of sodium citrate, mix thoroughly to obtain a silver ammonia solution. Immerse the optical fiber with a thermally responsive hydrogel structure and a rigid skeleton structure at the end face in the silver ammonia solution, and after 10 minutes, pass a 405nm wavelength laser into the optical fiber with a laser power of 2.0 to 3.0mW. After 1s, turn off the laser, and the laser emitted from the fiber core directly irradiates the thermally responsive hydrogel structure. The metal Ag + The ions absorb light energy and are reduced to silver nanoparticles under the action of the reducing agent sodium citrate, which are evenly distributed in the thermoresponsive hydrogel structure, such as Figure 3 This method can realize the precise integration of various material systems in the fiber end face structure, solve the problem of confined space or planar process constraints in traditional processing, and help to realize the miniaturization and functionalization of medical devices.

[0074] Example 3

[0075] The optical fiber end face micro-gripper as described in Example 1 relies on the femtosecond laser single-double photon integrated manufacturing method provided by the present invention, and the specific implementation method is as follows.

[0076] 1. Fiber end face treatment. Select a multimode fiber with a diameter of 250μm, and after stripping the coating layer, it is 125μm. Use a fiber cleaver to cut a flat end face, and soak the cut fiber end face in a 1mM toluene solution of 3-(trimethoxysilyl) propyl methacrylate. After one hour, rinse it with acetone and deionized water. After treatment, the adhesion between the fiber end face and the hydrogel can be improved;

[0077] 2. Femtosecond laser two-photon processing of hydrogel-driven microstructures.

[0078] 1) Preparation of hydrogel solution

[0079] The reagents used include N-isopropyl acrylamide, a crosslinking agent, a photoinitiator and ethylene glycol, wherein the crosslinking agent is N,N-methylenebisacrylamide, and the photoinitiator is phenyl lithium (2,4,6-trimethylbenzoyl) phosphonate.

[0080] 400 mg of N-isopropylacrylamide, 40 mg of cross-linking agent N,N-methylenebisacrylamide, and 10 mg of photoinitiator phenyllithium (2,4,6-trimethylbenzoyl) phosphonate were dissolved in 450 μL of ethylene glycol, and ultrasonically dissolved in a 60°C water bath for 30 to 60 min. The solution was taken out and manually shaken every 5 to 10 minutes to allow it to be evenly dispersed to assist dissolution, thereby obtaining a hydrogel solution that can be used for femtosecond laser processing.

[0081] 2) Thermoresponsive hydrogel structure

[0082] A 780nm wavelength femtosecond laser is used as a light source to print a thermally responsive hydrogel structure. The optical fiber is suspended above the substrate using a fixture and the end face of the optical fiber is immersed in the hydrogel solution prepared in step 1). The laser focus is adjusted to the interface between the optical fiber and the hydrogel. The drawn model file is imported into the software, the printing parameters are adjusted, and the scanning path of the laser is controlled to print the hydrogel structure with the end face of the optical fiber as the substrate. A thermally responsive hydrogel structure is obtained on the end face of the optical fiber. In this embodiment, a 25x objective lens is used for processing, and the poly N-isopropylacrylamide (PNIPAM) hydrogel uses a laser power of 85mW and a scanning speed of 30mm / s. After printing, the end face of the optical fiber is immersed in deionized water for 10min for development, and the next step of printing is performed after drying;

[0083] 3. Femtosecond laser two-photon integrated three-dimensional rigid skeleton structure.

[0084] Still using 780nm wavelength femtosecond laser as light source, select commercial photoresist IP-L 780, integrate three-dimensional rigid skeleton structure on the end face of optical fiber with thermal responsive hydrogel structure, use fixture to suspend the optical fiber processed in step 2 above the substrate and immerse the end face of optical fiber in commercial photoresist IP-L 780, ensure that the end face of optical fiber is between hydrogel and substrate, adjust laser focus to the interface between optical fiber and hydrogel, import the drawn model file into software, adjust printing parameters, and prepare three-dimensional rigid skeleton structure. In this case, 25x objective lens is used for processing, IP-L 780 uses laser power of 34mW, scanning speed of 100mm / s, and after printing, the whole structure is immersed in propylene glycol methyl ether acetate (PGMEA) for 20min, and then immersed in isopropyl alcohol (IPA) for 2min for development;

[0085] 4. In situ single-photon reduction of metal nanoparticles using optical fiber.

[0086] Prepare a metal salt solution, dissolve 0.017g of AgNO3 solid in 1mL of deionized water, add ammonia water to titrate until the solution is just clear, then add 0.017g of sodium citrate, mix thoroughly to obtain a silver ammonia solution. Immerse the optical fiber with a thermally responsive hydrogel structure and a rigid skeleton structure on the end face prepared in steps 1-3 in the silver ammonia solution, and after 10 minutes, pass a 405nm wavelength laser into the optical fiber with a laser power of 2.0 to 3.0mW. After 1s, turn off the laser, and the laser emitted from the fiber core directly irradiates the thermally responsive hydrogel structure. The metal Ag + The ions absorb light energy and are reduced to silver nanoparticles under the action of the reducing agent sodium citrate, which are evenly distributed in the thermoresponsive hydrogel structure, such as Figure 3 This method can realize the precise integration of various material systems in the fiber end face structure, solve the problem of confined space or planar process constraints in traditional processing, and help to realize the miniaturization and functionalization of medical devices.

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 2 is that the thermal responsive poly N-isopropylacrylamide (PNIPAM) material of the driving structure is replaced with commercial IP-S photoresist. The obtained device structure meets the design of the micro-gripper, but because IP-S does not respond to external stimuli (i.e., volume changes), the micro-gripper cannot achieve the closing and opening actions, and thus cannot achieve the light-driven clamping function.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 2 is that after the micro-gripper is prepared, in-situ laser reduction is not used to embed the Ag particles (i.e., the single-double photon composite processing method required by the patent is not used). In this case, since the poly N-isopropylacrylamide (PNIPAM) material is temperature sensitive, the micro-gripper can only be opened and closed when the ambient (solution) temperature changes. This temperature control method, especially during medical surgery, will have a negative impact on tissues. Compared with the light-driven method, the temperature drive greatly reduces the universality of the micro-gripper.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 2 is that the micro-gripper is prepared on the guide wire, so it is necessary to consider the light energy transmission on the traditional guide wire, increase the preparation steps of the light-driven micro-gripper, introduce more operation links, and is not conducive to the device molding design.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Example 2 is that when the optical fiber in situ single-photon reduction of metal nanoparticles is carried out, the laser power is increased to 16 mW. After the optical fiber is passed through the light for 2 seconds, the laser cannot penetrate the thermally responsive hydrogel structure because too many silver nanoparticles are embedded in the flexible driving structure. Therefore, the hydrogel structure cannot shrink / expand under the switching of the laser, and accordingly, the micro-gripper cannot open or close.

[0095] Performance Testing

[0096] The micro-gripper of Example 2 is used for operational performance verification. The micro-gripper is precisely controlled by remotely controlling the light source switch, such as Figure 4 As shown. After the light source is turned on, the tip of the gripper deflects by about 10um, with repeatable control performance and good stability. According to the structural size setting, objects of different sizes can be grasped, such as those with a diameter range of 5 to 30um, which has important application value in precision medicine, minimally invasive surgery, and single-cell manipulation.

[0097] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An optical fiber end-face light-driven micro-gripper, characterized in that: include: A flexible driving structure, wherein the flexible driving structure comprises metal nanoparticles having light-heat conversion capability and a thermally responsive hydrogel structure, wherein the metal nanoparticles are embedded in the thermally responsive hydrogel structure; A rigid skeleton structure, comprising a clamping structure and a supporting structure; The flexible driving structure is coaxially connected to the core of the optical fiber at the cross section; The rigid skeleton structure is connected to the flexible driving structure; The flexible driving structure is stimulated by the photothermal effect, the metal nanoparticles absorb light energy, the temperature of the flexible driving structure rises, the water molecules in the thermal responsive hydrogel structure escape from the hydrogel, the volume of the flexible hydrogel driving structure decreases, and the clamping structure presents a closed state; After the stimulation of the photothermal effect on the flexible driving structure disappears, the temperature of the flexible driving structure drops to the ambient temperature, water molecules re-enter the hydrogel, the volume of the flexible hydrogel driving structure expands, and the clamping structure end is in an open state.

2. The optical fiber end-face light-driven micro-gripper according to claim 1, characterized in that: The optical fiber end-face light-driven micro-gripper further comprises an optical fiber, and the optical fiber comprises a core and a cladding.

3. The optical fiber end-face light-driven micro-gripper according to claim 1, characterized in that: The flexible driving structure is coaxially connected to the optical fiber core at the cross section.

4. The optical fiber end-face light-driven micro-gripper according to claim 1, characterized in that: The metal nanoparticles include Au and / or Ag.

5. A method for preparing the optical fiber end-face light-driven micro-gripper as claimed in claim 1, characterized in that: The steps include: 1) dissolving N-isopropylacrylamide, a crosslinking agent, and a photoinitiator in a solvent to prepare a hydrogel solution; 2) Surface treatment of the optical fiber end face; 3) Laser printing a thermally responsive hydrogel structure: dropping the hydrogel solution prepared in step 1) onto a substrate, suspending an optical fiber above the substrate and immersing the end face of the optical fiber in the hydrogel solution; The laser focus is adjusted to be positioned at the interface between the optical fiber and the hydrogel, the drawn model file is imported into the software, the printing parameters are adjusted, the scanning path of the laser is controlled to print the hydrogel structure with the optical fiber end face as the substrate, and an optical fiber with a thermally responsive hydrogel structure on the end face is obtained; 4) Printing a rigid skeleton structure: drop a photoresist on a substrate, suspend the optical fiber having a thermally responsive hydrogel structure on the end face prepared in step 3 above the substrate and immerse the end face of the optical fiber in the photoresist; The laser focus is adjusted to be positioned at the interface between the optical fiber and the hydrogel, the drawn model file is imported into the software, and the printing parameters are adjusted to obtain an optical fiber with a thermally responsive hydrogel structure and a rigid skeleton structure at the end face; 5) The optical fiber with the end face having the thermal responsive hydrogel structure and the rigid skeleton structure prepared in step 4) is immersed in a metal salt solution. After 10-20 minutes, a laser with a central wavelength in the range of 400-550nm is introduced into the metal salt solution through the optical fiber. The laser power is 2.0-6.0mW. After 1-10s, the laser is turned off. The laser emitted from the fiber core is irradiated on the thermal responsive hydrogel structure. The metal ions absorb the light energy and are reduced to metal nanoparticles under the action of the reducing agent, which are evenly distributed in the thermal responsive hydrogel structure.

6. The method for preparing the optical fiber end-face light-driven micro-gripper according to claim 5, characterized in that: In step 5), the metal salt solution is an Au solution or an Ag solution.

7. The method for preparing the optical fiber end-face light-driven micro-gripper according to claim 5, characterized in that: In step 1), the crosslinking agent is N,N-methylenebisacrylamide; and the photoinitiator is phenyllithium (2,4,6-trimethylbenzoyl) phosphonate.

8. The method for preparing the optical fiber end-face light-driven micro-gripper according to claim 5, characterized in that: In step 1), in the hydrogel solution, the mass percentage of N-isopropylacrylamide is 25-45wt%, the mass percentage of cross-linking agent N,N-methylenebisacrylamide is 4.0-8.4wt%, and the mass percentage of photoinitiator phenyllithium (2,4,6-trimethylbenzoyl) phosphonate is 0.5-2wt%.

9. The method for preparing the optical fiber end-face light-driven micro-gripper according to claim 5, characterized in that: The surface treatment process in step 2) is to cut the optical fiber into a flat end face, immerse it in a toluene solution of 3-(trimethoxysilyl)propyl methacrylate, and then rinse it with acetone and deionized water.

10. The method for preparing the optical fiber end-face light-driven micro-gripper according to claim 5, characterized in that: In step 4), the photoresist includes any one or more of IP-L780, IP-S, IP-Dip, and SU-8 photoresists.

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