A biomimetic adhesion-based single-arm optical waveguide micro gripper

Abstract

This invention relates to the field of femtosecond laser micro / nano fabrication technology, and discloses a biomimetic adhesion-based single-arm optical waveguide micro-gripper, comprising: an optical fiber body for conducting excitation light, the optical fiber body including a core and a cladding; and a single-arm flexible waveguide driving structure, the bottom end of which is directly and integrally integrated into the center of the core end face of the optical fiber body. The refractive index of the single-arm flexible waveguide driving structure satisfies the optical waveguide transmission conditions, allowing the light beam emitted from the core to propagate directly within the single-arm flexible waveguide driving structure through total internal reflection. This invention, a biomimetic adhesion-based single-arm optical waveguide micro-gripper, breaks through the traditional technical paradigm of "multi-arm rigid skeleton + mechanical clamping," realizing a skeletonless single-arm hydrogel cantilever beam design, and completely eliminating the risk of mechanical damage to the target object through a biomimetic adhesion capture mechanism.

Description

Technical Field

[0001] This invention relates to the field of femtosecond laser micro / nano fabrication technology, and in particular to a micro gripper for a single-arm optical waveguide at the end face of an optical fiber based on biomimetic adhesion. Background Technology

[0002] Soft actuators made of responsive hydrogels have shown great application potential in soft robotics, targeted drug delivery, microfluidics, and biomimetic systems. Integrating micro-actuators into the end face of slender and flexible optical fibers can effectively overcome the scattering and attenuation problems of light in free space, providing an ideal way to achieve remote, high-precision micro-nano manipulation in complex and confined environments such as narrow cavities in the human body and inside microfluidic chips.

[0003] Currently, the mainstream design scheme for fiber optic end-face micro-manipulation devices (such as micro-grippers), as shown in Chinese invention patent CN115356815B, generally adopts a composite mode of "rigid skeleton + flexible drive structure". This scheme relies on photothermal drive to shrink the flexible hydrogel, thereby pulling the pre-designed rigid gripper arm, and generating mechanical gripping force through the cooperative envelope of multiple arms to achieve target grasping. Similarly, cutting-edge international research (such as Nat. Commun. 14, 4313 (2023)) is dedicated to developing biomimetic soft actuators with multiple joints. Although rigid materials are abandoned, they still rely on complex multi-arm, multi-joint configurations, and complete the operation task through the cooperative deformation of multiple flexible units.

[0004] However, a deeper analysis of existing technologies reveals that the above solutions all follow the deeply ingrained technological paradigm of "multi-arm collaboration to generate mechanical force," resulting in the following inherent and insurmountable defects: 1. Structural Complexity and Miniaturization Bottlenecks: Whether it's a rigid-flexible coupled micro-gripper or a multi-joint soft actuator, their design inevitably involves complex multi-arm or multi-limb structures. This not only makes the integration and manufacturing of devices on the fiber end face (only 125μm in diameter) extremely difficult and requires extremely high processing precision, but also severely limits their potential for further miniaturization. More importantly, complex structures are highly susceptible to fatigue failure during high-frequency operation.

[0005] 2. Damage risks and operational limitations caused by the capture mechanism: The "mechanical gripping" principle determines that the gripping force is a concentrated stress at the contact point, which can easily cause irreversible physical damage when manipulating tiny biological samples (such as cells and organoids). At the same time, the opening size and shape of the grippers limit the size and geometric features of the operable targets, resulting in poor versatility.

[0006] 3. Theoretical upper limits of energy transfer efficiency and response speed: In existing technologies, light energy emitted from optical fibers must travel a distance in water before reaching the driving structure. The absorption and scattering of light by water leads to energy loss. More importantly, the heat generated by photothermal conversion must be conducted from the metal nanoparticle layer on the surface of the structure through a long path to the entire interior of the hydrogel. This slow heat diffusion process fundamentally limits the response speed of the device.

[0007] In summary, how to achieve rapid, low-damage, and high-energy-efficiency manipulation of micro- and nano-objects at the end face of optical fibers using only a single flexible structure, without resorting to complex rigid frameworks and multi-arm structures, has long been a difficult technical challenge in this field. This requires researchers to break through the traditional mindset of "mechanical clamping" and fundamentally innovate the path mode of optical energy transmission and conversion. Summary of the Invention

[0008] To address the technical problems mentioned in the background section, this invention provides a micro gripper for a single-arm optical waveguide at the fiber end face based on biomimetic adhesion.

[0009] This invention is achieved using the following technical solution: a micro-gripper for a single-arm optical waveguide at the fiber end face based on biomimetic adhesion, comprising: An optical fiber body for transmitting excitation light, the optical fiber body comprising a core and a cladding; The bottom end of the single-arm flexible waveguide driving structure is directly and integrally integrated into the center of the fiber core end face of the optical fiber body. The refractive index of the single-arm flexible waveguide driving structure satisfies the optical waveguide transmission conditions, so that the light beam emitted from the fiber core can be directly propagated by total internal reflection inside the single-arm flexible waveguide driving structure. The single-arm flexible waveguide driving structure is composed of an asymmetrically arranged high cross-linking density layer and a low cross-linking density layer, and a metal nanoparticle coating for photothermal conversion is provided on the same side surface of the high cross-linking density layer and the low cross-linking density layer. The single-arm flexible waveguide driven structure bends towards the low cross-linking density side under photothermal action, and utilizes the hydrogel adhesion force generated when the surface of the micro gripper comes into contact with the target object to achieve single-arm biomimetic adhesion capture of the target object.

[0010] Furthermore, the single-arm flexible waveguide driving structure is a cantilever beam structure in the shape of a cuboid or a truncated pyramid, with an overall length of 50-80μm and a width and thickness not exceeding 10μm.

[0011] Furthermore, the thickness of the high crosslinking density layer is less than the thickness of the low crosslinking density layer.

[0012] Furthermore, the single-arm flexible waveguide driving structure is characterized by being made of a hydrogel material, which is polymerized from a hydrogel precursor comprising N-isopropylacrylamide monomer, N,N'-methylenebisacrylamide crosslinking agent, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide photoinitiator and polyvinylpyrrolidone.

[0013] Furthermore, the metal nanoparticle coating is a silver nanoparticle coating, and the silver nanoparticle coating is mainly attached to the same side surface of the high crosslinking density layer and the low crosslinking density layer; under 808nm near-infrared light excitation, the single-arm flexible waveguide driving structure completes a 90° bend within 2.97ms.

[0014] The present invention also proposes a method for fabricating a single-arm optical waveguide micro-gripper as described in claim 1, comprising the following steps: Step 1, hydrogel precursor preparation and optical fiber fixation: Prepare a hydrogel precursor solution composed of N-isopropylacrylamide (NIPAM) monomer, MBA crosslinking agent, TPO photoinitiator and PVP (for enhancing the mechanical strength of the single arm without a frame), and place the optical fiber end face, which has been surface silanized, in the hydrogel precursor solution. The second step is to fabricate a single-arm waveguide structure using femtosecond laser two-photon polymerization: using a femtosecond laser processing system, the laser focus is aligned with the center of the fiber core to directly fabricate a single-arm double-layer hydrogel structure without a rigid skeleton; during the processing, by setting different scanning repetition times, a low cross-linking density layer and a high cross-linking density layer are respectively constructed inside the single-arm double-layer hydrogel structure. The third step is the in-situ reduction of the metal nanoparticle coating: the processed single-arm hydrogel structure is immersed in a solution containing a silver precursor, and the surface of the single-arm hydrogel structure is scanned in situ again using a femtosecond laser two-photon reduction process to reduce and generate a dense silver nanoparticle coating, thereby completing the fabrication of the fiber end face single-arm optical waveguide micro gripper.

[0015] Furthermore, in the first step, the coating layer of the optical fiber needs to be stripped off and the end face cut flat, and then vertically fixed in the precursor solution.

[0016] Furthermore, in the third step, the femtosecond laser processing system includes a femtosecond laser, a laser power control module, a spatial light modulator, a lens group, an aperture, an oil mirror, an image acquisition module, a three-dimensional displacement stage, and a manual input module. The sample to be processed is fixed on the displacement stage, and a preset processing program can be written through the manual input module to achieve precise control of the three-dimensional position of the laser focus and the scanning path.

[0017] Furthermore, in the second step, by adjusting the scanning repetition time of the femtosecond laser, the total width and thickness of the single-arm flexible waveguide driving structure is 10 μm, and the length is 70 μm; one side has a thickness of 7 μm and a scanning time of 1 ms to form a low crosslinking density LCD layer; the other side has a thickness of 3 μm and a scanning time of 5 ms to form a high crosslinking density HCD layer.

[0018] Furthermore, in the third step, the laser power used in the femtosecond laser two-photon reduction process is 55mW.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes a biomimetic adhesion-based single-arm optical waveguide micro-gripper, which breaks through the traditional technical paradigm of "multi-arm rigid skeleton + mechanical clamping" for the first time. It achieves a skeletonless single-arm hydrogel cantilever beam design and completely eliminates the risk of mechanical damage to the target object through a biomimetic adhesion capture mechanism. Through the in-situ optical transmission architecture of the actuator / waveguide, light energy propagates through total internal reflection within the hydrogel. Combined with the two-photon in-situ reduction of the AgNPs coating, it achieves an ultrafast 90° bending within 2.97 ms, a response speed order of magnitude faster than existing technologies, with a driving power of less than 10 mW. Simultaneously, the PVP-enhanced skeletonless single arm can lift loads exceeding its own weight by 164 times. This gripper has irreplaceable application prospects in fields such as non-destructive manipulation of single cells, remote minimally invasive surgery in narrow cavities, and flexible logistics within microfluidic chips, representing a paradigm leap from "mechanical grippers" to "biomimetic adhesive flexible arms" in fiber optic end-face micromanipulation devices. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the femtosecond laser processing system proposed in an embodiment of the present invention; Figure 2 This is a schematic diagram of the optical fiber fixing device proposed in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the fiber end-face asymmetric double-layer hydrogel micro actuator proposed in an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the principle of ultrafast bending deformation driven by the optical waveguide effect proposed in an embodiment of the present invention. Figure 5 The time series diagram shows the micro-actuator proposed in this embodiment of the invention achieving a 90° ultrafast bending response within 2.97 ms. Figure 6 The graph shows the relationship between the response time and bending curvature of the micro-actuator proposed in this embodiment of the invention. Figure 7 This is a schematic diagram of a single-arm adhesive capture method inspired by the frog's tongue predation mechanism, as proposed in an embodiment of the present invention. Figure 8 These are time-series microscopic images of the ultrafast bending and adhesion of microparticles by the micro-gripper proposed in an embodiment of the present invention. Detailed Implementation

[0021] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0022] Please combine Figures 1-8 The fabrication process of the single-arm optical waveguide micro-gripper based on biomimetic adhesion proposed in this embodiment is as follows: In this embodiment, the femtosecond laser processing system used to fabricate the single-arm optical waveguide micro-gripper at the fiber end face is first described. For example... Figure 1 As shown, the femtosecond laser processing system used in this invention includes a femtosecond laser, a laser power control module, a spatial light modulator (SLM), a lens group (lens 1, lens 2), an aperture (P), an oil immersion lens (objective), an image acquisition module (CCD), a three-dimensional displacement stage, and a manual input module. The sample to be processed is fixed on the displacement stage, and a preset processing program can be written through the manual input module to achieve precise control of the three-dimensional position of the laser focus and the scanning path. Its advantages lie in the fact that this integrated system can complete subsequent hydrogel two-photon polymerization processing and metal nanoparticle two-photon reduction processing on the same platform without changing equipment, ensuring the alignment accuracy and process consistency of micro-nano processing.

[0023] In this embodiment, the first step involves preparing the hydrogel precursor and fixing it with optical fibers. First, a hydrogel precursor solution is prepared, primarily composed of N-isopropylacrylamide (NIPAM) monomer, N,N'-methylenebisacrylamide (MBA) crosslinking agent, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) photoinitiator, and polyvinylpyrrolidone (PVP). Using isopropanol as a solvent, 800 mg of NIPAM monomer, 15 mg of MBA crosslinking agent, 15 mg of TPO photoinitiator, and 150 mg of PVP are added to every 1 mL of solvent. The mixture is placed in a light-protected environment and magnetically stirred at room temperature for 12 hours until the solid powder is completely dissolved. Subsequently, the solution is ultrasonically degassed for 10 minutes in an ultrasonic cleaner to remove microbubbles, ultimately obtaining a uniform and transparent hydrogel precursor solution, which is stored in the dark for later use. NIPAM, as a thermally responsive monomer, endows the hydrogel with the ability to shrink in volume above its lower critical dissolution temperature, which is the basis for photothermal drive. MBA, as a crosslinking agent, is used to construct the three-dimensional network structure of the hydrogel. TPO, as a photoinitiator, initiates the polymerization reaction under femtosecond laser irradiation. Notably, the addition of PVP enhances the mechanical strength of the single-arm hydrogel structure in subsequent processing without a rigid framework, preventing the single arm from fracturing and failing when working independently. Its beneficial effect lies in the fact that the hydrogen bonding between PVP and PNIPAM molecular chains significantly improves the self-support and bending resistance of the single-arm hydrogel structure without rigid framework support, making the "framework-free" single-arm design physically possible. At the same time, the addition of PVP also increases the viscosity of the precursor solution, which is beneficial for maintaining the stability of the structural shape during femtosecond laser processing.

[0024] It should be noted that surface treatment of the optical fiber is necessary to enhance the interfacial bonding between the fiber end face and the hydrogel structure. Specifically, the optical fiber is inserted into the optical fiber ceramic ferrule for stable fixation, the fiber end face is cut flat, and then subjected to silanization treatment (e.g., immersion in a toluene solution of 3-(trimethoxysilyl)methacrylate), followed by rinsing with acetone and deionized water. Silanization transforms the fiber end face from a hydrophilic surface into an active interface capable of participating in the polymerization reaction. When the hydrogel precursor polymerizes on the fiber end face, the hydrogel molecular chains covalently bond with the double bonds in the silane coupling agent, forming a strong chemical bond rather than simple physical adsorption. The beneficial effect is a significant improvement in the interfacial bonding strength between the hydrogel driving structure and the optical fiber substrate, ensuring that the gripper will not peel off or detach from the fiber end face during high-frequency, large-amplitude repeated bending, thus guaranteeing the long-term reliability and lifespan of the device. The treated optical fiber is then vertically fixed in the precursor solution, as shown in the image. Figure 2 As shown.

[0025] In this embodiment, the second step involves femtosecond laser two-photon polymerization (TPP) to fabricate a single-arm waveguide structure. Specifically, the femtosecond laser processing system is turned on, and the pre-written processing program for the double-layer hydrogel structure is input into the system via a manual input module. Using TPP technology, the laser focus is precisely aligned with the center of the fiber core, directly fabricating a single-arm double-layer hydrogel structure without any rigid framework on the fiber end face. The advantage of precisely fabricating the actuator at the center of the fiber core is that when excitation light is subsequently applied, the beam exiting the core can directly enter the actuator's interior, rather than deviating to the cladding or the external water environment. This is a prerequisite for achieving the "actuator as waveguide" function.

[0026] It is worth mentioning that, in order to construct an asymmetric crosslinking density to achieve directional bending, the scanning repetition time (SRT) of the femtosecond laser is adjusted during the processing to construct an asymmetric structure with different crosslinking densities on both sides. For example... Figure 3 As shown, the overall dimensions of the micro-actuator were set to 70 μm in length, and 10 μm in width and thickness. The width of the low crosslinking density (LCD) portion was set to 7 μm, and the scan repetition time for processing was set to 1 ms; the width of the high crosslinking density (HCD) portion was set to 3 μm, and the scan repetition time for processing was set to 5 ms. The suitable laser processing power was approximately 55 mW. Its advantage lies in the fact that an asymmetric distribution of crosslinking density can be constructed within the same material system in the same processing step by adjusting a single process parameter (SRT), without the need to introduce a second material or perform secondary processing, greatly simplifying the fabrication process. Due to the short scan time and low crosslinking density of the LCD portion, its three-dimensional network structure is more porous and has higher porosity, allowing it to expel more water molecules when heated, thus exhibiting a greater volume shrinkage rate than the HCD portion. This difference in shrinkage rate is the direct mechanical source driving the single arm to bend directionally towards the LCD side. After processing, the sample was immersed in a developing solution (such as ethanol) for 15 minutes to remove the uncured precursor, resulting in a single-arm hydrogel structure with its bottom directly integrated into the center of the fiber core end face.

[0027] In this embodiment, the third step involves in-situ reduction of the metal nanoparticle coating. First, a silver ammonia solution is prepared as a silver precursor solution: a 0.1 mol / L aqueous solution of silver nitrate (AgNO3) is prepared, and 2% ammonia solution is added dropwise with stirring until the initially formed dark precipitate is completely dissolved, resulting in a clear and transparent silver ammonia complex solution. The prepared optical fiber end face with a single-arm hydrogel structure is then immersed in the silver ammonia solution.

[0028] Subsequently, the two-photon reduction process of the femtosecond laser processing system was used again to perform in-situ scanning reduction on the surface of the single-arm hydrogel structure. Since the laser focus can be precisely controlled, the dense silver nanoparticle (AgNPs) coating generated by the reduction mainly adheres to the surface of the hydrogel in the high cross-linking density (HCD) region. Its beneficial effects are reflected in several aspects: First, AgNPs, as a photothermal conversion medium, efficiently convert light energy into heat energy through plasmon resonance under 808nm near-infrared light irradiation, realizing remote, non-contact heating of the hydrogel actuator; Second, the AgNPs coating is mainly located on the surface of the HCD layer. When photothermal conversion occurs, heat is first transferred to the HCD layer. However, due to the high crosslinking density and weak shrinkage capacity of the HCD layer, when the heat is subsequently transferred to the adjacent LCD layer, the LCD layer undergoes severe shrinkage. This distribution pattern of "heat conduction from the weak shrinkage area to the strong shrinkage area" further amplifies the asymmetric shrinkage effect, making bending faster and at larger angles; Third, the two-photon reduction process and the previous two-photon polymerization process can be completed on the same femtosecond laser system without additional equipment, and the reduction area can be precisely matched with the preset HCD area, avoiding disordered deposition of AgNPs. After reduction, it is rinsed with deionized water to obtain a micro-actuator with excellent photothermal conversion capabilities. It should be noted that the AgNPs coating not only serves as a photothermal conversion medium, but its dense stacking also generates a plasmon enhancement effect that can further improve light absorption efficiency and reduce the required excitation power.

[0029] In this embodiment, the fourth step verifies the driving principle and performance of the prepared micro-gripper. For example... Figure 4 As shown, the fabricated micro-actuator is connected to an 808nm near-infrared (NIR) laser source. Since the actuator is directly fabricated at the center of the optical fiber core and its refractive index meets the waveguide transmission conditions (the hydrogel's refractive index is higher than that of the external water environment), the micro-actuator itself acts as an "extension waveguide" of the optical fiber. This "actuator as waveguide" design brings significant benefits: the light beam does not need to propagate through an external water environment, avoiding light energy loss caused by water absorption and scattering. Instead, it directly enters the micro-actuator from the fiber core and undergoes total internal reflection, allowing the light energy to reach the entire actuator structure almost without loss and be efficiently absorbed by the AgNPs distributed on the surface. Compared to existing technologies where light energy needs to travel a distance through water after exiting the optical fiber to reach the actuator, the light energy transmission efficiency of this invention increases exponentially, enabling the same thermal effect to be obtained at lower optical power. After absorbing light energy, the AgNPs convert it into heat energy, which diffuses into the surrounding hydrogel. When the temperature of a hydrogel rises above the lower critical dissolution temperature (LCST, approximately 32°C), the hydrogel changes from a hydrophilic state to a hydrophobic state, the molecular chains collapse, expelling internal water molecules and resulting in volume shrinkage.

[0030] In this embodiment, as Figure 5 Time series plots and Figure 6 As shown in the response time versus curvature curve, due to the difference in shrinkage rates between the LCD and HCD layers (the LCD layer has a larger shrinkage rate), the actuator rapidly bends towards the side with lower cross-linking density after being heated by light. Thanks to the optical waveguide design that eliminates optical path loss and the direct, efficient photothermal coupling, this micro-actuator exhibits excellent ultrafast response capabilities. With the laser activated, the curvature of the micro-actuator increases rapidly in a near-linear manner, completing a large-angle deformation from its initial state perpendicular to the fiber end face to a full 90° bend within just 2.97 ms. This 2.97 ms response time is an order of magnitude shorter than the 30 ms response time in existing technologies. Its advantage lies in enabling the grasper to complete the capture action before the target object moves or environmental conditions change, greatly improving the capture success rate in dynamic environments. When the laser is turned off, the structure rapidly cools down, the hydrogel reabsorbs water and expands, and the actuator instantly returns to its initial vertical state. The reversible process also responds quickly, enabling the gripper to rapidly release the target object and prepare for the next capture, achieving repeatable, high-frequency micro-manipulation.

[0031] In this embodiment, the fifth step is to verify the capture performance of the micro-grabber. For example... Figure 7 As shown, the miniature grasper designed in this invention mimics the capture mechanism of a frog sticking out its tongue to catch prey. Just as a frog captures prey by rapidly extending its tongue and utilizing the high adhesive force on its surface, the single-arm actuator of this invention generates ultrafast bending (e.g., under the excitation of the optical waveguide effect) under the excitation of the optical waveguide effect. Figure 7 (As shown by the dashed trajectory in the lower half), the target microparticles are firmly "adheded" to the actuator surface by utilizing instantaneous contact impact and the inherent adhesive force of the hydrogel surface. This biomimetic "adhesion" capture mechanism brings fundamental benefits compared to the "mechanical gripping" mechanism of traditional micro-grippers: First, it completely eliminates the dependence on the shape and size of the target object, eliminating the need to design different shaped grippers for different shaped objects; Second, the inherent adhesive force of the hydrogel surface is physical adhesion, which will not cause mechanical damage such as indentations, scratches, or brittle fractures to the surface of the target object, making it particularly suitable for non-destructive operation of fragile targets such as biological cells and soft tissues; Third, the single-arm structure does not require the space to reserve for multi-arm opposing movement, greatly reducing the difficulty of operation in extremely narrow spaces.

[0032] Furthermore, to verify the load-bearing capacity, this embodiment uses silicone microspheres with a diameter of 50 μm as the target object. Measurements showed that the micro-gripper itself is extremely lightweight, easily adhering to and lifting the aforementioned silicone microspheres, which weigh more than 164 times its own weight. This high load-bearing capacity benefits from two synergistic effects: first, the dynamic impact force generated by ultra-fast bending ensures sufficient contact between the single arm and the target object, increasing the effective adhesion area; second, the adhesive properties of the hydrogel material itself are further enhanced under impact compression. This load-bearing capacity far exceeds that of traditional friction-based micro-grippers, enabling this gripper to manipulate a wide range of objects, from tiny particles to larger ones.

[0033] like Figure 8 As shown in the time-series micrographs, the specific capture process is as follows: From 0 s to 29.536 s, the optical fiber is moved via a three-dimensional displacement stage, allowing the single-arm gripper to gradually approach the suspended target microparticle (silicone ball); at 29.540 s, an 808 nm laser is activated, and the actuator undergoes a large-angle, rapid bend within a very short time, successfully adhering to the target and completing the capture; subsequently, under continuous illumination (as shown at 31.293 s), the gripper remains bent and firmly adsorbs and lifts the microparticle; after the optical fiber moves to the target position, the laser is turned off at 32.134 s, the actuator rapidly cools down and returns to its initial straight state, and the target microparticle detaches and is released, thus achieving targeted, ultrafast, and non-destructive transport of micro-objects. Throughout the process, the high adhesion of the hydrogel surface ensures the reliability of the capture while avoiding mechanical damage to the target object. The beneficial effect of this operation process is that it enables remote control of the entire "capture-transfer-release" process for a single micro-object, and the target object remains in an aqueous environment throughout the process, avoiding surface tension damage to biological samples that may occur at the gas-liquid interface.

[0034] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, the shape of the single-arm flexible waveguide driving structure is not limited to a cuboid, but can also be a cantilever beam structure in the shape of a truncated pyramid. This shape helps to increase root strength and reduce tip mass, thereby further improving bending response speed; the metal nanoparticles are not limited to silver, but can also be gold nanoparticles, which are superior in terms of biocompatibility and have tunable plasmon resonance peaks; the light driving wavelength can be adjusted accordingly based on the absorption peak of the metal nanoparticles to achieve optimal photothermal conversion efficiency. However, the aforementioned alternative solutions do not depart from the core concept of this invention—achieving ultrafast non-destructive capture through a "single-arm optical waveguide structure + asymmetric cross-linking density + biomimetic adhesion"—and all fall within the protection scope of this invention. The above descriptions are merely specific embodiments of this application, but the protection scope of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the protection scope of this application. Therefore, the protection scope of this application should be determined by the scope of the claims.

[0035] In conclusion, 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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A micro-gripper for a single-arm optical waveguide at the fiber end face based on biomimetic adhesion, characterized in that, include: An optical fiber body for transmitting excitation light, the optical fiber body comprising a core and a cladding; The bottom end of the single-arm flexible waveguide driving structure is directly and integrally integrated into the center of the fiber core end face of the optical fiber body. The refractive index of the single-arm flexible waveguide driving structure satisfies the optical waveguide transmission conditions, so that the light beam emitted from the fiber core can be directly propagated by total internal reflection inside the single-arm flexible waveguide driving structure. The single-arm flexible waveguide driving structure is composed of an asymmetrically arranged high cross-linking density layer and a low cross-linking density layer, and a metal nanoparticle coating for photothermal conversion is provided on the same side surface of the high cross-linking density layer and the low cross-linking density layer. The single-arm flexible waveguide driven structure bends towards the low cross-linking density side under photothermal action, and utilizes the hydrogel adhesion force generated when the surface of the micro gripper comes into contact with the target object to achieve single-arm biomimetic adhesion capture of the target object.

2. The fiber optic end-face single-arm optical waveguide miniature gripper according to claim 1, characterized in that, The single-arm flexible waveguide driving structure is a cantilever beam structure in the shape of a cuboid or a truncated pyramid, with an overall length of 50-80μm and a width and thickness not exceeding 10μm.

3. The fiber optic end-face single-arm optical waveguide miniature gripper according to claim 1, characterized in that, The thickness of the high crosslinking density layer is less than the thickness of the low crosslinking density layer.

4. The fiber optic end-face single-arm optical waveguide miniature gripper according to claim 1, characterized in that, The single-arm flexible waveguide drive structure is made of hydrogel material, which is polymerized from a hydrogel precursor comprising N-isopropylacrylamide monomer, N,N'-methylenebisacrylamide crosslinking agent, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide photoinitiator and polyvinylpyrrolidone.

5. The fiber optic end-face single-arm optical waveguide miniature gripper according to claim 1, characterized in that, The metal nanoparticle coating is a silver nanoparticle coating, and the silver nanoparticle coating is mainly attached to the same side surface of the high crosslinking density layer and the low crosslinking density layer; under 808nm near-infrared light excitation, the single-arm flexible waveguide driving structure completes a 90° bend within 2.97ms.

6. A method for fabricating a single-arm optical waveguide micro-gripper as described in claim 1, characterized in that, Includes the following steps: Step 1, hydrogel precursor preparation and optical fiber fixation: Prepare a hydrogel precursor solution composed of N-isopropylacrylamide (NIPAM) monomer, MBA crosslinking agent, TPO photoinitiator and PVP (for enhancing the mechanical strength of the single arm without a frame), and place the optical fiber end face, which has been surface silanized, in the hydrogel precursor solution. The second step is to fabricate a single-arm waveguide structure using femtosecond laser two-photon polymerization: using a femtosecond laser processing system, the laser focus is aligned with the center of the fiber core to directly fabricate a single-arm double-layer hydrogel structure without a rigid skeleton; during the processing, by setting different scanning repetition times, a low cross-linking density layer and a high cross-linking density layer are respectively constructed inside the single-arm double-layer hydrogel structure. The third step is the in-situ reduction of the metal nanoparticle coating: the processed single-arm hydrogel structure is immersed in a solution containing a silver precursor, and the surface of the single-arm hydrogel structure is scanned in situ again using a femtosecond laser two-photon reduction process to reduce and generate a dense silver nanoparticle coating, thereby completing the fabrication of the fiber end face single-arm optical waveguide micro gripper.

7. The preparation method according to claim 6, characterized in that, In the first step, the coating layer of the optical fiber needs to be stripped off and the end face cut flat, and then vertically fixed in the precursor solution.

8. The preparation method according to claim 6, characterized in that, In the third step, the femtosecond laser processing system includes a femtosecond laser, a laser power control module, a spatial light modulator, a lens group, an aperture, an oil mirror, an image acquisition module, a three-dimensional displacement stage, and a manual input module. The sample to be processed is fixed on the displacement stage, and a preset processing program can be written through the manual input module to achieve precise control of the three-dimensional position of the laser focus and the scanning path.

9. The preparation method according to claim 6, characterized in that, In the second step, by adjusting the scanning repetition time of the femtosecond laser, the total width and thickness of the single-arm flexible waveguide driving structure are 10 μm, and the length is 70 μm. One side has a thickness of 7 μm and a scanning time of 1 ms to form a low crosslinking density LCD layer; the other side has a thickness of 3 μm and a scanning time of 5 ms to form a high crosslinking density HCD layer.

10. The preparation method according to claim 6, characterized in that, In the third step, the laser power used in the femtosecond laser two-photon reduction process is 55mW.

Images