A micro-tweezer based on vanadium dioxide nanowires

Abstract

This invention discloses a micro tweezer based on vanadium dioxide nanowires, comprising a silicon substrate, a vanadium dioxide nanowire actuator, a heating unit, a power supply, a capacitance detection circuit, and a data processing and recognition unit. The silicon substrate has clamping arm electrodes and heating unit electrodes. The clamping arm of the vanadium dioxide nanowire actuator has a double-layer structure of vanadium dioxide nanowires and a metal layer. The heating unit heats the clamping arm to deform it, achieving clamping. The capacitance detection circuit, combined with the recognition unit, can determine the clamping state and identify the type of object being clamped. This invention utilizes the double-layer structure of the clamping arm, taking advantage of the significant heterogeneous interfacial stress between the vanadium dioxide nanowires during phase transition and the surface-deposited metal layer. This allows a single nanowire to generate a bending displacement exceeding 5% or even higher of its own length. The clamping arm exhibits large displacement and strong environmental adaptability. Integrating sensing and recognition functions, it enables precise clamping, transfer, and type identification of micro- and nano-sized objects, making it compatible with micro- and nano-electromechanical systems (MEMS).

Description

Technical Field

[0001] This invention relates to the field of micro-nano electromechanical systems and micro-nano actuators, specifically a type of micro tweezers based on vanadium dioxide nanowires. Background Technology

[0002] While modern micro-nano electromechanical systems and micro-nano actuator technologies are constantly evolving, existing solutions face numerous common challenges in meeting the demands of next-generation micro-nano manipulations requiring higher precision and greater adaptability. For example, piezoelectric and electrostatic actuators struggle to simultaneously achieve large displacement and high output force at the microscale, often requiring the sacrifice of one or the introduction of complex mechanical amplification structures, increasing system complexity, size, and manufacturing difficulty. Most actuators have stringent environmental requirements and cannot operate stably in wet environments such as physiological fluids and cell culture media, limiting their application in live biological manipulation. Furthermore, existing micro-tweezers cannot determine the gripping state through electrical detection, nor can they identify the type of substance being gripped.

[0003] Microtweezers technology is a core device in the field of micro-nano manipulation. Its development is closely related to breakthroughs in fields such as micro-nano electromechanical systems (MEMS / NEMS), biomedical engineering, and advanced manufacturing. The core objective is to achieve controllable and precise mechanical manipulation at the microscale. Early micromanipulation relied on the precise control of macroscopic manipulators under a microscope, which limited accuracy and flexibility. With the maturity of microfabrication technology, microtweezers have developed as independent devices. The driving technology has evolved from macroscopic mechanical transmission to various direct driving mechanisms at the micro-nano scale, such as thermal, piezoelectric, electrostatic, and shape memory alloys. Microtweezers are also developing towards miniaturization, integration, and chip-based applications. However, the aforementioned technical shortcomings have not yet been effectively resolved. Summary of the Invention

[0004] The purpose of this invention is to overcome or at least partially solve the above-mentioned problems by proposing a micro tweezer based on vanadium dioxide nanowires. This tweezer has the advantages of large displacement, high frequency response, good environmental adaptability, and can realize the detection of gripping state and identification of the type of gripped substance. At the same time, it provides a method for preparing the micro tweezer and its application, filling the technical gap of existing micro-nano manipulation devices.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a micro tweezers based on vanadium dioxide nanowires, comprising:

[0006] A silicon substrate has two clamping arm electrodes and two heating unit electrodes arranged on its surface.

[0007] The vanadium dioxide nanowire actuator includes two clamping arms arranged symmetrically to each other. The clamping arms have a double-layer structure, with the lower layer being a single-crystal vanadium dioxide nanowire and the upper layer being a metal layer deposited by electron beam evaporation. Each clamping arm is electrically connected to a corresponding clamping arm electrode on the substrate silicon wafer.

[0008] A heating unit, which is arranged on the substrate silicon wafer and electrically connected to the heating unit electrode, is used to heat the clamping arm, causing the clamping arm to deform and perform a clamping action;

[0009] A power supply, which is arranged on the substrate silicon wafer and electrically connected to the heating unit electrode;

[0010] A capacitance detection circuit is electrically connected to the clamping arm electrode connected to the clamping arm, and is used to detect the change in capacitance value during the operation of the micro tweezers to judge its clamping state; the capacitance detection circuit is also connected to a data processing and recognition unit, and the data processing and recognition unit internally integrates a micro-nano object feature database and a recognition algorithm, which converts the read capacitance signal into object feature information to identify the type of the clamped object.

[0011] Preferably, the heating unit includes a serpentine heating resistance wire, and the width of the heating resistance wire is 3-5 μm; the thicknesses of the heating resistance wire, the clamping arm electrode and the heating unit electrode are all 40-60 nm; when the clamping arm is heated to 68 °C, the swing amplitude relative to the initial posture at room temperature is 60-90 °, and the displacement distance of its end is 150-250 μm.

[0012] Preferably, the capacitance detection circuit is a 4215-CVU supporting a 4200A-SCS parameter analyzer, and the minimum capacitance value it can detect is 10 -18 f, which can detect the dynamic change of capacitance value during the no-load, opening and closing, and clamping contact processes of the micro tweezers in real time, and cooperate with the upper computer software system to run the object type recognition algorithm in real time, and intuitively display the current clamping state (no-load / contact / stable clamping) and the predicted type label of the clamped object on the software interface.

[0013] Furthermore, in order to accurately judge the type of the clamped substance, the data processing and recognition unit connected to the capacitance detection circuit is constructed and operated according to the following steps:

[0014] Construct a micro-nano target dielectric constant database: Pre-test or input the standard dielectric constant ε range of common micro-nano operation objects (such as polystyrene microspheres, silica microspheres, different types of biological cells, etc.) at a specific frequency to form a reference database; at the same time, input the reference capacitance curve C of the micro tweezers changing with the opening and closing distance in the no-load state base-d ;

[0015] Implant the clamping state judgment logic: Set the capacitance change rate threshold (ΔC / Δt). When the capacitance detection circuit monitors that the real-time capacitance value suddenly changes and stabilizes in a specific numerical range, it is judged that the micro tweezers have entered the "clamping contact state" from the "moving state";

[0016] The object type recognition algorithm is configured based on the principle of parallel plate capacitor C = ε·S / d (where S is the effective contact area between vanadium dioxide nanowire and object, and d is the distance between the two arms). The algorithm obtains the capacitance measurement value C at the moment of clamping in real time, and calculates the distance d by combining the known geometric parameters of micro tweezers and the distance d calculated by real-time driving voltage, and then calculates the equivalent dielectric constant ε of the clamped object in reverse.

[0017] Perform matching and identification: Match the calculated ε with the ε in the database, calculate the matching degree using the least squares method or the nearest neighbor classification algorithm, and output the category name of the object when the matching degree is higher than the preset confidence level (such as 95%); if no match is found, mark it as an unknown object and record its dielectric characteristics to expand the database.

[0018] Through the integrated hardware detection and software algorithm processing described above, this invention not only uses vanadium dioxide nanowires as sensors to read physical quantities, but also solves the problem that existing technologies can only sense "presence" but cannot identify "what it is" by constructing a unique dielectric property inversion model, thus realizing integrated intelligent operation of "clamping-sensing-recognition" in micro-nano manipulation.

[0019] This invention also provides a method for preparing micro tweezers based on vanadium dioxide nanowires, comprising the following steps:

[0020] After the silicon wafer with polished and oxidized surface is activated, it is sequentially cleaned, dehydrated and surface film formed to obtain a pretreated substrate silicon wafer;

[0021] A layer of polymethyl methacrylate (PMMA) photoresist is uniformly coated on the surface of the substrate silicon wafer, and a pre-baking process is performed to form the photoresist layer;

[0022] The photoresist layer is exposed on a photolithography machine using a photomask, and then the substrate silicon wafer is developed. After the substrate silicon wafer is patterned, molybdenum is sputtered onto the patterned substrate silicon wafer at a power of 100W using a magnetron sputtering process. After sputtering for 7 to 15 minutes, a molybdenum metal thin film with a thickness of 40 to 60 nm is formed.

[0023] After magnetron sputtering, the excess molybdenum metal film on the substrate silicon wafer is removed by a peeling process to form metal electrodes and heating circuits.

[0024] The preparation of the vanadium dioxide nanowire actuator consists of two steps. The first step is the synthesis of vanadium dioxide nanowires. 0.4 g of commercially available vanadium dioxide powder with a purity of 99% is placed in a quartz boat and then placed in the center of a horizontal tube furnace. An unpolished (rough) quartz substrate is placed 6 mm above the bottom of the quartz boat to obtain a higher vapor density and deposition temperature. First, the furnace tube is evacuated to a basic pressure of 1.33 Pa and then purged with argon (Ar). Then, the temperature is increased at a rate of 15 °C / min and maintained at the target temperature of 750 °C~850 °C for 5~6 hours. Throughout the process, the pressure is maintained at 1333 Pa. After the reaction is completed, the tube furnace is allowed to cool to room temperature before the unpolished quartz substrate with vanadium dioxide nanowires grown is removed.

[0025] The second step involves using an electron beam process to deposit a 100-200 nm thick metal layer onto an unpolished quartz substrate on which vanadium dioxide nanowires have grown, forming a double-layer structure. The vanadium dioxide nanowire actuator on the quartz substrate is scraped off with a thin blade and dispersed in 5 ml of ethanol solution. After being evenly dispersed by an ultrasonic cleaner, 10 μl of the nanowire actuator suspension is dropped onto a glass slide using a pipette. The vanadium dioxide nanowire actuator is now complete.

[0026] In the vanadium dioxide nanowire brake, the single-crystal vanadium dioxide nanowires with a diameter of 200~400nm, a length of 100~150μm, and an aspect ratio of 375~500 serve as the bottom layer of the brake.

[0027] A vanadium dioxide nanowire actuator dispersed on a glass slide was transferred using a tungsten probe. Two vanadium dioxide nanowire actuators were transferred to the first clamping arm electrode and the second clamping arm electrode, respectively. Platinum was deposited on the ends of the vanadium dioxide nanowire actuators using focused ion beam induced chemical vapor deposition (FIB-CVD) to form two rectangular platinum metal blocks as the first and second fixing ends to symmetrically fix the two vanadium dioxide nanowire actuators.

[0028] Next, the power supply is connected to the first heating unit electrode and the second heating unit electrode through two wires, and the capacitance detection circuit is connected to the first clamping arm electrode and the second clamping arm electrode through two probes, thus obtaining a voltage-controlled self-sensing micro tweezer based on vanadium dioxide nanowires.

[0029] Furthermore, the vanadium dioxide nanowire actuator is first peeled off from the glass slide using a tungsten probe, and then a 5V voltage is applied to adsorb the vanadium dioxide nanowire actuator for transfer. The vanadium dioxide nanowire actuator is placed on the first clamping arm electrode and the second clamping arm electrode in two separate steps. Then, the applied voltage is turned off to release the vanadium dioxide nanowire actuator, and finally the transfer is completed.

[0030] Preferably, the activation temperature of the silicon wafer is 550~650K, the activation time is 25~35min, and the pre-baking treatment temperature is 370~380K, the time is 55~65s.

[0031] Preferably, the vanadium dioxide nanowires are single-crystal structures and are prepared by chemical vapor deposition; the metal used for the metal layer evaporation is chromium, the electron beam evaporation rate is 0.5~1.0 Å / s, and the vacuum degree of the evaporation environment is less than 1×10⁻⁶. –2 Pa.

[0032] Preferably, the first and second fixed ends are deposited with platinum at the ends of the vanadium dioxide nanowire actuator by focused ion beam induced chemical vapor deposition to form a platinum metal rectangular block with a length of 2μm, a width of 200nm, and a thickness of 200nm.

[0033] Preferably, the magnetron sputtering uses a metallic phase sputtering material, with a sputtering velocity of 0.6~0.9 Å / s and a sputtering environment vacuum degree of less than 1×10⁻⁶. –2 Pa.

[0034] Preferably, the photolithography uses AZ5214 photoresist, with an exposure dose of 3.6~4.0mW / cm² and a development time of 80~120s.

[0035] An application of vanadium dioxide nanowire-based microtweezers is disclosed, which are used in the fields of micromanipulation and microassembly to precisely grasp and transfer micro- and nano-scale objects, and simultaneously achieve real-time identification of the type of micro- and nano-scale objects being grasped; the micro- and nano-scale objects include one or more of polystyrene microspheres, silica microspheres, and different types of biological cells.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. Using a bilayer structure combining vanadium dioxide nanowires and a metal layer as the clamping arm, and leveraging the enormous heterogeneous interfacial stress between the vanadium dioxide nanowires and the surface-deposited metal layer during phase transition, a single nanowire can generate a bending displacement exceeding 5% or even higher than its own length, resulting in a large output displacement. Simultaneously, the phase transition of the vanadium dioxide nanowires is completed within milliseconds, enabling high-frequency control and manipulation.

[0038] 2. The deformation drive of the clamping arm originates from the solid-state phase change of the material, and its performance remains stable in various environments such as air, liquid, and even biological culture media, overcoming the stringent environmental requirements of electrostatic drive technologies. Simultaneously, heating is driven by generating Joule heat applied to the serpentine resistance wire using a low voltage, resulting in high energy conversion efficiency and low power consumption.

[0039] 3. By integrating a high-precision capacitance detection circuit with a data processing and recognition unit, it can detect capacitance changes in real time and determine the gripping state. At the same time, based on dielectric constant inversion and feature matching, it can accurately identify the type of gripped item, solving the technical problem that existing micro tweezers can only grip but cannot sense or identify the type of item. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the planar structure of the micro tweezers of the present invention;

[0041] Figure 2 This is a three-dimensional structural diagram of the micro tweezers of the present invention;

[0042] Figure 3 This is a flowchart illustrating the fabrication process of the electrodes and resistance wire circuit of the micro tweezers of the present invention.

[0043] Figure 4 This is an enlarged view of the front end of the micro tweezers of the present invention and a schematic diagram of its application, wherein the arrow indicates the direction of movement of the micro tweezers.

[0044] In the figure: 100, silicon substrate; 101, resist layer; 102, vanadium dioxide nanowire actuator; 102.1, first clamping arm; 102.2, second clamping arm; 103, first fixed end; 104, second fixed end; 105, first clamping arm electrode; 106, second clamping arm electrode; 107, heating resistance wire; 108, first heating unit electrode; 109, second heating unit electrode; 110, power supply; 111, capacitance detection circuit. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the accompanying drawings.

[0046] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this description, those skilled in the art can make creative modifications to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

[0047] This invention provides a micro tweezer based on vanadium dioxide nanowires, which solves the technical problems in the prior art. The overall concept is as follows:

[0048] Example 1:

[0049] Please see Figure 1 This embodiment provides a method for preparing self-sensing microtweezers based on vanadium dioxide nanowires, specifically:

[0050] 1) Substrate pretreatment:

[0051] Using a surface-polished and oxidized silicon wafer as the substrate material, it is activated at 550 K for 25 min to ensure good electrical insulation. Then, it is cleaned, dehydrated and surface film formed in sequence to enhance the adhesion between the silicon wafer and the photoresist, resulting in a pretreated substrate 100.

[0052] 2) Photoresist coating and exposure:

[0053] A layer of PMMA photoresist is uniformly coated on the surface of the pretreated substrate 100 and pre-baked at 370K for 60s to form photoresist layer 101.

[0054] The photoresist layer 101 is exposed on a photolithography machine using a photomask, and then the substrate 100 is developed with a developer to form a pre-pattern for subsequent electrode deposition.

[0055] The photoresist used in this step is AZ5214 photoresist, and the exposure dose is 3.8 W / cm². 2 The development time is 120 seconds.

[0056] 3) Metal electrode sputtering and stripping:

[0057] Metal is sputtered onto the electrode region of the photolithographic substrate 100 by magnetron sputtering. The metal material selected is molybdenum, which has a high melting point and a low coefficient of thermal expansion. Acetone is used to remove excess photoresist and excess metal layer on the photoresist to form a first clamping arm electrode 105, a second clamping arm electrode 106, a first heating unit electrode 108, a second heating electrode 109, and a heating resistance wire 107.

[0058] The first clamping arm electrode 105, the second clamping arm electrode 106, the first heating unit electrode 108, the second heating unit electrode 109, and the heating resistance wire 107 are all 50 nm thick. The sputtering velocity is controlled at 0.6 Å / s, and the vacuum level used is less than 1 × 10⁻⁶. –2 Pa, to ensure the continuity and conductivity of the electrodes.

[0059] 4) Preparation of vanadium dioxide nanowire actuators:

[0060] Before preparing vanadium dioxide nanowires using vapor deposition technology, the quartz boat and the unpolished (rough) quartz substrate must be cleaned. The cleaning process follows the standard procedure for electronic cleaning, which mainly includes sonication with acetone, alcohol, isopropanol, and distilled water for 5 minutes each, followed by drying with nitrogen (N2).

[0061] 0.4 g of commercially available vanadium dioxide powder with a purity of 99% was placed in a quartz boat and then placed in the center of a horizontal tube furnace; an unpolished quartz substrate was placed 6 mm above the reaction source to obtain higher vapor density and deposition temperature.

[0062] First, the furnace tube was evacuated to a basic pressure of 1.33 Pa, and then purged multiple times with argon. Then, the temperature was increased at a rate of 15 °C / min and held at the target temperature of 800 °C for 5 hours. Throughout the process, the pressure was maintained at 1333 Pa and the argon flow rate was 50 sccm. After the reaction was completed, the unpolished quartz substrate with vanadium dioxide nanowires grown on it was removed after the tube furnace cooled to room temperature.

[0063] Then, metal was deposited onto an unpolished quartz substrate with vanadium dioxide nanowires using an electron beam deposition process. The metal material chosen was chromium, which has a significantly different coefficient of thermal expansion from the vanadium dioxide nanowires and is ductile. The deposited metal layer thickness was 150 nm, and the deposition rate was controlled at 0.5 Å / s, with a vacuum level less than 1 × 10⁻⁶. –2 Pa, to ensure the continuity of the metal layer.

[0064] 5) Transfer and fixation of vanadium dioxide nanowire actuators:

[0065] After the vanadium dioxide nanowire actuator 102 is prepared in step 4), it is initially embedded in a quartz substrate. The vanadium dioxide nanowires on the quartz substrate are scraped off with a thin blade and dispersed in 5 ml of ethanol solution. After being dispersed evenly by ultrasonic cleaning, 10 µl is dropped onto a glass slide using a pipette. A tungsten probe first peels the vanadium dioxide nanowire actuator 102 off the glass slide, and then a voltage of 5 V is applied to adsorb the vanadium dioxide nanowire actuator 102 for transfer. The first clamping arm 102.1 and the second clamping arm 102.2 are placed on the first clamping arm electrode 105 and the second clamping arm electrode 106 in two steps, respectively. Then the applied voltage is turned off to release the vanadium dioxide nanowire actuator 102, and the transfer is completed.

[0066] Then, using FIB technology, metallic platinum is deposited on the interface between the end of the vanadium dioxide nanowire brake 102 and the electrode. A rectangular platinum block is deposited on the end of the vanadium dioxide nanowire brake 102 on the first clamping arm electrode 105 and the second clamping arm electrode 106, respectively, to smoothly fix the vanadium dioxide nanowire brake 102 and form the first fixed end 103 and the second fixed end 104.

[0067] Specifically, in this step, the metal block deposited by the first fixed end 103 and the second fixed end 104 using FIB technology is a rectangular block with a length of 2μm, a width of 200nm, and a thickness of 200nm.

[0068] 6) Circuit connection:

[0069] Next, the DC power supply 110 is connected to the first heating unit electrode 108 and the second heating unit electrode 109 through two wires to provide current to the heating resistance wire 107 so that it can work. The capacitance detection circuit 111 is connected to the first clamping arm electrode 105 and the second clamping arm electrode 106 through two probes. The capacitance value change is read by the 4215-CVU equipped in the 4200A-SCS parameter analyzer and the object type recognition algorithm is run in real time with the upper computer software system. The current clamping status (no load / contact / stable clamping) and the predicted type label of the clamped object are displayed intuitively on the software interface, thus obtaining a self-sensing micro tweezers based on vanadium dioxide nanowires.

[0070] The self-sensing microtweezers based on vanadium dioxide nanowires prepared according to this embodiment have the characteristics of large displacement and high frequency response, and can be widely used in the fields of micro-nano electromechanical systems and micro-nano actuators. At the same time, the present invention also has the characteristics of good environmental adaptability, low power consumption, miniaturization and high integration.

[0071] Comparative Example 1:

[0072] The difference between this comparative example and Example 1 is that electron beam deposition of different thicknesses of metallic chromium was used on vanadium dioxide nanowires of the same size to obtain a self-sensing micro tweezer based on vanadium dioxide nanowires in this comparative example.

[0073] Under the same testing environment, an open-loop test was conducted on a self-sensing microtweezer based on vanadium dioxide nanowires. Five sets of experimental data were read and the average value was taken. The results are shown in Table 1.

[0074] Table 1 Experimental Data

[0075]

[0076] As shown in Table 1, the average maximum displacement distance of the vanadium dioxide nanowire actuator with a chromium metal thickness of 150 nm deposited using electron beam deposition in Example 1 of this application is 250 μm, while the average maximum displacement distance of the vanadium dioxide nanowire actuator with a chromium metal thickness of 150 nm deposited using electron beam deposition is 50 μm. Clearly, the thickness of the chromium metal deposited using electron beam deposition cannot be too thin, which is beneficial for increasing the displacement distance of the vanadium dioxide nanowire actuator and also facilitates gripping by micro-tweezers.

[0077] The vanadium dioxide nanowire actuator with a chromium metal thickness of 150 nm deposited using electron beam deposition in Embodiment 1 of this application has an average maximum displacement distance of 250 μm, while the vanadium dioxide nanowire actuator with a chromium metal thickness of 150 nm deposited using electron beam deposition has an average maximum displacement distance of 50 μm. Clearly, the 150 nm thick metal layer provides better actuation performance for the vanadium dioxide nanowire actuator, resulting in a longer displacement distance during bending. This is beneficial for microtweezers to grip larger objects and for increasing the gripping range of the microtweezers.

[0078] Example 2:

[0079] The difference between this embodiment and Embodiment 1 is that:

[0080] The sputtered metal material was molybdenum, and the sputtering rate was adjusted to 0.7 Å / s;

[0081] The metal material used for vapor deposition is chromium, and the vapor deposition rate is adjusted to 0.6 Å / s;

[0082] The pre-baking treatment was carried out at a temperature of 380K for 65 seconds.

[0083] The photoresist exposure dose is 3.6 mW / cm2, and the development time is 80 seconds;

[0084] The target temperature for preparing vanadium dioxide nanowires was 850℃, the holding time was 6 hours, and the argon gas rate was 100 sccm.

[0085] The remaining steps and processes were all the same as in Example 1, resulting in a self-sensing microtweezer based on vanadium dioxide nanowires. The open-loop test was performed on it, and the results were comparable to those in Example 1.

[0086] Example 3:

[0087] The difference between this embodiment and Embodiment 1 is that:

[0088] The sputtered metal material was molybdenum, and the sputtering rate was adjusted to 0.9 Å / s;

[0089] The metal material used for vapor deposition is chromium, and the vapor deposition rate is adjusted to 1.0 Å / s;

[0090] The pre-baking treatment was carried out at a temperature of 378K for 55 seconds.

[0091] The photoresist exposure dose is 4.0 mW / cm2, and the development time is 85 seconds;

[0092] The target temperature for preparing vanadium dioxide nanowires was 780℃, the holding time was 5.5 hours, and the argon gas rate was 75 sccm.

[0093] The remaining steps and processes were all the same as in Example 1, resulting in a self-sensing microtweezer based on vanadium dioxide nanowires. The open-loop test was performed on it, and the results were comparable to those in Example 1.

[0094] Comparative Example 2:

[0095] The difference between this comparative example and Example 1 is that the metallic molybdenum sputtered into the electrode region of the photolithographic substrate 100 in step 4) of Example 1 is replaced with metallic aluminum. The remaining steps are the same as in Example 1, resulting in a self-sensing micro tweezer based on vanadium dioxide nanowires.

[0096] Under the same testing environment, an open-loop test was conducted on a self-sensing microtweezer based on vanadium dioxide nanowires. Five sets of experimental data were read and the average value was taken. The results are shown in Table 2.

[0097] Table 2 Experimental Data

[0098]

[0099] As shown in Table 2, the average maximum temperature after heating with a magnetron sputtering heating wire for molybdenum in Embodiment 1 of this application is 1200°C, while the average maximum temperature after heating with a magnetron sputtering heating wire for aluminum is 400°C. Clearly, the melting point of the metal sputtered by magnetron sputtering cannot be too low; this is beneficial for increasing the maximum operating temperature of the heating wire and for facilitating the gripping of the micro-tweezers.

[0100] In Embodiment 1 of this application, the average maximum temperature reached after heating with a magnetron sputtering heating wire for molybdenum was 1200°C, while the average maximum temperature reached after heating with a magnetron sputtering heating wire for aluminum was 400°C. Clearly, the heating wire formed from molybdenum exhibits better heating performance, a higher melting point, and greater oxidation resistance. This is beneficial for the microtweezers to operate in different environments and for improving the driving speed of the microtweezers.

[0101] Comparative Example 3:

[0102] The difference between this comparative example and Example 1 is that the shape of the heating wire 107 in step 4) of Example 1 is changed from a snake shape to a straight line. The remaining steps are the same as in Example 1, resulting in a self-sensing micro tweezer based on vanadium dioxide nanowires.

[0103] Under the same testing environment, an open-loop test was conducted on a self-sensing microtweezer based on vanadium dioxide nanowires. Five sets of experimental data were read and the average value was taken. The results are shown in Table 3.

[0104] Table 3 Experimental Data

[0105]

[0106] As can be seen from Table 3, the average maximum temperature after heating with a continuous S-shaped heating wire in Embodiment 1 of this application is 1200°C, while the average maximum temperature after heating with a straight heating wire is 800°C. Clearly, the shape of the designed heating wire cannot be too simple; this is beneficial for the concentration of heating temperature and for increasing the maximum heating temperature of the heating wire.

[0107] In Embodiment 1 of this application, the average maximum temperature reached after heating with a continuous S-shaped heating wire was 1200°C, while the average maximum temperature reached after heating with a straight heating wire was 800°C. Clearly, the continuous S-shaped heating wire provides better heating performance, higher temperatures, and a wider heat radiation area, which is beneficial for heating the microtweezers and for increasing their displacement range.

[0108] Comparative Example 4:

[0109] The difference between this comparative example and Example 1 is that, in the preparation of vanadium dioxide nanowires, an unpolished quartz substrate was placed 1 cm above the reaction source, resulting in a self-sensing microtweezer based on vanadium dioxide nanowires in this comparative example.

[0110] Under the same testing environment, an open-loop test was conducted on a self-sensing microtweezer based on vanadium dioxide nanowires. Five sets of experimental data were read and the average value was taken. The results are shown in Table 1.

[0111] Table 4 Experimental Data

[0112]

[0113] As shown in Table 4, the average maximum displacement distance of the vanadium dioxide nanowire actuator in Example 1 of this application, with a distance of 6 mm from the reaction source, is 250 μm, while the average maximum displacement distance of the vanadium dioxide nanowire actuator with a distance of 1 cm from the reaction source is 80 μm. Clearly, the distance from the reaction source should not be too far, which is beneficial for increasing the displacement distance of the vanadium dioxide nanowire actuator and also facilitates gripping by the micro-tweezers.

[0114] The vanadium dioxide nanowire actuator of Example 1 of this application, with a distance of 6 mm from the reaction source, has an average maximum displacement distance of 250 μm, while the vanadium dioxide nanowire actuator with a distance of 1 cm from the reaction source has an average maximum displacement distance of 80 μm. Clearly, the vanadium dioxide nanowires prepared at a distance of 6 mm from the reaction source are longer and have a longer displacement distance when bent. This is beneficial for the microtweezers to grasp larger objects and for increasing the gripping range of the microtweezers.

[0115] In summary, this invention utilizes the metal-insulator phase transition properties of vanadium dioxide nanowires to drive a heterojunction to generate large displacement and fast-response mechanical deformation, successfully constructing a novel micro / nano actuator unit. The design of forming the heterojunction through evaporation of a metal layer effectively amplifies the phase transition stress; the symmetrical integrated assembly method achieves precise and controllable clamping movements. These core design features enable the micro-tweezers to possess low-power actuation, high-frequency response operation, and strong environmental adaptability, significantly improving their operational performance and application potential at the micro / nano scale.

[0116] In addition to the aforementioned optimization measures, the manufacturing method of this invention can be appropriately adjusted to adapt to different application scenarios and needs. For example, different electrode materials and metal layer thicknesses can be selected according to actual needs to reduce the manufacturing cost of the microtweezers and change performance indicators such as the displacement distance of the microtweezers. Electrode materials can be metals such as molybdenum, tungsten, and nickel to reduce the manufacturing cost of the microtweezers. The metal layer can be metals such as chromium, tungsten, and titanium, which have a significantly different coefficient of thermal expansion from vanadium dioxide nanowires, to improve the displacement distance and displacement amplitude of the vanadium dioxide nanowire actuator. Simultaneously, the gripping state of the microtweezers and the type of object gripped can be detected by reading changes in capacitance values, achieving integrated clamping and detection.

[0117] Therefore, the method for fabricating self-sensing microtweezers based on vanadium dioxide nanowires of the present invention has the characteristics of flexibility and adjustability, and can be optimized and adjusted according to actual needs to meet different application scenarios and requirements.

[0118] The above description of the embodiments is provided to facilitate understanding and use of the present invention by those skilled in the art. It is obvious to those skilled in the art that various modifications can be made to the embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A type of micro tweezers based on vanadium dioxide nanowires, characterized in that, include: A silicon substrate (100) has two clamping arm electrodes and two heating unit electrodes respectively arranged on its surface; The vanadium dioxide nanowire actuator (102) includes two clamping arms arranged symmetrically to each other. The clamping arms are a double-layer structure formed by combining vanadium dioxide nanowires with a metal layer, and each clamping arm is electrically connected to a corresponding clamping arm electrode on the substrate silicon wafer (100). A heating unit is disposed on the substrate silicon wafer (100) and electrically connected to the heating unit electrode, for heating the clamping arm to deform the clamping arm and perform a clamping action; A power supply (110) is provided on the substrate silicon wafer (100) and electrically connected to the electrodes of the heating unit; The capacitance detection circuit (111) is electrically connected to the clamping arm electrode connected to the clamping arm, and is used to detect the change in capacitance value during the operation of the micro tweezers and determine its clamping state; the capacitance detection circuit (111) is also connected to a data processing and recognition unit, which integrates a micro-nano object feature database and recognition algorithm to convert the read capacitance signal into object feature information and identify the type of object being clamped.

2. The micro tweezers based on vanadium dioxide nanowires according to claim 1, characterized in that: The heating unit includes a serpentine heating resistance wire (107) with a width of 3~5μm; the thickness of the heating resistance wire (107), the clamping arm electrode and the heating unit electrode are all 40~60nm; when the clamping arm is heated to 68°, the swing amplitude of the initial posture relative to room temperature is 60~90°, and the displacement distance of its end is 150~250μm.

3. The micro tweezers based on vanadium dioxide nanowires according to claim 1, characterized in that: The capacitance detection circuit (111) is 4200A-SCS parameter analyzer matching 4215-CVU, which can detect the minimum capacitance value of 10 -18 f, can detect the capacitance value dynamic change in the process of micro-tweezers empty load, open and close and clamp contact.

4. The micro tweezers based on vanadium dioxide nanowires according to claim 1, characterized in that, The data processing and recognition unit converts the read capacitance signal into object feature information to identify the type of item being gripped. The specific method is as follows: A database of dielectric constants for micro and nano objects was constructed, and common micro and nano objects were entered within the standard dielectric constant range. At the same time, the reference capacitance curves of micro tweezers under no-load conditions as a function of the opening and closing distance of the two gripping arms were entered. A threshold for the rate of change of capacitance is set. When the capacitance value detected in real time changes abruptly and stabilizes within a specific range, the micro tweezers are determined to enter the clamping contact state. An object type recognition algorithm is configured based on the principle of parallel plate capacitor C = ε·S / d, where S is the effective contact area between vanadium dioxide nanowires and the object. The distance d between the two clamping arms is calculated by combining the real-time capacitance measurement value C, the geometric parameters of the micro tweezers and the real-time driving voltage, and the equivalent dielectric constant ε of the clamped object is solved. The equivalent dielectric constant ε obtained by inverse kinematics is matched with the standard dielectric constant in the database. The matching degree is calculated by least squares method or nearest neighbor classification algorithm. When the matching degree is higher than the preset confidence level, the name of the type of the clamped object is output. If no match is found, it is marked as an unknown object and its dielectric characteristics are recorded.

5. A method for preparing micro-tweezers based on vanadium dioxide nanowires, applied to the micro-tweezers based on vanadium dioxide nanowires as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. The silicon wafer with polished and oxidized surface is activated, cleaned, dehydrated and surface film formed in sequence to obtain the pretreated substrate silicon wafer (100). S2. Clamping arm electrodes, heating unit electrodes and heating units are formed on the surface of the pretreated substrate silicon wafer (100) by photolithography, magnetron sputtering and lift-off processes. S3. Prepare vanadium dioxide nanowires, and then deposit a metal layer on the surface of the vanadium dioxide nanowires by electron beam process to form a clamping arm with a double-layer structure of vanadium dioxide nanowires and metal layer. The two clamping arms form a vanadium dioxide nanowire brake (102). S4. Transfer the two clamping arms of the vanadium dioxide nanowire actuator (102) to the corresponding clamping arm electrodes on the substrate silicon wafer (100), and fix the clamping arms to the clamping arm electrodes by depositing the fixing end and realize electrical connection. S5. Then connect the power supply (110) to the heating unit electrode on the substrate silicon wafer (100) and connect the capacitance detection circuit (111) to the clamping arm electrode on the substrate silicon wafer (100) to complete the preparation of the micro tweezers.

6. The method for preparing micro tweezers based on vanadium dioxide nanowires according to claim 5, characterized in that: In step S1, the activation temperature of the silicon wafer is 550~650K, and the activation time is 25~35min.

7. The method for preparing a micro tweezer based on vanadium dioxide nanowires according to claim 5, characterized in that: In step S3, the vanadium dioxide nanowires are single-crystal structures with a diameter of 200-400 nm, a length of 100-150 μm, and an aspect ratio of 375-500; the evaporation thickness of the metal layer is 100-200 nm, the metal used for evaporation is chromium, the electron beam evaporation rate is 0.5-1.0 Å / s, and the vacuum level of the evaporation environment is less than 1 × 10⁻⁶. –2 Pa.

8. The method for preparing a micro tweezer based on vanadium dioxide nanowires according to claim 5, characterized in that: In step S3, the vanadium dioxide nanowires are synthesized by chemical vapor deposition. During synthesis, the temperature is raised to 750℃~850℃ at a heating rate of 15℃ / min and maintained for 5~6 hours, while the gas pressure inside the tube furnace is maintained at 1333Pa. In step S4, a 5V tungsten probe is used to adsorb and transfer the clamping arm. Platinum is deposited on the end of the clamping arm by focused ion beam induced chemical vapor deposition to form a platinum metal rectangular block with a length of 2μm, a width of 200nm, and a thickness of 200nm.

9. The method for preparing a micro tweezer based on vanadium dioxide nanowires according to claim 5, characterized in that: The magnetron sputtering uses metallic phase sputtering materials, with a sputtering power of 100W, a time of 7–15 min, a velocity of 0.6–0.9 Å / s, and a sputtering environment vacuum degree of less than 1 × 10⁻⁶. –2 Pa; the photolithography uses AZ5214 photoresist, with an exposure dose of 3.6~4.0mW / cm² and a development time of 80~120s.

10. The application of the vanadium dioxide nanowire-based microtweezers as described in claim 1, characterized in that, The micro tweezers are used in the fields of micromanipulation and microassembly to precisely grasp and transfer micro- and nano-scale objects, and simultaneously achieve real-time identification of the type of micro- and nano-scale objects being grasped; the micro- and nano-scale objects include one or more of polystyrene microspheres, silica microspheres, and different types of biological cells.

Images