A Micro-Nano Robot Sorting Platform Based on Electrical Impedance Analysis

Abstract

The present invention discloses a micro-nano robot sorting platform based on impedance analysis. The involved micro-nano robot measurement and sorting platform includes: inlet and outlet pipes, a cover plate, a substrate, impedance detection electrodes, and piezoelectric transducers. Among them, acoustic manipulation technology is used to control the movement of micro-nano robots. By adjusting the acoustic pressure field and acoustic streaming field, the movement control of micro-nano robots in two-dimensional or three-dimensional space is realized. The position of micro-nano robots is adjusted before impedance detection, and micro-nano robots are sorted after impedance detection. When the micro-nano robots pass through the microchannel, an alternating current signal is applied to different electrodes, and the change of the response signal when the micro-nano robots pass through is collected. The characteristic parameters of the micro-nano robots are obtained by using impedance measurement technology. The present invention combines acoustic manipulation technology and impedance measurement, and is applicable to the detection and sorting of micro-nano robots of various sizes, shapes and materials, with high speed and high accuracy.

Description

Technical Field

[0001] The present invention relates to a micro-nano electromechanical system, in particular to a micro-nano robot sorting platform based on impedance analysis. Background Art

[0002] Micro-nano motors, also known as micro-nano robots, are a type of micro-nano functional material with self-driving characteristics, with sizes in the micrometer to nanometer scale and shapes including spherical, rod-shaped, tubular, etc. They achieve their own movement at the micro-nano to macroscopic scale through different forms of energy conversion and have research and applications in fields such as environmental monitoring, pollution degradation, biochemical detection, and diagnosis and treatment. However, the size measurement and composition characterization of micro-nano robots often rely on complex and expensive equipment such as optical microscopes, scanning electron microscopes, X-ray diffractometers, and energy spectrometers. Therefore, exploring lower-cost and more convenient micro-nano robot detection and characterization technologies is crucial for the development of this field and the wide application of micro-nano robots. As an important carrier platform for the application of micro-nano robot technology, a microfluidic chip can control the flow of trace fluids and the movement of micro-nano robots in microchannels, so it is also suitable as a carrier platform for micro-nano robot measurement, characterization, and sorting. Microfluidic chips combined with impedance measurement have been studied and applied in flow cytometry and can quickly identify and classify different types of cells without labeling the detection objects. A microfluidic chip platform combined with acoustic manipulation technology can actively control the movement of micro-nano sized particle samples in a microchannel, integrate functional components such as microbubbles and microstructures, and can achieve many functions such as sample mixing, enrichment, and separation in the microchannel. The comprehensive integration of micro-nano particle object measurement and manipulation technologies will help to build a micro-integrated micro-nano robot detection and sorting platform to achieve low-cost, convenient, and accurate measurement and classification of micro-nano robots.

[0003] Impedance testing technology has been widely applied in the field of detection and analysis of micro-nano scale particulate materials. Ai Ye et al. discussed the applications of impedance measurement methods in classifying polystyrene microspheres by particle size, classifying white blood cells, classifying cancer cells, and differentiating cell viability in the micrometer to sub-micrometer scale, and achieved cell sorting by combining surface acoustic wave manipulation technology. However, a narrowed microchannel structure was used in the research, which restricted the movement of cells in the impedance detection area, not only increasing the risk of microchannel blockage but also being unsuitable for measuring hard particles. Yao Jiafeng et al. achieved single-particle position imaging in a microchannel based on various types of support vector machine algorithms by measuring the impedance of cells in the microchannel. Daniel Spencer et al. used multi-frequency impedance measurement to determine the inherent electrical properties of single cells and obtained the conductivity and dielectric constant of cells. However, the microfluidic chip platforms used in these studies contained complex electrode structures, with high processing difficulty and cost.

[0004] A search of existing related patents revealed that a microfluidic chip detection system for single-cell multi-parameter characterization disclosed in Chinese Patent Application No. 201310372705.1 combines a microfluidic chip, an optical detection module, an impedance detection module and a processor, and uses a paired electrode structure to achieve simultaneous characterization of multiple parameters of a single cell. Its microfluidic chip is composed of three layers of substrates aligned and bonded, and the two electrodes that constitute the electrode pair are located at the top and bottom of the microchannel respectively. The structure is relatively complex, the processing precision requirements are high, and the process is difficult. A system and method for distinguishing the shape of tiny particles by microfluidic impedance detection disclosed in Chinese Patent Application No. 201810930070.5 adopts an impedance flow detection method, and realizes the control of particle posture and the distinction of particles of different shapes through pipeline design and flow rate adjustment. The product uses a multi-stage contraction microchannel to guide and limit the posture of particles during the flow process. The narrowest size of the flow channel limits the size of particles that can be detected, and the thinner microchannel increases the risk of blockage during the detection process. In addition, this method of particle manipulation requires precise control of the fluid flow rate in the microchannel, and also requires a longer microchannel size to adjust the particle posture to be consistent with the streamline direction. Chinese Patent Application No. 201910437406.9 discloses a method for detecting yeast morphology and budding ratio based on impedance flow, which uses an impedance flow detection system to collect yeast impedance signals and realize the determination of budding yeast ratio. Similar to the detection of non-spherical cells, micro-nano robots with asymmetric and irregular three-dimensional structures need to maintain a relatively consistent spatial position and posture during detection to ensure the consistency and accuracy of the measurement signal. However, compared with cells, micro-nano robots are harder and less deformable, so it is not suitable to use slit-shaped microchannels to control the position and posture of micro-nano robots, and the dielectrophoresis control method is only applicable to micro-nano robots of specific materials. In addition, the above invention does not provide an effective sorting method after impedance detection, and it is difficult to collect different particles or cells separately based on the test results. The present invention combines electrical impedance analysis and ultrasonic manipulation technology to design a micro-nano robot sorting platform, which can manipulate micro-nano robots of many different materials such as inorganic materials, biomaterials-inorganic hybrid materials, etc. in a non-contact and label-free manner, and can combine electrical impedance analysis to achieve precise measurement and accurate sorting of micro-nano robots.

[0005] In summary, the development of a micro-nano robot sorting platform by combining acoustic manipulation, electrical impedance detection and microfluidics technology has significant practical significance and value. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a micro-nano robot sorting platform based on electrical impedance analysis, provide a more convenient micro-nano robot measurement and characterization method, and solve the problems of complex microfluidic chips and electrode structures used in existing particle impedance measurement technologies, difficult processes, single functions, and difficult manipulation of particles to be measured.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A micro-nano robot sorting platform based on impedance analysis, comprising: a cover plate, a substrate carrying the cover plate, a first electrode, a second electrode, a third electrode, a piezoelectric transducer located at the bottom of the substrate and in close contact with the substrate, and a Y-shaped microchannel located on the lower surface of the cover plate; the Y-shaped microchannel includes an inlet channel, a first outlet channel branched from the inlet channel to one side, and a second outlet channel branched from the inlet channel to the other side; the first electrode, the second electrode, and the third electrode all extend within the inlet channel, and the first electrode is located between the second electrode and the third electrode; the micro-nano robots contained in the conductive liquid medium flow in through the inlet channel and flow out through the first outlet channel or the second outlet channel; when the micro-nano robots pass through the inlet channel during the sampling process, the substrate is driven to resonate by the piezoelectric transducer to generate a sound pressure field and an acoustic streaming field, and the acoustic radiation force and the acoustic streaming are used to adjust the spatial position of the micro-nano robots in the direction perpendicular to the fluid flow direction; when the micro-nano robots pass through the detection area between the second electrode and the third electrode, a sinusoidal alternating current signal is applied by the first electrode, and the second electrode and the third electrode collect electrical signals for analyzing the signal changes generated when the micro-nano robots pass through the detection area between the second electrode and the third electrode, so as to extract the characteristic parameters of the micro-nano robots.

[0009] Further, the micro-nano robots are sorted according to the peak current |I Peak | (unit: A) measured between the second electrode and the third electrode. When the current |I Peak | ∈ [i1, i2], the micro-nano robots are considered qualified, and when the current is outside this range, the micro-nano robots are considered unqualified; where i1 and i2 are the calibrated current change ranges.

[0010] Further, a number of inwardly convex and parallel comb-like microstructures are provided on an inner side wall of the second outlet channel. Before sorting, the vibration of the microstructures is not excited, and the flow rate of the liquid medium in the second outlet channel is slower than that in the first outlet channel. When the micro-nano robots move to the branch, they are sorted. If the micro-nano robots are qualified, the vibration of the microstructures is not excited, and the micro-nano robots flow into the first outlet channel; if the micro-nano robots are unqualified, the vibration of the microstructures is controlled to increase the flow rate of the fluid in the second outlet channel until the flow rate of the fluid in the second outlet channel is faster than that in the first outlet channel, so that the micro-nano robots can be pulled into the second outlet channel.

[0011] Further, the comb-like microstructures have hydrophilic or hydrophobic surfaces. When the surface of the microstructures is hydrophilic, the injected liquid can completely fill the space between adjacent teeth; when the surface of the microstructures is hydrophobic, bubbles are generated between adjacent teeth when the liquid is injected.

[0012] Further, when a modulation signal is applied to the first electrode for measurement, the micro-nanorobots are sorted according to the measured current waveform between the second electrode and the third electrode; by measuring more than 1,000 micro-nanorobots of standard size and material, a measurement data set of standard qualified micro-nanorobots is obtained, and using an artificial neural network training model, this model can be used for the detection and identification of micro-nanorobots.

[0013] Further, it is characterized in that the cover plate is made of polydimethylsiloxane, and the microfluidic channel is processed by a micro-casting process.

[0014] Further, the shapes of the sortable micro-nanorobots include spherical, ellipsoidal, tubular, conical-tubular, rod-shaped, and polyhedral.

[0015] Further, the acoustic manipulation technology is used to realize the motion trajectory control and sorting of micro-nanorobots, and the impedance measurement technology is used to obtain the characteristic parameters of micro-nanorobots.

[0016] Further, the piezoelectric transducer is driven by the inverse piezoelectric effect, and the overall resonance of the sorting platform is excited to realize the bending and torsional vibration modes of the substrate, and to excite the vibration of the micro-structures or the vibration of the bubbles in the cover plate, thereby generating an acoustic pressure field or an acoustic streaming field; the acoustic pressure field or the acoustic streaming field is used to realize the motion control of micro-nanorobots in two-dimensional or three-dimensional space, including adjustment before impedance detection, and making the micro-nanorobots pass through the detection area along the same trajectory during impedance detection; after impedance detection, the micro-nanorobots are sorted according to the extracted characteristic parameters of the micro-nanorobots.

[0017] The present invention has the following beneficial effects:

[0018] 1. Design a micro-nanorobot intelligent detection and sorting platform based on microfluidic chip technology, which is small in size, low in cost, and easy to use. The chip body is a double-layer structure of a substrate and a cover plate, and the integrated electrodes are coplanar parallel linear electrodes. The comb-like micro-structures in the microfluidic channel and the main body of the microfluidic channel are prepared by a micro-casting process together; the simplified structure and processing technology avoid the complex processes and alignment and assembly processes required for multi-layer structure chips or multi-layer electrodes during processing, and the processing cost and process difficulty are lower.

[0019] 2. Use the acoustic manipulation technology to control the attitude and motion trajectory of micro-nanorobots when passing through the microfluidic channel, weakening the dependence of the impedance measurement signal on the motion attitude and trajectory of micro-nanorobots, which helps to improve the detection accuracy and detect micro-nanorobots with asymmetric structures; compared with the dielectrophoresis manipulation method of micro-nanorobots, it avoids the restriction on the material properties of micro-nanorobots, and compared with the inertial fluid focusing method of micro-nanorobots, it simplifies the structure of the microfluidic channel. Combining the comb-like micro-structures or bubbles in the microfluidic channel to control the diversion of micro-nanorobots at the branch of the microfluidic channel can separate and collect different micro-nanorobots after impedance detection, which is convenient for subsequent experiments.

[0020] 3. Measuring parameters such as the shape, size, material, and structure of micro-nano robots using the electrical impedance detection method is more convenient and faster than methods such as energy dispersive spectroscopy and scanning electron microscopy observation. By measuring under excitation electrical signals at multiple frequencies simultaneously, relevant information on multiple different parameters can be extracted in a single measurement, and the detection results are accurate. It is possible to detect the target physical and chemical properties without staining or labeling, and it is applicable not only to the detection of inorganic material artificial micro-nano robots but also to the detection of micro-nano robots with a bio-material-inorganic hybrid structure. The integrated integration of multiple experimental requirements such as the detection, sorting, and collection of micro-nano robots on the sorting platform has been realized. Description of the Drawings

[0021] Figure 1 It is a three-dimensional structure diagram of a micro-nano robot sorting platform based on impedance analysis;

[0022] Figure 2 It is an exploded view of the structure of a micro-nano robot sorting platform based on impedance analysis;

[0023] Figure 3 It is a resonant mode of the micro-nano robot sorting platform;

[0024] Figure 4 It is the sound pressure distribution on multiple cross-sections in a rectangular cross-section microchannel;

[0025] Figure 5 It is the sound pressure equipotential surface in a rectangular cross-section microchannel;

[0026] Figure 6 Schematic diagram of a partially enlarged three-electrode;

[0027] Figure 7 It is a three-dimensional model of a spherical micro-nano robot passing through a microchannel;

[0028] Figure 8 It is the electric field lines of a spherical micro-nano robot passing through a microchannel;

[0029] Figure 9 It is the current change of a spherical micro-nano robot passing through a microchannel;

[0030] Figure 10 It is a schematic diagram of a partially enlarged comb-shaped microstructure;

[0031] Figure 11 It is a resonant mode of the micro-nano robot sorting platform;

[0032] Figure 12 It is a schematic diagram of a partially enlarged five-electrode;

[0033] Figure 13 It is a schematic diagram of a comb-shaped microstructure fixing a bubble in a partially enlarged view;

[0034] Figure 14 is the sound pressure distribution around the bubble during resonance;

[0035] Figure 15 is the velocity field around the bubble during resonance. Specific implementation manner

[0036] For the convenience of understanding by those skilled in the art, the present invention will be further described below in conjunction with Embodiments 1 and 2 and the accompanying drawings. The content mentioned in the implementation manner does not limit the present invention.

[0037] A micro-nano robot sorting platform based on impedance analysis, and its Embodiment 1 is as follows:

[0038] As Figure 1 、 2 shown, the present invention discloses a micro-nano robot sorting platform based on impedance analysis. The platform includes two drain pipes 1, 2, a liquid inlet pipe 3, a cover plate 4, a substrate 5 carrying the cover plate 4, a first electrode 6, a second electrode 7, a third electrode 8, a piezoelectric transducer 9 located at the bottom of the substrate 5 and in close contact with the substrate 5, and a Y-shaped microchannel on the lower surface of the cover plate 4; the microchannel includes an inlet channel 18, a first outlet channel 19 branched from the inlet channel 18 to one side, and a second outlet channel 20 branched from the inlet channel 18 to the other side; the first electrode 6, the second electrode 7, and the third electrode 8 all extend within the inlet channel 18, and the first electrode 6 is located between the second electrode 7 and the third electrode 8. The liquid inlet pipe 3 is connected to the inlet end of the inlet channel 18. The outlet end of the first outlet channel 19 is connected to the drain pipe 1, and the outlet end of the second outlet channel 20 is connected to the drain pipe 2. The diameters of the drain pipes 1, 2, and the liquid inlet pipe 3 are 0.5 mm, and the material is stainless steel; the size of the cover plate 4 is 18×10×1.5 mm, and the material is polydimethylsiloxane (PDMS); the size of the substrate 5 is 25×15×0.5 mm, and the material is quartz glass; the distances between the first electrode 6 and the second electrode 7, and between the first electrode 6 and the third electrode 8 are both 20 μm; the size of the piezoelectric transducer 9 is 15×5×0.5 mm, and the material is lead zirconate titanate.

[0039] The preparation of the cover plate 4 first requires customizing a positive mold for photolithography processing: Spin-coat a positive SU-8 photoresist on a cleaned silicon wafer. After thermal baking and curing, use a mask plate with microchannels and comb-shaped microstructures for ultraviolet exposure on a lithography machine. Then, wash away the non-exposed part of the photoresist layer in the developer to form a convex mold including microchannels and comb-shaped microstructures on the silicon wafer. Finally, sputter a 100-200 nm silicon dioxide layer on the surface for protection. The positive mold can be used repeatedly after preparation. PDMS and the curing agent are mixed evenly at a ratio of 10:1. After removing air bubbles, pour it on the positive mold prepared by photolithography processing. After curing at 60 °C for 90 minutes, it can be peeled off to obtain the cover plate 4 containing rectangular cross-section microchannels and comb-shaped microstructures. Punch holes at the liquid drainage and liquid inlet positions to insert the liquid drainage pipes 1, 2 or the liquid inlet pipe 3. The liquid inlet pipe is simultaneously connected to an injection pump for sample injection, and the liquid drainage pipe is simultaneously connected to a collection container for collecting the micro-nanorobots after detection and separation.

[0040] The preparation of the electrodes requires first sputtering a metal layer on the substrate, and then using a mask plate containing electrode patterns, combined with photolithography technology and deep reactive ion etching technology to prepare a Cr-Au double-layer electrode on a quartz glass substrate. The thickness of the Cr layer is 30 nm, and the thickness of the Au layer is 100 nm. The first electrode 6 is connected to the signal output terminal of the lock-in amplifier, and the second electrode 7 and the third electrode 8 are connected to the differential input port of the lock-in amplifier through a transimpedance amplifier.

[0041] The piezoelectric transducer 9 is pasted on the substrate using epoxy resin glue and is connected to a signal generator and a power amplifier.

[0042] The phosphate buffer solution (PBS) containing spherical micro-nanorobots (5 μm microspheres, with the main body being polystyrene microspheres) flows in through the liquid inlet pipe 3 and flows out through the liquid drainage pipe. When the micro-nanorobots pass through the microchannels between the cover plate 4 and the substrate 5, a sinusoidal alternating current signal is applied by the first electrode 6, and the second electrode 7 and the third electrode 8 collect the electrical signals for analyzing the characteristic parameters of the micro-nanorobots. The piezoelectric transducer 9 drives the resonance of the micro-nanorobot sorting platform to generate a sound pressure field and a sound flow field to realize the position adjustment and sorting of the micro-nanorobots.

[0043] After the micro-nanorobots enter the liquid inlet channel 18, their movement trajectories are first adjusted using acoustic manipulation technology. As Figure 3 shown is an out-of-plane bending vibration mode of the micro-nanorobot sorting platform caused by the vibration induced by the inverse piezoelectric effect of the piezoelectric ceramic under the excitation of an ultrasonic frequency electrical signal. In this mode, the deformation amplitudes of the substrates on both sides of the liquid inlet channel 18 are symmetric and in opposite directions, and the sound pressure node line coincides with the long axis direction of the liquid inlet channel 18 and is located at the central longitudinal section of the liquid inlet channel 18 (xz plane), making the micro-nanorobots tend to move along the longitudinal section of the liquid inlet channel 18 under the action of fluid flow and acoustic radiation force. Take a small section of the liquid inlet channel 18 for analysis. Divide it into left and right parts along the longitudinal section (xz plane). By Figure 4 、5 As shown, when the amplitudes of the left and right parts of the substrate at the bottom of the liquid inlet channel 18 are symmetric and in opposite directions, the sound pressure nodal lines on the cross-section (yz plane) of the liquid inlet channel 18 are distributed in a "plus" shape, and the positions of the sound pressure nodal lines on the cross-sections at multiple different positions are the same. In three-dimensional space, the sound pressure nodal plane is two mutually orthogonal longitudinal sections of the liquid inlet channel 18. Thus, by adjusting the excitation frequency of the piezoelectric transducer, a sound pressure field can be constructed in the liquid inlet channel 18, enabling the micro-nano robot to move along the sound pressure nodal lines or nodal planes, regulating the movement trajectory of the micro-nano robot in two-dimensional or three-dimensional space, and ensuring the trajectory consistency and detection accuracy when it passes through the impedance detection area.

[0044] Micro-nano robots with different materials and structures have different conductivities and dielectric constants. When the micro-nano robot passes through the detection area between the second electrode 7 and the third electrode 8, different impedance values |Z| (unit: Ω) can be measured. The measured peak value of the instantaneous impedance can be used for the discrimination and identification of micro-nano robots. For example, micro-nano robots made of metal materials usually have relatively small impedance values, while micro-nano robots made of polymer materials usually have relatively high impedance values. In addition, due to Ohm's law |Z| = |U| / |I|, during the measurement process with a constant excitation signal voltage and frequency, the impedance value is inversely proportional to the current. The current |I| when the micro-nano robot passes through the detection area can also be directly detected using a lock-in amplifier to identify the micro-nano robot. For the measurement of tubular or rod-shaped micro-nano robots, the length of the micro-nano robot is related to the waveform width of the corresponding signal during detection. Since the response signal when the micro-nano robot passes through the detection area is approximately a double-peak Gaussian curve, the Gaussian curve function can also be extracted through curve fitting, and the corresponding relationship between the parameters of the double-peak Gaussian curve and the size of the micro-nano robot can be established to achieve the measurement of the characteristic parameters of the micro-nano robot.

[0045] As Figure 6 Shown is a partial enlarged view of the three-electrode structure used for detecting the impedance of a micro-nano robot. During detection, a sinusoidal alternating current signal with a frequency of 1 MHz and a peak-to-peak value of 1 V is applied to the first electrode 6 using a lock-in amplifier. The second electrode 7 and the third electrode 8 collect the signal changes generated when the micro-nano robot passes through. The second electrode 7 and the third electrode 8 are connected to a differential input port of the lock-in amplifier through a transimpedance amplifier, and the signal changes are analyzed and processed on a computer. As Figure 7 Shown is a three-dimensional model of a spherical micro-nano robot 11 passing through the liquid inlet channel 18. At this time, the electric field lines at the longitudinal section of the liquid inlet channel 18 are as Figure 8 shown, and the current change when the spherical micro-nano robot passes through is as Figure 9 shown. When the micro-nano robot passes through, it will affect the distribution of the electric field lines and the electrical signals detected on the second electrode 7 and the third electrode 8. Different micro-nano robots have different effects on the electrical signals, and there are differences between the measured signals. Thus, the micro-nano robots can be identified. Here, taking the measured peak current |IPeak |(Unit: A) Sort the micro-nanorobots. When the current is i2, the micro-nanorobots are considered "qualified". When the current is, the micro-nanorobots are considered "unqualified". Here, i1 and i2 are the calibrated current change ranges measured using standard micro-nanorobots.

[0046] After the computer detects the characteristic parameters of the micro-nanorobots, it can control the micro-nanorobot sorting platform to perform sorting, so that different types of micro-nanorobots flow out from different outlets of the sorting platform. As Figure 10 shown, the internal structures of the first liquid outlet channel 19 and the second liquid outlet channel 20 are different, so that the flow velocities of the liquid medium in the first liquid outlet channel 19 and the second liquid outlet channel 20 are different. Specifically, a number of inwardly convex and parallel comb-like microstructures 10 are provided on an inner side wall of the second liquid outlet channel 20. The microstructures 10 vibrate with the overall vibration of the micro-nanorobot sorting platform under the vibration excitation of a specific frequency of the piezoelectric ceramic. The generated flow field can regulate the flow velocity of the tributary where it is located, and guide the micro-nanorobots detected in the previous step to move towards one of the branches of the flow channel branch, realizing the sorting of micro-nanorobots. Before sorting, the vibration of the microstructures is not excited. Since there are microstructures in the second liquid outlet channel 20 that hinder the fluid flow, the flow velocity of the liquid medium in the second liquid outlet channel 20 is slower than that in the first liquid outlet channel 19. When the micro-nanorobots move to the branch, they are sorted. If the micro-nanorobots are qualified, the vibration of the microstructures can be not excited, and the micro-nanorobots flow naturally into the first liquid outlet channel 19 without microstructures. If the micro-nanorobots are unqualified, the vibration of the comb-like microstructures (10) is controlled to accelerate the fluid flow velocity of the second liquid outlet channel 20 until the fluid flow velocity of the second liquid outlet channel 20 is faster than that of the first liquid outlet channel 19, so that the micro-nanorobots can be pulled into the second liquid outlet channel 20, thereby sorting out the unqualified micro-nanorobots. After the micro-nanorobots enter the second liquid outlet channel 20, the vibration of the microstructures is stopped, and the sorting is performed again when the next micro-nanorobot moves to the branch.

[0047] A micro-nanorobot sorting platform based on impedance analysis, and its second embodiment is as follows:

[0048] Select the same drain pipes 1, 2, inlet pipe 3, substrate 5, piezoelectric transducer 9 as in Embodiment 1, the same cover plate material, size and processing technology, and the same electrode material and processing technology to prepare the micro-nanorobot sorting platform. Among them, in Embodiment 2, different acoustic manipulation parameters for micro-nanorobots are selected, and another electrode structure for impedance detection of micro-nanorobots and a micro-nanorobot sorting method using bubble vibration to generate a flow field are provided.

[0049] After the micro-nanorobots enter the microchannel, their movement trajectories are first adjusted using acoustic manipulation technology. As Figure 11Shown is an out-of-plane bending vibration mode of a micro-nano robot sorting platform surface caused by the inverse piezoelectric effect of a piezoelectric ceramic under the excitation of an alternating current signal with an ultrasonic frequency. Compared with Figure 3 the vibration mode shown, Figure 11 the vibration mode shown is generated under a higher frequency excitation. The nodal line distribution of the substrate deformation is more complex. There is a nodal line along the long axis direction of the microchannel, and multiple nodal lines appear perpendicular to the long axis direction of the microchannel, dividing the micro-nano robot intelligent sorting platform into multiple regions. The amplitudes of the regions on both sides of each nodal line are symmetric, and the vibration directions are opposite. The micro-nano robot tends to move along the longitudinal section of the microchannel. For this complex vibration mode under ultrasonic excitation, when the acoustic pressure nodal line coincides with the long axis direction of the microchannel, the movement of the micro-nano robot in the microchannel along this direction can be controlled. For different microchannels and electrode structures, different vibration modes can be obtained by adjusting the ultrasonic excitation frequency to meet different micro-nano robot manipulation requirements. There should be a significant difference between the frequency of the ultrasonic drive signal and the frequency of the impedance test to prevent the interference of the ultrasonic drive signal on the impedance measurement.

[0050] When detecting the impedance of a micro-nano robot, a five-electrode structure as shown in Figure 12 is selected, including three first electrodes 14, 15, 16, and a second electrode 12 and a third electrode 13. First, measure the impedance spectrogram of a single micro-nano robot. Adjust the micro-nano robot between electrodes 14 and 15, and use a lock-in amplifier to apply a swept-frequency electrical signal with a peak-to-peak voltage of 1 V and a frequency range of 10 Hz - 50 MHz to electrode 14. Connect the signal on electrode 15 to the lock-in amplifier through a transimpedance amplifier for measurement. Select a suitable frequency based on the measured frequency-magnitude spectrum and the characteristics of the micro-nano robot, and measure simultaneously at multiple frequencies to characterize the micro-nano robot. Here, three sine alternating current signal components of 1 MHz, 10 MHz, and 20 MHz are used, and the electrical signal obtained by frequency modulation and superposition of the three signals is applied to electrodes 14, 15, and 16 simultaneously by a lock-in amplifier. Electrodes 12 and 13 collect the signal changes when the micro-nano robot passes through. The two electrodes are connected to a differential input port of the lock-in amplifier through a transimpedance amplifier, and the signal changes are analyzed and processed on a computer. When analyzing the signal changes of the micro-nano robot passing through the electrode region, the internal oscillators of 1 MHz, 10 MHz, and 20 MHz of the lock-in amplifier are used as references respectively to demodulate the measured signals to obtain the corresponding signal components.

[0051] Micro-nanorobots with different materials, structures, and sizes can measure different waveforms when passing through the detection area, and the response signals of the same micro-nanorobot passing through the detection area can demodulate three different frequency components at 1 MHz, 10 MHz, and 20 MHz. By measuring with more than 1000 micro-nanorobots of standard size and material, obtaining the measurement dataset of standard qualified micro-nanorobots, and using an artificial neural network training model, this model can be used for the detection and identification of micro-nanorobots.

[0052] The micro-nanorobots that have completed the detection are sorted using the comb-like micro-structure 10 - micro-bubble 17 structure as shown in Figure 13 . Before the cover plate 4 is sealed with the substrate 5, it is treated by plasma cleaning, and its surface changes from hydrophobic to hydrophilic. Therefore, in Embodiment 1, the liquid can completely fill the space between two adjacent teeth in the comb-like micro-structure when injected into the micro-channel. In Example 2, keeping it at 45 °C overnight can restore the hydrophobic property of the surface, and stable bubbles are generated between the comb-like micro-structures due to the hydrophobic property of the surface when the liquid is injected. When the bubble vibrates under the excitation of the ultrasonic frequency, the total sound pressure around it is as shown in Figure 14 , and the velocity field is as shown in Figure 15 . The flow field generated when the bubble resonates is very intense, far exceeding the flow field generated by the vibration of the micro-structure itself, and can be used to sort large-sized micro-nanorobots.

[0053] Before sorting, the vibration of the comb-like micro-structure 10 - micro-bubble 17 structure is not excited. Due to the presence of micro-structures and bubbles in one branch hindering fluid flow, the flow rates of the two branches of the Y-shaped micro-channel are one fast and one slow. When the micro-nanorobot moves to the branch, it is sorted. If the micro-nanorobot is qualified, the vibration of the micro-structure - bubble can be not excited, and the micro-nanorobot can flow naturally into the branch without micro-structures. If the micro-nanorobot is unqualified, the vibration of the comb-like micro-structure 10 - micro-bubble 17 structure is controlled, and the vortex flow field generated by the bubble resonance is used to attract the micro-nanorobot to move towards the bubble, pulling the micro-nanorobot into this branch to sort out the unqualified micro-nanorobots. After the micro-nanorobot enters the branch channel, the excitation is stopped, and the next micro-nanorobot is sorted again when it moves to the branch.

[0054] The specific application ways of the present invention are numerous. The above description is only the preferred embodiment of the present invention; it should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements can be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A micro-nano robot sorting platform based on impedance analysis, characterized in that, It includes: a cover plate (4), a substrate (5) for carrying the cover plate (4), a first electrode (6), a second electrode (7), a third electrode (8), a piezoelectric transducer (9) located at the bottom of the substrate (5) and in close contact with the substrate (5), and a Y-shaped microchannel on the lower surface of the cover plate (4); the Y-shaped microchannel includes an inlet channel (18), a first outlet channel (19) branched from the inlet channel (18) to one side, and a second outlet channel (20) branched from the inlet channel (18) to the other side; the first electrode (6), the second electrode (7), and the third electrode (8) all extend within the inlet channel (18), and the first electrode (6) is located between the second electrode (7) and the third electrode (8); the micro-nanorobot contained in the conductive liquid medium flows in through the inlet channel (18) and flows out through the first outlet channel (19) or the second outlet channel (20); when the micro-nanorobot passes through the inlet channel (18), the piezoelectric transducer (9) drives the substrate (5) to resonate, generating an acoustic pressure field and an acoustic streaming field, and using acoustic radiation force and acoustic streaming to adjust the spatial position of the micro-nanorobot in the direction perpendicular to the fluid flow direction; when the micro-nanorobot passes through the detection area between the second electrode (7) and the third electrode (8), a sinusoidal alternating current signal is applied by the first electrode (6), and the second electrode (7) and the third electrode (8) collect electrical signals for analyzing the signal change generated when the micro-nanorobot passes through the detection area between the second electrode (7) and the third electrode (8), so as to extract the characteristic parameters of the micro-nanorobot; A number of inwardly convex and parallel comb-shaped microstructures (10) are provided on an inner side wall of the second outlet channel (20). Before sorting, the vibration of the microstructures is not excited. The flow rate of the liquid medium in the second outlet channel (20) is slower than that in the first outlet channel (19). When the micro-nanorobot moves to the branch, it is sorted. If the micro-nanorobot is qualified, the vibration of the microstructures is not excited, and the micro-nanorobot flows into the first outlet channel (19); if the micro-nanorobot is unqualified, the vibration of the microstructures (10) is controlled to accelerate the fluid flow rate in the second outlet channel (20) until the fluid flow rate in the second outlet channel (20) is faster than that in the first outlet channel (19), so that the micro-nanorobot can be pulled into the second outlet channel (20).

2. The micro-nano robot sorting platform based on impedance analysis according to claim 1, characterized in that The peak current |I measured between the second electrode (7) and the third electrode (8) Peak | is used to sort the micro-nano robots. The current |I Peak | ∈ [i1, i2] indicates that the micro-nano robot is qualified, and the current | outside this range indicates that the micro-nano robot is unqualified; where i1 and i2 are the calibrated current change ranges.

3. The micro-nano robot sorting platform based on impedance analysis according to claim 1, wherein The comb-shaped microstructures have hydrophilic or hydrophobic surfaces. When the surface of the microstructures is hydrophilic, the injected liquid can completely fill the space between adjacent teeth; when the surface of the microstructures is hydrophobic, air bubbles (17) are generated between adjacent teeth when the liquid is injected.

4. The micro-nano robot sorting platform based on impedance analysis according to claim 1, characterized in that, When a modulation signal is applied to the first electrode (6) for measurement, the micro-nanorobot is sorted according to the current waveform measured between the second electrode (7) and the third electrode (8); more than 1000 standard-sized and standard-material micro-nanorobots are used for measurement to obtain a measurement data set of standard qualified micro-nanorobots, and an artificial neural network training model is used, and then this model can be used for the detection and identification of micro-nanorobots.

5. The micro-nano robot sorting platform based on impedance analysis according to claim 1, wherein The cover plate (4) is made of polydimethylsiloxane, and the microchannel is processed by a microcasting process.

6. The micro-nano robot sorting platform based on impedance analysis according to claim 1, wherein the shapes of the sortable micro-nano robots (11) include spherical, ellipsoidal, tubular, conical tubular, rod-shaped, and polyhedral.

7. The micro-nano robot sorting platform based on impedance analysis according to claim 1, which uses acoustic manipulation technology to achieve the motion trajectory control and sorting of micro-nano robots, and uses impedance measurement technology to obtain the characteristic parameters of micro-nano robots.

8. The micro-nano robot sorting platform based on impedance analysis according to claim 7, wherein The piezoelectric transducer (9) is driven by the inverse piezoelectric effect and excites the overall resonance of the sorting platform to realize the bending and torsional vibration modes of the substrate (5), and excite the vibration of the microstructures (10) or the vibration of the bubbles (17) in the cover plate (4), thereby generating an acoustic pressure field or an acoustic streaming field; the motion control of the micro-nano robots in two-dimensional or three-dimensional space is realized by using the acoustic pressure field or the acoustic streaming field, including adjustment before impedance detection and making the micro-nano robots pass through the detection area along the same trajectory during impedance detection; after impedance detection, the micro-nano robots are sorted according to the extracted characteristic parameters of the micro-nano robots.

9. The micro-nano robot sorting platform based on impedance analysis according to claim 7, characterized in that, The computer controls the internal oscillator of the lock-in amplifier to generate an alternating current signal and apply it to the first electrode (6), and connects the signals on the second electrode (7) and the third electrode (8) to the differential input terminal of the lock-in amplifier through a transimpedance amplifier for signal analysis at one or more frequencies; the computer determines the shape, size, and material parameters of the micro-nano robots according to the impedance analysis results, and controls the signal generator to generate signals according to the determination results to excite the vibration of the piezoelectric transducer (9).

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