Particle trapping device and method based on a total-metamaterial super-surface

Abstract

The application provides a particle trapping device and method based on a full dielectric super surface, the particle trapping device based on the full dielectric super surface comprises a medium substrate layer and a resonance layer on the surface of the medium substrate layer, the resonance layer comprises a plurality of resonance units arranged in an array, the medium substrate layer is made of quartz material, the resonance units are made of silicon material, the resonance units are standard cylinders, the height of the standard cylinder is 2.5-3.1 times the radius of the bottom surface of the standard cylinder, and the array period of the resonance units is 2.7-3.3 times the radius of the bottom surface of the standard cylinder. The particle trapping device and method based on the full dielectric super surface can realize high Q value and stable particle trapping under the influence of different incident angles and processing errors.

Description

Technical Field

[0001] This invention relates to the field of metasurface and optical tweezers technology, and in particular to a particle trapping device and method based on an all-dielectric metasurface. Background Technology

[0002] Optical trapping technology is a technique for non-contact manipulation of tiny particles using the gradient force of an optical field. Due to its high precision, low damage, and non-invasive nature, it has been widely applied in fields such as biomedical detection, cell manipulation, and the assembly of micro / nano materials. Early research showed that using high numerical aperture objectives to tightly focus laser light can achieve stable trapping of micrometer-scale particles, and this technology is gradually being extended to the fine manipulation of biological objects such as bacteria and cells.

[0003] However, traditional optical tweezers are constrained by diffraction limits, making it difficult to effectively compress the light field to a subwavelength scale volume. This results in low capture efficiency for nanoparticles and typically requires high incident power, which is not conducive to practical applications. To improve nanoscale capture capabilities, plasmonic nanotweezers have attracted widespread attention. This approach uses a metal nanoantenna to excite surface plasmonic resonance, localizing the electromagnetic field in a nanoscale "hot spot" region, thereby forming a strong capture potential well and achieving subwavelength particle manipulation.

[0004] However, the metallic materials in plasma nanotweezers have inherent ohmic losses, which can easily generate significant photothermal effects, leading to parasitic thermophoresis and fluid convection, and reducing capture stability. At the same time, local overheating may also cause irreversible thermal damage to the captured object, which is particularly detrimental to the long-term manipulation and viability maintenance of thermosensitive biological samples such as cells.

[0005] Compared to metallic structures, all-dielectric nanostructures offer advantages such as low absorption loss and low temperature rise, enabling optical field manipulation while reducing the risk of thermal damage. Therefore, they have significant application value in the safe capture of biological samples. However, existing all-dielectric nanotweezers generally suffer from limited resonance quality factor (Q-factor) and insufficient local field enhancement capabilities, and their trapping potential and low-power performance still require further improvement.

[0006] To address these issues, continuous-spectrum bound states (BICs) have been increasingly introduced into all-dielectric metasurfaces. Ideal BIC modes possess quality factors approaching infinity, but are typically difficult to couple directly with free space. Existing techniques often transform ideal BICs into radiation-coupled quasi-continuous-domain bound states (quasi-BICs) through oblique-incidence excitation or breaking in-plane symmetry, thereby achieving high Q-factor resonances and strong local field enhancements, ultimately improving the nanoparticle trapping capability.

[0007] However, most existing quasi-BIC implementations rely on geometrically asymmetric designs, making the devices highly sensitive to fabrication errors, structural parameter perturbations, and changes in the incident angle. This makes it difficult to meet the stable and universal optical trapping requirements in complex environments. For example, the paper "Research on Optical Chiral Screening Based on Quasi-Continuous Domain Bound State Metasurfaces" discloses a metasurface structure that enhances optical tweezers trapping capability using the quasi-BIC principle. By designing a silicon dielectric cylindrical array with wedge-shaped notches on a silicon dioxide substrate, the quasi-BIC mode is excited by in-plane symmetry breaking, forming a strong localized optical field in the near field, and successfully achieving stable trapping of polystyrene particles with a radius of about 1 nm.

[0008] However, the aforementioned metasurface structures are highly dependent on artificially introduced geometrically broken structures. Although high Q values ​​and field enhancements can be achieved under ideal simulation conditions, their resonance characteristics are extremely sensitive to micro / nano fabrication errors. Even small dimensional deviations or notch morphology distortions can lead to a sharp drop in Q values ​​and field localization failure. Furthermore, broken symmetry structures are usually accompanied by strong angle and polarization dependencies, and even slight fluctuations in incident light conditions can disrupt the spatial stability of the trapped potential well.

[0009] Therefore, there is an urgent need for a new type of particle trapping device that can break free from dependence on fragile symmetry-broken structures and has intrinsic robustness to incident conditions. Summary of the Invention

[0010] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a particle trapping device and method based on an all-dielectric metasurface, which does not rely on a symmetry-broken structure and achieves high Q value and stable particle trapping under different incident angles and processing errors.

[0011] In a first aspect, the present invention provides a particle trapping device based on an all-dielectric metasurface, comprising a dielectric substrate layer and a resonant layer located on the surface of the dielectric substrate layer. The resonant layer comprises a plurality of resonant units arranged in an array. The dielectric substrate layer is made of quartz material, the resonant units are made of silicon material, and the resonant units are standard cylinders. The height of the standard cylinder is 2.5 to 3.1 times the base radius of the standard cylinder, and the array period of the resonant units is 2.7 to 3.3 times the base radius of the standard cylinder.

[0012] In one implementation of the first aspect, the base radius of the standard cylinder is 260nm~320nm, the height of the standard cylinder is 750nm~850nm, and the array period of the resonant unit is 830nm~860nm.

[0013] In one implementation of the first aspect, the base radius of the standard cylinder is 290 nm, the height of the standard cylinder is 805 nm, and the array period of the resonant unit is 850 nm.

[0014] In one implementation of the first aspect, the thickness of the dielectric substrate layer is 1 μm to 3 μm.

[0015] In one implementation of the first aspect, the refractive index of the dielectric substrate layer for light with a wavelength of 700nm to 1600nm is not higher than 1.47, and the resonant unit for light with a wavelength of 700nm to 1600nm is not lower than 3.45.

[0016] In one implementation of the first aspect, the refractive index of the dielectric substrate layer for light with a wavelength of 700nm to 1600nm is 1.45, and the resonant unit for light with a wavelength of 700nm to 1600nm is 3.47.

[0017] Secondly, the present invention provides a particle trapping method based on an all-dielectric metasurface, comprising:

[0018] The particle trapping device is placed in a liquid environment with the resonant unit facing upwards;

[0019] A beam of light is projected onto the particle trapping device, causing the beam to resonate in the resonant layer.

[0020] Adjusting at least one of the wavelength, polarization state, or incident angle of the light beam causes the light beam to excite destructive interference between electric dipole radiation and ring dipole radiation within the resonant unit, thereby inducing a dispersion flattening transition in the Anapole resonant mode, simultaneously exciting a flat-band quasi-continuous domain bound state, and constructing a three-dimensional optical potential well in the near-field region.

[0021] The target particle is introduced into the three-dimensional optical potential well, and the optical restoring force generated by the three-dimensional optical potential well is used to overcome the Brownian motion of the target particle, thereby achieving optical capture of the target particle.

[0022] In one implementation of the second aspect, the refractive index of the liquid environment is 1.31 to 1.38.

[0023] In one implementation of the second aspect, the operating wavelength of the light beam is 1000nm~1600nm, and the power of the light beam is 50 mW~150 mW.

[0024] In one implementation of the second aspect, the target particle has a particle size of 10nm to 20nm and the target particle is made of polystyrene.

[0025] As described above, the particle trapping device and method based on all-dielectric metasurface of the present invention does not rely on symmetry-broken structures and achieves high Q value and stable particle trapping under different incident angles and processing errors. Attached Figure Description

[0026] Figure 1 The diagram shown is a structural schematic of a particle trapping device based on an all-dielectric metasurface according to an embodiment of the present invention.

[0027] Figure 2 The image shown is a rendering of a cylinder with a low aspect ratio using existing technology.

[0028] Figure 2 (a) in the figure shows the frequency-wave vector dispersion relationship of a cylinder with a low aspect ratio using the prior art.

[0029] Figure 2 (b) shows the quality factor of a cylinder with a low aspect ratio using existing technology as a function of the normalized wave vector.

[0030] Figure 2 (c) in the figure shows a cross-sectional view of the near-field electric field intensity distribution of a cylinder with a low aspect ratio using the prior art.

[0031] Figure 3 The diagram shown is a schematic diagram of the flat band energy band and electric field distribution according to an embodiment of the present invention.

[0032] Figure 3 (a) in the figure shows a schematic diagram of the flat band structure of an embodiment of the present invention.

[0033] Figure 3 (b) in the figure shows a schematic diagram of the electric field distribution according to an embodiment of the present invention.

[0034] Figure 4 The diagram shown is a schematic representation of the Q-factor according to an embodiment of the present invention.

[0035] Figure 5 The diagram shows the changes in Fx and optical potential well under different incident angles and structural perturbations according to an embodiment of the present invention.

[0036] Figure 5 (a) in the figure shows the change in the position of the capture area under different incident angles according to an embodiment of the present invention.

[0037] Figure 5 (b) shows the optical potential well variation under structural perturbation changes in an embodiment of the present invention.

[0038] Figure 6 The diagram shows the changes in Fy and optical potential well under different incident angles and structural perturbations according to an embodiment of the present invention.

[0039] Figure 6 (a) in the figure shows the change in the position of the capture area under different incident angles according to an embodiment of the present invention.

[0040] Figure 6 (b) shows the optical potential well variation under structural perturbation changes in an embodiment of the present invention.

[0041] Figure 7 The diagram shows the changes in Fz and optical potential well under different incident angles and structural perturbations according to an embodiment of the present invention.

[0042] Figure 7 (a) in the figure shows the change in the position of the capture area under different incident angles according to an embodiment of the present invention.

[0043] Figure 7 (b) shows the optical potential well variation under structural perturbation changes in an embodiment of the present invention.

[0044] Component designation explanation

[0045] 1. Dielectric substrate layer; 2. Resonant unit. Detailed Implementation

[0046] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0047] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0048] It should be noted that when a component is said to be "connected" to another component, it can be directly connected to the other component or it can be connected to a component in between. When a component is said to be "set on" another component, it can be directly set on the other component or it may be set to a component in between.

[0049] Ideal continuous bound states (BICs) are essentially dark modes decoupled from free space, possessing an infinite theoretical quality factor, but cannot be directly excited by external plane waves. To make them excitable, current techniques typically involve breaking the in-plane inversion symmetry or rotational symmetry of the structure, causing a weak hybridization between the dark and bright modes, transforming them into quasi-BICs.

[0050] In the early stages of plasma optical tweezers technology, metallic nanoantennas, limited by skin depth and ohmic loss, naturally exhibited low aspect ratios. When researchers shifted to using metasurfaces for optical trapping, considering the shallow etching depth, easily controllable aspect ratio, and high process yield of low aspect ratio resonant units, the technology route of plasma optical tweezers was still followed, and low aspect ratio resonant units were commonly used. For example, in existing all-dielectric metasurface optical trapping devices, the traditional approach of using low aspect ratio resonant units in plasma optical tweezers is still followed. The height h of the silicon dielectric cylinder is designed to be smaller than the base radius r of the cylinder. Symmetry-breaking structures such as etching notches, asymmetric cuts, and elliptic deformation are introduced into the geometry of the resonant unit to transform the ideal standard cylinder into a non-standard cylinder.

[0051] However, this coupling mechanism, which relies on geometrical disruption, is extremely fragile. Once the structure deviates from the designed morphology, the hybridization intensity of the modes changes drastically, leading to a resonant peak shift, a sharp drop in Q value, and consequently, instability of the optical potential well. Furthermore, this structure is sensitive to the incident angle of light; even slight fluctuations in the incident light conditions can disrupt the spatial stability of the trapping potential well.

[0052] To address the sensitivity of optical trapping potential wells to light incident angles and manufacturing errors, please refer to... Figure 1 In one embodiment, the present invention provides a particle trapping device based on an all-dielectric metasurface, including a dielectric substrate layer 1 and a resonant layer located on the surface of the dielectric substrate layer. The resonant layer includes a plurality of resonant units 2 arranged in an array. The dielectric substrate layer 1 is made of quartz material, and the resonant units 2 are made of silicon material. The resonant units 2 are standard cylinders, the height h of which is 2.5 to 3.1 times the base radius r of which is a standard cylinder, and the array period P of the resonant units is 2.7 to 3.3 times the base radius r of which is a standard cylinder. Figure 1 The three-dimensional optical potential well shown by the color bar on the right intuitively presents the funnel-shaped trapping area formed by the potential well above the top surface of the cylinder, with the center being the minimum point of the potential well. The target particle is stably bound in this high-field local region by the gradient force.

[0053] The particle trapping device in this embodiment abandons the design approach of low aspect ratio and symmetry breaking used in existing metasurface-based particle trapping devices. It achieves quasi-BIC and optical trapping by simply using an unconventional high aspect ratio without designing a symmetry-breaking structure. This opens up new ideas for the research of metasurface-based particle trapping technology. This new approach is expected to be extended to the research of all-dielectric metasurfaces in other material systems.

[0054] The principle of this embodiment is as follows: This embodiment abandons the symmetry-breaking design, adopts a standard cylindrical shape, and precisely controls the height h of the standard cylinder to be 2.5 to 3.1 times the base radius r, and the array period P to be 2.7 to 3.3 times r, triggering the longitudinal multipole cooperative resonance mechanism. When the ratio of the height h to the base radius r of the standard cylinder is in the range of 2.5 to 3.1, the axial optical field confinement is significantly enhanced, and the spectra of the internally excited electric dipole (ED) and the ring dipole (TD) overlap. On this basis, further, within the range of the ratio of the array period P to the base radius r of 2.7 to 3.3, the lattice diffraction coupling is precisely controlled, so that the far-field radiation phase difference between the ED and TD is strictly locked within a wide momentum space. Nearby, the two undergo deep destructive interference, and the radiation channel is dynamically closed, thus spontaneously forming a high-Q Anapole resonant mode without destroying geometric symmetry. This fundamentally replaces the technical approach that relies on etched notches to forcibly couple dark modes.

[0055] Figure 2 (a) is the frequency-wave vector dispersion diagram of a standard cylindrical array using the existing low aspect ratio structure, reflecting the variation of the resonant frequency with the normalized wave vector. Figure 2 (b) is a graph showing the quality factor of a standard cylindrical array as a function of the normalized wave vector when using the existing parameter range, which characterizes the mode radiation loss and energy localization characteristics. Figure 2 (c) is a cross-sectional view of the near-field electric field intensity distribution in Anapole A and Anapole B modes when the standard cylindrical array uses the existing parameter range, which is used to intuitively present the local state of the optical field in space. Figure 3 (a) in the figure is a frequency-wave vector dispersion relation diagram of the resonant structure in the embodiment of the present invention, showing the flat-band topological characteristics and mode degeneracy. Figure 3 (b) is a cross-sectional view of the near-field electric field intensity distribution of the resonant structure in Anapole A and Anapole B modes according to the embodiment of the present invention, which is used to characterize the spatial distribution and local intensity of the optical gradient potential well.

[0056] Please refer to Figure 2 In (a) of this embodiment, when the height-to-diameter ratio of the resonant unit is less than 1, the optical field mainly oscillates radially, and the spectra of the two dipoles are significantly separated. Only lattice diffraction produces a weak match at the zero wave vector point. Band 1 is parabolic with a large dispersion rate, while band 2 intersects band 1 only near a specific wave vector point. The two modes degenerate only at a specific incident angle, and rapidly mismatch after deviating from the specific incident angle. Please refer to... Figure 3In (a), when the aspect ratio and period of the resonant unit meet the conditions of this embodiment, the strong axial optical field constraint is activated, making the longitudinal mode dominate the resonance. The control of the period parameter makes the phase difference of the far-field radiation of the two dipoles continuously locked in the anti-phase state in the wide wave vector space, forming a flat band bound state. Band 2 and band 3 almost coincide in the full momentum space, the curve is flat, the dispersion rate approaches zero, the two modes are continuously locked in the wide wave vector range, and the dispersion relationship undergoes topological reconstruction.

[0057] Please refer to Figure 2 In (b) of this embodiment, when the height-to-diameter ratio of the resonant unit is less than 1, the amplitudes of the two dipoles are mismatched, the phase difference deviates from the anti-phase state, the far-field interference cancellation is incomplete, the radiation channel is not effectively closed, radiation loss dominates, and an effective energy localization cannot be formed. The quality factor fluctuates in a low range of 21.5 to 22.5, with an extremely low order of magnitude. Please refer to... Figure 4 When the aspect ratio and period of the resonant unit meet the conditions of this embodiment, forced amplitude matching and phase inversion occur, the radiation channel is dynamically closed, non-radiative losses dominate, and the quality factor is stably maintained at 10. 5 The above achieves an ultra-high quality factor and increases the optical potential well depth by several orders of magnitude.

[0058] Please refer to Figure 2 In (c) of this embodiment, when the height-to-diameter ratio of the resonant unit is less than 1, energy diffuses significantly towards the edge of the cylinder. Please refer to [reference needed]. Figure 3 In (b), when the height-to-diameter ratio and period of the resonant unit meet the conditions of this embodiment, the energy is strictly compressed in the center and top surface region of the cylinder, presenting a circulating cancellation structure, forming a steep funnel-shaped potential well, which significantly enhances the capture stability and anti-disturbance capability.

[0059] This embodiment maintains stable optical capture even when the incident angle of light changes. The principle is as follows: Within this ratio range, the dispersion relation of the Anapole mode in momentum space undergoes a topological transformation: the resonant frequency, which originally changed rapidly with the wave vector, is flattened, forming a nearly dispersion-free flat-band quasi-continuous bound state over a wide wave vector range. The flat-band characteristic means that the excitation and near-field local intensity of this high-Q resonant mode are intrinsically insensitive to the wave vector of the incident light and in-plane periodic perturbations.

[0060] Furthermore, this embodiment employs a standard cylindrical morphology, completely eliminating the need for etching processes that require complex symmetry breaking features, thus ensuring high compatibility between the device structure and standard CMOS micro / nano fabrication processes. Because it does not rely on geometric breaks, the device is naturally immune to structural perturbations such as dimensional deviations and edge roughness during fabrication, significantly reducing mass production difficulty and cost.

[0061] Due to the near-dispersion-free characteristics of the flat-band quasi-BIC in this embodiment over a wide wave vector range, the spatial distribution and depth of the optical potential trap remain stable even when the incident light angle changes significantly. No precise calibration of the incident light path is required, and effective capture can be maintained even under fiber coupling or non-ideal collimated illumination, greatly improving the fault tolerance and engineering applicability of practical optical systems.

[0062] Figure 5 (a) Figure 6 (a) Figure 7 Figure (a) shows the distribution of Fx, Fy, and Fz components acting on the polystyrene particles and the corresponding one-dimensional optical potential wells as the incident angle gradually increases from 0° to 15°. The comparison shows that even with a ±15° shift in the incident angle, the core trapping region of the three-dimensional force field distribution does not drift, and the potential well depth almost coincides with the stiffness curve, verifying the robustness of the flat-band mode within a wide angle window. Figure 5 (b) Figure 6 (b) Figure 7 (b) reflects the effect of structural parameter perturbation on the potential well depth. The surface shows a clear plateau region, indicating that the manufacturing process tolerance will not destroy the capture stability.

[0063] This embodiment significantly reduces parasitic thermal effects and fluid convection under the action of light field by combining the inherent low absorption and low radiation loss characteristics of the Anapole mode with an all-dielectric material system. It avoids thermal damage to temperature-sensitive biological samples caused by traditional plasma optical tweezers or high-power focused optical tweezers, and provides a safe and reliable optical platform for highly active long-term manipulation of biological macromolecules, single cells or subcellular organelles.

[0064] This embodiment abandons the symmetry-breaking design, relying solely on an ultra-high aspect ratio and optimized array period to spontaneously excite high-Q quasi-BICs within a fully symmetrical structure. This embodiment significantly simplifies fabrication requirements, achieves wide incident angles and high-stability optical trapping, and opens a new path for all-dielectric metasurface particle trapping technology.

[0065] In one embodiment, the base radius of the standard cylinder is 260 nm to 320 nm, the height of the standard cylinder is 750 nm to 850 nm, and the array period of the resonant unit is 830 nm to 860 nm. Within this size window, the destructive interference efficiency between the electric dipole and the ring dipole reaches its peak, far-field radiation loss is extremely suppressed, and the quality factor is stably maintained at 10. 5 This size range effectively avoids mode leakage caused by excessively small size or multimode competition caused by excessively large size, ensuring that the bound states in the flat-band quasi-continuous domain form high-intensity and spatially symmetrical electromagnetic field hotspots in the near-field region. This provides sufficient field strength gradient for the subsequent construction of the three-dimensional optical potential trap, improving the compatibility and capture efficiency of the device at different operating wavelengths.

[0066] In one embodiment, the base radius of the standard cylinder is 290 nm, the height of the standard cylinder is 805 nm, and the array period of the resonant unit is 850 nm. At this size, the strong coupling of the resonant modes reaches a critical state, the transformation of the modes to bound states in the flat-band quasi-continuous domain is most complete, the band flatness is highest, and the quality factor can exceed 10. 7 The near-field electric field directly above the resonant unit exhibits a strong central local enhancement feature. The depth and stiffness of the three-dimensional optical potential well reach their maximum values ​​simultaneously, minimizing the sensitivity to the incident light wave vector. Even under non-ideal collimated illumination or fiber coupling conditions, it can still maintain the precise positioning and long-term confinement of nanoscale particles, significantly improving the engineering fault tolerance of practical optical systems.

[0067] In one embodiment, the thickness of the dielectric substrate layer is 1 μm to 3 μm. This thickness range can isolate the parasitic coupling of the underlying support structure to the near-field modes of the silicon resonator layer, while ensuring sufficient mechanical strength to withstand operation in microfluidic or liquid environments. If the thickness of the dielectric substrate layer is too thin, it may cause interference to the near-field distribution by the substrate transmission interference fringes. If the thickness of the dielectric substrate layer is too thick, it may cause fabrication warpage and stress concentration problems. This embodiment provides vertical optical field confinement while ensuring the flatness and optical response consistency of the metasurface array during large-area fabrication.

[0068] In one embodiment, the refractive index of the dielectric substrate for light with wavelengths of 700 nm to 1600 nm is no higher than 1.47, and the refractive index of the resonant unit for light with wavelengths of 700 nm to 1600 nm is no lower than 3.45. The high refractive index difference between quartz and silicon in this wide wavelength range constitutes a strong vertical optical confinement boundary, forcing incident photons to undergo multiple total internal reflections and Fabry-Perot resonants within the silicon cylinder. This embodiment ensures the effective accumulation of resonant modes within the resonant cavity while suppressing energy leakage towards the substrate, concentrating most of the light energy in the cladding region at the top of the cylinder, increasing the steepness of the near-field optical gradient, and thus enhancing the gradient trapping force for target particles.

[0069] In one embodiment, the refractive index of the dielectric substrate layer for light with wavelengths of 700nm to 1600nm is 1.45, and the resonant unit for light with wavelengths of 700nm to 1600nm is 3.47.

[0070] In one embodiment, the present invention also provides a particle trapping method based on an all-dielectric metasurface, comprising:

[0071] Step S100: Place the particle trapping device of the above embodiment in a liquid environment with the resonant unit 2 facing upward;

[0072] Step S200: Project a light beam onto the particle trapping device to excite resonance in the resonant layer.

[0073] Step S300: Adjust at least one of the wavelength, polarization state or incident angle of the beam to excite the destructive interference of electric dipole radiation and ring dipole radiation in the resonant unit, thereby inducing the Anapole resonant mode to undergo a dispersion flattening transition, simultaneously exciting the flat-band quasi-continuous domain bound state, and constructing a three-dimensional optical potential well in the near-field region.

[0074] Step S400: The target particle is introduced into the three-dimensional optical potential well, and the optical restoring force generated by the three-dimensional optical potential well is used to overcome the Brownian motion of the target particle, thereby achieving optical capture of the target particle.

[0075] The optical trapping force acting on the target particle is mainly dominated by the light field gradient force, while the scattering force component is negligible. The optical force calculation is based on Maxwell's stress tensor integral, and its mathematical expression and physical meaning are as follows:

[0076]

[0077] in, The time-averaged Maxwell stress tensor characterizes the momentum flux density distribution of the light field in space.

[0078] Represents the closed integral surface surrounding the target particle. The outward normal vector is used to determine the direction of the force and the integral boundary.

[0079] The specific component expansion of the time-averaged Maxwell stress tensor is as follows:

[0080]

[0081] in,

[0082] Represents electric displacement;

[0083] Represents a magnetic field;

[0084] The conjugate quantity representing the electric field strength;

[0085] The conjugate quantity representing the magnetic field strength;

[0086] Zhang Liang, representing the organization.

[0087] Based on the optical distribution, the optical potential energy of the target particle in a specific direction can be obtained by integrating along the capture path, and its expression is:

[0088]

[0089] in, Represents a unidirectional capturing potential;

[0090] This represents the gradient force component along the integration path direction;

[0091] This represents the capture path.

[0092] The potential well depth can be quantified through this integration. When the potential well depth satisfies the following condition, Brownian motion can be effectively suppressed, achieving stable optical trapping:

[0093]

[0094] in, Boltzmann's constant, The system temperature is denoted as .

[0095] Simulations and experimental verifications of 15 nm diameter polystyrene particles in a liquid environment with an incident power of 100 mW both show that the three-dimensional potential well depth stably exceeds the threshold, confirming the efficiency of the method.

[0096] The capture method in this embodiment can trigger the bound state in the quasi-continuous domain of the flat band by fine-tuning the beam parameters, without the need for complex optical path calibration or precise alignment. It utilizes the phase transition from the resonant mode to the flat band state to achieve automatic locking and enhancement of the potential well, thus solving the technical bottlenecks of traditional optical tweezers systems, such as sensitivity to the incident angle, easy drift of the potential well, and easy overheating at high power.

[0097] In one embodiment, the refractive index of the liquid environment is 1.31 to 1.38. If the refractive index of the liquid environment is too high, it may lead to mode leakage. If the refractive index of the liquid environment is too low, it may cause near-field attenuation. This embodiment ensures the effectiveness of the optical potential trap in biochemical detection scenarios while maintaining the low absorption characteristics of the liquid, minimizing Joule heating and thermophoretic flux generated during the capture process, and ensuring the long-term activity of temperature-sensitive biomolecules or living cells.

[0098] In one embodiment, the operating wavelength of the light beam is 1000 nm to 1600 nm, and the beam power is 50 mW to 150 mW. This embodiment's wavelength band lies in the overlap region between the transparent window of the silicon material and the optical window of biological tissue, which can reduce material absorption and scattering, as well as phototoxicity of biological samples. Within the wavelength and power density range of this embodiment, the destructive interference efficiency of the resonant mode is highest, and the field enhancement factor of the flat-band quasi-continuous domain bound states is sufficient to construct an optical potential well with a depth exceeding the thermal threshold at low power. The power density of this embodiment ensures that the gradient force is sufficient to overcome the thermal motion of nanoparticles without causing thermal damage, achieving an ideal operating range with low thermal load and high trapping stiffness, suitable for high-sensitivity manipulation at the level of living cells, exosomes, or single molecules.

[0099] In one embodiment, the target particles have a particle size of 10 nm to 20 nm and are made of polystyrene.

[0100] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered to be within the scope of this specification. When technical features of different embodiments are embodied in the same drawing, it can be regarded as the drawing also disclosing examples of combinations of the various embodiments involved.

[0101] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

[0102] The protection scope of the particle trapping method based on all-dielectric metasurfaces in this invention is not limited to the execution order of the steps listed in this embodiment. Any solution implemented by adding, subtracting, or replacing steps in the prior art based on the principles of this invention is included within the protection scope of this invention.

Claims

1. A particle trapping device based on an all-dielectric metasurface, comprising a dielectric substrate layer and a resonant layer located on the surface of the dielectric substrate layer, the resonant layer comprising a plurality of resonant units arranged in an array, wherein the dielectric substrate layer is made of quartz material and the resonant units are made of silicon material, characterized in that, The resonant unit is a standard cylinder, the height of which is 2.5 to 3.1 times the radius of its base, and the array period of the resonant unit is 2.7 to 3.3 times the radius of its base.

2. The particle trapping device with an all-dielectric metasurface according to claim 1, characterized in that, The standard cylinder has a base radius of 260nm~320nm, a height of 750nm~850nm, and an array period of 830nm~860nm.

3. The particle trapping device with an all-dielectric metasurface according to claim 2, characterized in that, The standard cylinder has a base radius of 290 nm, a height of 805 nm, and an array period of 850 nm for the resonant unit.

4. The particle trapping device with an all-dielectric metasurface according to claim 1, characterized in that, The thickness of the dielectric substrate layer is 1 μm to 3 μm.

5. The particle trapping device with an all-dielectric metasurface according to claim 1, characterized in that, The refractive index of the dielectric substrate layer for light with wavelengths of 700nm to 1600nm is not higher than 1.47, and the resonant unit for light with wavelengths of 700nm to 1600nm is not lower than 3.

45.

6. A particle trapping method based on an all-dielectric metasurface, characterized in that, include: The particle trapping device according to any one of claims 1 to 5 is placed in a liquid environment with the resonant unit facing upwards; A beam of light is projected onto the particle trapping device, causing the beam to resonate in the resonant layer. Adjusting at least one of the wavelength, polarization state, or incident angle of the light beam causes the light beam to excite destructive interference between electric dipole radiation and ring dipole radiation within the resonant unit, thereby inducing a dispersion flattening transition in the Anapole resonant mode, simultaneously exciting a flat-band quasi-continuous domain bound state, and constructing a three-dimensional optical potential well in the near-field region. The target particle is introduced into the three-dimensional optical potential well, and the optical restoring force generated by the three-dimensional optical potential well is used to overcome the Brownian motion of the target particle, thereby achieving optical capture of the target particle.

7. The particle trapping method based on an all-dielectric metasurface according to claim 6, characterized in that, The refractive index of the liquid environment is 1.31~1.

38.

8. The particle trapping method based on an all-dielectric metasurface according to claim 6, characterized in that, The operating wavelength of the light beam is 1000nm~1600nm, and the power of the light beam is 50 mW~150 mW.

9. The particle trapping method based on an all-dielectric metasurface according to claim 6, characterized in that, The target particles have a particle size of 10nm~20nm and are made of polystyrene.

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