Preparation method of femtosecond laser-induced implant electric signal shielding microstructure

Abstract

The invention relates to the technical field of material surface modification precision machining, and provides a preparation method of a femtosecond laser-induced implant electric signal shielding microstructure, a biological metal substrate material is completely immersed in a transparent liquid, and the transparent liquid is an HEPES buffer solution filled with inert gas. A stable microbubble array is formed through ultrasonic treatment induction, femtosecond laser is focused on an area above a material, and path scanning operation is carried out. And obtaining a dual-scale structure formed by the central microcavity and the nano texture on the surface of the material. According to the method, a femtosecond laser processing technology can be utilized, and a transient nonlinear light-induced breakdown effect of the femtosecond laser processing technology in a liquid phase is combined, so that a local microcavity and nano-grain composite dual-scale structure is induced to be formed, and charge distribution and dielectric properties on the surface of a material are accurately regulated and controlled. The invention further discloses an electric signal shielding microstructure and antibacterial application, and the double-scale structure not only has the function of regulating and controlling behaviors of adult cells, but also can effectively shield or interfere the electric signal conduction process between bacteria.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for material surface modification, and in particular to a method for preparing a microstructure for shielding electrical signals in a femtosecond laser-induced implant. Background Technology

[0002] Implantable medical devices such as artificial joints, bone screws, and cardiovascular stents are widely used in clinical treatment, but their surfaces are prone to bacterial colonization and biofilm formation, leading to persistent infections. Traditional antibacterial strategies, including antibiotic release, metal ion coating, and photothermal sterilization, have some effectiveness but are limited by factors such as increased drug resistance, enhanced local toxicity, and short duration of action.

[0003] CN112891365B discloses the preparation and application of a 3D biomimetic cell implant capable of releasing microRNA nucleic acid drugs. The 3D biomimetic genetically engineered cell implant is a linear drug-producing implant with a porous membrane structure. The outer layer is a membrane wall with nanopores, and the inner layer contains living cells capable of long-term drug release. It achieves efficient and long-term drug release by mimicking the biomimetic principle of nutrient diffusion from blood vessels to tissues. The drug-producing cells are selected from umbilical cord blood-derived MSCs, which are homologously recombined with Rab27A to continuously and efficiently produce exosomes. Simultaneously, the micRNA377 expression plasmid is introduced to produce cell exosomes containing recombinant nucleic acids. The MSCs used are transgenic to introduce the Kex2-EK secretory signal peptide, which allows microRNA nucleic acid drugs to be encapsulated within the exosomes.

[0004] CN110773739B discloses a gradient titanium-magnesium composite implant for inducing bone growth and its forming method. The implant is formed by extruding and filling the pores of a porous titanium alloy implant formed by selective laser melting with a composite material containing sustained-release magnesium alloy and bone-inducing nano-hydroxyapatite. The forming method includes the following steps: (1) forming a porous titanium alloy implant from spherical medical titanium alloy powder using selective laser melting technology; (2) grinding and mixing magnesium alloy powder and nano-hydroxyapatite powder in a high-energy ball mill under high-purity argon protection to obtain a uniformly mixed composite material powder; (3) wrapping the porous titanium alloy implant obtained in step (1) with the composite material powder from step (2), placing it into the ceramic extrusion cylinder of a hydrostatic extruder, and evacuating it to 5×10⁻⁶. －3 ~1×10 －3Pa, heat the extrusion cylinder until the magnesium alloy powder melts and keep it at a constant temperature, and apply a magnetic field to the outer ring of the extrusion cylinder; (4) apply compressive stress cyclically on both sides of the extrusion cylinder; (5) after the compressive stress is applied, stop heating the extrusion cylinder, and when the temperature of the magnesium alloy melt cools to the melting point, take out the porous titanium alloy implant filled with magnesium alloy and cool and solidify it in a high-purity argon environment to finally obtain a gradient titanium-magnesium composite implant; in step (1), the spherical medical titanium alloy powder is one or a mixture of two of medical pure titanium powder and Ti-Nb alloy powder, and the mass fraction of Ti in the Ti-Nb alloy powder is 65-80% and the mass fraction of Nb is 20-35%.

[0005] Current surface modification techniques face significant bottlenecks: they struggle to simultaneously achieve precise control of nanoscale structures and efficient electrical signal interference on material surfaces, and even more so to stably construct multi-scale hierarchical structures that combine both characteristics. These limitations prevent material surfaces from meeting the demands of high-end fields such as precision sensing, intelligent protection, and microelectronic devices, while also restricting the performance of materials in multi-physics coupling scenarios. Summary of the Invention

[0006] Long-term practice has revealed that, in addition to relying on chemical signals, such as quorum sensing molecules, bacteria can also synchronize their metabolism and aggregate through low-intensity, biocompatible electrical signals. This "electrical signal communication" mechanism has become a new target for regulating early biofilm formation. Current surface modification methods are unable to construct multi-scale structures on material surfaces that combine nanoscale structural regulation with electrical signal interference, and also lack structural design methods for actively regulating bacterial electrical behavior.

[0007] By altering the electrical properties of material surfaces to interfere with bacterial electrical signal transmission, thereby blocking their group coordination behavior, a novel approach to "drug-free antibacterial" methods can be provided.

[0008] In view of this, the present invention aims to propose a method for preparing a femtosecond laser-induced implant electrical signal shielding microstructure, comprising: Step S1: The bio-metal substrate material is completely immersed in a transparent liquid, which is a HEPES buffer filled with an inert gas; wherein, the 4-hydroxyethylpiperazine ethanesulfonic acid (HEPES) molecule contains hydroxyethyl, a piperazine ring and an ethanesulfonic acid group.

[0009] Step S2: Use ultrasonic treatment to induce the formation of a stable microbubble array; Step S3: A femtosecond laser is focused on the area above the bio-metal substrate material to perform a path scanning operation; Step S4: Under femtosecond laser induction, energy deposition is controlled by the bubble lens effect to obtain a dual-scale structure on the material surface consisting of a central microcavity and subwavelength nanotextures around the central microcavity.

[0010] Preferably, the femtosecond laser has a wavelength of 1030 nm, a pulse width of 300 fs, and a repetition frequency of ≥500 kHz.

[0011] Preferably, the path scanning operation includes parallel, grid, and spiral paths.

[0012] Preferably, the bio-metal substrate material includes titanium alloy, titanium or aluminum alloy, or stainless steel.

[0013] Preferably, the bio-metal substrate material is completely immersed in a transparent liquid, with the surface of the transparent liquid 0.5-2 mm away from the upper surface of the bio-metal substrate material.

[0014] Preferably, the central microcavity is 1μm-2μm, and the period of the nanostripes is 100nm-200nm, with a depth of 30nm-70nm.

[0015] Preferably, the femtosecond laser is focused on a 0.5μm-1μm area above the surface of the bio-metal substrate material to perform a grid scan.

[0016] The present invention also discloses an electrical signal shielding microstructure prepared by the above-described method for preparing an implantable electrical signal shielding microstructure, wherein the electrical signal shielding microstructure includes a bio-metal substrate having a central microcavity on its surface and a subwavelength nanotexture surrounding the central microcavity forming a dual-scale structure.

[0017] The present invention also discloses an antibacterial application of the electrical signal shielding microstructure as described above, wherein the antibacterial application of the electrical signal shielding microstructure is capable of shielding the transmission of electrical signals between microorganisms.

[0018] This invention provides an electronic device, comprising at least one processor; and A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, which, when executed by the at least one processor, enables the at least one processor to perform the above-described method.

[0019] The present invention provides a machine-readable storage medium storing instructions that cause a machine to perform the method described above.

[0020] This invention discloses a method for preparing a femtosecond laser-induced implantable electrical signal shielding microstructure. First, a bio-metal substrate material is completely immersed in a transparent liquid, which is a HEPES buffer solution filled with an inert gas. Then, a stable microbubble array is induced using ultrasonic treatment. A femtosecond laser is focused on the area above the bio-metal substrate material for path scanning. Under femtosecond laser induction, energy deposition is controlled through the bubble lens effect, resulting in a dual-scale structure on the material surface consisting of a central microcavity and subwavelength nanotextures surrounding the central microcavity. This method utilizes femtosecond laser processing technology, combined with its transient nonlinear photo-induced breakdown effect in the liquid phase, to induce the formation of a local microcavity and nanotexture composite dual-scale structure, achieving precise control over the charge distribution and dielectric properties of the material surface. This invention also discloses an electrical signal shielding microstructure and its antibacterial application. This dual-scale structure not only has the function of regulating adult cell behavior but also effectively shields or interferes with the electrical signal transmission process between bacteria, reducing the probability of biofilm formation at the source. By addressing the issue at the microscopic electrical signal level, this invention opens up a novel type of non-invasive antibacterial mechanism with high cutting-edge and differentiated technological advantages.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of a method for preparing a femtosecond laser-induced implant electrical signal shielding microstructure according to one embodiment of the present invention; Figure 2 This is a scanning electron microscope image of the dual-scale microstructure morphology according to one embodiment of the present invention; Figure 3 This is a fluorescent staining image showing the results of a comparative experiment on biofilm formation of bacteria on modified and unmodified surfaces, according to one embodiment of the present invention. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] To address the technical problems existing in current technologies, surface modification methods are currently unable to construct multi-scale structures on material surfaces that combine nanoscale structural regulation and electrical signal interference functions, and also lack structural design methods for actively regulating bacterial electrical behavior. This invention provides a method for preparing femtosecond laser-induced implantable electrical signal shielding microstructures, such as... Figure 1-3 As shown, the method for fabricating a femtosecond laser-induced implant electrical signal shielding microstructure includes, Step S1: Immerse the bio-metal substrate material completely in a transparent liquid, which is a HEPES buffer solution filled with inert gas.

[0027] Step S2: Use ultrasonic treatment to induce the formation of a stable microbubble array; Step S3: A femtosecond laser is focused on the area above the bio-metal substrate material to perform a path scanning operation; Step S4: Under femtosecond laser induction, energy deposition is controlled by the bubble lens effect to obtain a dual-scale structure on the material surface consisting of a central microcavity and subwavelength nanotextures around the central microcavity.

[0028] This invention discloses a method for fabricating a femtosecond laser-induced electrical signal shielding microstructure for implants. First, a bio-metal substrate material is completely immersed in a transparent liquid, specifically a HEPES buffer solution filled with an inert gas. Then, a stable microbubble array is induced using ultrasonic treatment. A femtosecond laser is focused on the region above the bio-metal substrate material for path scanning. Under femtosecond laser induction, energy deposition is controlled through the bubble lens effect, resulting in a dual-scale structure on the material surface consisting of a central microcavity and subwavelength nanotextures surrounding the central microcavity. This method utilizes femtosecond laser processing technology, combined with its transient nonlinear photo-induced breakdown effect in the liquid phase, to induce the formation of a localized microcavity and nanotexture composite dual-scale structure, achieving precise control over the surface charge distribution and dielectric properties of the material.

[0029] Dual-scale micro / nano structures were constructed on the surface of bio-metal substrates using femtosecond lasers combined with the bubble lens effect, such as... Figure 2 As shown. To achieve high-precision energy deposition, avoid thermal damage to materials, and ensure the integrity and consistency of micro / nano structures, in a more preferred embodiment of the present invention, the femtosecond laser has a wavelength of 1030 nm, a pulse width of 300 fs, and a repetition frequency greater than or equal to 500 kHz. The transparent liquid is a HEPES buffer solution filled with an inert gas. The HEPES buffer solution can maintain the pH stability of the system, with a typical physiological pH range of 6.8-8.2, avoiding chemical damage to biomaterials such as magnesium alloys and titanium alloys caused by acid-base fluctuations. The inert gas can isolate oxygen, reduce the oxidation reaction on the material surface during laser treatment, and inhibit the oxidation and rupture of the bubble array, ensuring the stability of the microbubble lens effect. Inert gases include nitrogen, helium, argon, etc. The stable microbubble array induced by ultrasonic treatment acts as a dynamic lens, controlling the laser energy focus through the bubble interface to achieve local enhancement or control of energy deposition, thereby improving the resolution and processing efficiency of micro / nano structures.

[0030] To more effectively control the distribution, density, and functional adaptability of the dual-scale structure on the surface of bio-metal substrates, in a more preferred embodiment of this invention, the path scanning operation includes parallel, grid, and helical scanning. When the laser scans parallel along a single direction, the central microcavity and surrounding nanotextures form oriented strips or linear arrays along the scanning direction. This ordered structure can guide cell migration in specific directions, for example, the extension of nerve cell axons and the directional growth of osteoblasts. Parallel paths offer high consistency, ensuring structural uniformity and are suitable for scenarios requiring large-area, low-complexity ordered patterns. Grid scanning forms a regular grid-like dual-scale structure, with the central microcavity distributed in a lattice, and the surrounding nanotextures interconnected to form a network framework. This structure enhances the wear resistance and fatigue resistance of the material surface, while the grid gaps serve as reservoirs or cell anchoring zones. During helical scanning, laser energy concentrates in the central region and gradually thins out at the edges, forming a gradient structure of high-density central microcavities and gradually changing nanotextures at the edges.

[0031] To achieve excellent biomechanical properties, chemical stability, and biocompatibility simultaneously, in a more preferred embodiment of this invention, the bio-metal substrate material comprises titanium alloy, titanium or aluminum alloy, or stainless steel. More preferably, Ti6Al4V is selected as the titanium alloy. The alloy composition of Ti6Al4V includes 6 wt.% Al and 4 wt.% V, optimizing its toughness and machinability, and complementing the ultrashort pulse characteristics of femtosecond lasers. Titanium alloys possess high strength and mechanical properties with an elastic modulus close to that of human bone. They exhibit chemical stability against body fluid corrosion and are non-toxic and biocompatible without immune rejection. Their surface oxide layer (TiO2) is chemically inert, making it less prone to chemical reactions in HEPES buffer filled with inert gas, stably withstanding the high-energy pulses of femtosecond lasers, and avoiding structural defects caused by chemical and thermal damage to the material during processing. For stainless steel, 316L stainless steel containing Mo is preferred to enhance its resistance to body fluid corrosion. If pure titanium is used, its high purity and superior biocompatibility make it suitable for applications sensitive to the release of metal ions. Its surface dual-scale structure can enhance its binding force with soft tissue and reduce inflammatory response.

[0032] To precisely match the ultrasonic-induced bubble array, femtosecond laser focusing, and bubble lensing effect, ensuring the stability, accuracy, and efficiency of the dual-scale structure fabrication, in a more preferred embodiment of this invention, the bio-metal substrate material is completely immersed in a transparent liquid, with the liquid surface 0.5-2 mm below the upper surface of the bio-metal substrate material. The femtosecond laser needs to penetrate the liquid layer and focus on the region above the material. A liquid layer thickness of 0.5-2 mm minimizes laser scattering and energy attenuation in the liquid, ensuring the accuracy and energy density of the focused spot. Although the HEPES buffer solution is transparent, a thick liquid layer still leads to energy loss. A liquid layer thickness of 0.5-2 mm allows for efficient transfer of ultrasonic energy to the material surface, inducing the formation of a uniformly dense and dimensionally stable microbubble array. A liquid layer that is too thin will cause the bubbles to easily break, while a liquid layer that is too thick will cause ultrasonic energy attenuation and a scattered bubble distribution.

[0033] To precisely match the interaction patterns of biological interfaces with the characteristics of laser processing, and to enhance the biofunctional adaptability and structural stability of the dual-scale structure, in a more preferred embodiment of the present invention, the central microcavity is 1μm-2μm, and the period of the nanostripes is 100nm-200nm, with a depth of 30nm-70nm.

[0034] To more accurately match the interaction between the bubble lensing effect and the material surface, achieving high-precision and high-uniformity construction of dual-scale structures while enhancing biocompatibility, a more preferred embodiment of this invention utilizes a femtosecond laser focused on a 0.5μm-1μm region above the surface of the bio-metal substrate material for grid-like scanning. This 0.5μm-1μm region precisely matches the spatial position of the microbubble array that has adhered to the material surface via ultrasound induction. The microbubbles act as dynamic lenses, and the bubble-liquid interface further converges and precisely transfers the laser energy focused in this region to the material surface.

[0035] An antibacterial modification experiment was conducted on the surface of a titanium alloy implant. Ti6Al4V titanium alloy sheets were mechanically polished and ultrasonically cleaned, then completely immersed in HEPES buffer solution supersaturated with N2 gas. Microbubbles were induced by ultrasound, followed by grid scanning of a 0.5 μm area slightly above the surface using a femtosecond laser at 1030 nm, 300 fs, and 500 kHz. The treated surface developed regular 1.5 μm diameter microcavities surrounded by nanostripes spaced 140 nm apart. In vitro bacterial culture tests showed that the biofilm formation rate of Staphylococcus aureus on the surface decreased by approximately 82%.

[0036] An experiment was conducted to investigate the anti-interference functionalization modification of aluminum alloy neural electrodes. Using 1060 aluminum alloy as the substrate, the electrodes were processed with the same liquid phase and femtosecond laser parameters. The laser focus was set 1 μm above the material surface, and a helical scanning path was employed. The resulting dual-scale structure effectively improved the surface resistivity and dielectric constant gradient distribution, exhibiting significant shielding capabilities against external electric fields in micro-electrophysiological signal testing, and inhibiting the electro-inducible migration of *E. coli*.

[0037] The microstructure construction and cell behavior testing of stainless steel dental implant surfaces were conducted using 316L stainless steel implants. A periodic dual-scale structure was created by femtosecond laser treatment, and osteoblast (MC3T3-E1) adhesion behavior was tested under culture conditions. Results showed that the modified structure significantly promoted the directional arrangement of cells within the microcavities and increased their alkaline phosphatase expression level by 47% compared to untreated samples. Bacterial fluorescence staining experiments showed that, as... Figure 3 As shown, the surface antibacterial ability is enhanced, and the electrical signal propagation index decreases by more than 70%.

[0038] The present invention also discloses an electrical signal shielding microstructure prepared by the above-described method for preparing an implantable electrical signal shielding microstructure, wherein the electrical signal shielding microstructure includes a bio-metal substrate having a central microcavity on its surface and a subwavelength nanotexture surrounding the central microcavity forming a dual-scale structure.

[0039] The present invention also discloses an antibacterial application of the electrical signal shielding microstructure as described above, wherein the antibacterial application of the electrical signal shielding microstructure is capable of shielding the transmission of electrical signals between microorganisms.

[0040] The electrical signal shielding microstructure provided by this invention not only has the function of regulating adult cell behavior, but also effectively shields or interferes with the electrical signal transmission process between bacteria, reducing the probability of biofilm formation at the source. By addressing the issue at the microscopic electrical signal level, it pioneers a novel type of non-invasive antibacterial mechanism, possessing significant cutting-edge and differentiated technological advantages.

[0041] This invention provides an electronic device, comprising at least one processor; and A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, which, when executed by the at least one processor, enables the at least one processor to perform the method described above.

[0042] This invention provides a machine-readable storage medium storing instructions for causing a machine to execute the methods described above. It should be noted that, for the foregoing method embodiments, for the sake of simplicity, they are all described as a series of actions. However, those skilled in the art should understand that this invention is not limited to the described order of actions, because according to this invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this invention.

[0043] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0044] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a femtosecond laser-induced electrical signal shielding microstructure for implantation, characterized in that, The method for preparing the femtosecond laser-induced implant electrical signal shielding microstructure includes: Step S1: Completely immerse the bio-metal substrate material in a transparent liquid, wherein the transparent liquid is a HEPES buffer solution filled with inert gas. Step S2: Use ultrasonic treatment to induce the formation of a stable microbubble array; Step S3: A femtosecond laser is focused on the area above the bio-metal substrate material to perform a path scanning operation; Step S4: Under femtosecond laser induction, energy deposition is controlled by the bubble lens effect to obtain a dual-scale structure on the material surface consisting of a central microcavity and subwavelength nanotextures around the central microcavity.

2. The method for preparing the femtosecond laser-induced implant electrical signal shielding microstructure according to claim 1, characterized in that, The femtosecond laser has a wavelength of 1030nm, a pulse width of 300fs, and a repetition frequency of ≥500kHz.

3. The method for preparing the femtosecond laser-induced implant electrical signal shielding microstructure according to claim 2, characterized in that, Path scanning operations include parallel, grid, and spiral.

4. The method for preparing the femtosecond laser-induced implant electrical signal shielding microstructure according to claim 1, characterized in that, The bio-metal substrate material includes titanium alloy, titanium or aluminum alloy, or stainless steel.

5. The method for preparing the femtosecond laser-induced implant electrical signal shielding microstructure according to claim 1, characterized in that, The bio-metal substrate material is completely immersed in a transparent liquid, with the surface of the transparent liquid 0.5-2 mm away from the upper surface of the bio-metal substrate material.

6. The method for preparing the femtosecond laser-induced implant electrical signal shielding microstructure according to claim 1, characterized in that, The central microcavity is 1μm-2μm in size, and the period of the nanostripes is 100nm-200nm, with a depth of 30nm-70nm.

7. The method for preparing the femtosecond laser-induced implant electrical signal shielding microstructure according to any one of claims 1-6, characterized in that, The femtosecond laser was used to perform a grid-like scan on a region 0.5μm-1μm above the surface of the bio-metal substrate material.

8. An electrical signal shielding microstructure prepared using the method for preparing a femtosecond laser-induced implant electrical signal shielding microstructure as described in any one of claims 1-7, characterized in that, The electrical signal shielding microstructure includes a bio-metal substrate with a central microcavity on its surface and subwavelength nanotextures surrounding the central microcavity, forming a dual-scale structure.

9. An antibacterial application of the electrical signal shielding microstructure as described in claim 8, characterized in that, The antibacterial application of the electrical signal shielding microstructure can shield the transmission of electrical signals between microorganisms.

10. A machine-readable storage medium, characterized in that, The machine-readable storage medium stores instructions for causing the machine to perform the method for fabricating a femtosecond laser-induced implant electrical signal shielding microstructure as described in any one of claims 1-7.

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