Body surface photothermal treatment and nanomaterial recovery system and method of operation thereof

Abstract

This invention discloses a system for photothermal treatment of body surfaces and recovery of nanomaterials, and its operating method, belonging to the technical field of photothermal treatment of body surfaces and recovery of nanomaterials. The system includes an infrared light source module, an electrical signal acquisition module, a control module, and a recovery module. Its core is the processing of an ion-responsive self-dissolving hydrogel composed of zinc ions forming dynamic coordination bonds with carboxyl groups in carboxymethyl cellulose and sodium alginate. This hydrogel remains stable in the saline environment of the body surface, but in a low-ion aqueous medium, it undergoes self-dissolution due to the reduction of coordination bonds caused by the outward diffusion of zinc ions. The system precisely regulates the photothermal temperature by acquiring the hydrogel's own resistance, based on a preset resistance-temperature mapping relationship and closed-loop feedback control. After processing, single-walled carbon nanotubes are recovered gently and efficiently under pure aqueous conditions using the hydrogel's self-dissolution properties. It also integrates ultraviolet and infrared sterilization, achieving green, non-destructive, and safe recycling of high-value nanofillers, significantly reducing the cost of medical consumables.

Description

Technical Field

[0001] This invention belongs to the fields of body surface photothermal treatment equipment, intelligent responsive material application and nanomaterial recycling technology. Specifically, it relates to a systematic method and system for realizing body surface photothermal treatment, temperature safety feedback and green recycling of high-value nanofillers using specific ion-responsive hydrogels. Background Technology

[0002] Conductive photothermal gels can generate photothermal effects under near-infrared light irradiation and can output temperature-related signals through changes in their resistance, impedance, or conductivity. Therefore, this type of material can be used as a photothermal treatment material for the body surface and a flexible temperature feedback material.

[0003] In existing technologies, photothermal gels applied to the body surface have the following prominent problems: First, there is the contradiction between the stability and removability of topical therapeutic materials. Ideally, these materials should maintain structural integrity during treatment (typically 5-10 minutes) to ensure accurate photothermal agent positioning and good sensor contact, but should be quickly and gently removed after treatment to avoid cumbersome physical scraping or secondary skin damage. Existing chemically cross-linked hydrogels (such as polyacrylamide) are structurally stable but difficult to remove after treatment; while physically cross-linked hydrogels, although biodegradable, may lack stability in the physiologically moist environment of the skin (such as sweat and exudate), disintegrating before treatment is complete, leading to photothermal agent diffusion and loss of therapeutic effect. Currently, few topical materials achieve both stability during treatment and immediate triggering of disintegration and removal after use.

[0004] Secondly, there is the challenge of recycling expensive nanofillers. Single-walled carbon nanotubes (SWCNTs) are widely used in the manufacture of high-performance photothermal therapy hydrogels due to their excellent photothermal conversion efficiency and conductivity. However, the preparation cost of SWCNTs is high, and directly discarding the entire hydrogel as medical waste after surface treatment would result in a serious waste of resources. Existing waste disposal methods, such as incineration or strong acid digestion, are energy-intensive, polluting, and severely damage the surface structure and photoelectric properties of SWCNTs, rendering them unusable. Enzymatic hydrolysis, while gentler, is costly and time-consuming, making it unsuitable for large-scale processing.

[0005] Third, there is the issue of overheating safety. Photothermal therapy has a narrow temperature window, making precise temperature control crucial. Existing photothermal therapy systems mostly rely on external infrared thermal imagers for temperature measurement, which are easily affected by the angle of illumination, environmental reflection, and skin surface condition, resulting in slow response and limited accuracy.

[0006] Fourth, the integration of functions is insufficient. Existing technologies treat photothermal therapy, temperature monitoring, and post-use material processing as isolated links, lacking a systematic solution that organically integrates "precise temperature safety feedback," "ion response-triggered disintegration," and "green recycling of nanofillers."

[0007] Therefore, there is an urgent need to provide an engineered system that enables the surface photothermal hydrogel to complete photothermal treatment, resistance signal feedback temperature control, post-use trigger self-dissolution, and efficient recycling of single-walled carbon nanotubes under the same system logic, thereby achieving safe and controllable treatment process and recycling of high-value materials. Summary of the Invention

[0008] The purpose of this invention is to provide a system for photothermal treatment of body surfaces and recovery of nanomaterials based on ion-responsive hydrogels, and its operating method. The core innovation of this invention lies in constructing the system using an ion-responsive, self-dissolving single-walled carbon nanotube composite hydrogel product, based on its unique environmentally responsive biphasic characteristics. Therefore, before describing the system of this invention, a detailed description of the functional hydrogel product itself is necessary.

[0009] In this invention, the conductive photothermal hydrogel is the functional object that forms the basis of the system's operation. The conductive photothermal hydrogel is an ion-responsive, self-dissolving single-walled carbon nanotube composite hydrogel, comprising carboxymethyl cellulose, sodium alginate, single-walled carbon nanotubes, and zinc ions. The zinc ions form dynamic coordination bonds with the carboxyl groups in the carboxymethyl cellulose and sodium alginate, constituting a three-dimensional hydrogel network. The single-walled carbon nanotubes are dispersed within this three-dimensional hydrogel network. The conductive photothermal hydrogel maintains its macroscopic gel structure in physiologically saline or relatively dry environments, and undergoes self-dissolution in low-ion aqueous media with a lower total ion content compared to the physiologically saline environment.

[0010] (I) Definitions and Explanations of Terms To more clearly illustrate the characteristics of this hydrogel product, the relevant terms are defined below: In this invention, the aqueous medium refers to a liquid medium with water as the continuous phase, including liquid systems containing inorganic salts, buffer salts, soluble polymers, proteins, or other water-soluble components. In this invention, the physiological saline environment refers to an environment containing physiologically relevant electrolytes, with an ionic composition and osmotic environment similar to that of animal tissue fluid, extracellular fluid, or the physiological environment of the body surface. Preferably, the physiological saline environment includes a physiological saline environment, a phosphate buffer environment, a simulated body fluid environment, a tissue fluid simulated fluid environment, a plasma simulated fluid environment, a cell culture medium environment, or a moist saline environment of the body surface. In some embodiments, the physiological saline environment includes an isotonic saline medium containing animal tissue fluid. The isotonic saline medium containing animal tissue fluid refers to a saline medium containing physiologically relevant electrolytes and with an osmotic environment similar to that of animal tissue fluid. Preferably, the osmolar concentration of the isotonic saline medium containing animal tissue fluid is between 280 mOsm / L and 320 mOsm / L. Preferably, when expressed as an equivalent sodium chloride concentration, the equivalent sodium chloride concentration of the isotonic saline medium of the animal tissue fluid is 0.13 mol / L to 0.17 mol / L.

[0011] In this invention, the low-ion aqueous medium refers to an aqueous medium with a lower total ion content relative to the physiological saline environment, capable of forming a concentration gradient with the hydrogel that promotes the diffusion of zinc ions contained in the hydrogel to the external aqueous medium. Preferably, the low-ion aqueous medium is deionized water, purified water, water for injection, or a low-salt flushing solution. The low-salt flushing solution can be an aqueous flushing medium that has been verified to form a concentration gradient that promotes the outward diffusion of zinc ions and triggers the self-dissolution of the hydrogel.

[0012] In this invention, the relatively dry environment refers to an environment where the hydrogel is exposed to air, adhered to a body surface, covered by a dressing, or similarly operated, and where a continuous external aqueous phase capable of continuously removing zinc ions contained in the hydrogel has not formed. In this relatively dry environment, the hydrogel can maintain a workable macroscopic gel structure. In this invention, self-dissolution refers to the disappearance of the macroscopic gel structure of the hydrogel, forming a mixture containing single-walled carbon nanotubes. Preferably, complete self-dissolution means that after treatment in a low-ion aqueous medium, the mass residue of the hydrogel is less than 1%, and there are no visible gel clumps remaining. Preferably, when the hydrogel is prepared into a cylindrical sample with a diameter of 10 mm and a height of 5 mm, the mass residue rate is the ratio of the recyclable macroscopic gel residue mass after removal and surface liquid aspiration to the initial mass of the cylindrical sample.

[0013] (II) Mechanism of ion-responsive self-dissolution Without being limited by specific theories, the ion-responsive self-dissolution behavior of the hydrogel of this invention is mainly related to the difference in ionic environments inside and outside the hydrogel and the migration of zinc ions. During the preparation process, the hydrogel adsorbs or binds zinc ions, which can dynamically coordinate with the carboxyl groups in carboxymethyl cellulose and sodium alginate, thereby crosslinking the polysaccharide chains into a three-dimensional hydrogel network. When the hydrogel is in a physiological saline environment, the external environment has an ionic composition and osmotic environment similar to animal tissue fluid or extracellular fluid, allowing the hydrogel to maintain a high effective crosslinking density and preserve its macroscopic gel structure. When the hydrogel forms continuous contact with a low-ion aqueous medium with a lower total ion content compared to the physiological saline environment, a concentration gradient is formed between the migratable zinc ions contained in the hydrogel and the external aqueous medium, causing zinc ions to diffuse from the hydrogel to the external aqueous medium. As zinc ions migrate out, the dynamic coordination bonds formed between zinc ions and carboxyl groups decrease, the crosslinking density of the hydrogel decreases, and the macroscopic gel structure disappears. This process does not rely on degradation by biological enzymes, strong acids, or strong bases.

[0014] When a hydrogel is in a relatively dry environment where it does not have continuous contact with an external aqueous medium, the lack of a continuous external aqueous phase that carries away the zinc ions contained in the hydrogel makes it difficult for the zinc ions in the hydrogel to continuously migrate to the external environment. Therefore, the hydrogel can maintain a workable macroscopic gel structure.

[0015] (III) Regarding the composition and proportioning scheme Preferably, the mass ratio of carboxymethyl cellulose to sodium alginate is 1:4 to 1:1, and the total mass concentration of carboxymethyl cellulose and sodium alginate in the precursor solution for preparing the hydrogel is 5.0 wt%. Preferably, the mass of the single-walled carbon nanotubes is 0.1% to 5.0% of the total mass of the carboxymethyl cellulose and sodium alginate. The hydrogel exhibits a temperature rise under near-infrared light irradiation and displays a negative temperature coefficient resistivity response.

[0016] Based on the aforementioned hydrogel products, to achieve the above objectives, this invention provides a body surface photothermal treatment and nanomaterial recovery system, comprising: An infrared light source module is used to irradiate infrared light onto a conductive photothermal gel disposed on the body surface, so that the conductive photothermal gel produces a photothermal effect. An electrical signal acquisition module is used to acquire the resistance signal of the conductive photothermal hydrogel; The control module is connected to the infrared light source module and the electrical signal acquisition module respectively. It is used to determine the temperature state based on the resistance signal and a preset mapping relationship, and to adjust the output of the infrared light source through closed-loop feedback control to maintain the target temperature. The recovery module is used to perform the self-dissolution, separation, and sterilization process of the conductive photothermal gel removed from the body surface after the photothermal treatment is completed, so as to recover the single-walled carbon nanotubes.

[0017] The infrared light source module of this system can use a near-infrared laser with typical parameters of wavelength 808nm, power adjustable from 0.1W to 1W, operating voltage 12V, and effective irradiation distance within 15cm.

[0018] The core hardware of the control module is a microcontroller development board, which is connected to the resistance acquisition circuit and the laser driver circuit. The module internally stores a resistance-temperature mapping curve or lookup table derived through experimental calibration. During operation, the module acquires the hydrogel resistance in real time, calculates the current temperature through the mapping relationship, compares it with the target temperature, and then dynamically adjusts the laser power using closed-loop feedback control algorithms such as PID control. When the real-time temperature is higher than the set value, the power is reduced; conversely, the power is increased. Preferably, the total duration of a single treatment session is fixed at 5-10 minutes.

[0019] The recovery module integrates multiple processing units. It first includes an ultraviolet irradiation unit for surface sterilization of the gel removed from the skin. Then, the gel completely self-dissolves in a processing container containing a low-ion aqueous medium, and the resulting carbon nanotube-containing mixture is sent to a high-speed centrifuge. Because carbon nanotubes are insoluble, they rapidly precipitate at 12000 rad / min, while other dissolved components remain in the supernatant. The separated precipitate is washed and dried, then irradiated in air by a separate infrared heating unit to raise its temperature to above 200°C, achieving thorough sterilization. Since carbon nanotubes can withstand temperatures below 400°C in air, this sterilization method is safe, efficient, and does not damage their structure.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: First, this invention integrates photothermal treatment, resistance change rate temperature feedback, and low-ion aqueous medium self-dissolution and recycling into a single system, enabling conductive photothermal hydrogels to directly enter a mild recycling process after photothermal treatment.

[0021] Secondly, this invention constructs a hydrogel network through the dynamic coordination between carboxymethyl cellulose, sodium alginate and zinc ions, so that the hydrogel maintains a macroscopic gel structure in a physiological saline environment and undergoes self-dissolution in a low-ion aqueous medium with a lower total ion content than the physiological saline environment, thereby taking into account both stability during use and triggering disintegration after use.

[0022] Third, the present invention utilizes the resistance-temperature response characteristics of the conductive photothermal hydrogel itself for feedback control, eliminating the need for an additional independent rigid temperature sensor inside the gel.

[0023] Fourth, the present invention uses the rate of change of resistance signal or normalized rate of change as the basis for judging temperature status. Compared with simply using the absolute resistance value, it is more suitable for application scenarios where there are differences in electrode contact position, initial resistance value or gel morphology.

[0024] Fifth, this invention utilizes a low-ion aqueous medium to trigger the self-dissolution of the hydrogel, and recovers the single-walled carbon nanotubes through centrifugation, washing, and drying, avoiding damage to the structure and photothermal properties of the single-walled carbon nanotubes caused by strong acids, strong alkalis, high-temperature calcination, or severe oxidation treatment.

[0025] Sixth, the low-ion aqueous medium self-dissolution and recycling module of the present invention integrates hydrogel self-dissolution and single-walled carbon nanotube recycling into a continuous processing flow, avoiding separating hydrogel decomposition and nanomaterial recycling into isolated steps.

[0026] Seventh, this invention utilizes single-walled carbon nanotubes to simultaneously construct near-infrared photothermal conversion pathways and resistance-temperature response pathways, enabling the hydrogel to output temperature-related resistance response signals during photothermal processes, which is beneficial for achieving in-situ temperature feedback during photothermal processes.

[0027] Eighth, the single-walled carbon nanotubes recovered by this invention can be further used to remanufacture conductive photothermal hydrogels, which helps reduce the resource waste of high-value nanofillers. After multiple cycles of "preparation-self-dissolution-recovery-remanufacturing", the recovered single-walled carbon nanotubes can still maintain photothermal conversion performance and Raman structural characteristics. In the tested examples, the photothermal conversion efficiency of the third-generation recovered single-walled carbon nanotubes decreased by 1.6 percentage points compared with the first generation, the photothermal conversion efficiency retention rate was about 96.3%, and the change in ID / IG of the third generation was +2.1%. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0029] Figure 1 This is a schematic block diagram of the surface photothermal treatment and nanomaterial recycling system of the present invention.

[0030] Figure 2 The graph shows the photothermal heating curve of the hydrogel in Example 5.

[0031] Figure 3 The graph shows the change in the mass residue of the hydrogel in PBS and deionized water in Example 5.

[0032] Figure 4 The graph shows the resistance response parameters of the hydrogel in Example 2 as a temperature-response curve.

[0033] Figure 5A morphological comparison of original SWCNTs and third-generation recycled SWCNTs.

[0034] Figure 6 A comparison of the Raman spectra of original SWCNTs and third-generation recovered SWCNTs.

[0035] Figure 7 This is a picture of the hydrogel sample prepared in Example 2.

[0036] Figure 8 This is a diagram showing the self-dissolution process of the hydrogel sample prepared in Example 2 in deionized water.

[0037] Figure 9 The recycling process is shown in Example 7. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] Experimental materials and instruments Sodium carboxymethyl cellulose (CMC, viscosity 300 mPa·s to 800 mPa·s), sodium alginate (SA, viscosity 200 mPa·s to 500 mPa·s), single-walled carbon nanotubes (SWCNTs, purity greater than 95%, diameter 1 nm to 2 nm), zinc chloride (ZnCl2), lithium chloride (LiCl), and other reagents were all of analytical grade.

[0040] Example 1: System Overall Structure like Figure 1 As shown, this embodiment provides a system for surface photothermal treatment and nanomaterial recovery. The system includes an infrared light source module, an electrical signal acquisition module, a control module, and a recovery module.

[0041] The infrared light source module uses an 808nm near-infrared laser with adjustable power between 0.1W and 1W, operating at 12V. The illumination distance is set within 15cm to ensure effective light power density. The electrical signal acquisition module is connected to the conductive photothermal gel via electrodes and incorporates a constant current voltage measurement circuit and an analog-to-digital converter for real-time acquisition of resistance signals.

[0042] The core of the control module is a microcontroller development board. The board receives digitized resistance signals and calculates the real-time temperature of the hydrogel based on a pre-established and internally defined "resistance-temperature mapping relationship." This mapping relationship is established by placing the prepared hydrogel in a temperature-controlled environment, measuring and recording its steady-state resistance values ​​at a series of temperature points within the range of 25℃ to 50℃, thus forming a calibration curve. During operation, the control module compares the calculated real-time temperature with the set target treatment temperature (e.g., 43℃) and runs a PID closed-loop feedback control algorithm to dynamically adjust the duty cycle of the PWM wave output to the laser, thereby controlling its output power. During treatment, the system only dynamically adjusts the power, without changing the preset fixed total treatment duration of 5-10 minutes.

[0043] The recycling module integrates an ultraviolet light source, a processing container, a low-ion medium supply unit, a high-speed centrifuge (maximum speed 12000 rad / min), drying equipment, and an infrared heating unit. It is used for ultraviolet sterilization, triggered autolysis, centrifugal separation, drying, and complete infrared sterilization of the used hydrogel.

[0044] Example 2: Preparation of conductive photothermal hydrogel This embodiment illustrates the preparation method of the functional gel processed by the system. The conductive photothermal hydrogel on which this invention is based is an ion strength-responsive self-dissolving single-walled carbon nanotube composite hydrogel. This hydrogel comprises carboxymethyl cellulose, sodium alginate, single-walled carbon nanotubes, and zinc ions.

[0045] Carboxymethyl cellulose and sodium alginate serve as anionic polysaccharide matrices. Zinc ions form dynamic coordination bonds with the carboxyl groups in carboxymethyl cellulose and sodium alginate, constituting a three-dimensional hydrogel network. Single-walled carbon nanotubes are dispersed within this three-dimensional hydrogel network, simultaneously providing near-infrared photothermal conversion pathways and resistivity-temperature response pathways.

[0046] The preparation method includes the following steps: S1, dissolving carboxymethyl cellulose and sodium alginate in water to obtain a polysaccharide mixed solution; S2, adding single-walled carbon nanotubes to the polysaccharide mixed solution and dispersing them to obtain a composite precursor solution containing single-walled carbon nanotubes; S3, contacting the composite precursor solution with a crosslinking solution containing zinc ions to form dynamic coordination bonds between zinc ions and carboxyl groups to obtain the single-walled carbon nanotube composite hydrogel.

[0047] Preparation of Sample A: Sodium carboxymethyl cellulose and sodium alginate were dissolved in deionized water at a mass ratio of 1:1 and stirred overnight until completely dissolved to obtain a polysaccharide mixture with a total mass concentration of 5.0 wt%. 0.1% (by mass) of single-walled carbon nanotubes were weighed and added to the polysaccharide mixture. The mixture was then treated with a 200 W ultrasonic probe in an ice bath for 30 minutes to obtain a uniform black composite precursor solution. The composite precursor solution was then poured into a mold and brought into contact with a 0.2 mol / L zinc chloride aqueous solution. Crosslinking was carried out at room temperature for 8 hours. The resulting hydrogel was then removed, and the surface was quickly rinsed with deionized water to remove any residual crosslinking solution, yielding the single-walled carbon nanotube composite hydrogel.

[0048] Preparation of Sample B: Except for adjusting the concentration of the zinc chloride crosslinking solution to 0.4 mol / L, the other conditions were the same as those for sample A.

[0049] Preparation of sample C: Except for adjusting the concentration of the zinc chloride crosslinking solution to 0.08 mol / L, the other conditions were the same as those for sample A.

[0050] Preparation of sample D: Except for adjusting the amount of single-walled carbon nanotubes added to 5.0% of the polysaccharide mass, all other conditions were the same as for sample A. This sample was used to test the effect of higher single-walled carbon nanotube content on photothermal properties and resistance temperature response properties.

[0051] Preparation of sample E: Except for adjusting the mass ratio of sodium carboxymethyl cellulose to sodium alginate to 1:4, the other conditions were the same as those for sample A.

[0052] The above samples are only used to illustrate the functional gels that this system can process, and do not mean that this application only protects this specific formulation.

[0053] Example 3: Photothermal treatment and resistance change rate feedback control like Figure 1 As shown, the infrared light source module irradiates near-infrared light onto the conductive photothermal hydrogel attached to the body surface. Single-walled carbon nanotubes absorb the light energy and convert it into heat energy, causing the hydrogel to heat up. Simultaneously, the electrical signal acquisition module collects the hydrogel's resistance in real time. The control module determines the temperature based on the "resistance-temperature mapping relationship" and adjusts the laser power through closed-loop feedback control to achieve precise temperature control.

[0054] To establish this mapping relationship, we constructed a two-electrode system under test conditions and tested the change in the resistivity response of the hydrogel at different temperatures. For example... Figure 4 As shown, the resistivity response parameters of the hydrogel in the temperature range of 25℃ to 50℃ can establish a good fit relationship with temperature, and the goodness of fit R0 is high. 2 The value is 0.999. This result confirms the feasibility and accuracy of using resistance to infer temperature.

[0055] Example 4: Stability in physiological saline environments and self-dissolution performance in low-ion aqueous media To verify that the conductive photothermal gel can maintain structural stability during photothermal treatment, samples A to E were made into cylindrical samples with a diameter of 10 mm and a height of 5 mm, and immersed in 50 mL of PBS and 50 mL of deionized water, respectively, and the mass residue rate was tested at 37 °C.

[0056] The formula for calculating the residual rate is: R = mt / m0 × 100% Where m0 is the initial mass, and mt is the mass after soaking and drying the surface moisture. When R is less than 1%, it is considered to be completely self-dissolving.

[0057] The test results are as follows: Table 1. Comparison of solubility stability of hydrogels with different formulations

[0058] Furthermore, the following comparative examples are provided to illustrate the technical advantages of the present invention: Comparative Example 1: Acrylamide monomer and N,N'-methylenebisacrylamide crosslinking agent were subjected to free radical polymerization under the initiation of ammonium persulfate, and an equal amount of single-walled carbon nanotubes were incorporated to obtain a composite hydrogel with a permanent covalent network.

[0059] Comparative Example 2: The zinc ions in the formulation of Sample A in Example 2 were replaced with calcium ions, and crosslinking was performed using calcium chloride solution. The remaining steps were the same as those in Sample A.

[0060] Comparative Example 3: Zinc ions in Sample A of Example 2 were replaced with iron ions, and crosslinking was performed using ferric chloride solution. The resulting hydrogel hardened, its flexibility decreased, and it did not readily swell or self-dissolve in deionized water.

[0061] Comparative Example 4: The zinc ions in Sample A of Example 2 were replaced with sodium ions, and the sample was treated with sodium chloride solution. A stable hydrogel could not be formed after treatment.

[0062] Comparative Example 5: The zinc ions in the formulation of Sample A from Example 2 were replaced with aluminum ions, and the sample was treated with aluminum chloride solution. After treatment, it was difficult to form the same flexible, self-dissolving hydrogel as Sample A.

[0063] Comparative Example 6: The zinc chloride solution crosslinking step in Example 2 was omitted, and the composite precursor solution was placed directly in deionized water. The results showed that no stable gel was formed.

[0064] Comparative Example 7: Polyvinyl alcohol solution was mixed with single-walled carbon nanotubes and physically cross-linked hydrogels were prepared by cyclic treatment of freezing at -20°C for 12 hours and thawing at room temperature for 4 hours. The number of cycles was 3, and the hydrogels contained no zinc ions.

[0065] The test results are summarized in Table 2 below: Table 2:

[0066] The results indicate that samples A through E exhibit a dual-phase characteristic: stability in physiologically saline environments and self-dissolution in low-ion aqueous media. The self-dissolution time of the hydrogel generally increases with increasing zinc ion crosslinking solution concentration. Covalent network hydrogels are difficult to self-dissolve, and conventionally physically crosslinked hydrogels show insufficient stability in PBS. Structures formed by calcium ion crosslinking only partially disintegrate in deionized water. Iron ion crosslinking hardens the hydrogel, making it difficult to self-dissolve. Sodium ions cannot crosslink to form a hydrogel. Aluminum ion crosslinking makes it difficult to form a flexible, self-dissolving hydrogel. Without crosslinking ions, no gel can be formed.

[0067] Furthermore, sample A was placed in air exposure, a simulated skin adhesion environment, and a simulated dressing coverage environment to observe its macroscopic morphology and operability. The results showed that sample A maintained its intact macroscopic gel structure in a relatively dry environment without continuous contact with deionized water, purified water, or low-salt rinsing solution, and could be grasped, moved, and adhered. Subsequently, when similar samples were placed in deionized water, the samples gradually swelled, self-dissolved, and formed a black mixture.

[0068] This result indicates that the self-dissolution of hydrogels requires continuous contact between the external aqueous medium and the hydrogel, and the formation of a concentration gradient between the zinc ions contained in the hydrogel and the external aqueous medium to promote the outward diffusion of zinc ions.

[0069] Example 5: Mechanism verification of self-dissolution triggered by low-ion aqueous media To verify the migration of zinc ions from the hydrogel to the external aqueous medium during the self-dissolution of the hydrogel in a low-ion aqueous medium, zinc ion test strips were used to qualitatively detect the external aqueous medium at different immersion time points.

[0070] Sample A was prepared into a cylindrical sample with a diameter of 10 mm and a height of 5 mm. The following experimental group was set up: Group A: Place the hydrogel sample in 50 mL of deionized water; Group B: Place the hydrogel sample in 50 mL PBS; Group C: Only 50 mL of deionized water was used as a negative control, without the addition of hydrogel; Group D: An aqueous solution containing zinc ions was used as a positive control.

[0071] Under the same temperature conditions, external liquid samples were collected at the initial time point, early immersion time point, mid-immersion time point, and time point after the macroscopic gel structure disappeared. The zinc ion test strips were immersed in the external liquids collected at each time point, and color development was performed according to the color development time specified in the test strip instructions. The color changes of the test strips were recorded under the same light conditions.

[0072] The results showed that in group A, the color development of the zinc ion test strip gradually increased with prolonged soaking time; after the macroscopic gel structure disappeared, the external aqueous medium showed the most obvious color development of the test strip. In group B, the zinc ion test strip showed weak color development within the same observation time, and the hydrogel maintained its macroscopic gel structure. No obvious zinc ion color development was observed in group C. Obvious zinc ion color development was observed in group D.

[0073] The above results indicate that when the hydrogel comes into contact with an external aqueous medium having a lower total ion content compared to the physiological saline environment, the detection signal of zinc ions in the external aqueous medium increases with prolonged immersion time, suggesting that zinc ions contained in the hydrogel can migrate into the external aqueous medium. This result supports the following mechanism: when the external aqueous medium comes into contact with the hydrogel, a concentration gradient is formed that promotes the diffusion of zinc ions contained in the hydrogel into the external aqueous medium; as zinc ions migrate out, the dynamic coordination bonds formed between zinc ions and carboxyl groups decrease, the crosslinking density of the hydrogel decreases, and ultimately the macroscopic gel structure disappears.

[0074] Therefore, the low-ion aqueous medium self-dissolution recovery module is not a simple ordinary soaking container, but utilizes the ion-responsive self-dissolution characteristics of conductive photothermal hydrogel to transform the photothermally treated hydrogel into a mixture containing single-walled carbon nanotubes under mild conditions, thus providing a prerequisite for subsequent centrifugal recovery.

[0075] Example 6: Self-dissolution behavior in external aqueous media with different ionic strengths A cylindrical sample with a diameter of 10 mm and a height of 5 mm was prepared using sample A, with an initial mass denoted as m0. The sample was placed in sodium chloride aqueous solutions with different ionic strengths at a temperature of 37℃. The ionic strengths were 0 M, 0.005 M, 0.01 M, 0.02 M, and 0.05 M. The sample was removed at regular intervals, surface moisture was absorbed, and the sample was weighed, recorded as mt. The residual mass rate was calculated. Residual mass rate = mt / m0 × 100% When the residual mass is less than 1% and there is no visible gel residue, it is considered to be completely self-dissolving.

[0076] The test results are shown in Table 3: Table 3

[0077] The results showed that the self-dissolution behavior of the hydrogel was related to the ionic strength of the external aqueous medium. When the total ion content of the external aqueous medium was low, the hydrogel could undergo complete self-dissolution; when the ionic strength of the external aqueous medium increased, the self-dissolution of the hydrogel slowed down significantly or only swelled without complete dissolution.

[0078] This result further illustrates that the low-ion aqueous media self-dissolution recovery module should provide an external aqueous media with a lower total ion content relative to the physiological saline environment to create an ionic environment difference sufficient to promote the outward diffusion of zinc ions.

[0079] Example 7: Low-ion aqueous media self-dissolution and recovery module After the photothermal treatment is completed, medical staff remove the hydrogel from the patient's skin, and then the manufacturer collects it.

[0080] After collection, the manufacturer places a certain amount of gel medical waste into the recycling module. The module first activates an ultraviolet light source to sterilize the gel. Subsequently, deionized water is injected into the processing container by the supply unit, completely submerging the gel. Driven by the outward diffusion of zinc ions, the hydrogel undergoes self-dissolution, forming a mixture containing single-walled carbon nanotubes.

[0081] After complete dissolution, the mixture was fed into a high-speed centrifuge at 12,000 rad / min, causing the carbon nanotubes to precipitate. The supernatant was discarded, and the collected precipitate was washed with deionized water and ethanol, then vacuum dried at 80°C.

[0082] Finally, the dried carbon nanotube powder is transferred to an infrared heating unit, where it is heated to over 200°C by infrared light in an air atmosphere and maintained for a period of time to complete thorough sterilization, resulting in recycled single-walled carbon nanotubes that can be immediately put into remanufacturing.

[0083] Example 8: Recovery efficiency and recycling performance of single-walled carbon nanotubes The mixture obtained after complete autolysis of sample A was centrifuged for recovery, and the recovery rate Y of single-walled carbon nanotubes was calculated: Y = M_recycled / M_original × 100% Where M_recycled is the mass of the recycled single-walled carbon nanotubes, and M_original is the mass of the initially added single-walled carbon nanotubes.

[0084] The recycled powder was reused to prepare hydrogels for second- and third-generation cycle tests.

[0085] Comparative Example 8: The hydrogel prepared using Sample A was not subjected to external aqueous medium soaking for self-dissolution in the recovery step. Instead, it was placed in a buffer containing alginate lyase and cellulase, treated at 37°C for 24 hours, and then centrifuged for recovery.

[0086] Comparative Example 9: The hydrogel prepared using Sample A was treated with acid digestion in the recovery step and then centrifuged to recover single-walled carbon nanotubes, in order to compare the effect of severe chemical treatment on recovery rate and photothermal properties.

[0087] The test results are as follows: Table 4 Comparison of single-walled carbon nanotube recovery efficiencies

[0088] The above results demonstrate that, compared to enzymatic digestion, the water immersion + centrifugation method is simpler and does not require the use of biological enzymes; compared to acidic digestion, the water immersion + centrifugation method is more conducive to maintaining the recovery efficiency of single-walled carbon nanotubes. These results support the use of a low-ion aqueous medium self-dissolution recovery module in this system for the gentle recovery of photothermal-treated conductive photothermal gels.

[0089] Example 9: Photothermal Properties and Structural Retention of Recycled Single-Walled Carbon Nanotubes To evaluate the impact of the recycling process on the structure and photothermal properties of single-walled carbon nanotubes, the photothermal conversion efficiency and Raman spectroscopy of the recycled single-walled carbon nanotubes were measured.

[0090] The test results are as follows: Table 5 Comparison of multi-generation cycling performance of single-walled carbon nanotubes

[0091] The results showed that when using a low-ion aqueous medium for self-dissolution and centrifugal recovery, the photothermal conversion efficiency of the recovered single-walled carbon nanotubes decreased only slightly. The third generation showed a decrease of 1.6 percentage points compared to the first generation, with a photothermal conversion efficiency retention rate of approximately 96.3%. The Raman spectral ID / IG change was only +2.1%, indicating that the mild self-dissolution and centrifugal recovery process had little impact on the structure of the single-walled carbon nanotubes. In contrast, acidic digestion treatment led to a significant decrease in photothermal conversion efficiency (from 43.2% to 35.1%) and a significant increase in the ID / IG change (+25.4%), indicating that harsh chemical treatment is detrimental to maintaining the structure and function of single-walled carbon nanotubes.

[0092] The results indicate that the low-ion aqueous medium self-dissolution and recovery process used in this system has little impact on the single-walled carbon nanotube structure, which is beneficial to maintaining its photothermal conversion performance and structural integrity.

[0093] Example 10: Remanufacturing steps for recycled single-walled carbon nanotubes like Figure 8 As shown, this embodiment illustrates the subsequent remanufacturing steps for recycling single-walled carbon nanotubes.

[0094] The recovered single-walled carbon nanotube powder was added back into a polysaccharide mixed solution containing sodium carboxymethyl cellulose and sodium alginate, and ultrasonic dispersion was used to obtain a remanufacturing composite precursor solution.

[0095] Subsequently, the remanufacturing composite precursor solution is contacted with an aqueous solution of zinc chloride, allowing zinc ions to form dynamic coordination bonds with the carboxyl groups in carboxymethyl cellulose and sodium alginate, resulting in a remanufactured conductive photothermal gel.

[0096] The remanufactured conductive photothermal gel can form a macroscopic gel structure, maintain structural stability in PBS, and undergo self-dissolution in deionized water. This result demonstrates that the single-walled carbon nanotubes recovered through this system can be reused to prepare conductive photothermal gels, achieving the recycling of single-walled carbon nanotubes.

[0097] Example 11: Performance Testing Module In some implementations, the system also includes a performance testing module. This module can be positioned after the low-ion aqueous medium self-dissolution recovery module and is used to test the performance of the recovered single-walled carbon nanotubes.

[0098] The performance testing module can detect the following metrics: Raman spectral ID / IG ratio of recovered single-walled carbon nanotubes; Photothermal conversion efficiency of recycled single-walled carbon nanotubes; Dispersion stability of recycled single-walled carbon nanotubes; Morphology of recycled single-walled carbon nanotubes; Near-infrared heating curves of hydrogels reconstituted from recycled single-walled carbon nanotubes; The resistance-temperature response of hydrogels reconstituted from recycled single-walled carbon nanotubes; Stability of PBS after reprocessing hydrogels from recycled single-walled carbon nanotubes; The self-dissolution properties of low-ionic aqueous media after reprocessing hydrogels from recycled single-walled carbon nanotubes.

[0099] The performance testing module is not a necessary module of this system, but it can be used to improve the quality control capabilities before the recycling of single-walled carbon nanotubes.

[0100] Example 12: System Automated Operation Flow This embodiment provides a system automation operation process.

[0101] S1, causing the infrared light source module to irradiate infrared light onto the conductive photothermal gel, causing the conductive photothermal gel to produce a photothermal effect; S2, the resistance signal of the conductive photothermal gel is acquired in real time through the electrical signal acquisition module; S3, the control module calculates the rate of change or normalized rate of change of the resistance signal; S4, the control module determines the temperature state of the conductive photothermal gel based on the rate of change of the resistance signal or the normalized rate of change. S5, the control module adjusts the output of the infrared light source module according to the temperature status; S6, after the preset processing time, preset temperature state, or manual termination command is reached, the control module shuts down the infrared light source module; S7 allows the photothermal treated conductive photothermal gel to enter the low-ion aqueous medium self-dissolution and recovery module. S8 allows the conductive photothermal hydrogel to be continuously contacted with a low-ion aqueous medium until the macroscopic gel structure disappears and a mixture containing single-walled carbon nanotubes is formed. S9, the mixture containing single-walled carbon nanotubes is centrifuged to cause the single-walled carbon nanotubes to precipitate. S10, collect the single-walled carbon nanotube precipitate, and wash and dry it to obtain recovered single-walled carbon nanotubes; S11, As needed, perform performance testing on the recycled single-walled carbon nanotubes; S12, as needed, the recycled single-walled carbon nanotubes are redispersed in the hydrogel precursor solution, and the resulting composite precursor solution is crosslinked to form a remanufactured conductive photothermal hydrogel.

[0102] Example 13: Application Scenario of Photothermal Treatment and Recycling of Body Surface In a typical application scenario, the conductive photothermal hydrogel is made into a patch and applied to the target treatment area on the patient's skin. The system completes 5-10 minutes of photothermal therapy with precise temperature control according to a preset program. After treatment, the hydrogel is removed. Hospitals can collect these used hydrogels and return them to the manufacturer periodically. The manufacturer uses the recycling module of this invention for centralized processing, completing the entire process of sterilization, self-dissolution, separation, and re-sterilization. The regenerated high-value single-walled carbon nanotubes are used to manufacture new hydrogel patches, forming a closed-loop cycle of materials. This model greatly reduces the cost of consumables per treatment, allowing manufacturers to supply hospitals at lower prices, ultimately effectively reducing the economic burden on patients and promoting the widespread application of advanced treatment technologies.

[0103] Example 14: Effect of component changes on performance In the tests of samples A to E, it was observed that: when the concentration of the zinc ion crosslinking solution increased (sample B, 0.4 mol / L), the overall self-dissolution time of the hydrogel was prolonged (19.2 hours); when the concentration of the zinc ion crosslinking solution decreased (sample C, 0.08 mol / L), the self-dissolution time was shortened (7.0 hours). When the amount of single-walled carbon nanotubes added increased to 5.0% (sample D), the sample still maintained physiological saline environment stability and self-dissolution ability. When the mass ratio of sodium carboxymethyl cellulose to sodium alginate was adjusted to 1:4 (sample E), the self-dissolution time was shortened to 9.5 hours.

[0104] These results indicate that by adjusting the hydrogel formulation parameters, its self-dissolution behavior can be controlled within a certain range to meet the dissolution time requirements of different application scenarios.

[0105] Example 15: Control experiment with different crosslinking ions To further verify the unique role of zinc ions in this invention, cross-linking control experiments with different metal ions were conducted (Comparative Examples 2 to 6).

[0106] Comparative Example 2, using calcium ion crosslinking, produced a hydrogel with a 99.0% residue rate in PBS after 4 hours, but only partially disintegrated in deionized water after more than 72 hours, with the surface gelatinizing while the core remained a hard mass. Comparative Example 3, using iron ion crosslinking, resulted in a hardened hydrogel with reduced flexibility, making it difficult to swell and self-dissolve in deionized water. Comparative Example 4, using sodium ion treatment, failed to form a stable hydrogel. Comparative Example 5, using aluminum ion crosslinking, struggled to form the same flexible, self-dissolving hydrogel as sample A. Comparative Example 6, omitting the crosslinking step, failed to form a stable gel.

[0107] The above-described control experiments fully demonstrate that zinc ions play an irreplaceable role in this invention. The dynamic coordination bonds formed by zinc ions with the carboxyl groups in carboxymethyl cellulose and sodium alginate can provide sufficient cross-linking density to maintain the gel structure in physiologically saline environments, and can also dissociate due to concentration gradients in low-ion aqueous media, causing the hydrogel to self-dissolve. The coordination bonds formed by calcium ions are too stable and difficult to dissociate; iron and aluminum ions may lead to excessive cross-linking or the formation of other types of coordination structures, causing the hydrogel to harden or lose its self-dissolving ability.

[0108] Industrial applicability The system structure provided by this invention is clear, and each module can be implemented using existing industrial components. The conductive photothermal hydrogel preparation method upon which this invention relies is mild and uses inexpensive and readily available raw materials. This system can be manufactured and used in fields such as medicine, beauty, and material recycling, and can produce positive effects such as saving high-value nanomaterial resources and reducing waste emissions.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can make various modifications, equivalent substitutions, and improvements to the technical solutions of the present invention without departing from the spirit and principles thereof. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A body surface photothermal treatment and nanomaterial recovery system, characterized in that, include: An infrared light source module is used to irradiate infrared / near-infrared light onto a conductive photothermal gel disposed on the body surface, so that the conductive photothermal gel produces a photothermal effect. An electrical signal acquisition module is used to acquire the resistance signal of the conductive photothermal hydrogel; The control module is connected to both the infrared light source module and the electrical signal acquisition module, and is configured as follows: Obtain the resistance signal; The temperature state of the conductive photothermal hydrogel is determined based on a preset resistance-temperature mapping relationship. Based on the comparison between the determined temperature state and the target temperature, the output power of the infrared light source module is adjusted through closed-loop feedback control. A recycling module is used to contain the conductive photothermal gel removed from the body surface after photothermal treatment and to perform a recycling process to recover the single-walled carbon nanotubes therein. The conductive photothermal hydrogel is an ion-responsive self-dissolving single-walled carbon nanotube composite hydrogel, which contains carboxymethyl cellulose, sodium alginate, single-walled carbon nanotubes, and zinc ions; the zinc ions form dynamic coordination bonds with carboxyl groups to form a three-dimensional hydrogel network; the single-walled carbon nanotubes are dispersed in the three-dimensional hydrogel network. The conductive photothermal gel is configured to maintain a macroscopic gel structure in the physiological saline environment of the body surface; and to undergo self-dissolution when in contact with a low-ion aqueous medium, due to the outward diffusion of zinc ions leading to a reduction in the dynamic coordination bonds.

2. The system according to claim 1, characterized in that, The physiological saline environment on the body surface is a saline environment, a phosphate buffer environment, or a moist saline environment on the body surface.

3. The system according to claim 1, characterized in that, The control module is also configured to control the total duration of each photothermal treatment to be between 5 and 10 minutes.

4. The system according to claim 1, characterized in that, The recycling process executed by the recycling module includes: The conductive photothermal gel removed from the body surface is brought into contact with a low-ionic aqueous medium, triggering its self-dissolution to form a mixture containing single-walled carbon nanotubes. The mixture containing single-walled carbon nanotubes was centrifuged to obtain single-walled carbon nanotube precipitate. The single-walled carbon nanotube precipitate is washed and dried to obtain recovered single-walled carbon nanotubes.

5. The system according to claim 4, characterized in that, The recycling module is also equipped with an ultraviolet light source for sterilizing the conductive photothermal gel by ultraviolet irradiation before it comes into contact with the low-ion aqueous medium.

6. The system according to claim 4, characterized in that, The recycling module also includes an infrared heating unit for irradiating the dried recycled single-walled carbon nanotubes with infrared light. The infrared irradiation heats the carbon nanotubes to over 200 degrees Celsius in an air atmosphere to achieve sterilization.

7. The system according to claim 1, characterized in that, The preset resistance-temperature mapping relationship is a quantitative relationship established by pre-testing and calibrating the resistance values ​​of the conductive photothermal hydrogel at different temperatures.

8. The system according to claim 1, characterized in that, The control module implements closed-loop feedback control through a PID control algorithm.

9. A method for photothermal treatment of body surface and recovery of nanomaterials using the system according to any one of claims 1-8, characterized in that, include: The infrared light source module irradiates infrared light onto the conductive photothermal gel placed on the body surface to generate a photothermal effect. The resistance signal of the conductive photothermal gel is acquired by an electrical signal acquisition module; The control module adjusts the output power of the infrared light source module based on the preset resistance-temperature mapping relationship and closed-loop feedback control, according to the collected resistance signal, so as to maintain the temperature within the target range. After the photothermal treatment is completed, the conductive photothermal gel is removed from the body surface and placed into the recycling module; The conductive photothermal gel is brought into contact with a low-ion aqueous medium, triggering self-dissolution to form a mixture containing single-walled carbon nanotubes; The mixture containing single-walled carbon nanotubes is separated and dried to recover the single-walled carbon nanotubes.

10. The method according to claim 9, characterized in that, Before the step of triggering self-dissolution, the method further includes a step of sterilizing the conductive photothermal gel removed from the body surface by ultraviolet irradiation; after the drying treatment, the method further includes a step of sterilizing the recovered single-walled carbon nanotubes by infrared irradiation, wherein the infrared irradiation causes the carbon nanotube temperature to reach above 200 degrees Celsius.

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