A method for regulating 4D printing and flexible long-distance transport of liquids through synergistic surface wettability response of nanostructures.

Abstract

This invention discloses a method for controlling the flexible long-distance transport of liquids through 4D printing with a nanostructure synergistic with surface wettability response. The method utilizes a Crassula muscosa-like surface array prepared by photopolymerization 4D printing, combined with a micro / nano composite structure formed by surface-modified TiO2 nanoparticles. This achieves adaptation to liquids with different surface tensions and controllability of the one-dimensional transport direction. Based on the shape memory effect of thermal stimulus response, the surface array structure can be programmed, fixed, restored, and reversibly deformed multiple times, thereby controlling its movement direction in real time during liquid transport. Furthermore, by modifying the array surface with TiO2 nanoparticles, changes in surface chemical properties can be induced under ultraviolet light irradiation, thereby achieving dynamic control of surface wettability and expanding the transport capacity for liquids with different surface tensions.

Description

Technical Field

[0001] This invention belongs to the field of liquid transportation technology and relates to a method for regulating long-distance liquid transportation. Specifically, it relates to a method for photopolymerization 4D printing with nanostructure synergistic surface chemical response and for regulating flexible long-distance liquid transportation. Background Technology

[0002] Controlling the directional, long-distance transport and flexible control of liquids on open surfaces has significant application value in areas such as directional cooling, chemical reactors, and medical microfluidics. Currently, relevant control strategies are mainly divided into two categories: active and passive. Active strategies rely on external fields (such as light, electricity, and magnetic fields) to drive liquid movement, offering advantages such as rapid response, high control precision, and real-time adjustment. However, their application is limited by the physicochemical properties of the liquid itself and specific surface designs, resulting in high energy consumption and system complexity, and typically only enabling short-distance transport. Passive strategies, on the other hand, drive directional liquid movement through wettability gradients or structural differences introduced by surface structure or chemical properties, showing potential for low power consumption and long-distance transport. However, current open-surface liquid transport interfaces based on chemical gradients, structural gradients, or capillary forces are mostly limited to a pre-set single transport direction, with the fundamental bottleneck being the lack of dynamically reconfigurable wettability gradients. Once these surfaces are fabricated, their transport paths are fixed and difficult to adjust in real-time according to actual needs or external conditions. Furthermore, passive strategies are typically only applicable to liquids within a specific surface tension range. How to achieve flexible transport and control of liquids with varying surface tensions over long distances using this strategy remains a critical issue that urgently needs to be addressed. Summary of the Invention

[0003] This invention provides a method for regulating the flexible long-distance transport of liquids through 4D printing and surface wettability synergistic of nanostructures. Inspired by the succulent plant *Crassula muscosa*, native to South Africa and Namibia, which exhibits a unique ability to directionally transport liquids on its stem and leaf surfaces: when liquid is deposited on its surface, it spontaneously moves unidirectionally in opposite directions due to differences in stem and leaf angles. Inspired by this, this invention proposes a 4D-printed biomimetic array based on the *Crassula muscosa* structure. This structure is fabricated using a photocurable resin with shape memory effect via digital light processing (DLP) 3D printing technology, enabling macroscopic morphology reconstruction under external stimuli. Simultaneously, nanostructures that respond to external stimuli and induce surface chemical changes are constructed on its surface, thereby synergistically achieving dynamic regulation of macroscopic morphology and wettability. Based on this mechanism, this invention provides a method for regulating the flexible and directional transport of liquids with multi-range surface tension over long distances.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A method for regulating 4D printing and flexible long-distance liquid transport through synergistic surface wettability response of nanostructures includes the following steps:

[0006] Step 1: Preparation of photopolymerization (DLP) 4D printing resin with shape memory effect:

[0007] The 4D printing resin comprises a tetrafunctional thiol crosslinking agent, a difunctional acrylate chain-forming agent, a monofunctional acrylate diluent, a photoinitiator, a light absorber, a free radical inhibitor, and a thermal free radical initiator. The mass ratio of the tetrafunctional thiol crosslinking agent, the difunctional acrylate chain-forming agent, and the monofunctional acrylate diluent is 30-50:30-40:10-40. The tetrafunctional thiol crosslinking agent is pentaerythritol tetramercaptoacetate; the difunctional acrylate chain-forming agent is a polyurethane-acrylate crosslinking agent. CN996, CN966, CN9021, polyethylene glycol diacrylate, and tripropylene glycol diacrylate are selected from the following: The monofunctional acrylate diluent is one or more of isobornyl methacrylate (IBOA), hydroxyethyl acrylate (HEA), 4-acryloylmorpholine, and N-vinylpyrrolidone; the photoinitiator is photoinitiator 819, and its dosage is 0.5~1.5% of the total mass of the tetrafunctional thiol crosslinking agent, the difunctional acrylate chain-forming agent, and the monofunctional acrylate diluent. The light absorber is Sudan III, used at a concentration of 0.01–0.05 wt% of the total mass of the tetrafunctional thiol crosslinking agent, difunctional acrylate chain-forming agent, and monofunctional acrylate diluent; the free radical inhibitor is p-methoxyphenol, used at a concentration of 0.01–0.05 wt% of the total mass of the tetrafunctional thiol crosslinking agent, difunctional acrylate chain-forming agent, and monofunctional acrylate diluent; the thermal free radical initiator is one of the following: azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), dimethyl azobisisobutyrate (AIBME), benzoyl peroxide, or ammonium persulfate, used at a concentration of 0.5–1.5 wt% of the total mass of the tetrafunctional thiol crosslinking agent, difunctional acrylate chain-forming agent, and monofunctional acrylate diluent. wt% , place the tetrafunctional thiol crosslinking agent, difunctional acrylate chain-forming agent and monofunctional acrylate diluent in a container and mix them evenly. Under light-protected conditions, add the photoinitiator, light absorber, free radical inhibitor and thermal free radical initiator and mix evenly. Store in a light-protected place.

[0008] Step 2: Design and construction of blade structural units inspired by Crassula muscosa:

[0009] Using Solidworks software, 3D modeling of structural elements was performed to construct a structure resembling the Crassula muscosa blade. The structural element consists of two parts: an inverted trapezoidal cylindrical structure in the lower half and an oblique conical structure in the upper half. The base of the inverted trapezoidal cylindrical structure has a diameter of [missing information]. A circle, the upper half of which has a diameter of The circle The cross-section is trapezoidal, with one side of length being... The angle between the base and the ground is The side length of the other waist is The angle between the base and the ground is The bottom platform of the oblique conical structure has a diameter of It is a circle with a pointed pyramidal top and a triangular cross-section, where the side length of the base is 1. The side length of one side is The length of the other side is The height of the lower half of the prism is The height of the upper part of the pyramid is The angle between the lateral edge and the base of the prism is ; , , , , , , , , , , , ;

[0010] Step 3: Design and construction of a Crassula muscosa-inspired surface array structure:

[0011] A rectangular base plate model was constructed using Solidworks software, and then assembled and linearly arrayed with the symmetrical structural units designed in step 2 to obtain a surface array structure assembly model, wherein the spacing between adjacent structural units is 5.0 mm.

[0012] Step 4: 4D print the Crassula muscosa-inspired surface array structure based on the constructed 3D model:

[0013] The surface array structure assembly model is imported into the 3D printer and 4D printed using the 4D printing resin from step 1. The printed sample is ultrasonically cleaned in ethanol and stored away from light. The printing parameters are as follows: the sample is cured layer by layer to the upper platform under a 385nm light source, and the height of each cured layer is 0.1mm.

[0014] Step 5: Pre-treat the nanoparticles with ultraviolet light response:

[0015] Anatase titanium dioxide (TiO2) nanoparticles were pretreated at 150-180℃ for 2-4 hours to ensure that the hydroxyl groups on their surface were completely eliminated.

[0016] Step 6: Construct micro / nano structures on the surface of the 4D-printed Crassula muscosa-inspired surface array structure:

[0017] The surface of the printed Crassulamuscosa-inspired surface array structure was modified using anatase titanium dioxide (TiO2) nanoparticles pretreated in step 5. The specific steps are as follows:

[0018] Step 6-1: Add the pretreated anatase TiO2 nanoparticles from step 5 to the solution and ultrasonically vibrate to form a stable suspension. The solution is one of ethyl acetate, isopropanol, methanol, or butyl acetate.

[0019] Step 6-2: Add a 4D-printed Crassula muscosa-like surface array structure to the suspension and perform ultrasonic vibration. The ultrasonic vibration time is 3 to 8 minutes, for example, 3 minutes, 5 minutes or 8 minutes. Different ultrasonic vibration times will modify the surface of the Crassula muscosa-like surface array structure with different loading amounts of TiO2 nanoparticles.

[0020] Step 6-3: After ultrasonic vibration, take out the sample and dry it in an oven at 80~100℃ for 30~60 minutes to obtain a surface array structure of Crassula muscosa modified with TiO2 nanoparticles.

[0021] Step 7: Post-curing treatment of the surface of the 4D printed array with micro / nano structures:

[0022] The Crassula muscosa-like surface array structure with TiO2 nanoparticles on its surface was heated at 70~90℃ for 3~5 hours to achieve further solidification and enhance the fixation effect of nanoparticles on the surface of the structure.

[0023] Step 8: Shape variation and surface chemical property control of 4D printing of Crassula muscosa-inspired surface arrays:

[0024] Step 8-1: After modifying TiO2 nanoparticles, the printed model is heated to above its glass transition temperature (Tg), and then the printed Crassula muscosa-like surface array is tilted and deformed at 20° along the direction of the cone. It is then cooled to room temperature in this state to fix the shape, thereby realizing the shape change of the surface array structure based on thermal stimulus response in 4D printing.

[0025] Step 8-2: Irradiate the Crassula muscosa-like surface array with micro-nano structure (TiO2 nanoparticle modification) under ultraviolet light to induce a chemical change, thereby achieving the regulation of surface wettability in response to ultraviolet light. The wavelength of the ultraviolet light is 254nm, 365nm or 405nm, and the irradiation time is 10~60min, for example 10min, 20min, 30min, 40min or 60min.

[0026] Step 9: Controlling the direction of liquid directional transport in Crassula muscosa-inspired surface arrays:

[0027] Step 9-1: Inject liquid onto the surface of the Crassula muscosa array obtained in step 8. The liquid will be transported along its structural contour in the opposite direction to the direction of the cone, and will be suppressed on the other side. After the array is tilted and deformed by 20° along the direction of the cone, liquid will be injected onto the surface of the array. The liquid will spread along the direction of the cone, and will be suppressed on the other side.

[0028] Step 9-2: After exposing the surface to ultraviolet light for different durations, liquids with different surface tension ranges can be transported. Specifically: when the ultrasonic time is 3 minutes, the surface tension range of liquids that can be transported by the Crassula muscosa-like array without ultraviolet light irradiation is 22.1~24.5 mN / m; when irradiated with ultraviolet light for 10 minutes, the surface tension range of liquids that can be transported is 22.1~30 mN / m; and when irradiated with ultraviolet light for 20 minutes, 30 minutes, 40 minutes, and 60 minutes, the surface tension range of liquids that can be transported is 22.1~33 mN / m. When the ultrasonic time is 5 minutes, the surface tension range of liquids that can be transported by the Crassula muscosa-like array without ultraviolet light irradiation is 22.1~24.5 mN / m. The surface tension range of liquids that can be transported by the Muskosa array is 22.1~24.5 mN / m. After 10 min of UV irradiation, the surface tension range is 22.1~30 mN / m; after 20 min and 30 min of UV irradiation, the surface tension range is 22.1~30 mN / m; after 40 min and 60 min of UV irradiation, the surface tension range is 22.1~40 mN / m. When the ultrasonic time is 8 min, the surface tension range of the Crassula-like liquid without UV irradiation is... The surface tension range of liquids that can be transported by the Muskosa array is 22.1~24.5 mN / m. The surface tension range of liquids that can be transported after 10 min of ultraviolet light irradiation is 22.1~30 mN / m, after 20 min of ultraviolet light irradiation is 22.1~33 mN / m, after 30 min of ultraviolet light irradiation is 22.1~40 mN / m, and after 60 min of ultraviolet light irradiation is 22.1~72.8 mN / m.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] This invention utilizes a Crassula muscosa-inspired surface array fabricated by photopolymerization 4D printing, combined with a micro / nano composite structure formed by surface-modified TiO2 nanoparticles. This achieves adaptation to liquids with varying surface tensions and tunable one-dimensional transport direction. Based on the shape memory effect of thermal stimulus response, the surface array structure can be programmed, fixed, restored, and reversibly deformed multiple times, thereby controlling its movement direction in real time during liquid transport. Furthermore, by modifying the array surface with TiO2 nanoparticles, changes in surface chemical properties can be induced under ultraviolet light irradiation, enabling dynamic control of surface wettability and expanding the transport capacity for liquids with different surface tensions. Attached Figure Description

[0031] Figure 1 grass Figure 2 Floor plan;

[0032] Figure 2 A 3D model of structural units that mimic the leaf morphology of Crassula muscosa;

[0033] Figure 3 A 3D model of the Crassula muscosa surface array structure;

[0034] Figure 4 The original shape of the 3D model of the Crassula muscosa surface array structure;

[0035] Figure 5 The deformed shape of the 3D model of the Crassula muscosa surface array structure;

[0036] Figure 6 The structure is a Crassula muscosa-like surface array modified with TiO2 nanoparticles.

[0037] Figure 7 To regulate the directional transport of dimethyl silicone oil on a Crassula muscosa-inspired surface array structure;

[0038] Figure 8 The change in wettability of DMF on a Crassula muscosa-like surface array structure after ultraviolet irradiation. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0040] Example 1: Regulation of directional transport of dimethyl silicone oil and N,N-dimethylformamide

[0041] Step 1: The 4D printing resin contains a tetrafunctional thiol crosslinking agent, a difunctional acrylate chain-forming agent, a monofunctional acrylate diluent, a photoinitiator, a light absorber, a free radical inhibitor, and a thermal free radical initiator. 40 wt% pentaerythritol tetramercaptoacetate crosslinking agent, 30 wt% tripropylene glycol diacrylate chain-forming agent, 20 wt% 4-acryloylmorpholine diluent, and 10 wt% hydroxyethyl acrylate diluent are placed in a container and mechanically stirred for 6 hours to ensure uniform mixing. Subsequently, under light-protected conditions, 1 wt% of the total polymer mass of photoinitiator 819, 0.05 wt% of light absorber Sudan III, 0.01 wt% of the free radical inhibitor p-methoxyphenol, and 1 wt% of the thermal free radical initiator azobisisoheptanenitrile are added. The mixture is then sonicated in an ice-water bath for 15 minutes until completely dissolved and stored in the dark. After curing under 385 nm ultraviolet light for 5 minutes, the resulting glass transition temperature (Tg) is determined. g The temperature is 75℃, and the resin prepared has a good shape memory effect after curing.

[0042] Step 2: Create a part (Part 1) using SolidWorks software and establish a reference plane (Plane 1). Draw a circular sketch with a bottom diameter of 1 mm within this plane. Figure 1 Next, create plane 2, making it perpendicular to plane 1. Draw a sketch on plane 2. Figure 2 ,like Figure 1 As shown, the sketch is an inverted trapezoidal structure: the upper base is 1 mm long, and the grass... Figure 1 The diameters of the trapezoids coincide; the length of the lower base is 3 mm; one side of the trapezoid is 2 mm long and forms an angle of 40° with the base; the other side of the trapezoid is 1.37 mm long and forms an angle of 70° with the base. A triangle is connected to the top of the trapezoid, with one side coinciding with the lower base of the trapezoid, one side extending 4.36 mm along the 1.37 mm side of the trapezoid, and the other side being 6.32 mm long. The 3D model is as follows: Figure 2 As shown.

[0043] Next, create plane 3 at a vertical distance of 1.29 mm from plane 2, and draw a circular sketch with a diameter of 3 mm within this plane. Figure 3 Its diameter coincides with the lower base of the trapezoid. Continue by creating plane 4 at a distance of 4.35 mm from plane 3, and create a point sketch on plane 3 (sketching). Figure 4 The location of this point is relative to the grass. Figure 2 The top vertices of the middle triangle coincide. Finally, the grass is placed using the lofting boss operation. Figure 1 with grass Figure 3 Connect, then put the grass Figure 3 with grass Figure 4Lofting bosses are created to construct structural units that mimic the blade shape of Crassula muscosa, and these units are saved with filenames ending in .SLDPRT.

[0044] Step 3: Create a part (Part 2) in SolidWorks and establish a reference plane (Plane 1). Draw a rectangular outline (sketching) on ​​this plane with a length of 40 mm and a width of 10 mm. Figure 1 Perform an extrude boss operation on the sketch, setting the extrude depth to 2 mm, to generate a cuboid solid with dimensions of 55 mm × 50 mm × 1.5 mm. Continue creating the sketch on plane 1. Figure 2 Draw a circular outline with a diameter of 1 mm, centered at the center point of the plane. After completing the sketch, save Part 2 as a .SLDPRT format file. Next, create a new assembly file and insert Part 1 and Part 2 in sequence. Add mate relationships so that the sketch in Part 1... Figure 1 With Part 2 Figure 2 The centers of the circles in the diagram coincide. Then, along the length of part 2, a two-dimensional linear array of the surface of part 1 is created, with the spacing between adjacent units set to 5 mm, thus constructing a 3D model of a Crassula muscosa-like surface array structure, as shown below. Figure 3 As shown. Finally, the assembly is saved as an .STL file for later application or output.

[0045] Step 4: Import the .STL file of the assembly from Step 2 into the slicing software for slicing. The layer height of the model slice is 0.1mm. Pour the resin from Step 1 into the resin tank of the DLP 3D printer, import the slice file into the 3D printer, and perform 3D printing. The printing parameters are as follows: printing at 25℃ under a 385nm wavelength light source with a light source power of 1000W; the first layer curing time is 30s, the substrate curing layer is 3 layers, and the lifting height of each layer is 5mm; subsequently, the curing time of each layer is 10s. After printing, ultrasonically clean the printed array structure in ethanol for 5min to remove unpolymerized components from the surface; at this time, the sample is not fully cured and needs to be stored away from light. After heating the printed sample in an oven at 85℃ for 10min, tilt the array 20° along the direction of the cone and cool it to room temperature to keep it fixed. The 3D printed Crassula muscosa-like surface array structure is thus 4D printed. The original shape of the 3D model of the Crassula muscosa-like surface array structure is as follows. Figure 4 As shown, the deformed shape is as follows Figure 5 As shown.

[0046] Step 5: Pre-treat titanium dioxide (TiO2) nanoparticles at 150°C for 3 hours to ensure that the hydroxyl groups on their surface are completely eliminated.

[0047] Step 6: Add 1.5g of pretreated TiO2 nanoparticles to 50g of ethyl acetate solution and sonicate to form a stable suspension. Add a 3D-printed Crassula muscosa-inspired surface array structure to the suspension and sonicate for 5 minutes before removing it.

[0048] Step 7: After removing the sample, place it in a 70℃ oven for heat curing for 4 hours to obtain a fully cured 3D-printed Crassula muscosa-like surface array structure modified with TiO2 nanoparticles. Figure 6 As shown.

[0049] Step 8: Dimethyl silicone oil is injected at a rate of 1.43 μL / s onto the structural units of the printed array structure. The dimethyl silicone oil is directionally transported along the structural contour towards the array in the opposite direction to the cone direction, while the transport is inhibited on the other side. The transport speed is 2.06 mm / s. After tilting the array 20° along the cone direction, dimethyl silicone oil is injected onto the array surface. The liquid is then directionally transported along the cone direction, while the transport is inhibited on the other side. When dimethyl silicone oil (350 cSt, surface tension 20.6 mN / m) is injected at a rate of 1.43 μL / s onto the surface of the printed cone array structure, the liquid is directionally transported in the opposite direction towards the cone along the structural contour, while the transport in the opposite direction is inhibited, reaching a transport speed of 2.06 mm / s. When the array is tilted 20° along the cone direction, the silicone oil is directionally transported along the cone direction, and the reverse transport is inhibited. The adjustment of the directional transport of dimethyl silicone oil in the Crassulamuscosa-inspired surface array structure is as follows: Figure 7 As shown.

[0050] Step 9: The structure shape was restored by heating at 85℃, and the sample was irradiated with 385 nm ultraviolet light for 40 minutes to achieve photoresponse modulation of surface wettability. After irradiation, the contact angle of the structure surface with N,N-dimethylformamide (DMF, surface tension 37.1 mN / m) decreased from 57.42° to 16.09°, indicating that it changed from a hydrophobic state to a highly hydrophilic state, and the wettability changed. On the UV-modulated array surface, when DMF was injected at the same rate (1.43 μL / s), the liquid was also transported in the opposite direction to the cone along the structural contour at a speed of 2.06 mm / s; when the array was tilted again by 20°, DMF also switched to transport along the cone direction, and the reverse direction was suppressed. The change in wettability of DMF on the Crassula muscosa-inspired surface array structure after ultraviolet irradiation is as follows: Figure 8 As shown.

[0051] Example 2: Regulation of directional transport of ethanol and water

[0052] The difference between this embodiment and Embodiment 1 is that:

[0053] Step 1: The 4D printing resin contains a tetrafunctional thiol crosslinking agent, a difunctional acrylate chain-forming agent, a monofunctional acrylate diluent, a photoinitiator, a light absorber, a free radical inhibitor, and a thermal free radical initiator. 30 wt% pentaerythritol tetramercaptoacetate crosslinking agent, 30 wt% polyurethane-acrylate CN966 chain-forming agent, and 40 wt% isobornyl methacrylate diluent are placed in a container and mechanically stirred for 6 hours to ensure uniform mixing. Subsequently, under light-protected conditions, 1 wt% of the total polymer mass of photoinitiator 819, 0.05 wt% of light absorber Sudan III, 0.01 wt% of the free radical inhibitor p-methoxyphenol, and 1 wt% of the thermal free radical initiator azobisisobutyronitrile are added. The mixture is then sonicated in an ice-water bath for 15 minutes until completely dissolved and stored in the dark. After curing under 385 nm ultraviolet light for 5 minutes, the resulting glass transition temperature (Tg) is determined. g The temperature is 90℃, and the resin prepared has a good shape memory effect after curing.

[0054] Step 4: Import the .STL file of the assembly from Step 2 into the slicing software for slicing. The model slice layer height is 0.5mm. Pour the resin from Step 1 into the resin tank of the DLP 3D printer, import the slice file into the 3D printer, and perform 3D printing. The printing parameters are as follows: printing at 25℃ under a 385nm wavelength light source with a light source power of 1000W; the first layer curing time is 30s, the substrate curing layer number is 3 layers, and the lifting height of each layer is 5mm; subsequently, the curing time of each layer is 10s. After printing, ultrasonically clean the printed array structure in ethanol for 5min to remove unpolymerized components from the surface; at this time, the sample is not fully cured and needs to be stored away from light. After heating the printed sample in an oven at 100℃ for 10min, tilt the array 20° along the direction of the cone and cool it to room temperature to keep it fixed. The 3D printed Crassula muscosa-like surface array structure is thus 4D printed.

[0055] Step 6: Add 1.5g of pretreated TiO2 nanoparticles to 50g of ethyl acetate solution and sonicate to form a stable suspension. Add a 3D-printed Crassula muscosa-inspired surface array structure to the suspension and sonicate for 8 minutes before removing it.

[0056] Step 8: Inject anhydrous ethanol (surface tension 22.1 mN / m) at a rate of 1.43 μL / s onto the structural units of the printed array structure. The anhydrous ethanol is directionally transported along the structural contour towards the array in the opposite direction to the cone direction, while the transport is inhibited on the other side, with a transport speed of 2.22 mm / s. After tilting the array 20° along the cone direction, dimethyl silicone oil is injected onto the array surface. The liquid is then directionally transported along the cone direction, while the transport is inhibited on the other side. When anhydrous ethanol is injected at a rate of 1.43 μL / s onto the surface of the printed cone array structure, the liquid is directionally transported in the opposite direction towards the cone along the structural contour, while the transport in the opposite direction is inhibited, with a transport speed of 2.13 mm / s. When the array is tilted 20° along the cone direction, the anhydrous ethanol is directionally transported along the cone direction, and the reverse transport is inhibited.

[0057] Step 9: The structure shape is restored by heating at 100℃, and the sample is irradiated with 385 nm ultraviolet light for 60 minutes to achieve photoresponse modulation of surface wettability. After irradiation, the surface of the structure becomes highly hydrophilic to water (surface tension 72 mN / m), and the wettability changes. When water is injected into the UV-modulated array surface at the same rate (1.43 μL / s), the liquid is also transported in the opposite direction to the cone along the structural contour at a speed of 1.98 mm / s; however, when the array is tilted again by 20°, the water is transported in the direction of the cone, and the reverse direction is suppressed.

Claims

1. A method for controlling 4D printing and flexible long-distance transport of liquids through synergistic surface wettability response of nanostructures, characterized in that... The method includes the following steps: Step 1: Preparation of photopolymerization (DLP) 4D printing resin with shape memory effect: A tetrafunctional thiol crosslinking agent, a difunctional acrylate chain-forming agent, and a monofunctional acrylate diluent were mixed evenly in a container. Under light-protected conditions, a photoinitiator, a light absorber, a free radical inhibitor, and a thermal free radical initiator were added and mixed thoroughly. The mixture was then stored in a light-protected place. The mass ratio of the tetrafunctional thiol crosslinking agent, the difunctional acrylate chain-forming agent, and the monofunctional acrylate diluent was 30-50:30-40:10-40. The amounts of the photoinitiator, light absorber, free radical inhibitor, and thermal free radical initiator were 0.5-1.5 wt%, 0.01-0.05 wt%, 0.01-0.05 wt%, and 0.5-1.5 wt%, respectively, based on the total mass of the tetrafunctional thiol crosslinking agent, the difunctional acrylate chain-forming agent, and the monofunctional acrylate diluent. Step 2: Design and construction of blade structural units inspired by Crassula muscosa: Using Solidworks software, 3D modeling of the structural elements was performed to construct a structure resembling the Crassula muscosa blade. The structural element consists of two parts: an inverted trapezoidal cylindrical structure in the lower half and an oblique conical structure in the upper half. The base of the inverted trapezoidal cylindrical structure has a diameter of [missing information]. A circle, the upper half of which has a diameter of The circle The cross-sectional structure is trapezoidal, with one side of length being... The angle between the base and the ground is The side length of the other waist is The angle between the base and the ground is The bottom platform of the oblique conical structure has a diameter of It is a circle with a pointed pyramidal top and a triangular cross-section, where the side length of the base is 1. The side length of one side is The length of the other side is The height of the lower half of the prism is The height of the upper part of the pyramid is The angle between the lateral edge and the base of the prism is ; Step 3: Design and construction of a Crassula muscosa-inspired surface array structure: A rectangular base plate model was constructed using Solidworks software, and then assembled and linearly arrayed with the Crassula muscosa blade structure unit designed in step 2 to obtain a surface array structure assembly model. Step 4: 4D print the Crassula muscosa-inspired surface array structure based on the constructed 3D model: Import the surface array structure assembly model into the 3D printer, and perform 4D printing using the 4D printing resin from step 1. Place the printed sample in ethanol for ultrasonic cleaning and store it away from light. Step 5: Pre-treat the nanoparticles with ultraviolet light response: Anatase titanium dioxide nanoparticles were pretreated at 150-180℃ for 2-4 hours to ensure that the surface hydroxyl groups were completely eliminated. Step 6: Construct micro / nano structures on the surface of the 4D-printed Crassula muscosa-inspired surface array structure: The surface of the printed Crassula muscosa-inspired surface array structure was modified using anatase titanium dioxide nanoparticles pretreated in step 5. Step 7: Post-curing treatment of the surface of the 4D printed array with micro / nano structures: The Crassula muscosa-like surface array structure with TiO2 nanoparticles on its surface was heated at 70-90℃ for 3-5 hours. Step 8: Shape variation and surface chemical property control of 4D printing of Crassula muscosa-inspired surface arrays: Step 8-1: After modifying TiO2 nanoparticles, the printed model is heated to above its glass transition temperature. Then, the printed Crassula muscosa-like surface array is tilted and deformed at 20° along the direction of the cone. It is then cooled to room temperature in this state to fix the shape, thereby realizing the shape change of the surface array structure based on thermal stimulus response in 4D printing. Step 8-2: Irradiate the Crassula muscosa-like surface array with TiO2 nanoparticle modification under ultraviolet light to induce a chemical change, thereby achieving the regulation of surface wettability in response to ultraviolet light. Step 9: Controlling the direction of liquid directional transport in Crassula muscosa-inspired surface arrays: Step 9-1: Inject liquid onto the surface of the Crassula muscosa array obtained in step 8. The liquid will be transported along its structural contour in the opposite direction to the direction of the cone, and will be suppressed on the other side. After the array is tilted and deformed by 20° along the direction of the cone, liquid will be injected onto the surface of the array. The liquid will spread along the direction of the cone, and will be suppressed on the other side. Step 9-2: After exposing the surface to ultraviolet light for different durations, liquids with different surface tension ranges can be transported.

2. The method for controlling 4D printing and flexible long-distance liquid transport using nanostructure synergistic surface wettability response according to claim 1, characterized in that... In step 1, the tetrafunctional thiol crosslinking agent is pentaerythritol tetramercaptoacetate; the difunctional acrylate chain-forming agent is one of the following: polyurethane-acrylate crosslinking agent CN996, CN966, CN9021, polyethylene glycol diacrylate, and tripropylene glycol diacrylate; the monofunctional acrylate diluent is one or more of the following: isobornyl methacrylate, hydroxyethyl acrylate, 4-acryloylmorpholine, and N-vinylpyrrolidone; the photoinitiator is photoinitiator 819; the light absorber is Sudan III; the free radical inhibitor is p-methoxyphenol; and the thermal free radical initiator is one of the following: azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, and ammonium persulfate.

3. The method for controlling 4D printing and flexible long-distance liquid transport using nanostructure synergistic surface wettability response according to claim 1, characterized in that... In step 2, , , , , , , , , , , , .

4. The method for controlling 4D printing and flexible long-distance liquid transport using nanostructure synergistic surface wettability response according to claim 1, characterized in that... In step 3, the spacing between adjacent structural units is 5.0 mm.

5. The method for controlling 4D printing and flexible long-distance liquid transport using nanostructure synergistic surface wettability response according to claim 1, characterized in that... In step 4, the printing parameters are as follows: the layers are cured layer by layer onto the upper platform under a 385nm light source, and the height of each cured layer is 0.1mm.

6. The method for controlling 4D printing and flexible long-distance liquid transport using nanostructure synergistic surface wettability response according to claim 1, characterized in that... The specific steps of step 6 are as follows: Step 6-1: Add the pretreated anatase TiO2 nanoparticles from step 5 to the solution and ultrasonically vibrate to form a stable suspension; Step 6-2: Add a 4D-printed Crassula muscosa-like surface array structure to the suspension and perform ultrasonic vibration. Step 6-3: After ultrasonic vibration, the sample is taken out and placed in an oven at 80~100℃ for 30~60 minutes to dry, thus obtaining a surface array structure of Crassula muscosa modified with TiO2 nanoparticles.

7. The method for controlling 4D printing and flexible long-distance liquid transport using nanostructure synergistic surface wettability response according to claim 6, characterized in that... The solution is one of ethyl acetate, isopropanol, methanol, and butyl acetate, and the ultrasonic oscillation time is 3-8 min.

8. The method for controlling 4D printing and flexible long-distance liquid transport using nanostructure synergistic surface wettability response according to claim 1, characterized in that... In step 8-2, the wavelength of the ultraviolet light is 254nm, 365nm or 405nm, and the irradiation time of the ultraviolet light is 10~60min.

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