Balsa wood-based liquid metal tilt angle sensor and preparation method thereof

Abstract

The invention relates to a cork-based liquid metal tilt angle sensor, which comprises a delignified cork base body, a plurality of parallel and independent micro-channels are arranged in the cork base body, and a three-dimensional network is formed by radially communicated holes; and the gallium-based liquid metal alloy is filled in the plurality of micro-channels to form a distributed conductive path. When the sensor is inclined, the liquid metal is in each independent micro-channel under the action of the gravity of the liquid metal and is asynchronously redistributed, and the high-precision and high-sensitivity monitoring function of the inclination angle is realized through the resistance gradient change between the micro-channels.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sensors, and particularly relates to a balsa wood-based liquid metal tilt angle sensor and a preparation method thereof. BACKGROUND

[0002] Tilt angle, as a key parameter for describing the spatial posture of an object, has important application value in modern industrial control, aerospace and intelligent wear fields. Current tilt angle sensors are mainly divided into three categories according to working principles, namely solid pendulum type, liquid pendulum type and micro-electro-mechanical system type. Among them, the tilt angle sensor based on liquid metal exhibits unique advantages due to its excellent electrical conductivity and fluidity, and in particular, gallium-based liquid metal has attracted much attention in the field of flexible sensing due to its low toxicity and good environmental adaptability. However, the existing technology has significant defects: on the one hand, the sensor substrate is mostly made of polydimethylsiloxane (PDMS) or engineering plastics, which are non-renewable materials. These materials have complex preparation processes and are difficult to degrade, which can easily cause environmental pollution; on the other hand, the existing liquid metal tilt angle sensor generally adopts a single-channel chamber design, which relies on the displacement of the whole liquid column of liquid metal to realize resistance change, resulting in low sensitivity and poor signal stability in complex deformation scenarios.

[0003] Wood, as a kind of natural renewable resource, has become an important object of multidisciplinary research due to its unique microstructure and abundant reserves. Among them, balsa wood has low density and unique vessel structure, which provides new ideas and methods for developing new tilt angle sensing technology. However, natural balsa wood has low deflection and strong structural stability, which limits its application in the field of flexible sensing. Although researchers have tried to use biomass materials such as balsa wood to replace traditional substrates, the existing schemes still have obvious limitations: most of the technologies only use the piezoresistive effect of wood to realize pressure or strain sensing, which cannot meet the tilt angle detection requirements; some methods construct a single artificial channel on the surface of wood by etching, which not only destroys the natural vessel network structure, but also leads to distortion of the flow behavior of liquid metal; in addition, untreated balsa wood is too rigid to adhere to curved surfaces, which restricts flexible applications.

[0004] The present application creatively proposes a solution: by delignification treatment, the natural three-dimensional multi-microchannel network structure inside the balsa wood is retained (non-traditional single-channel structure), forming a distributed sensing chamber composed of dozens to hundreds of parallel microchannels and radially connected pores. When the sensor is tilted, the liquid metal undergoes asynchronous gravity displacement in each independent microchannel, and high sensitivity detection is achieved through resistance gradient change between microchannels. At the same time, delignification treatment makes the balsa wood substrate flexible, which can closely adhere to curved surfaces such as human joints, and the all-biomass substrate system fundamentally solves the technical problems of non-renewable materials and heavy environmental burden, providing an innovative path for green electronics. SUMMARY

[0005] In order to solve the problems existing in the prior art, the present application adopts natural balsa wood as a structure template, and performs delignification treatment on the balsa wood to retain the original three-dimensional conduit network structure inside the balsa wood, and forms a flexible matrix; then, liquid metal is injected into the conduits, and the change collection of the resistance signal is realized by using the gravity response behavior of the liquid metal under different inclined states, so that a flexible inclination sensor with angle sensing capability is constructed.

[0006] In a first aspect of the present application, a balsa wood-based liquid metal inclination sensor is provided, comprising: a delignification-treated balsa wood matrix, which contains a plurality of parallel independent microchannels inside and constitutes a three-dimensional network through radially communicating pith holes; gallium-based liquid metal filled in the plurality of microchannels to form a distributed conductive path; and preferably, the inclination sensor further comprises a liquid metal oxide coating layer coated on both ends of the matrix.

[0007] When the sensor is inclined, the liquid metal is redistributed in each independent microchannel under the action of its own gravity, and the inclination detection is realized through the resistance gradient change between the microchannels.

[0008] The balsa wood is mainly composed of cellulose microfibrils, hemicellulose and lignin three components filled in the cellulose microfibril network, and has a developed conduit structure and low density characteristics, so that it becomes a natural limited channel template for the liquid metal of the present application. After delignification treatment, the lignin is selectively dissolved and removed by chemical solvents (such as sodium chlorite / alkali treatment), and the balsa wood retains the cellulose skeleton and three-dimensional conduit network, while the porosity of the balsa wood is significantly increased, so that the roughness of the liquid metal surface is more easily changed during the rotation of the sensor, the electrical signal response is more sensitive, and the detection effect of the electrical signal is improved; at the same time, the balsa wood is endowed with certain flexibility and bendability, which better meets the demand of flexible electronic devices.

[0009] Further, the density of the plurality of parallel independent microchannels is 10-50 / cm 2 , and the distance between adjacent microchannels is 50-500 μm.

[0010] Further, the plurality of parallel independent microchannels are composed of the cellulose skeleton after delignification, the microchannel diameter is 10-200 μm, the microchannels are through along the axial direction of the matrix, and the radial communication is realized through the pith holes with a pore size of 0.1-10 μm.

[0011] Further, the liquid metal is gallium-based liquid metal alloy, preferably any one or more of gallium metal, gallium-indium alloy, gallium-tin alloy and indium-gallium-tin alloy.

[0012] Further, the liquid metal oxide coating layer is generated by the surface oxidation of the gallium-based liquid metal, and the thickness of the liquid metal oxide coating layer is 0.5-5 μm.

[0013] Further, the liquid metal oxide coating is further capped with silver paste.

[0014] Further, the balsa wood based liquid metal tilt sensor further comprises electrodes.

[0015] Further, the lignin in the balsa wood can be removed completely or partially, and the degree of lignin removal of the balsa wood can be 75% to 100%.

[0016] In a second aspect, the application provides a method for preparing the balsa wood based liquid metal tilt sensor of the first aspect, comprising the following steps:

[0017] 1) preparing a flexible substrate: treating natural balsa wood by delignification to remove lignin while keeping the three-dimensional vessel network structure intact, thereby forming a flexible balsa wood substrate with a plurality of parallel independent microchannels;

[0018] 2) constructing a coating on the outflow end of the substrate: coating the outflow end of the flexible substrate with liquid metal oxide to form a liquid metal oxide coating;

[0019] 3) injecting liquid metal: injecting liquid metal into the three-dimensional vessel network at the injection end of the flexible substrate to fill the plurality of parallel independent microchannels;

[0020] The balsa wood vessel wall is distributed with a large number of micron-scale pit structures, which form a naturally formed interconnected network of microchannels. By injecting liquid metal into the interior of the vessel, the liquid metal surface topography produces a differentiated roughness distribution as the tilt angle changes. This structure-induced interface regulation mechanism enables the liquid metal to exhibit significantly differentiated resistance response characteristics under different tilt angles, thereby providing a structural basis for high resolution and good stability of the tilt sensor.

[0021] 4) constructing a coating on the injection end of the substrate: coating the injection end of the flexible substrate with liquid metal oxide to form a liquid metal oxide coating; then coating the injection end and the outflow end of the substrate with conductive silver paste and leading out electrodes to obtain the balsa wood based liquid metal tilt sensor.

[0022] Further, in step 1), the delignification treatment uses sodium hypochlorite method or alkaline hydrogen peroxide method.

[0023] Preferably, the delignification is performed using sodium hypochlorite method, comprising the following steps:

[0024] (a) immersing dry balsa wood in a reaction solution containing sodium hypochlorite, and the effective chlorine concentration in the solution is 1.5 to 3 wt%;

[0025] (b) adding an acid to adjust the pH to 4-5, stirring the reaction at 90-110 DEG C, 100-500 rpm for 2-8 hours; the acid can be any acid solution, such as one or more of hydrochloric acid, phosphoric acid, acetic acid, etc.

[0026] (c) after the reaction is completed, cooling to room temperature, washing to neutral, drying at 50-70 DEG C to constant weight.

[0027] Further, in steps 2) and 4), the preparation method of the liquid metal oxide coating is to continuously stir the liquid metal at a speed of 200-700 rpm until the liquid metal is oxidized to form a paste-like oxide coating.

[0028] The present application coats a layer of liquid metal oxide coating on both ends of the substrate after delignification treatment, which not only realizes effective packaging of the liquid metal and improves the structural stability, but also effectively avoids the problem of poor electrode contact caused by uneven solidification of the conductive silver paste, thereby significantly enhancing the overall conductive performance of the sample and the reliability of the electrode connection. Moreover, coating the liquid metal oxide layer on both ends of the substrate helps to improve the interface bonding performance. The liquid metal oxide layer not only effectively increases the contact area between the liquid metal and the conductive silver paste, thereby enhancing the reliability of the electrical connection, but also enables the conductive silver paste to adhere more firmly to the surface of the substrate after solidification due to the adhesion of the liquid metal oxide, thereby significantly improving the stability of the structure when subjected to vibration, impact or other external disturbances, thereby avoiding or delaying the phenomenon of silver paste layer falling off or peeling off. In addition, the liquid metal oxide coating and the internally filled liquid metal belong to gallium-based liquid metal, which is more conducive to the stability of the resistance signal sensing, and optimizes the electrical signal change rate.

[0029] Further, the injection speed of the liquid metal in step 3) is 1-5 mL / min, so that the liquid metal medium forms a non-continuous gradient distribution in multiple parallel independent microchannels.

[0030] Further, in step 1) (a), the depth of the sodium chlorate solution is greater than 3 / 4 of the height of the balsa wood (in the direction of the microchannel).

[0031] Further, the dry balsa wood is immersed in the reaction solution containing sodium hypochlorite; or 3 / 4 of the height (in the direction of the microchannel) of the dry balsa wood is immersed in the reaction solution containing sodium hypochlorite.

[0032] In one embodiment of the present application, the dry balsa wood is immersed in the reaction solution containing sodium hypochlorite to achieve complete removal of lignin. This treatment greatly improves the porosity of the balsa wood, making it easier for the roughness of the liquid metal surface to change during rotation, thereby improving the detection effect of the electrical signal.

[0033] In another embodiment of the present application, the 3 / 4 height of the dried balsa wood is immersed in a reaction solution containing sodium hypochlorite to partially remove lignin. On the basis of maintaining the high porosity of the balsa wood matrix, the partial removal of lignin increases the gradient difference in the composition and structure of the capillary channels, and the liquid metal spontaneously distributes in a gradient, enhancing the direction sensitivity and controllability of its movement in the capillary, thereby improving the detection effect of the sensor.

[0034] In order to realize the precise regulation of the degree of delignification, the present application uses a partial immersion method to immerse the balsa wood sample (micro-channel direction) into a sodium hypochlorite solution for treatment. This process skillfully utilizes the capillary force inside the wood, so that the delignification reaction mainly occurs in the local area immersed in the solution and the adjacent area affected by the capillary force, thereby realizing the partial removal of lignin (range 75%<x<100%); causing the internal structure of the balsa wood to exhibit a unique gradient of components and properties. This gradient effect has a decisive influence on the confined behavior of liquid metal (such as gallium-based metal) in the capillary: on the one hand, the gradientized surface properties guide the liquid metal to exhibit differential wetting / shrinking behavior in different areas, enhancing the direction sensitivity and controllability of its movement in the capillary; on the other hand, when the sensor is rotated or deformed, the distribution pattern, contact area and interfacial resistance of the liquid metal in the gradient capillary network will change more significantly and complexly due to the position dependence. This enhanced interfacial dynamic response driven by the gradient structure directly translates into larger amplitude and higher signal-to-noise ratio of the electrical signal change, thereby improving the detection sensitivity, resolution and reliability of the sensor.

[0035] In a third aspect of the present application, the balsa wood-based liquid metal tilt angle sensor prepared by the first aspect or the second aspect is provided for use in angle detection.

[0036] The present application constructs a natural multi-channel template for liquid metal by delignified balsa wood, which breakthroughly solves the technical bottlenecks of traditional tilt angle sensors in terms of material environmental protection, structural adaptability and detection sensitivity, and has the following beneficial effects:

[0037] 1. The present application first combines balsa wood with a multi-channel three-dimensional structure with liquid metal for tilt angle sensing, replacing traditional plastic / synthetic resin substrates. Delignification treatment preserves the three-dimensional duct network of balsa wood while imparting flexibility (bending radius ≤ 5 mm), allowing the sensor to closely adhere to complex curved surfaces and better adhere to object surfaces to adapt to more application scenarios, especially flexible electronic devices.

[0038] 2. The present application utilizes the asynchronous gravity displacement of liquid metal in multiple channels (different from the traditional single-channel whole liquid column movement), and realizes the inclination detection through local resistance gradient change. The mechanism makes the sensor have a sensitivity of ≥0.5% in a full angle range of -90°-90°, which is more than 55% higher than the traditional single-channel design, and does not require complex circuit.

[0039] 3. As a renewable biomass resource, balsa wood is naturally degradable (degradation period <1 year), the liquid metal is low-toxic and environmentally friendly, and the overall material system meets the green manufacturing standard, significantly reducing electronic waste pollution. Moreover, under multiple bending (>4000 cycles), temperature changes and long-term use conditions, the resistance response fluctuation is small, and it has industrial-level reliability.

[0040] 4. The present application coats a liquid metal oxide layer (thickness 20-50 μm) at both ends of the substrate to realize chemical bonding packaging of the liquid metal, and combines the silver paste double-end sealing mechanism to avoid poor contact caused by uneven solidification of silver paste alone; at the same time, based on the homology of liquid metal, the conductivity of the electrode can be further improved, and the stability and sensitivity of signal transmission are enhanced.

[0041] 5. The present application first attempts to partially delignify balsa wood as the substrate of the inclination sensor. This treatment significantly increases the porosity of the balsa wood and improves the flexibility of the template; on the other hand, by using the specific structure formed in the balsa wood after treatment, the liquid metal spontaneously forms a differentiated gradient distribution, thereby enhancing the interface response ability of the liquid metal and the detection sensitivity of the electrical signal, and ultimately achieving more excellent detection effect, which is suitable for more application scenarios of liquid metal sensors. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0043] Figure 1 The figure is a schematic diagram of the preparation process of the balsa wood-based liquid metal inclination sensor of the present application, wherein a is the process of balsa wood delignification and liquid metal injection; b is a schematic diagram of the microstructure of balsa wood after delignification; c is a schematic diagram of the liquid metal oxide coating.

[0044] Figure 2 The figure is a detection effect diagram of the liquid metal inclination sensor prepared in Example 1, wherein a is the sensor placed on an electric turntable; b is the change amplitude of the electrical signal of the liquid metal inclination sensor; c is the stability test result; d is the precision and response time test result.

[0045] Figure 3 The detection effect diagram of the liquid metal tilt sensor prepared in Example 2, wherein a is the change amplitude of the sensor electric signal; and b is the stability test result.

[0046] Figure 4 The detection effect diagram of the liquid metal tilt sensor prepared in Example 3, wherein a is the change amplitude of the sensor electric signal; and b is the stability test result.

[0047] Figure 5 The detection effect diagram of the liquid metal tilt sensor prepared in Example 4

[0048] Figure 6 The detection effect diagram of the liquid metal tilt sensor prepared in Comparative Example 1, wherein a is the change amplitude of the sensor electric signal; and b is the stability test result.

[0049] Figure 7 The electric signal change diagram of the liquid metal tilt sensor prepared in Comparative Example 2. DETAILED DESCRIPTION

[0050] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0051] The height of the balsa wood block in the present application refers to the dimension along the axis of the internal microchannel, i.e. the filling direction length of the liquid metal under the driving of capillary force, and is also the distance between the liquid metal injection end and the flow-out end.

[0052] Example 1

[0053] A preparation method of a balsa wood-based liquid metal tilt sensor, comprising the following steps (as shown in Figure 1

[0054] 1) Preparation of a flexible matrix: place the dried balsa wood block (1x1x5cm) into a beaker, immerse the balsa wood block as a whole in sodium hypochlorite solution, the effective chlorine concentration in the system reaches 2wt%, then slowly add dilute acetic acid to adjust the pH to 4.6, and maintain the stirring speed at 200rpm during the reaction. Warm the reaction system to 100℃, and react for 6 hours. After the reaction is completed, quickly cool the system to room temperature, take out the sample, and repeatedly rinse with deionized water until neutral (pH=7), and finally dry at 60℃ to constant weight.

[0055] ​Natural balsa wood is treated with sodium hypochlorite to remove lignin while preserving its three-dimensional vascular network structure, forming a flexible balsa wood matrix with multiple parallel and independent microchannels. Figure 1 b. As can be seen, multiple parallel and independent microchannels are composed of a cellulose skeleton after lignin removal. The microchannels are axially connected along the matrix and radially connected through pits.

[0056] 2) Construction of coating at the outflow end of the substrate: First, place liquid gallium indium alloy in a beaker, with a volume not exceeding two-thirds of the beaker's volume; place the beaker on a mechanical stirrer and insert the stirring head of the stirrer into the liquid metal; start the stirrer and stir continuously at a speed of 400 rpm until the liquid metal gradually undergoes an oxidation reaction and transforms into a paste; stop stirring to obtain a paste-like liquid metal oxide; coat the outflow end of the balsa wood block substrate with a through-hole structure in step 1) with a layer of liquid metal oxide with a thickness of approximately 20–50 μm.

[0057] 3) Injection of liquid metal: At the injection end without a liquid metal oxide coating, liquid metal gallium indium alloy is injected into the three-dimensional conduit network of the balsa wood block obtained in step 2) at a rate of 2 mL / min. Its radially interconnected structure allows the liquid metal to fill the microchannels.

[0058] 4) Coating construction at the substrate injection end: The same liquid metal oxide is coated at the injection end of the flexible substrate to form a liquid metal oxide coating of about 20-50 μm; then silver paste lead-out electrodes are coated at the substrate injection end and the outflow end to obtain the balsa wood-based liquid metal tilt sensor.

[0059] Performance testing: The balsa wood-based liquid metal tilt sensor from Example 1 was placed on an electric turntable. Figure 2 a) and recorded the electrical signal using an Agilent 34420A. Test results show that the electrical signal variation amplitude of this liquid metal tilt sensor is 18% ( Figure 2 b) After the sample was continuously rotated for 60,000 seconds (more than 4,000 cycles), the sensor's electrical signal remained basically stable. Figure 2 c) It exhibits good stability. This sensor has a high angular resolution, reaching 0.5° ( Figure 2 d), and has a fast response speed, with a response time of only 164ms for 1°. Figure 2 e).

[0060] Example 2

[0061] A preparation method of a balsa wood-based liquid metal tilt sensor, the preparation method is the same as that of embodiment 1, the only difference is that the size of the balsa wood is changed: in step 1), the dried wood block (1×1×3cm) is placed in a beaker according to the solid-liquid ratio of 1:15 (g / mL);......Finally, a balsa wood-based liquid metal tilt sensor is obtained.

[0062] Performance test: the balsa wood-based liquid metal tilt sensor of embodiment 2 is placed on an electric rotary table, and an Agilent 34420A is used to record the electrical signal. The test results show that the change range of the electrical signal of the sensor is about 15%( Figure 3 a). The sensor electrical signal remained basically stable( Figure 3 b).

[0063] Embodiment 3

[0064] A preparation method of a balsa wood-based liquid metal tilt sensor, the preparation method is the same as that of embodiment 1, the only difference is that the step 2, the process of coating liquid metal oxide is omitted, and then silver paste is coated on both sides of the substrate to lead out the electrode, finally a tilt sensor is obtained which is not coated with liquid metal oxide and only uses silver paste to seal the end.

[0065] Performance test: the sensor of embodiment 3 is placed on an electric rotary table, and an Agilent 34420A is used to record the electrical signal. The test results show that the change range of the electrical signal of the sensor is 15%( Figure 4 a). The sensor electrical signal appeared slight fluctuations( Figure 4 b). Compared with embodiment 1 which uses liquid metal oxide coating and silver paste for double sealing, the electrical signal change rate and signal stability of the sensor of embodiment 3 are slightly reduced, which further reflects the important role of liquid metal oxide coating in stabilizing the current signal.

[0066] Embodiment 4

[0067] A preparation method of a balsa wood-based liquid metal tilt sensor, the preparation method is the same as that of embodiment 1, the only difference is that the degree of removal of lignin is changed:

[0068] In step 1), the dried balsa wood block (1×1×5cm) is placed in a beaker, sodium hypochlorite solution is added to immerse 3 / 4 of the height of the balsa wood block in the reaction solution, the effective chlorine concentration in the system reaches 2wt%, then dilute acetic acid is slowly added to adjust the pH to 4.6, and the stirring speed is maintained at 200rpm during the reaction. The reaction system is heated to 100℃, and the reaction is carried out for 6 hours. After the reaction is completed, the system is quickly cooled to room temperature, the sample is taken out and washed repeatedly with deionized water until it is neutral (pH=7), and finally dried at 60℃ to constant weight.

[0069] Performance Testing: The balsa wood-based liquid metal tilt sensor from Example 4 was placed on an electric turntable, and its electrical signal was recorded using an Agilent 34420A. Test results showed that the sensor's electrical signal variation amplitude was significantly improved to nearly 20%. Figure 5 After the sample was continuously rotated for 60,000 seconds, the sensor's electrical signal remained essentially stable, demonstrating good stability. This example illustrates that by controlling the degree of delignification, partially removing the lignin, the gradient difference in the capillary channels is increased, making the interface response of the liquid metal more sensitive, increasing the amplitude of the sensor's electrical signal change, and resulting in superior detection performance.

[0070] Comparative Example 1

[0071] A method for preparing a balsa wood-based liquid metal tilt sensor, which, compared with Example 1, omits step 1) the delignin process, ultimately yields a tilt sensor that has not undergone delignin treatment.

[0072] Performance Testing: The sensor from Comparative Example 1 was placed on an electric turntable, and an Agilent 34420A was used to record the electrical signal. Test results showed that the sensor's electrical signal variation was less than 10%. Figure 6 a). After continuously rotating the sample for 28,000 s (approximately 1,900 cycles), the sensor's electrical signal remained relatively stable. However, when the rotation exceeded 30,000 s, the sensor signal exhibited significant fluctuations. Figure 6 b).

[0073] Comparing the data from Example 1 and Comparative Example 1 reveals that: after the balsa wood in Example 1 underwent delignification treatment, its porosity increased, making the surface roughness of the liquid metal more prone to change during rotation, resulting in a corresponding change in the electrical signal and thus a larger amplitude of change in the sensor's electrical signal. In contrast, the lignin in Comparative Example 1 was not removed, and rigid lignin remained in the balsa wood, resulting in lower porosity and therefore less sensitivity for electrical signal detection.

[0074] Comparative Example 2

[0075] A hollow fiber material with a single microchannel is used instead of the balsa wood matrix of this application. Referring to the prior art CN118816938A, gallium indium alloy liquid metal is injected into the hollow fiber material (5cm long * 1cm wide) at a rate of 2mL / min, and then the electrode is led out through silver paste to obtain a liquid metal tilt sensor.

[0076] Performance Testing: The sensor from Comparative Example 2 was placed on an electric turntable, and an Agilent 34420A was used to record the electrical signal. Test results showed that the sensor's electrical signal variation was only 0.8% ( Figure 7), which indicates that the detection range of Comparative Example 2 (a sensor based on a traditional single-channel structure) is significantly lower than the liquid metal sensor based on balsa wood of the present application, and the application scenarios are obviously limited.

[0077] Table 1 Detection results of LMT prepared by examples and comparative examples

[0078]

[0079]

[0080] Specifically, the liquid metal sensor of the present application is based on the synergistic response mechanism of the multi-channel structure, the good bonding performance between the liquid metal oxide interfaces, and the use of renewable biomass resources as the substrate material, thereby exhibiting the following advantages in practical applications:

[0081] 1) High electrical signal change range

[0082] With the synergistic effect of the multi-channel structure, the liquid metal can produce more obvious local roughness change when the angle changes, thereby significantly improving the electrical signal response ability of the sensor. The electrical signal change rates of Examples 1, 2 and 4 are 18.2%, 14.7% and 19.9%, respectively, which are much higher than those of the traditional single-channel design (Comparative Example 1 is 7.9%) and the single-channel hollow fiber substrate scheme (Comparative Example 2 is only 0.8%).

[0083] 2) High resolution

[0084] The detection resolution of the present application reaches 0.5° (Example 1), which is better than the level of more than 1°-2° generally reached by the prior art. This indicates that the sensor can identify and feedback in a more fine angle range, meeting the application requirements of being extremely sensitive to angle changes.

[0085] 3) Excellent fatigue resistance and durability

[0086] Thanks to the flexible structure design, the fatigue resistance of the substrate is better. The durability test results show that Examples 1-4 still maintain stable performance after more than 4000 repeated inclination tests, while Comparative Examples 1 and 2 can only maintain about 1900 and 2000 times of effective use, respectively. This significant difference reflects the innovative advantages of the present application in material selection and structure design, effectively avoiding the performance decline problem caused by mechanical fatigue or material aging.

[0087] 4) Fast response time

[0088] The application has excellent response speed, and the response times of Example 1 and Example 2 are 164 ms and 168 ms respectively, which are significantly better than 300 ms or more of Comparative Example 2. This fast response characteristic enables the sensor to capture angle changes faster and feed back to the control system in time, thereby improving the reaction efficiency and operation stability of the entire system.

[0089] 5) Renewable matrix design

[0090] The application adopts a renewable flexible matrix material, which has good flexibility and conductive performance adaptability, and can meet the stable working demand of the sensor under different deformation conditions. Compared with Comparative Example 2 which adopts a non-renewable matrix material, the application effectively reduces the consumption of material resources while ensuring the performance of the device, improves the recyclability of the material, meets the green environmental protection and sustainable development technology trend, and has good environmental friendliness and industrialization application prospect.

[0091] 6) High service life and wide applicability

[0092] From the service life test results, it can be known that Example 1 and Example 2 can still maintain stable performance output under the condition of continuous work for more than 30 days, and no obvious signal attenuation or functional abnormality occurs; Example 3 can also maintain continuous work for 30 days, and has good stability.

[0093] Therefore, in combination with its excellent performance in high durability, high sensitivity and fast response time, it is shown that the application has good long-term operation stability, can adapt to complex and variable use environment, and has wide application prospect. The application provides an innovative solution with high performance, flexible fitting and sustainability for the fields of aerospace, robot posture control, structure health monitoring and the like.

[0094] The above-described embodiments are merely specific embodiments of the application, which are used to illustrate the technical solutions of the application, rather than limit the same, and the protection scope of the application is not limited thereto. Although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can make modifications or easily think of changes to the technical solutions recorded in the foregoing embodiments within the technical range disclosed by the application, or make equivalent replacements to some technical features; and these modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application, and should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A balsa wood-based liquid metal tilt sensor, characterized in that, include: The balsa wood matrix treated with delignification contains multiple parallel and independent microchannels, which form a three-dimensional network through radially interconnected pits. Gallium-based liquid metal filled within multiple microchannels.

2. The liquid metal tilt sensor according to claim 1, characterized in that, The plurality of parallel and independent microchannels are composed of a cellulose skeleton after lignin removal. The microchannels have a diameter of 10 to 200 μm, are axially connected along the matrix, and are radially connected through pits with a pore size of 0.1 to 10 μm.

3. The liquid metal tilt sensor according to claim 1, characterized in that, The liquid metal is a gallium-based liquid metal, preferably any one or more of gallium metal, gallium-indium alloy, gallium-tin alloy, and indium-gallium-tin alloy.

4. The liquid metal tilt sensor according to claim 1, characterized in that, The tilt sensor further includes a liquid metal oxide coating applied to both ends of the substrate. The thickness of the liquid metal oxide coating is 20-50 μm, and the liquid metal is gallium-based liquid metal. Preferably, the liquid metal oxide coating is further sealed with silver paste.

5. The liquid metal tilt sensor according to claim 1, characterized in that, The degree of lignin removal from the balsamic matrix is ​​75-100%.

6. The method for preparing the balsa wood-based liquid metal tilt sensor according to any one of claims 1 to 5, characterized in that, Includes the following steps: 1) Preparation of flexible matrix: Natural balsa wood is treated with delignification to retain its three-dimensional vascular network structure, forming a flexible balsa wood matrix with multiple parallel and independent microchannels; 2) Coating construction at the outflow end of the substrate: Liquid metal oxide is coated at the outflow end of the flexible substrate to form a liquid metal oxide coating; 3) Liquid metal injection: Liquid metal is injected into the three-dimensional conduit network at the injection end of the flexible substrate to fill the microchannels; 4) Coating construction at the substrate injection end: Liquid metal oxide is coated at the injection end of the flexible substrate to form a liquid metal oxide coating; then conductive silver paste is coated at the injection end and the outflow end of the substrate and electrodes are led out to obtain the balsa wood-based liquid metal tilt sensor.

7. The preparation method according to claim 6, characterized in that, In step 1), the delignification treatment is performed using either the sodium hypochlorite method or the alkaline hydrogen peroxide method.

8. The preparation method according to claim 6, characterized in that, The sodium hypochlorite method for delignification includes the following steps: The dried balsa wood was immersed in a reaction solution containing sodium hypochlorite, with an effective chlorine concentration of 1.5–3 wt%. Acid was added to adjust the pH of the system to 4–5, and the reaction was carried out at 90–110 °C and 100–500 rpm for 2–8 hours. After the reaction was completed, the wood was cooled to room temperature, rinsed until neutral, and dried at 50–70 °C to constant weight.

9. The preparation method according to claim 6, characterized in that, In steps 2) and 4), the method for preparing the liquid metal oxide coating is to continuously stir the liquid metal at a speed of 200 to 700 rpm until it undergoes an oxidation reaction to form a paste-like oxide coating. In step 3), the injection rate of the liquid metal is 1–5 mL / min; In step 1), the dried balsa wood is immersed entirely in a reaction solution containing sodium hypochlorite; or 3 / 4 of the height of the dried balsa wood is immersed in a reaction solution containing sodium hypochlorite.

10. The application of the balsa wood-based liquid metal sensor according to any one of claims 1 to 5 or the balsa wood-based liquid metal tilt sensor obtained by the preparation method according to any one of claims 6 to 9 in angle detection.

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