A self-sensing cellulose nanocrystal-based flexible actuator and its preparation method

Abstract

This invention relates to an electroactive ionic polymer material, aiming to provide a self-sensing cellulose nanofiber-based flexible actuator and its preparation method. The actuator should possess self-sensing functionality, thereby eliminating the need for a feedback source outside the actuator, reducing production costs, and featuring simple operation and ease of promotion. The technical solution is a self-sensing cellulose nanofiber-based flexible actuator, characterized in that: two grooves are formed on each of the front and back surfaces of the actuator, the two grooves are arranged at a distance from each other, and the bottom of the grooves extends to the cellulose nanofiber-ionic liquid biocomposite membrane in the actuator. The two grooves also surround the edges of the other three sides (excluding the metal electrode side) and penetrate the edge of the metal electrode side, thus forming independent shielding electrodes and sensors in three directions around the actuator.

Description

Technical Field

[0001] This invention relates to an electroactive ionic polymer material, specifically to a self-sensing cellulose nanofiber-based flexible actuator and its preparation method. Background Technology

[0002] Electroactive polymer actuators offer significant advantages due to their low driving voltage, minimal mechanical deformation, lightweight, flexibility, fast response time, and wide frequency bandwidth. Based on these key characteristics, electroactive polymer actuators can be applied to active medical devices, soft robots, wearable electronic devices, flexible displays, and surgical instruments. However, the electrolyte membranes of these electroactive polymer actuators are primarily based on non-biological membrane materials, including polyvinylidene fluoride (PVDF) and perfluorosulfonic acid-polytetrafluoroethylene (PTFE) copolymers. These materials suffer from drawbacks such as high cost, complex manufacturing processes, and low actuation performance, hindering their use in human-friendly fields, including health monitoring, wearable electronic devices, and soft haptic devices.

[0003] Cellulose is a natural polymer with renewable, environmentally friendly, biocompatible, and biodegradable properties, making it a potential base material for electroactive polymer actuators. Subsequently, cellulose-based actuators have been extensively studied. However, these cellulose-based ion actuators still exhibit low actuation performance for next-generation soft robots and bioelectronics due to their relatively low electrochemical properties.

[0004] When using electroactive polymer actuators, real-time feedback of the actuator's deformation is typically required to facilitate closed-loop control of the system. However, the need for an external feedback source for the actuator increases the cost and complexity of the overall system design, hindering the application of electroactive polymer actuators. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology and provide a self-sensing cellulose nanofiber-based flexible actuator and its preparation method; the actuator should have a self-sensing function, thereby eliminating the need for a feedback source outside the actuator, reducing production costs, and having the characteristics of simple operation and easy promotion.

[0006] The technical solution provided by this invention is:

[0007] A self-sensing cellulose nanofiber-based flexible actuator includes a thin strip or sheet-like cellulose nanofiber-ionic liquid ionic electroactive actuator and a metal electrode connected to one side of the actuator along its length. The actuator has two grooves on its front and back sides, the two grooves being spaced apart and the bottom of the grooves extending to the cellulose nanofiber-ionic liquid biocomposite membrane within the actuator. The two grooves also surround the edges of the other three sides (excluding the metal electrode side) and penetrate the edge of the metal electrode side, thus forming independent shielding electrodes and sensors in three directions around the actuator.

[0008] The grooves are arranged correspondingly on the front and back sides of the driver.

[0009] A method for preparing a self-sensing cellulose nanocrystal-based flexible actuator is carried out according to the following steps:

[0010] 1) Preparation of cellulose nanocrystal ion-type electroactive actuators

[0011] 2) Fabrication of patterned electrodes for ion-driven electroactive actuators using cellulose nanocrystals

[0012] 2.1) Place the ion-type electroactive actuator of cellulose nanocrystals inside the excimer laser;

[0013] 2.2) Input the pattern and set the laser pulse energy and repetition frequency of the excimer laser;

[0014] 2.3) Electrodes of the corresponding shape are fabricated by evaporating the driver electrodes using a pulsed excimer laser;

[0015] 2.4) The patterned cellulose nanowhisker ionic electroactive actuator was cooled at room temperature and its pattern was checked for compliance, finally obtaining the cellulose nanowhisker patterned electrode actuator.

[0016] In step 2.2), the pulse energy of the KrF excimer laser is 9–11 mJ; the laser pulse frequency used is set to 7–10 Hz.

[0017] In step 2.2), the driver stage in the patterning process moves at 0.2 mm / s. -1 It moves at a constant speed.

[0018] Step 1) involves preparing cellulose nanofiber ion-active actuators, which is performed according to the following steps:

[0019] (1) Preparation of cellulose nanofiber-ionic liquid biocomposite membrane

[0020] (1.1) Ionic liquid, cellulose nanocrystal suspension and deionized water were mixed, stirred at room temperature and ultrasonically treated to obtain a stable and uniform cellulose nanocrystal-ionic liquid dispersion.

[0021] (1.2) Removing air bubbles from the cellulose nanocrystal-ionic liquid dispersion under vacuum;

[0022] (1.3) Pour the bubble-free dispersion into a mold and dry it in a vacuum drying oven to obtain a cellulose nanofiber-ionic liquid biocomposite membrane.

[0023] 2) Preparation of cellulose nanocrystal-ionic liquid ionic electroactive actuators

[0024] (2.1) The prepared cellulose nanocrystal-ionic liquid biocomposite membrane was cut into thin strips;

[0025] (2.2) The fine strip-shaped cellulose nanofiber-ionic liquid biocomposite membrane was immersed in PEDOT:PSS solution repeatedly to ensure full adhesion;

[0026] (2.3) The cellulose nanofiber-ionic liquid biocomposite membrane with PEDOT:PSS solution attached was placed in a vacuum drying oven for preliminary drying;

[0027] (2.4) The preliminarily dried cellulose nanocrystal-ionic liquid biocomposite membrane was placed at room temperature for thorough drying; then the metal electrode was set according to conventional methods to finally obtain the cellulose nanocrystal-ionic liquid ionic electroactive actuator.

[0028] In step (1.1), the concentration of the cellulose nanofiber suspension is 6.6-7.00 wt%, and the ionic liquid is a 98% 1-ethyl-3-methylimidazolium tetrafluoroborate solution.

[0029] In step (1.1), the weight ratio of cellulose nanocrystal suspension, ionic liquid and deionized water is 15-16:0.5-0.6:40-50, and the mixing temperature is 20-30℃.

[0030] The stirring time at room temperature in step (1.1) is 4 to 6 hours.

[0031] In the ultrasonic treatment of step (1.1), the power of the ultrasonic oscillation is 50W and the treatment time is 5 to 15 minutes.

[0032] In step (1.2), the process of removing air bubbles by vacuum is carried out in a vacuum drying oven, and the vacuum drying oven is evacuated 3 to 5 times consecutively, with an interval of 5 minutes between each evacuation, and each evacuation lasts for 10 to 15 minutes.

[0033] In step (1.2), the drying temperature in the vacuum drying oven is 55-65℃ and the drying time is 4-6h.

[0034] In step (2.1), the composite film is cut into thin strips of 10mm × 40mm.

[0035] In step (2.2), in the PEDOT:PSS solution, PEDOT is a polymer of 3,4-ethylenedioxythiophene monomer, PSS is sodium alginate, the weight ratio of PEDOT to PSS is 6:8, the solvent is deionized water, the solution concentration is 1.3%-2.0%, the immersion time is 5-10 min, and it is repeated 5-7 times.

[0036] In step (2.3), the drying temperature in the vacuum drying oven is 45-55℃ and the drying time is 4-6h.

[0037] In step (2.4), the drying time at room temperature is 4 to 6 hours.

[0038] The beneficial effects of this invention are:

[0039] 1. Electrode patterning on the surface of a cellulose nanocrystal-based flexible actuator forms individual electrically isolated sensing elements. The introduced patterned layout enables the actuator to obtain displacement by monitoring the electrical signals of the sensing elements during its duty cycle, without any additional feedback system. This achieves closed-loop control in a highly compact manner without limiting the actuator's applicability.

[0040] 2. Cellulose is a natural polymer that is renewable, environmentally friendly, biocompatible, and biodegradable. It is inexpensive, readily available, reliable, and environmentally friendly, making it a suitable material for electroactive polymer actuators. This invention utilizes cellulose nanowhiskers, needle-like nanomaterials obtained by carboxylation modification of natural plant cellulose. Compared to other cellulose materials, cellulose nanowhiskers exhibit higher water-holding capacity and higher crystallinity. This is because the carboxylation process results in abundant hydroxyl groups within the cellulose nanowhiskers. The internal fibers are tightly entangled and interwoven under van der Waals and hydrogen bonds, forming an ultrafine network structure, thus giving the cellulose nanowhiskers higher mechanical strength and elastic modulus. Furthermore, the high aspect ratio (diameter 5-50 nm, length 100-3000 nm) and large specific surface area of ​​cellulose nanowhiskers significantly enhance their affinity for cellulose with ionic liquids and other active substances.

[0041] 3. The preparation method of the intermediate layer of the biocomposite membrane of the present invention is a simple solution casting method. The preparation method and process conditions are simple. Vacuum drying is used to remove air bubbles in the ion exchange membrane, so that the components in the final ion exchange membrane are evenly distributed. It has the advantages of stable operation, superior performance, simple operation and easy promotion.

[0042] 4. This invention uses PEDOT:PSS material as electrode material, which has the advantages of high conductivity, good thermal stability and strong adhesion, and significantly improves the disadvantages of traditional electroactive polymer actuator electrode materials, such as high price and easy breakage.

[0043] 5. This invention prepared an ionic electroactive polymer with superior comprehensive performance, and designed an actuator based on it. The designed cellulose nanowhiskers-ionic liquid ionic electroactive actuator exhibited a bending displacement of 7.60 mm (sinusoidal input voltage of 1.5 V, excitation frequency of 0.1 Hz), good driving persistence (98% of the bending displacement after 2 hours), and a relatively wide frequency bandwidth. Under a sinusoidal input voltage of 0.1 Hz ± 1.5 V, the bending strain reached as high as 0.32%, mainly due to its relatively large specific capacitance (115.2 mF / cm). -2 ) and tuned machinery. This material is beneficial for use as a "green" electronic device, such as wearable devices and biomedical devices.

[0044] 6. The most significant advantage of using lasers to pattern ionic electroactive actuators for cellulose nanocrystals is that electrodes can be removed simultaneously from both sides of the sample without damaging the intermediate biocomposite membrane. Furthermore, compared to machine milling or manual scraping, laser ablation provides better precision and finer patterns with high repeatability, laying the foundation for future commercialization. Attached Figure Description

[0045] Figure 1 This is a surface SEM image of the cellulose nanocrystal-ionic liquid composite film in an embodiment of the present invention.

[0046] Figure 2 This is an example diagram of the deformation state of the cellulose nanocrystal-ionic liquid ionic electroactive actuator under a sinusoidal input voltage of 0.1Hz±1.5V in an embodiment of the present invention.

[0047] Figure 3 This is an example diagram of the patterning of cellulose nanocrystal ion-type electroactive actuators in an embodiment of the present invention.

[0048] Figure 4 This embodiment of the invention illustrates the relationship between the displacement of the cellulose nanocrystal-ionic liquid ionic electroactive actuator and the sensing voltage at a voltage of 1V and a frequency of 1Hz. Detailed Implementation

[0049] When using electroactive polymer actuators, real-time feedback is typically required. This helps determine the actuator's position and state, enabling closed-loop control of the system. Due to the repeatability and reproducibility issues inherent in the electromechanical processes of electroactive polymer actuators, real-time feedback is valuable for reliable applications. The most commonly used feedback systems include laser displacement sensors, load cells, and cameras, although the use of individual electroactive polymer actuator strips as deformation sensors or other sensors has also been proposed. However, the need for an external feedback source for the actuator increases the cost and complexity of the overall system design, hindering the adoption of electroactive polymer actuators.

[0050] In its natural state, the anions and cations in the actuator are uniformly distributed within the ion exchange membrane, making it electrically neutral overall and non-polar. However, when subjected to bending deformation by external force, one side of the actuator contracts while the other extends, resulting in a higher ion concentration on the compressed side compared to the extended side. To balance the internal ion concentration, both anions and cations on the compressed side migrate towards the extended side. Since EMIM+ has a larger volume than BF4–, more cations migrate to the stretched side, causing an imbalance in the charge distribution within the ion exchange membrane relative to the neutral layer. This leads to the accumulation of charge and a potential difference across the entire actuator surface. According to the sensing mechanism, the voltage signal originates entirely from the migration and accumulation of ions during the deformation process. Therefore, the actuator can achieve sensing functionality (self-sensing function) without an external power source. Furthermore, because ion migration is directional, the direction of deformation can be determined by detecting the sign of the induced electrical signal on the actuator surface.

[0051] Self-induction refers to a single electroactive polymer material simultaneously acting as both an actuator and a sensor, allowing the sensed signal to be used for closed-loop control of a device. The tight integration of sensing and actuation functions exhibited by biological systems has been a source of inspiration for research on smart materials and devices, driving the development of fundamental research and applications in sensing and actuation. The motivation for creating self-induction actuators is to achieve closed-loop control in a highly compact manner, without limiting the applicability of the actuator, enabling it to achieve the effect of sensing its own actuated displacement without the need for additional devices. Since cellulose-based actuators also exhibit electromechanical sensor behavior, combining the actuation and sensing functions of a single device to create a self-induction actuator is advantageous.

[0052] The following description, in conjunction with the embodiments shown in the accompanying drawings, provides further details.

[0053] Principle analysis of the invention:

[0054] The actuator provided by this invention is an ultra-low voltage, high-performance ion actuator based on cellulose nanocrystals (CCNC), ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate solution), and poly(3,4-ethylenedioxythiophene)poly(styrene sulfonate) (PEDOT: PSS) (see CN115368611A).

[0055] (1) Driving principle

[0056] The actuator based on cellulose nanocrystals has a three-layer structure, with two layers being PEDOT:PSS electrode layers and the middle layer being a cellulose nanocrystal-ionic liquid membrane (see [link]). Figure 1 The driving mechanism of the polymer actuator is termed a doping-dedoping process based on an electrochemical redox reaction. After applying a driving voltage to the PEDOT:PSS electrode layer, anions (small ions, BF4-) and cations (large ions, EMIM+) in the cellulose nanofiber electrolyte membrane migrate towards the anode and cation sides, respectively. The accumulation of anions and cations near the cathode layer leads to a relative volume difference, causing the ion actuator to bend and deform towards the anode, thus inducing a bending yaw of the actuator (see [link to relevant documentation]). Figure 2 This enables it to drive under voltage.

[0057] (2) Sensing principle

[0058] In its natural state, the anions and cations in the actuator are uniformly distributed within the ion exchange membrane, making it electrically neutral overall and non-polar. However, when subjected to bending deformation by external force, one side of the actuator contracts while the other extends, resulting in a higher ion concentration on the compressed side compared to the extended side. To balance the internal ion concentration, both anions and cations on the compressed side migrate towards the extended side. Since EMIM+ has a larger volume than BF4–, more cations migrate to the stretched side, causing an imbalance in the charge distribution within the ion exchange membrane relative to the neutral layer. This leads to the accumulation of charge and a potential difference across the entire actuator surface. According to the sensing mechanism, the voltage signal originates entirely from the migration and accumulation of ions during the deformation process, thus enabling the actuator to perform sensing functions without an external power source. Furthermore, because ion migration is directional, the direction of deformation can be determined by detecting the sign of the induced electrical signal on the actuator surface.

[0059] (3) Patterned electrodes realize the self-inductance principle

[0060] Actuators for patterned cellulose nanocrystals, with electrode surface patterns such as... Figure 3As shown, it consists of three independent (i.e., mutually insulated) parts: a driving part (i.e., the driver), a shielding electrode for reducing crosstalk (which needs to be grounded during use), and a sensing electrode (i.e., the sensor). These three independent parts are separated by grooves formed by laser ablation. The depth of the grooves needs to reach the cellulose nanofiber-ionic liquid biocomposite membrane (i.e., removing the residual layer of dried PEDOT:PSS solution through laser ablation). The width of the grooves can be determined as needed (0.5-1 mm recommended); the width of the shielding electrode and the sensor can also be determined as needed (0.5-1 mm recommended for the shielding electrode; 1.0-2.0 mm recommended for the sensor). All electrodes are connected to electrode terminals from the same end of the strip for easy external electrical connection. The driver is equipped with metal electrodes (preferably copper sheet electrodes) to connect to the power supply voltage and is responsible for bending the entire system. The two sensor electrodes located on opposite surfaces of the strip bend synchronously with the driver. The sensing voltage of the sensor electrodes is measured at the output end; the driving displacement of the driver can be obtained by measuring the change in the sensing voltage. The shielded electrode connected to the circuit's common ground eliminates crosstalk between the driver and the sensor.

[0061] Example 1

[0062] A method for preparing an ionic electroactive actuator based on cellulose nanowhiskers is carried out as follows:

[0063] 1) Preparation of cellulose nanocrystal-ionic liquid biocomposite membrane

[0064] 1.1) Mix 15g of cellulose nanocrystal suspension (concentration of 6.6wt%) with 0.5g of ionic liquid (concentration of 98%) and 40g of deionized water. Mix and stir at 20℃ for 4h, and then sonicate for 5min (power of ultrasonic oscillation of 50W) to obtain a stable and uniform cellulose nanocrystal-ionic liquid dispersion.

[0065] 1.2) Remove air bubbles from the cellulose nanocrystal-ionic liquid dispersion in a vacuum drying oven. Perform vacuuming three times consecutively, each time for 15 minutes, with a 5-minute interval between each time.

[0066] 1.3) Pour the bubble-free dispersion into a mold and dry it in a vacuum drying oven at 55°C for 6 hours to obtain a cellulose nanofiber-ionic liquid biocomposite membrane with a thickness of 0.45 mm.

[0067] 2) Preparation of cellulose nanocrystal-ionic liquid ionic electroactive actuators

[0068] 2.1) Cut the prepared cellulose nanofiber-ionic liquid composite membrane into thin strips of 10mm × 40mm;

[0069] 2.2) The fine cellulose nanofiber-ionic liquid composite membrane was immersed in a PEDOT:PSS solution (PEDOT is a polymer of 3,4-ethylenedioxythiophene monomer, PSS is sodium alginate, the weight ratio of PEDOT to PSS is 6:8, and the solution concentration is 1.3%) for 5 min, and the immersion time was repeated 7 times.

[0070] 2.3) The cellulose nanofiber-ionic liquid composite film with PEDOT:PSS solution attached was placed in a vacuum drying oven for preliminary drying at 55℃ for 4 hours.

[0071] 2.4) The preliminarily dried cellulose nanofiber-ionic liquid composite membrane was placed at room temperature (27°C) and dried for 4 hours to ensure it was fully dried. Then, two electrodes were set up according to conventional methods to finally obtain the cellulose nanofiber-ionic liquid ionic electroactive actuator.

[0072] 3) Fabrication of patterned electrodes for ion-driven electroactive actuators using cellulose nanocrystals

[0073] 3.1) Place the ion-type electroactive actuator of cellulose nanocrystals inside the excimer laser.

[0074] 3.2) Input the patterning track gauge. The KrF excimer laser pulse energy is 9 mJ. The laser pulse frequency used is set to 10 Hz. During the patterning process, the driver stage is positioned at a speed of 0.2 mm / s. -1 It moves at a constant speed.

[0075] 3.3) Electrodes of corresponding shapes are fabricated by evaporating the driver electrodes using a pulsed excimer laser.

[0076] 3.4) The patterned cellulose nanowhisker ionic electroactive actuator was cooled at room temperature and its pattern was checked for compliance, finally obtaining the cellulose nanowhisker patterned electrode actuator.

[0077] Example 2

[0078] A method for preparing an ionic electroactive actuator based on cellulose nanowhiskers is carried out as follows:

[0079] 1) Preparation of cellulose nanocrystal-ionic liquid biocomposite membrane

[0080] 1.1) 16g of cellulose nanocrystal suspension (concentration of 6.66wt%) and 0.5g of ionic liquid (concentration of 98%) were mixed with 45g of deionized water and stirred at 30℃ for 5h. The mixture was then sonicated for 10min (ultrasonic oscillation power of 50W) to obtain a stable and uniform cellulose nanocrystal-ionic liquid dispersion.

[0081] 1.2) Remove air bubbles from the cellulose nanocrystal-ionic liquid dispersion in a vacuum drying oven. Perform vacuuming four times consecutively, each time for 15 minutes, with a 5-minute interval between each time.

[0082] 1.3) Pour the bubble-free dispersion into a mold and dry it in a vacuum drying oven at 60°C for 5 hours to obtain a cellulose nanofiber whisker-ionic liquid biocomposite membrane with a thickness of 0.45 mm.

[0083] 2) Preparation of cellulose nanocrystal-ionic liquid ionic electroactive actuators

[0084] 2.1) Cut the prepared cellulose nanofiber-ionic liquid composite membrane into thin strips of 10mm × 40mm;

[0085] 2.2) The fine cellulose nanofiber-ionic liquid composite membrane was immersed in a PEDOT:PSS solution (PEDOT is a polymer of 3,4-ethylenedioxythiophene monomer, PSS is sodium alginate, the weight ratio of PEDOT to PSS is 6:8, and the solution concentration is 1.5%) for 6 minutes, and the immersion time was repeated 6 times.

[0086] 2.3) The cellulose nanofiber-ionic liquid composite membrane with PEDOT:PSS solution attached was placed in a vacuum drying oven for initial drying; then, two electrodes were set up according to conventional methods, the drying temperature was 50℃, and the drying time was 5h.

[0087] 2.4) The preliminarily dried cellulose nanofiber-ionic liquid composite membrane was placed at room temperature (26°C) and dried for 5 hours to ensure it was fully dried, thus obtaining the cellulose nanofiber-ionic liquid ionic electroactive actuator.

[0088] 3) Fabrication of patterned electrodes for ion-driven electroactive actuators using cellulose nanocrystals

[0089] 3.1) Place the ion-type electroactive actuator of cellulose nanocrystals inside the excimer laser.

[0090] 3.2) Input the patterning track distance. The KrF excimer laser pulse energy is 10 mJ. The laser pulse frequency used is set to 9 Hz. During the patterning process, the driver stage is positioned at a speed of 0.2 mm / s. -1 It moves at a constant speed.

[0091] 3.3) Electrodes of corresponding shapes are fabricated by evaporating the driver electrodes using a pulsed excimer laser.

[0092] 3.4) The patterned cellulose nanowhisker ionic electroactive actuator was cooled at room temperature and its pattern was checked for compliance, finally obtaining the cellulose nanowhisker patterned electrode actuator.

[0093] Example 3

[0094] A method for preparing an ionic electroactive actuator based on cellulose nanowhiskers is carried out as follows:

[0095] 1) Preparation of cellulose nanocrystal-ionic liquid biocomposite membrane

[0096] 1.1) Mix 15g of cellulose nanofiber suspension (7wt%) with 0.6g of ionic liquid (98%) and 50g of deionized water. Stir at 25℃ for 5h and sonicate for 15min (ultrasonic power of 50W) to obtain a stable and uniform cellulose nanofiber-ionic liquid dispersion.

[0097] 1.2) Remove air bubbles from the cellulose nanocrystal-ionic liquid dispersion in a vacuum drying oven. Perform vacuuming five times in a row, each time for 14 minutes, with a 5-minute interval between each time.

[0098] 1.3) Pour the bubble-free dispersion into a mold and dry it in a vacuum drying oven at 65°C for 4 hours to obtain a cellulose nanofiber whisker-ionic liquid biocomposite membrane with a thickness of 0.45 mm.

[0099] 2) Preparation of cellulose nanocrystal-ionic liquid ionic electroactive actuators

[0100] 2.1) Cut the prepared cellulose nanofiber-ionic liquid composite membrane into thin strips of 10mm × 40mm;

[0101] 2.2) The fine cellulose nanofiber-ionic liquid composite membrane was immersed in a PEDOT:PSS solution (PEDOT is a polymer of 3,4-ethylenedioxythiophene monomer, PSS is sodium alginate, the weight ratio of PEDOT to PSS is 6:8, and the solution concentration is 2%) for 10 min, and the immersion time was repeated 5 times.

[0102] 2.3) The cellulose nanofiber-ionic liquid composite membrane with PEDOT:PSS solution attached was placed in a vacuum drying oven for preliminary drying at 45℃ for 6 hours.

[0103] 2.4) The preliminarily dried cellulose nanocrystal-ionic liquid composite membrane was placed at room temperature (25°C) and dried for 6 hours to ensure it was fully dried. Then, two electrodes were set up according to conventional methods to finally obtain the cellulose nanocrystal-ionic liquid ionic electroactive actuator.

[0104] 3) Fabrication of patterned electrodes for ion-driven electroactive actuators using cellulose nanocrystals

[0105] 3.1) Place the ion-type electroactive actuator of cellulose nanocrystals inside the excimer laser.

[0106] 3.2) Input the patterning track gauge. The KrF excimer laser pulse energy is 11 mJ. The laser pulse frequency used is set to 7 Hz. During the patterning process, the placement driver stage moves at a constant speed of 0.2 mm s⁻¹.

[0107] 3.3) Electrodes of corresponding shapes are fabricated by evaporating the driver electrodes using a pulsed excimer laser.

[0108] 3.4) The patterned cellulose nanowhisker ionic electroactive actuator was cooled at room temperature and its pattern was checked for compliance, finally obtaining the cellulose nanowhisker patterned electrode actuator.

[0109] Performance testing

[0110] 1. Response Testing

[0111] The test examples obtained the excitation response of the ion-type electroactive actuator based on cellulose nanocrystals under a sinusoidal input voltage of 0.1Hz ± 1.5V. The test results are as follows: Figure 2 As shown.

[0112] The ion-type electroactive actuator based on cellulose nanowhiskers obtained in this invention exhibits excellent actuation performance attributed to its adjusted mechanical properties, large specific capacitance, and strong ionic interactions between the cellulose nanowhiskers and the ionic liquid. Another reason for the improved actuation performance is the electrochemical doping process of the PEDOT:PSS electrode layer. Anions and cations migrate from the cellulose nanowhisker matrix into the PEDOT:PSS electrode layer, inducing an electrochemical doping process that leads to enhanced bending displacement. Therefore, the actuator's actuation mechanism is a result of the synergistic effect of ion movement within the film and the electrochemical doping process of the PEDOT:PSS electrode layer under applied voltage, resulting in a high-performance and stable actuator.

[0113] 2. Self-induction test

[0114] Actuators for patterned cellulose nanocrystals, with electrode surface patterns such as... Figure 3As shown, it consists of three independent parts: a driving function part (i.e., the driver), a shielding electrode for reducing crosstalk, and a sensing element (i.e., the sensor). The driver port is connected to the input voltage. Two sensor electrodes located on opposite sides of the strip bend synchronously with the driver. The sensing voltage of the sensor electrodes is measured at the two output terminals, and the driving displacement of the driver can be determined by measuring the change in sensing voltage.

[0115] When the input voltage frequency is 1Hz and the amplitude of the sinusoidal voltage is 1V, the relationship between the driver displacement and the sensed voltage is as follows: Figure 4 As shown, it is clear that the output sensing voltage of the ionic electroactive actuator of cellulose nanocrystals is positively correlated with the displacement of the actuator as the end displacement changes.

[0116] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to describe its nature. Although the present invention has been described in detail with reference to the examples, those who have the same knowledge in the technical field of the present invention can modify and change the technical ideas of the present invention in various forms, and all of them should be covered within the scope of the claims of the present invention.

Claims

1. A self-sensing cellulose nanofiber-based flexible actuator, comprising a thin strip or sheet-like cellulose nanofiber-ionic liquid ionic electroactive actuator and a metal electrode connected to one side of the actuator along its length, characterized in that: The actuator has two grooves on its front and back sides, which are arranged at a distance from each other and the bottom of the grooves extends to the cellulose nanofiber-ionic liquid biocomposite membrane in the actuator. The two grooves also surround the edges of the other three sides except the metal electrode side and penetrate the edge of the metal electrode side, thereby forming independent shielding electrodes and sensors in three directions around the actuator. The grooves are arranged correspondingly on the front and back sides of the driver; The preparation method of the self-sensing cellulose nanofiber-based flexible actuator is carried out according to the following steps: 1) Preparation of cellulose nanocrystal ion-type electroactive actuators; 2) Fabrication of patterned electrodes for ion-driven electroactive actuators using cellulose nanocrystals; 2.1) Place the ion-type electroactive actuator of cellulose nanocrystals inside the excimer laser; 2.2) Input the pattern and set the laser pulse energy and repetition frequency of the excimer laser; 2.3) Electrodes of the corresponding shape are fabricated by evaporating the driver electrode using a pulsed excimer laser; 2.4) The patterned cellulose nanowhisker ionic electroactive actuator was cooled at room temperature and its pattern was checked for compliance, and finally the cellulose nanowhisker patterned electrode actuator was obtained. In step 2.2), the KrF excimer laser pulse energy is 9–11 mJ; the laser pulse frequency used is set to 7–10 Hz. In step 2.2), the driver stage in the mapping process moves at 0.2 mm / s. −1 Moving at a constant speed; Step 1) involves preparing cellulose nanofiber ion-active actuators, which is performed according to the following steps: (1) Preparation of cellulose nanocrystal-ionic liquid biocomposite membrane (1.1) Mix the ionic liquid, cellulose nanocrystal suspension and deionized water, stir at room temperature and sonicate to obtain a stable and uniform cellulose nanocrystal-ionic liquid dispersion. (1.2) Removing air bubbles from the cellulose nanocrystal-ionic liquid dispersion under vacuum; (1.3) Pour the bubble-free dispersion into a mold and dry it in a vacuum drying oven to obtain a cellulose nanofiber-ionic liquid biocomposite membrane; 2) Preparation of cellulose nanocrystal-ionic liquid ionic electroactive actuators (2.1) Cut the prepared cellulose nanocrystal-ionic liquid biocomposite membrane into thin strips; (2.2) The fine strip-shaped cellulose nanofiber-ionic liquid biocomposite membrane was immersed in PEDOT:PSS solution repeatedly to ensure full adhesion; (2.3) The cellulose nanofiber-ionic liquid biocomposite membrane with PEDOT:PSS solution attached was placed in a vacuum drying oven for preliminary drying; (2.4) The preliminarily dried cellulose nanocrystal-ionic liquid biocomposite membrane was placed at room temperature for thorough drying; then the metal electrode was set according to conventional methods to finally obtain the cellulose nanocrystal-ionic liquid ionic electroactive actuator.

2. The method for preparing the self-sensing cellulose nanocrystal-based flexible actuator according to claim 1, characterized in that: In step (1.1), the concentration of the cellulose nanofiber suspension is 6.6-7.00 wt%, and the ionic liquid is a 98% 1-ethyl-3-methylimidazolium tetrafluoroborate solution. In step (1.1), the weight ratio of cellulose nanofiber suspension, ionic liquid and deionized water is 15-16:0.5-0.6:40-50, and the mixing temperature is 20-30℃. In step (1.1), the stirring time at room temperature is 4–6 hours; In the ultrasonic treatment in step (1.1), the power of the ultrasonic oscillation is 50W and the treatment time is 5 to 15 minutes.

3. The method for preparing the self-sensing cellulose nanocrystal-based flexible actuator according to claim 2, characterized in that: In step (1.2), the process of removing air bubbles by vacuum is carried out in a vacuum drying oven, and the vacuum drying oven is evacuated 3 to 5 times consecutively, with an interval of 5 minutes between each evacuation, and each evacuation lasts for 10 to 15 minutes. In step (1.2), the drying temperature in the vacuum drying oven is 55-65℃ and the drying time is 4-6h.

4. The method for preparing the self-sensing cellulose nanocrystal-based flexible actuator according to claim 3, characterized in that: In step (2.1), the composite film is cut into thin strips of 10mm × 40mm; In step (2.2), the PEDOT:PSS solution contains PEDOT, which is a polymer of 3,4-ethylenedioxythiophene monomer, and PSS, which is sodium alginate. The weight ratio of PEDOT to PSS is 6:

8. The solvent is deionized water, the solution concentration is 1.3%-2.0%, the immersion time is 5-10 minutes, and the process is repeated 5-7 times.

5. The self-sensing cellulose nanocrystal-based flexible actuator according to claim 4, characterized in that: In step (2.3), the drying temperature in the vacuum drying oven is 45-55℃, and the drying time is 4-6 hours. In step (2.4), the drying time at room temperature is 4 to 6 hours.

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