SILK FIBROIN-BASED MULTI-RESPONSIVE SOFT ACTUATOR, MANUFACTURING METHOD AND REGULATION AND CONTROL METHOD

Abstract

A silk fibroin-based multi-responsive soft actuator and a manufacturing method therefor are provided. The soft actuator includes a silk fibroin membrane and a flexible substrate, the silk fibroin membrane being arranged on and tightly bonded with the flexible substrate to form a double-layer membrane structure, thermal expansion coefficients of the silk fibroin membrane and the flexible substrate being different. The manufacturing method for a soft actuator includes: performing plasma processing on a flexible substrate; then scrap-coating the flexible substrate with a silk fibroin wet membrane, drying same to obtain a silk fibroin membrane, the silk fibroin membrane together with the flexible substrate forming a double-layer membrane; soaking the double-layer membrane into water, and then drying same; and integrally or locally soaking in a calcium chloride aqueous solution the silk fibroin membrane in the dried double-layer membrane, then taking out same, and drying same to obtain a soft actuator.

Claims

1. A silk fibroin-based multi-responsive soft actuator, wherein the soft actuator comprises a silk fibroin membrane and a flexible substrate, wherein the silk fibroin membrane is placed on the flexible substrate and tightly bonded thereto to constitute a double-layer membrane structure, wherein thermal expansion coefficients of the silk fibroin membrane and the flexible substrate are different.

2. The silk fibroin-based multi-responsive soft actuator according to claim 1, wherein a thermal expansion coefficient of the silk fibroin membrane is negative.

3. A regulation and control method applied to the multi-responsive soft actuator according to claim 1, wherein the soft actuator is heated, causing the silk fibroin membrane and the flexible substrate to undergo different thermal deformations, making the double-layer membrane structure bend and deform towards a side where the silk fibroin membrane is located.

4. The regulation and control method according to claim 3, wherein by adjusting whether the silk fibroin membrane in the double-layer membrane after drying is soaked in the calcium chloride aqueous solution or a concentration of the calcium chloride aqueous solution in which the silk fibroin membrane is soaked during the manufacturing process, a deformation angle, an amplitude and a morphology of the multi-responsive soft actuator are regulated and controlled.

5. A regulation and control method applied to the multi-responsive soft actuator according to claim 2, wherein the soft actuator is heated, causing the silk fibroin membrane and the flexible substrate to undergo different thermal deformations, making the double-layer membrane structure bend and deform towards a side where the silk fibroin membrane is located.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a schematic diagram of the structure of a soft actuator with a double-layer membrane structure.

[0032] FIG. 2 shows the deformation state of the soft actuator of the present invention.

[0033] FIG. 3 shows the deformation curvature of soft actuators obtained by soaking in aqueous solutions of calcium chloride with different concentrations at various temperatures.

[0034] FIG. 4 is a schematic diagram of a soft actuator structure with a heating electrode on the flexible silk fibroin membrane.

[0035] FIG. 5 is a schematic diagram of a soft actuator structure with a heating electrode on a flexible substrate.

[0036] FIG. 6 shows a curvature diagram of deformation for different regions of the soft actuator under different electric heating powers.

[0037] FIG. 7 shows the deformation diagram of the soft actuator under light stimulation.

[0038] In the figures, 1silk fibroin membrane, 2flexible substrate, 3heating electrode.

DESCRIPTION OF EMBODIMENTS

[0039] The following is a further detailed description of the present invention in combination with the accompanying drawings and specific embodiments.

[0040] An embodiment of the present invention is as follows:

Example 1

[0041] A calcium chloride-formic acid solution with a concentration of 3 wt % is prepared. 1.3 g of degummed silk is dissolved in 6.8 ml of the above solution, and placed in an ultrasonic cleaner and oscillated for 1 hour to obtain the silk fibroin solution.

[0042] A clean PI with a thickness of 30 m is adopted as the flexible substrate 2, and subjected to plasma treatment for 2 minutes. A four-sided preparation device with a thickness of 200 m is adopted to scrap-coat the wet silk fibroin membrane. After drying, a double-layer membrane including the silk fibroin membrane 1 and the flexible substrate 2 is obtained, as shown in FIG. 1. The double-layer membrane is respectively treated by not being soaked, entirely soaked in 1 wt % calcium chloride aqueous solution for 1 minute and blown dry with nitrogen, entirely soaked in 2 wt % calcium chloride aqueous solution for 1 minute and blown dry with nitrogen, and entirely soaked in 3 wt % calcium chloride aqueous solution for 1 minute and blown dry with nitrogen, thereby obtaining soft actuators with different deformation abilities.

[0043] When the actuator operates, the overall soft actuator is placed on a 100 C. hot plate. Since the thermal expansion coefficient of the silk fibroin membrane 1 is negative, the silk fibroin membrane 1 undergoes thermal contraction when temperature rises, while the thermal expansion coefficient of the PI flexible substrate 2 is positive, causing thermal expansion when temperature rises. This leads to the bending of the double-layer membrane structure of the soft actuator towards a side of the silk fibroin membrane 1, as shown in FIG. 2. After turning off the hot plate, the temperature of the actuator slowly decreases and returns to its initial morphology. The bending curvature may be regulated by the temperature of the hot plate, and the soft actuators obtained after soaking in calcium chloride aqueous solutions with different concentrations exhibit different bending curvatures, as shown in FIG. 3. The higher the concentration of the calcium chloride aqueous solution used for soaking, the greater the bending curvature of the soft actuator, indicating that the deformation ability of the silk fibroin-based soft actuator in the present invention may be effectively regulated through the concentration of calcium chloride.

Example 2

[0044] A calcium chloride-formic acid solution with a concentration of 4.8 wt % is prepared. 1.3 g of degummed silk is dissolved in 6.8 ml of the above solution, and placed in an ultrasonic cleaner and oscillated for 1 hour to obtain the silk fibroin solution.

[0045] A clean PET with a thickness of 50 m may be adopted as the flexible substrate 2, and subjected to plasma treatment for 2 minutes. A four-sided preparation device with a thickness of 100 m is used to scrap-coat the wet silk fibroin membrane. After drying, the thin membrane is washed in water for 5 minutes, and after drying, a double-layer membrane including the silk fibroin membrane 1 and the flexible substrate 2 is obtained, as shown in FIG. 1. The entire double-layer membrane is soaked in a 2 wt % calcium chloride aqueous solution for 1 minute, and then blown dry with nitrogen. Screen printing is utilized to print a silver heating electrode 3 on a side of the silk fibroin membrane 1 of the double-layer membrane, which is then cut to the required size to obtain the soft actuator, as shown in FIG. 4.

[0046] When the actuator is working, the heating electrode 3 is connected to a DC power supply. At a specific power, the heating electrode 3 generates Joule heat, causing the overall temperature of the soft actuator to rise. Since the thermal expansion coefficient of the silk fibroin membrane 1 is negative, the silk fibroin membrane 1 undergoes thermal contraction when temperature rises, while the PET flexible substrate 2 has a positive thermal expansion coefficient and undergoes thermal expansion when temperature rises. This leads to the double-layer membrane structure of the soft actuator bending towards a side of the silk fibroin membrane 1. The bending curvature may be regulated and controlled by the electrical power. After the power is turned off, the actuator returns to its initial morphology.

Example 3

[0047] A calcium chloride-formic acid solution with a concentration of 4.8 wt % is prepared. 1.3 g of degummed silk is dissolved in 6.8 ml of the above solution, and placed in an ultrasonic cleaner and oscillated for 1 hour to obtain the silk fibroin solution.

[0048] A clean PE with a thickness of 100 m may be adopted as the flexible substrate 2, and subjected to plasma treatment for 2 minutes. A four-sided preparation device with a thickness of 200 m is used to scrap-coat the wet silk fibroin membrane. After drying, the thin membrane is washed in water for 5 minutes, and after drying, a double-layer membrane including the silk fibroin membrane 1 and the flexible substrate 2 is obtained, as shown in FIG. 1. Half of the double-layer membrane is soaked in a 2 wt % calcium chloride aqueous solution for 1 minute, and then blown dry with nitrogen. Screen printing is utilized to print a silver heating electrode 3 on a side of the flexible substrate 2 of the double-layer membrane, which is then cut to the required size to obtain the soft actuator, as shown in FIG. 5.

[0049] When the actuator operates, the heating electrode 3 is connected to a DC power supply. At a specific power, the heating electrode 3 generates Joule heat, causing the overall temperature of the soft actuator to rise. Due to the negative thermal expansion coefficient of the silk fibroin membrane 1, the silk fibroin membrane 1 undergoes thermal contraction when temperature rises, while the PE flexible substrate 2 with a positive thermal expansion coefficient undergoes thermal expansion when temperature rises, resulting in the double-layer membrane structure of the soft actuator bending towards a side of the silk fibroin membrane 1. After turning off the power supply, the actuator returns to its initial morphology. Since silk fibroin membranes 1 with different calcium chloride contents possess different thermal expansion coefficients, the region soaked in 2 wt % calcium chloride solution exhibits a larger bending curvature than the region not soaked in calcium chloride solution. The bending curvature of different regions may be regulated and controlled by electrical power. As shown in FIG. 6, a bending curvature of 55 m.sup.1 may be generated at a heating power as low as 0.02 W. This result indicates that the soft actuator possesses very low energy consumption, and the deformation ability thereof may be adjusted through calcium chloride concentration, achieving programmable deformation in different regions.

Example 4

[0050] A calcium chloride-formic acid solution with a concentration of 3 wt % is prepared, and rhodamine B dye with a concentration of 100 mg/L is added thereto. 1.3 g of degummed silk is dissolved in 6.8 ml of the above solution, and placed in an ultrasonic cleaner and oscillated for 1 hour to obtain the silk fibroin solution containing photothermal conversion dye.

[0051] A clean PET with a thickness of 50 m may be adopted as the flexible substrate 2, and subjected to plasma treatment for 2 minutes. A four-sided preparation device with a thickness of 100 m is used to scrap-coat the wet silk fibroin membrane. After drying, a double-layer membrane including the silk fibroin membrane 1 and the flexible substrate 2 is obtained. The double-layer membrane sample is respectively treated by not being soaked, entirely soaked in 2 wt % calcium chloride aqueous solution for 1 minute and blown dry with nitrogen, half soaked in 2 wt % calcium chloride aqueous solution for 1 minute and blown dry with nitrogen, thereby obtaining soft actuators with different deformation abilities.

[0052] When the actuator operates, an infrared lamp irradiates the soft actuator. Under the photothermal effect of Rhodamine B, the overall temperature of the soft actuator rises. Due to the negative thermal expansion coefficient of the silk fibroin membrane 1, the silk fibroin membrane 1 undergoes thermal contraction when temperature rises, while the PET flexible substrate 2 with a positive thermal expansion coefficient undergoes thermal expansion when temperature rises, causing the double-layer membrane structure of the soft actuator to bend towards a side of the silk fibroin membrane 1. After turning off the light source, the actuator slowly returns to its initial morphology. The actuator or actuator region soaked in 2 wt % calcium chloride solution exhibits a larger bending curvature than the sample or region not soaked in calcium chloride solution, as shown in FIG. 7. This result indicates that the deformation ability of the soft actuator may be regulated and controlled through calcium chloride concentration, and programmable deformation of different regions may be achieved.

Example 5

[0053] A calcium chloride-formic acid solution with a concentration of 3 wt % is prepared. 1.3 g of degummed silk is dissolved in 6.8 ml of the above solution, and placed in an ultrasonic cleaner and oscillated for 1 hour to obtain the silk fibroin solution.

[0054] A clean PET with a thickness of 30 m may be adopted as the flexible substrate 2, and subjected to plasma treatment for 2 minutes. A four-sided preparation device with a thickness of 80 m is used to scrap-coat the wet silk fibroin membrane. After drying, a soft actuator with a double-layer membrane structure including the silk fibroin membrane 1 and the flexible substrate 2 is obtained, as shown in FIG. 1.

[0055] When the actuator operates, the overall soft actuator is placed on a nylon mesh, with a water tank filled with water underneath the mesh, so that the soft actuator is in a high humidity environment. Due to the water absorption and swelling of the silk fibroin membrane 1, while the PET flexible substrate 2 absorbs almost no water, the double-layer membrane structure of the soft actuator bends towards a side of the flexible substrate 2. After moving away from the humidity source, the actuator returns to its initial morphology.