A method for preparing a liquid crystal elastomer acoustic deflection sensitive element

Abstract

The present invention belongs to the field of acoustic wave measurement technology, and specifically relates to a method for preparing a liquid crystal elastomer acoustic polarization sensitive element. The method utilizes the electrical properties of liquid crystal materials, and adopts vibration and strong electric field to redirect the director of the liquid crystal, thereby ensuring the consistency of the liquid crystal director, improving the sensitivity of the light polarization state change to the deformation of the liquid crystal elastomer, and further ensuring the underwater acoustic detection sensitivity of the acoustic polarization sensitive element; a strong electric field at a 45° angle to the main optical axis of the acoustic polarization sensitive element is used to redirect the liquid crystal director, and the main optical axis of the liquid crystal elastomer sensitive element differs from the fast axis and slow axis of the liquid crystal by about 45°, so that the polarization state change of the polarized light of the sensitive element is maximized, further improving the sensitivity of the sensitive element. The present invention is tailor-made for polarization modulation hydrophones, has a simple process, is suitable for mass production, has low production cost, and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of acoustic wave measurement, and in particular relates to a method for preparing a liquid crystal elastomer acoustic deflection sensitive element. Background Art

[0002] In underwater acoustic detection and information acquisition, hydrophones are devices used to receive underwater sound waves. Most hydrophones on the market are piezoelectric, piezoresistive, magnetoelectric, capacitive, or fiber optic. Acoustic polarization modulation hydrophones, a new type of hydrophone, modulate underwater acoustic signals onto the polarization angle of light through a sensitive element to detect underwater sound. However, research on their acoustic polarization modulation sensitive elements is limited.

[0003] The acoustic polarization sensitive element is the core of a photoacoustic polarization modulated hydrophone. It picks up underwater acoustic signals and converts them into signals of changes in the optical polarization angle. As a crucial component of a hydrophone, the sensitive element is the most important factor affecting the hydrophone's sensitivity, self-noise, optical wavelength, and detection bandwidth. Its fabrication method is crucial to the performance of the hydrophone. Furthermore, because the fabrication of acoustic polarization sensitive elements involves knowledge from multiple disciplines, including hydroacoustics, optics, materials science, structural mechanics, and dynamics, and is highly theoretically and technically demanding, a mature method for fabricating these elements remains elusive. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a liquid crystal elastomer acoustic polarization sensitive element. The obtained liquid crystal elastomer acoustic polarization sensitive element can convert an underwater acoustic signal into a signal of a change in light polarization angle, thereby realizing acoustic polarization conversion and improving the sensitivity of the sensitive element.

[0005] The technical solutions adopted are:

[0006] A method for preparing a liquid crystal elastomer acoustic deflection sensor comprises the following steps:

[0007] (1) Prefabricate a metal packaging box, 3D print a liquid crystal box made of transparent resin, and fix the liquid crystal box to a vibrating polarization table, keeping the optical axis of the liquid crystal box at a 45° angle to the electric field direction;

[0008] (2) mixing the liquid crystal material, monomer material, auxiliary material and photosensitive initiator and placing them in a heated stirring container, heating the mixture in the dark, maintaining the temperature in the dark and fully stirring to allow the liquid crystal material and the elastic monomer material to fully mix and react to obtain an oligomer precursor;

[0009] (3) Turning on the vibration and strong electric field switches of the vibrating polarization table, squeezing the heated oligomer precursor into the liquid crystal cell, so that the liquid crystal of the oligomer precursor is kept away from light under the action of vibration and strong electric field, and the director is redirected; at this time, the direction of the strong electric field is 45 degrees to the main optical axis of the liquid crystal cell;

[0010] (4) turning off the vibration switch, cooling the liquid crystal box in the dark, and performing a preliminary Michael addition reaction to solidify the oligomer precursor into a liquid crystal elastomer (during this process, the oligomer precursor is partially solidified into the liquid crystal elastomer but is not completely solidified);

[0011] (5) Turn on the illumination switch and illuminate the liquid crystal elastomer under a strong electric field to expose the liquid crystal elastomer and initially anchor the director;

[0012] (6) Turn off the light switch, maintain the strong electric field, and continue the Michael addition reaction in the dark;

[0013] (7) turning on the light switch to illuminate the liquid crystal elastomer, so that the director of the liquid crystal elastomer is completely anchored;

[0014] (8) Assemble the liquid crystal box into the prefabricated metal packaging box to complete the preparation of the acoustic polarization sensitive element.

[0015] Preferably, in step (1), the metal packaging box is a cylindrical cavity, with an incident light connector connector and an output light connector connector respectively provided at both ends, and an opening provided in the middle of the cylinder; the liquid crystal box is a cylindrical cavity closed at both ends, and an underwater acoustic coupling window is provided on the cylindrical surface, and a row of oligomer precursor extrusion holes is provided below the underwater acoustic coupling window.

[0016] The extrusion holes are evenly arranged, with 5 to 10 holes being provided, and the direction of the extrusion holes is at a 45° angle to the main optical axis of the liquid crystal cell.

[0017] Preferably, the length of the liquid crystal box is 2 to 2.5 cm, the circular diameter is 1.5 to 2 cm, the underwater acoustic coupling window is 1 cm × 1.5 cm (the underwater acoustic coupling window is open and not sealed with transparent resin), and the opening size of the prefabricated metal packaging box is the same as the size of the underwater acoustic coupling window of the liquid crystal box; during installation, the underwater acoustic coupling window is opposite to the opening on the metal packaging box.

[0018] Preferably, in step (2), the raw materials of the oligomer precursor have the following weight percentages: 45% to 80% liquid crystal material, 20% to 60% monomer material, 0 to 5% auxiliary material, and 0.2% to 2% photoinitiator; the temperature of the heated mixture is 65 to 100°C.

[0019] Preferably, the liquid crystal material is any one of liquid crystal BP006, liquid crystal HCCH-BP4, and liquid crystal RM82; the monomer material is a mixture of one or more of n-butylamine, acrylate, C3M, EDDET, TMPTA, NVP, and RM257; the photoinitiator is any one of photoinitiator I-651 and photoinitiator IRG-184; and the auxiliary material is chiral dopant R5011 or base catalyst DPA.

[0020] Preferably, in the step (3), the oligomer precursor is squeezed into the liquid crystal cell to a height of the squeeze-in hole, with no overflow being the standard.

[0021] Preferably, in step (3), the vibration frequency is 5 to 50 Hz and the electric field strength is 0.5 to 10 kV / m. Providing the liquid crystal cell with a vibration frequency of 5 to 50 Hz is mainly intended to provide greater kinetic energy for the redirection of the liquid crystal director and increase the activity space of the liquid crystal macromolecules.

[0022] The main purpose of placing the liquid crystal box under the action of a strong electric field (electric field strength of 0.5 to 10 kV / m) is to provide a direction for the redirection of the liquid crystal director. The direction of the strong electric field is 45 degrees to the predetermined optical axis.

[0023] Preferably, in step (4), the liquid crystal box is cooled to 24-40° C. at a rate of 0.3-1° C. / min, and then maintained at this temperature in the dark for 60-90 min to ensure the Michael addition reaction.

[0024] Preferably, in step (5), the light intensity is set to 1 mW / cm 2 ~20mW / cm 2 , maintain the predetermined temperature at 24-40°C and irradiate under strong electric field for 1-2 minutes.

[0025] Preferably, in step (6), the predetermined temperature is maintained at 24-40° C. and kept away from light for 3-6 hours.

[0026] Preferably, in step (7), the light intensity is set to 20 mW / cm 2 ~80mW / cm 2 , turn on the light switch, maintain the preset temperature at 24-40℃ and light for 10-20 minutes.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention discloses a method for preparing a liquid crystal elastomer acoustic polarization sensitive element. The method utilizes the electrical properties of liquid crystal materials and adopts vibration and a strong electric field to redirect the director of the liquid crystal, thereby ensuring the consistency of the liquid crystal director and improving the sensitivity of light polarization state changes to the deformation of the liquid crystal elastomer, thereby ensuring the underwater acoustic detection sensitivity of the acoustic polarization sensitive element.

[0029] The present invention discloses a method for preparing a liquid crystal elastomer acoustic polarization sensitive element. The method uses a strong electric field at a 45° angle to the principal optical axis of the acoustic polarization sensitive element to redirect the liquid crystal director. The principal optical axis of the liquid crystal elastomer sensitive element differs from both the fast axis and the slow axis of the liquid crystal by approximately 45°, minimizing the polarization state measurement error and further improving the sensitivity of the sensitive element.

[0030] The invention discloses a method for preparing a liquid crystal elastomer acoustic polarization sensitive element, which is tailor-made for a photoacoustic polarization modulation hydrophone, has a simple process, is suitable for mass production, has a low production cost, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a three-dimensional structural diagram of the prefabricated metal packaging box of the present invention.

[0032] Figure 2 This is a three-dimensional structural diagram of the liquid crystal box of the present invention using 3D printed transparent resin.

[0033] Figure 3 This is a top view of the liquid crystal box of the present invention fixed on a vibrating polarization table.

[0034] In the figure, 1-metal packaging box, 11-output light connector plug-in, 12-incident light connector plug-in, 13-opening, 2-liquid crystal box, 21-hydroacoustic coupling window, 22-extrusion hole, 3-vibration table, 4-positive electrode, 5-negative electrode. DETAILED DESCRIPTION

[0035] The accompanying drawings are for illustrative purposes only and do not represent the actual size, orientation, etc. of the product; the present disclosure will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] The reagents used in the present invention can all be purchased through commercial channels.

[0037] Example 1

[0038] A vibration polarization table consists of a square baseplate with a positive electrode and a negative electrode placed vertically at opposite ends. The positive and negative electrodes are parallel to each other, creating a strong electric field when powered. The field strength can also be controlled by setting a switch. Currently unavailable commercially, these devices are typically made in laboratories. However, commercially available vibration tables are constructed by attaching two parallel electrodes to the table and applying a DC voltage.

[0039] This embodiment discloses a method for preparing a nematic liquid crystal elastomer acoustic polarization sensitive element, comprising the following steps.

[0040] Step 1: Prefabricate the metal packaging box, such as Figure 1 As shown, the metal packaging box is a cylindrical cavity with incident light connector and outgoing light connector respectively set at both ends, and an opening adapted to the liquid crystal box is set in the middle of the column. Figure 2 As shown, the liquid crystal cell is a cylindrical cavity with a row of evenly spaced holes for oligomer precursor extrusion. The holes are oriented at a 45° angle to the main optical axis of the liquid crystal cell. A hydroacoustic coupling window is also provided. During assembly, the hydroacoustic coupling window of the liquid crystal cell faces outward.

[0041] like Figure 3 As shown, the liquid crystal box is fixed to the vibrating polarization table, and the optical axis direction of the liquid crystal box is kept at a 45° angle to the electric field direction.

[0042] Step 2: Prepare the mixture in the following proportions.

[0043] Liquid crystal RM82 (1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene): monomer n-butylamine: photoinitiator I-651 = 55:44:1, the mixture was heated to 80°C in the dark, maintained at this temperature in the dark and fully stirred for 16 hours to obtain an oligomer precursor.

[0044] Step 3: Turn on the vibration and strong electric field switches of the vibrating polarization table, squeeze the 80°C polymer into the liquid crystal cell, keep it away from light for 1 minute, the vibration frequency is 25 Hz, and the electric field strength is 5 kV / m.

[0045] Step 4: Turn off the vibration button, cool the liquid crystal box to 28°C at a rate of 0.3°C / min, and then keep it at this temperature in the dark for 60 minutes.

[0046] Step 5: Set the light intensity to 10mW / cm 2 , turn on the purple light switch, maintain the preset temperature of 28℃, electric field and light for 1 minute.

[0047] Step 6: Turn off the light switch, maintain the electric field intensity at 5 kV / m, maintain the predetermined temperature at 28° C., keep away from light for 6 hours, and continue the Michael addition reaction.

[0048] Example 2

[0049] This embodiment discloses a method for preparing a blue phase liquid crystal elastomer acoustic polarization sensitive element, comprising the following steps.

[0050] Step 1: Prefabricate a metal packaging box, 3D print a transparent resin liquid crystal box, and fix the liquid crystal box to a vibrating polarization table, keeping the optical axis of the liquid crystal box at a 45° angle to the electric field direction.

[0051] Fix the liquid crystal box on the vibrating polarization table and keep the optical axis of the liquid crystal box at a 45° angle to the electric field direction.

[0052] Step 2: Prepare the mixture in the following proportions.

[0053] Liquid crystal BP006: chiral dopant R5011: monomer RM105 (acrylate): monomer C3M: monomer EDDET: base catalyst DPA (di-n-propylamine): photoinitiator IRG-184 = 46.9: 3.1: 8.2: 29.9: 11.3: 0.2: 0.4. Heat the mixture to 80°C in the dark, maintain this temperature in the dark and stir thoroughly for 16 hours to obtain an oligomer precursor.

[0054] Step 3: Turn on the vibration and strong electric field switches of the vibrating polarization table, squeeze the 80°C polymer into the liquid crystal cell, keep it away from light for 1 minute, set the vibration frequency to 50 Hz, and the electric field strength to 5 kV / m.

[0055] Step 4: Turn off the vibration button, cool the liquid crystal box to 27°C at a rate of 0.3°C / min, and then keep it at this temperature in the dark for 60 minutes.

[0056] Step 5: Set the light intensity to 20mW / cm 2 , turn on the purple light switch, maintain the preset temperature of 27℃, electric field and light for 1 minute.

[0057] Step 6: Turn off the light switch, maintain the predetermined temperature of 27° C. under the action of an electric field strength of 5 kV / m, and keep it away from light at this temperature for 6 hours to continue the Michael addition reaction.

[0058] Step 7: Set the light intensity to 70mW / cm 2 Turn on the illumination switch, maintain the predetermined temperature at 27° C., and illuminate for 20 minutes to completely anchor the director of the liquid crystal elastomer.

[0059] Step 8: Assemble the liquid crystal box into the prefabricated metal packaging box to complete the preparation of the acoustic polarization sensitive element.

[0060] Other unmentioned places are the same as those in Example 1.

[0061] Example 3

[0062] This embodiment discloses a method for preparing a cholesteric liquid crystal elastomer acoustic polarization sensitive element, comprising the following steps.

[0063] Step 1: Prefabricate a metal packaging box, 3D print a transparent resin liquid crystal box, and fix the liquid crystal box to a vibrating polarization table, keeping the optical axis of the liquid crystal box at a 45° angle to the electric field direction.

[0064] Fix the liquid crystal box on the vibrating polarization table and keep the optical axis of the liquid crystal box at a 45° angle to the electric field direction.

[0065] Step 2: Prepare the mixture in the following proportions.

[0066] Liquid crystal HCCH-BP4: monomer TMPTA: monomer NVP: monomer RM257: chiral agent R5011: photoinitiator I-651 = 70:7:4:12:4:1. Heat the mixture to 80°C in the dark, maintain this temperature in the dark and stir thoroughly for 20 hours to obtain an oligomer precursor.

[0067] Step 3: Turn on the vibration and strong electric field switches of the vibrating polarization table, squeeze the 80°C polymer into the liquid crystal cell, keep it away from light for 1 minute, the vibration frequency is 25 Hz, and the electric field strength is 5 kV / m.

[0068] Step 4: Turn off the vibration button, cool the liquid crystal box to 27°C at a rate of 0.3°C / min, and then keep it at this temperature in the dark for 90 minutes.

[0069] Step 5: Set the light intensity to 10 mW / cm2, turn on the purple light switch, and maintain the predetermined temperature of 27°C, electric field, and light for 1 minute.

[0070] Step 6: Turn off the light switch, maintain the predetermined temperature of 27° C., keep it away from light at this temperature for 6 hours, and continue the Michael addition reaction under the action of the electric field.

[0071] Step 7: Set the light intensity to 60mW / cm 2 Turn on the illumination switch, maintain the predetermined temperature at 27° C., and illuminate for 20 minutes to completely anchor the director of the liquid crystal elastomer.

[0072] Step 8: Assemble the liquid crystal box into the prefabricated metal packaging box to complete the preparation of the acoustic polarization sensitive element.

[0073] Other unmentioned places are the same as those in Example 1.

[0074] The meanings of the English abbreviations used in this invention are:

[0075] Photoinitiator I-651: benzil dimethyl ether, α, α-dimethoxy-α-phenylacetophenone;

[0076] RM105: Acrylates, 4-methoxyphenyl-4-((6-(acryloyloxy)hexyl)oxy)benzoate;

[0077] C3M: diacrylate, 4-bis-[4-(3-acryloyloxypropionyloxy)benzoyloxy]-2-methylbenzene;

[0078] EDDET: 2,2-(ethylenedioxy)dithiol, 2'-(1,2-ethylenedioxy)bis(ethanethiol);

[0079] RM82: 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene;

[0080] IRG-184: 1-hydroxycyclohexylphenyl ketone;

[0081] RM257: 1,4-bis-[4-(3-acryloyloxypropionyloxy)benzoyloxy]-2-toluene;

[0082] DPA: di-n-propylamine;

[0083] TMPTA: trimethylolpropane triacrylate;

[0084] NVP: N-vinylpyrrolidone;

[0085] BP006: Nematic liquid crystal mixture produced by Jiangsu Hecheng New Materials Co., Ltd. (HCCH);

[0086] R5011: chiral dopant produced by Jiangsu Hecheng New Materials Co., Ltd. (HCCH);

[0087] HCCH-BP4: Shulibenzophenone produced by Jiangsu Hecheng New Materials Co., Ltd. (HCCH), molecular formula C14H12O6S.

[0088] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for preparing a liquid crystal elastomer acoustic deflection sensor, characterized in that: The specific steps include: (1) Prefabricate a metal packaging box, which is a cylindrical cavity with incident light connectors and outgoing light connectors at both ends, and an opening in the middle of the cylinder; 3D print a liquid crystal box made of transparent resin and fix the liquid crystal box to a vibration polarization table; The liquid crystal cell is a cylindrical cavity with closed ends, and an underwater acoustic coupling window is provided on the cylindrical surface. A row of holes for extrusion of oligomer precursors is provided below the underwater acoustic coupling window. The liquid crystal cell has a length of 2 to 2.5 cm and a circular diameter of 1.5 to 2 cm. The size of the underwater acoustic coupling window is 1 cm x 1.5 cm. The opening size of the prefabricated metal packaging box is the same as that of the underwater acoustic coupling window of the liquid crystal cell. During installation, the underwater acoustic coupling window faces the opening of the metal packaging box. (2) Mixing the liquid crystal material, monomer material, auxiliary material and photosensitive initiator, placing the mixture in a heated stirring container, heating the mixture in the dark, maintaining the temperature in the dark and stirring the mixture sufficiently, so that the liquid crystal material and the elastic monomer material are fully mixed and reacted to obtain an oligomer precursor; (3) Turn on the vibration and strong electric field switches of the vibrating polarization table, squeeze the heated oligomer precursor into the liquid crystal cell, and keep the liquid crystal of the oligomer precursor away from light under the action of vibration and strong electric field, and redirect the director; at this time, the direction of the strong electric field is 45 degrees to the main optical axis of the liquid crystal cell; (4) Turn off the vibration switch and cool the liquid crystal box away from light to perform a preliminary Michael addition reaction, so that the oligomer precursor is solidified into a liquid crystal elastomer; (5) Turn on the illumination switch and illuminate the liquid crystal elastomer under a strong electric field to expose the liquid crystal elastomer and initially anchor the director; (6) Turn off the light switch, maintain the strong electric field, and continue the Michael addition reaction in the dark; (7) Turn on the light switch to illuminate the liquid crystal elastomer, so that the liquid crystal elastomer director is completely anchored; (8) Assemble the liquid crystal box into the prefabricated metal packaging box to complete the preparation of the acoustic polarization sensitive element.

2. The method for preparing a liquid crystal elastomer acoustic polarization sensor according to claim 1, characterized in that: In the step (2), the raw materials of the oligomer precursor are as follows: 45% to 80% of liquid crystal material, 20% to 60% of monomer material, 0% to 5% of auxiliary material, and 0.2% to 2% of photoinitiator in weight percentage; the temperature of the heated mixture is 65°C to 100°C.

3. The method for preparing a liquid crystal elastomer acoustic polarization sensor according to claim 1, wherein: In the step (3), the vibration frequency is 5-50 Hz, and the electric field strength is 0.5-10 KV / m.

4. The method for preparing a liquid crystal elastomer acoustic polarization sensor according to claim 1, wherein: In the step (3), the oligomer precursor is squeezed into the liquid crystal cell to the height of the squeeze hole.

5. The method for preparing a liquid crystal elastomer acoustic polarization sensor according to claim 1, wherein: In the step (4), the liquid crystal box is cooled to 24°C to 40°C at a rate of 0.3 to 1°C / min, and then maintained at this temperature in the dark for 60 to 90 minutes to ensure the Michael addition reaction.

6. The method for preparing a liquid crystal elastomer acoustic polarization sensor according to claim 1, wherein: In step (5), the light intensity is set to 1 mW / cm 2 ~20mW / cm 2 , maintain the predetermined temperature at 24℃~40℃ and illuminate under a strong electric field for 1~2 minutes.

7. The method for preparing a liquid crystal elastomer acoustic polarization sensor according to claim 1, wherein: In the step (6), the predetermined temperature is maintained at 24°C to 40°C and kept away from light for 3 to 6 hours.

8. The method for preparing a liquid crystal elastomer acoustic polarization sensor according to claim 1, characterized in that: In step (7), the light intensity is set to 20 mW / cm 2 ~80mW / cm 2 , turn on the light switch, maintain the preset temperature at 24℃~40℃ and light for 10~20 minutes.

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