Azo-based ion conductive gel for monitoring human body movement and preparation method thereof

Abstract

The present invention discloses an azo-based ion conductive gel for monitoring human body movement and a preparation method, and belongs to the technical field of polymer functional materials and their applications. The present invention uses polyvinyl alcohol with different molecular weights as the main polymer network structure of the gel, uses cellulose nanofibers / cellulose nanocrystals as nanofillers, and main chains containing hydroxyazobenzene with different alkyl chain lengths as functional monomers to obtain the functional azo-based ion conductive gel. The present invention introduces functional azo groups on the basis of ion conductive gel, which has high tensile properties, high transparency, strong toughness, high conductivity, weather resistance and good light responsiveness. The azo-based ion conductive gel has good electromechanical and photoelectric effects and sensitive stress-strain capabilities, has certain advantages in the field of sensing for monitoring human body movement, and can be used for the manufacture of sports equipment.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of polymer functional materials, and in particular to an azo-based ion conductive gel for monitoring human body movement and a preparation method thereof. Background Art

[0002] With the rapid development of wearable electronic devices and personal health monitoring, flexible conductive gels have made great progress in the design and manufacturing process of stretchable biomedical electronic products and optoelectronic components due to their inherent high stretchability, high transparency and good mechanical properties. However, traditional flexible conductive gels have difficult problems such as poor water retention, low tensile strength, poor weather resistance and poor compatibility with other devices. In addition, ion conductive gels are difficult to balance mechanical strength and ion conductivity, which limits their practical applications.

[0003] In recent years, the adjustable surface charge characteristics of cellulose nanofibers and cellulose nanocrystals and the anti-ion migration rate effect of carboxyl functional groups can effectively enhance the polymer gel network and effectively improve the ion conductivity, which has attracted widespread attention. Due to its cis-trans isomerism under different light sources, azo groups are widely used in information storage, oil-water separation, optoelectronic devices and other fields, accompanied by different appearance, mechanical properties, and electrical signal conversion.

[0004] Traditional ion conductive gels use water as the ionic liquid, so electronic devices are difficult to work normally at sub-zero temperatures. In addition, the single water solvent has a high water loss rate, and the working life of flexible electronic devices is short. The strong molecular effect between binary solvent systems causes increased mechanical strength, reduced water loss rate, and enhanced freeze resistance, which have been deeply explored in the field of flexible conductive gels. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a novel azo-based ion conductive gel for monitoring human body movement and a preparation method thereof. The present invention uses polyvinyl alcohol as a flexible matrix, cellulose nanofibers or cellulose nanocrystals as fillers, and azobenzene as a functional group. The prepared azo-based ion conductive gel has high stretchability, high transparency, high ionic conductivity, good frost resistance and excellent mechanical / photoelectric effect, and can be used for the preparation of sensor devices.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing an azo-based ion conductive gel for monitoring human body movement, comprising:

[0008] S1: Disperse monomer A in 10 g of solvent a under stirring at room temperature;

[0009] S2: Prepare 6g aqueous solutions of monomer B with different mass fractions, add them dropwise to the S1 solution, and stir at room temperature to obtain a uniformly dispersed solution;

[0010] S3: adding monomer C with a certain mass ratio to monomer B and a different molecular weight, and heating in an oil bath under continuous stirring until monomer C is completely dissolved;

[0011] S4: After the reaction is finished, stirring is stopped, and the mixture is allowed to settle in an oil bath to remove bubbles generated during the reaction, and then the mixture is transferred to a specific mold and placed in a freeze dryer / refrigerator to obtain an azo gel;

[0012] S5: soaking the azo gel in different salt solutions D for a period of time to obtain the final product, the azo ion conductive gel;

[0013] The reaction formula for preparing the above-mentioned azo-based ion conductive gel is as follows:

[0014]

[0015] Furthermore, in step S1, the monomer A is 4,4-dihydroxyazobenzene or one of dihydroxyazobenzenes with alkyl chains of different lengths, with a mass of 0.01-0.05 g, and the solvent a is dimethyl sulfoxide or ethylene glycol, with a mass of 10 g;

[0016] Furthermore, in step S2, monomer B is cellulose nanofiber or cellulose nanocrystal, with a mass of 0.018-0.36 g, and a mass ratio with monomer C of 1:5, 1:10, 1:20, 1:25, 1:50 and 1:100;

[0017] Further, in step S3, monomer C is M W The amount of polyvinyl alcohol added is 1.5-2.0g for 47000, 67000, and 195000, which can be properly adjusted. The oil bath heating temperature is 80-110℃;

[0018] Furthermore, the specific mold in step S4 is a PTFE mold with a size of (40-80) mm×(40-80) mm×(5-30) mm and a freezing temperature of -15 to -25°C;

[0019] Furthermore, the specific operation process of step S5 is: prepare salt solution D of different concentrations (0.5-3.5M), where the salt solution D is any one of common types such as sodium chloride, potassium chloride, sodium sulfate, calcium chloride, etc., and immerse the formed ion conductive gel in 16-32g of the salt solution for 24-48h.

[0020] Further, the synthesis method of 4,4-dihydroxyazobenzene comprises:

[0021] (1) Slowly add a certain volume of 3M dilute hydrochloric acid to p-aminophenol and deionized water, stir evenly to form a light brown reddish brown solution, and place in an ice water bath;

[0022] (2) slowly adding an aqueous solution of sodium nitrite to the above solution, and the solution turns grape purple;

[0023] (3) preparing a diazonium salt solution: adding deionized water, copper sulfate pentahydrate, ammonia water (25%), and hydroxylamine hydrochloride in a certain mass ratio;

[0024] (4) After the solution (3) is homogeneous, add it dropwise to the solution (2) using a dropping funnel. The system is a mixture of dark purple liquid and yellow mud-colored floccules. Remove the ice water bath and stir at room temperature.

[0025] (5) After the reaction, the reaction system was filtered to obtain a yellow mud product, which was washed with ethanol, filtered, concentrated by a rotary evaporator, washed with deionized water, 2M dilute hydrochloric acid, and deionized water, and filtered;

[0026] (6) Recrystallize the mixture of 50 mL of ethanol and water in a volume ratio of 1:1 with 10 mL of deionized water in step (1), vacuum dry, and weigh to obtain a black granular product with a certain crystalline form. The amount of each substance added can be appropriately adjusted according to this ratio.

[0027] Further, the preparation reaction formula of 4,4-dihydroxyazobenzene is as follows:

[0028]

[0029] Furthermore, in step (1), the mass of p-aminophenol is 2 g, and the volume of 3M dilute hydrochloric acid is 40 mL, based on 10 mL of deionized water;

[0030] Furthermore, the step (2) is 100 mL of a sodium nitrite aqueous solution having a mass fraction of 1.33 wt %;

[0031] Furthermore, the mass ratio of the components of the diazonium salt in step (3) is 18.3:8.2:5.5:1.3, and the total mass is 33.3 g. The amount of each substance added can be appropriately adjusted according to this ratio;

[0032] Furthermore, the stirring time at room temperature in step (4) is 2.5-3.5h;

[0033] Furthermore, the volume ratio of deionized water, 2M dilute hydrochloric acid, and deionized water in step (5) is 1:1:1. Based on 10 mL of deionized water in step (1), the total volume is not less than 60 mL and not more than 80 mL. The amount of each substance added is appropriately adjusted according to this ratio.

[0034] The synthesis methods of hydroxyazobenzenes with different alkyl chains include:

[0035] (7) Potassium carbonate and 4,4-dihydroxyazobenzene are added to N,N-dimethylformamide in a certain molar ratio and stirred evenly at room temperature;

[0036] (8) Add potassium iodide and chloro / bromo-R-alcohol (in a certain molar ratio with azobenzene) to the solution of (1) and stir vigorously in an oil bath;

[0037] (9) The reaction system was cooled to room temperature and placed on 900 g of crushed ice to obtain a red precipitate, which was recrystallized twice from n-hexane to obtain a brown-yellow product with a certain crystalline form.

[0038] The preparation reaction formula of hydroxyazobenzene with different alkyl chains is shown below:

[0039]

[0040] Furthermore, based on 40 mL of N,N-dimethylformamide in step (7), the molar ratio of potassium carbonate to 4,4-dihydroxyazobenzene is 1:1, and the total mass is 15 g. The amount of each substance added can be appropriately adjusted according to this ratio.

[0041] Furthermore, in step (8), the amount of potassium iodide added is 0.015-0.018 g, the molar ratio of chloro / bromo-R-alcohol to 4,4-dihydroxyazobenzene is 1.05-1.15:1, the chloro / bromo-R-alcohol is slightly excessive, R is a 2-7 methylene chain, and the reaction temperature is 105-120°C.

[0042] Furthermore, the total amount of n-hexane recrystallized twice in step (9) is 1500 mL.

[0043] On the other hand, the present invention also provides a sensor device for monitoring human body movement, wherein the sensor type is an electromechanical sensor or a photoelectric sensor; two identical conductive gels prepared by the above method are placed with a polyimide tape in the middle as a dielectric layer, and copper electrodes are connected. After the connection is completed, the polyimide tape is used for entanglement and sealing to prevent dehydration, thereby obtaining a sensor device for monitoring human body movement.

[0044] Furthermore, the azo-based ion conductive gel is in the shape of a long strip.

[0045] In another aspect, the present invention further provides an application of the above-mentioned sensor device for monitoring human body movement, which is applied to at least one of the following (1)-(4):

[0046] (1) Measure the finger joint / knee joint signals of human body;

[0047] (2) Determine human pulse signal;

[0048] (3) Determine the Adam's apple signal when the human body makes different sounds;

[0049] (4) Measure the light intensity signal.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The invention provides a method for synthesizing hydroxyazobenzene and extended hydroxyazobenzene, focusing on the improvement of post-processing, obtaining azo monomers with high purity (more than 99%), improving the sensitivity of photoelectric response, and being able to construct photoelectric sensor devices.

[0052] The invention provides a method for preparing an azo-based ion gel, wherein polyvinyl alcohol is used as a polymer network structure of the gel, cellulose nanofibers / cellulose nanocrystals are used as nanofillers, and dihydroxyazobenzene is used as a functional group to construct a binary solvent system conductive gel, which has high tensile properties (600%), strong toughness (2.2Mpa), high water retention rate (92%), and good frost resistance (-60°C), can extend the service life of flexible electronic devices, and can be applied to the construction of sensor devices for monitoring human motion or in the field of mechanical / optical-electrical sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The morphology of the azo-based ion conductive gel prepared in Example 1 of the present invention;

[0054] Figure 2 The repeatable real-time response of the sensor device prepared in Example 2 of the present invention under full-wavelength illumination;

[0055] Figure 3 This is the stress-strain curve of the azo-based ion conductive gel prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0056] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0057] Unless otherwise specified, the reagents and materials used in the examples and comparative examples can be obtained through commercial channels.

[0058] The present invention provides an azo-based ion conductive gel for monitoring human body movement and a preparation method thereof, and specific embodiments are as follows.

[0059] Example 1

[0060] A method for preparing an azo-based ion conductive gel for monitoring human body movement, comprising:

[0061] Add 2g p-aminophenol and 10mL deionized water into a 250mL three-necked flask, and add 40ml 3M dilute hydrochloric acid dropwise under magnetic stirring. The addition should be completed within 30 minutes. The system should be a light brown reddish brown solution. Place the flask in an ice water bath.

[0062] Weigh 1.33 g of sodium nitrite and dissolve it in 100 mL of deionized water. After stirring evenly, add it dropwise into the three-necked flask through a dropping funnel. Add the solution dropwise over one hour.

[0063] In a 500 mL three-necked flask, 18.3 g of deionized water, 8.2 g of copper sulfate pentahydrate, 6 g of ammonia water (25%) and 1.3 g of hydroxylamine hydrochloride were added in sequence to prepare diazonium salt; the diazonium salt solution was added dropwise to the above solution through a dropping funnel, the ice water bath was removed, and the reaction was continued at room temperature for 2.5 h;

[0064] The reaction system was filtered to obtain a yellow mud-like product, which was dissolved in an appropriate amount of ethanol and filtered to obtain a reddish-brown filtrate. The ethanol was evaporated off in a vacuum to obtain a crude product. The crude product was then washed with (2×10 mL) deionized water, (2×10 mL) 2M dilute hydrochloric acid, and (2×10 ml) deionized water, and then recrystallized in a 1:1 ethanol:water mixture, vacuum dried, and weighed to obtain 1.5 g of 4,4-dihydroxyazobenzene;

[0065] 4,4-dihydroxyazobenzene (9.104 g, 0.0425 mol), K2CO3 (5.865 g, 0.0425 mol) and 40 mL of DMF were fully dissolved in a 100 mL single-necked flask, and the solution was stirred at 30 °C for 30 min until it was evenly dispersed;

[0066] KI (0.015 g, 0.090 mol) and 6-chloro-1-hexanol (6.174 g, 0.045 mol) were added to the solution, and the mixture was vigorously stirred and refluxed at 110° C. in an oil bath for 24 h; the reaction solution was cooled to room temperature, and dropped into 900 g of crushed ice, and the precipitate was collected by suction filtration. The product was recrystallized twice in 1500 mL of n-hexane, and then vacuum dried at 50° C. for 24 h after recrystallization, and 12.253 g was weighed to obtain the final 4-hexylhydroxy ether p-hydroxyazobenzene;

[0067] Under stirring at room temperature, 0.02 g of 4,4-dihydroxyazobenzene was dispersed in 10 g of dimethyl sulfoxide, 6 g of an aqueous solution of 0.2 g of cellulose nanofibers was prepared, and the solution was added dropwise to the azobenzene solution and stirred at room temperature to obtain a uniformly dispersed solution;

[0068] Add 2.0 g of polyvinyl alcohol with a molecular weight of 67,000, stir continuously, increase the temperature stepwise, and heat the oil bath to 90°C. After the polyvinyl alcohol is completely dissolved, continue stirring at this temperature for 3 h.

[0069] After the reaction is completed, stirring is stopped, and the mixture is allowed to stand in an oil bath to precipitate to remove bubbles generated during the reaction. The mixture is transferred to a 60 mm × 60 mm × 10 mm PTFE mold and placed in a refrigerator at -20°C for 24 h to obtain an azo gel. The azo gel is immersed in a 20 g 1 M KCl salt solution for 36 h to obtain the final product, an azo ion conductive gel. The morphology is shown in FIG. Figure 1 .

[0070] The prepared conductive gel was tested for performance, specifically:

[0071] The tensile test was performed by a universal testing machine. The test conditions were room temperature. The samples were cut into standard test sizes and stretched at a rate of 10 mm / min to obtain the stress-strain curve of the samples. Figure 3 , its elongation at break is over 600%;

[0072] The conductive gel prepared by the present invention is immersed in deionized water at room temperature of 25°C, the deionized water is replaced regularly and the hydrogel is taken out, the surface water is absorbed with filter paper, and then weighed until the hydrogel reaches swelling equilibrium. The hydrogel that has reached swelling equilibrium is vacuum freeze-dried at -40°C and weighed. The water retention rate is calculated by the following formula:

[0073] SR=(W s -W d ) / W d ; W s is the mass after vacuum freeze drying, unit is g; W d is the mass of the initial hydrogel, in g.

[0074] Its water retention rate is as high as 92%.

[0075] After the conductive gel prepared by the present invention is stored at -60°C for 24 hours, its mechanical strength, tensile properties and the like remain almost unchanged, and it has good freeze resistance.

[0076] Take two identical conductive gels prepared above, put a polyimide layer in the middle, connect copper electrodes at both ends, and seal with transparent polyimide to prevent dehydration to obtain a sensor device. The image of the current change over time obtained by the test is shown in Figure 2 , proving that the material has good sensitivity and accuracy.

[0077] Example 2

[0078] A method for preparing an azo-based ion conductive gel for monitoring human body movement, comprising:

[0079] Add 2g p-aminophenol and 10mL deionized water into a 250mL three-necked flask, and add 40mL 3M dilute hydrochloric acid dropwise under magnetic stirring. The addition should be completed within 30 minutes. The system should be a light brown reddish brown solution. Place the flask in an ice water bath.

[0080] Weigh 1.33 g of sodium nitrite and dissolve it in 100 mL of deionized water. Stir well and then add it dropwise into the three-necked flask through a dropping funnel. Add the mixture dropwise over one hour.

[0081] In a 500mL three-necked flask, 18.3g of deionized water, 8.2g of copper sulfate pentahydrate, 6g of ammonia water (25%) and 1.3g of hydroxylamine hydrochloride were added in sequence to prepare diazonium salt; the diazonium salt solution was added dropwise to the above solution through a dropping funnel, the ice water bath was removed, and the reaction was continued at room temperature for 3h;

[0082] The reaction system was filtered to obtain a yellow mud-like product, which was dissolved in an appropriate amount of ethanol and filtered to obtain a reddish-brown filtrate. The ethanol was evaporated off in a vacuum to obtain a crude product. The crude product was then washed with (2×15 mL) deionized water, (2×15 mL) 2M dilute hydrochloric acid, and (2×15 ml) deionized water, and then recrystallized in a mixture of ethanol and water in a ratio of 1:1, vacuum dried, and weighed to obtain 1.45 g of 4,4-dihydroxyazobenzene;

[0083] 4,4-dihydroxyazobenzene (9.104 g, 0.0425 mol), K2CO3 (5.865 g, 0.0425 mol) and 40 mL of DMF were fully dissolved in a 100 mL single-necked flask, and the solution was stirred at 30 °C for 30 min until it was evenly dispersed;

[0084] KI (0.018 g, 0.108 mol) and chloropropanol (4.254 g, 0.045 mol) were added to the solution, and the mixture was vigorously stirred and refluxed at 105 °C in an oil bath for 24 h;

[0085] The reaction solution was cooled to room temperature, dropped into 900 g of crushed ice, and the precipitate was collected by suction filtration. The product was recrystallized twice in 1200 mL of n-hexane, and then vacuum dried at 50° C. for 24 h after recrystallization. 11.775 g was weighed to obtain the final 4-propylhydroxy ether p-hydroxyazobenzene;

[0086] Under stirring at room temperature, 0.05 g of 4-propylhydroxyether-p-hydroxyazobenzene was dispersed in 10 g of dimethyl sulfoxide, 6 g of an aqueous solution of 0.1 g of cellulose nanofibers was prepared, and the solution was added dropwise to the azobenzene solution and stirred at room temperature to obtain a uniformly dispersed solution;

[0087] Add 2.0 g of polyvinyl alcohol with a molecular weight of 47,000, stir continuously, increase the temperature stepwise, and heat the oil bath to 95°C. After the polyvinyl alcohol is completely dissolved, continue stirring at this temperature for 3 h.

[0088] After the reaction is completed, stirring is stopped, and the mixture is allowed to stand in an oil bath to precipitate to remove bubbles generated during the reaction. The mixture is transferred to a 50 mm × 50 mm × 10 mm PTFE mold and placed in a refrigerator at -25°C for 24 hours to obtain an azo gel. The azo gel is immersed in 20 g of 1.5 M KCl salt solution for 24 hours to obtain the final product, an azo ion conductive gel.

[0089] Take two identical conductive gels prepared above, place a polyimide layer in the middle, connect copper electrodes at both ends, and after the connection is completed, use transparent polyimide to entangle and seal to prevent dehydration to obtain a sensor device. The prepared sensor has good sensitivity.

[0090] Within the parameter ranges defined in the present invention, the prepared conductive gels can achieve the technical effects of the present invention, which will not be described in detail here.

[0091] In summary, the present invention proposes a binary solvent system conductive gel with polyvinyl alcohol as the polymer network structure of the gel, cellulose nanofibers / cellulose nanocrystals as nanofillers, and dihydroxyazobenzene as functional groups, which has high stretchability (600%), strong toughness (2.2Mpa), high water retention rate (92%) and good frost resistance (-60°C).

[0092] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing an azo-based ion conductive gel for monitoring human body movement, characterized in that: Prepared using the following raw materials in parts by weight: The monomer A is 4,4-dihydroxyazobenzene or 4-R-hydroxyazobenzene, and R is a C2-C7 alkyl chain; the solvent a is dimethyl sulfoxide or ethylene glycol; The monomer B is cellulose nanofibers or cellulose nanocrystals, and the solvent b is secondary water; The monomer C is M W The polyvinyl alcohol is 47000-195000; the mass ratio of the monomer B to the monomer C is 1:5-100; The salt solution D is sodium chloride, potassium chloride, sodium sulfate or calcium chloride solution with a concentration of 0.5-3.5 mol / L; The above method comprises the following steps: S1: dispersing monomer A in solvent a; S2: Disperse monomer B in solvent b, add dropwise to the above solvent a, and stir to obtain a uniformly dispersed solution; S3: Add monomer C, stir continuously, and heat in an oil bath until monomer C is completely dissolved; S4: After the reaction is completed, the mixture is allowed to stand, transferred to a specific mold, and frozen to obtain an azo gel; S5: Put the azo gel into the salt solution D to obtain the azo ion conductive gel.

2. The method for preparing the azo-based ion conductive gel for monitoring human body movement according to claim 1, characterized in that: The 4,4-dihydroxyazobenzene is prepared by the following steps: (1) adding dilute hydrochloric acid dropwise to a mixed solution of p-aminophenol and deionized water, and performing an ice water bath treatment; (2) preparing a sodium nitrite aqueous solution and adding it dropwise to the above solution; (3) adding deionized water, copper sulfate pentahydrate, ammonia water and hydroxylamine hydrochloride in sequence to form a diazonium salt solution; (4) performing a coupling reaction, slowly adding the solution (3) to the solution (2), removing the ice water bath, and stirring the reaction at room temperature; (5) washing with ethanol, filtering, vacuum evaporation, washing with deionized water, and washing with hydrochloric acid; (6) Ethanol and water are added in a volume ratio of 1:1 and recrystallized to obtain 4,4-dihydroxyazobenzene.

3. The method for preparing the azo-based ion conductive gel for monitoring human body movement according to claim 2, characterized in that: The 4-R-hydroxyazobenzene is prepared by the following steps: (7) potassium carbonate and 4,4-dihydroxyazobenzene prepared according to claim 2 are dissolved in N,N-dimethylformamide and stirred at room temperature; (8) adding potassium iodide and monomer E to the above solution and stirring vigorously in an oil bath; the monomer E is chloro / bromo-R-alcohol, and R is a 2-7 methylene chain; (9) The solution was cooled to room temperature, precipitated with crushed ice, recrystallized with n-hexane, and dried in vacuo to obtain 4-R-hydroxyazobenzene.

4. The method for preparing the azo-based ion conductive gel for monitoring human body movement according to claim 3, characterized in that: The time for adding hydroxylamine hydrochloride in step (3) is 15 minutes, and the addition needs to be slow and even.

5. The method for preparing the azo-based ion conductive gel for monitoring human body movement according to claim 4, characterized in that: The dropping time of step (4) is 2.5h-3.5h.

6. The method for preparing the azo-based ion conductive gel for monitoring human body movement according to claim 5, characterized in that: In the step (8), the oil bath temperature is 105-120° C., and the stirring is magnetic stirring.

7. The method for preparing the azo-based ion conductive gel for monitoring human body movement according to claim 1, characterized in that: In the step S3, the oil bath heating temperature is 80-110° C.; in the step S5, the salt solution immersion time is 24-48 hours.

8. The method for preparing the azo-based ion conductive gel for monitoring human body movement according to claim 7, characterized in that: In the step S4, the freezing temperature is -15 to -25°C, the specific mold is a PTFE mold, and the inner size is 40-80mm×40-80mm×5-30mm.

9. A sensor device for monitoring human body movement, characterized in that: Two identical conductive gels prepared by the method described in any one of claims 1 to 8 are placed with a polyimide tape as a dielectric layer in between, and copper electrodes are connected. After the connection is completed, the polyimide tape is used for entanglement and sealing to prevent dehydration, thereby obtaining a sensor device for monitoring human body movement.

10. An application of the sensor device for monitoring human body movement according to claim 9, characterized in that: Used to measure human finger joint / knee joint signals, human pulse signals, Adam's apple signals when the human body makes different sounds, and light intensity signals.

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