CN112648917A

CN112648917A - Novel flexible sensor capable of detecting human physiological signals based on coffee ring effect and preparation method thereof

Info

Publication number: CN112648917A
Application number: CN202011307732.7A
Authority: CN
Inventors: 胡本慧; 尹思梦; 王金毅; 周宇轩
Original assignee: Nanjing Medical University
Current assignee: Nanjing Medical University
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2021-04-13

Abstract

The invention discloses a novel flexible sensor capable of detecting human physiological signals based on a coffee ring effect and a preparation method thereof. The novel flexible sensor comprises a flexible substrate layer, a strain sensing layer based on a carbon nano tube gradient structure film, a flexible conducting layer and a packaging layer; the detection method of the flexible sensor comprises the following steps: the flexible sensor is attached to the skin of a human body for detection, the flexible conducting layer is connected with the microprocessor or the signal processing device through the flexible metal lead, and when the flexible sensor is stretched and deformed, the resistance value change of the flexible sensor is used as signal transmission data, so that the deformation quantity of the flexible sensor can be reflected with high sensitivity. The invention has excellent stretchability, sensitivity and stability, can effectively overcome the defects of poor flexibility, incompatible sensitivity and stability and the like of the conventional flexible sensor, and can be worn for a long time and monitor the physiological condition of a human body in real time; and the flexible sensor is simple and convenient in preparation process and convenient for large-scale production from the industrial angle.

Description

Novel flexible sensor capable of detecting human physiological signals based on coffee ring effect and preparation method thereof

Technical Field

The invention relates to a flexible sensor, in particular to a novel flexible sensor capable of detecting human physiological signals based on coffee ring effect and a preparation method thereof, belonging to the technical field of sensors or functional materials.

Background

In recent years, flexible electronic sensors gradually become research hotspots and have the characteristics of being light, thin, portable, excellent in electrical performance, high in integration level and the like. As a flexible electronic device for sensing an applied force on a surface of an object, a flexible tensile strain sensor is generally evaluated in performance by three key factors: sensitivity, stretchability and long-term stability.

The carbon nano tube is a tubular object formed by coaxially bending single-layer or multi-layer graphite atoms, has the diameter of one to dozens of nanometers and the length of several micrometers, is a one-dimensional material with high length-diameter ratio and surface volume ratio, has excellent mechanical and chemical properties, electronic properties and biocompatibility, and is selected by scientific researchers as a material for preparing a flexible sensor. At present, a sensor prepared based on a carbon nano tube has the characteristics of high sensitivity and the like, but the compatibility of the high sensitivity and the high stability of the sensor is difficult to realize. Meanwhile, a method with a complex process is mostly adopted to prepare the microstructured device, so that large-scale preparation is difficult, and the application of the microstructured device in reality is limited. Achieving fast response, low cost manufacturing, high sensitivity and stability of flexible sensors remains a significant challenge.

In view of the above, there is an urgent need in the art to develop a flexible sensor that has a simple structure, is easy and convenient to manufacture, and has a rapid response, high sensitivity and stability.

Disclosure of Invention

The invention mainly aims to provide a novel flexible sensor capable of detecting physiological signals of a human body based on a coffee ring effect and a preparation method thereof, so as to overcome the defects in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

a novel flexible sensor capable of detecting human physiological signals based on coffee ring effect is characterized by comprising:

the flexible substrate layer that sets up in proper order stacks, flexible substrate layer and health skin have similar young modulus, can adhere at the health positions such as wrist, neck, and is conformal with skin, follows the tensile state of skin and produces deformation, and is frivolous noninductive.

The strain sensing layer is a thin film based on a carbon nano tube gradient structure. The self deformation degree can be converted into the change of the electrical property, which is mainly reflected in the change of the resistance value.

The flexible conducting layer is formed by adopting a metal evaporation method, and the patterning of the flexible conducting layer is realized by adopting a mask plate method.

The flexible substrate layer has good biocompatibility and allows long-time contact with the skin;

the flexible conducting layer is attached to the flexible substrate layer, the flexible substrate layer pulls the strain sensing layer to deform, and the strain sensing layer is used for detecting the skin stretching condition of the person to be detected.

A preparation method of a novel flexible sensor capable of detecting human physiological signals based on coffee ring effect is characterized by comprising the following steps:

step 1, carrying out fluorination treatment on a substrate;

step 2, generating a flexible substrate layer of the flexible sensor on a substrate;

step 3, preparing uniformly dispersed carbon nano tube dispersion liquid;

4, placing a mask plate on the flexible substrate and carrying out hydrophilization treatment;

step 5, depositing the carbon nanotube dispersion liquid in a hydrophilization treatment area to form a strain sensing layer with certain gradient distribution;

and 6, placing a mask beside the strain sensing layer, and evaporating metal to form a flexible conductive layer. One end of the flexible conducting layer is connected with the strain sensing layer, and the other end of the flexible conducting layer is used as a flexible metal lead connecting part;

step 7, separating the substrate of the flexible sensor from the flexible substrate layer;

and 8, packaging the flexible substrate layer, the strain sensing layer and the flexible conductive layer by using a packaging layer so that the flexible substrate layer, the strain sensing layer, the flexible conductive layer and the packaging layer form a flexible sensor.

The fluorination treatment is carried out on the surface of the substrate, so that the flexible sensor is favorably separated from the substrate without damage.

The material of the flexible substrate layer comprises: and flexible and biocompatible high molecular polymers such as Polydimethylsiloxane (PDMS) and Polyimide (PI).

The material of the strain sensing layer comprises: and (3) carboxyl modified carbon nano tubes.

The sensor is attached to the skin of a human body for detection, the flexible conducting layer is connected with the microprocessor or the signal processing device through the flexible metal lead, and when the flexible sensor is stretched and deformed, the resistance value of the flexible sensor is changed to serve as signal transmission data. The testing method is suitable for physiological data such as human body pulse or voice signals.

In one possible implementation form of the method,

In one possible implementation, the material of the strain sensing layer includes: carboxylated modified single-walled carbon nanotubes (SWCNTs).

The present disclosure forms a flexible sensor by sequentially forming a strain sensing layer and a flexible conductive layer on a flexible substrate layer, and encapsulating the above structure. Because the strain transmission layer is directly formed through the self-assembly effect, the complicated procedures and errors of subsequent integrated devices are avoided, and the preparation efficiency of the flexible sensor is improved. In addition, the flexible sensor disclosed by the invention is made of flexible materials, has strong conformal capability, reduces the influence of measurement to the maximum extent, and is favorable for obtaining more accurate data.

Compared with the prior art, the advantage of this patent includes: the sensor has excellent stretchability, sensitivity and stability, can effectively overcome the defects of poor flexibility and the like of the conventional flexible sensor, and can be worn for a long time and monitor the physiological condition of a human body in real time; and the flexible sensor is simple and convenient in preparation process, saves cost and is convenient for large-scale production from the industrial aspect.

Drawings

FIG. 1 is a flow chart illustrating the preparation of a flexible sensor according to an exemplary embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a novel flexible sensor capable of detecting physiological signals of a human body based on the coffee ring effect according to an exemplary embodiment of the present invention;

FIG. 3 is a schematic view of a reticle in an exemplary embodiment of the invention, the left view being a schematic view of a serpentine reticle and the right view being a schematic view of a rectilinear reticle;

FIG. 4 is a schematic representation of a strain sensing layer in accordance with an exemplary embodiment of the present invention;

FIG. 5 is a partial diagram of resistance change during cyclic stretching of the novel flexible sensor capable of detecting physiological signals of a human body based on the coffee ring effect according to an exemplary embodiment of the present invention;

FIG. 6 is a graph showing the variation of the resistance of the novel flexible sensor for detecting physiological signals of a human body based on the coffee ring effect according to an exemplary embodiment of the present invention;

fig. 7 is a graph showing the change of strain sensitivity of the novel flexible sensor capable of detecting physiological signals of a human body based on the coffee ring effect in an exemplary embodiment of the present invention.

Fig. 8 is a detection method of a novel flexible sensor capable of detecting physiological signals of a human body based on the coffee ring effect in an exemplary embodiment of the invention, which is an example of detection of pulse signal data of the human body.

In the figure: 1. a flexible substrate layer; 2. a strain sensing layer; 3. a flexible conductive layer.

Detailed Description

The present invention will be described in further detail with reference to the following examples in order to clarify technical problems, technical solutions, implementation processes and performance displays.

The embodiment of the invention provides a novel flexible sensor capable of detecting human physiological signals based on a coffee ring effect, which comprises a flexible substrate layer, a strain sensing layer based on a carbon nano tube gradient structure film, a flexible conducting layer and a packaging layer, wherein the flexible substrate layer, the strain sensing layer, the flexible conducting layer and the packaging layer are sequentially stacked; the strain sensing layer is connected with the flexible conductive layer, the strain sensing layer and the flexible conductive layer are arranged on the flexible substrate layer, and the flexible substrate layer, the strain sensing layer and the flexible conductive layer are packaged and protected by the packaging layer.

In one possible implementation, the material of the substrate may include, but is not limited to: silicon (Si) crystals, Polycarbonate (PC) or glass.

In one possible implementation, the material of the flexible substrate layer may include, but is not limited to: and flexible and biocompatible high molecular polymers such as Polydimethylsiloxane (PDMS) and Polyimide (PI). Polydimethylsiloxane (PDMS) is a colorless or pale yellow liquid in a chemical state, and has excellent physical properties. The dimethyl silicone oil is nontoxic and tasteless, and has physiological inertia and good chemical stability. The electric insulation, weather resistance and hydrophobicity are good, the shear resistance is high, and the cable can be used for a long time at the temperature of minus 50 ℃ to 200 ℃.

The invention also provides a preparation method of the novel flexible sensor capable of detecting human physiological signals based on the coffee ring effect, and fig. 1 is a flow chart of the preparation method of the flexible sensor, which comprises the following steps:

step 1, carrying out fluorination treatment on a substrate;

step 3, preparing uniformly dispersed carbon nano tube dispersion liquid;

In some specific embodiments, as shown in fig. 2, which is a schematic structural diagram of a mechanical sensor of a coffee ring formed by carbon nanotubes, the preparation method of the novel flexible sensor capable of detecting physiological signals of a human body based on the coffee ring effect may include the following steps:

as an example of this embodiment, step 1 may include:

the specific process is as follows: and respectively and sequentially soaking the substrate with a proper amount of acetone, ethanol and deionized water, and carrying out ultrasonic treatment for 20min to remove impurities on the substrate. Carrying out fluorination treatment on the substrate, wherein the fluorination treatment comprises the following specific steps: placing the substrate in a vacuum cavity, dropwise adding perfluorooctyl trichlorosilane in the cavity, vacuumizing the vacuum cavity by using a vacuum pump to ensure that the vacuum cavity is filled with fluorinated gas, placing the substrate in the vacuum cavity, and fluorinating for half an hour to ensure that the surface of the substrate forms a functional layer in the vacuum cavity. The functional layer is processed by fluorine gas to form a structure similar to Polytetrafluoroethylene (PTFE), the thickness of the functional layer is about 0.1 to 10 mu m, the texture is compact and firm, and the functional layer has excellent barrier, anti-pollution, abrasion resistance and chemical erosion resistance. And the fluorination treatment is carried out on the surface of the substrate, so that the nondestructive separation of the flexible sensor and the substrate is facilitated.

As an example of this embodiment, step 2 may include: manufacturing a flexible substrate layer of the flexible sensor, mixing Polydimethylsiloxane (PDMS) prepolymer and Polydimethylsiloxane (PDMS) curing agent according to the volume-to-mass ratio of 10:1, and stirring to fully fuse the Polydimethylsiloxane (PDMS) prepolymer and the Polydimethylsiloxane (PDMS) curing agent. Placing the fluoridized substrate on a spin coater, dropwise adding the prepared flexible substrate material, setting the spin-coating speed to be 1000rpm and the spin-coating time to be 60s, placing the spin-coated substrate on a hot plate, setting the temperature to be 80 ℃, and curing for 4 h. A flexible substrate layer of the flexible sensor is obtained.

As an example of this embodiment, step 3 may include: and preparing a carbon nano tube dispersion liquid with uniform dispersion. Dispersing the carboxylated single-walled carbon nanotubes with the diameter of 1-2 nanometers and the length of 5-30 micrometers in deionized water, and carrying out ultrasonic treatment for 3 hours to ensure that the carboxylated single-walled carbon nanotubes are uniformly dispersed. To obtain the carbon nano tube dispersion liquid with even dispersion.

As an example of this embodiment, step 4 may include: and placing the mask plate and the flexible substrate together in a plasma surface treatment instrument for hydrophilic treatment.

As an example of this embodiment, step 5 may include: separating the mask plate and the flexible substrate, dripping the dispersed carbon nano tube dispersion liquid on the part of the flexible substrate subjected to hydrophilization treatment, and standing for several minutes. Under the influence of the self-assembly effect, a strain sensing layer with a certain gradient distribution is formed in the hydrophilized area. Fig. 4 is a physical diagram of the strain sensing layer.

As an example of this embodiment, step 6 may include: a mask is placed beside a strain sensing layer on a flexible substrate layer, and a Chromium (Cr) layer and a Gold (Au) layer are sequentially evaporated to form a flexible conducting layer (2). One end of the flexible conducting layer is connected with the strain sensing layer, and the other end of the flexible conducting layer is used as a flexible metal lead connecting part. As shown in FIG. 3, which is a schematic diagram of the mask with the serpentine structure and the linear structure, a proper mask can be selected for manufacturing the flexible lead according to actual requirements. The flexible conductive layer (2) may be formed by selecting other metal materials (for example, copper, etc.), and the metal materials are not limited as long as the metal materials have good ductility and corrosion resistance.

In a possible implementation mode, the flexible conducting layer is of a snake-shaped structure, the extensibility is enhanced, a stretching space is reserved, the system performance is reduced due to the fact that the flexible conducting layer is not prone to breaking, and the detection accuracy of the strain sensor is improved.

As an example of this embodiment, step 8 may include: the encapsulation is carried out using Parylene (Parylene).

The invention also provides a detection method of the novel flexible sensor capable of detecting the human physiological signal based on the coffee ring effect, which comprises the following steps: and when the flexible sensor is stretched and deformed, the resistance value change data is used as signal transmission data.

The embodiment of the invention also provides the practical application of the novel flexible sensor which can detect the physiological signal of the human body based on the coffee ring effect, and the practical application can comprise the following steps: the flexible sensor is attached to a human body, and the flexible conducting layer is connected with the microprocessor or the signal processing device through the flexible metal lead. When a human body or an animal moves in a small range, the flexible sensor is stretched and deformed, and the resistance value change of the flexible sensor is used as signal transmission data, so that the deformation quantity of the flexible sensor can be reflected at high sensitivity.

The impedance value and the stretch ratio of the sensor have a certain relation, so that the change of the impedance value is adopted to determine the deformation state of the skin, and the change of the impedance value is taken as signal transmission data. The testing method is suitable for physiological data such as human body pulse or voice signals.

Fig. 5 is a partial diagram of resistance value change in the cyclic stretching process of the novel flexible sensor capable of detecting physiological signals of a human body based on the coffee ring effect, and it can be seen from fig. 5 that the sensor has strong uniformity and good recoverability in the cyclic stretching process. Fig. 6 and fig. 7 are a resistance value variation graph and a variation graph of the strain sensitivity of the novel flexible sensor capable of detecting human physiological signals based on the coffee ring effect, respectively. (data are from 4 samples, and each group of data is an average value of 10 times) from fig. 7, it can be seen that the strain sensitivity of the novel flexible sensor which can detect human physiological signals based on the coffee ring effect increases with the increase of the deformation quantity of the sensor. The invention has higher strain sensitivity in the 10% stretchable range, can be applied to measuring the micro stretching deformation of the body surface, and has good clinical application prospect. Fig. 8 is a detection method of a novel flexible sensor capable of detecting physiological signals of a human body based on the coffee ring effect in an exemplary embodiment of the invention, which is an example of detection of pulse signal data of the human body.

The novel flexible sensor capable of detecting the physiological signals of the human body based on the coffee ring effect has a large strain coefficient, can effectively overcome the defects of poor flexibility, poor sensitivity and the like of the conventional flexible sensor, and is simple in production process and convenient for large-scale production.

Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein were chosen in order to best explain the principles of the embodiments, the practical application, or technical improvements to the techniques in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A novel flexible sensor capable of detecting human physiological signals based on the coffee ring effect is characterized in that, comprising: a flexible substrate layer (1), a strain sensing layer (2), a flexible conductive layer (3), an encapsulation layer ( 4); the strain sensing layer (2) is connected with the flexible conductive layer (3), the two are arranged on the flexible substrate layer (1), and the encapsulation layer (4) connects the flexible substrate layer (1). The bottom layer (1), the strain sensing layer (2), and the flexible conductive layer (3) are packaged and protected.

2. The flexible mechanical sensor according to claim 1, characterized in that the flexible substrate layers (1) are stacked in sequence, and can be adhered to body parts such as wrists and necks, and deformed following the stretching state of the skin; The strain sensing layer (2) is a thin film based on a carbon nanotube gradient structure; the patterning of the strain sensing layer (2) and the flexible conductive layer (3) is realized by a mask method.

3 . The flexible mechanical sensor according to claim 1 , wherein the flexible substrate layer ( 1 ) has a similar Young's modulus to the body skin, can be conformally attached to the skin, and is generated with the stretching state of the skin. 4 . deformation, light, thin and non-inductive, and has good biocompatibility; the strain sensing layer (2) and the flexible substrate layer (1) are attached and arranged, and the flexible substrate layer (1) drives the strain sensing layer ( 2) Deformation occurs. The strain sensing layer realizes the following functions: transforming the degree of its own deformation into a change in electrical characteristics, which is mainly reflected in a change in resistance value.

4. A preparation method of a novel flexible sensor that can detect human physiological signals based on coffee ring effect, is characterized in that, comprises the following steps:

Step 1: carry out fluorination treatment to the substrate;

Step 2: the flexible substrate layer (1) of the flexible sensor is generated on the substrate;

Step 3: make a uniformly dispersed carbon nanotube dispersion;

Step 4: place a mask on the flexible substrate and carry out a hydrophilization treatment;

Step 5: depositing a carbon nanotube dispersion in the hydrophilization treatment area to form a strain sensing layer (2) with a certain gradient distribution;

Step 6: a mask is placed beside the strain sensing layer (2), and metal is evaporated to form a flexible conductive layer (3). One end of the flexible conductive layer (3) is connected with the strain sensing layer (2), and the other end is used as a connection part of the flexible metal lead;

Step 7: separating the substrate of the flexible sensor and the flexible substrate layer (1);

Step 8: Encapsulating the flexible substrate layer (1), the strain sensing layer (2), and the flexible conductive layer (3) with an encapsulation layer (4), so that the flexible substrate layer (1) , the strain sensing layer (2), the flexible conductive layer (3) and the encapsulation layer (4) constitute a flexible sensor.

5 . The preparation method of a novel flexible sensor based on coffee ring effect that can detect human physiological signals according to claim 5 , wherein fluorination treatment is performed on the surface of the substrate, which is beneficial to the flexible sensor and the said flexible sensor. 6 . Non-destructive separation of substrates.

6. The preparation method of a novel flexible sensor that can detect human physiological signals based on the coffee ring effect according to any one of claims 5 to 6, wherein the material of the flexible substrate layer (1) comprises: : Flexible and biocompatible polymers such as polydimethylsiloxane (PDMS) or polyimide (PI).

7. The preparation method of a novel flexible sensor capable of detecting human physiological signals based on the coffee ring effect according to claim 5, wherein the material of the strain sensing layer (2) comprises: carboxylated modified carbon nanotubes.

8. The preparation method of a novel flexible sensor capable of detecting human physiological signals based on the coffee ring effect according to claim 5, characterized in that: the flexible conductive layer (3) is a serpentine structure, when the novel flexible sensor When deforming, reserve the stretching space, which is not easy to break and cause the performance of the system to decline.

9. The preparation method of a novel flexible sensor capable of detecting human physiological signals based on the coffee ring effect according to claim 5, characterized in that: the strain sensing layer (2) and the flexible conductive layer (3) ) The patterning is realized by the method of reticle.

10. The preparation method of a novel flexible sensor based on the coffee ring effect that can detect human physiological signals according to claim 5, wherein the novel flexible sensor is attached to human skin for detection, and the novel flexible sensor is When the flexible sensor is stretched and deformed, the change of its resistance value is used as the signal transmission data, which can reflect the deformation amount of the flexible sensor with high sensitivity. This test method is suitable for physiological data such as human pulse or voice signal.