KR20170009081A - Bio-signal measuring sensor using pla piezoelectric material of nanofiber web type by electrospinning - Google Patents

Abstract

The present invention relates to a biometric signal measurement sensor. More specifically, a polylactic acid (PLA) is electrospun to manufacture a piezoelectric PLA material realized in the form of a nanofiber web. By folding the nanofiber web two or more times, the top parts of the nanofiber web are made to face each other while the bottom parts of the nanofiber web face each other, thereby forming a folding type PLA nanofiber web. The folded layers of the folding type PLA nanofiber web are connected to a flexible parallel electrode unit. The folding type PLA nanofiber web connected to the flexible parallel electrode unit is inserted into a body pressing unit made of an elastic band to generate a piezoelectric signal by being expanded or contracted by receiving pressure from the body pressure unit expanding or being contracted during breathing or exercise operations as well as measuring biometric signals. Accordingly, the biometric signal measurement sensor uses the piezoelectric PLA sensor in the form of a nanofiber web electrospun to be prepared at a low cost by using the polylactic acid.

Description

TECHNICAL FIELD [0001] The present invention relates to a bio-signal measurement sensor using a PLA piezoelectric material of a nanofiber web type obtained by electrospinning. [0002] The present invention relates to a biosignal-

The present invention relates to a bio-signal measuring sensor, and more particularly, to a PLA piezoelectric material, which is formed by electrospinning a poly-lactic acid to form a nanofiber web, Folded PLA nanofiber web is formed by folding at least two times so that the bottom portion and the bottom portion of the folded PLA nanofiber web are facing each other, And the folded PLA nanofiber web in which the flexible parallel electrode portion is connected is inserted into a body pressing portion made of an elastic band and expanded or contracted under the pressure of the body pressing portion which expands or contracts during breathing or exercise By generating a piezoelectric signal to measure a living body signal, it is possible to make a low-cost production using polylactic acid, No fiber web relates to the form of the bio-signal measuring sensor using a piezoelectric sensor PLA.

As interest in health care has increased recently, there has been an increasing interest in health management, which can manage health status through active physical activities such as regular exercise. In order to perform such health management, a smart sensor equipped with a sensor capable of continuously measuring respiration or pulse waves during daily life or exercise, or a sensor capable of continuously measuring the motion of a muscle to calculate the degree of motion Research and development of clothing are being carried out.

Accordingly, as disclosed in Korean Patent No. 10-1023446, the inventors of the present invention have found that two elastic bands, which cause a change in length depending on the number of respiratory or heartbeats, and the elastic bands inserted between these two elastic bands, There has been proposed a breathing apparatus or a heart rate measuring apparatus including a piezoelectric polymer layer causing a change in length and an electrode layer transmitting an electrical signal generated by a change in length of the piezoelectric polymer layer.

In addition, as disclosed in Korean Patent No. 10-1384761, the applicant of the present invention has an electrocardiogram measuring unit composed of a dry electrode and a respiration measuring unit composed of a piezoelectric sensor capable of recognizing the expansion and contraction of the chest during breathing, A sports bra capable of simultaneous measurement of breathing and electrocardiogram which enables simultaneous measurement of ECG signal and breathing behavior during daily life or exercise by wearing a bra.

Also, as disclosed in Korean Patent No. 10-1331858, the present applicant has proposed an elastic fastening band and a piezoelectric sensor in a pant, such as a training suit, so that when wearing a smart pant and walking or running, the thigh muscles We have proposed a smart pants that can measure motion signals of muscles that can confirm the degree of motion by movement.

1 (a) shows a PVDF film sensor and a physiological sensing belt (PSB) suggested by the present inventor, and FIG. 1 (b) shows a schematic cross-sectional structure when the physiological sensing belt PSB is worn . The PSB sensor as shown in FIG. 1 was developed by the present inventor in order to study breathing and muscle movements. The piezoelectric signal generated in the PVDF film placed between the electrodes having excellent sensitivity is used for breathing and muscles of the wearer of the PSB sensor To detect motion.

However, as described above, the piezoelectric polymer layer, the respiration measuring unit, or the piezoelectric sensor proposed by the present inventors and applicants of the present invention have a piezoelectric means for generating a piezoelectric signal by a stretching action that occurs during breathing or motion is polyvinylidene fluoride, (PVDF) and polymers thereof (for example, PVDF-TrEE), and it has been proposed that a number of smarts In the case of mass production to be applied to clothing, the initial investment cost for manufacturing a piezoelectric material capable of generating a piezoelectric signal has increased to a considerable extent, and this increase in cost can be measured by breathing or exercise Which is a limitation of various attempts to apply the sensor to various smart apparel. There was a point.

In order to reduce the cost of manufacturing a piezoelectric material by using a polymer piezoelectric material such as PVDF and the polymer, many researchers have recently been interested in the piezoelectric properties of polylactic acid (PLA) as an alternative means, Many researchers have already compared the piezoelectric properties of PLA films with those of PVDF films. The present inventors have also studied a PLA stretched film and a PLA nanofiber web as means for replacing the PSB sensor realized with an expensive PVDF film.

In general, polylactic acid (PLA) has a spiral chain structure and is known as a crystalline phase, which is the most stable thermally at room temperature. Such a crystalline form can be easily obtained by forming a film by melting or solution method have. However, the PLA film obtained by this method has a net dipole moment of zero because the C = O dipole group is randomly oriented in all directions (360) along the main chain, and does not exhibit piezoelectric properties.

However, when this -crystallized PLA film is stretched in a uniaxial direction at a high stretching ratio and / or a high temperature, it can be converted into a -crystal having a loose 3 ₁ helical structure along the polymer chain. The C = O dipole group is still oriented in all directions (360) along the main chain until this time, but the PLA film converted to this -type crystal exhibits shear piezoelectricity under external pressure.

Unlike the PVDF film, which requires a polarization process to align the CF dipoles along the direction of polarization in order to exhibit piezoelectric properties, uniaxially stretched PLA films can exhibit shear piezoelectric properties without such a polarization process do. Although the C = O dipole can not rotate easily due to the strong interaction between the helical structures in PLA, the -shaped helical structure formed by the stretching effect has a weaker interaction force than the -shaped helical structure, It can be seen that the shear stress effect is a way to switch the PLA spiral structure. As in FIG. 2, the helical structure is distorted by shear stress, and with such a change the C = O dipole sum becomes non-zero, thereby allowing the PLA sample to generate a piezoelectric signal with respect to external pressure. What can be expressed as the maximum piezoelectric property is called the shear piezoelectric property and is defined as d _14. This is because when the film produced by uniaxial hot rolling in the direction 3 is deformed by the external force applied in the fourth direction (diagonal direction) Means that the signal is generated in the first direction (thickness direction) (see FIG. 3).

There have been attempts to use PLA as an alternative means of realizing piezoelectric characteristics without using expensive PVDF. However, conventionally, instead of using PLA itself as a piezoelectric material, other inorganic piezoelectric materials (such as PZT) However, such a problem has been difficult to apply PLA as a means of replacing PVDF.

Korean Patent No. 10-1023446 Korean Patent No. 10-1384761 Korean Patent No. 10-1331858

The present invention relates to a PLA piezoelectric material that is electrospun poly Lactic Acid and is realized as a nanofiber web, and a top portion and a top portion of the nanofiber web are disposed opposite to each other, folded PLA nanofiber web is formed by folding at least two times so that the bottom portion of the folded PLA nanofibrous web faces each other and then the flexible parallel electrode portion is connected to each folded layer of the folded PLA nanofibrous web, Folded PLA nanofiber web is inserted into a body pressing part made of an elastic band and expanded or contracted under the pressure of the body pressing part that expands or contracts during breathing or exercise to generate a piezoelectric signal, To provide a biosignal measurement sensor using a PLA piezoelectric sensor in the form of a nanofiber web obtained by electrospinning, Will.

In order to solve the above-mentioned problems, a bio-signal measurement sensor using a PLA piezoelectric sensor in the form of a nanofiber web obtained by electrospinning,

A body pressing part composed of two elastic bands expanding or contracting with the movement of the body while pressing the body part in which movement occurs during breathing or exercise and forming an insertion space between the two elastic bands; A first folding part folded to face the top part and a top part of the nanofiber web produced by electrospinning polylactic acid (PLA), a bottom part and a bottom part, A second folding section folded to face each other with mutual opposing faces, a folded PLA nanofiber web folded to be alternately stacked; The PLA nanofibrous web according to the present invention comprises a folded PLA nanofibrous web and a folded PLA nanofibrous web. The folded PLA nanofibrous web has a bottom and a top, A flexible parallel electrode unit receiving a piezoelectric signal generated in a folding type PLA nanofiber web that is stretched together; And a shield signal transmission line connected to the flexible parallel electrode unit and transmitting a piezoelectric signal, which is an electrical signal generated from the folding type PLA nanofibrous web, to a control unit.

At this time, 80% or more of the monomers constituting the polylactic acid (PLA) are composed of one kind of isomer selected from L-isomer or D-isomer.

The folded PLA nanofiber web is formed by folding the nanofiber web formed by electrospinning at least twice so that the same faces face each other.

The flexible parallel electrode unit may include:

A first electrode connected to a bottom portion of the folded PLA nanofibrous web, the bottom portion of the folded PLA nanofibrous web being located in a space between the at least one second folded portions; And a second electrode connected to a top portion of the folding PLA nanofibrous web and disposed in a space between the stacked first folding portions, Are electrically connected to each other.

The flexible parallel electrode unit may further include an elastic layer surrounding the entirety of the folding PLA nanofibrous web, and the elastic layer may be formed of silicone rubber.

The present invention can realize a piezoelectric material which can exhibit a piezoelectric characteristic superior or similar to that of a conventional PVDF piezoelectric material at a very low cost. Therefore, it is an object of the present invention to provide a piezoelectric material having various forms such as smart clothing and smart band It can be easily applied to the product, and the cost burden for mass production of such smart clothing and smart band can be significantly reduced.

Further, the present invention can be implemented much thinner and more flexible than the PLA film, and the PLA chains can be effectively aligned along the electric field direction by the high DC voltage applied to the electrospinning, Can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a conventional PVDF film sensor and a physiological sensing belt (PSB) (a) and a cross section (b) when a PSD with a PVDF film inserted is worn on the body.
Fig. 2 is an exemplary diagram illustrating a phenomenon in which a PLA chain structure is twisted by shear pressure. Fig.
Fig. 3 is an example showing polarization caused by shear pressure in a uniaxially stretched PLA film. Fig.
4 is a cross-sectional view of a bio-signal measurement sensor using a PLA piezoelectric material in the form of a nanofiber web obtained by electrospinning according to the present invention.
FIG. 5 is a cross-sectional view showing a state in which a PLA piezoelectric material in the form of a nanofiber web is laminated in various layers according to the present invention, in which (a) is a constructive / destructive laminate, (b) (D) a parallel electrode connection structure capable of lighting LEDs.
6 is an FE-SEM image of a PLA piezoelectric material obtained by electrospinning a nanofiber web obtained according to the present invention at different magnifications ((a) 2000 ×, (b) 5000 × and (c) 100000 ×).
Figure 7 is an image showing the cutting angle applied to produce a PLA stretched film according to one embodiment of the present invention.
FIG. 8 is a view showing the dimensions and structure of a bio-signal measuring sensor (PSB sensor) coated with silicone rubber according to an embodiment of the present invention.
FIG. 9 is a schematic view showing that a piezoelectric signal is generated by periodic external pressure applied to a bio-signal measurement sensor according to the present invention; FIG.
10 is a graph showing the ATR-IR spectrum of a silicon rubber (a) and a PLA piezoelectric material (b) in the form of a nanofiber web obtained by electrospinning.
11 is a graph showing ATR-IR spectra of unstretched PLA film, uniaxially stretched (x 5) PLA film and pure PLA nanofiber web at MD position (a) and TD position (b) according to the present invention.
12 is a graph showing the results of a comparison of the elongation curves (DR = (a) 1, (b) 2, (c) 3, A graph (h) showing the dynamic pressure test signal of the PLA stretched film and V _{p - p} for DR (R _in = 1 GΩ, Gain = 0 dB).
Figure 13 shows PLA stretching (DR = 5) prepared with various cutting angles (a) 0 °, (b) 30 °, (c) 45 °, (d) 60 ° and (e) Measuring human respiration with PSB sensor of film (R _in = 1 GΩ, Gain = 20 dB).
14 is a dynamic pressure test (R _in ) of a piezoelectric material made of a pure PVDF nanofiber web (a) obtained by electrospinning and a pure PLA nanofiber web (b) = 1GΩ, Gain = 0dB) signal.
15 is a view showing the constructive and destructive lamination effect of the PVDF nanofiber web (a) and the PLA nanofiber web (b) obtained by electrospinning.
16 is a graph showing the relationship between the piezoelectric signal (R _in (a), (b)) and the PLA nanofiber web ( = 1 GΩ, Gain = 0 dB).
17 shows V _{p -p} according to the piezoelectric signal and lamination number generated in PLA nanofiber webs constructively laminated with multiple layers ((a) 1, (b) 3, (c) 5 and (d) 8 layers) Graph (e) (R _in = 1 GΩ, Gain = 0 dB).
Simple folding as in Figure 18 at (c) in Fig. 5 (a), serial connection, the folding of the electrode _{(R in = 1GΩ, Gain =} 0dB) (b) and the parallel connection folding of the electrode (R _in = 100MΩ, Gain = 0 dB) (c) A graph showing a piezoelectric signal of one 5-layer PLA nanofiber web.
19 is a graph comparing generation currents according to the structure of three types of folding (simple folding, series connection folding of electrodes, and parallel connection folding of electrodes).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

4 is a cross-sectional view of a bio-signal measurement sensor using a PLA piezoelectric material in the form of a nanofiber web obtained by electrospinning according to the present invention.

Referring to FIG. 4, the bio-signal measurement sensor using the PLA piezoelectric material of the nanofiber web type obtained by electrospinning according to the present invention may be applied to a living body, A body pressing section 100 composed of two elastic bands for shrinking and forming an insertion space between two elastic bands, a nanofiber web produced by electrospinning polylactic acid (PLA) a folded PLA nanofibrous web 200 (hereinafter referred to as " folded PLA nanofibrous web ") is folded such that a top portion and a top portion are mutually opposed and a second folded portion is folded so that a bottom portion and a bottom portion are opposed to each other. ), A body pressing part connected to a bottom part of the folded PLA nanofibrous web and a top part of the upper surface, and expanding or contracting due to movement of the body part generated during breathing or movement, A flexible parallel electrode unit 300 receiving a piezoelectric signal generated in the folding type PLA nanofiber web under pressure and being stretched together; and a flexible parallel electrode unit 300 connected to the flexible parallel electrode unit to generate an electrical signal And a shield signal transmission line 400 for transmitting the piezoelectric signal.

The body pressing unit 100 is composed of an elastic band that presses the body part so as to detect a change of the body necessarily accompanied by breathing or exercising. When the breathing is to be measured, the elastic body is wrapped around the chest area And an elastic band surrounding the thigh when measuring the degree of motion of the thigh.

The body pressing unit 100 includes a first band 110 for covering and pressing the whole of a body part for detecting a change in the body, a second band 110 disposed on an upper surface of the first band, A second band that expands or contracts with the first band due to expansion or contraction of a body part generated during physical activities such as breathing or exercise, (120).

Accordingly, the second band 120 is fixed to the first band 110 in three rims like the PSB sensor shown in FIG. 1, and the remaining one rim portion is kept open , And the folding type PLA nanofiber web 200 can be inserted or separated.

In this case, the first band 110 may be constituted by independent bands as shown in FIG. 1, so that a user who wants to use the bio-signal measurement sensor according to the present invention can be directly worn on the body part, As described in the prior registration patents of the present applicant, a smart garment is manufactured in a state where the first band is provided on a specific area of a sports bra or a training suit, and the second band is installed on the upper side of the smart band, Of course.

The folded PLA nanofibrous web 200 and the flexible parallel electrode unit 300 are inserted into the insertion space formed between the first band 110 and the second band 120, The PLA nanofibrous web 200 is pressurized by the change of the body necessarily accompanied by the movement of the PLA nanofiber web 200, thereby generating a piezoelectric signal to measure the degree of breathing or exercise.

The folded PLA nanofiber web 200 is formed by folding the nanofiber web formed by electrospinning polylactic acid (PLA), which is an environmentally friendly polymer having excellent biodegradability and biocompatibility, so that the same faces face each other at least twice And is formed in a laminated form.

The polylactic acid (PLA) is a material that many researchers are interested in as an alternative means of replacing conventional polymer piezoelectric materials such as polyvinylidene fluoride (PVDF) and its polymers (for example, PVDF-TrFE) , The piezoelectric properties of this polylactic acid (PLA) are exhibited by asymmetric molecular structures in which atoms exhibit unique and independent electrical properties in all directions around carbon atoms.

At this time, it is preferable that at least 80% of the monomers constituting the polylactic acid (PLA) are composed of one kind of isomer selected from L-isomer or D-isomer. Lactic acid, which is a monomer of PLA, is an optical isomer and has two forms of L-isomer and D-isomer (see Chemical Formula 1). PLA consisting of L- The isomeric PLA is referred to as PDLA (see Chemical Formula 2). In the present invention, the purity of each isomer greatly influences the piezoelectric properties of PLA, and it is necessary for any isomer to exhibit piezoelectric properties that 80% or more of the monomers of total PLA are composed of one kind of isomer. More preferably 90% or more, more preferably 95% or more, and most preferably 98% or more of the total monomers of PLA. As a result of studying the piezoelectric properties of PLA and electrospun materials of piezoelectric inorganic particles, it was found that the piezoelectric properties were not observed in the pure PLA material used as the control group. This result is probably due to the fact that the isomer is not considered see.

[Chemical Formula 1]

(2)

Accordingly, the folded PLA nanofiber web 200 is prepared by electrospinning a spinning solution in which PLA, which is composed of at least 80% of the total monomers, is dissolved in a solvent, and the nanofibers are randomly assembled to contain pores Nanofiber webs. ≪ / RTI >

Preferably, the solvent is a mixed solution of chloroform and dimethylacetamide, and the chloroform and dimethylacetamide are mixed in a volume ratio of 2: 1 to 4: 1. By weight to 20% by weight. According to these conditions, a PLA nanofiber web having excellent effects can be produced more readily.

As shown in FIG. 6, the folded PLA nanofiber web 200 has a pore structure, and the folded PLA nanofiber web 200 has a pore structure. It is possible to generate a piezoelectric signal when the pressure is applied or removed. 6 is a graph showing the results of FE analysis of a pure PLA nanofiber web obtained by electrospinning a 9 wt .-% PLA solution at a different magnification ((a) is 2 k ×, (b) is 5 k × and (c) -SEM displays an image. Although subsequent studies have shown that smaller nanoscale (5-15 nm diameter) fibers take up a higher proportion, the optimal electrospinning conditions established in this study allow relatively uniform electrospinning of a 100 nm diameter scale It was confirmed that pure PLA nanofiber was produced. It is believed that exhibiting a uniform shape without lumps is due to optimization of electrospinning conditions such as electrospinning voltage, relative viscosity, solvent, solution concentration and TCD distance of the electrospinning chamber.

The PLA nanofiber web formed by such electrospinning is folded at least twice so that the same faces face each other so as to realize a folding type laminated in a folded state as shown in FIGS.

At this time, when the PLA nanofiber web is laminated, the top and bottom portions of the PLA nanofiber web may be sequentially stacked while being in contact with each other like the Constructive laminate shown in FIG. 5 (a) However, in order to obtain a more enhanced piezoelectric signal, one nanofiber web connected like the destructive laminate shown in FIG. 5 (a) faces the bottom portion and the bottom portion, And the top portion are also folded so as to face each other so that the region where the bottom portion faces and the region where the top portion faces are sequentially stacked alternately.

Accordingly, the folding PLA nanofibrous web 200 is destructively laminated and has a first folding portion 210, which is a region where the top portion of the PLA nanofiber web is opposed to the first folding portion 210, The second folding part 220, which is the area where the bottom part of the bottom surface of the first folding part 220 is opposed to the first folding part 220, are stacked alternately.

Since the folding PLA nanofibrous web 200 in which the first folding unit 210 and the second folding unit 220 are alternately stacked is composed of a conductive fabric, when the pressure is applied, the first and second Even when the folding section is pressed and folded, the piezoelectric film can be restored to the original state at the time of removing the pressure, so that the piezoelectric signal can be continuously generated.

The flexible parallel electrode unit 300 is connected to the upper and lower surfaces of the folded PLA nanofibrous web, and the thickness of the folded PLA nanofibrous web generated when the flexible parallel electrode unit 300 is compressed or restored by external applied pressure A first electrode (310) formed of a conductive material capable of transmitting a piezoelectric signal, which is an electrical signal generated due to the change, to the signal transmission unit and attached to the bottom surface of the folding PLA nanofibrous web; And a second electrode 320 attached to an upper surface of the web.

The first electrode 310 and the second electrode 320 may be attached to each other as shown in FIG. 5C as a 'simple folded shape' or a 'folded shape in which electrodes are connected in series' The first electrode and the second electrode are provided on the lowermost surface and the uppermost surface of the folded PLA nanofibrous web 200 in a folded state, respectively, as shown in FIG. The first electrode 310 and the second electrode 320 may be disposed on the bottom and top surfaces of the folded PLA nanofibrous web 200.

The first electrode 310 is disposed on the bottom surface of the folded PLA nanofibrous web 200 and the folded PLA nanofibrous web is folded to form a folded second folding unit 220 The second electrode 320 is disposed on the uppermost surface of the folded PLA nanofibrous web 200 and the upper surfaces of the folded PLA nanofibrous web are connected to each other. And is inserted into the space between the first folding units 210 folded to face each other.

The flexible parallel electrode unit 300 includes a first electrode 310 connected to the bottom portion of the folded PLA nanofibrous web and disposed in a space between the at least one second folding unit 310, And a second electrode 320 connected to a top portion of the folding PLA nanofibrous web and disposed in a space between the first folding portions, And electrodes electrically connected to each other are electrically connected to each other.

Accordingly, when the first and second bands 110 and 120 are inflated according to the expansion of the chest or the expansion of the muscles involved in the exercise in breathing with the bio-signal measurement sensor according to the present invention, The folded PLA nanofibrous web 200 in which the second folding units 210 and 220 are alternately stacked is expanded by squeezing and each of the stacked layers is also squeezed to narrow the gap between the first and second folding units, The second electrode 320 and the first electrode 310 inserted in the space between the folded PLA nanofibrous web 2 and the folded PLA nanofibrous web 2 are brought into contact with the bottom surface and the top surface of the folded PLA nanofibrous web 2,

Therefore, rather than acquiring piezoelectric signals only on the top and bottom surfaces of the PLA nanofiber web in a collapsed state, the PLA nanofibrous web can be folded by pressure and expansion applied during breathing or exercise, (I.e., a region formed by the piezoelectric film), so that a stronger piezoelectric signal can be obtained.

4, the shielding signal transmission line 400 is connected to the first electrode 310 and the second electrode 320, one end of which is a flexible parallel electrode unit, and the other end is connected to the first electrode 310 and the second electrode 320, (Not shown) to measure the degree of respiration or movement of an electrical signal, which is a piezoelectric signal generated in the folding type PLA nanofiber web by the movement of the body accompanied by the movement of the body during breathing or exercise. To the control unit.

The shielding signal transmission line 400 may be composed of a simple conductor for transmitting an electrical signal, a conductor made of a conductor for transmitting an electrical signal, and an insulation layer / a shielding layer / So that the electrical signal to be transmitted is minimally affected by the noise of the surroundings.

The elastic layer 500 may further include an elastic layer 500 surrounding the entirety of the folded PLA nanofibrous web provided with the flexible parallel electrode section. The elastic layer 500 is preferably made of silicone rubber. When the elastic layer is wrapped with the elastic layer, movement of the body accompanied by biological activities such as breathing and exercise can be more easily transmitted to the folding PLA nanofiber web, and the folding PLA nanofiber web It is possible to protect the web, thereby improving durability.

Next, an experiment for analyzing piezoelectric characteristics in which an electrical signal is generated when a pressure is applied using a bio-signal measurement sensor using PLA piezoelectric material of the nanofiber web type obtained by electrospinning according to the present invention will be described. In this case, in order to confirm the excellent piezoelectric effect of the PLA piezoelectric material of the nanofiber web form obtained by electrospinning, the measurement values of the PSB sensor constituted by the PVDF film and the bio-signal measurement sensor constituted by the PLA film And the PSB sensor is used in combination to refer to a bio signal measurement sensor.

Example  1. Manufacture of piezoelectric material and bio-signal measurement sensor

1-1. material

In this embodiment, PLA 4032D (MW = 195,000) purchased from NatureWorks, USA was used. A polarized PVDF film sensor (DT2-052) with electrodes (thickness 52 μm, width 4 mm, length 30 mm) on the top and bottom layers was purchased from Measurement Specialties Inc. to measure the respiration signal compared to conventional piezoelectric materials Respectively. A silicone elastomer base and a silicone elastomer curing agent (Sylgard® 184A and 184B, Dow Corning, Korea) were used in the silicone coating process to enhance the frictional force of the elastic fabric bands while protecting the film or nanofiber webs. Chloroform (CF) and dimethylacetamide (DMAc) were purchased from Sigma-Aldrich Korea and used as a solvent for making electrospinning solution. A nickel-copper plated polyester fabric (J.G. Korea Inc., Korea) with an adhesive side on one side was used as the electrode for the piezoelectric material.

1-2. PLA  Manufacturing process

1-2-1. PLA  shorten Stretching  film

The PLA chip was dried in a vacuum state at 100 DEG C for 6 hours, and a PLA film was produced using an injection machine installed in KITECH (Korea Institute of Industrial Technology). Table 1 shows the temperature of each injector section. Prior to lapping, air was blown to 130 DEG C to increase the width of the film. The injected PLA films were stretched at different ratios in a hot chamber using an Instron 占 tensile testing machine from FITI (Korea). First, the PLA film was fixed to a holder and held in a hot chamber at 80 DEG C for 15 minutes to achieve a thermal equilibrium state. Then, various elongation ratios (DR: 2, 3, 4, 4.5, 5, and 5.5) To stretch the PLA film.

Barrel 1 Barrel 2 Barrel 3 Barrel 4 Adapter Spin block Pack body Air knife 220 ℃ 240 ℃ 240 ℃ 240 ℃ 240 ℃ 240 ℃ 240 ℃ 130 ℃

- Set temperature condition of each section of injector -

1-2-2. Electrospun nanofiber web

PLA solution was dissolved in a mixed solvent of chloroform (CF): dimethylacetamide (DMAc) (3: 1 v / v) at 9 wt% (w / v) to prepare a pure PLA solution for electrospinning. First, DMAc was added to completely dissolve PLA in CF and to eliminate some difficulties in electrospinning using only PLA and CF solution. 6 mL of the PLA solution was placed in a syringe and electrospun under the following conditions: needle type 18G, flow rate 1.5 cc / h, voltage 12 kV, tip-to-collector distance (TCD) Speed 80rpm.

1-3. Manufacture of bio-signal measurement sensor

1-3-1. PSB sensor

Three types of PSB sensors were used: conventional PVDF film, PLA stretched film, and PLA nanofiber web-based PSB sensor. In the case of the PLA stretched film, the elongation (DR) and the cutting angle were varied (Table 2). As a result of the dynamic pressure test, the PL 5 stretched film of DR 5 exhibited the maximum piezoelectric generation signal for external pressure periodically applied under the same conditions and was used to cut the DR 5 PLA film at different angles as in FIG. The PLA nanofiber web based PSB sensor was fabricated in the same dimensions as in FIG. The silicone rubber coating was prepared as follows: a silicone elastomer base (Sylgard® 184A) and a carbon black paste (10: 1 w / w) were mixed and a silicone elastomer curing agent (10 wt .-% of silicone elastomer base) was added. The mixture was placed in a vacuum desiccator for 20 minutes to remove air bubbles that could accumulate during the mixing process. This solution was spread as thin as possible on a glass plate, then placed in a heated air oven and held at 60 ° C for 30 minutes to cure. The sensor was placed on a hard rubber and then placed in an oven and held at 60 ° C for 30 minutes. The thickness of the entire sensor including the silicone rubber layer was maintained at about 1.5 mm.

Condition 1
: DR 2 3 4 4.5 5 5.5 Condition 2
: Cutting angle 0 ° 30 ° 45 ° 60 ° 90 ° -

1-3-2. Biomedical Signal Measurement Sensor

Different DR PLA stretched films and PLA nanofiber webs were used to fabricate bio-signal measurement sensors. The top and bottom electrodes were prepared as follows: a nickel-copper plated polyester conductive fabric with one side adhered and rounded was attached to both sides of the PLA sample, and finally the bio-signal measurement sensor was bonded with a transparent adhesive I wrapped it in tape. To confirm the specific DR of the PLA film exhibiting a maximum peak-to-peak voltage ( V _pp ), an initial piezoelectric measurement of the PLA film was performed and this PLA stretched film was used in the subsequent PSB sensor production. In the case of the PLA nanofiber web, the sensors were fabricated with different structures as shown in FIG.

Experimental Example 1. Characteristic Analysis of Piezoelectric Material and Biosignal Sensor

1-1. Experimental Method

1-1-1. Field emission-scanning electron microscopy (FE-SEM)

An FE-SEM device (LEO SUPRA 55, Carl Zeiss Inc., USA) was used to observe the shape of the pure PLA nanofiber web.

1-1-2. Attenuated total reflectance infrared (ATR-IR) spectroscopy

The ATR-IR is useful for obtaining information about the chain direction, physical location and structure of thick film samples, and is impossible to measure using other conventional transmission IR modes or grazing incidence reflective absorption modes. In this study, ATR-IR was measured at a resolution of 100 cm 4 cm ^-1 using an FTIR spectrophotometer (IFS 66V, Bruker) containing a diamond crystal accessory (GladiATR ^™ , PIKE). Before measurement, sample positions (MD (machine direction), TD (cross direction) and polarization direction (TE (cross electrical) mode and TM (cross magnetic) mode) were converted and data was recorded using OPUS software.

1-1-3. Measure piezoelectric and PSB signals

The V _pp calculated using a self-fabricated dynamic pressure device was measured. Piezoelectric signal generated by periodic external pressure sensor was transferred to Piezo Film Lab Amplifier with voltage mode set to 1GΩ R _in . The signal was then stored on the PC via the NIDAQ board. To detect the piezoelectric signal, a sinusoidal pressure of 1 kgf at 0.5 Hz was applied to the bio-signal measurement sensor.

1-2. Experiment result

1-2-1. ATR-IR analysis

As in FIG. 10 (a), the isotropic silicone rubber showed a very large TM mode spectral absorbance over the entire wavelength range (i.e., A _TE < A _TM < 2 A _TE ). On the other hand, the TM mode spectrum of a PLA electrospun nanofiber web showed that A _TM is not greater than A _TE , rather that A _TM is less than A _TE overall, which is due to the high electric field applied in the electrospinning process, Orientation and / or C = O and COC dipole orientation are present along the nanofiber orientation. Additionally, in order to compare the degree of orientation according to the difference made by different methods (unstretched PLA film, PLA film stretched at DR = 5 and PLA nanofiber web), PLA film The ATR-IR spectrum of the sample was measured (Fig. 11). PLA stretched film and nanofiber web while representing the uniform chain orientation characteristics, PLA films are not stretched was found that the absorption spectrum is much larger than the overall A _TM yi A _TE as that observed in the case of silicon rubber. In the case of the stretched PLA film, no special peak change was observed in the TE and TM modes when the sample was placed at the TD position. However, changing the sample to the MD position resulted in significant changes in the COC symmetry (1044 cm ^-1 ) and asymmetric stretching (1178 cm ^-1 ) bands in the TE mode. This is thought to be due to the PLA main chains arranged parallel to the sample surface according to the stretching effect. In the case of nanofiber webs, the C = O stretching band at 1751 cm ^-1 as well as the COC symmetric and asymmetric stretching bands exhibited stronger absorbance than the stretched film, regardless of the location (MD or TD) at which the sample was placed. Interestingly, even the absorbance of the COC symmetric and asymmetric stretching bands in the TM mode was smaller than in the TE mode, but the difference in absorbance between the TM and TE modes was smaller than that observed with the PLA stretched film (DR = 5). This indicates that electrospinning PLA nanofibers have a preferential chain and dipole orientation, although the chain and dipole orientation degrees are small compared to uniaxially stretched PLA films.

1-2-2. Dynamic pressure signal

Piezoelectric signals of sensors fabricated using PLA films with various elongation ratios (DR) ranging from 1 to 5.5 were measured using a conventional dynamic pressure analyzer. 12A to 12G are measurement results of piezoelectric voltage signals generated by applying periodic external pressure along the thickness direction for various DRs. 12 h shows the V _pp of PLA films of various DR derived from a to g of FIG. The piezoelectric effect of the PLA elongation film as shown in FIG. 12 does not need to provide the shearing stress according to the stretching direction of the sample but the external pressure in the thickness direction When applied, it is generated by the deformation of the helical structure. As the DR increases (DR = 5 or more), the PLA spiral chains arranged in the uniaxial stretching direction are increased, and it is clear that the generation of the piezoelectric signal increases nonlinearly. The increased helical structure repeats the structure with the preferred chain and dipole arrangement due to the shear stress, which increases the piezoelectric signal generated by the dynamic pressure exerted in the outward direction. However, the stretching tensile stress is applied in a direction in which some larger than the fracture stress of the PLA (DR = 5.5), PLA molecular chain and dipole orientation degree is rapidly reduced DR = compared to the V _pp maximum value observed in 5 DR = in 5.5 The V _pp value is greatly reduced (h in FIG. 12).

1-2-3. PSB sensor signal

Based on the results of FIG. 12, a PLA film with DR = 5 was used to fabricate the PSB sensor. A silicone rubber coating sensor (as in Figure 1) sandwiched between elastic fabric bands was made using a PLA stretched film (DR = 5) cut at various angles (0 to 90 °, Figure 7) with respect to the stretching direction. In the periodic breathing process, an external pressure is applied to the PSB and the PSB sensor made with the PLA film cut at 45 ° produces the strongest signal about three times higher than the other samples cut at 0 ° and 60 ° (Fig. 13). Unlike in the previous dynamic pressure test (FIG. 12), periodic breath measurement using a PSB sensor applies not only the dynamic pressure effect but also the elongated effect, but the mainly effect is the cut angle of the film. The uniaxially stretched PLA film (DR = 5) has already been deformed into a spherical coil due to the stretching effect, and the C = O dipoles required for the generation of the piezoelectric signal are arranged in the proper direction only when cut at 45 degrees, So that a high pressure signal is expected. This is supported by the fact that the PLA chain exhibits shear-induced piezoelectric properties due to the stretching and pressing effect during the breathing process. This type of piezoelectric action differs from that seen in linear PVDF stretched films whose molecular chains are linear. In the case of PVDF stretched films, a major contributing factor is the uniaxial stretching followed by a polarization process in which C-F dipoles are preferentially arranged in the direction perpendicular to the stretching direction.

1-2-4. Electric radiation PLA Nano Web  Piezoelectric sensor based on

1-2-4-1. FE- SEM  Research

FE-SEM was chosen rather than the traditional SEM method due to the fact that it has a spatial resolution of 3 to 6 times better than conventional SEM of 1½ nm and is clear and less static image distortion. Figure 6 shows an FE-SEM image of a pure PLA nanofiber web obtained by electrospinning a 9 wt .-% PLA solution at different magnifications (2kx, 5kx and 100kx).

1-2-4-2. Dynamic pressure signal

Comparing the pure PVDF nanofiber web and V _{p -p} signal of the bio-signal measuring sensor made of PLA nanofiber web shown in FIG. 14. Under constant R _in, addition, the same experimental conditions as well as the external pressure, as compared with PVDF nanofiber web to generate ~ 3.7V PLA nanofiber web was produced an about 3.2V V _{p -p.} FIG. 15 shows a schematic diagram of an arrangement in a constructive and destructive configuration using PVDF and PLA nanofiber webs to distinguish between the effect of the CF dipole array of linear PVDF and the C = O dipole array direction of helical PLA. In the case of the PVDF nanofiber web, the CF dipole is mainly arranged on one side, thereby enhancing the piezoelectric signal in the constructive laminate, whereas the piezoelectric signal disappears in the destructive laminate (Fig. 15a). As described above, the piezoelectric signal of the PLA can be generated only by a variation of the helical structure in which the C = O dipole is preferentially arranged along the helical direction. Therefore, in the bio-signal measurement sensor fabricated with the PLA nanofiber web, it was expected that almost similar V _{p -p} signals would be generated in both constructive and destructive forms (FIG. 15 (b)). However, according to the results obtained in FIG. 16, the V _{p -p} signals (FIGS. 16A and 16C) in the constructive laminate structure of the PVDF and the PLA nanofiber web are different from the destructive laminate structure (b and d in FIG. 16) . Both of the constructive laminate structures of PVDF and PLA were enhanced compared to those shown in Fig. destructive type laminated PVDF sensors compared to the (b in Fig. 16) showed that the destructive stacked PLA nanofibers V _{p -p} signal of the bio-signal measuring sensor (d in FIG. 16) produced by an improved web. The above results demonstrate that the spiral PLA nanofiber web, as in an electrospun PVDF nanofiber web, is polarized during electrospinning without any additional elongation process, indicating that the C = O dipoles exhibit an alignment at a certain angle.

FIG. 17 shows changes in piezoelectric signals according to the number of laminated PLA nanofiber webs. As the number of PLA nanofiber web laminations increases, the final piezoelectric signal increases non-linearly. Although the signal generated by the lamination increase in the early stage was significantly increased (up to the fifth layer), it was found that the signal was increased only modestly even when the lamination was further increased, which caused the external pressure to be exerted on the PLA chain Indicates that the effect is limited. In other words, a specific thickness plays an important role in generating the final piezoelectric signal (Fig. 17). Additional experiments were performed using a five layer laminated PLA nanofiber web to study the effect of three different folding methods on the piezoelectric signal. Three different types of piezoelectric sensors were fabricated by folding the PLA nanofiber web and inserting the upper and lower electrodes in different ways to form various structures (FIG. 5). In the case of simple folding (Fig. 18a) and folding the electrodes in series (Fig. 18b) in a similar manner to the destructive lamination, the sum of C = O dipole polarization between all layers must be significantly reduced. However, when the electrodes were folded in series, much higher piezoelectric signals were seen than in the case of simple folding, probably because the conductivity between all the layers increased as the electrodes were inserted between the folded nanofiber webs. When the electrodes are connected in parallel (parallel connection of the battery) (Fig. 18 (c)), as the total area of the electrode generating the piezoelectric current increases and the total value of the generated current increases, appear. When the electrodes are measured to generate signals when folded so that the parallel connection, the use of an input resistance (R _in) of 1GΩ because the output voltage can be measured roneun NIDAQ board (the maximum input voltage 10V) be less than 10V input resistance R _in was reduced to 100 M? 10 times, and the output voltage was also reduced by 10 times. In the case of a parallel connection in which electrodes are sandwiched between folded nanofiber webs as compared to simple folding where the electrodes are located only at the top and bottom of the nanofibrous web laminate, The total number of C = O dipoles is further increased. The maximum generated current I _max can be calculated from the maximum peak pressure V _max using equation (1). Under the same experimental conditions, the parallel-connected PLA structure showed ~ 9 times more piezoelectric current signal than the series connected structure, and ~ 40 times more than the simple folding structure (Figure 19).

(One)

100: body pressing part 110: first band
120: 2nd band
200: folding type PLA nanofiber web
210: first folding unit 220: second folding unit
300: Flexible parallel electrode portion
310: first electrode 320: second electrode
400: shielded signal transmission line
500: elastic layer

Claims (5)

A body pressing part composed of two elastic bands expanding or contracting with the movement of the body while pressing the body part in which movement occurs during breathing or exercise and forming an insertion space between the two elastic bands;
A first folding part folded to face the top part and a top part of the nanofiber web produced by electrospinning polylactic acid (PLA), a bottom part and a bottom part, A second folding section folded to face each other with mutual opposing faces, a folded PLA nanofiber web folded to be alternately stacked;
The PLA nanofibrous web according to the present invention comprises a folded PLA nanofibrous web and a folded PLA nanofibrous web. The folded PLA nanofibrous web has a bottom and a top, A flexible parallel electrode unit receiving a piezoelectric signal generated in a folding type PLA nanofiber web that is stretched together; And
And a shield signal transmission line connected to the flexible parallel electrode unit and transmitting a piezoelectric signal as an electrical signal generated from the folding type PLA nanofibrous web to a control unit. Biological signal measurement sensor using material. The method according to claim 1,
Wherein at least 80% of the monomers constituting the polylactic acid (PLA) are composed of one kind of isomer selected from the group consisting of an L-isomer and a D-isomer. A bio - signal measurement sensor using PLA piezoelectric material in web form. 3. The method of claim 2,
Wherein the folded PLA nanofiber web is formed by folding the nanofiber web formed by electrospinning so that the same faces face each other at least twice. The biosignal measurement sensor using the PLA piezoelectric material of nanofiber web type obtained by electrospinning . The method of claim 3,
The flexible parallel electrode unit includes:
A first electrode connected to a bottom portion of the folded PLA nanofibrous web, the bottom portion of the folded PLA nanofibrous web being located in a space between the at least one second folded portions; And a second electrode connected to a top portion of the folding PLA nanofibrous web and disposed in a space between the stacked first folding portions, The PLA piezoelectric material according to claim 1, wherein the PLA piezoelectric material is formed of a nanofibrous web obtained by electrospinning. 5. The method of claim 4,
The PLA nanofibrous web according to any one of the preceding claims, further comprising an elastic layer covering the entirety of the folding type PLA nanofiber web provided with the flexible parallel electrode section, wherein the elastic layer is made of silicone rubber. Signal measurement sensor.

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