WO2017095097A1

WO2017095097A1 - High-sensitivity sensor containing linearly induced cracks and method for manufacturing same

Info

Publication number: WO2017095097A1
Application number: PCT/KR2016/013789
Authority: WO
Inventors: 최용환; 이태민; 이건희; 최만수; 강대식; 페트로피키트사
Original assignee: 재단법인 멀티스케일 에너지시스템 연구단; 서울대학교산학협력단
Priority date: 2015-11-30
Filing date: 2016-11-28
Publication date: 2017-06-08

Abstract

Provided is a high-sensitivity sensor having a conductive thin film containing linearly induced cracks. The high-sensitivity sensor relates to a sensor, obtained by forming linearly induced microcracks on a conductive thin film formed on a support, for measuring external tensile and pressure by measuring a change in the electrical resistance due to modification, short - circuiting, or openings in micro - joining structures formed by the microcracks. The high-sensitivity conductive crack sensor may be applied to high-precision measurements or artificial skins, and may be utilized as a positioning detection sensor by pixelating the sensor. Thus, the high-sensitivity sensor may be effectively used in the fields of precise measurements , bio-measurement devices through human skin , human motion measuring sensors, display panel sensors, etc.

Description

Straight line-induced crack sensitive sensor and its manufacturing method

The present invention relates to a linear sensor-induced crack-containing high sensitivity sensor and a method for manufacturing the same, and applied to a measurement or artificial skin requiring high precision for sensing tensile force and pressure by using a conductive thin film formed with linear cracks. This relates to a possible high sensitivity sensor.

In general, a high sensitivity sensor is a device that detects a minute signal and delivers it as data such as an electrical signal, which is one of the components required in the modern industry.

Among such sensors, capacitive sensors, piezoelectric sensors, strain gauges and the like are known as sensors for measuring pressure and tensile force.

Strain gauge sensor, which is a conventional tensile sensor, detects mechanical change as an electrical signal. When it is attached to the surface of a machine or structure, the strain gauge sensor is used to measure the change in fine dimension, that is, the strain. It is possible to know the stress which is important for confirming the strength and the safety from the size of the strain.

In addition, the strain gauge measures the deformation of the surface of the workpiece in accordance with the change in the resistance value of the metal resistance element, and in general, the resistance value of the metal material increases with increasing force from the outside and decreases with compression. Strain gages are applied to sensors as sensors for converting physical quantities such as force, pressure, acceleration, displacement, and torque into electrical signals, and are widely used for measurement control as well as experiments and research.

However, conventional strain gauge sensors are susceptible to corrosion due to the use of metal wires, are not only very sensitive, but also have low output values, requiring additional circuitry to compensate for small signals, and semiconductor tension sensors are heat sensitive. Has

The pressure sensor is a sensor that can measure the pressure applied to the surface, which is an essential element when manufacturing artificial skin. Strain represents the horizontal change in length applied to the surface, while pressure represents the force applied perpendicular to the surface.

Conventional pressure sensors measure the resistance value of a silicon film made of thin film that changes with pressure, and is widely used not only for research and measurement but also in industry.

However, the conventional pressure sensor has a disadvantage of being unable to distinguish small pressures due to its very low sensitivity and cannot be bent. This disadvantage makes it impossible to apply to artificial skin, it is necessary to manufacture a sensor that can bend while detecting a small pressure.

Due to the above problems, the sensor can be driven only in a specific environment, or affected by various environmental factors, such that the accuracy of the measured value is degraded. There is a problem that is difficult to secure. In addition, these sensors have a problem that it is difficult to manufacture a flexible structure due to its structural problems.

As interest in research into the development of wearable medical and artificial electronic skin devices and high performance sensors has increased, various types of pressure sensors based on nanowires, silicon rubber, piezoelectric and organic thin film transistors that accumulate external information have been developed. Has been developed.

Cracks have generally been regarded as defects and have been avoided, but studies related to cracks such as cracks, thin film cracking and interconnectors for nanowire production have recently been reported.

In addition, strain sensors based on carbon nanotubes, nanofibers, graphene platelets and mechanical cracks have been reported.

The crack sensor was affected by the spider's sensory system. Spider sensor is known to be very sensitive to strain and vibration.

Although cracks were generally regarded as defects to be avoided, as a study of cracking patterning, thin film crack formation has recently been reported for the fabrication of nanowires and interconnectors, and crack sensors similar to spider's sensory systems have been reported. It has been reported to be very sensitive to strain and vibration, but has a limit of only 2% strain.

Therefore, the development of a new high-sensitivity sensor that can compensate for this problem is required.

The technical problem to be solved in the present invention is to maintain the accuracy of the measured value even after repeated use while being less affected by the environment, and has a high sensitivity sensor that can sense the change in tension and pressure applicable to a variety of fields with flexibility To provide.

Another technical problem to be solved by the present invention is to provide a method for manufacturing the high sensitivity sensor.

In order to solve the above technical problem, the present invention,

A flexible support having a hole pattern formed thereon; And

A conductive thin film formed on at least one surface of the support;

The conductive thin film includes cracks induced in a straight line having a crack surface facing each other and at least some of the surfaces in contact with each other,

The crack surface is guided in a straight shape by a regular hole pattern formed in the flexible support,

Provided is a high sensitivity sensor for measuring an external stimulus by measuring an electrical change caused by a change in contact area or a short circuit or re-contact as the crack plane moves in response to an external physical stimulus.

The present invention also provides

Forming a regular hole pattern in the flexible support;

Forming a conductive thin film on at least one surface of the flexible support; And

It provides a method of manufacturing a high-sensitivity sensor comprising a; stretching the conductive thin film to induce a linear crack.

The high-sensitivity sensor of the present invention is capable of measuring tension and / or pressure with high sensitivity using a conductive thin film in which linearly induced cracks are formed on one surface of the support, and has flexibility to be applicable to various fields. . The high-sensitivity sensor as described above can be applied to highly accurate measurement or artificial skin, and can be utilized as a positioning detection sensor by pixelating the sensor, and thus can be used as a precision measurement field, a biometric device using human skin, and the like. It can be usefully used in the field of motion measuring sensor, display panel sensor and the like.

In addition, the high-sensitivity sensor can be mass-produced in a simple process, thereby having a very high economy.

FIG. 1 is a model of a crack lip having grains of size 1. FIG.

2 shows a complex planar portion surrounded by an integration contour.

3 is a schematic diagram of a manufacturing process of a crack sensor according to an exemplary embodiment.

4 is an SEM image (c, d) showing changes in the surface of the sensor (a, b) before and after pulling the crack sensor and changes in the crack on the conductive thin film according to one embodiment.

FIG. 5 is an SEM image showing that cracks are formed (b, c) before (a) and after the cracks are applied.

FIG. 6 is an SEM image showing the formation of cracks in various gap lengths. FIG.

FIG. 7 is a graph (b, d) showing a difference (a) of crack formation patterns and a FEM simulation result (c) for identifying the gaps at various gap lengths, and illustrating resistance changes according to crack formation differences.

FIG. 8 is a graph of the surface of a crack-based sensor randomly formed without patterning and a resistance change measured using the same. FIG.

9 is a conceptual diagram and a result graph showing a change pattern of resistance in the tensile direction.

10 is a load cell for measuring changes due to pressure and tension.

Figure 11 is a graph showing the reproducibility of the change in the resistance and repeated experiments by loading and unloading according to the range of change rate.

12 shows the results of resistance change measurement and hysteresis thereof by loading and unloading according to the change rate range.

FIG. 13 shows a normalized resistance vs strain curve comparing the theoretical value obtained by equation 6 with the experimental value measured by the crack sensor.

14 is a graph measuring the reaction rate for a sudden change.

Fig. 15 shows experimental results showing resistance changes caused by various pressurization conditions of a pressure range (a) of 0 to 10 kPa, a pressure caused by a small ant (b) and a pressure caused by a wrist pulse (c, d).

FIG. 16 illustrates a high sensitivity sensor capable of simultaneously indicating position and pressure using a multi-pixel array and measured results using the same.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Recently, a mechanical crack based sensor using a crackless parallel system with high sensitivity to deformation and vibration has been reported. However, in order to achieve ultrafast performance, force sensitivity must be amplified by high flexibility and controllability through the formation of cracks.

The present invention provides an inexpensive ultra high sensitivity strain and pressure sensor based on the induction formation of more precise mechanical cracks in a regular micro scale pattern.

The sensor according to the present invention can concentrate stress in a specific area around the hole by patterning a hole on the surface of the device, from which it is possible to precisely form a uniform crack connecting the hole.

The sensor of the present invention is a sensor capable of measuring the tensile rate and measuring the pressure applied to the surface. After depositing a thin metal film on the polymer to produce a mechanical crack. It can be effectively applied to wearable healthcare and can replace existing stretch or pressure sensors.

Hereinafter, a high sensitivity sensor having a conductive film containing a crack induced in a straight line according to an embodiment of the present invention will be described in more detail.

High sensitivity sensor according to the present invention

A flexible support having a hole pattern formed thereon; And

A conductive thin film formed on at least one surface of the support;

In addition, the present invention,

Forming a regular hole pattern in the flexible support;

The high-sensitivity sensor according to the present invention may form cracks uniformly formed in a straight line along the hole pattern by the hole pattern formed on the flexible support, and the formation of such a straight crack may further improve the sensitivity of the sensor. Can be.

In the crack sensor according to the present invention, when a conductive thin film formed on a hole pattern formed on the flexible support is subjected to an external physical stimulus due to tension or pressure, a stress sensor is formed around a position where a hole formed on the flexible support is located. ), The crack surface can be uniformly formed along the contact surface between the hole and the hole.

The crack surface is formed between the hole and the hole as shown in the adjacent c and d of Figure 4, the length (G) of the crack surface as shown in Figure 7a is the center of the hole adjacent to the center of the hole It may have a length of 50% or more with respect to the length (P) of the straight line followed by, preferably, having a length of 60% or more.

When the length of the G has a length of less than 50% of the length of the P, the crack may not be formed in a straight line, which is formed in the form of a plurality of cracks are not straight, as shown in Figure 6a and 7a Sensitivity may be reduced.

According to one embodiment, the hole (hole) pattern may be any shape, such as circular, oval, square, rhombus, asterisk, cross, etc., preferably a rhombus made of a curve as shown in c, d of FIG. That is, a rhombus consisting of four arcs with four vertices in the shape of a cross or a curve may be suitable.

The hole pattern described above may be advantageous for uniformly forming cracks of a straighter shape by providing directionality in the generation of cracks at each vertex.

Crack sensor according to the present invention is generated by the stress concentrated in two adjacent hole pans by the external force by the hole pattern as shown in Figure 4c, d, as shown in Figure 4d and 6b by the external force Cracks may be formed in a straight line along the hole pattern.

When a tensile force is applied to a patterned crack, the cracks formed perpendicular to the axis of force exerted by the tensile force are opened, and the cracks formed in parallel (horizontally) are closed.

By extending the cracks as shown in FIG. 4D by applying strain to the tightly closed cracks as shown in FIG. 4C, the contact area between the crack surfaces can be reduced, which increases the electrical resistance. Since there is no conductivity between the broken crack faces, the resistance of the metal layer may increase rapidly due to the cracks opened by the break.

In rare cases, bridge, metal contact between crack lip may lead to high strain sensitivity of the resistance.

The high sensitivity sensor of the present invention may exhibit a sensitivity (ΔR / R ₀ ) of 1 to 1 × 10 ⁶ at a strain of 0 to 10%.

The gauge factor of the high sensitivity sensor according to the present invention is defined as (Δ R / R ₀ ) / ε, and the gauge factor may be 2 × 10 ^{6 or} more in a strain range of 0 to 10%.

The high sensitivity sensor according to the present invention may exhibit a sensitivity (ΔR / R ₀ ) of 2 × 10 ⁴ or more at a pressure in the range of 7 to 10 kPa, and preferably 1 × 10 ⁵ or more at a pressure in the range of 8 to 9.5 kPa. .

The present invention exhibits high sensitivity by pressure sensitivity, which can be used to measure physiological signals such as pulses by attaching to the wrist as shown in FIGS. 15C and 15D. Figure 15c is a result of measuring the pulse by attaching a high-sensitivity sensor according to the present invention to the wrist, Figure 15d is a high-sensitivity sensor according to the present invention can distinguish the three minute differences, such as pulse percussion wave, tidal wave, diastolic wave It means that it has high precision as much as possible.

According to one embodiment, the external physical stimulus may be applied at various angles with respect to the crack surface, the axis of force with respect to the direction in which the external physical stimulus exerts a force on the crack surface is perpendicular (90 °) or 45 degrees. When applied at an angle of ° can exhibit a better sensitivity. That is, when the external physical stimulus exerts an external force symmetrically and uniformly with respect to the shape of the pattern of the conductive thin film formed by the shape of the hole (hole) or cracks, it may appear more sensitive, that is, the gauge factor ( The change in gauge factor may be greater, and more preferably an external force may be applied to the crack surface in an angle range of 90 ° ± 10 °.

The high-sensitivity sensor is a sensor in which cracks formed in the conductive thin film are spaced according to tension or pressure, thereby measuring the change in resistance of the conductive thin film to measure external tension or pressure.

That is, among the cracks formed in the conductive thin film, cracks having crack surfaces facing each other and at least some of the surfaces are in contact with each other, and when the external stimulus such as tension or pressure change is applied, the contact surface moves while the contacted crack surfaces move. According to this change, an electrical resistance is changed or an electrical short or open is formed, and thus a large change in the resistance value on the conductive thin film is generated, thereby detecting the conductive thin film structure by using a tension sensor, a pressure sensor, or the like. It can be used as.

In the case of the conventional strain gauge sensor, the resistance increases as the metal thin film is stretched, but in the case of the present invention, the crack gap of the metal thin film is opened. As crack cracks open, electrical shorts increase, and resistance increases rapidly. For this reason, it has a much higher sensitivity than the conventional strain gauge sensor.

According to one embodiment, the cracks present in the conductive thin film may be induced in a straight line according to the hole pattern formed in the flexible support, the extent of the crack is also generated lifespan spacing, shape, thickness of the conductive thin film, forming conditions And the like, and are not particularly limited.

In the high sensitivity sensor of the present invention, the flexible support is selected from the group consisting of polyurethane acrylate (PUA), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE) and the like. It is preferably any one selected or a combination thereof, most preferably polyurethane acrylate (PUA).

In the high-sensitivity sensor of the present invention, the conductive thin film is preferably any one selected from the group consisting of Au, Ag, Pt, Cu, Cr, Pt, etc., or a combination thereof, most preferably Cr / Pt combination. Can be.

According to one embodiment, the thickness of the conductive thin film is not limited, but preferably has a thickness such that cracks can be formed by mechanical methods such as tensile and bending, and the formation conditions of such a crack is a conductive thin film. And the type of flexible support.

In the high sensitivity sensor of the present invention, the thickness of the conductive thin film is preferably 0.1 nm to 1 μm, more preferably 10 nm to 50 nm, even more preferably 20 nm to 30 nm. In addition, the Young's modulus of the conductive thin film may be 10 ¹⁰ to 10 ¹² .

In the high sensitivity sensor of the present invention, the gauge factor of the high sensitivity sensor may be 1 x 10 ⁵ to 1 x 10 ⁶ (1 to 10% tensile range). The gauge factor refers to the rate of change of the strain gauge's resistance to generated strain.

In the high sensitivity sensor of the present invention, the flexibility of the high sensitivity sensor means that it can be bent to a minimum radius of 1 mm or more.

By the above characteristics, the high-sensitivity sensor of the present invention can be applied in various fields such as pressure sensor, tension sensor, artificial skin, etc., and can be utilized as positioning detection sensor by pixelating the sensor.

The present invention carried out a theoretical analysis of the resistance vs strain data, which was in agreement with the results of the experimental data at strains not too large.

The inventors have revealed a universal mechanism for strain sensors based on parallel cracks formed on a uniform 20 nm Pt film of particulate form cracked on a stretchable polymer. In the sensor, free cracks cut the sensor strip by a technique that produces a large unidirectional strain. The normalized conductance S vs. strain ε of the sensor, defined by Equation (1) below, is the probability distribution function (pdf) P (x) of the steps on the cracks that form the contact between the cracks lip: Is determined by

(One)

For free cracks, equation P (x) has only parameters related to size.

Strain ε ₀ corresponds to the width of crack gap kε ₀ , where kε ₀ is the grain size x ₀ = kε ₀ to be.

(2)

In the above formula, x = ε / ε ₀ and k is a proportional coefficient defined in relation to the crack gap width with respect to strain. k may differ depending on the materials constituting the parallel crack system, which can be obtained from the experiment.

Physically, Equation 2 indicates that the small step of the crack protrusion formed by the shift of the grain is the same distribution as the large step formed by the accumulation of the grain, which is the elasticity of the substrate having no scale and any length characteristics. Because of the presence of the area, it may not be possible to distinguish between large and small meandering projections.

One of the solutions in equation 2 is log-normal pdf

(3)

Alternatively, you can choose the nearly identical log-logistic pdf.

(4)

Μ and B are variables of pdf.

The distribution of equation 3 and the distribution of equation 4 both belong to the class of asymmetric distributions with so-called long tails.

The large non-zero probability, except for the rare contact between the crack lip, is in the nature of the conduction mechanism through the crack, and therefore coincides with the long tail distribution.

Equations 3 and 1 provide the resistance R = 1 / S as a function of strain, as follows:

(5)

erf (x) is an error function. Equation 5 renders the normalized resistance. The normalized resistance is remarkably consistent with the experimental results with strains up to 2%.

At the same time, the log-logistic pdf of Equation 4 can be derived with Equation 1 below.

(6)

The equation is consistent with the experiments of the fitting parameters ε ₀ = 0.39 and B = 2.39 and has the same precision as the lognormal pdf of equation 5.

However, the power-law function of Equation 6 is much simpler than the error function of Equation 5.

The present invention can propose a generalized exponential law for data fitting by experimenters doing free parallel crack studies.

Surprisingly, after changing a uniform Pt film strip into a patterned strip on a much more extensible polymer (FIG. 4A), the strain dependence of resistance from exponential law to exponential function in equation 6 over a wide strain range of 5% or more. It has changed tremendously. A straight line appearance in the semi-log plot is shown in FIG. 11D.

Here is the basic mechanism of this phenomenon.

Important differences between the cracks formed in previous studies and the present invention are shown in FIGS. 5B and 5C.

The cracks between the pattern patches closely follow the "crests" of the wrinkles on the metal / polymer film.

That is, this means that the crack passage is very direct and only closely neighboring platinum particles have separated along the crack lip (FIG. 1).

In this regard, the local deviation is related to the size of the grains and, therefore, may not satisfy the modification equation 1 for free crack generation.

Meanwhile, as shown in FIG. 5B, the pattern patches are pressed to each other in a direction horizontal and perpendicular to the deformation direction, due to a Poisson ratio of 0.5, which is an inherent property of the rubbery material.

Thus, the system is virtually unchanged in one dimension with cutting through cracks currently located in a cluster of squares that are lined up in the horizontal direction (FIG. 5).

Similar to this study, it is sufficient to calculate the step pdf.

According to FIG. 1, each i-th particle along the crack (crack orbit) lip can move up and down with a probability of 1/2 and yi movement (in the deformation direction).

The crack step size refers to the travel distance of the up (down) trajectory by several adjacent particles.

As shown in FIG. 1, for example, the sum of three grain movements in one direction produces a step of size X. Suppose the local grain shift is distributed in the local pdf P (y).

The grains adjacent to normalized size 1 moving perpendicular to the small steps y1, ..., y2 may have an overall pdf P (x) function of step size x.

(7)

In the above formula,

(8)

delta is a delta function and n = 1, 2, ... The delta function represents a fine pdf of the step consisting of the movement of the positive value n in the direction satisfying the equation y1 + ... + yn-x = 0.

According to the above equation, as assumed, the probability of vertical movement of the particles is 1/2.

Therefore, defining a step as total upward movement, the probability of the configuration given to the small steps of ⁿ is proportional to 1/2 ⁿ .

Then rewrite Equation 7 as the Fourier integral of the delta function,

(9a)

Or to simplify Equation 9a as

(9)

Where

10

to be.

The geometric series of equation 9 can be converted directly to equation 11 below.

(11)

The Cauchy integration of Equation 11 can be analyzed in general terms.

At large values x, the decay of the function P (x) may be nearly exponential and may indicate that it may be nearly independent of the particular form of P (y).

(12)

If one pole plays the dominant role in the denominator of equation 11,

(13)

In equation 13, the lowest actual value z ₀ > 0.

All other poles (all solutions in equation 13) can be complex and can lie at the bottom of the complex plane (see example in FIG. 2).

It can be seen from Equation 10 that there is always a single pure imaginary pole, α = -iz ₀ , otherwise it is impossible for the integral of Equation 10 to equal 2 when we have the pole in the upper half. .

In fact, if α = -iz ₀ , and

If the integral of f (α) in Equation 10 with a value greater than 1 is not possible, it is because the integral contains a normalized probability function, and | exp (iαy) | Even if it is exactly 1, the maximum value is given only as 1.

However, Equation 13 is not satisfied because f (?) = 2> 1.

Conveniently, by closing the Cauchy integral integral shape of Equation 11 by an infinitely large semicircle at the bottom face (FIG. 2), P (x) is obtained as the sum of the remainder of the poles, which is governed by the pole -iz ₀ . The largest value of the exponent term will prevail at the large x. In the case of limiting itself by this play, a normalized probability can be obtained.

(14)

This is because from the equation 1 the conductance S has a large strain as well

(15)

It is clear that it is also an exponential function of strain due to resistance.

(16)

The exponential law function and the exponential function can be regarded as the difference between Equations 6 and 16.

Consider the most common example of P (y) = 1, assuming the position of any grains next to each other, and then move the uniform distribution of grains along the cracks in FIG. In this case, Equation 10 enhances the following Equation 17,

(17)

Equation 13 then takes the form:

. (18)

Equation 17 can be found numerically. The lowest z ₀ = 1.256, and the other poles are 2.789 ± 7.438 i and 3.360 ± 13.866 i ... (see Figure 2).

In FIG. 13 we provide the pure exponential function of equation 16 (black line) with the strain (red line) calculated as normalized resistance vs P (y) = 1 to see the agreement between the experimental data and the theory. do. On the other hand, the asymptotic function 16 must rescale the strain by α = 7 times, for example, to match the resistance vs strain calculated with a uniform pdf of grains, and the linear slope of the experiment in FIG. 11D.

Physically it limits the movement of grains by 30% and thus means that the cracks are flattened.

Therefore, the resistance reacts as flattening by increasing the slope of the resistance on the semi-logarithmic scale.

The parameter measures the flatness of the crack.

It can be seen from FIG. 1 that the maximum inclination of the step protrusion is limited by α, and α is the tangent of the maximum inclination angle.

The maximum tilt angle at P (y) = 1 is 45 degrees with tangent α = 1.

Of course, if the crack ribs are perfectly flat with no movement and α = 0, it can have sudden separation of the crack ribs and infinite slope of R / R ₀ .

According to the fitting of FIG. 2E, the parameter of strain measured in% is

to be.

With this close estimate, it was possible to calculate a particular grain size x ₀ .

The SEM image shows that the distance x of the gap is proportional to the strain x = kε, where k with ε in%

50 nm and the particle size x ₀ = kε ₀ = 30 nm can be quite close to the primary particle size component of the granulated Pt film.

Hereinafter, examples are provided to help the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and various changes and modifications can be made within the scope and spirit of the present invention. It will be apparent to one having the above and obviously such modifications and modifications fall within the scope of the appended claims.

Example 1 Fabrication of Inductive Crack-based High Sensitivity Sensor

A crack sensor was prepared as shown in FIGS. 3A-3C.

Specifically, spin coated 100 탆 polydimethylsiloxane (PDMS; polydimethylsiloxane) was treated with oxygen plasma using a plasma surface treatment machine CUTE-1MPR (Femto Science Inc.) and bonded onto glass. 20 μl polyurethane acrylate (PUA; polyurethane acrylate) was dropped into the PDMS / glass mold, and then covered with a filler patterned silicone mold, followed by irradiation with 350 nm UV (about 12 mJ / cm ² ). The patterned 10 nm chromium layer was formed by thermal evaporation with a thermal evaporator (Selcos Inc.) and deposited a sputtered 20 nm platinum layer. The metal layer deposited PUA film was carefully peeled off the PDMA / glass mold and then tensioned 5% in the x / y direction using a custom stretcher. The crack sensor before and after tensioning is shown in FIG. 4.

After that, wires were attached using conductive polymers to connect electrical signals to the sensors. The high sensitivity sensor thus manufactured is illustrated in FIGS. 4 and 5. 4 and 5 show that the crack is opened as the deformation is applied to the high sensitivity sensor.

Example 2 Multi-Pixel Array Sample Preparation

In order to demonstrate the scalability and ability of the device for detecting mechanical vibrations and pressures, a 16 x 4 pixel array is provided in a 6 x 6 cm ² area as shown in FIG. 16b. A schematic diagram of a multiple pixel system is shown in FIGS. 16A and 16C. Each pixel (1 × 1 cm ² islands) was constructed with a thickness of 100 μm PUA / 10 nm Cr / 20 nm Pt with a hole pattern, and then stretched and stretched 10% bi-axially to generate cracks. The electrical connection between cracked Pt and Lab View-based PXI-4071 system (NI instrument Inc.) was formed by gold lines (Au, 50 nm thick) deposited on PET films using the shadow mark method. Each pixel manufactured was freely placed on a PET film by a conductive polymer (CW2400, circuitworks) or electrically connected by a gold line.

Experimental Example 1 Measurement of Change in Resistance (Gauge Factor) According to Crack Gap Length

In order to confirm the effect of the straight crack using the high sensitivity sensor of Example 1, cracks were formed using three different hole patterns.

As shown in FIG. 7A, P is the shortest distance to the hole center, is the same in all three patterns tested, G is the length of the gap, and the gap represents the shortest distance between the tip of the hole.

The crack formation patterns and changes in resistance when the lengths of G were 10 μm, 15 μm, and 20 μm are shown in FIGS. 6 a, b, and a through d in FIG. 7.

6A shows that when the length of the gap G is 10 μm and 15 μm, several cracks can be induced, and 6b shows that a very straight crack can be generated when G is 20 μm. The occurrence of a large number of uneven cracks, such as that shown in FIG. 6A, can lower the sensitivity to changes in resistance, and these results are shown in FIGS. 7B and 7D.

To understand this non-uniformity, we performed a finite element method (FEM) simulation and the simulation results are shown in Figure 7c. Based on the results of FIG. 7C, it is shown that the narrow pattern gap produces a wider distribution of high stresses that stimulates wherever cracks appear within the gap distance. In addition, if the length G of the gap does not have a sufficient length with respect to P, the section in which the stress acts on the crack surface where the crack is generated may be too wide and diverse, and stresses may be generated at various points to induce the crack. It becomes possible.

The crack of the crack sensor according to the invention is advantageous in the case where it is induced in a straight line, which is shown in the results of FIGS. 7b and 7d.

In addition, the resistance change at 20 μm of FIG. 7B shows a sharper graph compared to the sensor based on the disordered crack, which shows the change in resistance according to the change of the distance of the crack lip. Respond more accurately to changes in the distance of cracks.

Experimental Example 2 Measurement of Change in Resistance (Gauge Factor) According to Tensile Angle

To demonstrate the possibility of a theoretical concept of resistance that depends on the single parameter (normalized gap size x / x ₀ = kε / x ₀ ) of the high sensitivity sensor manufactured in Example 1, we set the normalized resistance vs strain The square pattern was positioned at 60-45 ° as shown in FIG. 9B to compare with the case of °. The experimental results are shown in FIGS. 9C and 9D.

By replotting on a log-log scale, the 60 degree curve coincided with the 90 degree curve after adjusting the strain to 0.32 (see FIG. 9C).

Geometrically 90-60 = 30, which is from x = kε to sin (π / 6) x = k (0.5ε) or above k (0.32 ε) because of the additional shrinkage caused by the deformation in the orthogonal direction of the sample. Since the gap size by deformation is provided, it is explained by effectively narrowing the appropriate gap size (Fig. 9A).

Since the conductivity is dominated by most of the conductivity paths that occur through narrow gaps at 30 °, the difference in the angle of view of 60 ° may be somewhat relevant here.

For 45 ° at the same angle of view, the rescaling factor is 0.7, thus close to sin (π / 4) = 1 / √2 (FIG. 9C).

Figure 9d is a result of the resistance change that occurs as the angle of the crack generated in the lattice shape, the largest change in resistance when the angle is 90 °, the change in resistance is shown in the order of 45 °, 60 ° .

Thus, the change in resistance is more sensitive when the rectangular patch formed by the cracks generated in the form of a lattice is tensioned through the force symmetrically at the same angle, which means that the distance of the cracks can be more effectively opened (90 ° -tension). The angle generated by the difference of the angle) is an angle of 45 ° or less at an angle of 45 ° or more, which may result in a lower resistance compared to 45 ° as a narrower distance between cracks is formed. However, this may have less effect at angles close to 90 °.

Experimental Example 3 Measurement of Resistance Change According to Strain Variation

The change in resistance was measured by applying current while applying tension to the high sensitivity sensor of Example 1. In detail, FIGS. 11A to 11D illustrate changes in electrical resistance measured by stretching up to a maximum of 10% and returning to an original state, that is, 0% strain, and FIGS. 11A to 11C illustrate hysteresis and reproducibility of the sensor of Example 1. It is a graph.

The high sensitivity crack sensor of Example 1 was fixed by a custom pressure test equipment.

Continuous pressure was applied to the crack sensor constructed based on the load cell (2712-041, Instron Co.) and Lab VIEW (NI instrument) based on the PXI-4071 resistance analyzer (NI instrument) of FIG. 10.

FIG. 11A shows the results of reproducibility tests measured at 5000 repetition cycles in the strain ranges of 0 to 2.5%, 0 to 5%, and 0 to 10%, and FIG. 11B shows reproducibility after 5000 cycles at 10% strain. It represents. From this, it can be seen that the crack sensor according to the present invention shows little difference in performance even after 5000 or more repeated measurements.

FIG. 11C shows a reproducibility result of repeating the loading-unloading test using the loading cell of FIG. 10 1800 times in the strain range of 0 to 10%, and the crack sensor according to the present invention has excellent reproducibility from the results of the graph. It can be seen that.

In addition, as shown in FIG. 11D, when the electrical resistance measured while the sensor of Example 1 was stretched to a maximum of 10% and then returned to its original state, that is, 0% strain state, the change in electrical resistance was approximately equal to the initial resistance. It can be seen that it changes up to 2x10 ⁵ times, and the same type of resistance change can be repeatedly obtained repeatedly. This is due to the fact that the contact area decreases as the strain is applied to the crack surfaces that were in contact with each other, and eventually the electrical resistance rapidly increases as they are spaced apart, and the cracks spaced apart as the sensor contracts as the strain is removed. As the surface comes into contact, the resistance decreases as the contact area increases, returning to its original state.

Experimental Example 4 Measurement of Resistance Change According to Strain Variation

12A to 12C show graphs measuring resistance changes measured in loading and unloading tests in the strain ranges of 0 to 2.5%, 0 to 5%, and 0 to 10%.

12A to 12C, the crack-based sensor of Example 1 according to the present invention shows little hysteresis in the loading and unloading process, but the hysteresis increases slightly as the applied strain range increases.

12C is shown with standard deviation using the mean value of the values measured in five samples.

In the present invention, the theoretical analysis of the strain data for the resistance was performed (Equations 1 to 18), and FIG. 13 shows a strain-resistance curve in which the resistance change according to the strain is fitted based on data obtained experimentally and theoretically. Plot of From the above results, it can be seen that the crack sensor according to the present invention exhibits almost the same result as the experimental data in the range of strain not too large.

Figure 14 is a graph showing the reaction time when a sudden change, it can be seen that the reaction within 100ms through the results of the experiment. In addition, it can be seen from FIG. 14 that the change of the strain and the change of resistance show almost the same response.

Experimental Example 5 Measurement of Resistance Change According to Pressure

The application of pressure can stretch the sample and increase the resistance of the metal film.

For the measurement of pressure, the crack-based sensor of Example 1 is mounted on a custom machine, and the resistance data can be measured with a resistance analyzer (PXI-4071, National Instruments).

Pressure data was obtained with the load cell 2712-041, Instron Co. of FIG.

The resistance of the pressure data obtained can be linearized into three pressure zones, which is shown in Figure 15a. The graph of FIG. 15A is

1) Slope at 0-6 kPa 606.15 kPa ^-1

2) Slope at 6-8 kPa 40341.53 kPa ^-1

3) slope at 8-9.5 kPa shows three pressure regimes of 136018.16 kPa ^-1 , and the slope of this pressure-resistance curve is reported (Y.Zang. Et al. Flexible suspended gate organic thin-film transistors for ultra -sensitive pressure detection.NAURE COMMUNICATIONS, 6: 6269, doi: 10.1038 / ncomms7269) shows a significantly better sensitivity than 192 kPa ^-1 at pressures in the range of 0-5 kPa, the highest performance of pressure sensitivity.

FIG. 15B shows a result of measuring a small ant mass (Ponera japonica, 1 mg) corresponding to a pressure of 0.2 Pa using the crack sensor, which shows that the crack sensor according to the present invention exhibits high sensitivity to pressure. .

The crack sensor was mounted on the wrist to measure the physiological signal of the wrist pulse.

15C and 15D show graphs of measuring physiological signals of the wrist pulse, and FIG. 15D shows enlarged results of a part of the 15C graph, and the crack sensor according to the present invention is shown in FIG. It can be seen that the sensitivity is high enough to measure all the step changes.

Experimental Example 6 Position and Pressure Measurement Using a High Sensitivity Sensor Array

To demonstrate sensor scalability and spatial resolution and pressure sensing capability, a multi-pixel array was fabricated by the method of Example 2, which is shown in FIG. 16A. Crack-based devices exhibit high flexibility and may be warped as shown in FIG. 16B.

S, N, and U in the shape of small LEGO pieces were carefully placed in the sensor of Example 2 in which the pixels were arrayed as shown in FIG. 16C, and the pressure and position derived therefrom could be easily detected from the array sensor. The results measured from the array sensor are shown in FIG. 16d.

The specific parts of the present invention have been described in detail above, and for those skilled in the art, these specific descriptions are merely preferred embodiments, and the scope of the present invention is not limited thereto. Will be obvious. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims

A flexible support having a hole pattern formed thereon; And

A conductive thin film formed on at least one surface of the support;

The conductive thin film includes cracks induced in a straight line having a crack surface facing each other and at least some of the surfaces in contact with each other,

The crack surface is guided in a straight shape by a regular hole pattern formed in the flexible support,

A high sensitivity sensor for measuring an external stimulus by measuring the electrical change caused by a change in contact area or a short circuit or re-contact as the crack surface moves in response to an external physical stimulus.
The method of claim 1,

The crack surface is a high-sensitivity sensor is a stress caused by the external force is concentrated between the adjacent holes, the crack is induced in a straight line along the hole pattern.
The method of claim 1,

The crack surface is provided between adjacent holes and holes, and the length G of the crack surface is 60% or more with respect to the straight line P connecting the center of the hole and the adjacent hole where the crack surface is located. High sensitivity sensor having.
The method of claim 1,

And a sensitivity of the external force applied to the crack surface is applied in a direction of 90 ° or 45 ° with respect to the crack surface.
The method of claim 1,

High sensitivity sensor with a sensitivity of 2x10 4 or greater at pressures in the range of 7 to 10 kPa.
The method of claim 1,

The shape of the hole pattern is a high sensitivity sensor that is formed of a rhombus shape consisting of a cross shape or a curve having four vertices coupled to four arcs (arc).
The method of claim 1,

The flexible support is any one selected from the group consisting of polyurethane acrylate (PUA), polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polypropylene (PP) and polyethylene (PE), or a combination thereof. High sensitivity sensor.
The method of claim 1,

The conductive thin film is any one or a combination thereof selected from the group consisting of Au, Ag, Pt, Cu, Cr, Pt and the like.
The method of claim 1,

The crack is a high sensitivity sensor that is nano-level fine cracks.
The method of claim 1,

The high sensitivity sensor, characterized in that the electrical short-circuit or opening of the crack is caused by an external stimulus to change the electrical resistance value of the conductive thin film.
The method of claim 1,

And wherein the external stimulus is one of a stretch and a press or a combination thereof.
The method of claim 1,

High sensitivity sensor that the thickness of the conductive thin film is 0.1 nm to 1 ㎛.
The method of claim 1,

High sensitivity sensor having a gauge factor of 1 to 2 × 10 6 at a strain of 0 to 10%.
The method of claim 1,

The high sensitivity sensor is a flexible sensor that can be bent to a minimum radius of 1 mm or more.
A pressure sensor comprising the high sensitivity sensor according to any one of claims 1 to 14.
A tension sensor comprising the high sensitivity sensor according to any one of claims 1 to 14.
A pressure and tension sensor comprising a high sensitivity sensor according to any one of claims 1 to 14.
An artificial skin comprising the high sensitivity sensor according to any one of claims 1 to 14.
Forming a regular hole pattern in the flexible support;

Forming a conductive thin film on at least one surface of the flexible support; And

The method of manufacturing the high-sensitivity sensor of claim 1, further comprising: inducing linear cracks by stretching the conductive thin film.