JPH0326972B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a skin resistance measurement sensor for locally measuring a skin resistance value corresponding to the physiological activity of living skin. [Prior Art] One conventional method for measuring skin resistance is to apply a constant voltage between positive and negative electrodes placed on the skin at regular intervals and measure the value of the current flowing therethrough. It is widely known as a simple method. [Problems to be solved by the invention] The skin of living bodies such as the human body is composed of the epidermis, dermis, and subcutaneous tissue, and is responsible for some of the body's temperature regulation and metabolic functions (sweating and skin respiration). It plays an important role in preventing bacteria and other bacteria from entering the body. The subcutaneous tissue controls the internal and external metabolic cycles of the body through blood flow, sweat lines, etc., and supports the activation of the skin tissue itself. On the other hand, the dermis receives replenishment of cell constituent substances from the subcutaneous tissue and regenerates various skin cells at regular intervals. Skin cells that have lost their physiologically active functions are pushed upward and become the epidermis, which protects the dermis from the outside world. Therefore, the tissue located in the lower layer of living skin has a higher degree of physiological activity and a higher water content. In other words, the lower the skin layer, the higher the electrical conductivity. By the way, like other cells, the metabolic function of the living body's skin stagnates as the living body ages, so the water content of the skin decreases, that is, the electrical conductivity of the skin decreases. Furthermore, when the physiological activity of living skin is disrupted due to skin diseases, autoimmune diseases, etc., the affected area generally loses moisture compared to normal conditions and becomes rough, resulting in a decrease in electrical conductivity. Conversely, skin tissue may become inflamed due to trauma, infection, allergic disease, etc., and lymph fluid may leak out, causing local skin resistance to drop sharply compared to surrounding normal tissue. In this way, the age of the skin and the health condition of the skin are reflected in the electrical conductivity through the water content, so if skin resistance can be easily measured, it will be useful in determining the health condition.
For example, as mentioned above, as the skin ages, the moisture content decreases, causing cracks and hangnails on the surface.
Not only does this increase the number of spots and wrinkles, which is a cosmetic problem, but it also makes it easier for bacteria and harmful substances to penetrate into the body from the outside, which is undesirable from the standpoint of maintaining the health of the body. In order to compensate for the fact that the supply of fat and water from the subcutaneous tissue slows down due to aging, and the "freshness" of the skin decreases, it is effective to apply the necessary ingredients to the skin surface in a cream or aqueous solution. be. These moisture, ions, and oils supplied from the outside penetrate into the inside through the epidermis and form a film on the epidermis to block the outside air, resulting in the "freshness" of the skin.
will recover. The recovery process of such damaged skin should naturally be observed as a change in skin resistance. Conventionally, as one means for measuring skin resistance, a method has been known in which a constant voltage is applied between the positive and negative electrodes placed on the skin at regular intervals and the value of the current flowing is measured. However, this method requires an external power supply that always shows a constant value, making the device large and inconvenient, and there is a risk that a short circuit between the electrodes or other accidents may cause a large current to flow through the skin and cause burns. It was hot too. An object of the present invention is to eliminate the drawbacks of the conventional galvanic skin resistance measuring device described above and to provide a simple galvanic skin resistance measuring device based on a new principle. [Means for Solving the Problems] In order to achieve the above object, the present invention applies the principle of a chemical battery and combines an anode electrode with a higher standard monopolar potential and a cathode electrode with a lower standard monopolar potential. Using a device with a structure in which a DC potentiometer or ammeter is connected between the anode and the skin, the cathode and the anode are brought into pressure contact with the skin of the living body so that the skin contact area is constant and the distance between the cathode and the anode is kept constant. Disclosed is a sensor for measuring skin resistance that displays the voltage on the DC potentiometer. In particular, a sensor using a noble metal as an anode material and a semiconductor crystal as a cathode material is useful because it can generate a stable and large electromotive force. [Function] According to the present invention, a kind of chemical cell is formed by the anode electrode, the skin, and the cathode electrode, and a voltage corresponding to the physiological state of the skin is generated, which is detected and displayed by a potentiometer. [Example] The principle and examples of the present invention will be explained below. FIG. 1 shows an embodiment of the present invention. A conductive mineral (A) 2 with a higher standard unipolar potential and a conductive mineral (B) 3 with a lower standard unipolar potential are placed with an insulating resin 4 at a certain interval.
Fix it with. A2 and Otsu3 are connected to separate lead wires, and each lead wire is externally connected to a terminal of a DC potentiometer 5. At this time, the lead wire of A 2 is connected to the positive terminal of the DC potentiometer 5, and the lead wire of Otsu 3 is connected to the negative terminal. Each of the conductive minerals A and B has the same surface area, for example, a spherical shape with a diameter of 3 mm, and a hemisphere is embedded in the insulating resin 4. At the same time, the surface of the insulating resin 4 is the skin surface 1.
FIG. 1a shows the state in which it is pressed against the skin surface 1 so as to be in contact with the skin surface 1. At this time, the pointer of the DC potentiometer shows a constant positive potential corresponding to the skin resistance value. This is due to the following reasons. Taking an example in which A 2 is a metal and Otsu 3 is an n-type semiconductor single crystal, when this sensor for measuring skin resistance is placed in contact with the skin, the energy band diagram becomes as shown in FIG. 1b. In the figure, Ec is the electron energy at the bottom of the conduction band, Ev is the electron energy at the top of the filling band, e ^- is a free electron, and h ⁺ is a free hole. Since the standard unipolar potential is high in A2, when an electrical closed circuit is formed by pressure contact, free electrons flow from Otsu3 to A2. Free electrons flow from the upper 2 to the skin 1 at the pressure contact part, and a potential gradient as shown is formed. As mentioned above, the biological skin 1 is an electrical conductor, and the electrons flowing from the anode (A 2) move inside the skin 1 toward the cathode (B 3) according to the lines of electric force that follow the distribution of internal resistance. flows. That is, the skin 1 acts not just as a resistor but as an electrolyte, and the parts A2-Skin1-B3 form a so-called biological battery. As is well known, a chemical battery generates electromotive force through a redox reaction within an electrolyte, with a reduction reaction occurring on the anode side and an oxidation reaction occurring on the cathode side. In this case, in the skin near A2, for example, Fe ³⁺ +e ^- →Fe ²⁺ (oxidizing agent Fe ³⁺ ), and in Otsu 3, S→S ⁺ +e ^- (reducing agent Otsu) is generated. Here, S is a semiconductor, and for example, if S≡Ge, then Ge→Ge ²⁺ +2e ^- . As shown, a Schottky barrier is formed at the contact surface between the cathode semiconductor 3 and the skin 1, and the Schottky barrier is biased in the opposite direction by the chemical reaction described above. For this reason, electrons cannot flow into the cathode from within the skin. Since electrons become insufficient in the semiconductor crystal due to the outflow of electrons to the anode, free electrons are excited into the conduction band of the semiconductor via defect levels of the crystal. Free holes generated by free electron excitation flow to the interface with the skin 1 due to the internal electric field of the semiconductor, and at the interface, they are converted into positive ions of the semiconductor by the catalytic action of the skin, liberated from the crystal, and diffused into the skin 1. Penetrate. That is, the battery current in the electrolyte (skin 1) is composed of electrons injected from the anode metal (A 2) side and cations flowing from the cathode semiconductor (Otsu 3) side. In principle, the electromotive force of this chemical battery is controlled by the combination of anode material A and cathode material B, but the electromotive force that can be taken out to the outside actually depends on the redox ability (strength of reaction) of the electrolyte (skin). Determined by battery internal resistance. For example, platinum as A2, n as Otsu3
When using type germanium crystals and using an electrolyte solution such as dilute sulfuric acid, the maximum voltage that can be taken out to the outside is approximately 1.15V, but the same material combination was used to construct the skin resistance measurement sensor shown in Figure 1a. In this case, the voltage that can be taken out to the outside is at most 0.7V even if the skin contact distance between A and B is shortened to 1 mm or less. However, if we limit the combination of A and B, make the skin contact areas constant for each (it is possible for the skin contact areas of A and B to take different constant values), and furthermore keep the distance between A and B constant, Figure 1. The voltage value displayed on the external DC potentiometer 5 through the lead wire as shown in a is the voltage value displayed on the electrode 2-
The value reflects the skin resistance (constituting a part of the battery's internal resistance) between 3 and 3. Therefore, depending on the purpose,
By changing the combination of A and B materials, skin contact area, and skin contact distance between A and B, it is possible to select an appropriate voltage value to be displayed externally. As mentioned above, the water content and ionic conductivity of human skin vary depending on age and individual differences, and even within an individual, they vary slightly depending on the skin area, physical condition, season, and weather. In an attempt to measure skin age using the sensor for measuring skin resistance of the present invention, we selected five healthy male and female subjects from each age group, and
Table 1 shows the average value of the voltage generated corresponding to the skin resistance on the back of the right hand measured with the device shown in Figure 1a at 10 am on a sunny day in August (winter season) and August (summer season). in this case,
A 2 is a platinum ball with a diameter of 3 mm, Otsu 3 is an n- ball with a diameter of 3 mm.
A Ge (resistivity: 0.01 Ωcm) sphere was used, and the skin contact distance between the two was 2 mm.

[Table] The displayed measured values show that there are significant differences between groups, meaning that the older the age, the higher the skin resistance in winter than in summer. Furthermore, it has been suggested that skin resistance is higher in men than in women, and that the younger the age, the greater the difference in skin resistance between summer and winter. These can be considered to be phenomena related to skin metabolism. Note that the higher the skin resistance, the higher the internal resistance of the battery, so the displayed voltage values in Table 1 become smaller. Therefore, by using the device of the present invention, the skin age of the subject can be estimated within a certain error range based on data prepared in advance. Even the skin of the same subject shows different skin resistance values at different locations. This is natural considering that skin resistance reflects the local water content and ionic conductivity of cellular tissue. For example, select a teenage male from the subject group listed in Table 18.
Table 2 shows the differences in display voltage depending on the location measured at 2:00 pm on a sunny day in May (summer). The measuring device used was the same as in Table 1, and the measured values are expressed as average voltages. Although the differences are not as large as in the age groups shown in Table 1, there are clearly significant differences depending on the measurement site.

[Table] It has been pointed out that the skin resistance is particularly high on the elbows where the skin is thick and the epidermis tends to become rough. Being able to easily and relatively measure such local skin resistance using a voltage display is considered to be of great benefit in maintaining skin health. Unlike conventional electrical resistance measuring devices, the device of the present invention does not require an external power source, making it extremely easy to use, and not only does it not require preliminary operations such as adjusting the power supply voltage, but it also eliminates the need for short-circuiting of both electrodes. However, there is no risk of excessive current flowing, making it suitable for human body measurement (if the electrodes are short-circuited, no voltage will be generated). Also, the current value itself is very small (about 0.1mA at most). This is because the electrolyte action of the skin is small, so it is much safer than using an external power source.However, to obtain accurate readings, wipe off moisture, oil, and dirt from the skin surface beforehand, and clean the electrodes. Care must be taken to wipe off dirt and keep contact resistance low. FIG. 2 shows a spring type pressurized skin resistance measuring device which is another embodiment of the present invention. The electrode part that comes into contact with the biological skin 1 has a semicircular gold plate 2 as an anode and a semicircular semiconductor tin (α-Sn) as a cathode.
Plate 3 was used. The radius of each was approximately 5 mm.
An insulating groove 11 with a width of 1 mm was provided in the center between these two electrodes 2 and 3. An insulating liquid groove 11 was provided between the electrodes 2, 3 and the groove 4. The electrodes 2 and 3 and the groove 4 were fixed with an insulating resin 4. Lead wires 9 and 10 connected to each electrode extended upwardly inside the hollow cylindrical part 8 through the inside of the fixed part made of the resin 4, and were connected to terminals of a DC potentiometer 5 attached to the lid of the hollow cylindrical part 8, respectively. The cylindrical insulating resin 4 to which the disc electrode and the lead wire are fixed is adhered to an outer frame 7 of the device, and the outer frame 7 is in contact with a hollow cylindrical portion 8 via a spring 6. As a result, when measuring skin resistance, a constant area of the negative and positive electrodes is brought into contact with the skin by constant pressurization by the spring 6, and a constant contact resistance can be provided. Using this device, we measured biological skin resistance and tested whether it was possible to measure the improvement in skin ``moisture'' caused by cosmetics. After measuring the skin resistance of the right cheek and back of the right hand of 10 female customers in their teens and 20s indoors on a sunny day in August, a beauty cream containing water-soluble ions was rubbed into the areas to be measured, and the skin resistance was measured. The change in potential was measured as a change in potential, and the average value for each group is shown in Table 3.
As shown in the measurement results in Table 1, the skin of young women is generally "moisturized" and therefore the displayed voltage of the DC potentiometer 5 is high. This shows that it has the effect of improving freshness.

〔Effect of the invention〕

In the present invention, measurement results corresponding to the local resistance value of the skin surface of a living body have been shown, but it is obvious that the device of the present invention can also be applied to measurement of water content of hair and distribution of subcutaneous fat.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams for explaining another embodiment and principle of the present invention, respectively. In the figure, 1 is a living body skin, 2 is an anode electrode A, 3 is a cathode electrode A, 4 is an insulating resin, 5 is a DC potentiometer, 6 is a spring, 7 is an outer frame, and 8 is a hollow cylindrical portion.

Claims (1)

[Claims] 1. Consists of negative and positive electrodes that are used at a constant distance from each other, and a DC potentiometer that is connected to the electrodes and has a function of detecting the voltage generated between the two electrodes, and the positive electrode is The negative electrode consists of a first conductive mineral shell having a standard unipolar potential of A sensor for measuring skin resistance, which is made of two conductive minerals and uses both the negative and positive electrodes mentioned above in contact with the skin at the same time. 2. A sensor for measuring skin resistance as described in claim 1, wherein A is a precious metal and B is a semiconductor crystal.