Method and device for measuring viscoelasticity of surface of biological tissue

Abstract

The present invention relates to a method and device for measuring the viscoelasticity of a surface of biological tissue. The method comprises the following steps: S1, in the normal direction of a surface of biological tissue, driving the surface to move in the normal direction by a constant displacement and then maintaining same; S2, by using a sensor, measuring a time-dependent mechanical response of the surface of the biological tissue during the implementation process of step S1; and S3, according to the mechanical response obtained by the sensor, using a processing module to output the viscoelasticity characteristic data of the surface of the biological tissue. Said measurement method of the present invention aims to more scientifically and reliably measure the viscoelasticity of surfaces of biological tissue, especially human skin.

Description

A method and device for measuring viscoelasticity of biological tissue surface Technical Field

[0001] The invention relates to a method and a device for measuring the surface viscoelasticity of biological tissue, especially human skin. Background Art

[0002] Analyzing the physical properties of biological tissues, such as human skin or the epidermis of plant fruits, is crucial. For example, measuring the surface elasticity of human skin is valuable for both cosmetic and dermatological applications.

[0003] For measuring skin elasticity, the CK device commonly available on the market uses a combination of negative pressure and optical measurement, as outlined in patent US5054502A. During each test, the front end of the probe module's outer wall is pressed against the skin, causing deformation / displacement through vacuum suction or piston pressure. Measurements are then taken based on the reduction in light intensity transmitted from the light transmitter to the light receiver. Actual products, such as the elasticity measurement products shown on the official website www.courage-khazaka.de, utilize a vacuum-negative pressure approach. The measurement principle, as described on the CK website and in its technical manual, is that the CK device applies a fixed suction force to the skin for 0.1 seconds, observing changes and recovery before and after that 0.1 second. Characteristic indicators such as R-parameters, F-parameters, and Q-parameters are derived from this pressure to evaluate the viscoelastic properties of the skin. The CK method can be understood as observing the skin's stretching distance and subsequent recovery over a 0.1-second period using a fixed suction force. However, the empirical value of this 0.1-second time period is subject to considerable industry debate. For example, US scientists conducting relevant research believe that 0.04-0.07 seconds is appropriate. Others suggest that this value should be individualized and will vary depending on the test sample. Currently, recognized limitations of the CK device include the difficulty in data reproducibility and interpretation, as well as the insufficient resolution caused by negative pressure suction.

[0004] On the other hand, skin itself has a certain elastic modulus. According to the study "Stiffness and Elasticity of the Masticatory and Facial Expression Muscles in Patients with the Masticatory Muscle Pain" (Korean J Oral Med, Vol. 34, No. 3, 2009), the elasticity of human skin is approximately 0.70 ± 0.46 N. During measurement, the front face of the CK device presses against the skin, generating pressure. Because skin has an elastic modulus and the skin is interconnected, the compression of the front face on the skin it covers (herein, the compression force is called external pressure, which refers to the pressure between the front face and the skin) will cause the elasticity of the skin within the hole of the front face to change. The degree of change is related to the degree of compression. If the external pressure used in each measurement is different, the pressure environment will change with each measurement, and the baseline for each measurement will be different, which will cause interference with the measurement.

[0005] Summary of the Invention

[0006] The present invention aims to propose a new measurement method for detecting the surface viscoelasticity of biological tissues, especially human skin, in a more scientific and reliable manner.

[0007] To this end, a method for measuring the viscoelasticity of the surface of biological tissue is proposed, comprising the following steps: S1, in the normal direction of the surface of the biological tissue, driving the surface to move to a fixed displacement along the normal direction and then maintaining it; S2, using a sensor to measure the time-varying mechanical response of the surface of the biological tissue during the implementation of step S1; S3, using a processing module to output viscoelastic characteristic data of the surface of the biological tissue based on the mechanical response obtained by the sensor.

[0008] The measurement method of the present invention does not adopt the idea of ​​CK to measure deformation with a fixed force. Instead, it drives the surface of biological tissue, such as human skin, to move a fixed distance to measure the surface's mechanical response over time (fixed-distance force measurement). Based on the mechanical response curve, relevant features (such as the various features mentioned above) are obtained to provide experts with an evaluation of the viscoelasticity of the biological tissue surface. Each person's skin composition is different, and the mechanical response feedback under a fixed displacement of the skin will be different. The present invention reflects these differences in the mechanical response through the fixed-displacement force measurement method, avoiding the introduction of empirical judgment, making the measurement results for different testers more consistent and accurate. Theoretically, the measurement method is also more scientific.

[0009] The measuring method of the present invention is particularly suitable for measuring the viscoelasticity of human skin, and is also applicable to measuring the surface viscoelasticity of other biological tissues such as plant fruits.

[0010] When measuring the viscoelasticity of human skin, as an improved solution, step S1 is configured to use an actuator to drive the sensor to apply an action to the surface of the biological tissue until the surface moves to a fixed displacement and then maintains the position. The action includes at least mechanical compression or mechanical stretching. For example, the CK device relies on negative pressure to stretch the skin, which requires a sealed environment and inevitably presses the front end against the skin, disrupting its natural state. The present invention, by using the sensor to perform mechanical action, allows for detection of the skin in an undamaged or substantially undamaged natural state.

[0011] Skin, as a combined model of an elastic element obeying Hooke's law and a viscous element obeying Newton's law of viscosity, has certain requirements for the duration of mechanical motion. Taking compression as an example, we want to minimize the diffusion of the skin caused by viscosity during compression, allowing for as much release as possible after compression for more accurate results. Therefore, pressing too slowly is unfeasible, while pressing too quickly also presents problems. For example, accurate braking of the machine can lead to significant deviations in skin displacement. To balance detection accuracy, diffusion of the skin during compression, and displacement control, extensive experiments have shown that the time from the sensor applying the motion to the surface moving normal to a fixed displacement in step S1 must be controlled within 0.1-1 seconds.

[0012] As another improvement to the measurement of skin viscoelasticity, the measurement method of the present invention also includes step S4, which is used to cyclically repeat steps S1-S3, and in each cycle, the fixed displacement of the surface moving along the normal direction is controlled to be different to obtain the mechanical response of different layers of the skin. For example, in the first execution of steps S1-S3, the displacement of the skin is controlled to be between 0-2mm, which is used to measure the mechanical response of the skin epidermis to the pressing or stretching action; in the second cycle of steps S1-S3, the displacement of the skin is controlled to be between 2-4.4mm, which is used to measure the comprehensive mechanical response of the epidermis and dermis, and so on to the measurement of subcutaneous tissue (optional). By controlling the different action distances each time, the characteristics of different layers of the skin can be reflected. Furthermore, in order to avoid interference of the last press on the next measurement, a recovery time is set after the end of each cycle and before the start of the next cycle for the skin to return to its natural state.

[0013] As another improved solution, step S2 further includes: forming a mechanical curve based on the mechanical response obtained by the sensor; the starting point of the mechanical curve is configured to be at least at or before the maximum value corresponding point, the maximum value being the value when the force fed back by the surface reaches its maximum; the ending point of the mechanical curve is configured to be at least at or after the steady-state value corresponding point, the steady-state value being the value when the force gradually decreases to a stable value after the maximum value, and the curve segment between the maximum value and the steady-state value can fully reflect the viscoelastic characteristics of the surface of the biological tissue. The method for determining the steady-state value further includes: using the value corresponding to the first point on the mechanical curve after the maximum value whose slope is less than a set threshold as the steady-state value; or using the value of a point on the mechanical curve corresponding to a set time period after the maximum value as the steady-state value. Preferably, a prompt device can be provided to provide a prompt when the sensor obtains the ending point, such as through sound / light / vibration.

[0014] The present invention also provides a device for measuring the viscoelasticity of the surface of biological tissue, comprising: a sensor for measuring the mechanical response of the surface when an action is applied to the surface of the biological tissue; an actuator for driving the sensor to perform the action; a processing module for coupling the actuator and the sensor respectively; and a memory arranged to store computer-executable instructions, which, when executed, causes the processing module to execute the above-mentioned method.

[0015] To prevent interference with the measurement caused by the front end extrusion disrupting the surface structure's natural state during surface elasticity measurement, an improved solution is described. The measuring device includes a distance detection device and a reference surface facing the surface during measurement. The sensor is configured to contact the surface protruding from the reference surface during measurement, thereby achieving non-contact between the reference surface and the surface. The distance detection device is used to obtain the distance between the reference surface and the biological tissue surface. During measurement, the distance between the reference surface and the measured surface structure is obtained by the distance detection device, so that an external system, such as a robotic arm, moves the module to the reference surface at the same distance from the surface structure as before, ensuring a stable measurement reference / measurement environment. The sensor then contacts the surface structure protruding from the reference surface during measurement. Since the reference surface and the surface structure are non-contact, the surface structure is not squeezed, thereby eliminating pressure interference at its source. This allows the sensor to apply compression or tension to the surface in its natural state (undamaged by compression) and measure the mechanical response, resulting in more accurate measurement results. In this solution, the reference surface should be understood as the outer surface of the module housing that contains the sensor.

[0016] Furthermore, the distance detection device is configured to include at least two distance sensing electrodes provided on the reference surface, wherein the distance sensing electrodes are provided on the front or back of the reference surface; the contactless measurement module is provided with a capacitance-to-digital conversion circuit (CDC) coupled to a processing module, wherein the capacitance-to-digital conversion circuit couples each distance sensing electrode to obtain mutual capacitance; the processing module outputs distance information based on the mutual capacitance. Specifically, the mutual capacitance value formed by the distance sensing electrodes changes when approaching a surface structure such as human skin, thereby obtaining the distance between the human skin and the reference surface, controlling the distance between the human skin and the reference surface to reach a preset value and ensuring that it remains stable. In the above scheme, only an approximate distance range can be obtained based on a pair of electrodes. In order to obtain more accurate distance information, the number of distance detection devices can be configured to be at least two and arranged around the sensor. The area and / or spacing of the distance sensing electrodes in each distance detection device are different, so that the strength of the electric field lines formed is different, that is, the electric field lines formed are high and low. On the one hand, the measurement range is expanded to provide a reference for the operating speed of the external actuator, and more importantly, the height difference formed by the electric field lines can be used to obtain an accurate degree of proximity.

[0017] Alternatively, as another improvement, the reference surface can be controlled to be in contact with the skin each time the surface structure is measured. Specifically, the measuring device is configured to have a pressure detection device and a reference surface that directly or indirectly presses against the surface during the measurement; the pressure detection device is used to sense the contact pressure between the reference surface and the surface when the reference surface directly or indirectly presses against the surface. During the detection process, the pressure detection device is used to feedback the contact pressure (external pressure) between the reference surface and the surface structure, such as human skin, and the module is moved by an external system, such as a manipulator, to adjust the contact pressure to be consistent with the previous measurement, for example, a contact force of 0.5N or the like. On the one hand, there is basically no squeezing and thus basically no damage to the natural state of the skin. On the other hand, the sensor is maintained in a uniform external pressure measurement environment in each measurement to avoid introducing measurement errors, so that the sensor can apply a pressing or stretching action under a stable measurement reference and then measure the mechanical response of the surface structure, and the measurement result is more accurate. Similarly, the number of pressure detection devices is configured to be at least two and arranged around the sensor to take into account each circumferential position and ensure detection uniformity. Preferably, the number of pressure detection devices is set to at least three and evenly distributed around the sensor.

[0018] For a solution in which a sensor is used to press a surface structure, the sensor can be configured to include a pressure detection sensor coupled to an actuator, wherein the actuator is used to drive the pressure detection sensor to move along a normal direction of contact with the surface structure during measurement. Furthermore, the pressure detection sensor is configured as a first sensor unit, the first sensor unit being provided with a flexible multifunctional layer, the flexible multifunctional layer being internally provided with a curved elastic electrode electrically connected to the multifunctional layer as an upper electrode, a lower electrode being provided below the upper electrode, an insulating layer being provided between the upper and lower electrodes, and a downward projection of the upper electrode covering at least a portion of the area of ​​the lower electrode, the flexible multifunctional layer being deformed by an external force, driving the upper electrode to change its contact area with the insulating layer; the contactless measurement module being provided with a capacitance-to-digital conversion circuit (CDC) of a coupling processing module, the capacitance-to-digital conversion circuit coupling each electrode via a switch array for the capacitance formed between the upper and lower electrodes in the first sensor unit. When pressed, the deformation of the flexible multifunctional layer and the capacitance formed between the upper and lower electrodes reflect the normal component of the force. Combined with the CDC to collect the capacitance value of each electrode, a high force resolution can be achieved. In addition, due to the direct measurement using tactile means, the elastic force can be accurately measured.

[0019] For stretching using a sensor, the sensor can be configured to include a tension sensor, wherein the surface of the tension sensor that contacts the surface structure is provided with an adhesive layer, such as double-sided tape. The tension sensor is coupled to an actuator, which is configured to drive the tension sensor to move in a normal direction of contact with the surface structure during measurement. During testing, when the tension sensor contacts a surface structure, such as human skin, the double-sided tape adheres to the skin, providing a pre-adhesive force. The actuator drives the tension sensor to move, and the tension sensor is in a stretched state, generating a tensile force. The tensile force and the pre-adhesive force can be used to determine the actual contact stress between the skin and the sensor. In the present invention, after testing is completed, a protective cover can be installed to prevent the double-sided tape from being exposed to air for a long time, causing oxidation reactions and changes in its viscosity. Alternatively, the double-sided tape can be made into a consumable material. When testing is required, the double-sided tape is placed in a groove in the watch case. After monitoring is completed, the double-sided tape is removed and the adhesive position is wiped to ensure that the pre-adhesive force remains relatively stable during each test. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 shows a schematic flow chart of a method for measuring viscoelasticity of biological tissue surfaces;

[0021] FIG2 is a schematic diagram showing the relative position relationship between the biological tissue surface viscoelasticity measuring device and the tissue surface;

[0022] FIG3 shows a schematic structural diagram of a device for measuring viscoelasticity of a biological tissue surface;

[0023] FIG4 is a schematic diagram showing the effect of the measurement device when the sensor is pressed to the depth of the epidermis;

[0024] FIG5 is a schematic diagram showing the effect of the measurement device when the sensor is pressed to the depth of the dermis;

[0025] FIG6 shows a schematic diagram of the structural distribution of a distance detection device;

[0026] FIG7-1 shows a schematic diagram of the electric field line distribution structure when the distance detection electrode is located on the skin side of the reference surface;

[0027] FIG7-2 shows a schematic diagram of the electric field line distribution structure when the distance detection electrode is located on the side of the reference surface facing away from the skin;

[0028] FIG8 shows a schematic structural diagram of a pressing scheme of a testing device for viscoelasticity of biological tissue surfaces;

[0029] FIG9 shows a schematic diagram showing the distribution relationship between the flexible upper layer electrodes and the lower layer electrodes;

[0030] Figure 10-1 shows a schematic diagram of the grouping and distribution relationship between the flexible multifunctional layer and the lower layer electrodes;

[0031] Figure 10-2 shows a schematic diagram of the relationship between the grouping of the flexible multifunctional layer and the distribution of the lower layer electrodes;

[0032] FIG11 is a schematic structural diagram of a stretching scheme of a testing device for viscoelasticity of a biological tissue surface;

[0033] FIG12 shows a schematic diagram of the protective cover installation structure after the detection is completed. DETAILED DESCRIPTION

[0034] As shown in Figure 1, a flow chart of a method for measuring the viscoelasticity of the surface of biological tissue mainly includes three steps: S1, in the normal direction of the surface of the biological tissue, driving the measuring device to move along the normal direction of the surface of the biological tissue to a fixed displacement and then maintaining it; S2, synchronously with S1, using a sensor to measure the time-varying mechanical response of the surface of the biological tissue during the implementation of step S1; S3, based on the mechanical response obtained by the sensor, using a processing module to output the viscoelastic characteristic data of the surface of the biological tissue.

[0035] As shown in FIG. 2 , the surface tissue measured by the biological tissue surface viscoelasticity measuring device is configured as skin, which is mainly composed of a stratum corneum 601 , an epidermis 602 , a dermis 603 , and a subcutaneous tissue 604 .

[0036] As shown in Figure 3, the biological tissue surface viscoelasticity measuring device is mainly composed of a sensor 100, an actuator 200, a distance detection device 300, and a processing module 400. In step S1, the actuator 200 drives the sensor 100 to stretch or press the surface structure to reach a predetermined position. The feedback information of the sensor 100 is analyzed by the processing module 400 to obtain the contact stress between the sensor 100 and the skin surface, and the mechanical response data required for step S2 is completed. In step S1, the time required for the sensor 100 to move from the beginning to the normal preset position can be configured as a fixed time. The measuring device can be controlled by an external robotic arm to ensure that the measurement position is relatively fixed each time, and the feedback information of the distance detection device 300 during the test can ensure that the relative position relationship between the reference plane and the epidermal structure is stable.

[0037] As shown in Figures 4 and 5, each measurement process of the measuring device needs to include steps S1-S3, and also includes step S4. Step S4 is to cyclically execute steps S1-S3. During the repeated cycle, the displacement of the sensor 100 can be different according to the instructions of the processing module 400 under the drive of the actuator 200. Different preset displacements of the sensor 100 are formulated according to the depth distance of the skin surface. The viscoelastic characteristic value of the deep skin can be characterized by the mechanical response curve measured at that depth, eliminating the previous test data to characterize the viscoelastic characteristic data of the skin component at that depth, thereby achieving the viscoelastic effect of detecting components at different depths. After each measurement is completed, the cyclic measurement interval needs to be configured with sufficient time so that the surface of the biological tissue, such as the skin, can return to its natural state to avoid inconsistent initial states of repeated measurements. Driven by actuator 200, sensor 100 stretches or compresses epidermal tissue. The starting point of the mechanical response curve for the epidermal tissue stress condition is configured to be at least at or before the point corresponding to the maximum contact force, which is the value at which the force feedback from the surface tissue reaches its maximum. The ending point of the mechanical response curve is configured to be at least at or after the point corresponding to the steady-state value, which is the value at which the force gradually decreases to a stable value after the maximum value. The steady-state value is determined by determining the steady-state value by: determining the value corresponding to the first point on the mechanical curve after the maximum value where the slope of the mechanical change is less than a set threshold; or determining the steady-state value by determining the value of a point on the mechanical curve that is a set time after the maximum value. When the force response curve reaches its end point, i.e., when the epidermis returns to its initial state, the detection device can issue a prompt, which can be a voice prompt via a buzzer on the processing module, a visual prompt via an external display on the measurement device, or a light prompt via a device such as a light-emitting diode.

[0038] As shown in Figure 6, the distance detection device 300 mainly includes distance detection electrodes, which include at least two groups of electrode groups. The sensor 100 protrudes from the distance detection device. When the test device approaches epidermal tissue such as skin, the capacitance value formed by the distance detection electrode changes. The processing module 400 can know the distance between the test device and the skin, thereby ensuring that the position of the test device and the human skin is relatively stable each time it is measured. Since the sensor 100 protrudes from the distance detection device, the distance detection device 300 will not directly contact the skin, which can avoid damage to the skin and external force interference during the test process.

[0039] As shown in Figure 7-1 and Figure 7-2, the distance detection electrodes can be distributed on the side of the reference surface close to the human skin or the side facing away from the human skin. The distance detection electrodes can be configured with at least two electrode groups. The distance electrodes can also be configured into electrode groups with different areas and spacings to form different electric field line distributions, thereby improving the overall detection distance range while subdividing the detection distance and accurately judging the relative position relationship between the reference surface and the human skin.

[0040] As shown in Figure 8, the sensor 100 in the compressive configuration of the device for measuring the viscoelasticity of biological tissue surfaces primarily comprises a flexible upper electrode 101 (integrated with a flexible multifunctional layer at the bottom and an upper electrode located in the middle of the multifunctional layer, which protrudes upward to form a curved hemisphere), an insulating layer 102, and a lower electrode 103 disposed on the processing module 400. The lower electrode 103 is contained within the processing module 400 but can also be separately disposed. Driven by the actuator 200, the sensor 100 can move along the normal direction of the epidermal structure, achieving a compressive action on the epidermal structure. A distance detection device 300 defines the initial state between the detection module and the epidermal structure. The sensor 100 is pressed by the actuator 200. Due to the varying viscoelasticity of the epidermal structure, the deformation of the flexible multifunctional layer of the upper electrode 101 varies under the same displacement state. This difference in the viscoelasticity of the epidermal structure is determined by the change in the capacitance of the sensor 100 detected by the processing module 400. By real-time monitoring of capacitance changes caused by deformation of the upper electrode 101 of the sensor 100, a force response curve of the epidermal tissue during testing can be derived. Viscoelastic characteristic parameters of the epidermal tissue are then derived via processing module 400. Multiple sensors 100 can be used, and averaging multiple groups can be used to reduce measurement errors.

[0041] As shown in Figure 9, the flexible upper electrode 101 is in contact with the insulating layer 102 on the surface of the lower electrode 103 under the action of external force. Due to the pressure, the flexible upper electrode 101 is deformed, and the mutual capacitance formed by the flexible upper electrode 101 and the lower electrode 103 changes. The magnitude of the normal force acting on the sensor 100 can be obtained by the change in capacitance value.

[0042] As shown in FIG10-1 , the lower electrode 103 can also be configured as multiple distributed electrodes, which can be configured in a strip shape or configured as at least three detection electrodes in different directions according to deformation. When the flexible multifunctional layer of the upper electrode 101 is deformed by force, the projected area of ​​the partitioned area of ​​the lower electrode is changed differently, resulting in different capacitance change information. The upper electrode 101 couples different combinations of upper and lower electrodes through the switch array of the processing module 400, and the actual force magnitude and direction information of the upper electrode 101 can be obtained based on the different contact areas.

[0043] As shown in FIG10-2 , the upper electrode 101 can also be divided into multiple parts, and the parts are bonded together by an insulating layer. There is no conduction between the parts. The lower electrode 103 is a whole and serves as a common electrode. The magnitude and direction information of the force can also be obtained based on the capacitance change values ​​of different electrode components.

[0044] As shown in Figure 11, when the measuring device detects the surface viscoelasticity in a stretched state, the sensor 100 is mainly composed of a tension detection sensor 105 and an adhesive layer 104. The tension detection sensor 105 is fixed to the actuator 200. During measurement, the actuator 200 drives the tension detection sensor 105 to produce relative normal movement with the surface tissue. The tension detection sensor 105 contacts the surface tissue such as human skin, and the adhesive layer 104 is such as a double-sided tape. The three are fixed together, and the adhesive layer 104 provides a pre-bonding force. The actuator 200 drives the tension detection sensor 105 to move normally. The tension detection sensor 105 is in a stretched state and generates a stretching force. The stretching force and the pre-bonding force can be used to derive the actual contact stress between the human skin and the sensor 100. Through steps S1-S2, the mechanical response curve of the surface tissue under the action of the stretching force can be obtained, and the surface tissue viscoelastic characteristic parameters are output through the processing module 400.

[0045] As shown in Figure 12, after the inspection is completed, the protective cover 500 can be installed to prevent the double-sided tape from being in long-term contact with the air to cause an oxidation reaction and change in viscosity; alternatively, the adhesive layer 104 can be made into a consumable material. When inspection is required, the adhesive layer 104 is placed in the groove of the case. After the inspection is completed, the adhesive layer 104 is removed and the bonding position is wiped to ensure that the pre-bonding force of each test remains relatively stable.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for measuring the viscoelasticity of a biological tissue surface, characterized in that: The following steps are involved: S1. In the normal direction of the surface of the biological tissue, driving the surface to move along the normal direction to a fixed displacement and then maintaining the displacement; S2, using a sensor to measure the time-varying mechanical response of the surface of the biological tissue during the implementation of step S1; S3. Outputting viscoelastic characteristic data of the surface of the biological tissue using a processing module according to the mechanical response acquired by the sensor.

2. The measuring method according to claim 1, characterized in that: The biological tissue is configured as skin.

3. The measuring method according to claim 2, characterized in that: The step S1 further comprises: An actuator is used to drive the sensor to apply an action to the surface of the biological tissue until the surface moves to the fixed displacement and then maintains the displacement, wherein the action at least includes mechanical pressing or mechanical stretching.

4. The measuring method according to claim 3, characterized in that: In step S1, the time from when the sensor starts to apply the action to when the surface moves to a fixed displacement along the normal direction is configured to be within 0.1-1 s.

5. The measuring method according to claim 2, characterized in that: The method further comprises a step S4 for cyclically repeating the steps S1-S3, and controlling the fixed displacement of the surface moving along the normal direction to be different in each cycle so as to obtain the mechanical responses of different layers of the skin.

6. The measuring method according to claim 5, characterized in that: A recovery time is reserved after each cycle ends and before the next cycle begins for the skin to recover to a natural state.

7. The measuring method according to claim 1, characterized in that: The step S2 further comprises: Forming a mechanical curve based on the mechanical response obtained by the sensor; The starting point of the mechanical curve is configured to be at least located at or before a point corresponding to a maximum value, and the maximum value is a value when the force fed back by the surface reaches a maximum; The end point of the mechanical curve is configured to be at least located at or after a point corresponding to a steady-state value, wherein the steady-state value is a value when the force gradually decreases to a stable value after the maximum value.

8. The measuring method according to claim 7, characterized in that: The method for determining the steady-state value further includes: The value corresponding to the first point after the maximum value on the mechanical curve whose slope is less than the set threshold is taken as the steady-state value; or, The value of the point corresponding to the set time length after the maximum value on the mechanical curve is taken as the steady-state value.

9. A device for measuring viscoelasticity of biological tissue surface, characterized in that: include: a sensor for measuring a mechanical response of the surface of the biological tissue when an action is applied to the surface of the biological tissue; An actuator, used for driving the sensor to perform the action; a processing module, coupled to the actuator and the sensor respectively; A memory arranged to store computer executable instructions which, when executed, cause the processing module to perform a method according to any one of claims 1 to 8.

10. The measuring device according to claim 9, characterized in that: The measuring device has a distance detection device and a reference surface facing the surface during measurement; The sensor is configured to contact the surface protruding from the reference surface during measurement so as to achieve non-contact between the reference surface and the surface; The distance detection device is used to obtain the distance between the reference plane and the surface of the biological tissue.

11. The measuring device according to claim 10, characterized in that: The distance detection device is configured to include at least two distance sensing electrodes disposed on the reference surface; The contactless measurement module is provided with a capacitance-to-digital conversion circuit coupled with the processing module, and the capacitance-to-digital conversion circuit couples each distance sensing electrode to obtain mutual capacitance; The processing module outputs the distance between the reference plane and the biological tissue surface according to the mutual capacitance Distance information.

12. The measuring device according to claim 11, characterized in that: The number of the distance detection devices is configured to be at least two and they are arranged around the sensor, and the areas and / or intervals of the distance sensing electrodes in the respective distance detection devices are different.

13. The measuring device according to claim 9, characterized in that: The measuring device has a pressure detection device and a reference surface that directly or indirectly bears against the surface during measurement; A pressure detection device is used to sense the contact pressure between the reference surface and the surface when the reference surface directly or indirectly presses against the surface.

14. The measuring device according to claim 9, characterized in that: The sensor is configured to include a pressure detection sensor; The pressure detection sensor is coupled to the actuator, and the actuator is used to drive the first pressure detection sensor to move along the normal direction of contact with the surface during measurement.

15. The measuring device according to claim 14, characterized in that: The pressure detection sensor is configured as a first sensor unit, the first sensor unit is provided with a flexible multifunctional layer, a curved elastic electrode electrically connected to the multifunctional layer is provided inside the flexible multifunctional layer as an upper electrode, a lower electrode is provided below the upper electrode, an insulating layer is provided between the upper electrode and the lower electrode, and the downward projection of the upper electrode covers at least part of the area of ​​the lower electrode, and the deformation of the flexible multifunctional layer under the external force drives the upper electrode to change the contact area with the insulating layer; The contactless measurement module is provided with a capacitance-to-digital conversion circuit of the coupling processing module, and the capacitance-to-digital conversion circuit couples each electrode through a switch array for the capacitance formed between the upper electrode and the lower electrode in the first sensor unit.

16. The measuring device according to claim 9, characterized in that: The sensor is configured to include a tension detection sensor, a surface of the tension detection sensor for contacting the surface being provided with an adhesive layer; The tension detection sensor is coupled to the actuator, and the actuator is used to drive the tension detection sensor during measurement. The sensor moves in a normal direction in contact with the surface.

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