A method and device for modulating friction between superlubricating interfaces

Abstract

The present invention relates to a method and device for modulating the friction between superlubricating interfaces. The method comprises: 1) placing superlubricating material layers at the interfaces of two objects undergoing relative sliding motion respectively, so that the superlubricating material layers have superlubricating properties and form superlubricating interfaces; 2) at least one of the two objects undergoing relative sliding motion comprises, in addition to the superlubricating material layer, a dielectric layer and a conductive layer, wherein the dielectric layer is located between the superlubricating material layer and the conductive layer; 3) applying a bias voltage between the conductive layer and the superlubricating material layer to change the electrical state of the surface of the superlubricating material layer, thereby modulating the friction between the superlubricating interfaces. The present invention also realizes a transmission device and a braking device based on modulating the friction between superlubricating interfaces. The present invention can realize the electrostatic reversible modulation of the superlubricating friction of micro-nano solid interface contact, and can be applied to extreme working conditions such as high pressure, high temperature, and high speed of micro-electromechanical systems.

Description

Technical Field

[0001] The invention relates to the field of micro-electromechanical systems, and in particular to a method and a device for modulating friction between super-lubricating interfaces. Background Art

[0002] With the popularization of intelligence and the development of micro-nano technology, more and more new micro-nano electromechanical devices have emerged, and they have great application potential in information communication, aerospace, biomedicine, environmental health, scientific research instruments and other fields. However, as the size of devices continues to decrease and the specific surface area of ​​materials increases, surface problems such as adhesion, friction and wear at micro-nano interfaces become more and more significant, leading to increased energy consumption, device performance degradation, and shortened device life. "Superlubrication" technology (i.e., friction coefficient as small as 10 due to non-commensurate contact) -3 The emergence of nano-tribology (or even lower) has brought revolutionary changes to the field of nano-tribology (Chinese patent application number: 201310355985.5). This phenomenon of extremely low or even zero interlayer friction and no wear is of great significance to reducing friction loss and energy dissipation. On the other hand, if this "zero friction" can be reversibly modulated to a set value, it can also be applied to the braking and transmission functions of micro-nano systems. Macro-scale mechanical brakes achieve braking by generating friction torque by pressing contact and disengaging contact. However, at the micro-nano scale, as mentioned earlier, the material adhesion problem is very serious and it is impossible to achieve controllable debonding of materials. Therefore, it may be possible to achieve transmission and braking functions at the micro-nano scale based on superlubrication technology and reversible friction modulation methods. However, existing research on the influencing factors of "superlubrication" friction mostly focuses on contact area, sliding speed, pressure, temperature, material system, etc., and cannot be applied to the large-scale reversible modulation of "superlubrication" friction of a specific structure that has been designed.

[0003] Electrostatic interaction is an important means of controlling the movement of mechanical components in micro-nano electromechanical systems. The Coulomb interaction it brings will affect surface adsorption and friction behavior. As a mature control method for micro-electromechanical systems, electrostatic interaction can also be used to achieve controllable modulation of micro-nano friction. In fact, some methods for electrically modulating micro-nano friction have been reported in the literature, including changing the morphology of organic molecular assemblies by electrostatic interaction to modulate friction (Langmuir 2009, 25 (20), 12114-12119), applying bias to change the carrier concentration of silicon PN junction to increase friction (Science 2006, 313 (5784), 186), using oscillating voltage to make the cantilever beam resonate to reduce friction (Nature nanotechnology 2006, 1 (1), 20-21), and applying bias between the two-dimensional material substrate and the atomic force microscope tip to increase friction (Applied Surface Science 2018, 455, 527-532; Physics Letters A 2020, 384(7), 126166), but most of them are limited to the electrical modulation of the point contact friction between the atomic force microscope tip and different materials, which is very different from the actual sliding friction in the form of surface contact in micro-electromechanical systems. At present, there is no electrostatic modulation of the friction in the form of surface contact at the micro-nano interface, let alone "superlubricity" friction.

[0004] Therefore, we hope to find a method and device that will not destroy the "super-lubrication" friction properties of the micro-nano interface, and can reversibly modulate the friction between the super-lubrication interfaces, so as to achieve a series of functions such as transmission or braking, and apply it to micro-nano mechanical systems. Summary of the invention

[0005] In view of this, one of the purposes of the present invention is to solve the technical problem that the friction between superlubricating interfaces is difficult to controllably modulate, and to provide a method and device for modulating the friction between superlubricating interfaces.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for modulating friction between superlubricating interfaces, comprising at least the following steps:

[0008] 1) Placing a superlubricating material layer at the interface of two objects undergoing relative sliding motion, so that the superlubricating material layer has superlubricating properties and forms a superlubricating interface;

[0009] 2) at least one of the two objects that undergo relative sliding motion comprises, in addition to the superlubricating material layer, a dielectric layer and a conductive layer, wherein the dielectric layer is located between the superlubricating material layer and the conductive layer;

[0010] 3) applying a bias voltage between the conductive layer and the superlubricating material layer to change the electrical state of the surface of the superlubricating material layer, thereby modulating the friction force of the superlubricating interface.

[0011] Preferably, the superlubricating material layer is selected from one or more of the following materials: two-dimensional materials, two-dimensional heterogeneous nanocomposite powders, diamond-like films, etc. The two-dimensional material can be one or more of graphene, transition chalcogenide metal compounds, hexagonal boron nitride, black phosphorus, and MXene.

[0012] Preferably, the dielectric layer is selected from one or more of the following materials: silicon oxide, tantalum oxide, hafnium oxide, tungsten oxide, zinc oxide, magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, nickel oxide, germanium oxide, etc.

[0013] Preferably, the conductive layer is selected from one or more of the following materials: heavily doped semiconductors, metals, etc. The heavily doped semiconductors may be heavily doped silicon, etc.; the metals may be gold, aluminum, copper, platinum, etc.

[0014] The friction modulation effect is achieved by applying a bias voltage between at least one of the superlubricating material layers and the conductive layer, and different electrical states are designed in another superlubricating material layer to respectively meet the increased and decreased friction modulation effects.

[0015] The invention discloses a transmission device based on modulating the friction between superlubricity interfaces, comprising a driving body and a driven body that slide relative to each other; superlubricity material layers are respectively placed on the contact interfaces of the driving body and the driven body to make them have superlubricity characteristics; wherein the driving body and / or the driven body, in addition to the superlubricity material layer, also comprises a dielectric layer and a conductive layer, and the dielectric layer is located between the superlubricity material layer and the conductive layer; the transmission device based on modulating the friction between superlubricity interfaces also comprises a device for applying voltage between the superlubricity material layer and the conductive layer; when the driving body contacts the driven body and slides relative to each other, a voltage is applied between the conductive layer and the superlubricity material layer to change the electrical state of the surface of the superlubricity material layer, increase the interface friction force or cancel the interface friction force; the increase of the interface friction force enables the driving body to drive the driven body to move, thereby realizing the transmission function; the cancellation of the interface friction force enables the driving body and the driven body to be in a superlubricity state, thereby canceling the transmission function.

[0016] Optionally, by periodically applying voltage, periodic transmission between the driving body and the driven body is achieved, and the reciprocating motion of the driving body is converted into unidirectional continuous motion of the driven body.

[0017] The present invention also discloses a braking device based on modulating the friction between superlubricating interfaces, comprising a moving body and a braking body that undergo relative sliding; superlubricating material layers are respectively placed on the contact interfaces of the moving body and the braking body to make them have superlubricating properties; wherein at least the braking body, in addition to the superlubricating material layer, also comprises a dielectric layer and a conductive layer, and the dielectric layer is located between the superlubricating material layer and the conductive layer; the braking device based on modulating the friction between superlubricating interfaces also comprises a device for applying a voltage between the superlubricating material layer and the conductive layer; when the moving body contacts the braking body and undergoes relative sliding, a bias voltage is applied between the conductive layer and the superlubricating material layer to change the electrical state of the surface of the superlubricating material layer, thereby increasing the interface friction force so that the speed of the moving body is reduced or even stopped, thereby realizing the braking function.

[0018] Preferably, the conductive layer is selected from one or more of the following materials: heavily doped semiconductors and metals. The heavily doped semiconductors may be heavily doped silicon, etc.; the metals may be gold, aluminum, copper, platinum, etc.

[0019] Preferably, the dielectric layer is selected from one or more of the following materials: silicon oxide, tantalum oxide, hafnium oxide, tungsten oxide, zinc oxide, magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, nickel oxide, germanium oxide, etc.

[0020] Preferably, the superlubricating material layer is selected from one or more of the following materials: two-dimensional materials, two-dimensional heterogeneous nanocomposite powders, diamond-like films, etc. The two-dimensional material can be one or more of graphene, transition chalcogenide metal compounds, hexagonal boron nitride, black phosphorus, and MXene.

[0021] The possible mechanisms for modulating the friction of superlubricating interfaces are: Figure 1As shown, by applying a bias voltage between the first superlubricating material layer on the conductive layer and the dielectric layer, the charge density on the surface of the first superlubricating material layer increases. For micro-nano friction, the magnitude of the sliding friction force is the potential barrier height that needs to be overcome during the sliding process. Due to the Coulomb interaction caused by the increase in charge density, electrostatic attraction and repulsion occur between the first superlubricating material layer and the second superlubricating material layer, the interlayer spacing of the superlubricating material changes, and the interlayer potential energy changes, resulting in an increase or decrease in the height of the sliding friction barrier. When the interface between the first superlubricating material layer and the second superlubricating material layer slides relative to each other, the interlayer sliding friction force increases or decreases. Since the interlayer sliding process of the superlubricating material is a vacuum van der Waals gap, charge tunneling will not occur under a low interlayer electric field. The charge density on the surface of the superlubricating material can be maintained during the sliding process, ensuring the effect of friction modulation. The bias voltage applied between the first superlubricating material layer on the conductive layer and the dielectric layer is removed, the charge density on the surface of the first superlubricating material layer is restored to its original state, and the interlayer sliding friction force is restored, so that the friction force can be reversibly modulated. Different electrical states are designed for the second superlubricating material layer that slides relative to the first superlubricating material layer, so as to realize electrostatic attraction or repulsion between the first superlubricating material layer and the second superlubricating material layer, so as to meet different friction modulation effects. When the second superlubricating material layer carries a charge with a different polarity from the first superlubricating material layer, there is electrostatic attraction between the layers, the distance between the superlubricating material layers decreases, the friction energy barrier between the layers increases, and the sliding friction force increases. When the second superlubricating material layer and the first superlubricating material layer have charges of the same polarity, there is electrostatic repulsion between the layers, the distance between the superlubricating material layers increases, the friction energy barrier between the layers decreases, and the sliding friction force decreases.

[0022] In summary, the present invention proposes a method and device for modulating the friction between superlubricating interfaces. Compared with the previous method of electrically modulating micro-nano friction, the present invention can realize the electrostatic reversible modulation of the superlubricating friction between micro-nano solid interfaces, and can be applied to extreme working conditions such as high pressure, high temperature, and high speed of micro-electromechanical systems. The electrical modulation design structure is also highly compatible with the current micro-electromechanical system processes and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a method for modulating friction between superlubricating interfaces in Example 1 of the present invention, wherein: 1-conductive layer; 2-dielectric layer; 3-first superlubricating material layer; 4-second superlubricating material layer; 5, 6-objects in relative sliding motion; there is an electrical connection between the conductive layer and the first superlubricating material layer, and the second superlubricating material layer can be designed with different electrical connections to achieve different modulation effects.

[0024] Figure 2This is a schematic diagram of a transmission device based on modulating the friction between superlubricating interfaces in Example 2 of the present invention, wherein: 11 is a driving wheel; 12 is a conductive layer; 13 is a dielectric layer; 14 is a superlubricating material layer; 15 is a driven wheel.

[0025] Figure 3 This is a schematic diagram of a braking device based on modulating the friction between superlubricating interfaces in Example 3 of the present invention, wherein: 21 is a metal layer; 22 is a dielectric layer; 23 is a nanosheet molybdenum sulfide slider; 24 is a nanosheet molybdenum sulfide slider; 25 is a cantilever beam for manipulating the movement of the slider 23.

[0026] Figure 4 This is a schematic diagram of a device for reducing friction between superlubricating interfaces in Example 4 of the present invention, wherein: 31-metal layer; 32-medium layer; 33-nanosheet boron nitride slider; 34-nanosheet boron nitride slider; 35-medium layer; 36-metal layer. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below through embodiments in conjunction with the accompanying drawings, but the scope of the present invention is not limited in any way.

[0028] Embodiment 1:

[0029] like Figure 1 As shown, this embodiment shows a method for modulating the friction between superlubricating interfaces, comprising the following steps:

[0030] 1) A first superlubricating material layer 3 and a second superlubricating material layer 4 are placed at the interface of two objects 5 and 6 that undergo relative sliding motion, respectively, so that they have superlubricating properties and form a superlubricating interface.

[0031] 2) At least one of the two objects 5 and 6 that undergo relative sliding motion includes a dielectric layer 2 and a conductive layer 1 in addition to a superlubricating material layer. Figure 1 The case where the object 5 includes the dielectric layer 2 and the conductive layer 1 and the object 6 does not include the dielectric layer 2 and the conductive layer 1 is illustrated. The dielectric layer 2 is located between the first superlubricating material layer 3 and the conductive layer 1.

[0032] 3) Applying a bias voltage between the conductive layer 1 and the first superlubricating material layer 3 to change the electrical state of the surface of the first superlubricating material layer 3, thereby modulating the friction force of the superlubricating interface.

[0033] Embodiment 2:

[0034] like Figure 2As shown, this embodiment shows a transmission device based on modulating the friction between superlubricating interfaces, including: a driving wheel 11 and a driven wheel 15 that undergo relative sliding, a conductive layer 12 located outside the driving wheel 11 and composed of metal, a dielectric layer 13 located outside the conductive layer 12, and a superlubricating material layer 14 located outside the dielectric layer 13; the driven wheel 15 also has the same structure of the conductive layer 12, the dielectric layer 13 and the superlubricating material layer 14.

[0035] When the driving wheel 11 and the driven wheel 15 come into contact and slide relative to each other, a bias voltage is applied between the conductive layer 12 and the superlubricating material layer 14 to change the surface electrical state of the superlubricating material layer, increase the interface friction, and make the driving wheel drive the driven wheel to move, thus realizing the transmission function; or cancel the interface friction, so that the driving body and the driven body are in a superlubricating state, canceling the transmission function, but because the interface is in a superlubricating state, the movement can be maintained. The reciprocating motion of the superlubricating structure can be realized by applying a periodic voltage.

[0036] Embodiment 3:

[0037] like Figure 3 As shown, the present embodiment shows a braking device based on modulating the friction between super-lubricating interfaces, comprising: a metal layer 21, a dielectric layer 22 located on the metal layer 21 and composed of silicon oxide, a nanosheet molybdenum sulfide slider 23 located on the dielectric layer 22, a nanosheet molybdenum sulfide slider 24 located above the nanosheet molybdenum sulfide slider 23, and a cantilever beam 25 for manipulating the movement of the nanosheet molybdenum sulfide slider 24, wherein the metal layer 21 and the nanosheet molybdenum sulfide slider 23 are connected by an external voltage source, and the nanosheet molybdenum sulfide slider 24 is at a suspended potential.

[0038] When a bias is applied between the metal layer 21 and the nanosheet molybdenum sulfide slider 23, the semiconductor nanosheet molybdenum sulfide slider 23 is charged by the metal-insulator-semiconductor structure capacitor, so that the surface charge density of the nanosheet molybdenum sulfide slider 23 increases. For example, when the silicon oxide thickness is 300nm and the bias voltage is 1V, the surface charge of molybdenum sulfide is calculated to be about 1.1495*10-4C / m2. When the nanosheet molybdenum sulfide slider 23 and the nanosheet molybdenum sulfide slider 24 slide relative to each other, an energy barrier caused by Coulomb interaction is introduced, resulting in an increase in the total friction energy barrier and an increase in the sliding friction force. The movement speed of the nanosheet molybdenum sulfide slider 24 is reduced or even stopped, achieving a braking effect. When the bias between the metal layer 21 and the nanosheet molybdenum sulfide slider 23 is removed, the surface charge of the molybdenum sulfide is conducted away through the wire, and the corresponding Coulomb interaction energy barrier disappears, resulting in the total friction energy barrier returning to its original state, and the sliding friction force returning to its original state. In this way, the reversible increase and modulation of the sliding friction force of the micro-nano interface can be achieved.

[0039] Embodiment 4:

[0040] like Figure 4 As shown, a device for reducing friction between superlubricating interfaces shown in this embodiment includes: a metal layer 31, a dielectric layer 32 located on the metal layer 31 and composed of silicon oxide, a nanosheet boron nitride slider 33 located on the dielectric layer 32, a nanosheet boron nitride slider 4 located above the nanosheet boron nitride slider 3, a dielectric layer 35 located above the nanosheet boron nitride slider 34, and a metal layer 36 located above the dielectric layer 35, wherein the metal layer 31 and the nanosheet boron nitride slider 33 are connected by an external voltage source, and the nanosheet boron nitride slider 34 and the metal layer 36 are connected by an external voltage source, and the two voltage sources have opposite polarities.

[0041] When a bias is applied between the metal layer 31 and the nanosheet boron nitride slider 33, the insulating nanosheet boron nitride slider 33 is charged by the metal-insulator-insulator structure capacitor, so that the surface charge density of the nanosheet boron nitride slider 33 increases. At the same time, a reverse bias is applied between the nanosheet boron nitride slider 34 and the metal layer 36, so that the surface of the nanosheet boron nitride slider 34 carries a charge with the same polarity as the surface of the nanosheet boron nitride slider 33. When the nanosheet boron nitride slider 33 and the nanosheet boron nitride slider 34 slide relative to each other, an energy barrier caused by Coulomb interaction is introduced, and the energy barrier is opposite in sign to the friction energy barrier caused by the van der Waals force, resulting in a decrease in the total friction energy barrier and a decrease in the sliding friction force. On the other hand, it is difficult for the insulating boron nitride slider to transfer charge, and an electrostatic repulsion force is generated between the nanosheet boron nitride slider 33 and the nanosheet boron nitride slider 34, resulting in a decrease in the normal support force between the layers, which also reduces the sliding friction force between the nanosheet boron nitride slider 3 and the nanosheet boron nitride slider 34. When the bias between the metal layer 31 and the nanosheet boron nitride slider 33 is removed, the surface charge of the boron nitride is conducted away through the wire, and the corresponding Coulomb interaction dominant energy barrier disappears, causing the total friction energy barrier to return to its original state, and the sliding friction force to return to its original state. In this way, the controllable reduction modulation of the sliding friction force of the micro-nano interface can be achieved.

[0042] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. It can be understood by those skilled in the art that various replacements, changes and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the contents disclosed in the embodiments of this specification, and the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A transmission device based on modulating the friction between superlubricating interfaces, characterized in that: The invention comprises a driving body and a driven body which slide relative to each other; a superlubricating material layer is placed on the contact interface of the driving body and the driven body respectively, so that the superlubricating material layer has superlubricating properties; wherein the driving body and / or the driven body, in addition to the superlubricating material layer, also comprises a dielectric layer and a conductive layer, and the dielectric layer is located between the superlubricating material layer and the conductive layer; the transmission device based on modulating the friction between the superlubricating interfaces also comprises a device for applying a voltage between the superlubricating material layer and the conductive layer; When the active body and the driven body contact and slide relative to each other, a voltage is applied between the conductive layer and the superlubricating material layer to change the surface electrical state of the superlubricating material layer, thereby increasing the interface friction or canceling the interface friction; the increase in the interface friction enables the active body to drive the driven body to move, thereby realizing the transmission function; the cancellation of the interface friction enables the active body and the driven body to be in a superlubricating state, thereby canceling the transmission function.

2. The transmission device based on modulating the friction between superlubricating interfaces according to claim 1, characterized in that: By periodically applying voltage, periodic transmission between the active body and the driven body is achieved, and the reciprocating motion of the active body is converted into unidirectional continuous motion of the driven body.

3. The transmission device based on modulating the friction between superlubricating interfaces according to claim 1, characterized in that: The conductive layer is selected from one or more of the following materials: heavily doped semiconductors, metals; the heavily doped semiconductors are heavily doped silicon; the metals are gold, aluminum, copper, or platinum; the dielectric layer is selected from one or more of the following materials: silicon oxide, tantalum oxide, hafnium oxide, tungsten oxide, zinc oxide, magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, nickel oxide, germanium oxide; the superlubricating material layer is selected from one or more of the following materials: two-dimensional materials, two-dimensional heterogeneous nanocomposite powders, diamond-like films; the two-dimensional materials are one or more of graphene, transition chalcogenide metal compounds, hexagonal boron nitride, black phosphorus, and MXene.

4. A braking device based on modulating the friction between superlubricating interfaces, characterized in that: It comprises a moving body and a braking body which slide relative to each other; superlubricating material layers are respectively placed at the contact interfaces of the moving body and the braking body so as to make them have superlubricating properties; wherein at least the braking body, in addition to the superlubricating material layer, also comprises a dielectric layer and a conductive layer, and the dielectric layer is located between the superlubricating material layer and the conductive layer; the braking device based on modulating the friction between the superlubricating interfaces also comprises a device for applying voltage between the superlubricating material layer and the conductive layer; when the moving body contacts the braking body and slides relative to each other, a bias voltage is applied between the conductive layer and the superlubricating material layer to change the electrical state of the surface of the superlubricating material layer, thereby increasing the interface friction force so that the speed of the moving body is reduced or even stopped, thereby realizing the braking function.

5. The braking device based on modulating the friction between superlubricating interfaces as claimed in claim 4, characterized in that: The conductive layer is selected from one or more of the following materials: heavily doped semiconductors, metals; the heavily doped semiconductors are heavily doped silicon; the metals are gold, aluminum, copper, or platinum; the dielectric layer is selected from one or more of the following materials: silicon oxide, tantalum oxide, hafnium oxide, tungsten oxide, zinc oxide, magnesium oxide, zirconium oxide, titanium oxide, aluminum oxide, nickel oxide, germanium oxide; the superlubricating material layer is selected from one or more of the following materials: two-dimensional materials, two-dimensional heterogeneous nanocomposite powders, diamond-like films; the two-dimensional materials are one or more of graphene, transition chalcogenide metal compounds, hexagonal boron nitride, black phosphorus, and MXene.

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