A Comprehensive Guide to Air Bearings: An In-Depth Overview of Principles, Classifications, Characteristics, and Applications

I. What is an air bearing?

Bearings are the cornerstone of modern industry: from automobiles to machine tools, from household appliances to spacecraft, virtually every rotating machine relies on them. Yet most people are familiar only with rolling bearings and fluid‑film bearings—devices that support loads using balls, rollers, or an oil film. So, is there a type of bearing that requires neither balls nor lubricant, operating solely on “air”?

The answer is yes—this is it. Air bearing (Air Bearing), also known as Air-bearing 。

Air bearing It refers to a sliding bearing that uses gas as a lubricant. The most commonly used gas lubricant is air; nitrogen, argon, hydrogen, helium, or carbon dioxide may also be employed as needed. During operation, a pressurized gas film forms between the bearing’s sliding surfaces, fully supporting the load and enabling non-contact relative motion between the moving and stationary components.

The concept of air bearings can be traced back as early as 1854, when the French engineer G. A. I’An proposed using gas as a lubricant. In 1896, the world’s first air bearing was developed. However, it was not until after the 1950s—when precision manufacturing technologies and gas dynamics theory had matured—that air bearings were truly introduced into engineering applications.

II. Classification and Operating Principle of Air Bearings

Based on the formation mechanism of the pressurized gas film, air bearings are primarily classified into three major types:

1. Aerostatic bearing

Air‑film bearings rely on an external air source to supply compressed air (or other gases), with the compressed air flowing through the supply ports. Throttle A minute clearance is introduced between the bearing and the moving component, within which a hydrostatic air film that supports the load is established, thereby levitating the moving part.

Throttle It is the core component of a hydrostatic bearing. When the load varies, the restrictor automatically adjusts the gas flow rate and velocity entering the gap, thereby maintaining a stable air‑film thickness. Depending on the throttling mechanism, hydrostatic bearings can be classified into types such as orifice‑type, slit‑type, porous‑material, and surface‑throttled bearings.

of the hydrostatic bearing The greatest advantage Yes: It can operate normally at any speed, even at zero speed. It is also currently used in industrial applications… Most extensive Types of air bearings.

2. Aerodynamic Bearing

Air‑film bearings do not rely on an external air supply; instead, they utilize the space between the rotor journal and the bearing liner. Relative motion to generate an air film. When the rotor spins at high speed, the viscous gas is drawn into the converging wedge-shaped gap between the two surfaces, where it is compressed to create a pressure field that supports the rotor. Because no external air supply is required, hydrodynamic bearings are also referred to as “ Self-acting bearing ”。

Common types of aerodynamic bearings include foil bearings, tilting-pad bearings, stepped bearings, and herringbone‑groove bearings, among others. Among these, Foil Air Bearing It is an important and rapidly developing branch in recent years, employing flexible foil as its supporting structure and offering advantages such as high rotational speed, high-temperature resistance, and the elimination of the need for auxiliary lubrication.

3. Extruded Film Bearing

Squeeze-film bearings generate a periodic pressure air film in the clearance through high-frequency vibrations of the bearing surface, thereby supporting the load. These bearings are relatively uncommon and are typically used in specialized precision applications.

In addition, depending on the direction of the load they bear, air bearings can also be classified as Radial bearing (Withstand radial loads), Thrust bearing (承受 axial load) and Radial-thrust combined bearing 。

III. Core Performance Parameters of Air Bearings

The performance metrics of air bearings are remarkable. In Rotational speed In terms of performance, air bearings can reach speeds exceeding 350,000 rpm, with some records even reporting up to 1.3 million rpm. In Accuracy In this regard, the radial runout can be as low as 0.025 µm, and the axial and radial rotational accuracy can exceed 0.1 µm. In… Stiffness In terms of performance, the axial stiffness can reach 250 newtons per micrometer, capable of supporting a load of 500 kilograms. In… Vibration In this regard, the vibration can be reduced to 0.2 mm/s.

What do these parameters mean? Simply put: air bearings can operate at speeds far exceeding those of conventional bearings, while maintaining an order of magnitude higher precision and extremely low vibration.

IV. The Six Core Advantages of Air Bearings

1. Extremely low friction

At room temperature, the viscosity of air is only that of No. 10 mechanical oil. One in five thousand The frictional resistance of a bearing is directly proportional to the viscosity of the lubricant; therefore, the frictional resistance of an air bearing is significantly lower than that of a liquid-lubricated bearing. Near-zero friction This means extremely low power consumption and minimal heat generation.

2. Extremely wide speed range

Due to low friction and minimal temperature rise, air bearings exhibit a temperature increase of no more than 20–30°C at 50,000 rpm. Hydrostatic bearings can even… Zero speed It operates under normal conditions, a capability that hydrodynamic bearings cannot achieve. This characteristic enables air bearings to perform reliably across a wide range of operating conditions, from low-speed precision positioning to ultra-high-speed rotation.

3. Extremely wide temperature tolerance range

The gas remains in the gaseous state over an extremely wide temperature range, and its viscosity is only slightly affected by temperature. For example, when the temperature rises from 20°C to 100°C, the viscosity of air increases by only 23%. The operating temperature range of air bearings can reach -265℃ to 1650℃ This characteristic confers upon it irreplaceable advantages in fields such as cryogenic refrigeration equipment and high-temperature gas turbines.

4. Extremely high accuracy and long-term stability

Air bearings have no mechanical contact, therefore No wear — Accuracy does not degrade over time. This characteristic is critical for applications such as semiconductor manufacturing and precision metrology, which demand long-term stability of measurement accuracy.

5. Clean and pollution-free

The only “lubricant” for air bearings is air (or another gas), and no lubricating oil is required. This means… No oil mist contamination. , making it ideally suited for cleanrooms, vacuum environments, and applications in the food and pharmaceutical industries where ultra‑high cleanliness is required.

6. Theoretical lifespan is infinite

Due to the absence of solid contact and wear, under conditions of uninterrupted clean-air supply, air bearings… The theoretical lifespan is infinite. . Meanwhile, since no lubrication is required, it also Nearly maintenance-free 。

V. Limitations and Challenges of Air Bearings

Of course, air bearings are not a panacea. They also have certain inherent limitations:

Low load-bearing capacity The load-carrying capacity of a gas‑film bearing is only that of a liquid‑film bearing of the same size. A few thousandths . The typical load limit per unit projected area is approximately 0.36 MPa, which makes it difficult to apply in the heavy‑machinery sector.

The machining accuracy requirements are extremely stringent. . To enhance load-carrying capacity and air-film stiffness, the air-film gap in air bearings is typically less than 0.015 millimeters This places extremely stringent demands on the machining accuracy of these parts.

A clean air source is required. Air bearings are highly sensitive to the quality of the supplied air; dust, oil mist, or moisture can all compromise the air film and damage the bearing surfaces. Therefore, a sophisticated air‑source treatment system is required.

Not suitable for vacuum environments. In a vacuum, air bearings cannot form an air film and must be replaced with alternative support methods.

VI. Application Fields of Air Bearings

Thanks to the aforementioned characteristics, air bearings have secured an irreplaceable position in numerous high-end industries.

Semiconductor manufacturing

Air bearings are used in semiconductor manufacturing equipment. Core component In processes such as lithography, wafer inspection, and wafer dicing, air-bearing platforms deliver frictionless, vibration-free motion control with ultra‑high precision. As chip manufacturing continues to shrink, the demands on motion accuracy have reached the nanometer scale, making air bearings… The only viable option 。

Ultra-precision machining

In ultra-precision CNC machine tools, high-speed grinding spindles, and other equipment, air spindles deliver rotational speeds and precision unattainable with conventional rolling bearings. Air bearings can also… Significantly extends tool life — In the PCB drilling industry, drill bit diameters can be as small as 50 microns; only air spindles can operate at the required speeds while ensuring tool life.

Aerospace

Air foil bearings have become integral to aircraft air conditioning systems (air cycle machines). Industry standard In fields such as aero‑turbine engines and micro gas turbines, air bearings have found widespread application thanks to their advantages, including high‑temperature resistance and the elimination of the need for lubrication.

Medical equipment

In fields such as high-speed dental drills and precision medical instruments, air bearings deliver operating conditions characterized by high rotational speeds, low vibration, and zero contamination.

AI and Data Center Cooling

In 2025, China achieved an industrial breakthrough in full‑hydrodynamic air bearing technology. An AI server cooling module based on this technology offers high‑efficiency heat exchange, low‑noise operation, and energy‑saving, environmentally friendly performance, providing a groundbreaking solution for next‑generation computing infrastructure.

Other typical applications

Air bearings are also widely used in high-speed centrifuges, gyroscopic instruments, coordinate measuring machines, textile machinery, cable‑making equipment, cryogenic refrigerators, hydrogen expanders, and more.

VII. Latest Development Trends

1. Full‑flow aerodynamic bearings have achieved a breakthrough in industrialization.

In November 2025, China launched the “world’s first industrialization project for fully hydrodynamic air bearings,” marking a major breakthrough in China’s ability to break the long-standing technological blockade imposed by foreign countries in the ultra-precision bearing sector. Fully hydrodynamic air bearings are hailed as the cornerstone of the bearing industry. “Crown Pearl” Its domestic production signifies that China will no longer be subject to foreign export restrictions in critical sectors such as aerospace turbomachinery, high-precision CNC machine tools, and nuclear energy equipment.

2. New Materials and New Processes

Researchers are exploring the application of porous materials, metal rubber, ceramic matrix composites, and titanium–aluminum matrix composites in air bearings. Porous‑throttling technology holds promise for further enhancing bearing stiffness and load-carrying capacity.

3. Intelligentization and Active Compensation

With the advancement of sensor technology and control algorithms, air bearings are moving toward… Active compensation Directional Evolution—by continuously monitoring and dynamically adjusting the air‑film state, vibration is further suppressed and precision is enhanced.

4. Novel working fluids such as supercritical carbon dioxide

Institutions including the Institute of Engineering Thermophysics of the Chinese Academy of Sciences are exploring lubrication‑bearing technologies based on novel working fluids such as supercritical carbon dioxide, which hold promise for achieving gas‑lubricated operation under higher temperatures and more severe operating conditions.

VIII. Summary

Air bearing is a technology that integrates gas dynamics, precision manufacturing, and materials science. Cutting-edge technology It replaces ball bearings and lubricants with an invisible air “cushion,” enabling motion with virtually zero friction, zero wear, and ultra‑high precision—tasks that would have seemed nearly impossible for conventional bearings.

Of course, air bearings are not intended to replace all conventional bearings. Their advantages—such as high precision, high speed, and cleanliness with zero contamination—make them particularly well-suited for applications in semiconductors, aerospace, and ultra-precision manufacturing, among others. High-end sector It has become an irreplaceable choice; meanwhile, its lower load-bearing capacity and higher manufacturing costs mean that it currently focuses primarily on these “high‑end, cutting‑edge” application areas.

With the industrial breakthrough of China’s full‑flow‑pressure air bearing technology in 2025, this once‑foreign‑monopolized “bottleneck” technology is now moving toward independent and controllable development. From lithography machines to AI servers, from aircraft engines to precision medical devices, air bearings are pushing the frontiers of high‑end manufacturing at an unprecedented pace. Though perhaps not as widely recognized as rolling bearings, in fields that strive for… Ultimate precision and speed In this field, air bearings are quietly underpinning the cutting edge of modern industry.