In recent years, thanks to the breakthrough advancements in generative artificial intelligence technology, the humanoid robot industry has gained increasing attention. Domestic and international tech companies, including Tesla, Huawei, Xiaomi, Tencent, and Yushuo Technology, have all entered the sector and intensified their efforts.

Industry analysis reports show that in 2023, China's humanoid robot industry entered a period of explosive growth, with the market size reaching 3.91 billion yuan, a year-on-year increase of 85.7%. It is expected that the humanoid robot industry will continue to grow rapidly in 2024 and 2025, and by 2026, the market size of China's humanoid robot industry will exceed 20 billion yuan.

(ULSrobotics)

Robotic body lightweighting technology is one of the key areas of research, as it addresses issues such as close collaboration between humans and robots in confined spaces, ensuring safety during joint operations to prevent injury from the machine, and enhancing the robot's mobility and flexibility.

The skeletal structure of the limbs serves as the basic framework that supports various movements of humanoid robots.   Its application scenarios include shell materials, spine, upper arms, forearms, thighs, lower legs, and other structural components.   Common materials used include steel, aluminum alloys, magnesium alloys, carbon fiber, and polymer materials.   Under the trend of lightweighting, "replacing steel with plastic" has become a hot topic in the manufacturing of humanoid robots.

This article will introduce eight commonly used polymer materials in humanoid robots.

1. Polyether Ether Ketone (PEEK)
In early 2024, Tesla showcased the Optimus-Gen2 humanoid robot, which reduced its weight by 10 kilograms and increased walking speed by 30% without sacrificing performance, thanks to a lightweight material—PEEK. PEEK is one of the key raw materials used in the production of humanoid robots.

PEEK, or Polyetheretherketone, is a high-performance polymer composed of repeating units that contain one ketone group and two ether groups in the main chain structure. It is classified as a specialty polymer and is one of the highest in terms of overall performance and product value among engineering plastics.

PEEK has a comprehensive range of properties. It outperforms most other specialty engineering plastics in terms of rigidity, while also offering toughness, mechanical strength, and excellent resistance to heat, wear, and corrosion.

With a high specific strength and low density, PEEK can significantly reduce the material's weight while meeting strength requirements, making it an ideal solution for lightweight applications. It has broad potential in industrial sectors for "plastic replacing steel" applications.

Chart: PEEK has significant advantages in physical and chemical properties.

PEEK can enhance its overall performance by being compounded with materials such as carbon fiber and glass fiber.   Leveraging the high tensile strength and elastic modulus of carbon fiber, carbon fiber-reinforced PEEK materials exhibit improved toughness, impact resistance, specific strength, and thermal stability. These properties make them suitable for applications in robotic arms, joint linkages, and other components, with significant potential in humanoid robots.

With an estimated demand of 10 million humanoid robots, the use of PEEK for lightweight solutions is expected to drive an additional 105,000 tons of PEEK demand, resulting in a PEEK market size of 52.5 billion RMB.

Chart: PEEK Market Potential in Humanoid Robots

2. Polyamide (PA)
The robot Poppy, designed by Ensta ParisTech and Flowers Lab from France, has all parts 3D printed using Selective Laser Sintering (SLS) technology, with the material being Polyamide (PA), except for the motors and electronic circuits.

Nylon, also known as Polyamide (PA), is a general term for thermoplastic resins with repeated amide groups—NHCO—on the molecular backbone. It is widely used across various industries and is the most commonly used type among the five major engineering plastics. Nylon has low density, high mechanical strength, stiffness, hardness, and toughness, excellent aging resistance, good vibration-damping properties, superior sliding properties, outstanding wear resistance, and good machinability. It also exhibits precise control during machining, with no creep and excellent anti-wear performance, as well as good dimensional stability. The main drawback is its high water absorption.

3. PC/ABS
The humanoid robot NAO, developed by SoftBank Group, is primarily made of Polycarbonate-ABS plastic, Polyamide, and Carbon Fiber Reinforced Thermoplastic materials.

ABS engineering plastic, also known as PC+ABS (engineering plastic alloy), is commonly referred to as plastic alloy in the chemical industry. It is named PC+ABS because this material combines the excellent heat resistance, weatherability, dimensional stability, and impact resistance of PC resin with the excellent processing fluidity of ABS resin. As a result, it is used in products with thin walls and complex shapes, maintaining both its outstanding performance and the moldability of plastic materials composed of an ester.

The main drawback of ABS engineering plastic is its heavy weight and poor thermal conductivity. Its molding temperature is determined by the temperature range between the two base materials, typically around 240-265°C. If the temperature is too high, ABS will decompose, and if it's too low, the fluidity of the PC material will be inadequate.