Humanoid robots are designed to perform most actions in a human-like manner, which requires a high degree of flexibility. To achieve such flexibility, strict control over the robot’s weight is essential. Excessive weight significantly increases the torque burden on servo motors, which in turn affects the robot’s responsiveness, payload capacity, and battery life.

Lightweight design helps reduce the weight of various components, thereby lowering the torque and power required by the drive system. This enhances the robot’s load-bearing capabilities, reduces energy consumption, and extends its operational lifespan. As such, lightweighting is critical to improving performance and enabling large-scale commercial deployment. Leading robotics manufacturers have all demonstrated a clear trend toward weight reduction in their product iterations.

For example, Tesla’s second-generation humanoid robot, Optimus Gen 2—released in December 2023—achieved a 10 kg weight reduction compared to the first generation, resulting in a 30% increase in walking speed along with significant improvements in stability, agility, and overall performance. One of the key factors behind this weight reduction was the extensive use of PEEK (Polyetheretherketone) in its bionic joints and lightweight gear components.

01
What Is PEEK Material?
Polyetheretherketone (PEEK) is a high-performance crystalline aromatic thermoplastic polymer that belongs to the polyaryletherketone (PAEK) family. It is composed of phenylene rings connected by ether and ketone linkages. Recognized as one of the highest-performing thermoplastic materials in the world, PEEK offers superior properties compared to metals and most other plastic materials.

Compared to major engineering plastics and high-performance specialty plastics, PEEK offers well-rounded performance. It not only surpasses most specialty engineering plastics in terms of rigidity, but also maintains excellent toughness, demonstrating a comprehensive mechanical profile. In addition, it exhibits outstanding resistance to heat, wear, and corrosion.

Compared to conventional metals, PEEK offers a significantly higher specific strength than steel and aluminum alloys. This allows for a substantial reduction in material weight while still meeting strength requirements, making it an ideal solution for lightweight design. In addition, PEEK also outperforms common metals in terms of electrical insulation and chemical resistance.

In summary, the outstanding comprehensive performance of PEEK makes it a promising material with broad application prospects in the lightweight design of humanoid robots.

02
Applications of PEEK in Humanoid Robots

PEEK is mainly used in the limb skeletons and joint transmission components of humanoid robots:

Joint Gears/Bearings and Other Transmission Components:
PEEK’s excellent wear resistance and self-lubricating properties, with an ultra-low friction coefficient (0.1–0.2) and low thermal expansion coefficient (approximately 30×10⁻⁶/K), make it ideal for joint gears and bearings. Its use reduces component wear, lowers energy consumption and noise. At the same time, PEEK offers high strength, good dimensional stability, and is lighter than metal materials, improving the torque-to-weight ratio of humanoid robot joints, enabling more efficient and precise movements while extending service life.

Lightweight Structural Components
PEEK can be reinforced with materials such as glass fiber or carbon fiber and used in robotic frames or housings. This allows for significant weight reduction while maintaining high rigidity, thereby improving motion efficiency.

PEEK is an ideal material for achieving the lightweight goals of humanoid robots. As the commercialization of humanoid robots continues to advance, the market potential for PEEK in this sector is expected to grow accordingly.