What materials are the prototype robots mainly made of?

Prototype robots from the leading humanoid robotics companies (as of late 2025) are predominantly made of the following materials:

1.Structural frame/chassis:

• Aerospace-grade aluminum alloys (e.g., 7075, 6061) – lightweight and high strength-to-weight ratio

• Magnesium alloys – used in some newer designs for even lower weight

• Carbon-fiber-reinforced polymers (CFRP) – increasingly common in limbs and torso panels (especially Tesla Optimus Gen 2, Figure 02/03, Agility Digit, Boston Dynamics Atlas new electric version)

2.Actuators and joints:

• High-performance electric motors with proprietary windings

• Harmonic drives or cycloidal gearboxes made of specialized steels

• Titanium is used in high-load joints (e.g., Boston Dynamics’ new electric Atlas, Apptronik Apollo, Sanctuary Phoenix)

3.Outer shells / cosmetic covers:

• ABS or polycarbonate plastics

• Soft silicone or TPU skins for face and hands (especially on Ameca, C.Figure 02/03, and Tesla Optimus Gen 2.5+ prototypes)

• Fabric or neoprene covers on some models (Tesla Optimus, 1X Neo)

4.Hands and end-effectors:

• Combination of aluminum/titanium skeleton + soft polymer or silicone “skin”

• Tendon-driven designs often use high-strength polymer cables (Dyneema or similar)

5.Batteries and electronics housings:

• Lithium-ion or lithium-polymer cells in custom packs

• Usually housed in magnesium or CFRP enclosures

In short:

2024–2025 humanoid robot prototypes have largely moved away from the heavy steel structures of older robots and are now built primarily from aerospace-grade aluminum, magnesium, titanium, and carbon-fiber composites, with increasing use of soft polymers/silicone for human-like appearance and safer interaction.