Crack-Resistant and Tissue-Like Artificial Muscles with Low Temperature Activation and High Power Density

Area of Science:

• Materials Science
• Robotics Engineering
• Polymer Chemistry

Background:

• Soft robotics demand artificial muscles with low modulus, high power density, and stimulus sensitivity for safe human-machine interaction.
• Durability and resistance to crack propagation are crucial for the longevity of artificial muscles during actuation cycles.

Purpose of the Study:

• To design and synthesize a novel artificial muscle platform combining low modulus, high power density, and crack resistance.
• To engineer a material that ensures safe human-machine interactions and extended service life in soft robotic applications.

Main Methods:

• Molecular engineering of a liquid crystalline network incorporating crystallizable segments and an ethylene glycol flexible spacer.
• Utilizing aza-Michael chemistry to achieve low covalent crosslinking density and high crystallinity.
• Characterization of mechanical properties, including modulus, fracture energy, fatigue threshold, and power density.

Main Results:

• The material achieved a tissue-matched modulus of 0.7 MPa and a high power density of 450 W kg⁻¹ at 40 °C.
• Demonstrated exceptional crack resistance with a fracture energy of 33,720 J m⁻² and a fatigue threshold of 2250 J m⁻².
• Exhibited no crack propagation after 500 heating-cooling cycles under a static load of 220 kPa due to crystalline domains.

Conclusions:

• The proposed material design successfully integrates low modulus, high power density, and crack insensitivity into a single artificial muscle.
• This advancement offers a promising pathway for developing robust and safe artificial muscles for advanced soft robotics and smart devices.