Reversible kink instability drives ultrafast jumping in nematodes and soft robots

Area of Science:

• Biomechanics
• Soft Robotics
• Nematology

Background:

• Entomopathogenic nematodes (EPNs) display a pre-jump bending instability, hypothesized to improve launch performance.
• The precise mechanisms and benefits of this kink instability in EPNs remain largely unproven.

Purpose of the Study:

• To provide evidence that the kink instability is crucial for enhancing EPN jumping performance.
• To explore the mechanisms by which EPNs control jump direction and energy storage.
• To investigate the potential of harnessing this instability for bio-inspired soft robotic applications.

Main Methods:

• Observational studies of EPN jumping behavior and aspect ratio modulation.
• Development and use of a bio-inspired Soft Jumping Model (SoftJM).
• Computational simulations to analyze jump dynamics and control mechanisms.
• Atomic Force Microscopy (AFM) to quantify cuticle stiffness.

Main Results:

• EPNs actively form a liquid-latched loop, then rapidly open it to achieve jumps of 20 body lengths (BL) with high power output.
• The kink instability enhances energy storage from muscular force, enabling controlled bidirectional jumps.
• A stiffness-modified SoftJM achieved jumps of approximately 25 BL.

Conclusions:

• The kink instability, often a failure mode, is a key mechanism for EPNs to achieve efficient and controlled jumping.
• Harnessing kink instabilities offers a novel strategy for designing limbless soft robots capable of locomotion on complex terrains.
• This research provides insights for developing robots for planetary exploration and other applications requiring controlled jumping.