Reversible kink instability drives ultrafast jumping in nematodes and soft robots

Area of Science:

• Biomechanics
• Soft Robotics
• Nematology

Background:

• Entomopathogenic nematodes (EPNs) possess a unique bending-elastic instability, termed a kink, previously unproven to enhance jumping.
• This instability is hypothesized to be crucial for airborne launch and locomotion.

Purpose of the Study:

• To provide evidence that the kink instability is crucial for EPN jumping performance.
• To explore the mechanisms and implications of this kink using a bioinspired physical model.
• To investigate the potential of harnessing kink instabilities for soft robotic applications.

Main Methods:

• Demonstrated active aspect ratio modulation and α-shaped loop formation in EPNs.
• Utilized a soft jumping model (SoftJM) for mechanism exploration and experimentation.
• Quantified cuticle stiffness using atomic force microscopy and compared with *Caenorhabditis elegans*.

Main Results:

• EPNs achieve heights of 20 body lengths and power of ~10^4 W/kg through rapid loop opening.
• EPNs control jump direction by adjusting head position and center of mass.
• A stiffness-modified SoftJM achieved jumps of ~25 body lengths.

Conclusions:

• The reversible kink instability enhances energy storage and launch performance in EPNs.
• Harnessing kink instabilities offers a novel approach for designing limbless soft robots capable of bidirectional jumping.
• This research has implications for robotic locomotion on complex terrains and planetary exploration.