I work at interface between engineering and biology. My current research focuses on animal movement that uses energy stored in elastic elements.  While this can produce faster and sometimes more efficient movements than muscle alone, it also comes with challenges. Elastically driven systems require tight tuning between each of the elements.  How then, does an elastic system stay in tune when each of these parts can change?  And over what timescales does that turning occur?

Robobird: an animal model for exoskeleton adapation

In collaboration with Jonas Rubenson and Greg Sawicki, I have built a lower limb orthosis for a guinea fowl. We’re exploring the long-term musculoskeletal and neural adaptations to wearable rotobtics and trying to understand  the sensory feedback mechanisms are by which animals adapt to their use.

 Plasticity of elastic systems

Guinea fowl are a great system to study the plasticity of a elastic system since they store and release elastic energy through the stretch and recoil of long tendons in their limbs and they also grow to maturity in 6 months.  As some components of a muscle-tendon-unit change during growth in response to environmental conditions, we’d like to know whether other components also change to keep the system well-tuned and efficient. In collaboration with Jonas Rubenson, I’ve been looking at how musculoskeletal and tendon properties vary between guinea fowl raised with large amounts of activity and those with restricted movement.

Guinea fowl running on a treadmill

Musculoskeletal Modeling

A musculoskeletal model allows us to explore complex dynamics that result from the interaction of many many elastic elements.

Sensory feedback to adjust elastic systems

Cane toads use elastic elements in their forelimbs as brakes to absorb impacts during landing.   In collaboration with Gary Gillis, I’ve been exploring whether anurans, like many running species, prepare for landing by predicting the timing and intensity of impact from sensory feedback. To do this, we’ve performed several experiments to conflict or ablate sensory information and evaluated the influence on landing preparation.

Here we  were testing whether toads prepare each forelimb for landing individually by having them land with one limb before the other and measuring muscle timing and activity levels.

 

What makes a ‘good’ spring?

Springs are commonly treated as idealized objects that return all the energy stored in them.  But, like any actuator, springs face limitations. Understanding the conditions in which different spring material and geometric properties limit spring efficiency is crucial to understanding how difference species tune power amplified systems. In collaboration a Sheila Patek and Al Crosby, we’ve been exploring how spring properties relate to their performance.