Hossein Salahshoor: Decoding Enigmatic Material Systems

“The brain, to me, is emblematic of all the complexities you can have in a materials system,” says Hossein “Amir” Salahshoor, new faculty member in Duke’s Department of Civil and Environmental Engineering (CEE). “It’s highly heterogeneous. It’s very nonlinear. It’s multiphasic—it contains both solid and fluid phases. It’s a multiscale system, so different things are happening at the neuron level versus the tissue level. It’s highly anisotropic, meaning that its properties vary as a function of direction, and exhibit time-dependent behavior—viscoelasticity, for example.”

Salahshoor develops computational and data-driven methods to predict and design complex materials systems, which includes trying to predict how materials respond to different forces, temperatures or other stimuli. Salahshoor’s work lies at the intersection of mechanics, data science, applied mathematics, and biology. The potential applications of his work are numerous, ranging from sustainable architectured materials discovery, to ultrasonic therapy, to the seamless integration of computation and physical components in cyberphysical systems.

“Whatever advancements we find in designing or modeling new classes of complexities in materials, or having better predictive models, there could be some ramifications in brain mechanics.”

Duke Civil and Environmental Faculty member Hossein “Amir” Salahshoor

But through all the different collaborations, he keeps coming back to the brain, because of its all-encompassing complexity.

“Whatever advancements we find in designing or modeling new classes of complexities in materials, or having better predictive models, there could be some ramifications in brain mechanics,” says Salahshoor. Recently, he has been interested in the brain’s response to ultrasonic stimulation and how anatomy directs and refocuses ultrasonic waves.

“My work has shown that when you subject a human skull to an ultrasound, there are shear waves that accompany the pressure waves generated by the ultrasound. The shear waves, due to the mismatch in the mechanical impedance of skull and soft matter, propagate downward and toward the inner ear, causing the subject to hear things,” said Salahshoor. “No matter where you put the ultrasound probe, you’ll get this bone conduction mechanism, because the skull is acting as a wave guide for shear waves.”

That is just one example of how computational modeling can shed light on experimental approaches and guide future attempts to mitigate or control unwanted effects. The same tools can capture the physical differences from patient to patient, allowing therapeutic approaches like ultrasound neuromodulation to be adjusted for efficacy.

Prior to his postdoctoral studies at Caltech, Salahshoor earned an M.S. in mathematics and a PhD in aerospace engineering from Georgia Tech, and with his interests equally divided between data-driven computations and mechanics—particularly biomechanics—joining Duke University and CEE was a logical next move.

“There’s a huge legacy at Duke of conducting research at the intersection of computational and mechanical sciences,” he says. “Having the opportunity to add to that legacy is an honor. He also notes the size of school facilitates open communications and opportunities for collaboration. “It’s a great place for interdisciplinary research, which mine is,” Salahshoor adds.

It’s also a great place for basketball fans like him.

Salahshoor begins his position on August 1, 2023.