UCSD Jacobs School of Engineering University of California San Diego
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Rethinking Multi-Functional Materials

MAE professor Sia Nemat-Nasser is developing a multicomponent braid consisting of fibers for mechanical reinforcement, metallic wires for power and communications, and polymer matrix material impregnated around periodically spaced sensors and other electronics.

Siavouche "Sia" Nemat-Nasser's team at the Center of Excellence for Advanced Materials is experimenting with creating a new generation of multi-functional materials. They are working on integrating sensors the size of a grain of sand into fiber-reinforced polymers which are then braided with specialized fibers that have built-in functions.

"It's almost impossible to predict how such a multifunctional material would be used, but you could weave it into tents for soldiers, and the tent itself could harvest solar energy and function as a battery," says Nemat-Nasser, author of Plasticity: A Treatise on Finite Deformation of Heterogeneous Inelastic Materials (Cambridge University Press, 2004).

Nemat-Nasser says a network of multifunctional fabric could also be equipped with stress and strain sensors, which could communicate with "nodes" similar to the housefly's recently elucidated motion-detection circuitry. The fly uses information received from what could be described as passive sensors to help it reflexively add enough torque to maintain its horizontal motion: "Flies can maneuver and change paths much faster than birds or any flying machine, and if you consider a fly's weight relative to its performance, they're truly remarkable."

Rather than continually sending data to a central repository, only readings that matched pre-determined profiles would be transmitted.

"You could also braid in very thin, properly designed copper wires," he says, "and you could use the wire to control the tent's dielectric properties and even use it as heating or cooling elements and as the backbone of the communications network. We are experimenting with those ideas now."

Nemat-Nasser envisions materials that can not only act as sensors and change their properties on cue, but also generate their own power and even make decisions. He delivered a plenary talk Dec. 2004 at the Second World Congress on Biomimetics, Artificial Muscles and Nano-Bio which summarized his group's efforts to make a robotic muscle that flexes due to an ionic impulse, similar to muscle contraction.