The genius of hot and sour soup is that two very different culinary ingredients—chili oil and vinegar—unite to give a distinct flavor, piquant and tangy. Engineers who devise recipes for composite materials apply a similar principle. They might combine a strong material resistant to breakage with a stiff material resistant to deformation and fabricate a composite that is both strong and stiff. But just as hot and sour soup prepared with an ounce of chili–vinegar mixture is not as spicy or sour as it would be were it prepared with an ounce of either undiluted ingredient, one might expect that the engineer's composite is not as strong as its strongest constituent nor as stiff as its stiffest. A rigorous theorem confirms that intuition. 1
But in 2001, Roderic Lakes of the University of Wisconsin–Madison and colleagues created a material with a stiffness greater than theoretically allowed. They did it by...
