That gooey substance that clings to an eggshell after it’s been cracked—called an eggshell membrane—may be too valuable to just toss in the trash. Instead, it can be used for a variety of industrial and medical applications, according to a study published in the September issue of Acta Biomaterialia. Under the lens of a scanning electron microscope, the membrane’s network of more than 62 types of proteins is visible (as in photo above). These proteins can be used to precipitate gold from a solution, craft aluminum nanowires to form semiconductors, or soak up dyes or heavy metals from contaminated water, according to researchers. By attaching compounds to the eggshell membrane, researchers have created biosensors that can detect glucose, dopamine, or urea concentrations in human blood. The membranes can also be ground into a powder that a Missouri company markets to treat joint disorders. Eggshell membranes are a hip research topic, too: Since 2011, more than 30 papers have been published each year. The sticky substance does have a few drawbacks. Membranes are tough to separate from the shell, and they are thin—only about the width of a human hair—so hundreds or thousands of eggs are needed for most applications.