They are not ready to replace Kevlar yet, but scientists are working on armored cotton t-shirts that are light and flexible but acquire the properties of boron carbide, the third hardest materials on the planet, according to researcher Xiaodong Li:

We were able to make large quantities of high-strength B4C nanowires using cotton T-shirts as both the template and carbon source. 'Cotton fibres have lots of small pores which can be used to trap the powder. During the process the cotton fibres change to carbon fibres - which react with the boron powder, producing B4C. The boron-carbide nanowires we synthesized keep the same strength and stiffness of the bulk boron carbide but have super-elasticity


The only side-effect is that the t-shirts turn to black. Does this mean that we will have bullet-proof t-shirts soon? Unfortunately, no. The technology is not there yet, although—according to other scientists—the approach seems promising. I'm sure the military would like to give their soldiers bullet-proof underpants. [RSC via PopSci]