In what can revolutionalise analysis of sub-surface tissues and enhance medical diagnosis without invasive procedures, scientists at Stanford University in the United States have found a food-dye that makes skin temporarily invisible. The scientists have tested the dye in animal experiments and have published the study in Science magazine.
The dye can come in handy in making diagnosis, locating veins to draw blood or even making procedure to remove tattoos simpler.
So how does the 'invisibility dye' work?
Scattering of light is why we deem certain substances to be opaque. To put it simply, scattering of light is when interaction between particles of a medium and the light causes that light to get deflected from its straight path.
When we consider skin, the various substances like fats, proteins and other materials are so tightly packed, refractive indices of all these cause light to scatter in a way that it makes the skin opaque.
Stanford scientists have found that when a dye named tartrazine is dissolved in water and made to absorb in tissues, it interacts with the refractive indices in a way that it renders the skin transparent.
The scientists applied the dye to a slice of chicken breast. They found that refractive index of the fluid in the muscle cells rose to match that of muscle proteins. This rendered the slice invisible.
The dye was then tested on live mice. It was found that application of the dyes on their scalp revealed maze of blood vessels underneath.
The disappearing effect was not permanent. When the dye was rinsed off, the skin again assumed its opaque nature.
