When doctors need to look inside the human body, they usually use ultrasound, magnetic resonance imaging (MRI), X-rays and other technologies. However, all of them provide a rather limited view. To solve this problem, Stanford University employees decided to go the opposite way and make human skin transparent. It turned out that ordinary food coloring, which may even be present in the products in your kitchen, can help with this.
Scientists have developed a technology that makes skin transparent. Photo source: livescience.com
How to make skin transparent
The tissues of the human body contain many different substances – proteins, fats, liquids, etc. Each substance has its own ability to refract, reflect and scatter light. When light hits the boundary between two materials with different refractive indices, it changes direction, is reflected and scattered in different directions. For this reason, we cannot see through the human body.
It follows that in order to make human skin transparent, the refractive indices of the substances in it must be equalized. This is exactly what the researchers decided to do. To do this, they used a food coloring additive known as tartrazine. This yellow-orange dye is often found in candies and other confectionery products, as well as in drinks, wasabi seasoning, medicines and cosmetics.
Demonstration of the change in transparency of a chicken breast after applying a solution with a dye. Photo source: flscience.com
The authors of the work dissolved the dye in water and applied the resulting solution to a piece of chicken breast. As expected, this allowed the refractive indices of the substances in the tissue to be equalized, as a result of which it temporarily became translucent. The diagram above clearly shows how much it changed.
The same result was achieved when the researchers applied the dye solution to the skin of mice. The authors of the work report this in the publication Science.
How effective is the skin transparency composition?
After the solution was absorbed into the skin of the mice, the scientists were able to examine the blood vessels that run along the surface of the skull with a resolution of 0.001 millimeters. When the researchers applied the same solution to the abdomen of the mice, they were able to examine the internal organs – the liver, small intestine, bladder, etc. They were even able to see how the muscles inside the intestine contract.
To stop the skin from being transparent, it is enough to simply wash it with water and remove the food coloring from the surface. The part of the coloring that has already penetrated the skin is excreted from the body with the urine of mice within two days, without causing any harm to health.
After applying the dye solution to the heads of mice, scientists were able to see their veins. Photo source: livescience.com
Why does the dye make the skin transparent
According to the researchers, the transparency of the skin appears within a few minutes after the molecule penetrates the skin. The time depends on how quickly the dye molecules penetrate the tissue. But why does food coloring make fabrics transparent?
As the authors of the work explain, the dye contains a molecule that absorbs most of the light, especially the blue and violet parts of the spectrum. Human skin is a scattering medium. Separately, both the dye and the skin block most of the light, but when the molecule combines with the skin, transparency is achieved.
The secret is that tartrazine dissolved in water changes its refractive index, as a result of which it coincides with the refractive index of lipid molecules in the body's tissues. As the food coloring solution is absorbed into the skin, the scattering of light inside the tissue decreases, just like fog dissipates in the early morning.
How safe is the dye solution? According to the authors of the study, it caused minimal inflammation, and in the short term. Most likely, the dye does not have a long-term negative effect on the animals. The researchers did not find any changes in body weight or blood test results in the mice.
This technology has not yet been tested on humans. It is too early to say whether the dye will make human skin transparent in the same way. It should be taken into account that human skin is four times thicker than that of mice. This complicates the absorption of the dye molecule into the deep layers of the skin. But if the technology does prove effective or can be improved, and at the same time scientists prove its safety for health, medicine will receive a useful tool that can be used for a variety of purposes.
Be sure to visit our Zen and Telegram channels, where you will find the most interesting news from the world of science and the latest discoveries!
For example, the solution can make veins more visible for blood sampling, because not all people have “noble” skin with clearly visible veins. This technology can also simplify tattoo removal with a laser, and will help detect cancer in the early stages, which will increase the effectiveness of treatment. In addition, this technology does not require large financial costs, unlike many other modern diagnostic methods, which are often inaccessible to the general public due to their high cost.