December 11, 2023

Imagine if there were cheap 3D printed sensors that could change color to show us if something was getting too hot or under too much pressure. Well, it’s coming soon — and they biodegrade once thrown away.

The sensors were developed by scientists at the Empa Institute in Switzerland led by Dr. Gustav Nyström. At the heart of the technology is a substance called hydroxypropyl cellulose (HPC), which has been used as a carrier for active ingredients such as drugs and foods.

HPC forms liquid crystals when mixed with water.thanks to the microstructure of These crystals, which only reflect certain wavelengths of the visible spectrum, cause them to appear as The colors that the human eye sees. The same principle is naturally employed in brightly colored butterfly wings and the like.

Simply changing the temperature of the liquid crystal can change the “structural color” of the liquid crystal. Taking this fact into consideration, the Empa scientists added small amounts of carbon nanotubes to the HPC/water mixture, increasing its conductivity. As a result, when a voltage is applied to the material, its temperature increases and the crystals change color accordingly.

Two images of color-changing digital display created by scientists
Two images of color-changing digital display created by scientists


After “blowing up” the biodegradable mixture by adding cellulose nanofibers, the material could be 3D printed without changing its structural color or conductivity. So far, scientists have used the technology to produce a seven-segment digital display, as well as a strain sensor that changes color in response to pressure. piezoelectric Electrical current generated by mechanical deformation.

“Our lab has developed different cellulose-based disposable electronic components, such as batteries and sensors,” said study co-author Xavier Aeby. “This is the first time we have been able to develop cellulose-based displays .”

source: but