Print These Electronic Circuits Directly Onto Skin

An anonymous reader quotes a report from IEEE Spectrum: New circuits can get printed directly on human skin to help monitor vital signs, a new study finds. In the new study, researchers developed a way to sinter nanoparticles of silver at room temperature. The key behind this advance is a so-called a sintering aid layer, consisting of a biodegradable polymer paste and additives such as titanium dioxide or calcium carbonate. Positive electrical charges in the sintering aid layer neutralized the negative electrical charges the silver nanoparticles could accumulate from other compounds in their ink. This meant it took less energy for the silver nanoparticles printed on top of the sintering aid layer to come together, says study senior author Huanyu Cheng, a mechanical engineer at Pennsylvania State University. The sintering aid layer also created a smooth base for circuits printed on top of it. This in turn improved the performance of these circuits in the face of bending, folding, twisting and wrinkling. In experiments, the scientists placed the silver nanoparticle circuit designs and the sintering aid layer onto a wooden stamp, which they pressed onto the back of a human hand. They next used a hair dryer set to cool to evaporate the solvent in the ink. A hot shower could easily remove these circuits without damaging the underlying skin. After the circuits sintered, they could help the researchers measure body temperature, skin moisture, blood oxygen, heart rate, respiration rate, blood pressure and bodily electrical signals such as electrocardiogram (ECG or EKG) readings. The data from these sensors were comparable to or better than those measured using conventional commercial sensors that were simply stuck onto the skin, Cheng says. The findings have been published in the journal Applied Materials & Interfaces.