An international research team, including engineers at Penn State University, has developed a process to print metal wearable sensors directly on the skin without heating. The new technology helps wearable sensors develop from simple electrodes to flexible devices that can provide users with biometric measurement and enough comfort. < / P > < p > according to the first author of the study, Ling Zhang from Harbin Institute of technology, China, the team has created a simple and universally applicable manufacturing technology using the new sintering auxiliary layer, which can directly print the sensors on the body. < / P > < p > the team has previously developed flexible printed circuit boards for wearable sensors. However, it is not possible to print directly on the skin using the previous technology, because the metal components in the sensor need to be bonded, which is called sintering. The process usually takes about 572 degrees Fahrenheit to bond the silver nanoparticles in the sensor together. < / P > < p > obviously, the skin can’t withstand such a high temperature. The researchers added a kind of nano particle, which can make the silver particles sintered at a lower temperature of about 212 degrees Fahrenheit. The temperature of this method is low enough to print sensors on cloth and paper, but it is still too high for human skin. < / P > < p > after changing the formula of the auxiliary layer and the printing material, the researchers were able to sinter at room temperature. The room temperature auxiliary layer is composed of polyvinyl alcohol slurry and calcium carbonate in eggshell. < / P > < p > the new layer reduces the surface roughness and enables the ultra-thin metal pattern layer to bend and fold while maintaining its conductivity. After printing, the researchers used a hair dryer to cool down the water used as a solvent in the ink. The results are very encouraging. The sensor can continuously capture temperature, humidity, blood oxygen level and cardiac performance signals. Sensors can also be connected in the network, with wireless transmission function, printed sensors are easy to disassemble even in the warm water shower. More Samsung devices can now run Android applications on PC through your phone