Light and small wearable electronic devices are useful because they can monitor a variety of biometric data. However, recently, a method of monitoring the human body by printing electronic circuits on human skin is being sought one step further. Research teams such as Pennsylvania State University have announced that they have developed a technology to monitor biometric data by printing electronic circuits on the skin at room temperature.
The research team has focused on heating and sintering solid powder assemblies at a temperature lower than the melting point as a method of manufacturing a highly flexible electronic circuit applicable to biometric data monitoring. Although metal nanoparticles can be sintered to directly print electronic circuits on the surface of paper or cloth, there is a problem that the temperature required for sintering is too high for human skin.
The research team of Professor Huanyu Cheng of Pennsylvania State University was also developing a flexible printed electronic circuit that can be used as a wearable sensor once, but it was not possible to realize a technology that directly prints on the skin due to a problem in the process of bonding metal nanoparticles. It required a high temperature of 300 degrees to sinter the silver nanoparticles used in electronic circuits.
Of course, the team looked for a way to allow the skin to withstand such high temperatures and to sinter at lower temperatures. In addition, a material layer called sintering aid was created under the electronic circuit, and a method was developed to reduce the amount of energy required for bonding silver nanoparticles in the printed electronic circuit.
The sintering aid developed by the research team consists of a biodegradable polymer paste, which is the main component of a peelable face mask, and calcium carbonate that makes up eggs. In the sintering aid layer, silver nanoparticles accumulate, reducing the amount of energy required for sintering. He explained that after changing the composition of the sintering aid layer and the printing material, he learned that silver nanoparticles can be sintered at room temperature.
In addition, it is said that instead of suddenly printing electronic circuits on uneven skin, it printed electronic circuits on a smooth sintering aid layer to improve electromechanical performance when electronic circuits are bent or broken. The sintering aid and the electronic circuit layer can be printed on clothing and paper in addition to human skin.
The research team actually conducted an experiment in which an electronic circuit made of wooden stamps and silver nanoparticles and a sintering aid layer were placed and printed on the back of a human hand. It is said to have succeeded in sintering the electronic circuits of silver nanoparticles at room temperature by evaporating the solvent with a cold and hot hair dryer, covering the electronic circuit and the sintering aid on the skin.
In fact, the electronic circuit printed on the skin is said to have been able to measure body temperature, skin moisture, blood oxygen, heart rate, respiration rate, blood pressure, and electrocardiogram. The research team explained that the data accuracy measured by the electronic circuit printed directly on the skin was the same as or better than the wearable sensor installed on the skin.
The electronic circuit printed on the skin can be wetted with water, but it can be easily removed with hot water and can be recycled once separated. It can be used for the elderly or babies as it does not damage the skin when removed.
The team can also use a similar technique to print electronic circuits on paper and create a simple board with a wireless communication chip added to it. This simple board can be attached to the inside of the sleeve to collect data from electronic circuit sensors printed on the skin and send it to other devices.
The research team said that this approach replaces hundreds of degrees of temperature using a new layer of sintering aid, and can sinter metal nanoparticles at low or room temperature. It is excellent that it can be combined with other expansion modules to replace wearable electronics that monitor health. Related information can be found here .