Live Printing

3D printer taught to print elastic microchips on the skin

Grigory Kopiev, N+1

Scientists from the University of Minnesota have developed a 3D printing technology for flexible pressure sensors on the skin. This technology will help in the development of wearable electronics. The study by Guo et al. 3D Printed Stretchable Tactile Sensors is published in the journal Advanced Materials.

The development of wearable electronics and 3D printing are among the main technological trends of recent years. Engineers from The University of Minnesota decided to combine them and create skin electronic sensors using a 3D printer.

Since the sensors must be biologically compatible, the researchers had to create printing materials that would meet several parameters at once: flexibility, electrical conductivity, the ability to print without using harsh conditions in the process, such as high sintering temperature or intense radiation. 

The ideal candidate for the role of such a material, according to scientists, should be a "solution" of submicrometer silver particles in a silicone elastic polymer that hardens at room temperature. The researchers selected such a concentration of silver (68 mass percent) in the medium that under normal conditions the material conducts current very weakly, but dramatically – hundreds of times – increases the conductivity under pressure. This happens due to the fact that in the normal state, the "grid" of silver particles in the volume of the elastomer is not fully formed, but even with a slight compression, the particles are arranged more tightly, which allows the current to flow through the material. This effect has become the basis of the sensors being developed.

To demonstrate the effectiveness of the approach, scientists modified a commercially available 3D printer. The device had four independent nozzles for four different compositions: pure silicone elastomer, electrode material (75% by weight of silver in the elastomer), sensor material (68% by weight of silver in the elastomer) and a water-washed auxiliary polymer (poloxamer), which played the role of support during the solidification of the remaining layers. 

The creation of the sensor consisted of several stages. First, a silicone substrate was created, on which a silicone electrode was applied. A pressure-sensitive spiral sensor was printed in the center of the electrode. An insulating layer of silicone and a supporting polymer were applied around it. An electrode was also printed on top of the sensor. After solidification of the materials, the supporting layer of the poloxamer was dissolved in water.

Stages of sensor creation (from an article in Advanced Materials)

The resulting sensors were attached to the fingers and measured the change in conductivity under different conditions: finger pressing, finger flexion in the joint. Scientists have found that the change in conductivity depends on the type of load. Thus, the sensor can not only detect movement, but also determine its type. Also, by attaching the sensor to the artery, the scientists were able to accurately determine the pulse of the subject.

Using a model of a human hand, scientists have demonstrated that potentially using their technology, it is possible to print sensors directly on human skin within a few minutes.

Scientists believe that their development is potentially ready for mass implementation. In the future, they plan to conduct tests on real leather, as well as develop a semiconductor composition for printing.

Portal "Eternal youth" http://vechnayamolodost.ru  15.05.2017