Together with Canadian colleagues, a team from the Swiss Federal Laboratories for Materials Science and Technology (Empa), led by Gilberto Siqueira, have developed skin sensors made of nanocellulose and silver particles. With a thickness of just half a millimeter, high flexibility and biocompatibility, such sensors could one day be attached to the skin of patients in order to monitor blood values.

For the project, which Empa presented in its magazine “Empa Quarterly”, the researchers used nanocellulose as “ink” in a 3D printing process. Nanocellulose can be obtained from wood, but is also formed by certain types of bacteria, for example, which use it to build structures that serve as their habitat. Because of its mechanical properties and biocompatibility, this raw material is particularly well suited for various applications such as coatings, packaging, but also as a structure for three-dimensional cell cultures for medical applications.

Cellulose with silver

In order to render the sensor electrically conductive, the team of researchers led by Gilberto Siqueira added silver threads to the gelatinous nanocellulose prior to 3D printing. In a series of tests, they determined the appropriate mixing ratio to form a three-dimensional network of nanocellulose and silver threads.

Gilberto Siqueira compared the flexibility of the cellulose nanofibers with that of cooked spaghetti, “but with a diameter of barely 20 nanometers and only a few micrometers in length,” the magazine article states.

According to Empa, the sensors generated in this way can measure metabolic parameters, such as the concentration of calcium, potassium, and nitrogen-containing ammonium ions. The electrochemical skin sensor then sends the measured values to a computer for further data processing.

In a subsequent step, the researchers intend to further improve the sensor and, for example, replace the silver particles with other conductive carbon-based materials. This would make the sensors not only biocompatible, but also completely biodegradable.