Introduction

Wearable electrochemical sweat sensor consisting of a composite membrane with poly (vinylidene fluoride) (PVDF) and graphene. The membrane is self-standing and incorporates three different components: a first consisting of PVDF and graphene, a second of PVDF as an electrical insulation,  and a third composite made of PVDF, graphene and possibly metal elements. When in contact with drops of sweat and/or other electrolytic solutions, the membrane electrochemically generates a voltage signal proportional to the salt content of the solution. It is therefore possible to detect the presence of sweat and to estimate the concentration of the ions present there.

Technical features

The sensor consists of a PVDF composite polymer thin membrane, containing graphene and possibly metal. The membrane is self-standing, light, flexible and incorporates three sectors: the first (S1) in PVDF and graphene; the second (S2) in PVDF; the third (S3) in PVDF and graphene, possibly with metallic elements. Sector S1, if placed in contact with sweat or other saline solutions, is the site of reduction reactions while sector S3 is the site of oxidation reactions. Consequently, when both S1 and S3 are in contact with even small quantities of sweat there is the passage of electrons and therefore a voltage signal whose intensity depends on the concentration of ions in the sweat (or other saline solution). The production process of the membrane is crucial. The TRL is 3, which is a working prototype and tested in the laboratory in significant environments. The activation of an ethics committee is envisaged to proceed with tests on people. The first 1 cm × 2.1 cm sample was tested as a sweat sensor; the second sample, 5 cm × 9 cm in size, was immersed in saline solution and tested as an electrolytic cell.

Possible Applications

• Medical, health, welfare sector;
• Fitness sector;
• Continuous minimally invasive monitoring;
• Real-time sweat for PPE.

Advantages

• Economical: does not require the use of expensive reference electrodes;
• Flexible, wearable, washable, reusable adaptable;
• It does not require an external power supply because it is a device that is self-powered by electrochemical means in the presence of sweat;
• Biocompatible and with low bacterial proliferation.