Effect of metabolite and temperature on artificial human sweat characteristics over a very wide frequency range (400 MHz–10.4 GHz) for wireless hydration diagnostic sensors

Sweat is an important biofluid that is excreted by the human body. It contains physiological biomarkers that provide vital information on the general health condition of the body. As a result, analysis of electrolytes in this biofluid is gaining traction in the development of non-invasive sweat diagnostics to determine level of dehydration, cystic fibrosis and illicit drugs. This paper presents a wireless measurement modality of permittivity properties of sweat of different metabolite concentration levels exemplifying the full spectrum of human sweat. The artificial sweat used in the study is an analogue of actual human sweat. It is synthesized from a composite mixture of metabolites and minerals including sodium chloride, potassium chloride, Urea and lactic acid. The effect of ambient temperature on the permittivity measurements of the various sweat solutions are studied across a frequency range of 400 MHz to 10.4 GHz. This information is important in the development of wireless radio frequency (RF) non-invasive biosensors.