Memristive measurements on human skin
Unlike in linear electrical measurements, the applied electrical voltage or current forces ions to move and thus changes the underlying electrical properties of the measured object. Resulting current voltage characteristics exhibit pinched hysteresis loops, the fingerprint of a memristor (memory resistor), which is a passive electrical element that correlates voltage and current via a state-dependent Ohm’s law. Its ability to conduct current depends on the amount of charge, or flux that went through it. The existence of the memristor was predicted by Leon Chua from the University of Berkeley in 1971 and confirmed by Hewlett Packard in 2008. A “memristive measurement” is a type of electrical measurement that studies the properties of an underlying memristor and that is always non-linear since the current and the voltage waveforms are different from each other. As recently shown, human sweat ducts and the stratum corneum are both memristors and information can be stored within. Utilizing the non-linear (memristive) properties of human skin leads to a new class of measurements with potential use in sensor applications.