On the Breathability of Epidermal Polymeric-Printed Tattoo Electrodes

Tattoo sensors offer many of the features of next-generation epidermal devices. They are ultrathin and conformable electrodes that have been shown to record high-quality biosignals from the skin. Moreover, they can be fabricated through large-area processing such as printing. Here, we report on printed poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) tattoo electrodes breathability. Epidermal devices require a breathable interface to ensure a physiological transepidermal water loss for reduced skin inflammation and discomfort of the user. In this work, we deeply examine the polymeric tattoo sensor's permeability properties with complementary experiments. By assessing the water permeance, the water-vapor transmission rate, and the impedance spectroscopy of polymeric tattoo electrodes, we show that they are intrinsically breathable, establishing a dry interface with the skin. The stability of such a dry interface is shown through the recording of muscle activity during sport when the sweat rate is much higher. While breathability is often hindered in conventional epidermal sensors, in PEDOT:PSS tattoo electrodes, it lies at the core of a stable sensor performance.