A breathable tattoo electrode for bio-potential recording based on a Parylene C nanofilm is presented in this study. The proposed approach allows for the fabrication of micro-perforated epidermal submicrometer-thick electrodes that conjugate the unobtrusiveness of Parylene C nanofilms and the very important feature of breathability. The electrodes were fully validated for electrocardiography (ECG) measurements showing performance comparable to that of conventional disposable gelled Ag/AgCl electrodes, with no visible negative effect on the skin even many hours after their application. This result introduces interesting perspectives in the field of epidermal electronics, particularly in applications where critical on-body measurements are involved.

Interfacing ultrathin functional films for epidermal applications with external recording instruments or readout electronics still represents one of the biggest challenges in the field of tattoo electronics. With the aim of providing a convenient solution to this ever-present limitation, in this work we propose an innovative free-standing electrode made of a composite thin film based on the combination of the conductive polymer PEDOT:PSS and ferrimagnetic powder. The proposed epidermal electrode can be directly transferred onto the skin and is structured in two parts, namely a conformal conductive part with a thickness of 3 μm and a ferrimagnetic-conductive part that can be conveniently connected using magnetic connections. The films were characterized for ECG recordings, revealing a performance comparable to that of commercial pre-gelled electrodes in terms of cross-spectral coherence, signal-to-noise ratio, and baseline wandering. These new, conductive, magnetically interfaceable, and free-standing conformal films introduce a novel concept in the domain of tattoo electronics and can set the basis for the development of a future family of epidermal devices and electrodes.

In an increasingly interconnected world, where electronic devices permeate every aspect of our lives, wearable systems aimed at monitoring physiological signals are rapidly taking over the sport and fitness domain, as well as biomedical fields such as rehabilitation and prosthetics. With the intent of providing a novel approach to the field, in this paper we discuss the development of a wearable system for the acquisition of EEG signals based on a portable, low-power custom PCB specifically designed to be used in combination with non-conventional ultra-conformable and imperceptible Parylene-C tattoo electrodes. The proposed system has been tested in a standard rest-state experiment, and its performance in terms of discrimination of two different states has been compared to that of a commercial wearable device for EEG signal acquisition (i.e., the Muse headset), showing comparable results. This first preliminary validation demonstrates the possibility of conveniently employing ultra-conformable tattoo-electrodes integrated portable systems for the unobtrusive acquisition of brain activity.

interesting features and apart from few examples, the full potential of OFETs has not been deployed yet in mass real-life applications. One of the fields that could greatly benefit from flexible and low-cost organic transistors, and therefore offer a first real application scenario, is the Internet of Things (IoTs), where cost-effective electronic tags would enable the link to smart objects at viable costs. [2] Yet, highly performing devices are required to intercommunicate and exchange continuous information in real time at high frequencies, i.e., in the high frequency to the ultrahigh frequency bands, from MHz to GHz. Such frequency range is still largely prohibitive for organic OFETs, especially when scalable, large-area processes must be adopted. In fact, up to now, the development of OFETs is mostly limited to those fields where a fast response is not strictly necessary, such as neuromorphic engineering, and sensing and biosensing applications. [3][4][5][6] Another issue with the adoption of OFETs regards applications where high currents are required, for example, for displays driving circuitry. In fact, due to their relatively low charge mobility, large-width (W) organic transistors are usually necessary, and this contributes to the increase of the area required to host simple electronic functions.A common strategy to enlarge the transistor form factor consists in reducing the channel length (L), a process that has been efficiently employed by standard MOSFET technologies along the years, leading to a continuous miniaturization of the siliconbased MOSFET area and, as a consequence, to the increase of the density of devices per unit area, as well as the maximum operating frequencies. Unfortunately, scaling the channel length usually requires sophisticated fabrication techniques that can negatively impact on one of the main advantages of organic semiconductors-based technologies, i.e., the possibility of fabricating flexible circuits at low costs and high-throughputs. This aspect has de facto limited along the years the development of all those applications in which a high-density of organic devices is needed, such as high-density sensors arrays and complex circuits. Nevertheless, many strategies have been proposed so far for the fabrication of short-channel organic transistors, such as those based on the use of photolithographic approaches, including nanoimprint lithography, stencil lithography, and electron beam lithography. In particular, nanoimprint lithography allows to obtain channel lengths down to few tens of nm, [7,8] In this paper, the development of a simple and reproducible approach for the fabrication of n-type organic field-effect transistors with a 350 nm-long channel on flexible substrates is reported. The critical feature of the device, the channel length, is obtained using a self-alignment process that exploits the vertical step of a plasma-etched thin Parylene C layer, according to the so-called step-edge architecture. The fabricated devices can operate in continuous mode and show an averag...

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