Bio-potential noise of dry printed electrodes: physiology versus the skin-electrode impedance.

Objective. To explore noise characteristics and the effect physiological activity has on the link between impedance and noise.Approach. Dry-printed electrodes are emerging as a new and exciting technology for skin electro-physiology. Such electrode arrays offer many advantages including user convenience, quick placement, and high resolution. Here we analyze extensive electro-physiological data recorded from the arm and the face to study and quantify the noise of dry electrodes, and to characterize the link between noise and impedance. In particular, we studied the effect of the physiological state of the subject (e.g. rapid eye movement sleep) on noise.Main results. We show that baseline noise values extracted from dry electrodes in the arm are in agreement with the Nyquist equation. In the face, on the other hand, the measured noise values were higher than the values predicted by the Nyquist equation. In addition, we studied how different electrode properties affect performances, including electrode size, shape, and material properties.Significance. Altogether, the results presented here provide a basis for understanding dry electrode performances and substantiate their great potential in electro-physiological investigations.

Gas-assisted blade-coating of organic semiconductors: molecular assembly, device fabrication and complex thin-film structuring.

The competitive performance of optoelectronic devices based on advanced organic semiconductors increasingly calls for suitably scalable processing schemes to capitalise on their application potential. With performance benchmarks typically established by spin-coating fabrication, doctor-blade deposition represents a widely available roll-to-roll-compatible means for the preparation of large-area samples and establishing the device upscaling potential. However, the inherently slower film formation kinetics often result in unfavourable active layer microstructures, requiring empirical and material-inefficient optimisation of solutions to reach the performance of spin-coated devices. Here we present a versatile approach to achieving performance parity for spin- and blade-coated devices using in situ gas-assisted drying enabled by a modular 3D-printed attachment. This is illustrated for organic photodetectors (OPDs) featuring bulk heterojunction active layers comprising blends of P3HT and PM6 polymer donors with the nonfullerene acceptor ITIC. Compared to conventionally blade-coated devices, mild drying gas pressures of 0.5-2 bar yield up to a 10-fold enhancement of specific detectivity by maximising external quantum efficiency and suppressing dark-current. Furthermore, controlling gas flux distribution enables one-step fabrication of 1D chain conformation and 2D chain orientation patterns in, respectively, PFO and P3HT:N2200 blend films, opening the possibility for high-throughput fabrication of devices with complex structured active layers.