In this review, we aim to introduce the reader to the technique of electrical impedance spectroscopy (EIS) with a focus on its biological, biomaterials, and medical applications. We explain the theoretical and experimental aspects of the EIS with the details essential for biological studies, i.e., interaction of metal electrodes with biological matter and liquids, strategies of measurement rate increasing, noise reduction in bio-EIS experiments, etc. We also give various examples of successful bio-EIS practical implementations in science and technology, from whole-body health monitoring and sensors for vision prosthetic care to single living cell examination platforms, virus disease research, biomolecules detection, and implementation of novel biomaterials. The present review can be used as a bio-EIS tutorial for students as well as a handbook for scientists and engineers because of the extensive references covering the contemporary research papers in the field.

We investigate the formation of a new class of density-phase defects in a resonantly driven 2D quantum fluid of light. The system bistability allows the formation of low density regions containing density-phase singularities confined between high density regions. We show that in 1D channels, an odd (1-3) or even (2-4) number of dark solitons form parallel to the channel axis in order to accommodate the phase constraint induced by the pumps in the barriers. These soliton molecules are typically unstable and evolve toward stationary symmetric or anti-symmetric arrays of vortex streets straightforwardly observable in cw experiments. The flexibility of this photonic platform allows implementing more complicated potentials such as maze-like channels, with the vortex streets connecting the entrances and thus solving the maze.

The time domain technique for impedance spectroscopy consists in computing excitation voltage and current response Fourier images by fast or discrete Fourier transform and calculating their relation. Here we propose an alternative method for excitation voltage and current response processing for deriving system impedance spectrum based on fast and flexible adaptive filtering method. We show the equivalence between the problem of adaptive filter learning and deriving system impedance spectrum. To be specific we express the impedance via the adaptive filter weight coefficients. The noise canceling property of adaptive filtering has been also justified. Using the RLC circuit as a model system we experimentally show that adaptive filtering yields correct admittance spectra and elements ratings in the high noise conditions when Fourier transform technique fails. Providing the additional sensitivity for impedance spectroscopy, adaptive filtering can be applied to otherwise impossible to interpret time-domain impedance data. The advantages of adaptive filtering were justified with the practical living-cell impedance measurements.

The dark solitons observed in a large variety of nonlinear media are unstable against the modulational (snake) instabilities and can break in vortex streets. This behavior has been investigated in nonlinear optical crystals and ultra-cold atomic gases. However, a deep characterization of this phenomenon is still missing. In a resonantly pumped two-dimensional polariton superfluid, we use an all-optical imprinting technique together with the bistability of the polariton system to create dark solitons in confined channels. Due to the snake instabilities, the solitons are unstable and break into arrays of vortex streets whose dynamical evolution is frozen by the pump-induced confining potential, allowing their direct observation in our system. A deep quantitative study shows that the vortex street period is proportional to the quantum fluid healing length, in agreement with the theoretical predictions. Finally, the full control achieved on the soliton patterns is exploited to give proof of principle of an efficient, ultra-fast, analog, all-optical maze solving machine in this photonic platform.

In this paper, we propose a fast and simple approach for the fabrication of the electrocatalytically active ruthenium-containing microstructures using a laser-induced metal deposition technique. The results of scanning electron microscopy and electrical impedance spectroscopy (EIS) demonstrate that the fabricated ruthenium-based microelectrode had a highly developed surface composed of 10 μm pores and 10 nm zigzag cracks. The fabricated material exhibited excellent electrochemical properties toward non-enzymatic dopamine sensing, including high sensitivity (858.5 and 509.1 μA mM−1 cm−2), a low detection limit (0.13 and 0.15 μM), as well as good selectivity and stability.

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