Ferrofluids exhibit a unique combination of liquid properties and strong magnetic response, which leads to a rich variety of interesting functional properties. Here, the magnetic‐field‐induced splitting of ferrofluid droplets immersed in an immiscible liquid is presented, and related fascinating dynamics and applications are discussed. A magnetic field created by a permanent magnet induces instability on a mother droplet, which divides into two daughter droplets in less than 0.1 s. During the splitting process, the droplet undergoes a Plateau–Rayleigh‐like instability, which is investigated using high‐speed imaging. The dynamics of the resulting satellite droplet formation is shown to depend on the roughness of the supporting surface. Further increasing the field results in additional splitting events and self‐assembly of microdroplet populations, which can be magnetically actuated. The effects of magnetization and interfacial tension are systematically investigated by varying magnetic nanoparticles and surfactant concentrations, and a variety of outcomes from labyrinthine patterns to discrete droplets are observed. As the splitting process depends on interfacial tension, the droplet splitting can be used as a measure for interfacial tension as low as 0.1 mN m −1 . Finally, a population‐based digital microfluidics concept based on the self‐assembled microdroplets is presented.

The perspective of downscaling organic electrochemical transistors (OECTs) in the nanorange is approached by depositing poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on electrodes with a nanogap designed and fabricated by electromigration induced break junction (EIBJ) technique. The electrical response of the fabricated devices is obtained by acquiring transfer characteristics in order to clarify the specific main characteristics of OECTs with sub‐micrometer‐sized active channels (nanogap‐OECTs). On the basis of their electrical response to different scan times, the nanogap‐OECT shows a maximum transconductance unaffected upon changing scan times in the time window from 1 s to 100 µs, meaning that fast varying signals can be easily acquired with unchanged amplifying performance. Hence, the scaling down of the channel size to the nanometer scale leads to a geometrical paradigm that minimizes effects on device response due to the cationic diffusion into the polymeric channel. A comprehensive study of these features is carried out by an electrochemical impedance spectroscopy (EIS) study, complemented by a quantitative analysis made by equivalent circuits. The propagation of a redox front into the polymer bulk due to ionic diffusion also known as the “intercalation pseudocapacitance” is identified as a limiting factor for the transduction dynamics.

We report on the preparation and stereolithographic 3D printing of a resin based on the composite between a poly(ethylene glycol) diacrylate (PEGDA) host matrix and a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) filler, and the related cumulative volatile organic compounds’ (VOCs) adsorbent properties. The control of all the steps for resin preparation and printing through morphological (SEM), structural (Raman spectroscopy) and functional (I/V measurements) characterizations allowed us to obtain conductive 3D objects of complex and reproducible geometry. These systems can interact with chemical vapors in the long term by providing a consistent and detectable variation of their structural and conductive characteristics. The materials and the manufacture protocol here reported thus propose an innovative and versatile technology for VOCs monitoring systems based on cumulative adsorption effects.

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