Kamal Asadi

Understanding how microbial populations generate and modulate electrical signals remains a major technical challenge because extracellular ionic processes are inherently weak, spatially distributed and stochastic. Here, we introduce a mesoporous ultra‐low‐impedance PEDOT:PSS electrode that exploits volumetric ionic‐electronic coupling to probe stochastic electrochemical dynamics in axenic populations of the marine model diatom Phaeodactylum tricornutum . The three‐dimensional porous architecture provides a large electrochemically accessible surface area with high capacitance and low impedance, enabling sensitive detection of non‐equilibrium current fluctuations under applied bias. Applied bias systematically amplifies stochastic electrical fluctuations, while living diatoms significantly modify their amplitude and temporal statistics. Noise analysis reveals enhanced low‐frequency fluctuations, increased power‐law exponents and higher transient‐event rates, indicating biologically driven perturbations of the local electrochemical environment. Pharmacological inhibition with tetraethylammonium suppresses spontaneous electrical activity, providing independent functional evidence that membrane‐associated potassium‐dependent processes contribute to the measured signals. Increasing diatom cell density further produces progressively larger spectral exponents and distinct changes in stochastic‐event dynamics, demonstrating that these electrical signatures encode microbial population density. These findings establish stochastic electrochemical noise as a sensitive, label‐free probe of microbial bioelectrochemical activity and a bioelectronic strategy for monitoring living microbial systems through their intrinsic non‐equilibrium electrical fluctuations.

Modern power electronics and electrified transport systems increasingly demand polymer dielectric materials that operate reliably at high temperatures (high-T) exceeding 100 °C. The development of polymer dielectrics that retain their capacitive performance under thermal stress has been a long-standing challenge. Here, we describe a scalable route to high-T polymer dielectric nanocomposite based on polymethylmethacrylate (PMMA) and metallic iron nanoparticles (FeNPs), wherein the PMMA chains are grafted from the surface of the FeNPs via atom transfer radical polymerisation. This strategy ensures uniform particle dispersion even at high filler loadings and addresses the interfacial compatibility and processing complexity. The nanocomposite, particularly at 3 v/v% FeNP content, retains its capacitive efficiency at temperatures up to 200 °C and electric fields of 200 MV/m while the capacitive performance of neat PMMA deteriorates significantly beyond 70 °C. Using broad band dielectric spectroscopy, we shows that the improved high-T performance arises from significantly restricted molecular mobility of the PMMA chains. These findings pave the way for practical utilization of commodity polymeric materials in high-temperature electronics and capacitive energy storage applications.

Graphene oxide is an oxidized form of graphene and an electrical insulator. Graphene oxide can be used in the fabrication of electronic devices with variable resistance and capacitance (memristor and capacitive memory) and micro-supercapacitors in a metal/insulator/metal structure, where the state of the device changes based on the growth of graphene dendrites due to the reduction of the graphene oxide layer in the presence of moisture and applied electric field. The dendrites growth process is an irreversible electrochemical process that depends on many parameters such as the applied electric field and the environmental humidity. By controlling its reduction, suitable and stable devices can be fabricated as ionic devices like supercapacitors. In this research, potassium permanganate, which is an oxidizing agent, was used to control the rate of the graphene oxide reduction process. Depending on the amount of potassium permanganate and the amount of the applied electric field in the environmental conditions, three different behaviors are observed in the voltammetric responseof the samples. Such behaviors can be used in the fabrication of memristors, ionic devices (devices in which the ionic process is dominant), and micro-supercapacitors. In this research, the obtained results are discussed and the performance of the devices is studied.

It has been theoretically predicted that remanent polarization in odd nylons increases in a linear fashion with decreasing the molecular size of the amide unit, and can reach values comparable to those of inorganic ferroelectrics for lower order odd-nylons. However, such large remanent polarizations have never been experimentally measured due to challenges in processing low order nylons such as nylon-3 into films, and into their ferroelectric phase. Here, we report solution-processed ferroelectric capacitors fabricated from linear chain nylon-3 with excellent dielectric performance and demonstrate a giant remanent polarization of 16.1 ± 0.5 μC cm−2, which is the record high remanent polarization reported for ferroelectric polymers and is comparable to values that are reported for inorganic ferroelectric ceramics. Based on our analysis of ferroelectric odd nylons, we predict that nylon-1 could achieve remanent polarization values approaching 40 μC cm−2, far exceeding those reported for any ferroelectric polymer to date.

Dielectric materials with high relative permittivity, i.e., high‐k dielectrics, are in great demand for application as gate dielectric for the development of field‐effect transistors operating at low voltages. However, a high‐k gate dielectric does not always produce favorable outcomes, particularly in field‐effect transistors based on organic semiconductors (OFETs). Contradicting experimental results have been reported, with some studies showing compromised OFET performance, while others demonstrate enhanced performance when using high‐k gate dielectrics. Currently, no comprehensive or systematic study has been conducted to compare or integrate these conflicting results. As a result, the relative validity and broader implications of these conflicting findings remain uncertain. Here, the effects of high‐k gate dielectrics with systematically varied dielectric constants on OFET performance are systematically investigated and the inconsistencies in the literature are resolved. By employing a highly miscible high‐k polymer blend system, it is demonstrated that both positive and negative correlations of dielectric constant and field‐effect mobility exist in different semiconductor systems. These results provide a strategy to rationally design organic transistors that incorporate high‐k dielectrics, without compromising the field‐effect mobility due to the broadening of the density of states.

The existing device models for organic electrochemical transistors (OECTs) fail to provide any device design guidelines for optimized performance parameters such as transconductance that are pivotal for the applications OECTs in sensing. Moreover, the current models are based on the questionable assumption of a homogenous organic semiconductor layer, and all predict a linear behavior of the resistance with the OECT channel length. Consequently, the experimentally observed nonlinear resistance behavior in OECTs has been overlooked thus far. Here, an OECT device model is developed that accurately describes the nonlinear behavior of the OECT channel resistance and offers the first guidelines for maximizing transconductance. The model is inherently nonlinear and the nonlinearity stem from the non‐monolithic capacitance of the organic semiconductor layer. Moreover, the model provides a consistent and reliable estimations for the contact resistance in OECTs. The success of the model in accurately describing and providing predictions of the OECT operation by relating the device's geometrical parameters with electrochemical parameters of the semiconductor layer paves the way toward unlocking OECT potentials in diverse applications, from biosensing to neuromorphic computing and flexible electronics.