Crosslinked PEDOT:PSS Organic Electrochemical Transistors On Interdigitated Electrodes With Improved Stability

The influence of gate voltage in the off state (Vg,off) on the stability of the transfer curve of an organic electrochemical transistor (OECT) based on interdigitated electrodes (IDEs) is studied in this work. When a high Vg,off such as +0.5 V is used, a larger amount of Na+ ion injection is promoted as compared to lower Vg,off, and a noticeable decay of drain current is observed in the transfer characteristics of the OECTs upon consecutive measurements. After the crosslinking of PEDOT:PSS, the decay of drain current can be significantly reduced, indicating the improved stability of transfer characteristics in the crosslinked OECTs. The mitigation effect after the crosslinking of PEDOT:PSS on the decay of drain current is also observed in the pulsed gate bias stress experiment, which allows the usage of a higher pulse gate voltage in the off state. The decay of drain current is likely attributed to the repetitive injection–extraction of cations (i.e., Na+) under cycling gate bias

Speed-loop bandwidth design method for controller parameters of ship hydrogen storage DC electric propulsion system

ObjectivesThis paper aims to study the problems that the external electrical characteristics of a hydrogen fuel cell are soft, its dynamic characteristics are poor and its system stability is susceptible to the influence of propulsion load in marine hydrogen storage DC electric propulsion systems. MethodsFirst, an analysis is performed of the output external electrical characteristics of the hydrogen fuel cell and the propeller load conditions of the marine electric propulsion system, then a ship-engine-propeller model and a frequency-domain model of drive control system for a permanent magnet synchronous motor (PMSM) are set up. Next, a speed-loop bandwidth design method is proposed, considering the external electrical characteristics of hydrogen fuel cell and propeller load conditions. Finally, on basis of the parameters of a mother ship, an electric propulsion system for a hydrogen-battery DC electric propulsion ship in a hardware-in-loop experimental platform is established to verify the proposed method.ResultsThe experimental results show that the speed response of the motor has no overshoot under this method, and the speed-loop fluctuation is reduced by 5 r/min when the load torque disturbance occurs. ConclusionsThe speed-loop bandwidth design method proposed in this paper improves the comprehensive characteristics of the ship hydrogen storage DC electric propulsion system, and is easy to implement in engineering

Organic Electrochemical Transistor with Molecularly Imprinted Polymer-Modified Gate for the Real-Time Selective Detection of Dopamine

Because of their low operation voltage, high transconductance, and good aqueous compatibility, organic electrochemical transistors (OECTs) have been widely applied in the sensing of small redox-active molecules such as dopamine. However, selective detection of dopamine (DA) can be challenging since its sensing mechanism relies on the gate voltage offset caused by the redox chemistry at the gate electrode. To introduce selectivity toward dopamine detection, a polypyrrole film was electrochemically deposited on the Pt gate electrode with the presence of dopamine as a template and then overoxidized in an alkaline solution. The resultant OECT sensor with an overoxidized MIP (o-MIP/Pt) gate shows a similar detection limit of ∼34 nM as compared to the device with a bare Pt gate. At the same time, when compared to the drain current response of a representative interferent, ascorbate (AA), a good selectivity of DA/AA signal ratio of larger than 5 can be achieved in the concentration range between ∼0.4 and ∼10 μM, whereas OECT sensor with bare Pt gate shows little selectivity toward DA. The selectivity of the OECT sensor toward DA can be maintained in the copresence of 1-fold DA (∼0.4 μM) and 10-fold AA (∼4 μM), regardless of the order of the additions

Nucleic acid visualization assay for Middle East Respiratory Syndrome Coronavirus (MERS-CoV) by targeting the UpE and N gene.

Since its first emergence in 2012, cases of infection with Middle East respiratory syndrome coronavirus (MERS-CoV) have continued to occur. At the end of January 2020, 2519 laboratory confirmed cases with a case-fatality rate of 34.3% have been reported. Approximately 84% of human cases have been reported in the tropical region of Saudi Arabia. The emergence of MERS-CoV has highlighted need for a rapid and accurate assay to triage patients with a suspected infection in a timely manner because of the lack of an approved vaccine or an effective treatment for MERS-CoV to prevent and control potential outbreaks. In this study, we present two rapid and visual nucleic acid assays that target the MERS-CoV UpE and N genes as a panel that combines reverse transcription recombinase polymerase amplification with a closed vertical flow visualization strip (RT-RPA-VF). This test panel was designed to improve the diagnostic accuracy through dual-target screening after referencing laboratory testing guidance for MERS-CoV. The limit of detection was 1.2×101 copies/μl viral RNA for the UpE assay and 1.2 copies/μl viral RNA for the N assay, with almost consistent with the sensitivity of the RT-qPCR assays. The two assays exhibited no cross-reactivity with multiple CoVs, including the bat severe acute respiratory syndrome related coronavirus (SARSr-CoV), the bat coronavirus HKU4, and the human coronaviruses 229E, OC43, HKU1 and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Furthermore, the panel does not require sophisticated equipment and provides rapid detection within 30 min. This panel displays good sensitivity and specificity and may be useful to rapidly detect MERS-CoV early during an outbreak and for disease surveillance