Owing to their simple chemical structures and straightforward synthesis, poly(thiophene vinylene) (PTV) derivatives are promising types of polymer donors for organic solar cells (OSCs). However, the ...structural rigidity of PTVs results in the formation of films with poor mechanical properties, which limits the application of PTVs in intrinsically stretchable (IS)‐OSCs. Here, new carboxylate‐containing PTVs are developed with tuned molecular weight (MW) (PETTCVT‐X, X = L, M, and H) and realize efficient and mechanically durable IS‐OSCs. The crystallinity of the PTVs increases progressively with increasing MW, leading to enhanced hole mobility and suppressed charge recombination of the OSCs. Moreover, both the mechanical stretchability and electrical properties of the PTVs increase significantly with increasing MW, owing to the formation of tie‐chains that connect the isolated crystalline domains. Consequently, OSCs featuring a PTV with the highest MW (PETTCVT‐H) exhibit the highest power conversion efficiency (PCE, 15.3%) and crack‐onset strain (COS, 7.1%) among the series, compared to lower values for the PETTCVT‐L (PCE = 9.7% and COS = 1.3%) and PETTCVT‐M‐based OSCs (PCE = 12.5% and COS = 3.7%). Therefore, the IS‐OSCs employing PETTCVT‐H present the highest initial PCE (10.1%) and stretchability (strain at PCE80% (retaining 80% of the initial PCE) = 16%).
A series of new carboxylate‐containing poly(thiophene vinylene)s (PETTCVT‐X, X = L, M, and H) with different molecular weights (MWs) is developed. Intrinsically stretchable organic solar cells featuring the highest MW PETTCVT‐H achieve the highest initial power conversion efficiency (PCE= 10.1%) and stretchability (strain at PCE80% = 16%) among the series.
In the last few decades, extensive academic and industrial efforts have been devoted to developing high-performance conjugated polymers (CPs) for organic electronics. Specifically, the relationships ...between the molecular structures of CPs and their properties and device characteristics have been a subject of intense studies. In this review, we highlight recent advances in the molecular design of CPs, particularly on tuning their regioregularity (RR). The RR of repeating units (
i.e.
, directional, positional, and sequential regularities) within the CP backbone determines the intrinsic properties of CPs and the performances of the resulting devices. Despite the significant impact of RR on the overall properties of the polymers and the device performances, the importance of RR in the design of CPs has yet to be emphasized. Furthermore, RR control is critical in state-of-the-art CPs with asymmetric molecular structures. This review presents a library of examples that report the impact of RR control in CPs on the properties and performances in various organic electronic devices, including simple homopolymers with asymmetric alkyl side chains and more recently developed copolymers with various donor-acceptor (D-A) combinations. This review summarizes important guidelines and provides insights for the molecular design of RR-controlled CPs and their applications in efficient organic electronics.
We summarize a variety of examples of regioregularity-controlled conjugated polymers and describe their impacts on the polymer properties and performances in polymer solar cells.
Many materials in nature change colours in response to stimuli, making them attractive for use as sensor platform. However, both natural materials and their synthetic analogues lack selectivity ...towards specific chemicals, and introducing such selectivity remains a challenge. Here we report the self-assembly of genetically engineered viruses (M13 phage) into target-specific, colourimetric biosensors. The sensors are composed of phage-bundle nanostructures and exhibit viewing-angle independent colour, similar to collagen structures in turkey skin. On exposure to various volatile organic chemicals, the structures rapidly swell and undergo distinct colour changes. Furthermore, sensors composed of phage displaying trinitrotoluene (TNT)-binding peptide motifs identified from a phage display selectively distinguish TNT down to 300 p.p.b. over similarly structured chemicals. Our tunable, colourimetric sensors can be useful for the detection of a variety of harmful toxicants and pathogens to protect human health and national security.
To treat intractable cases of autoimmune encephalitis, the need for novel immunotherapy that penetrates the blood‐brain barrier (BBB) is increasing. Tofacitinib is a Janus kinase (JAK) inhibitor used ...to treat refractory immune‐mediated diseases that effectively penetrates the BBB. Accordingly, tofacitinib could be a new option for patients with refractory autoimmune encephalitis. Patients treated with tofacitinib were selected from Seoul National University Hospital cohort for autoimmune encephalitis from April 2019 until July 2020. We retrospectively analyzed the efficacy of tofacitinib in patients with autoimmune encephalitis who showed insufficient responses to multimodal conventional immunotherapies. Tofacitinib was administered orally at a dose of 5 mg twice daily. A total of eight patients were treated with tofacitinib; two had good responses (clinical global impression‐improvement score CGI‐I = 1 or 2), three had partial responses (CGI‐I = 3), and three showed no significant improvements (CGI‐I = 4) in response to tofacitinib. The two good responders showed the improvement of chronic autoimmune meningoencephalitis and the cessation of the new‐onset refractory status epilepticus in anti‐myelin oligodendrocyte glycoprotein (MOG)–associated disorder, which was previously intractable to anesthetics and the other immunotherapies. No patients had serious side effects. Our findings suggest the potential of tofacitinib as a therapeutic option for central nervous system autoimmune diseases.
A key limitation inherent in wireless power transmission (WPT) systems using coils is a high sensitivity to the alignment between the transmitting and receiving coils. Moreover, the physical ...separation of the transmitting and receiving coils or any metallic barrier between them can notably reduce the efficiency. To overcome these limitations, a practical WPT system that is insensitive to the alignment between coils and metallic obstacles is proposed. It uses a printed circuit board-type antenna fabricated by reducing the structure of an antenna used in previous research and is designed to resonate at the target frequency through impedance matching. The proposed system uses surface-guided-mode resonance at the metal–air interface and transmits uniform power within 1.3 m. In addition, the proposed system satisfies the electromagnetic field international standard that is the electric field and magnetic field reference values are 152.5 V/m and 0.4 A/m, respectively at 4 MHz.
The acquisition of physiological data are essential to efficiently predict and treat cardiac patients before a heart attack occurs and effectively expedite motor recovery after a stroke. This goal ...can be achieved by using wearable wireless sensor network platforms for real-time healthcare monitoring. In this paper, we present a wireless physiological signal acquisition device and a smartphone-based software platform for real-time data processing and monitor and cloud server access for everyday ECG/EMG signal monitoring. The device is implemented in a compact size (diameter: 30 mm, thickness: 4.5 mm) where the biopotential is measured and wirelessly transmitted to a smartphone or a laptop for real-time monitoring, data recording and analysis. Adaptive digital filtering is applied to eliminate any interference noise that can occur during a regular at-home environment, while minimizing the data process time. The accuracy of ECG and EMG signal coverage is assessed using Bland-Altman analysis by comparing with a reference physiological signal acquisition instrument (RHS2116 Stim/Recording System, Intan). Signal coverage of R-R peak intervals showed almost identical outcome between this proposed work and the RHS2116, showing a mean difference in heart rate of 0.15 ± 4.65 bpm and a Wilcoxon's
value of 0.133. A 24 h continuous recording session of ECG and EMG is conducted to demonstrate the robustness and stability of the device based on extended time wearability on a daily routine.
A smart grid is a next-generation intelligent power grid that can maximize energy efficiency by monitoring power information in real time and by controlling the flow of power by introducing IT ...communication technology to the existing power grid. In order to apply a wireless communication network to a smart grid, it is necessary to be able to efficiently process large amounts of power-related data while enabling a high level of reliability and quality of service (QoS) support. In addition, international standards-based design is essential considering compatibility and scalability. The IEEE 802.15.4 standard is considered to be the most powerful communication method for processing data through the smart grid AMI. To reduce the energy consumption, as the duty cycle of the superframe increases, the probability of the congestion increases. However, this binary exponential algorithm in IEEE 802.15.4 standard does not account for the application of traffic characteristics that essentially negatively affect the smart grid network performances in terms of packet delivery ratio and time delay. Therefore, in this paper, we propose a new transmission scheme to reduce performance degradation by excessive collisions in the content access period (CAP), when data transmission is performed in IEEE 802.15.4 applied to smart grids. In addition, we investigated the main research topics required when applying wireless networking technology to smart grids and suggested improvement measures. Simulation results showed that the proposed scheme increased the data delivery rate and reduced the latency, and it was confirmed that reliability was improved.
Abstract
This study investigates and proposes innovative approaches to achieve frequency selectivity within a limited space. Traditional multiresonant acoustic devices use individual sensing elements ...of varying sizes to achieve resonance frequency (
f
r
), leading to an inability to sense focused acoustic waves, unlike the human ear. A miniaturized, self‐powered artificial basilar membrane that incorporates multiresonant features is introduced. Multiple
f
r
of the diaphragms are developed using inner boundary conditions (iBCs) defined by an adjustable micropatterned elastomeric support (µ‐support) and a porous nanofiber (NF) mat. This new approach offers the advantage of all‐in‐one fabrication, eliminating the need for device area variation or an additional rigid frame typically required in conventional multiresonant acoustic devices. The efficacy of the iBCs in shifting
f
r
within the vocal frequency ranges is verified via a laser Doppler vibrometer, simulation, and triboelectric output. With its self‐powering capabilities based on triboelectric principles, this artificial basilar membrane holds promise for accurately recognizing musical and vocal signals with specific frequency characteristics. With four different iBCs in a total device area of 23 × 23 mm
2
, a tunable four‐channel system with
f
r
ranging from 400 to 3000 Hz is achieved. This advancement enables the sensing of focused acoustic waves, simulating the functionality of an artificial human ear model.
A novel and simple nonlinear logical torque-sharing function (TSF) for a switched reluctance motor (SRM) drive is proposed. This novel scheme using nonlinear TSF manipulates currents in two adjacent ...phases during commutation, so that efficiency and torque ripple in an SRM drive can be considerably improved. For constant torque generation, the switching of one-phase windings is regulated, and torque reference for the other phase stays at the previous state under the condition of a certain current limit given by the overall drive power rating. Every torque state monitored by the nonlinear logical condition determines a regulated or nonregulated torque control among two phases overlapped in commutation region, where one phase is incoming to produce the majority of torque and the outgoing current in the other phase is decreasingly controlled by the logical condition. Due to the same switching state in a nonregulated phase and the reduction of commutation period by the proposed control method, the switching number can be significantly reduced, and hence, the switching loss can be reduced. In case that one-phase regulation cannot satisfy a proper torque reference required for minimum torque ripple operation, a two-phase regulation mode is employed in the novel nonlinear TSF. In order to include magnetic nonlinearity in torque control and decrease a current tail at the end of commutation, the current of the incoming phase needs to be controlled in an increasing manner, and at the same time, the outgoing phase current tracks on an opposite direction so that torque sharing between two phases can be smoothly achieved with a minimum current crossover. The proposed control scheme is verified by some computer simulations and experimental results.
Most previous studies have been focused on the variation of tea chemical composition by fermentative processes as well as different cultivars and regions. The detailed changes of flavonoid profiles ...were described for the first time by each processing step of green and black tea leaves in this study. A total of 24 flavonoid derivatives including catechins, theaflavins, and flavonols were separated and identified from the tea samples based on UPLC-DAD-QToF/MS data and constructed library. Among these, the fragmentation pathway of theaflavins was proposed specifically in positive ionization mode for structural interpretation. During leaf processing, the individual flavonols were changed as diverse patterns according to their aglycone types and glycosylated forms, but their total content showed a slight difference. EGCG and ECG were increased after roasting approximately twofold higher than that of fresh leaves (EGCG, 2709.5 →6085.6; ECG, 1548.0 →2318.2 mg/100 g dry weight, respectively) in green tea while considerably decreased their contents due to oxidation and conversion to theaflavins after fermentation during black tea processing. Especially, the drying steps also found to be factor to influence positively to increase the flavonoid contents in both tea processing. Therefore, this result indicated that detailed conditions of each processing step played important roles in changing the flavonoid profiles from tea leaves.
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