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Hybrid organic–inorganic perovskite (HOIP) materials have attracted significant attention in photovoltaics, light emission, photodetection, etc. Based on the prototype metal halide perovskite crystal, there is a huge space for tuning the composition and crystal structure of this material, which would provide great potential to render multiple physical properties beyond the ongoing emphasis on the optoelectronic property. Recently, the two-dimensional (2D) HOIPs have emerged as a potential candidate for a new class of ferroelectrics with high Curie temperature and spontaneous polarization. Room-temperature solution-processability further makes HOIP a promising alternative to traditional oxide ferroelectrics such as BaTiO3 and PbTiO3. In this perspective, we focus on the molecular aspects of 2D HOIPs, their correlation with macroscopic properties, as well as the material design rules assisted by advanced simulation tools (e.g., machine learning and atomistic modeling techniques). The perspective provides a comprehensive discussion on the structural origin of ferroelectricity, current progress in the design of new materials, and potential opportunities and challenges with emerging materials. We expect that this perspective will provide inspiration for innovation in 2D HOIP ferroelectrics. [ABSTRACT FROM AUTHOR]

The roles of various plasma agents in the inactivation of bacteria have recently been investigated. However, up to now, the effect of the charged particles on the inactivation of bacteria is not well understood. In this paper, an atmospheric pressure plasma jet device, which generates a cold plasma plume carrying a peak current of 300 mA, is used to investigate the role of the charged particles in the inactivation process. It is found that the charged particles play a minor role in the inactivation process when He/N2(3%) is used as working gas. On the other hand, when He/O2(3%) is used, the charged particles are expected to play an important role in the inactivation of bacteria. Further analysis shows that the negative ions O2- might be the charged particles that are playing the role. Besides, it is found that the active species, including O, O3, and metastable state O2*, can play a crucial role in the inactivation of the bacteria. However, the excited He*, N2 C 3Πu, and N2+ B 2Σu+ have no significant direct effect on the inactivation of bacteria. It is also concluded that heat and UV play no or minor role in the inactivation process. [ABSTRACT FROM AUTHOR]

A phosphorescent dye, tris(1-phenylisoquinoline) iridium (III) [Ir(piq)3] doped interface of 4,4′,4″-tris(carbazol-9-yl)-triphenylamine (TCTA) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) has been studied in organic light emitting diodes. Two devices with different emissive interfaces, TCTA+6% Ir(piq)3/BCP and TCTA+6% Ir(piq)3/BCP+1% Ir(piq)3, exhibited nearly the same red Ir(piq)3 emissions and I–V characteristics. However, the second device showed higher efficiency and luminance than the first device over the whole voltage range. The maximum efficiency of 6.0 cd/A reached at 0.026 mA/cm2 in the second device was 30% higher than that of 4.6 cd/A reached at 0.032 mA/cm2 in the first device. The improved performance of the second device is attributed to the fact that the excitons can be formed on both sides of the TCTA/BCP interface and can be more efficiently collected with the additional 1% Ir(piq)3 doped in the BCP layer. Therefore, the exciton-collecting structure, doping phosphorescent dyes into both sides of the TCTA/BCP interface, is believed to be a very useful way to optimize the performance of phosphorescent organic light emitting diodes. [ABSTRACT FROM AUTHOR]

Charge transfer and accumulation at semiconductor devices can lead to device degradation. Understanding and controlling such a process is therefore important. Second harmonic generation has been shown to be a sensitive probe of charging of semiconductor interfaces, with the added advantages of high spatial and temporal resolution. We have investigated the use of self assembled monolayers (SAMs) as a means to control charging. Our results suggest that octadecylsiloxane SAMs, bound to the native oxide, significantly reduce charge accumulation at oxide interfaces. [ABSTRACT FROM AUTHOR]

We propose herein to make use of rotating electric fields for achieving flexible control on the hydrodynamic behavior of two miscible co-flowing water solutions in straight microchannels, in the context of a new manipulation tool for stratified liquid contents of microfluidic systems. Our theoretical analysis indicates that, while fluids of distinct electrical conductivities and identical permittivity are parallel pumped into the mainchannel, a circularly traveling field, as emitted from a four-phase electrode array surrounding the channel sidewalls, can direct the deflection of diffusing phase interface between the side-by-side miscible electrolyte streams asynchronously at half of the interfacial relaxation frequency, where the co-field electrorotational torque becomes most appreciable. An immediate application of the out-of-phase electroconvective streaming is that time required for electrolyte mixing is reduced because the area of two-phase contact interface is dramatically enlarged, and a serial combination of several rotating electrode arrays of alternate propagating directions can further rectify the mixing of microfluidics by inducing chaotic advection. [ABSTRACT FROM AUTHOR]

Based on the continuum mechanics theory, we propose herein a universal design of microfluidic ionic diode based on external concentration polarization of a gating ion-selective medium embedded in the microfluidic network with four power terminals. This micro/nanofluidic hybrid chip employs a cationexchange nanoporous membrane (CEM) coupled with both a control and output microfluidic channel. Under the action of a vertical electric field throughout the CEM, nanoscale surface conduction of excessive counterions within the charged nanopores is converted to the propagation of either enriched or depleted boundary toward the opposing electrode-terminal in phase with the electroconvective flow, thereby making an adjustment in the electrical conductance of output microchannel for achieving highflux field-effect current control and diode functionality. Three basicworking states, including the "on," "transition," and "off" statuses, are distinguished in different ranges of source voltage magnitude. The rectification factor of the proposed ionic circuit platform can attain one hundred-fold even at small source and gate voltages. The presented field-effect-tunable microfluidic ion diode is easily scalable, permits appreciable fluid flowdue to an intrinsically small hydrodynamic resistance, and holds promise for producing high-flux ion current rectification in next-generation integrated circuits. [ABSTRACT FROM AUTHOR]

We optimized the diameter and microgeometry of preformed conductive filaments (CFs) to improve the switching reliability of copper/nanoporous amorphous carbon (a-C)/platinum memory devices. Forming-free devices were obtained because of the introduction of preformed CFs into the nanoporous layer during the copper electrode evaporation process. The switching fluctuation decreased with the increasing preformed CF size in a certain range; however, the device with stronger preformed CFs suffered from high current in the first RESET process. Furthermore, to achieve both high switching uniformity and low power consumption, a dual-layer structure was proposed to regulate the microgeometry of preformed CFs. Compared with those of a pristine device and single-layer nanoporous device, the fluctuation of high/low resistance values was further suppressed to 26% and 21%, respectively. In addition, Resistive random access memory (RRAM) devices exhibited a fast switching speed (<50 ns), excellent endurance (>105 cycles), and long retention time (>105s at 85°C). These results reveal the key role of preformed CF optimization in resistive switching performance improvement, providing an effective approach to develop high-performance RRAM devices. [ABSTRACT FROM AUTHOR]

Herein, we first describe a perfusion chip integrated with an AC electrothermal (ACET) micromixer to supply a uniform drug concentration to tumor cells. The inplane fluid microvortices for mixing were generated by six pairs of reconstructed novel ACET asymmetric electrodes. To enhance the mixing efficiency, the novel ACET electrodes with rotating angles of 0°, 30°, and 60° were investigated. The asymmetric electrodes with a rotating angle of 60° exhibited the highest mixing efficiency by both simulated and experimental results. The length of the mixing area is 7 mm, and the mixing efficiency is 89.12% (approximate complete mixing) at a voltage of 3V and a frequency of 500 kHz. The applicability of our micromixer with electrodes rotating at 60° was demonstrated by the drug (tamoxifen) test of human breast cancer cells (MCF-7) for five days, which implies that our ACET inplane microvortices micromixer has great potential for the application of drug induced rapid death of tumor cells and mixing of biomaterials in organs-on-a-chip systems. [ABSTRACT FROM AUTHOR]

We describe a novel rotating trait of induced-charge electroosmotic slip above a planar metal surface, a phenomenon termed "Rotating induced-charge electro-osmosis" (ROT-ICEO), in the context of a new microfluidic technology for tunable particle rotation or rotational trap. ROT-ICEO has a dynamic flow stagnation line (FSL) that rotates synchronously with a background circularly polarized electric field. We reveal that the rotating FSL of ROT-ICEO gives rise to a net hydrodynamic torque that is responsible for rotating fluids or particles in the direction of the applied rotating electric field either synchronously or asynchronously, the magnitude of which is adjusted by a balance between rotation of FSL and amplitude of angular-direction flow component oscillating at twice the field frequency. Supported by experimental observation, our physical demonstration with ROT-ICEO proves invaluable for the design of flexible electrokinetic framework in modern microfluidic system. [ABSTRACT FROM AUTHOR]

Droplet-based microfluidics has provided a means to generate multi-core double emulsions, which are versatile platforms for microreactors in materials science, synthetic biology, and chemical engineering. To provide new opportunities for double emulsion platforms, here, we report a glass capillary microfluidic approach to first fabricate osmolarity-responsive Water-in-Oil-in-Water (W/O/W) double emulsion containing two different inner droplets/cores and to then trigger the coalescence between the encapsulated droplets precisely. To achieve this, we independently control the swelling speed and size of each droplet in the dual-core double emulsion by controlling the osmotic pressure between the inner droplets and the collection solutions. When the inner two droplets in one W/O/W double emulsion swell to the same size and reach the instability of the oil film interface between the inner droplets, core-coalescence happens and this coalescence process can be controlled precisely. This microfluidic methodology enables the generation of highly monodisperse dual-core double emulsions and the osmolarity-controlled swelling behavior provides new stimuli to trigger the coalescence between the encapsulated droplets. Such swelling-caused core-coalescence behavior in dual-core double emulsion establishes a novel microreactor for nanoliter-scale reactions, which can protect reaction materials and products from being contaminated or released. [ABSTRACT FROM AUTHOR]

By imposing a biased gate voltage to a center metal strip, arbitrary symmetry breaking in induced-charge electroosmotic flow occurs on the surface of this planar gate electrode, a phenomenon termed as AC-flow field effect transistor (AC-FFET). In this work, the potential of AC-FFET with a shiftable flow stagnation line to flexibly manipulate micro-nano particle samples in both a static and continuous flow condition is demonstrated via theoretical analysis and experimental validation. The effect of finite Debye length of induced double-layer and applied field frequency on the manipulating flexibility factor for static condition is investigated, which indicates AC-FFET turns out to be more effective for achieving a position-controllable concentrating of target nanoparticle samples in nanofluidics compared to the previous trial in microfluidics. Besides, a continuous microfluidics-based particle concentrator/director is developed to deal with incoming analytes in dynamic condition, which exploits a design of tandem electrode configuration to consecutively flow focus and divert incoming particle samples to a desired downstream branch channel, as prerequisite for a following biochemical analysis. Our physical demonstrations with AC-FFET prove valuable for innovative designs of flexible electrokinetic frameworks, which can be conveniently integrated with other microfluidic or nanofluidic components into a complete lab-on-chip diagnostic platform due to a simple electrode structure. [ABSTRACT FROM AUTHOR]

A modified evaluation method for laser flash is proposed. In this method, the moment of laser-heating cutoff time is considered as zero point. The penetration depth and formula equation of the sample temperature distribution are obtained with the approximate analytical solution before time zero (during laser heating) for the physical model of a continuously heated half-infinite, well-distributed sample. The weighted-average and approximate-equation methods are then used to quantitatively determine the laser effect depth, which leads to the formulation of a modified evaluation method in flash thermal diffusivity measurement. Results of the simulation calculations and experiments confirm the correctness of the modified method, which remarkably increases flash method applications. The modified method is applicable only to cases in which δ(x) does not exceed the sample thickness (√12α τ0 ≤ L) during laser heating. [ABSTRACT FROM AUTHOR]

A data correction method that can reduce finite pulse time effects in the flash method is presented in this article. Based on the physical model of the classical flash method, the present method uses the cutoff time moment of laser heating as zero point. This article investigated the case of constant heat flux heating by using the theoretical method and obtained a new calculation formula. The formula was tested in the case where half temperature rise time is less than the pulse time (i.e., τ0/t0.5 > 1), and the result was satisfactory. Theoretically, this method can correct the effect of any finite pulse time and significantly expand the scope of application of the flash method. [ABSTRACT FROM AUTHOR]

Incremental increase in dimethyl sulfoxide (or dimethyl formamide) in ortho-dichlorobenzene solution of poly[N-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) gradually reduces the polymer-solvent interaction, the attraction forces between polymer chains become more dominant, and the polymer chains adopt a tight and contracted conformation with more interchain interactions, resulting in a progressive aggregation in both solutions and films. This was used to fine tune the morphology of PCDTBT/PC71BM based solar cells, leading to improved domain structure and hole mobility in the active layer, and significantly improved photovoltaic performance. The power conversion efficiency increased from 6.0% to 7.1% on devices with an active area of 1.0 cm2. [ABSTRACT FROM AUTHOR]

We demonstrate a simple approach to generate phase segregation between colloidal PbS nanocrystals (NCs) and organic [6,6]-phenyl C61 butyric acid methyl ester (PC61BM). Continuous vertical phase segregation is observed in cross-linked composite films of NCs and PC61BM. Hybrid bulk heterojunction photovoltaic cells fabricated with the phase segreated composite layer have achieved the state-of-art power conversion efficiency of 3.7% under one sun of simulated Air Mass 1.5 Global solar irradiation. The presented method can be generally applied in other NC/organic systems for the development of hybrid heterojunction photovoltaic cells. [ABSTRACT FROM AUTHOR]

We combined experimental and computational approaches to tune the thickness of the films in poly(N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT)-based organic solar cells to maximize the solar absorption by the active layer. High power-conversion efficiencies of 5.2% and 5.7% were obtained on PCDTBT-based solar cells when using [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) and [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) as the electron acceptor, respectively. The cells are designed to have an active area of 1.0 cm2, which is among the largest organic solar cells in the literature, while maintaining a low series resistance of 5 Ω cm2. [ABSTRACT FROM AUTHOR]

A white organic light-emitting diode with the structure of ITO/NPB 30 nm/TCTA+2% TPP 20 nm/BCP+0.4% Ir(piq)320 nm/Alq3 40 nm/Mg:Ag was fabricated and characterized, where 2,5,7,10-tetra-phenylpyrene and tris(1-phenylisoquinoline) iridium (III) [Ir(piq)3] were used as a blue fluorescent dye and a red phosphorescent dye respectively. The I–V characteristics of the device showed a turn-on voltage of 2.6 V. The electroluminescent spectra of the device consisted of blue fluorescent and red phosphorescent emissions. The intensity of the blue emission increased gradually relative to the red emission with increasing voltage. The emissions of the device were in the white-light region between 10 and 15 V. A maximum white light luminance of 1076 cd/m2 with CIE coordinates of (x, y=0.27, 0.24) was reached at 15 V with an efficiency of 1.35 cd/A. The white light emission is related to the simultaneous exciton formation on both sides of the TCTA/BCP interface. [ABSTRACT FROM AUTHOR]